TF10:Thin Films for Electronics and Optics

Posters

TF10.1.PTHE STRUCTURE AND CERTAIN PROPERTIES OF Pb(Ti,Zr)O3

THIN FILMSA.F. Andreeva, A.M. Kasumov, S.V.   Utkin

The Institute for Problems of Materials Science of the National Academy of SciencesKrzhyzhanovsky St. 3,. Kiev - 142, 03680, Ukraine

e-mail: andreeva@ipms.kiev.ua

Thin Pb(Ti,Zr)03 (PZT) films are perspective for the using in optical and acoustic

electronics as an infrared radiation detectors, a ferroelectrics memory elements, and so on.

Wide application of PZT films is retarded by the unperfectnesses of their obtaining

methods. The CVD methods (sol-gel, spincoat) release the reactive gases I2, Cl2 and others

that is practically incompatible with the other microelectronics processes. The laser

evaporation disturbs the PZT films stoichiometry. The HF-sputtering of PZT fouls the

condensates with a residual gases because of a small deposition rate. A sputtering of several

targets gives the irreproducible composition and properties of PZT layers. Diffusion in

oxide films of Ti, Pb and Zr has small rates and requires the high temperatures (over

1000°C). Thus a research for effective methods to obtain PZT films is the actual problem.

In this work a possibility was investigated to make PZT films through the reaction

synthesis of solid Pb-Ti-Zr solutions. The films were obtained on a polished SiO2, NaCl,

and the pyroceram at 300 - 800 K. The deposition rate was 10 - 15 nm/s, the films thickness

0.05 - 0.8 mm. The MDM (metal-dielectric-metal) structures were obtained with the bottom

electrode of the low-resistance SnO2 or Fe and with the In point top electrode.

The PZT films obtained at 500 K were amorphous. With growth of condensation

temperature to 600 K films crystallization was occurred in the perovskite structure. For

PZT films with the thickness 0.8 mm. on Fe underlayers the calculated value of the

dielectric constant e was of several thousands order.

The advantages of reaction synthesis method for PZT films obtaining are a low

deposition temperatures and the allowance to perform all technology in one cycle including

a modification of the composition and properties of the ferroelectric by a doping.

TF10.2.P

THE PERSPECTIVES OF THE APPLICATION OF THE RARE-EARTH METALS OXIDES THIN FILMS IN OPTICS AND

ELECTRONICSA.F. Andreeva

The Institute for Problems of Materials Science of the National Academy of SciencesKrzhyzhanovsky St. 3,. Kiev - 142, 03680, Ukraine

e-mail: andreeva@ipms.kiev.ua

The structure and properties of the rare-earth metals oxides (REMO) thin films were

investigated. The films were obtained by a reaction synthesis - an evaporation of the metal

in O2 atmosphere. It was shown that the REMO films are perspective for using as:

The masking layers with a high wear resistance and the low density of defects

(density of defects of size 1.5 mm was 0.06 cm-2) for the transparent photolithography

templates. It is possible to produce photolithography templates of planar construction due

to the phase transformations in masking layer of the praseodymium oxide. It turns out in

this case that all glass surface of substrate is covered by protecting REMO layer consisting

of transparent and non-transparent sites according to the topology. Owing to this fact occurs

the additional increase of templates wear resistance by preventing the knocking out of the

glass surface and the ability appears to use mask layers many times, saving additionally

resources and work expenses.

Optical REMO coatings have high transparency in wide spectral diapason 0.19

15 mm, refractive index is 1.92.2, light dispersion loss of laser REMO-SiO2 mirrors

< 0.005%, the threshold of the stationary radiation strength to concentrated light flux during

120 s was greater than 2.5 kW/cm2.

The REMO films are perspective for the using in capacitors and in multilevel

integrated circuits. They have high electric resistivity 1015 1016 Ohmcm, low dielectric

loss 110-4; high puncture strength 107 -108 V/cm.

The based on REMO high temperature and a heat flux sensors have the following

characteristics: the flux measured range is 108 W/cm2, the time constant is <<0.1 s, the

temperature coefficient of electric resistance at 200C is 0.06 - 0.08 0C-1.

TF10.3.P

SILICON OXYNITRIDE FOR SILICON INTEGRATED OPTICS

O.P.Agnihotri 1* , Hee Chul Lee1, B.S.Sahu2, and Pankaj Srivastava2

1 Department of Electrical Engineering and Computer Science, Korea Advanced Institute of

Science and Technology, Daejeon, Republic of Korea2 Semiconductor Engineering Laboratory, I. I. T., New Delhi, India

Growth of low refractive index (~1.5) and hydrogen free silicon oxynitride by a low

temperature deposition process could play a significant role in the fabrication of integrated

optical components on silicon substrates. We have used a photosensitized chemical vapor

deposition process to grow silicon oxynitride at a substrate temperature 0f 350°C which

could be used for the fabrication of low loss optical waveguide on silicon substrates. We

used a gaseous mixture of SiH4 (2% in Ar),NH3 and N2O under 253.7 nm UV radiation.

The oxynitride composition was varied by changing N2O:(N2O+NH3) ratio while keeping

N2O+NH3 and SiH4 flow rates constant. The refractive index could be tailored from 1.46 to

1.95. The optical energy gap increases from 4.8 eV to 5.7 eV as the flow rate ratio varies

from 0 to 0.25. At the flow rate ratio of 0.25,the resistivity of silicon oxynitride was

3.5x1014 ohm-cm and the refractive index was 1.51. The midgap interface state density of

silicon oxynitride/Si MIS devices was 8.5x1010 cm-2 eV-1. The infrared absorption showed

no evidence of Si-H and N-H bonds. The oxynitride grown in this work could therefore be

used as a low loss optical waveguide material for silicon integrated optics [1,2].

1. K.Wörhoff, A.Driessen, P.V.Lamback, L.T.H.Hielderink, P.W.C.Linders and

Th.J.A.Popma: Sensors and Actuars 74 (1999) 9.

2. O.P.Agnihotri, S.C.Jain, J.Poortmans, J.Szlufcik, G.Beaucarne, J.Nijs and R.Mertens:

Semicond.Sci. Technol. 15 (2000) R29.

* opa@ee.kaist.ac.kr

TF10.4.P

DIELECTRIC CHARACTERISTICS OF RF-MAGNETRON SPUTTERED YTTRIUM OXIDE THIN FILMS DEPOSITED ON

PLASMA-ETCHED SILICON SUBSTRATES

J.J. Araiza 1 , M. Aguilar-Frutis2, C. Falcony3,*

1Unidad Académica de Física, U.A.Z.. Av. Preparatoria # 301, C.P. 98060, Zacatecas, México.

2CICATA-IPN, Miguel Hidalgo 11500, México, DF México, 3CINVESTAV-IPN, Apdo. Postal 14-740, 07000, México, DF México

High quality yttrium oxide thin films were deposited on Si(100) substrates by rf-magnetron sputtering. The films were deposited at low temperatures; from room temperature, and up to 300º C. The characteristics of the films were studied as a function of the different etching times of the silicon substrates. Films free from –OH or water related bonds are obtained with high refractive indexes, depending on the experimental conditions. X-ray diffraction measurements of the films show that they are mainly polycristalline, presenting the cubic and/or the monoclinic phases of the yttrium oxide. The incorporation of these films into Metal-Oxide-Semiconductor structures show that they can stand electric fields close to 5 MV/cm, and with dielectric constants higher than 11. The surface state density of the MOS structures, determined at midgap of the semiconductor, was in the range of 1011 cm-2eV-1. Atomic force microscopy and energy dispersive spectroscopy measurements are also presented.The financial support by CONACyT-Mexico, under grant: G37858-E is acknowledged

____________________

*Corresponding author: C. FalconyTel. (+) 52 55 5747 3703 Fax (+) 52 55 5747 7096e-mail address: cfalcony@fis.cinvestav.mx

TF10.5.P

OPTICAL, STRUCTURAL AND ELECTRICAL CHARACTERISTICS OF RF-MAGNETRON SPUTTERED ALUMINUM OXYNITRIDE

THIN FILMS DEPOSITED ON SILICON SUBSTRATES

J.J. Araiza 1 , M. Aguilar-Frutis2,*, C. Falcony3, M. Jergel3,4, M. Garcia2,5

1Unidad Académica de Física, U. A. Z.. Av. Preparatoria # 301, C.P. 98060, Zacatecas, México.

