Our activities on ABO 3 oxides Our activities on ABO 3 oxides Some information about DFAV Some...

• Our activities on ABOOur activities on ABO33 oxides oxides

• Some information about DFAVSome information about DFAV• Brief summary on the activities of other groups Brief summary on the activities of other groups or DFAVor DFAV

University of Pavia

Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta” DFAV DFAV

Survey on activities on ABOSurvey on activities on ABO33 oxides oxides

University of Pavia University of Pavia Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta”

LiNbO3 Characterization of LN substrates

Characterization of structural and photoinduced defects

Microstructures in LN by means of fs laser pulses

Staff and experimental facilities

Materials and Collaborations

Basic physical problems of interest

•KTO/KLTN/BCT

•Charge transport and trapping in KTO

•Doping in KTO

Examples

Kiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

Staff members:

Giorgio Samoggia Full Professor Carlo Bruno Azzoni Associate Professor

H. of D.Pietro Galinetto ResearcherEnrico Giulotto ResearcherDaniela Grando * ResearcherMaria Cristina Mozzati Contract

ResearcherFrancesco Rossella Ph.D. StudentDorino Maghini TechnicianMassimo Marinone Graduate StudentVirginia Stasi Graduate StudentMassimiliano Rossi Graduate Student (USA

LBL)*Electronics Departmente-mail : [email protected]


Experimental facilitiesExperimental facilities

•Raman and micro-Raman spectroscopy

•Optical absorption, PL, TL, PC, TSC

•Hall, Photo-Hall and magneto-optical spectroscopy

•EPR spectroscopy and Photo-EPR

•Static magnetization measurements

•Electro-optical characterization

•Femto-second laser sources

•Dielectric permittivity spectroscopyKiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

Materials

LiNbO3

K1-xLixTa1-yNbyO3

Ba0.77Ca0.23TiO3

LiNbO3/LiTaO3KTaO3

BaTiO3

KNbO3

SrTiO3

LiTaO3

FeCrMgCuHfV…

Single crystals

thin films

Nano-particles diluted in silica glass

Nanosized grains ceramicsKiev 2005, February 2nd – P. Galinetto DFAV University of Pavia

Kiev 2005, February 2nd – P. Galinetto DFAV University of

Pavia

UniCatt. Physics Dept- Brescia

INOA Firenze

C.n.r. IMM Bologna

Dip. Fisica - Padova

C.n.r. Ist. di Cibernetica Napoli

Collaborations

Saes Getter S.p.a.

Avanex 2 Co.

A.F. Ioffe Physical & Technical Institute – S.Petersburg – RU

Materials physics department – UA Madrid - E

Fachbereich Physik, University of Osnabrueck - DE

Institute of Physics, AS CR, Prague RC

Dept of Mat. Science, Ukrainian Acad.of Sciences, Kiev, Uk

Main Basic Physical PhenomenaMain Basic Physical Phenomena

•Phase transitions (PT) in pure and mixed oxides based on ABO3 (KTO, STO, BTO, etc) compounds

•Structural, electronic and optical properties of intrinsic and impurities defects in ABO3 related materials

•Study of the transport phenomena and charge localization due to optical irradiation in ABO3 compounds


Study of self-ordering and of new phase transitions in soft matrices containing interacting degrees of freedom of impurities and Jahn-Teller polarons

Doped KTO, KLT, KLTN

PT temperature ranging from LT to RT and morecomplex interplay between Li-dipoles and Nb-dipoles character of soft-mode and relaxation order-disorder PT, magnitude of dielectric susceptibility, and very interesting new matrix and impurity mode coupling effects,new PT and related phenomena.

Phase transitions in mixed oxides…..

