Plasma deposited films, electronic

Optical and electrical properties of plasma deposited films, sometimes unique indeed, as well as the easy of their deposition, at low temperature and low cost, on inexpensive substrates of almost any size and shape, render these materials very attractive for optoelectronic applications. The possibility to tailor optical parameters, such as refractive index and extinction coefficient, and what is particularly important - the ability to adjust parameters of the electronic structure, such as transport p, optical gap, density of localized states, etc., recommend these plasma films as active photoelectric elements, e.g. for solar cells and water splitting cells. 

Despite such limitations, plasma-deposited a-C(N) H films were found to be used in a number of applications. The stress reduction induced by nitrogen incorporation [12] and consequent adhesion improvement, allowed the development of a-C(N) H antireflective coatings for Ge-based infrared detectors [13]. It was also found that N can electronically dope a-C H films, and can strongly decrease the defect density, which gives prospects on its use as a semiconductor material [14]. Nitrogen incorporation was also found to decrease the threshold electric field in electron-field emission process [15], making possible the use of a-C(N) H films as an overcoat on emission tips in flat-panel display devices [16]. 

The nature of the surface of organogermanium films, obtained by magnetically enhanced rf-plasma deposition from tetraethylgermane, was examined by ESCA (electron spectroscopy for chemical analysis) and FTIR methods56. 

In summary, the importance of ion-induced secondary-electron emission in plasma environments is demonstrated by, among other things, the fact that it produces a substantial fraction of the ions, generates significant heating of surrounding surfaces, and modifies the properties of deposited films. 

X-ray photoelectron spectroscopy (XPS) was used for elemental analysis of plasma-deposited polymer films. The photoelectron spectrometer (Physical Electronics, Model 548) was used with an X-ray source of Mg Ka (1253.6 eV). Fourier transform infrared (FTIR) spectra of plasma polymers deposited on the steel substrate were recorded on a Perkin-Elmer Model 1750 spectrophotometer using the attenuated total reflection (ATR) technique. The silane plasma-deposited steel sample was cut to match precisely the surface of the reflection element, which was a high refractive index KRS-5 crystal. 

Another experiment was done by exposing the deposited films to a hydrogen plasma for posthydrogenation. It did not bring any substantial improvement of the electronic properties. This can be associated with the dense nature of the material and the resulting slow diffusion of hydrogen into the bulk. The pos-... 

A second method of surface smoothing is to deposit a thick layer of SiOj and then a thin the layer by RIE or sputter etching. Because the sputter yield of the SiOj is greatest at an angle of 45°, the corners in the SiOj film etch quicker than the rest of the film and are therefore rounded by the etch process. With some deposition systems, for example, biased electron cyclotron resonance (ECR) plasma deposition, it is possible to deposit and etch concurrently, yielding a one-step process with a reduced deposition rate. ... 

The morphology of the plasma polymerized films has been examined by electron microscopy by a number of workers ( 3,, 48). Figure 12 shows the replica electron micrograph of plasma polymerized ethylene deposited on chromium substrate at several gas pressures (46). The presence of powder particles is clearly evidenced in Figures 12a-c. The size and density of the powdery products decrease with increasing pressure until at a pressure of 3 torr when the polymer is mainly film and contains very few particles. 

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