2CICATA-IPN, Miguel Hidalgo 11500, México, DF México, 3CINVESTAV-IPN, Apdo. Postal 14-740, 07000, México, DF México

4Institute of Physics, Slovak Academy of Sciences, Bratislava, Slovakia5IIM-UNAM, Coyoacan 04510, México, DF México

The optical, structural and electrical characteristics of rf-magnetron sputtered aluminum oxynitride thin films are reported. The films were deposited at room temperature and up to 300º C without any further thermal treatments. The characteristics of the films were studied as a function of the substrate temperature during deposition and the flow ratio of nitrogen to argon in the sputtering chamber. Films free from –OH or water related bonds were obtained with a high refractive index, depending on the experimental conditions during deposition. X-ray diffraction measurements of the films show that they are mostly amorphous. The incorporation of these films into Metal-Oxide-Semiconductor structures show that they can withstand electric fields up to 5 MV/cm, without observing destructive dielectric breakdown. The effect of a plasma etching process, carried out on the substrates previous to deposition of the films, is also discussed.The financial support by CONACyT-Mexico, under grants: J34225-U and G37858-E is

acknowledged. The partial support from CGPI-IPN grant # 20010281 is also

acknowledged.

____________________*Corresponding author: M. Aguilar-FrutisTel. (+) 52 55 5729 6000 ext. 67738Fax (+) 52 55 5557 5103e-mail address: mafrutis@yahoo.es

TF10.6.P

LASER-STIMULATED TRANSFORMATIONS IN AMORPHOUS Si/Ge AND AsxSe1-x/TeySe1-y - TYPE MULTILAYERS

Beke D.L1, Csik A.1, Kikineshi A.1,2, Langer G.1, Malyovanik M.2, Shipljak M.2

1Debrecen University, Debrecen, Hungary2Uzhgorod National University, Uzhgorod, Ukraine

Recent development of thin film technology has made it possible to fabricate high-quality multilayer structures (MLS) from different amorphous semiconductors [1,2]. Some properties of these structures are similar to the compositionally modulated superlattices with modulation periods L=5-20 nm [2], therefore the size-dependent effects in optical and electrical characteristics can be investigated and related to the initial structure, interface mixing. We have extended our investigations of laser-beam-induced interdiffusion in a-Se/As2S3 amorphous MLS to the number of AsxSe1-x/TeySe1-y-type and Si/Ge structures, which were less sensitive to the direct photo-stimulated transformations but exhibited considerable changes of optical transmission in the given spectral regions, DC- and photo-conductivity due to the thermal annealing by focused laser beam.

60-300 nm thick Si/Ge structures were prepared by ciclic magnetron sputtering, while amorphous AsxSe1-x/TeySe1-y MLS with 0.1 x 0.5, 0.1 y 0.4 and total thickness d up to 1-2 mm were fabricated by ciclic thermal evaporation of corresponding initial glasses in vacuum. All structures were deposited onto transparent sapphire or silica-glass substrata, therefore optical transmission measurements of MLS were performed mostly in the wavelegth region of absorption edge of the narrow-band component (i.e. Ge, TeySe1-y). Well-definied blue-shift of absorption edge was observed in all MLS, which depended on the modulation period and can be additionally changed by constant or pulsed laser beam illumination at 0.51, 0.53, 0.63, 0.69 mm. Thus optical transmission of the MLS for the given small-intensity read-out laser beam can be effectively changed. The effects of laser-induced enlightenment correlate well with the changes of the refractive index, reflectivity and electrical conductivity in all investigated MLS in the 100-350 K temperature range. The mechanism of the observed effects was explained in the framework of the interdiffusion model, which takes into account the laser-beam heating of the MLS.

Besides fundamental interest these results are applicable for producing certain solid-state solutions, mixtures of amorphous materials and for spatial patterning, direct writing of thin film optical elements.

1. Nesheva D., Arsova D., Levi Z. Phil.Mag. B69, 205 (1994)2. Csik A., Malyovanik M., Dorogovich J., Kikineshi A., Beke D.L., Szabo I.A., Langer G. Journ. of Optoelectronics and Advanced Materials, 3, 33 (2001)

TF10.7.P

Reflectance of thin thermal oxide layer grown on c-Si substrate - statistical evaluation

Róbert Brunner 1 , Juraj Dillinger2, Emil Pinčík1.1 Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava,

Slovakia2 Department of Physics, Slovak University of Technology, Faculty of Mechanical

Engineering, Námestie slobody 17, 812 31 Bratislava, Slovakia

We present the enhanced reflectance measurements of optical and geometrical parameters of thin films - i.e. films, the thickness of which is less than wavelength of the light. These parameters are calculated as a coefficients of best fit of the dispersion curve of the reflectance data. The enhancement is based on statistical test, which enables to estimate confidence interval of the measured parameters. Both reflectance spectroscopy and standard ellipsometry investigations were performed and the obtained results were compared. The reflectance of the samples was measured for normally incident light using fiber-optics spectrometer. Optical properties of layered structure were described by standard mathematical model, based on 2x2 overall transfer matrix formalism. Tabulated empirical values of the complex refractive index of crystalline silicon substrate were used in these calculations. Parameters of oxide layer, were evaluated in fitting process of measured reflectance spectra. Simple phenomenological model of material dispersion of thin film, based on first order polynomial expansion, was used. Subsequently, the statistical test utilizing the resampling procedure was applied to the measured data set and the confidence intervals for estimated parameters of the structure were determined. The main advantage of the real data based numerical simulation is, that none a priori information, which should regard data error distribution function, is required. The reconstruction of material parameters using reflectance data is the inverse task, which is often badly conditioned. In consequence, the possibility to estimate the errors of measurement of the structure parameters and the ability to judge the stability of the calculated results without any preliminary assumption is very useful and can be unavoidable in most cases.

Corresponding author *: Tel.; Fax.; E-mail: Give full address details of the corresponding author at the bottom

TF10.8.P

PULSED LASER DEPOSITION OF Cd1-xMnxTe THIN FILMS

A.P. Caricato, E. D’Anna, M. Fernández, G. Leggieri, A. Luches, E. Mero, M. Martino.

INFM and University of Lecce, Department of Physics, 73100 Lecce, Italy

The semimagnetic semiconductor Cd1-xMnxTe is a very interesting material due to its

various properties connected with the presence of the magnetic ion (Mn). In particular the

energy gap and the lattice constant can be tuned varying the Mn content. Moreover the

spin-exchange interaction between this ion and the conduction band electrons is responsible

of different phenomena like, for example, a giant Faraday rotation near the fundamental

absorption edge. This property is of interest in the design of fiber optic magnetic field

sensors.

Pulsed laser ablation is a well-suited technique for the deposition of thin films of such

compound materials since, unlike the evaporation processes, it preserves the stoichiometry

of the target. Cd1-xMnxTe thin films (0.6–0.7 mm) were deposited by laser ablation of targets

with different Mn content (x=0.05, 0.36, 0.43 and 0.50). Ablation was performed with a

XeCl laser (=308 nm, =30 ns) at a fluence of 6 J/cm2. Films were deposited on sapphire

substrates placed at 40 mm from the target and heated at 250 °C. Energy dispersive

spectroscopy and optical transmission measurements in the 200 – 3500 nm range were

performed on the deposited films. From these characterizations it was possible to evaluate

the band-gap energy and the composition of the films. The film stoichiometry resulted in

quite good agreement with the one of their relative targets, although the deposited samples

presented a lower Cd incorporation. Scanning electron microscopy inspection showed that

the surface morphology is good for films with low magnetic ion (Mn) concentration

(x=0.05). The surface quality of the films deteriorates with increasing Mn concentration,

due to the presence of sub-micron droplets. From photoluminescence spectroscopy only the

peak at 2.0 eV, associated to the Mn2+ 6A1(6S) 4T2(4G) transition, was detected in samples

with x 0.36.

TF10.9.P

STRUCTURAL AND PHOTOLUMINESCENT PROPERTIES OF TERBIUM AND EUROPIUM DOPED ZINC ALUMINATE FILMS

SYNTHESIZED BY PYROSOL TECHNIQUE.

M. García-Hipólito a , C. D. Hernández-Péreza, A. Corona-Ocampoa, R. Martíneza, O.

Alvarez-Fragosoa, E. Martíneza and C. Falconyb,c.a Instituto de Investigaciones en Materiales, UNAM, A.P. 70-360 Coyoacán 04510 México,

D. F. b Departamento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, México D F. 07000.

Dense ZnAl2O4 coatings have been synthesized by ultrasonic spray pyrolysis deposition

process using aluminum chloride and zinc acetate. The preparation, structural and

luminescent properties of zinc aluminate films doped with Tb3+ and Eu3+ ions are presented.