Prof. Blinc, Opening talk EMF Cambridge 2003


KLTN 0.14/1.2KLTN 0.14/1.2

KLTN 0.4/3.1KLTN 0.4/3.1

0 20 40 60 80 100 120 140 160 180 200 220 2400

500

1000

1500

2000

2500

3000

3500

Inte

nsi

ty (

arb

.un

its)

Raman Shift (cm-1)

17 K 30 K 60 K 100 K 130 K 150 K 180 K

KLTN 0.6/17.3 + Cu, VKLTN 0.6/17.3 + Cu, V

Investigations of PT in KLTN combining Raman and dielectric spectroscopy


Isovalent substitution Isovalent substitution BaBa2+2+ Ca Ca2+2+

Ca has smaller ionic radius (Ba= 1.35Ca has smaller ionic radius (Ba= 1.35Å vsÅ vs Ca= Ca= 0.990.99ÅÅ) )

Influence on Curie temperatureInfluence on Curie temperature

Source of structural disorderSource of structural disorder

Congruently grown barium calcium titanate,

Ba0.77Ca0.23TiO3 (BCT77/23) can be fabricated as high

optical quality single crystals, possess large electro-optic coefficients. Another great advantage of BCT is that the tetragonal-ortorhombic phase transition, which is destructive in BaTiO3, is depressed in BCT 77/23 holographic sensitivity making it excellent candidate for various photorefraction based applications


0 50 100 150 200 250 300

30

40

50

60

70

80

(cm

-1)

T (K)

2

3

4

5

6

inte

grat

ed in

tens

ity (a

.u.)

260

270

280

290

300

310

(cm

-1)

FWHM, integrated intensity and energy for the mode at 300 cm-1

The A-mode hardens

0 50 100 150 200 250 30020

40

60

(c

m-1

)

T (K)

1

2

3

4

Inte

grat

ed in

tens

ity (a

.u.)

42

44

46

48

(c

m-1

)

FWHM, integrated intensity and energy for the mode at 40 cm-1

The E-mode softens

Lowering the temperature...

•PHOTO-INDUCED EFFECTS ON PT IN KTO, STO

•?Nano-materials?: effect of nanometric scaling on the occurrence and the nature of phase transition in BTO, KTO and STO

Photo-induced transport phenomena and charge localization of ABO3 compounds

0 40 80 120 1600

50

100

150

5 10 15 20 25

1

10

100

Inte

grat

ed in

tens

ity (

arb.

un.

)

Temperature (K)

#3 "as grown" #3 after oxidation #542

E=0.16 eV

E=0.08 eV

Inte

grat

ed in

tens

ity (

arb.

un.

)

1/T (K-1)

10-2

10-1

100

101

102

1x103 B

PC

(A

)

(PC + PL) vs T

TL

TSC

+ EPR + photo-EPR


Cu centres in KTO……impurities defects in ABO3


Characterization of Cu centres in KTO

Other dopants like Be, Co, Ni

Absorption due to polarons in KTO:Be

LT Absorption, EPR, PhotoEPR, Phototransport, PL, TL, TSC

300 400 500 600 700 800

0.2

0.4

0.6

0.8

KTBe456t Be (transparent) KTBe456b Be (blue) KTPC340 pure (pale yellow) KTPC340c CuO (pale green/blue) KTGRN yellow KTCO2 Co (green)

Op

tica

l Den

sity

Wavelenght (nm)

400 500 600 700 8000.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

KTBe456t Be (transparent) KTBe456b Be (blue) KTPC340 pure (pale yellow) KTPC340c CuO (pale green/blue) KTGRN yellow KTCO2 Co (green)

Op

tica

l den

sity

Wavelenght (nm)

EPR+PhotoEPR +Abs

Characterization of structural, optical and electronic properties of LiNbO3 crystals and substrates in connection with different growth processes and different doping

Study of the transport phenomena and charge localization due to optical irradiation of LiNbO3 (or other ABO3 compounds, eventually doped) and of the irradiation effects on the linear and nonlinear optical properties

Study of the feasibility of 1D, 2D and 3D periodical structures, waveguides and microstructures on LiNbO3 (or other ferroelectric oxides) crystalline substrates by means of femtosecond laser irradiation in the transparent spectral region

Keypoints of activities on LiNbO3

Crystalline quality1

2

3


How we study crystalline How we study crystalline quality?quality?

