Semi-conducting materials

Metal chalcogenide semi-conducting materials have found many applications in opto-electronic, solar cell and photovoltaic devices. Deposition of these materials can be achieved by a variety of techniques of which one of the most... 

GaN as a semi-conducting material for electronics is about to be launched on the market, especially for the use in blue- and UV-emitting LEDs and laser diodes [2]. The material is deposited on crystalline substrates like sapphire using thin-film epitactical techniques. Often, metal-organic chemical vapor deposition (MOCVD) is used. The necessity for such technologies limits the production rate and pushes up costs. 

A Iky nes have been polymerized using ionic and radical initiators, but the polymer molecular weights are low. High molecular weights are obtained by using Ziegler-Natta coordination catalysts (Sec. 8-4d-2) [Chien et al., 1980]. The polymers are of considerable interest in terms of their potential as (semi)conducting materials. 

The main competition to semi-condnctor photovoltaics for producing solar electricity commercially is coming from photoelectrochemical devices based on dye sensitisation. These devices use relatively inexpensive semi-conducting materials such as titanium dioxide, zinc oxide and tin oxide. Gratzel in Switzerland has carried out the seminal work in this area, following on from the initial observation by Fujishima and Honda in Japan that a titanium dioxide electrode could be used to spht water into hydrogen and oxygen. 

Photo-electrochemical systems use semi-conducting materials (like photovoltaics) to split water using only sunlight. 

X-ray analysis reveals a sandwich structure for these semi-conducting materials of formula [M(dmb)2]TCNQ TCNQ° (N= 1, 1.5), the polymeric chains of M(dmb)2 + are separated by layers of TCNQ- and neutral TCNQ (i.e., mixed-valence TCNQ- layers). The latter layer is responsible for the conductivity. Since TCNQ is an electron acceptor, electron transfer from the polymer to the mixed valence TCNQ layer is also possible from the Cu(I) center to the TCNQ- TCNQ° layer. This photoinduced electron transfer from... 

Quantitative determinations have recently focused on high-purity materials [252] trace noble metals (Pd, Pt and Th) in automobile catalysts [253] and non-conducting [254,255] and semi-conducting materials [256]. The determination of "Ca in the presence of "Ar... 

The HOMO and LUMO energies were calculated with the use of Eq. (la) and (lb) [16], The electrochemical band gap values Ef were determined from the difference between HOMO and LUMO levels and found to be 2.25 eV, which is in the range of semi-conducting materials. 

The shield has a strippable outer layer formed by a coextrusion of 20% strip material and 50% standard semi-conductive material. 

The continuous dynode is a leaded glass funnel coated on the inside with a semi-conductive material. 

Both 33 and 61 form semi-conducting materials when the counter-anion is exchanged with TCNQ followed by a doping with neutral TCNQ . The materials exhibit formula of the type [M(dmb)j]TCNQ xTCNQ° where M = Cu, Ag,... 

It was recently shown that doping poly(pPIN) with iodine produces a semi-conductive material, with conductivities of about 8 X 10 S cm typical of non-conjugated doped polymers [99]. This material also showed a large quadratic electro-optic effect which would make it useful for non-linear optics applications [100]. 

The use of infrared spectrometry for quantitive analysis became possible only in the 1980s, when affordable and user-friendly benchtop Fourier-transform spectrometers became available. The sensitivity of the FT-IR spectroscopy was, however, insufficient to meet the requirements of the immunoassay. To address this problem, an instrument equipped with a liquid nitrogen-cooled detector made from a semi-conducting material, for example MCT (mercury-cadmium-telluride) or InSb (indium antimonide), was used to increase sensitivity by a factor of 20 compared with the thermal detector DTGS found in standard FT-IR machines. Use of a light-pipe cell with a long optical path (20 mm) for a... 

Semi-conductive materials may be produced by addition of conventional carbon blacks. Resistivity is lowest for those grades with the highest structure and highest surface areas. Non-black products generally rely on the use of antistatic additives, which reduce the surface resistivity of the product, since most non-black fillers are insulating in nature. 

The introduction of metal atoms into a pdymer, or the formaticm of a polymer through metal centres fequently provides semi-conducting materials. Unfortunately, and equally frequently, the polymers are insduble, infusable and thus intractable materuls. It is beyond the limited space available to discuss the conductance of the large number of known n tallo-organic pdymers. For this reason a selective approach is adopted here mth the aim to illustrate, and whenever possible, to present weU characterized system or ernes vriiich have outstanding electrical properties. 

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