Different substrate temperatures and doping concentrations in the start spraying solution

were studied. The elemental composition was measured by Energy Dispersive

Spectroscopy (EDS). X-ray diffraction analyses demonstrated that the films were single-

phase cubic corresponding to spinel. The excitation and emission spectra of Tb3+ and Eu3+

ions were measured. Concentration quenching of the photoluminescence was observed. In

addition, the surface morphology of the films was investigated.

This contribution will be presented by: Manuel García-Hipólito..

TF10.10.P

ELECTRICAL CONDUCTIVITY AND DYNAMICS OF ELECTRO-FORMING IN Al-SiOx-Al THIN FILM SANDWICH STRUCTURES

R.D. Gould and M.G. LopezThin Films Laboratory, Department of Physics, School of Chemistry and Physics,

Keele University, Keele, Staffs. ST5 5BG, U.K.

Many insulating thin film materials, including silicon oxide (SiOx), exhibit a high-field electrical conduction process on the application of relatively low voltages. The dominant high-field conduction process in SiOx appears to be the Poole-Frenkel effect, in which the high field leads to a lowering of the potential barrier between donor-like centres and the bottom of the conduction band. Such behaviour is usually indicated by a linear dependence of log J on V1/2, where J is the current density and V is the applied voltage. Since this type of process is bulk limited, it normally occurs irrespective of the type of metal contacts.

Identical structures frequently show an effect known as electroforming, in which following the application of several volts under moderate vacuum conditions, the conductance increases by several orders of magnitude and shows other characteristic features such as voltage-controlled differential negative resistance (VCNR) and elecron emission. In contrast with the Poole-Frenkel effect, electroforming is very sensitive to the type of electrodes used, with those having noble metals such as gold electroforming easily, while others, including aluminium, electroform with difficulty. Recent work has established that in samples having gold electrodes the value of the Poole-Frenkel field-lowering coefficient generally increases with the number of DC voltage cycles reqiired before electroforming, frequently attaining a value of up to twice the theoretical value. The enhanced values were associated with the establishment of non-uniform electric field region during voltage cycling, which was considered a necessary condition for the onset of electroforming.

In the present work aluminium electrodes were used in order to explore the characteristics of a contrasting system. Electroforming occurred in some samples, but with a maximum current value of less than 1 mA, considerably lower than with gold electrodes. Poole-Frenkel conductivity was observed in the initial voltage cycles, with a value of typically 4.5 10-5 eV m1/2 V-1/2, moderately exceeding the theoretical value. Electroforming normally took place after several voltage cycles, but was not permanent, with a reversion to Poole-Frenkel conduction during some cycles. As for the case with gold electrodes, the value of increased in the first few cycles, but after further voltage cycling the behaviour became less stable with varying values of . This behaviour can be understood in terms of a filamentary conduction model where the stability of samples with aluminium electrodes is inferior to those with gold electrodes as a consequence of the lower melting point. Corresponding author R.D. Gould. Telephone 00-44-(0)1782 5833316; Fax 00-44-(0)1782 712378; E-mail R.D. Gould@keele.ac.uk. Address: Department of Physics, School of Chemistry and Physics, Keele University, Keele, Staffs. ST5 5BG, U.K.

TF10.11.P

MONTE CARLO SIMULATION OF CURRENT-VOLTAGE CHARACTERISTICS IN METAL-INSULATOR-METAL THIN FILM

STRUCTURES

S. Gravano1, E. Amr2, R.D. Gould1 and M. Abu Samra2

1Department of Physics, School of Chemistry and Physics, Keele University, Keele, Staffs. ST5 5BG, UK.

2Department of Physics, College of Science and Technology, Al Quds University,Abu Deis, PO Box 20002, Jerusalem, West Bank.

Many metal-insulator-metal (MIM) thin film sandwich structures exhibit an electroforming process, after which the resulting DC current-voltage (I-V) characteristic exhibits ohmic conduction and voltage-controlled differential negative resistance (VCNR) at low and high voltages respectively.

Among several alternative models of the electroforming process and subsequent conduction the most successful appears to be the filamentary model, in which it is assumed that the electroforming process establishes a population of ohmic filaments within the insulating matrix, spanning the metal contacts. The VCNR behaviour results from the progressive cessation of conduction in individual filaments as the voltage is increased, owing to Joule heating effects. Early work showed that by assuming triangular or parabolic distributions of filament resistances, I-V characteristics typical of those obtained experimentally could be obtained. More recent simulations performed in this group considered more realistic normal distributions of filament resistances and radii, which were also demonstrated to yield characteristics in accord with experiment.

In the present work we likewise consider a model containing 5 106 filaments with normal distributions of the filament population. However, in contrast to previous work in which the I-V characteristics were derived analytically, a novel approach using a Monte Carlo method was adopted. The resulting I-V characteristics were clearly in accord with experiment, showing typical behaviour of ohmic conduction and VCNR. More importantly is that the approach adopted here lends itself to consideration of more complex distributions, and therefore to a better representation of the underlying filament population. Preliminary work has considered a multivariate distribution.

Corresponding author S. Gravano, Tel. 00-44-(0)1782-583324; Fax 00-44-(0)1782-712378; Email s.gravano@keele.ac.ukAddress: Department of Physics, School of Chemistry and Physics, Keele University, Keele, Staffs, ST5 5BG, UK.

-100

-50

0

50

100

1,30 1,35 1,40 1,45 1,50

photon energy, eV

volta

ge, m

V 1

2

3

4

х10

х10

TF10.12.P

EFFECT OF THERMAL ANNEALING ON JUNCTION LAYER FORMATION IN NbNGaAs HETEROSYSTEM

I. Hotovy, L.V. Shekhovtsov, E.F. Venger

Investigations of spectral characteristics of transverse photovoltage made it possible to determine presence and properties of a junction layer in the samples of NbNGaAs Schottky contact. In particular, for these structures at thermal annealing temperature below 800 ºC spectral characteristics obtained at voltage excitation on the GaAs side demonstrate alternating signs (curve 1). The measurements were made at the exciting light beam intensity of 81014 photon/cm2s. The low-energy portion of spectral curve, with a peak near 1.37 eV, is due to nonequilibrium charge carrier generation in a doped semiconductor layer whose formation along the metalsemiconductor interface results from NbN deposition followed with annealing of the structure studied. The form of the spectral characteristics obtained at voltage excitation on the NbN side (curve 2) is typical for

structures with a depletion layer at the interface (to which, in particular, belongs Schottky contact). Thermal annealing at a temperature over 900 ºC results in a relative decrease of junction layer conduction and, correspondingly, in a drop of contribution to the total signal from the voltage generated in this region. In this case the main contribution comes from the lateral photovoltage generated at the boundary between the GaAs bulk and depletion region of Schottky contact. The spectral characteristic is transformed into a curve that does not change its sign over the spectral range measured (curve 3). However, at photovoltage excitation on the NbN side, generation of voltage in the junction layer again manifests itself as a peak near 1.37 eV

(curve 4). Nonlinear dependence of the voltage amplitude on the exciting light beam intensity is evidence of predominantly barrier mechanism for generation of the voltage studied. Thus investigation of the features of spectral characteristics of transverse photovoltage in Schottky contact seems to be a promising technique for obtaining information on formation and properties of junction layers in semiconductor heterosystems.

L.V. Shekhovtsov. Institute of Semiconductor Physics National Academy of Sciences of Ukraine 45, prospect Nauki, 03028 Kiev, Ukraine, Fax: +(380-44)-265-83-42; E-mail: k208@photon.kiev.ua

TF10.13.P

Structural and optical properties of transparent P-type Cu-Al-O thin films prepared by DC sputtering

B.Ismail, M.Kanzar, B.RezigLaboratory of Photovoltaic & Semiconductors MaterialsPB 37 Ecole National d’Ingénieurs de Tunis Le belvédère 1002 Tunisie

Abstract : Phase formation processes in co-sputtered Cu-Al films (precursors), and the formation of CuAlO2 from these precursors were produced by sequentialeous deposition of Cu and Al in DC sputtering anto Pyrex substrates. The Cu-Al precursors were oxidized in air at various temperature. Subsequently the formation of CuAlO2 was studied after both incomplete and complete oxidization. The films were characterized by means of the X-Ray –Diffraction ( XRD), Scanning electron Microscopy (SEM) and spectrophotometer. The analysis of the XRD data was found that next to composition of precursors the oxidization temperature is a signification parameter for the formation process and the microstructure of the resulting CuAlO2 films. The optical transmission of the films show 40% to 60% transparency in most of the visible spectrum and became much more transparent in the infrared spectrum (cf fig 1). The optical band gap estimated from 2(h) plot, were found to be in the rang 3-3.5 eV depending in the fabrication parameters.