•Raman and micro-Raman spectroscopy

•Optical absorption, PL, TL, PC, TSC

•Hall, Photo-Hall and magneto-optical spectroscopy

•Ellipsometry

•Electron Paramagnetic Resonance (EPR) and Photo-EPR

•Static magnetization measurements

•Electro-optical characterization

•Femto-second laser sources *Kiev 2005, February 2nd – P. Galinetto DFAV University of

Pavia

Lattice of ideal, defect-free LN crystal

coupling and mutual influence of intrinsic and extrinsic defects

decrease of the intrinsic defect concentration

Due to the Li-deficiency the conventional congruent crystals have high concentration of intrinsic (non-stoichiometric) defects, which can easily compensate a high concentration of extrinsic defects (for instance, optically or acoustically active impurities)

Possibility to vary both the [Li]/[Nb] ratio and [O] contents (in addition to the modification by dopants!) is a very powerful tool for the optimisation of crystal parameters

•strong increase of the spectrum resolution due to line narrowing

•changes of some LN properties

•appearance of new impurity centers

EPR

Raman


EPR spectroscopy :•Control of the material quality:

check of purity of growth processesdetection of defects and/or unwanted EPR active magnetic

impurities information about structural disorder

•Evaluation of the oxidation state of the transition ions•Information about site symmetry from the EPR signal angular dependence

Fe3+ EPR lines (BIc) in CLN (LN:Fe 0.1%)

…in quasi-st LN(LN:Fe 0.1%) 500 1000 1500 2000 2500

Der

ivat

ive

EP

R S

ign

als

(arb

. un

.)

B (G)


Raman in LiNbO3In crystals, Raman spectrum depends on the direction and

polarization state of the incident and scattered light with respect to the cristallographic axes

Porto notation: ki(ei,ed)kd

The crystal structure of pure LiNbO3 has Rc3 space group symmetry and 4A1+ 9E Raman-active modes are predicted by factor-group analysis

b

a

a

zA

00

00

00

:)(1

00

00

0

:)(

d

c

dc

xE

00

0

00

:)(

d

dc

c

yE


0 200 400 600 800 1000 12000.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

In

tens

ity (

arb.

units

)

Raman Shift (cm-1)

z(x,x)z x(z,z)x

RS is strongly sensitive to orientation

Elight | c

Elight // c

-Raman to check disorientation, multidomains…


RS is sensitive to the deformation of the lattice and to the presence of point defects, becoming a powerful tool to deal with the problem of stoichiometry

The mode at 880 cm-1 is the vibration, parallel to the c axis, of the oxygen ions which consists basically in the stretching of the Nb–O and Li–O bonds.

800 820 840 860 880 900 920 940

0

1

2

3

4

5

6

7

Inte

sity

(ar

b.un

its)

Raman Shift (cm-1)

When a Nb ion sits at a Li site its oxygen first neighbors increase their bonding forces respective to the perfect crystal situation because of the stronger electrostatic interaction.


Can be used to check the stoichiometry (Li/Nb ratio)

monitoring the changes of linewidth of some Raman modes. FWHM changes are greater than

peak shift.

100 120 140 160 1800.0

0.5

1.0

1.5

CL1

CL2

q-SLCL3

Inte

nsit

y (a

rb.u

nits

)

Raman Shift (cm-1)

800 820 840 860 880 900 920 9400

1

2

3

4

5

6

7

8

q-SLCL1

Inte

sity

(ar

b.un

its)

Raman Shift (cm-1)

48.0 48.5 49.0 49.5 50.05

10

20

25

30

FWHM @ 152 cm-1

FWHM @ 870 cm-1

(c

m-1)

Li content (mol%)

The fact that the linewidth of some Raman modes scale with the composition xc =

[Li]/([Li] + [Nb]) of LN crystals, together with the use of a confocal microscope (

Raman), allows a 3D determination of the sample stoichiometry.


