Newer semiconductor materials

The other potential semiconductor detector materials have a larger band gap than germanium and consequently would have the advantage of room temperature operation assuming that their other properties were satisfactory. Of these, only cadmium telluride, cadmium zinc telluride (CZT) and mercuric iodide have found their way into 

The approximate energy range over which usable detection efficiency can be expected. The actual range will depend upon the thickness and material of the detector window. 

Thallium bromide is a material showing some promise. Its high density and high band gap make it an attractive proposition. Working devices have been constructed 

Gallium arsenide is a material with some theoretical promise as a semiconductor detector which although abandoned for the present could ultimately have a place in gamma spectrometry due to improvements in the technology of manufacture of the material for the electronics industry. The other materials listed in Table 3.1 have all been considered as potential materials for gamma spectrometry, but discarded for one reason or another. In practice, the material almost universally used for gamma-ray spectrometry is germanium and we shall not deal in detail with other types of detector, with the exception of scintillation detectors, which will be discussed separately in Chapter 10. 

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Recently, Mg and Be compounds have been used in alloys with ZnSe to make blue and green semiconductor lasers. Bulk growth by zone melting and molecular beam epitaxy (MBE) ° has been used. In these cases, good semiconductor material has been obtained dilution with group IIB compounds may be responsible. However, growth of pure MgS in very thin films on ZnSe has been achieved the epitaxial orientation effect of the substrate results in a tetrahedral cubic (sphalerite or zinc-blende) structure. It is likely that improvements in these materials will take place at a rapid rate, driven in part by applications and in part by newer, cleaner synthetic methods. 

Among the newer uses of phosphoric acid are as a metal cleaner in printed circuit board manufacture, and as a metal etchant in the production of semiconductor materials. A 1% solution of hexafluorophosphoric acid, HPFg, can be used to clean aluminium, prior to anodising [23]. 

SIMS is one of the most powerful surface and microanalytical techniques for materials characterization. It is primarily used in the analysis of semiconductors, as well as for metallurgical, and geological materials. The advent of a growing number of standards for SIMS has gready enhanced the quantitative accuracy and reliability of the technique in these areas. Future development is expected in the area of small spot analysis, implementation of post-sputtering ionization to SIMS (see the articles on SALI and SNMS), and newer areas of application, such as ceramics, polymers, and biological and pharmaceutical materials. 

Newer microcalorimeters have been produced by modem semiconductor microfabrication techniques to produce an extremely small addenda heat capacity, thus allowing submicro-Joule precision for ultra-thin film heat capacity measurements [139], which can be applied to a wide range of materials. Over... 

Unfortunately, most of the low band gap materials studied so far have been found to undergo such corrosions. Therefore, there is a need to develop newer materials for developing a photoelectrochemically stable semiconductor. 

Many intensive scientific investigations are focused on the preparation and characterisation of new polymeric organic films. Many newer surface science techniques, designed and developed for semiconductors and dielectric materials, address specific details about the structure and morphology of these organic films. 

Gallium arsenide is one of the newer materials used to make semiconductor chips for use in supercomputers. Its composition is 48.2% Ga and 51.8% As. What is the empirical formula ... 

It is difficult to present all applications of EIS some applications (such as those to solid materials and PEM fuel cells, corrosion and passivity, batteries see Sect. 1.3) may be found in available books. As examples, Mott-Schottky plots obtained for semiconductors, the impedance of coating and paints, and electrocatalysis of hydrogen adsorption, absorption and evolution were presented as they are well known in the electrochemical literature. Additionally, newer and developing applications such as the impedance of self-assembled monolayers, biological bilayers, and biosensors were also shown. 

Two Classes of Chemically Sensitive Interface. It is our ultimate goal to select materials from widely different chemical classes— metals, metal oxides, semiconductors, organic polymers, coordination complexes, and organized thin films— to form a chemically sparate array. Because of our fairly extensive experience with metals, oxides, and ordinary polymers, we are currently focusing our efforts on two newer classes of materials, self-assembled monolayers and plasma-grafted polymer films. 

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