name of the person who will make the presentation: Belkacem Ismail

Corresponding author *:Belkacem Ismail Tel2161874700\562.; E-mail:kacem.ismail@webmails.com PB 37 Ecole Nationale d’Ingénieurs de Tunis Département Génie Industriel Laboratoire de Photovoltaïque & Matériaux Semiconducteurs Le belvédère 1002 Tunisie

TF10.14.P

EFFECT OF OXYGEN PARTIEL PRESSURE ON THE PROPERTIES OF TiOx THIN FILMS PREPARED BY DC SPUTTERING

B.Ismail, M.Kanzar, B.RezigLaboratory of Photovoltaic & Semiconductors MaterialsPB 37 Ecole National d’Ingénieurs de Tunis Le belvédère 1002 Tunisie

Abstract : Thin films n-type TiOx were prepared by DC magnetron reactivesputtering. The structural, optical and electrical properties have studied as a function of oxygen partiel pressure and sputtering power. We have found that the the as deposited titania film was quite transparent in visible region. The index of the refraction increases by increasing oxygen flow. We have found the variation of the optical band gap of TiOx to be less than 2% and is less indicative of chemical and/or microstructure changes than the extinction coefficient at higher energys in the visible. The resistivity is too large to mesured at heigh oxygen flows. The resistivity falls by several orders of magnetude as the oxygen flow decreases

name of the person who will make the presentation: Belkacem Ismail

Corresponding author *:Belkacem Ismail Tel2161874700\562.; E-mail:kacem.ismail@webmails.com PB 37 Ecole Nationale d’Ingénieurs de Tunis Département Génie Industriel Laboratoire de Photovoltaïque & Matériaux Semiconducteurs Le belvédère 1002 Tunisie

TF10.15.P

THIN FILM MICROELECTRODE ARRAY FOR NON-INVASIVE MONITORING OF HUMAN SKIN

1 Ivanic, R ., 1Novotny, I., 1Rehacek, V., 1Tvarozek, V., 2Weis, M.1Department of Microelectronics, Slovak University of Technology, Ilkovicova 3, 812 19

Bratislava, Slovakia2Institute of Medical Physics and Biophysics, Comenius University, Bratislava, Slovakia

Planar interdigitated array (IDA) of electrodes is a commonly used electrode configuration for conductometric sensing applications. The multilayers structure of the skin in particular epidermis, requires a special design of electrode system with slight penetration depth of the electric field. An application of the electrode systems for measurement electric parameters in dermatology has to take in consideration the relation between thickness of the skin and the distance of electrodes. If the distance of coupled electrodes is greater than the skin thickness, the vector intensity lines of the electric field are enclosed across the planar structures of the skin. In opposite, when the distance is lower then the thickness of the skin, then the lines of electric field are enclosed of circuit longitudinal to laminar skin structures. That last requirement can be fulfilled only by use of thin film technology.

Measurements and comparation of system sensitivity have been simulated for symmetric and non-symmetric electrodes with different dimensions. With decreasing of distance (gap) between IDA fingers the sensitivity is increased 100 times in comparatison with planar bulk electrodes. Simulation of electrical field by QuickField showed that vector of electrical intensity of non-symmetric IDA system is more enclosed in upper laminar skin structures with comparison to symmetric IDA systems. The density of the vector intensity lines of the electric field in non-symetric structure is 30% higher as in the case of symetric structure. Generally the 80% of electric field intensity is concentrated in the depth which corresponds to distance between electrodes.

With aspect of theoretical analysis, such as simulation of electrical properties of human skin and simulation of electrostatic field of IDA electrods, the non-symmetric Pt thin film IDA electrodes (widths of fingers are 15mm and 50mm, gap is 25mm) have been designed and fabricated.

The results of conductometric electrical measurements of both the electrochemical solutions and the human skin using thin film IDA electrodes has been in agreement with and has confirmed their applicability in non-invasive dermatology diagnostisc.

AcknowledgementThis work was supported by SK grant VEGA 7623/20

Rastislav Ivanic, +421 2 60291 731, +421 2 65423 480, ivanic@elf.stuba.sk

Ing. Rastislav Ivanic, PhD.Department of Microelectronics, STUIlkovicova 3812 19 Bratislava, Slovakia

TF10.16.P

ATOMIC MECHANISMS OF ULTRAFAST CRYSTALLIZATION PROCESS IN THIN TE ALLOYS

J. Kalb, T. Pedersen, S. Ziegler, R. Detemple, D. Wamwangi, H.-W. Wöltgens, M. Wuttig*

I. Physikalisches Institut, RWTH Aachen, D-52056 Aachen

Te alloys are successfully employed for reversible optical data storage where the laser induced switching between a crystalline and an amorphous state is employed to store information. Since crystallization of amorphous regions (bits) is the time limiting step in these storage materials, considerable effort has been spent to determine, understand and optimise the atomic mechanism of crystallization. Here we report on measurements which enable us to separate the two processes governing the kinetics of crystallization, namely nucleation and subsequent growth. For a number of different Te alloys including Ge2Sb2Te5, Ge4Sb1Te5 and AgInSbTe the kinetics of fast crystallization processes are determined on the nanosecond time scale [1-3]. This investigation reveals that two different recrystallization mechanisms are dominant in different alloys. Subsequently the activation barrier of crystallization has been determined by differential scanning calorimetry and measurements of the electrical resistance. Using viscosity measurements the activation barrier for growth could be measured, as well. This enables the separation of the contribution of nucleation and growth to crystallization. Our data show that the two different crystallization mechanisms, namely fast growth crystallization and fast nucleation crystallization are due to the difference in the activation barrier for nucleation for the different materials.

References:[1] R. Detemple, I. Friedrich, W. Njoroge, I. Thomas, V. Weidenhof, H.-W. Wöltgens, S. Ziegler, M. Wuttig Mat. Res. Soc. Symp. Proc. 674, V1.8.1 (2001)[2] W. Njoroge, M. Wuttig J. Appl. Phys. 90, 3816 (2001[3] V. Weidenhof, I. Friedrich, S. Ziegler, M. Wuttig J. Appl. Phys. 89, 3168 (2001)

Corresponding author: M. Wuttig Tel. +241-80-27155; Fax. +241-80-22331; E-mail: wuttig@physik.rwth-aachen.de

TF10.17.P

THE ELECTROMECHANICAL BEHAVIOR OF NICHROME (Ni-Cr

80-20 WT%) FILMImam H. Kazi1, Wild, P. M.1, Moore, T. N.1, Sayer, M.2

Queen’s University at Kingston

Kingston, Ontario

Canada K7L 3N6

Abstract

The application of thin film in strain gauge technology is well established and Ni-Cr [80/20

wt%] is a commonly used material for application in thin film strain gauges. Even though

Ni-Cr [80/20 wt%] is widely used in thin film strain gauges, there is not a lot of

information available about its electromechanical properties and behavior. All such

information is usually veiled behind commercial secrecy. In the present work, the

electromechanical properties and behavior of sputter deposited Ni-Cr [80/20 wt%] film on

glass substrate have been investigated experimentally for strain gauge application. The

films were coated with alumina film and then heat treated for stabilization before their

electromechanical properties were determined. The sheet resistance, gauge factor and the

temperature coefficient of resistance (TCR) have been investigated and their dependence on

film thickness has been studied. The temperature coefficient of resistance has been found

to vary with temperature as well. The results qualitatively conform to what is to be

expected from metal films. However, for the most part, there are no experimental results

available to compare with. The gauge factor is compared with previously reported results

and the differences are discussed.

TF10.18.P

DC- SPUTTERING OF THIN FILM ELECTROLYTES ON VARIOUS SUBSTRATES FOR SOFC APPLICATION

Darja Kek1, Peter Panjan1, Marijan Macek 1 ,2

1Jozef Stefan Institute, Jamova 39, 1000 Ljubljana, Slovenia2University of Ljubljana, Faculty of Electrotechnical Engineering, Trzaska 25, 1000

Ljubljana, Slovenia

The reduction of the operating temperature of the solid oxide fuel cells (SOFC) by shifting

from bulk to thin film electrolyte (stabilized ZrO2 or acceptor doped CeO2) is of prime

research interest in the field. Indeed, the possibility thereby exists to embed miniaturized

SOFC structures as a power sources together with microelectromechanical (MEMS)

components, and other active electronics into the same silicon wafer.

