Epitaxial technological applications

Thin-film XRD is important in many technological applications, because of its abilities to accurately determine strains and to uniquely identify the presence and composition of phases. In semiconduaor and optical materials applications, XRD is used to measure the strain state, orientation, and defects in epitaxial thin films, which affect the film s electronic and optical properties. For magnetic thin films, it is used to identify phases and to determine preferred orientations, since these can determine magnetic properties. In metallurgical applications, it is used to determine strains in surfiice layers and thin films, which influence their mechanical properties. For packaging materials, XRD can be used to investigate diffusion and phase formation at interfaces... 

Thin semiconductor films (and other nanostructured materials) are widely used in many applications and, especially, in microelectronics. Current technological trends toward ultimate miniaturization of microelectronic devices require films as thin as less than 5 nm, that is, containing only several atomic layers [1]. Experimental deposition methods have been described in detail in recent reviews [2-7]. Common thin-film deposition techniques are subdivided into two main categories physical deposition and chemical deposition. Physical deposition techniques, such as evaporation, molecular beam epitaxy, or sputtering, involve no chemical surface reactions. In chemical deposition techniques, such as chemical vapor deposition (CVD) and its most important version, atomic layer deposition (ALD), chemical precursors are used to obtain chemical substances or their components deposited on the surface. 

Electrosynthesis of semiconductors such as epitaxial GaAs and other semiconductor materials with high value would be attractive candidates for improved processing by electrochemical techniques. Materials such as HgCdTe (IR sensors), CdTe, CdS, and CdSe (photoelectrochemical and photovoltaic devices) would enjoy much wider application if less costly production could be achieved. Current electrochemical technology for such applications is embryonic, and most semiconductor materials now made with these techniques are inferior in properties compared to those available from other preparation methods. An improvement that is most needed is the ability to deposit single crystals of macroscopic size and of controlled expitaxy. 

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