Epitaxial, surface nitride

No epitaxy could be obtained by reaction of the metal films with reactive gas for short reactions times. This is understandable as the carburization and nitridation reactions progress from the surface of the metal films to the substrate and occur with a change in crystal structure of the film (for instance bcc to hex). So even if the starting metal film is epitaxial, the final carbide or nitride compound could be polycrystalline. For high temperatures and for long time treatments (>15 h), however, perfect epitaxial Y Mo2N films could be obtained on MgO (100).17 In this last case, the crystalline state of the precursor metal film had no effect on the final parallel orientation of the nitride. 

Nitride-based photoconductive detectors consist of a single undoped or lightly doped epitaxial layer with interdigitated electrodes deposited and patterned on the top surface. Optical absorption in the semiconductor layer produces electron-hole pairs which can be swept out by an applied bias voltage to detect a measurable current proportional to the incident photon flux. A summary of published photoconductive detector performance is shown in TABLE 1. 

S. Koizumi, T. Murakami, T. Inuzuka, and K. Suzuki, Epitaxial growth of diamond thin films on cubic boron nitride (111) surfaces by DC plasma chemical vapor deposition, Appl. Pl s. Lett, 57(6) 563-565 (1990)... 

Before illustrating actual examples of electrochemical growth of epitaxial organic films and their visualization by AEM, a brief description of the AFM method in this context is warranted. An atomic force microscope operates much like a surface profilometer. A small tip, usually of silicon or silicon nitride, at the end of a silicon cantilever is moved in small increments with piezoelectric actuators over the sample (or the sample is moved under... 

In this process, the substrate is placed inside a reactor supplied by different gases [21], The principle of the process is that a chemical reaction takes place between the source gases producing a solid material which condenses on all surfaces inside the reactor. CVD is widely used in the semiconductor industry to deposit various materials such as polycrystalline, amorphous, and epitaxial silicon, carbon fiber, filaments, carbon nanotubes, Si02, silicon-germanium, tungsten, silicon nitride, silicon oxynitride, titanium nitride, and various high-k dielectrics. 

H. Aida, S.-W. Kim, K. Sunakawa, N. Aota, K. Koyama, M. Takeuchi, T. Suzuki, Ill-Nitride epitaxy on atomicahy controUed surface of sapphire substrate with slight misorientation, Jpn. J. Appl. Phys. 51 (2012) 025502. 

Chemical Vapor Deposition. Chemical vapor deposition (CVD) is a process where by the heat-induced decomposition of gases form different semiconductor layers such as silicon dioxide, silicon nitride, polysilicon, and gallium arsenide on the surface of the wafer. When the layer formed is a continuation of the crystalline structure of the substrate, the process used is epitaxial growth. Other, non-epitaxial forms of CVD involve the deposition of layers that are a different structure than the substrate. Table 5 outlines typical chemistries associated with CVD. 

As a conclusion of this section, let us characterise briefly the electronic structure investigations of one more group of materials whose properties are greatly dependent on surface effects. These are thin films made from refractory carbides and nitrides. These films find applications in microelectronics, optics and as coatings for cutting tools and other complicated multilayered materials. Such films can be produced by different methods, such as thermal deposition or laser evaporation, (Morchan, 1982), molecular-beam epitaxy and cathode sputtering (Herman, 1982 Cho, 1983), plasma condensation in vacuum with ionic bombardment of the substrate surface (Dorodnov and Potrosov, 1981), chemical vapour-phase deposition (Anikeev, 1977 Anikin, Anikeev and Zolotaryova, 1979), etc. 

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