In this context, Y-stabilized zirconia and Gd-doped ceria have been prepared by DC-

sputtering using a metallic targets. The films have been deposited under argon/oxygen

atmospheres on various substrates (porous NiO/YSZ substrates, Al2O3 and silicon wafers)

heated between 200-700oC. The structures of YSZ and Gd-doped CeO2 with the thickness

of 0.5 mm to 10 mm have been investigated by x-ray diffraction, SEM and TEM. The films

morphology varied from columnar to polycrystalline structure depending on the oxygen

pressure and the substrate temperature. The electrical properties of some thin films (YSZ)

were investigated by impedance spectroscopy in different atmosphere and in the

temperature range between 350oC and 600oC. The activation energy and conductivity of

thin films will be reported and compared to the data obtained for bulk material.

TF10.19.P

LUMINESCENT PROPERTIES OF THE ZnS-Cu FILMELECTROLUMINESCENT DEVICES FABRICATED BY DIFFERENT

METHODS

V.S.Khomchenko, V.E.Rodionov

Institute of Semiconductor Physics, National Academy of Science of Ukraine,

45, Prospect Nauky, 03028, Kiev, Ukraine.

ZnS-Cu thin films are of interest of use for various optoelectronics devices as green

and blue emitting layers. The cooper has peculiarity as activator in comparison with other

metals (for example, Mn, Tb). High annealing temperature is need for the appearance of the

ZnS-Cu films luminance. A special method must be use for the luminescent ZnS-Cu films

fabrication.

The ZnS-Cu films were prepared by different physical and chemical methods. For

EL characterization the two types of El devices used on the glass and ceramic substrate. The

thin film EL (TFEL) device on glass substrate has a conventional double (or single) insulating

structure. In another inverse TFEL structure, the metal back electrode and BaTiO3 (~ 40 mm

thick) insulator sheet were formed on ceramic substrate by special technology.

The excitation and emission mechanisms of Cu electroluminescence (EL) are

studied in different type ZnS-Cu layers by means of EL spectrum investigation, voltage and

frequency dependence of the brightness, brightness wave investigation and the influence of

probing pulses on brightness waves amplitudes and shapes. It is shown that the EL

excitation occurs through the impact-excitation mechanism. The mechanism emission is an

underlayed recombination.The EL degradation character is similar to that observed for

emission centers with intraionic emission mechanism. The behavior peculiarities of the Cu

in the ZnS lattice are discussing taking into consideration the amphoteric character Cu as an

impurity in the ZnS.

TF10.20.P

Optical properties of electrodeposited CdIn2Te4 thin filmsKiran Jain, K.N.Sood, Sandeep Kohli, and A.C.Rastogi

Materials Division, National Physical Laboratory Dr. K. S. Krishanan Marg New Delhi 110 012

The ternary (CdTe)1-x(In2Te3)x is of interest because all alloys formed by mixing CdTe and In2Te3 are semiconductors. These ternary alloys have been regarded as potential electro-optical and photovoltaic materials. Few experimental studies on the growth of Cadmium indium telluride films have been reported and no attempt was made so far to deposit them by electrochemical technique. The knowledge of the optical properties of cadmium indium telluride thin films near and above the absorption edge is important for photovoltaic applications.

In the present work a novel electrochemical deposition technique is used to deposit CdIn2Te4 films, in which a single parameter, deposition potential is capable of varying the optical band gap of the film by varying cation concentration in the deposit. Co-deposition of Cd, In and Te from a single bath was found to yield ternary Cd-In-Te semiconductor films. These films have been deposited over tin oxide coated glass substrate from an aqueous solution containing CdSO4, InCl3 and TeO2. Cathodic deposition potential was varied from –0.45 V to –0.68 V (SCE) and temperature (80 °C ) was kept constant. It was found that the Cd, In and Te concentration in the film can be controlled by varying the cathode potential, and correlated to observed optical properties, absorption co-efficient and optical band gap of the films. Morphological, compositional and structural analysis were also carried out. The as deposited films showed cubic structures with c-axis perpendicular to the substrate. The band gap energies as determined from the optical transmission studies varied between 1.0 and 1.4 eV depending upon the deposition potential.

Dr.(Mrs) Kiran Jain, Scientist, Elec.Mat.Div., NPL, New Delhi E.mail: kiran@csnpl.ren.nic.in

TF10.21.P

POLYCRYSTALLINE Nd:KGW THIN FILM CREATED BY PULSED LASER DEPOSITION

J. Lančok(1), T. Kocourek(1), V. Vorlíček(1), C. Garapon(2) and M. Jelinek(1)

(1) Institute of Physics ASCR, Na Slovance 2, 182 21 Prague 8, Czech Republic

(2) Laboratoire PCML, University Claude Bernard, Lyon 1, France

Potassium gadolinium tungstate KGd1-xNdx(WO4)2 (Nd:KGW) is knowing from beginning

of 70-th. Its has a lot of interest as efficient low threshold diode pumped solid-state lasers

with interesting optical properties. Besides, KGW host has a high nonlinear susceptibility

of the third order (3), and therefore can be used as a Raman shifter. The textured and

amorphous thin films of neodymium doped potassium gadolinium tungstate, KGd1-

xNdx(WO4)2 (Nd:KGW) were deposited by KrF laser ablation on MgO, YAP and YAG

substrates at temperatures up to 800 oC in oxygen ambient atmosphere. The influence of

substrate materials and substrate temperature (Ts) on films crystallinity and morphology

were studied by conventional X-ray diffraction (XRD), microraman spectroscopy (MRS)

and scanning electron microscopy (SEM). Fluorescence and excitation spectra and lifetime

were measurement as a consequence of crystalline structure of the films. The textured films

with fluorescence spectra close to the bulk crystal were deposited at YAG substrate at

higher Ts, whereas the smoother films were obtained at Ts=400 °C at all types of substrates.

The fluorescence decay was almost exponential, with a lifetime of about 110 ms for

polycrystalline films.

Acknowledgements

The work was supported by the project LN00A015 of the Ministry of Education of the

Czech Republic. Jan Lančok would like to thank to post-doc grant GAČR GP106/01/D017.

We would like to express thanks to J. Chval for SEM photos.

TF10.22.P

Nonlinear Size Phenomena of Hot Electrons in Semiconductors Thin Films.

G.N.Logvinov, Yu.G.Gurevich, O.Yu.TitovDepartamento de Fisica, Centro de Investigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Apartado Postal 14-740, 07000 Mexico, D.F., Mexico

We suggest the theory of the size effects in semiconductors of thickness of order and less

the characteristic energy diffusion length known as the cooling length. Since these lengths

is considerably longer than the momentum mean free path and have the order

in typical semiconductors the effects discussed in this report can occur in

submicron films. A discussion is given of the principal phenomena that are responsible for

the dependence of the transport coefficients on the size of a sample. These are the energy

distribution of carriers at the boundaries in a transverse magnetic field, cooling of carriers

at the boundaries, and presence of “overheating” relaxation mechanisms. Thermal

boundary conditions are discussed in detail. Methods of calculation of the conductivity and

the non-linear current-voltage characteristics of films are given for single- and many-valued

(field) dependence of the electron temperature.

Instituto Politecnico Nacional, Seccion de Estudios de Posgrado e Investigacion, ESIME Culhuacon, Av. Santa Ana 1000, Col. San Francisco, Culhuacan, C.D.04430, D.F.,Mexico (*) Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados, Instituto Politecnico Nacional, Apartado Postal 14-740, 07000 Mexico, D.F., Mexico

TF10.23.P

STUDY ON ENERGY TRANSFERENCE BETWEEN Ce AND Mn IONS IN FILMS OF Al2O3.

R. Martínez-Martínez a , E. Martínez-Sáncheza, M. García-Hipólitoa, F. Ramos-Britoa, O. Álvarez-Fregasoa and C. Falconyb.

aInstituto de Investigaciones en Materiales, UNAM, A.P. 70-360 Coyoacán 04510 México, D.F.

bDepartamento de Física, CINVESTAV-IPN. Apdo. Postal 14-740, México, D.F. 07000.

Corresponding autor e-mail: maga@servidor.uman.mx

Al2O3: Ce:Mn thin films were grown by the Pyrosol technique. Recent experiments shown

that Al2O3: Mn films do not presents luminescent emissions. On the other hand, blue

photoluminescence emissions from Al2O3: Ce,Cl films is obtained but as some

concentration of Mn ions is added red emission appears. This red emission is characteristic

of the manganese ions. Presumably this phenomenon is due to an energy transference

process. In this work, detailed study on the energy transference between above cited ions is

performed. In addition, the influence, on the luminescent properties, of the preparation

parameters is investigated.