0 20 40 60 80 1009

10

11

12

= 1 cm-1

FWH

M (

cm-1)

depth ()0 2000 4000 6000 8000 10000

9.0

9.5

10.0

10.5

11.0

11.5

12.0

FWH

M (

cm-1)

spot position at 10 m depth (m)

Scan at 10 microns depth in a 10 mm

long plateDepth profile

Li/Nb changes ˜ 0.08 %

good homogeneity of Li/Nb ratio (changes less than 0.3 cm-1)

Non-destructive structural toolNon-destructive structural tool

Micron-scale spatial resolutionMicron-scale spatial resolution

Presence of a structurally disordered layerPresence of a structurally disordered layer

Effectiveness of damage removal methodEffectiveness of damage removal method

Control on optical surface finishingControl on optical surface finishing

Raman for surface quality analysis after wafering process:Raman for surface quality analysis after wafering process:


Important complete characterization of: stoichiometry, nature and content of impurities, degree of structural disorder before starting with investigation of charge trapping mechanisms and phenomena related to photo-induced defects

Study of the transport phenomena and charge localization due to optical irradiation of LiNbO3 (or other ABO3 compounds, eventually doped) and of the irradiation effects on the linear and nonlinear optical properties

2

• Photovoltaic current, photoconductivity,

• Photo-EPR

vs %, doping, T


complementary techniques (Raman microscopy, Electron Paramagnetic Resonance, optical absorption, photo-voltaic current and photo-conductivity measurements) were used to detect intrinsic and extrinsic defects, charge trapping and recombination processes, and the related photo-refractive behaviour in lithium niobate single crystals, with congruent and stoichiometric composition, containing Fe and Mg dopant. The role of UV and visible irradiation was investigated.

Comprehension and control of the photocarrier localization mechanisms in connection with preparation methods and treatment of the materials.

Characterization of structural and photoinduced defects in pure and doped lithium niobate

The properties of LN crystals are not simply ruled by the stoichiometry (Li/Nb ratio) and by intentional or accidental impurities: interrelations of intrinsic and extrinsic defects ever exist, leading to different phenomena in samples with apparent similar composition. In this frame it is important to perform experiments in crystals well characterized in terms of stoichiometry, impurity content and degree of structural disorder.ExperimentalExperimental

VIS-UV

UV

Charge transport and trapping phenomena

Photovoltaic and Photocurrent

Raman scattering, optical absorption, EPR

Foto-EPR

130 140 150 160 170 180

1

2

3

E mode at about 150 cm-1

Inte

nsi

ty (

arb

. un

.)

Raman Shift (cm-1)

Sp SFe CFe Cp CFM

825 850 875 900 925

0.2

0.4

0.6

0.8

1.0

1.2

1.4

1.6

1.8

A mode at about 870 cm-1

Raman Shift (cm-1)

In

ten

sity

(ar

b.u

nit

s) Sp CFe Cp CMg SFe CFM

Raman spectroscopy Raman spectroscopy

1 2 3 4

0.5

1.0

1.5

SFeCMF

CpCFe

CFe5%

Opt

ical

den

sity

energy (eV)

Optical absorptionOptical absorption

Shift in the ”optical edge”

Absorption Band at ~ 2.6 eV,

Fe2+Mg doping: decrease in the polaron induced abs band

antisites NbLi

Absorption Band at ~ 1.5 eV polarons

0 2000 4000 6000 8000

x0.2

x10

x20

CMg

CFM

Cp

CFe

Sp

SFe

Der

ivat

ive

EP

R S

ign

als

(arb

. un

.)

