Chemical evaporation deposit technologies

Some of the technological areas in which means and methods of electrochemical deposition constitute an essential component are all aspects of electronics—macro and micro, optics, optoelectronics, and sensors of most types, to name only a few. In addition, a number of key industries, such as the automobile industry, adopt the methods even when other methods, such as evaporation, sputtering, chemical vapor deposition (CVD), and the like, are an option. That is so for reasons of economy and/or convenience. 

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. 

Many technologies exist for the deposition of thin films (1,2). Usually such coatings are applied by evaporative deposition, chemical vapor deposition, or sputtering. However, exposure of DT-filled glass microspheres to most of these processes would cause excessive heating of the glass shell allowing the DT gas to escape. 

In thin-film technology (layer thickness <1 pm), a microporous platinum layer is deposited on the already fired ceramic by thermal evaporation, sputtering, chemical vapor deposition, or electrolytic or electroless deposition. The microporosity of the thin electrode provides sufficient access of the exhaust gas to the three-phase boundary. 

The technology of growing carbon nanotubes from the vapor phase dates back to 1991 when they were first found [11] in arc discharge experiments. Nanotubes can be obtained by chemical vapor deposition, laser evaporation, arc discharge, and carbon ion bombardment [62], Addition of particulate metal catalysts creates a more controlled growth habitat and helps growth of whiskers with greatly enhanced dimensional uniformity. 

Microfabrication has been the topic of a recent review in which thin-film (<1 pm, based on vacuum evaporation, sputtering or chemical vapor deposition) and thick-film (>10pm, based on screen printing or lamination) technologies are described for the mass production of potentiometric sensors and sensor arrays [80]. Current challenges include the cost of fabrication, especially for thin-film devices, the control of physical dimensions of the sensing elements, the incorporation of liquid reservoirs, and the stability of the integrated reference electrodes. 

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