Presentation: Enrique Martínez Sánchez

TF10.24.P

Properties Of Silicon Oxynitride Thin Films Deposited By Electron Beam Physical Vapour Deposition Technique

*K. C. Mohite, S. T. Pawar, B. N. Pawar, S. R. Jadkar and M. G. Takwale

School of Energy Studies, University of Pune, Pune 411 007 (India)

ABSTRACT

During last two decades or more amorphous silicon oxynitride (SiOxNy), thin films have found widespread applications as a dielectric and mask material in microelectronics as well as an antireflective coating in amorophous silicon based solar cells. Furthermore, the mechanical hardness and chemical inertness of silicon oxynitride have made them a viable material for sensors.

In present study, we have deposited silicon oxynitride thin films utilising electron beam physical vapour deposition technique (EB-PVD) at low substrate temperatures onto single crystalline silicon and glass. These films were characterised by UV-Visible spectroscopy, Infra Red Spectroscopy, X-ray Photoelectron Spectroscopy and Photoluminescence Spectroscopy.

The effects of deposition time and substrate temperature on optical and compositional properties have been investigated systematically. The XPS studies reveals that the incorporation of nitrogen in the SiO2 films increases with increase in substrate temperature and deposition time. The incorporation of nitrogen is further confirmed by photoluminescence spectra. UV-Visible spectroscopic analysis shows that the band gap of SiOxNy films lies in the range of 2.98-3.11 eV. However, the ellipsometric measurements shows that values of refractive indices, n and k, are in the range of 1.51 to 1.98 and 0.03 to 0.06 respectively. With above results we firmly concluded that the EB-PVD deposited SiOxNy films have potential use in the field of a-Si: H based solar cells as an antireflective coating.

*Corresponding author: E-mail: kcm@physics.unipune.ernet.in

TF10.25.P

THE EFFECT OF THE CARRIER DIFFUSION AND RECOMBINATION IN SEMICONDUCTORS UNDER THE

TEMPERATURE FIELD ON THE PHOTOACOUSTIC SIGNAL

L. Villegas-Lelovsky, G. González de la Cruz, Yu. G. GurevichCentro de Investigación y de Estudios Avanzados del IPN, 07000 D.F. México

An analytic derivation is presented for the heat transport in bipolar semiconductors, taking

into account generation and heating of carriers on the surface due to an incident modulated

laser beam on the surface and finite carrier diffusion and recombination in the solid under

inhomogeneous temperature distribution. The temperature distribution in the limit of the

one temperature and two temperatures as function of the position and time in the

semiconductor is calculated using appropriate conditions according to the photoacoustic

experimental set up. In addition, special emphasis is made on the effect of the

inhomogeneous temperature distribution on the heat power density generated in the sample

due to the recombination of the electron-hole pair in the photoacoustic signal. In the case of

two temperatures is showed that both the carrier current density and the carrier heat flux

turn out to be depending of the electron and hole temperatures. The frequency dependence

of the amplitude and phase signal obtained from electron and phonon temperature

distributions are analyzed for characteristic parameters of the problem: the thermal

generation rate of carriers concerning to difference of the temperatures involved and the

electron-phonon energy interaction. In order to do it remarkable we neglected the carrier

heating on the surface of the sample.

Corresponding author *: Phone and Fax: +52 55 57 47 38 28; E-mail: lvl@fis.cinvestav.mx Physics Department, CINVESTAV-IPN, Apartado Postal 14-740, 07000, Mexico DF, Mexico

TF10.26.P

ANNEALING DEPENDENCE OF OPTICAL PROPERTIES OF Ga20S75Sb5 AND Ga20S40Sb40 THIN FILMS

Osman M.A. [1], Othman A.A.[2], Amer H.H. [3], , Dahshan A.[4]

1,2,4 Department Of Physics, Assiut University, Assiut, Egypt.3. Solid State Physics Department, National Center For Radiation Research Abstract:

Amorphous Ga20S75Sb5 and Ga20S40Sb40 thin films were prepared onto glass substrates. The effect of annealing (in vacuum) at different temperatures on the optical parameters was investigated in the temperature range 373 K- 593 K. The optical absorption coefficient ( ) ,refractive index (n) and extinction coefficient (k) for the as –deposited and annealed films were calculated from reflectance an transmittance measurements in the range 190-900 nm . X-ray diffraction indicates that the as –deposited and annealed films up to the glass transition temperature exhibit amorphous nature. On annealing above the glass transition temperature these films have a poly crystalline structure. Analysis of the optical absorption data indicates that the optical band gap Eg of these films obeys Tauc relation for the allowed non-direct transitions. It was found that the optical band gap Eg increases with annealing temperature up to Tg, whereas above Tg this remarkable decreases .The obtained results were interpreted on the basis of amorphous –crystalline transformation.Corresponding author : e_ mail :aaelho@yahoo.com

TF10.27.P

PHOTOLUMINESCENCE PROPERTIES OF a-Si:H BASEDTHIN FILMS AND CORRESPONDING SOLAR CELLS

E. Pinčíka, H. Kobayashib, H. Gleskovác, M. Kučerad, L. Ortegae, M. Jergelf,1, C. Falconyf, R.   Brunner a,

a Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovakia

b Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan

c Department of Electrical Engineering, Princeton University, Princeton, N.J. 08544, USAd Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9,

842 39 Bratislava, Slovakia e Laboratoire de Crystallographie du CNRS, BP 166, 38042 Grenoble Cedex 09, France f Departmento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, 07300 México D.F.,

México

Amorphous hydrogenated silicon (a-Si:H) is a very known semiconductor with metastable properties. Direct surface exposure, such as occurs in rf plasma equipments, introduces damage due to the charged particle bombardment. The paper deals with luminescent properties of virgin and ion beam exposed and chemically treated (in KCN solution) surfaces of a-Si:H and corresponding solar cell structures. The cyanide treatment improves the electrical characteristics of both corresponding MOS structures and solar cells. The influence of both oxygen and argon rf plasmas was also studied.

The photoluminescence measurements were performed at liquid helium temperatures at 6 K using an Ar laser and lock-in signal recording device containing the Ge and Si photodetectors. Optically determined band-gap-related groups of defects were observed as broad luminescent peaks between 0.7–1.0 eV. Additional two peaks were detected around 1.1 eV and 1.7 eV. The evolution of a new luminescent transition at ~1.2 eV during “PL quenching” experiments is presented. The luminescent properties of a-Si:H surfaces before and after ion beam and chemical treatment procedures are compared.

Corresponding author *: Tel. 00421-2-5941 0543; Fax. 00421-2-5477 6085; E-mail: fyzirbbr@nic.savba.sk 1 On the leave from the Institute of Physics SAS, Bratislava, SlovakiaPoster presentation

TF10.28.P

ON STRUCTURAL PROPERTIESOF Si/Zr(Y)O2 and Zr(Y)O2/Si SYSTEMS

E. Pinčík a, , M. Jergelb,1, C. Falconyb, L. Ortegac, E. Lomonovad, R. Brunnera, Š. Chromike, M. Hartmanováa

a Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovakia

b Departmento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, 07300 México D.F., México

c Laboratoire de Cristallographie du CNRS, BP 166, 38042 Grenoble Cedex 09, France d General Physics Institute, Academy of Sciences, Moscow, Russia

e Institute of Electrical Engineering, Slovak Academy of Sciences, Dúbravská cesta 9, 842 39 Bratislava, Slovakia

Investigation of Zr(Y)O2 (or YSZ) thin films is interesting because of more reasons such as its application as buffer layer in YBCO superconductors or in plasma anodic SiO2 growth at room temperature through YSZ layer. The aim of the paper is i) to clarify the formation of polycrystalline structure of deposited YSZ and Si films on Si and YSZ crystals, respectively, depending on the substrate surface orientation and ii) to follow the evolution of the YSZ/Si interface properties at the initial stage of the plasma anodization. YSZ layers were deposited on silicon substrate (n-type, 1016 cm-3) by electron beam evaporation and subsequently annealed at 930°C for 30 minutes. Plasma anodic oxidation was performed for 20 minutes with the current density and sample temperature kept at 3.8 mA/cm2 and 250°C, respectively. The deposition of Si layers on YSZ crystals was made by MBE technique. Structural properties of all samples were inspected by X-ray diffraction at grazing incidence and electrical properties of YSZ/Si structures by frequency and temperature dependencies of the resistance, C-V characteristics, and deep level transient spectroscopy (DLTS). The X-ray measurements confirmed that YSZ film deposited on Si is amorphous or polycrystalline. A well developed face centered cubic (fcc) phase with lattice parameter of 0.509 nm is typical for the best YSZ layers, four intense 111, 200, 220 and 311 diffractions being usually detected. Yttrium oxide was not registered. The polycrystalline structure of Si-on-YSZ layers was affected by the orientation of YSZ substrate surface, namely (100) or (111). On the annealing procedure, the surface of crystalline silicon at the interface with deposited YSZ layer consisted of large polycrystalline blocks, their size being reduced by one order of magnitude after the plasma anodization. The YSZ/Si interface electrical properties were changed remarkably as found by DLTS which revealed a continuous spectrum of interface states originating due to the anodization. It is attributed to the formation of a very thin silicon oxide interlayer between YSZ layer and Si crystal.