B (G)

EPR EPR B c-axisB c-axis

Sfe: componenti a 380 G e 1440 G, più intense, con la minore larghezza di riga (ΔB) e forma quasi simmetrica, in accordo con stechiometria nominale

SFe e CFe hanno stechiometria in accordo con quella nominale, paragonabile quantità di Fe3+ e, in particolare SFe, buona

qualità del cristallo

SFe e CFe hanno stechiometria in accordo con quella nominale, paragonabile quantità di Fe3+ e, in particolare SFe, buona

qualità del cristallo

CMF: transizione –½ +½, indipendente dalla simmetria puntuale, è la più intensa alto grado di disordine nei siti reticolari di Fe, indotto dal drogaggio di Mg, porta allo “spread” e quindi all’allargamento e alla scomparsa delle componenti a bassi campi di risonanza.

Appl. Phys. A 56, 103-108 (1993)

Fe3+: presente in tracce anche nei campioni nominalmente puri, non rilevato solo in CMg.

Cfe: righe più larghe e asimmetriche. BCFe è circa 3 volte BSFe (valori in accordo coi risultati di ΔB vs. xc di letteratura).

0 100 200 300 400 500-10

-8

-6

-4

-2

0

2

4

6Ar-ion laser source: 514nm, 15mW

J (1

0-6A

/m2 )

CFe SFe CFM

time (s)

Photovoltaic current and Photoconductivity Photovoltaic current and Photoconductivity

VISIBLE

UV

0 100 200 300 400-50

-40

-30

-20

-10

0

10

20

30

40

Xe-lamp, broad-band UV light, 70 mW

J (1

0-6A

/m2 )

time (s)

CFe SFe CFM

0 100 200

-3

-2

-1

0

J (1

0-6A

/m2 ))

time (s)

2.725 0.1 0.17 CFM - UV

2.37 0.13 0.044 -CFM – 514 nm

0.58 1.55 3.4 SFe - UV

0.16 0.023.6 -SFe – 514 nm

0.04 0.031 0.79 CFe - UV

0.036 L 0.054 H 3.02 -CFe - 514 nm

JDARK (10-6A/m2) JPHC (10-6A/m2) JPHV (10-6A/m2)

Jphv is proportional to the number of Fe2+, while Jphc is proportional to the [Fe2+]/[Fe3+] ratio

This one-center model was refined, adding to the scheme the intrinsic defects NbLi, which can take part in the charge transport as shallow electron traps, lowering the n-type Jphc

Campo applicato: 60kV/m. Contatti normali all’asse ottico (asse c).

Study of the feasibility of 1D, 2D and 3D periodical structures, waveguides and microstructures on LiNbO3 (or other ferroelectric oxides) crystalline substrates by means of femtosecond laser irradiation in the transparent spectral region

3

“MICROSTRUCTURAL MODIFICATION OF LINBO3 CRYSTALS INDUCED BY

FEMTOSECOND LASER IRRADIATION”Appl. Surf. Science in press


Femto-writing e femto-sculptureFemto-writing e femto-sculptureAdvantage of the method: Advantage of the method: i irradiation in the transparence region

higher penetration length

very high peak intensity multiphoton absorption cascade ionization

the energy transfer is confined in the focal volume

Possible effects: Possible effects:

•Refraction index changes due to photorefractive/stresses/structural changes

•Ablation – optical breakdown


Gratings written by means of ultrashort pulses (100fs) with interferential method in glassesApplied Surface Science 197

(2002) 688, M. Hirano et al.

Wave-guide laser writing in transverse and longitudinal geometry

Experimental Set-up

Ti:Sapphire oscillator

25 nJ-130 fs-82 MHz

Ti:Sapphire amplifier

1 mJ-130 fs-1 kHz

Dichroic mirror

CCD camera

in situ monitoring

Sample on motor controlled xyz stage

mirror

shutter

/2 sheet

isolatore

polarizer

objectiveMonitoring channel

filters

mirror

= 810 nm

/2 sheet

Commercial z-cut congruent LN substrates.

At the LaserLab of Electronics Dept


The main effect of the irradiation in this regime was the formation of refractive index microstructures, visible at the polarizing microscope.

