Semiconductive films

A doped material was prepared by plasma polymerisation using 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) [67]. Electrical conductivity of the iodine-doped material decreased by five orders of magnitude and the iodine doping caused a serious structural change. 

A structural and electrical survey for conductive phenomena was performed using acetonitrile plasma polymerised film [68]. This polymer was discovered to have two states of electrical condnction. Electrical conduction in the high condnction state was sensitive to the nature of electrode material. Electrical conduction in the low conduction state was unaffected by the electrode material. 

Organometallic compounds were used to fabricate semiconductive thin films on different substrates by glow discharge polymerisation [69]. Tetramethyltin (TMT) and diethylzinc (DEZ) were deposited on several substrates such as polypropylene, Sn02, quartz and glass. The physicochemical properties of the deposited films were characterised by FTIR, XPS, SEM and X-ray diffraction. 

Plasma-polymerised thiophene for passivating the surface defects on GaAs has been employed [70]. The paper showed the passivation of GaAs surface was made possible by sulfur present in an overlayer, provided by the thin film of plasma-polymerised thiophene. The deposition of polythiophene lowered the barrier height, reduced the surface recombination velocity and increased diffusion length. 

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Eq. (14.43) requires accumulation to extend all along the channel, namely Vdcontact with the rest of the semiconductor layer, we have also to account for the bulk conductivity of the semiconducting film when integrating the drain current, which leads to an equation of the form... 

Eq. (14.51) can be substantially simplified if we assume that C, 2> C which is indeed the case when the semiconducting film is thinner than the insulating layer. The drain current in the linear and saturation regimes is then respectively given by... 

Let us add here that the fabrication of polycrystalline semiconductive films with enhanced photoresponse and increased resistance to electrochemical corrosion has been attempted by introducing semiconductor particles of colloidal dimensions to bulk deposited films, following the well-developed practice of producing composite metal and alloy deposits with improved thermal, mechanical, or anti-corrosion properties. Eor instance, it has been reported that colloidal cadmium sulfide [105] or mercuric sulfide [106] inclusions significanfly improve photoactivity and corrosion resistance of electrodeposited cadmium selenide. 

Mitzi, D. B. Kosbar, L. L. Murray, C. E. Copel, M. Afzah, A. 2004. High-mobihty ultrathin semiconducting films prepared by spin coating. Nature 428 299-303. 

Klechkovskaya, N. N. Maslov, V. N. Muradov, M. B. 1989. Growth and structure of semiconducting films of CdS, ZnS, and solid solutions based on them, obtained by the mechanisms of chemisorption from solutions of electrolytes. Soviet Physics Crystallogr. 34 105-107. 

Semiconductors that are used in electrochemical systems often do not meet the ideal conditions on which the Mott-Schottky equation is based. This is particularly true if the semiconductor is an oxide film formed in situ by oxidizing a metal such as Fe or Ti. Such semiconducting films are often amorphous, and contain localized states in the band gap that are spread over a whole range of energies. This may give rise... 

This paper is a report on stable and reproducible current-controlled bistable electrical switching and memory phenomena observed in polycrystalline metal-organic semiconducting films. 

This technique of forming semiconducting films by direct oxidation-reduction is used to grow highly microcrystalline films directly on the copper or silver substrate. These films show a metallic sheen and can be grown to a thickness of 10 ym in a... 

Infrared Reflectance Spectra of Cu-TCNQ Semiconducting Films... 

To investigate the formal charge of TCNQ in the semiconducting films of Cu-TCNQ, the infrared reflectance spectra was recorded at room temperature for crystalline Cu-TCNQ films before and after an external electric field was applied to the sample. 