Corresponding author *: Tel. 00421-2-5941 0543; Fax. 00421-2-5477 6085; E-mail: fyzipinc@nic.savba.sk 1 On the leave from the Institute of Physics SAS, Bratislava, Slovakia

TF10.29.P

A study of Al/Si3N4/ultrathin Si/GaAs structures by DLTS and C-V measurements

E. Pinčík a, , J. Bartoša, J. Ivančoa, R. Brunnera

a Institute of Physics, Slovak Academy of Sciences, Dúbravská cesta 9, 842 28 Bratislava, Slovakia

The major problem of GaAs-based MIS structures has been Fermi-level pinning at the interface. Improvements of the interface quality a consequently decreasing density of states for insulators on GaAs have been partly associated with the deposition of thin silicon interlayer. Due to the lattice mismatch between Si and GaAs the Si layer can be prepared only about 1.5 – 2 nm thick without introducing misfit dislocations. It has been demonstrated, that high quality Si3N4 thin films can be deposited by ECR plasma source. In this work, we present the application of DLTS and C-V techniques for monitoring the electrical characteristics of metal/Si3N4/Si/GaAs capacitors. We try to identify the Si interlayer as a very thin quantum well. We suppose and calculate an ideal interface between crystalline Si and GaAs, in which the band discontinuity depends only on the semiconductors involved. A quantum well can capture and emit charge carriers from the barrier region by the similar way as deep levels. We suppose that the carrier emission signal from the quantum well is included in the observed DLTS signal, but we had to distinguish between the carrier emission from deep levels at the Si/GaAs interface (and/or from the bulk of crystalline GaAs) and the emission from the quantum well. Therefore, we have performed for the case of very thin quantum well relevant theoretical calculations of: i) the thermal activation energy of the quantum well emission; ii) the emission rate of electrons from a quantum well; iii) the DLTS peak height; iv) the model of the C-V curve. Next, we will discuss DLTS and C-V measurements on the Al/Si3N4/Si(2 nm)/n-GaAs (~5·1017 cm-3) structures, in which three deep traps have been identified, with respective thermal energies - 0.19 eV, 0.40 eV and 0.69 eV. The former (0,16 eV) was identified as an emission from the quantum well introduced by means of an intermediate ultrathin Si layer. This interpretation is supported by the correlation between theoretical calculations of the thermal activation energy of the quantum well (QW), the emission rate of electrons from the QW and DLTS peak and C-V behaviors. Modeling of C-V curves revealed that at sufficiently positive bias voltages a quasi accumulation of electrons is reached.

Corresponding author *: Tel. 00421-2-5941 0543; Fax. 00421-2-5477 6085; E-mail: fyzipinc@nic.savba.sk Poster presentation

TF10.30.P

ERBIUM DOPING INTO CARBON THIN FILMS

Václav Prajzler a, Ivan Hüttel b, Pavla Nekvindová c, Josef Schröfel a, Anna Macková d, Jan Gurovič e and Jarmila Špirková c

aCTU, Faculty of Electrical Engineering, Department of Microelectronics, PraguebICT, Institute of Chemical Technology, Department of Solid State Engineering, Prague

cICT, Institute of Chemical Technology, Department of Inorganic Chemistry, PraguedAcademy of Science, Nuclear Physics Institute, Řež

eCTU, Faculty of Mechanical Engineering, Department of Physical Education, Prague

Thin carbon films exhibit specific optical and mechanical properties, which make them promising materials for integrated optics. These structures can be used as active waveguides, if we dope the deposited layers with erbium ions. Erbium doping into carbon thin films were realised using PACVD method namely these ways:

1. Thin carbon layers doped with erbium were deposit by sputtering by Ar ions from a carbon target with metal erbium.

2. Growth of carbon thin films from a gas mixture (CH4 + Ar + Erbium isopropoxide).3. Growth of carbon thin films using a gas mixture (CH4 + Erbium tris)4. Doping carbon thin films, which were prepared from gas (CH4), using erbium

nitrate dissolved in glycerol.

The fabricated films were characterized by using optical ellipsometry, ERDA, RBS and other methods.Good results were obtained when using the non-oxidizing media (glycerol) at low temperatures (25 – 120 °C) for times ranging from 10 min. - 500 hrs. After this energy-saving and harmless approach as much as 1.32 mole % of erbium was found in the treated samples. The fabricated thin layers exhibited waveguiding properties at 633 nm. The possibility of fabrication of the sandwich-like multiple layers was investigated as well. The sandwich structure consisted of up to three consequently PACVD deposited carbon layers. The deposition of the particular carbon layer was immediately followed with the diffusion of Er3+ the liquid source. The RBS measurement of the sandwiches revealed non-homogeneous distribution of the Er3+ showing three maxima, which corresponded to three deposited layers. Nevertheless, the depths of the erbium containing layers were up to 1 mm. Quite high concentrations (about 11 mole %) of the incorporated erbium were found also when the doping occurred during the PACVD using erbium tris (2,2,6,6 – tetramethyl – 3,5 – heptanedionate) was used as a precursor.

Corresponding author:Václav Prajzler Czech Technical University, Faculty of Electrical Engineering, Department of Microelectronics, Technická 2, 166 27 Prague, Czech Republic E-mail: vasek.prajzler@email.cz

TF10.31.P

IN-SITU STUDIES OF GASOCHROMIC SWITCHING

C. Salinga, P. Meyers, C. Liesch, T. Eleftheriadis, H. Weis, T. Pedersen, M. Wuttig*I. Physikalisches Institut, RWTH Aachen, D-52056 Aachen

Optical spectroscopy, spectroscopic ellipsometry and stress measurements are employed to study the kinetics and mechanism of gasochromic switching upon hydrogen exposure of several thin films systems including Pd, Mg, Gd and WO3. Stress measurements reveal that the smallest stresses of around 250 MPa are built up for WO3, where gasochromic switching is completely reversible. Stresses which are larger by up to 2 orders of magnitude are observed for Pd, Mg and Gd films. These other materials shown evidence for irreversible deformation upon hydrogen loading and at least for Mg also a rapid property degradation upon repeated switching.The kinetics of the switching process have also been studied by fast, time resolved measurements using optical spectroscopy and spectroscopic ellipsometry. Together with the stress measurements these data enable us to identify the atomic mechanism of hydrogen induced switching. Interesting enough these measurements reveal that the film thickness dereases upon hydrogen exposure.

Corresponding author: M. Wuttig Tel. +241-80-27155; Fax. +241-80-22331; E-mail: wuttig@physik.rwth-aachen.de

TF10.32.P

OPTICAL CHARACTERIZATION OF GaP1-xNx (x 0.024) LAYERS GROWN BY MOLECULAR BEAM EPITAXY

M.A. Santana-Aranda1, C. Mejía-García2, M. Meléndez-Lira1, G. Contreras-Puente2,M. López-López1, K. Momose3, A. Utsumi3, H. Yonezu3, Y. Furukawa3

1 Departamento de Física, CINVESTAV-IPN, México DF, Mexico2 Escuela Superior de Física y Matemáticas, IPN, México DF, Mexico

3 Department of Electrical and Electronic Engineering, Toyohashi University of Technology, Toyohashi, Japan

Nitrated III-V compounds open the possibility of monolithic integration on III-V based light emitting devices and Si based microelectronics. Small amounts of nitrogen in the GaPN alloy increase the light emitting efficiency of GaP. While lattice matching of GaPN to Si is accomplished with 2.1% of nitrogen. In this work, we present the characterization of GaPN layers with up to 2.4% nitrogen content grown on GaP substrates by molecular beam epitaxy. Photoluminescence, contact-less electro-reflectance and Raman scattering measurements are performed in order to characterize the quality of the layers, and compared to results obtained with high-resolution x-ray diffraction, atomic force microscopy and transmission electron microscopy. The photoluminescence spectra are red shifted with increase of nitrogen content. The behavior of the energy band gap determined with the electro-reflectance measurements is compared to previously published calculations and experimental determinations. GaP-like LO mode, as observed by Raman scattering, is shifted toward lower frequencies because of two contributions; alloying and strain. Furthermore, high-resolution x-ray diffraction reveals that GaPN layers are partially relaxed, which is supported by transmission electron microscopy and atomic force microscopy. Transmission electron microscopy shows dislocations and micro-cracks for the samples with higher nitrogen content. Atomic force micrograph of the sample with 2.41% of Nitrogen show the presence of some grooves parallel to the direction, that are related to the process of strain relaxation.