Ti:Sapphire oscillator, LE + HRR

At the focus region either refractive index changes or material removal were observed at variance of irradiation conditions.

Formation of large ablated regions (>10 m) triggered by the presence of crystal defects, surface scratches or accumulation centers.

200 400 600 800 1000

Raman Shift (cm-1)

Ram

an

In

ten

sity

(arb

.un

its)

Oscillator ablationAmplifier ablation

200 400 600 800 10000

2000

4000

6000

8000

10000

Y A

xis

Titl

e

X Axis Title

B D F

Raman shift (cm-1)

AFM


3μm-step grating

Efficiency:

10% - 1st order (red light)

Grating diffraction spots

10μm


laser source (He-Ne): 20 mW , λ = 632.8 nm

Integrated Optical microscope Olimpus Spot diameter 10 µm ÷ 1 µm depending on the objectives (10X, 50X, 100X), autofocus by means of piezoelectric driver Back-scattering geometry

Spectrometer focal length = 300 mm , 2 holographic gratings (1800 gg/mm or 600 gg/mm). Resolution 0.2 cm-1

Holographic notch filter

CCD 256 X 1024 pixels (pixel = 27 µn, 16 bit dinamical range), Peltier cooled system

Experimental set-upconventional Labram Dilor JYHoriba (mod. 010)

60 cm

EPR spectrometer


Apparato di misura: MAGNETOMETRO SQUID

Cosa misura:

momento magnetico“m” di un campione,

da cui si determinano suscettività magnetica e magnetizzazione

Unità di misura: emu (erg/G)

Range di misura di “m”: 10-8 2

emu (condizioni standard)

Errore di misura: in genere < 2%

Come misura:

Sonda bobina superconduttrice connessa

a uno SQUID che rileva la variazione del flusso

magnetico provocata dal movimento del

campione attraverso la bobina stessa (tecnica a

estrazione).

other research activities

Colossal Magnetoresistive Material (La1-xAxMnO3 A = Ca, Na)

CaCu3Ti4O12 (CCTO): high-k material

Li3VO4:Cr,Mg ionic transport, SHG

Ultrafast spin dynamicsin ferromagnetic thin films transient MOKE


Dipartimento di Fisica “A. Volta”Dipartimento di Fisica “A. Volta”

12 full professors

18 associate professors

10 researchers

15 technicians

30 post graduate, PhD and fellowship students


Sources of budget (~)

1990

20%

0%45%

10%25%

National Grant Eu-Int Grant UniPV Private companies INFM

2004

0%7%

8%

35%

50%

National Grant Eu-Int Grant UniPV Private companies INFM


•Physics education and physics history

•Quantum information theory

•Optical spectroscopy & laser-matter interaction in semiconductors

•Magnetism and superconductivity Magnetism and superconductivity

Research activities of other groups


PHYSICS EDUCATION and PHYSICS HISTORY GroupStaff: G. Bonera, L. Borghi, A. De Ambrosis, L. Falomo, L. Mascheretti, M.C. Garbarino, L. Cardinali

*Identification of tools and strategies to support the Physics teaching/learning process

*Historical comprehension of the developments of different physical branches, taking into account not only the technical aspects but also the global cultural and social context.

QUANTUM INFORMATION THEORY GROUPStaff: GM D’Ariano, C. Macchiavello, M. Sacchi, P. Lo Presti, R. Buscemi, E. Chiribella, P. Perinotti

•Quantum Measuring Devices for Photonics and Quantum Information •Entanglement Assisted High Precision Measurements •Quantum Teleportation and Quantum Cloning by the optical parametric squeezing process •Quantum Properties of Distributed Systems


MAGNETISM AND SUPERCONDUCTIVITYMAGNETISM AND SUPERCONDUCTIVITYDipartimento di Fisica “A. Volta”, Universita’ di Pavia and INFM, Via Bassi 6 , I-27100 Pavia (Italy)

