PhD Thesis Violetta Gianneta

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Transcript of PhD Thesis Violetta Gianneta

  • - l2O3 Si

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    2009

  • This thesis is part of the 03ED375 research project, implemented within the framework of the Reinforcement Programme of Human Research Manpower (PENED) and co-financed by National and Community Funds (20% from the Greek Ministry of Development-General Secretariat of Research and Technology and 80% from E.U.-European Social Fund). 03ED375 () (20% - 80% ).

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  • Abstract In the present thesis, the growth of porous anodic alumina films on Si substrate

    was studied extensively. Potential applications of porous anodic alumina films formed

    directly on Si, regarding the use of porous membranes as mask or template for various

    nanostructures growth directly on Si, are discussed.

    Chapter one deals with the theory and mechanisms governing porous anodic

    alumina film growth, either on porous anodic films formed by anodization of

    aluminum foils, or on porous anodic films developed on Si substrates. Additionally,

    the effect of different factors (pH, temperature, applied voltage) on the final structural

    characteristics is presented.

    In chapter two, the preliminary processing steps regarding sample preparation

    before the anodization procedure are quoted. Moreover, details about the experimental

    set-up and the electrochemical conditions used during the sample anodization in the

    current work are given.

    In chapter three, the influence of three different factors, in the final structural

    characteristics, is investigated. Primarily, the impact of the initial aluminum thickness

    deposited on Si substrate, and secondly the confinement of the aluminum film in areas

    of a few m2, in the pore size and pore density are studied. Finally, the influence of

    the third factor is associated with a three-step instead of a two-step anodization, in

    combination with an in-between step of aluminum chemical etching, on the ordering

    and the uniformity of the pores.

    The deposition of Ti and Cr nanodots arrays on Si, using the porous alumina

    membrane as a masking layer, is investigated in chapter four. Furthermore, the Ti

    nanodots are used for the electrodeposition of Au nanodots and nanowires inside the

    porous alumina films. Additionally, the Cr dots are used as metallic nanostructured

    mask for the Si etching by reactive ion etching process, that leads to the formation of

    Si nanopillars on Si substrate.

    In chapter five the growth of hexagonally ordered SiO2 dots on Si through

    porous anodic alumina membranes, in various acidic electrolytes, is studied.

    Moreover, the electrical characterization of the interface of porous alumina film/Si

    and porous alumina film with SiO2 dots in pore bottoms/ Si is presented. Finally, in

    the present thesis the technology of fabrication of Si nanocrystals embedded in SiO2 dots arrays through porous alumina membranes on Si substrate is developed for the

  • first time. This was achieved by the combination of ion beam synthesis with the

    already existing technology of porous anodic alumina growth on Si substrates. The

    nanocrystals are electrically isolated from the substrate. This technique is promising

    as an application in non-volatile memory devices.

    The main achievements accomplished through this study are summarized as

    follows:

    The optimization of pores ordering by developing the porous alumina membrane in two or three processing steps in combination with the chemical

    etching of Al film, lying above the porous membrane, following each

    anodization cycle.

    The increase of pores density by the confinement of porous alumina film in areas of a few m2 on Si.

    The development of Ti and Cr nanodots arrays, directly on Si, through porous alumina membranes. The use of Cr nanodots as nanostructured masking layer

    for the formation of Si nanopillars, formed by etching of Si substrate with

    RIE, on Si.

    The density of interface stages results from the electrical characterization of porous alumina with or without SiO2 dots at each pore bottom, with the Si

    substrate. The results are encouraging, keeping in mind that the pore

    membranes and SiO2 dots were electrochemically grown directly on Si

    substrate.

    The development of distinct Si nanocrystals, embedded in SiO2 dots, combining for the first time two different technologies, that is the fabrication

    of porous anodic alumina films directly on Si substrate, as well as the ion

    beam synthesis technique. The proposed technique is promising for the

    fabrication of non-volatile memory devices.

  • . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

    . . . . . . . . . . 7

    .1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

    .1.1 . . . . . . . . . . . . 9

    .1.2 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 .1.2 . . . . . . . . . 12

    .1.2

    Si . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 .2 . . . . . . . . . . 19

    .3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

    .4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 .5 . . . . . . . . . 27 .5.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 .6 , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 .6.1 pH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32 .7 . . . . . . . . . . . . . . . . . . . . . . . . . 33 .7.1 10% . . . . 34 .7.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

  • .8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 .8.1 Faraday . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

    .9 . . . . . . . . . . . . . . . . . . . . . . 42 1.9.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

    .10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

    .10.1. / Si . . . . . . . . . . . . . . . . . . 49

    .11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

    - - . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 .1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56

    .2 . . . . . . . . . . . . . . . . . . 59

    .3 . . . . . . . . . . . . . . . . . . . . . 62

    .4 . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

    II.5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64

    Si . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65 .1 . . . . . 66

  • .2 Al . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

    .3 . . . . . . . . . . . . 84 .4 . . . . . . . . . . . . . . . . . . . 89 .5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94

    V

    . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

    IV.1. Ti Cr Si . . . . . . . . . . . . 99

    V.1.1 Ti Cr Si . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

    V.1.2 . . . . . . . . . . . . . . . . . . . . .107

    V.1.3 IV.I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110

    IV.2. Ti Au . . . . . . . . . . . . . . . . . . . 111 IV.3. Cr Si Si Si . . . . . . . . . . . . . .