Corresponding author: M.A. Santana-Aranda Departamento de Física, CINVESTAV-IPN, Apdo. Postal 14-740, México DF 07000, México. Tel/Fax: +52-55-5747-3828; e-mail: msantana@fis.cinvestav.mx

TF10.33.P

ELECTROPHYSICAL PROPERTIES OF MIS STRUCTURES WITH SOL-GEL TiO2(La) DIELECTRIC FILMS

S. Simeonov1, E. Kafedjiiska1, A. Szekeres 1 , C. Parlog2 and M. Gartner2

1Institute of Solid State.Physics, 72, Tsarigradsko Chaussee, 1784 Sofia, Bulgaria2Institute of Physical Chemistry .Spl. Independente 202, Bucharest 77208, Romania

In this work capacitance-voltage (C-V) and current-voltage (I-V) characteristics of MIS

structures with sol-gel TiO2 dielectric films doped with lanthanum are studied. The

TiO2(La) films were deposited from titanium-lanthanum alkoxide solution, dried in air for

24 h and then, annealed in air at 700oC for 1 h. The film thicknesses, obtained by

ellipsometric measurements, were in the range 180-230 nm. The analysis of the C-V

characteristics reveals that the dielectric permittivity of the undoped TiO2 films is 60.5. For

TiO2(La) films with atomic ratio La/Ti=0.028 the permittivity increases up to 93.5. Further

increase of La/Ti ratio leads to decrease of the permittivity. Fixed dielectric charge is in the

order of 1011 cm-2. This charge is negative for undoped TiO2 and TiO2(La) films with the

highest ratio of La/Ti=0.22, while it is positive for the other La/Ti ratios. The energy

distribution of traps at the TiO2(La)/Si interface, evaluated from the C-V characteristics

measured at different temperatures, is in the order of 1012 eV-1cm-2. In the case of undoped

TiO2 and TiO2(La) films with the highest ratio of La/Ti the charge in the interface traps is

positive, while for the other cases it is negative. The conductivity of these TiO2(La) MIS

structures was examined by analysis of the I-V characteristics in wide temperature interval

(100-300 K. Trap-assisted tunneling and electron mobility in the conduction band of the

dielectric film are considered as possible transport mechanisms. On the basis of these

results the possible use of TiO2(La) films as gate dielectric for development of ULSI MOS

IC is discussed.

TF10.34.P

INFLUENCE OF THE SUBSTRATE TEMPERATURE ON STRUCTURAL PROPERTIES OF THIN SnO2 LAYERS PREPARED

BY PLASMA OXIDATION

Z. Stryhal1, J. Pavlik 1* , A. Mackova2, V. Perina2, P. Hedbavny3

1 J. E. Purkyne University, Department of Physics, Ceske mladeze 8, CZ – 40096 Usti nad Labem, Czech Republic

2 Nuclear Physics Institute of Acad. Sci. Of Czech Republic, CZ-250 68 Rez near Prague, Czech Republic

3VAKUUM PRAHA, V Holesovickach 2, CZ – 120 00 Prague 2, Czech Republic

We studied the surface and structure properties of the SnO2 thin films, which are widely used for gas sensor applications. Thin SnO2 films (< 40 nm) were produced by plasma oxidation of evaporated thin tin films on Pyrex, SiO2, and aluminium substrates.

The structure of such SnO2 films and also their chemical and physical properties depend on parameters governing the growth of these films during plasma oxidation, e.g. both on the plasma parameters and the substrate temperature. The substrate temperature is one of important parameters in surface physics experiments.

Our experimental set-up (the substrate inside the vacuum chamber fixed on a manipulator) does not allow a direct substrate heating during plasma oxidation. The substrate mounted onto a stainless steel holder was heated from the substrate backside by a quartz lamp as heat radiator. Temperature of the holder with substrate was measured by Pt100 temperature sensor.

The plasma source consisted of an axially movable quartz tube in which the capacitively coupled RF discharge (13.56 MHz) was generated in a pure oxygen or oxygen/argon mixture.

The surface morphology and structure of SnO2 films prepared at various substrate temperatures by plasma oxidation were analysed by Atomic Force Microscopy (AFM), and Rutherford Backscattering Spectrometry (RBS).

Corresponding author *: Tel. +420–47-5214417 ; Fax. +420-47-5212053; E-mail: PAVLIKJ@PF.UJEP.CZ

TF10.35.P

OXIDATION OF HYDROGENATED CRYSTALLINE SILICON AS AN ALTERNATIVE APPROACH FOR IMPROVEMENT OF

ULTRATHIN SiO2 PROPERTIES

A. Szekeres, A. Paneva* and S. AlexandrovaInstitute of Solid State Physics, 72 Tzarigradsko Chaussee Blvd., Sofia 1784, Bulgaria

*Faculty of Physics, Sofia University, 5 Bourchier Blvd., Sofia 1126, Bulgaria

The development of MOS devices requires ultrathin SiO2 layers with easily controllable thickness, high dielectric quality and perfect interfaces obtained at low temperatures (<900oC). The growth of reliable thin thermal oxide on silicon in thin-film regime is important for fabrication of smaller and faster MOS device structures. The pre-oxidation conditions of the Si surface play a decisive role and, hence, will influence the growth kinetics of ultrathin oxides and their properties. That is why in recent years increased attention has been paid to these issues.

In this paper we discuss the low-temperature growth of thermal oxide on (100) and (111) oriented silicon which underwent different cleaning procedures and present results on the properties of the formed SiO2/Si structures. As a tool of investigations, multiple-angle spectrocsopic ellipsometry is applied. We consider the temperature range 800-860oC for Si oxidation in an oxide thickness range of up to 20 nm. Prior to oxidation the Si substrates were cleaned by standard RCA procedure followed by rf hydrogen plasma. The latter is aimed at achieving hydrogenation of the Si near-surface region altering the oxidation kinetics.

The results show that the oxidation kinetics obeys a linear time dependence. The smaller activation energies and higher initial growth rates observed at oxidation of hydrogenated silicon indicate facilitation of oxide growth in the early oxidation stage. Formation of a less dense Si surface layer due to voids decorated with hydrogen is suggested to be responsible for the higher kinetics rates. The presence of hydrogen helps the growth of more perfect SiO2

network reflecting in an interface composition closer to stoichiometry and in lower intrinsic stress.

TF10.36.P

THE EFFECT OF THE CARRIER DIFFUSION AND RECOMBINATION IN SEMICONDUCTORS UNDER THE

TEMPERATURE FIELD ON THE PHOTOACOUSTIC SIGNAL

L. Villegas-Lelovsky, G. González de la Cruz, Yu. G. GurevichCentro de Investigación y de Estudios Avanzados del IPN, 07000 D.F. México

An analytic derivation is presented for the heat transport in bipolar semiconductors, taking

into account generation and heating of carriers on the surface due to an incident modulated

laser beam on the surface and finite carrier diffusion and recombination in the solid under

inhomogeneous temperature distribution. The temperature distribution in the limit of the

one temperature and two temperatures as function of the position and time in the

semiconductor is calculated using appropriate conditions according to the photoacoustic

experimental set up. In addition, special emphasis is made on the effect of the

inhomogeneous temperature distribution on the heat power density generated in the sample

due to the recombination of the electron-hole pair in the photoacoustic signal. In the case of

two temperatures is showed that both the carrier current density and the carrier heat flux

turn out to be depending of the electron and hole temperatures. The frequency dependence

of the amplitude and phase signal obtained from electron and phonon temperature

distributions are analyzed for characteristic parameters of the problem: the thermal

generation rate of carriers concerning to difference of the temperatures involved and the

electron-phonon energy interaction. In order to do it remarkable we neglected the carrier

heating on the surface of the sample.

Corresponding author *: Phone and Fax: +52 55 57 47 38 28; E-mail: lvl@fis.cinvestav.mx Physics Department, CINVESTAV-IPN, Apartado Postal 14-740, 07000, Mexico DF, Mexico