Changes in the electrical conductivity of a thin-semiconductive film when an eluate is adsorbed on the surface was used by Seiyama and co-workers (45). The response on a ZnO film (20-1000 A) depended upon the nature of the interaction. For electron acceptors, such as 02, a decrease in the conductivity was observed, while for electron donors such as ethyl alcohol and C02, an increase in the conductivity was measured. Temperatures of 200 °C or greater were necessary to avoid slow desorption rates and concomittant loss in resolution. Sensitivities were poor, but the phenomena are worth further scrutiny in hopes of obtaining materials exhibiting stable characteristics as well as... 

A vast number of semiconductor materials have been tested for use as electrodes. Some of these are elucidated in Chapter 28, particularly with respect to their unique properties toward photochemically excited molecules, although most have been used as bulk single crystals and not as polycrystalline films. The two most common semiconducting film electrodes are Sn02 and InOx. 

It was found that 368 exhibits ambipolar activity with appreciable electron (0.12 cm2 V 1 s ) and hole (0.008 cm2 V 1 s-1) mobilities at the substrate growth temperature of 70°C, and 371 shows monopolar n-type activity with a high mobility of 0.32 cm2 V-1 s-1 for semiconducting films deposited at a substrate temperature of 25°C. 373 exhibits stable n-type activity even in the air although the observed electron mobility in the air (0.01 cm2 V-1 s ) is somewhat lower than that under vacuum (0.08 cm2 V-1 s-1). In the case of 368 films grown at 70°C, both n- and p-type mobilities as well as current on-off ratios are enhanced by orders of magnitude compared to films grown at 25°C. 369 exhibits only p-type activity, with no detectable n-type behavior. Hole mobility extracted from the transfer plot is 5 x 10-14 cm2 V-1 s 1 with... 

Water is known to cause electrical instability in a variety of electronic devices. For example, if water is absorbed on the surface of an unencapsulated amorphous silicon TFTs it induces a charge in the semiconducting film that acts as an additional channel layer for conduction, the back-channel effect [56]. The situation for semiconducting polymers is more complex, because water can be absorbed by the bulk of the film and interact directly with the accumulated carrier states. 

Krishnaswamy, R. Kalyanikutty, K. P. Kanishka, B. Sood. A. K. Rao, C. N. R. Nonlinear Viscoelasticity of Ultrathin Nanocrystalline Semiconducting Films of CdS and CuS at Liquid-Liquid Interfaces. J. Colloid Interface Sd., (submitted for publication). 

In the case of the semiconductor photoelectrochemical cell represented in Fig. 48, the efficiency is rather small, in part because the optical absorption of the wide band gap semiconducting films requires UV light excitation, thus making poor use of the available visible NIR radiation of the sunlight. In order to overcome this limitation, the use of dye sensitizers in association with the wide band gap semiconductors is very interesting. A typical scheme of a dye solar cell (DSC) can be seen in Fig. 50. 

The approach to HTSC electrosynthesis described in this section is entirely analogous to that used for the production of semiconductive films such as CujcInj,S(Se)j [205,206]. The thermal treatment of electrodeposited metallic precursors carried out in an H2S(Se) atmosphere in some cases proved more successful than the cathodic codeposition of sulfur or selenium with the metals [207]. There is also an analogy with other combined methods of selenide preparation the sputtering of copper or indium followed by cathodic deposition of selenium [208], and the chemical reaction of selenium with metals. In this case, as in the deposition of incomplete HTSC precursors [189], the use of the deposition mode is much easier. 

The silicon surface can be stabilized using surface modification techniques which are divided into three categories (1) attachment of redox mediator which consumes the holes on the surface (2) attachment of electronically conducting polymer and (3) coating with thin metal or semiconducting films to create a buried semiconductor interface. Combinations of these approaches can also be used to stabilize the sihcon surface. ... 

Figure 1.4 Multiple internal reflections within ultra-thin semiconducting films (penetration depth of light 8 df). The extension of the space charge layer scl depends on the applied potential U and on the electronic layer properties (defect density Nd, dielectric constant e). It is assumed that only electron/hole pairs generated within the scl contribute to the photocurrent [74].

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