Techniques : Nuclear Magnetic Resonance (NMR, mainly in Solids)Muon Spin Rotation (MUSR) Susceptibility and magnetization (SQUID)Specific heat Magnetic Resonance Imaging (collaborations)

Team : Prof. A. Rigamonti, Prof. F. Borsa, Prof. P. Carretta, Prof. M. Corti, Dr. A. Lascialfari, p.i. S. AldrovandiPost-doc : J. LagoPhD and graduate students : I. Zucca, L. Spanu, E. Micotti, N. Papinutto, M. Filibian, M. Mariani


Motions and structure of flux lines lattice in Motions and structure of flux lines lattice in superconductorssuperconductors

Diamagnetic fluctuations above TDiamagnetic fluctuations above TCC in BCS superconductors (MgB in BCS superconductors (MgB22))

Quantum Phase transitions (Quantum Critical Point)Quantum Phase transitions (Quantum Critical Point)

CeCuCeCu6-x6-x Au Auxx

Low-dimensional Low-dimensional quantum antiferromagnets (S=1/2) quantum antiferromagnets (S=1/2)

La2CuO

4

SrCu2

O3

Sr2CuO

3

Cu8

Negligible intermolecular interactions molecular nanomagnets

Molecular nanomagnetsMolecular nanomagnets

Fe8 crystal

Easy-axis (magnetization)

Fe (3+) s=5/2 ground state S=10 (giant spin)

Quantum tunneling of the magnetization (QTM)Quantum tunneling of the magnetization (QTM)

Optical Spectroscopy & Laser-Matter Interaction

Optical Spectroscopy Laboratory

M. Galli, D. Bajoni, M. Patrini, M. Belotti, G. Guizzetti, F. Marabelli

Nonlinear Optics Laboratory

A.M. Malvezzi, M. Patrini, G. Vecchi, C. Comaschi

Electronic and photonic nanostructures: theory

D. Gerace, M. Liscidini, M. Agio, A. Balestrieri, L.C. Andreani


Optical Techniques

Linear:•angle-resolved reflectance & transmittance

•spectroscopic ellipsometry

•modulation spectroscopies (photo-, electro- and thermo-reflectance).

Nonlinear : •Raman scattering •luminescence and •second-harmonic generation•time-resolved spectroscopy


Optical Spectroscopy Laboratory Facilities

•FFT-IR spectrometer, 20-5000 cm-1, with accessories for reflectance and transmittance measurements, cryostat for T= 4-300 K, micro-reflectance apparatus and optical microscope for high spatial resolution

•FT-Step Scan, with spectral extension up to the visible (20 – 50000 cm-1) for phase-sensitive detection and time-resolved spectroscopy (> 1 s) in reflectance and transmittance.

•Spectrophotometer 200-3300 nm, with cryostat for T = 12 - 300 K, and accessories for transmittance and reflectance in the specular and diffuse configurations (250-2500 nm).

•Spectroscopic ellipsometer (250 - 900 nm), with macro- and microprobe (minimum spot size 100 microns) .

•Micro - Raman apparatus with He-Ne laser source, microprobe (down to 1 micron) and stage for mapping, CCD camera detector.

•Atomic Force microscope

Laser Matter Interaction Laboratory Facilities

• CW picosecond laser system 80 MHz, 40 ps, > 10 W @1.053 µm , 1.5 W @ 0.53 µm, THG and FHG

• CW femtosecond laser system, 130 fs, 760 - 840 nm, 2 W

• CW femtosecond OPO, 80 MHz, 1.4 - 2 µm

• Detection facilities from UV to IR, lock-in, average, photon counting

• Nonlinear measurements, 2nd and 3rd harmonic generation

• Photonic crystals and waveguides

•Metallic and semiconducting nanoparticles in dielectric matrices

•SiGe Q-dots for integrated optics Si-compatible

• Q-dots InAs/InGaAs for laser @ 1.3 – 1.55 micron

• III-V structures for photovoltaic applications

Research activities

Si

SiO2

– X ( = 0°)

In any case…

Thanks!

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