Metal chalcogenide semiconductors

Froment M, Lincot D (1995) Phase formation processes in solution at the atomic level Metal chalcogenide semiconductors. Electrochim Acta 40 1293-1303... 

The arrangement of zinc and sulfur atoms in the Zn4S core is similar to the observed Zn40. Theoretical calculations demonstrated that the compound is a poor model of extended metal chalcogenide semiconductors (ZnS). Octanuclear zinc compounds have also been structurally characterized with this core. In the presence of an alkylammonium cation, a sulfide containing octanuclear zinc species was formed [BzEt3N]2[Zng(S)(SBz)i6].126 The complexes with benzylthiolate... 

The basic recipe for producing Q-state metal chalcogenide semiconductors involves the exposure of metal ions to a source of the chalcogenide in the presence of some stabilizing medium (7 and ref. therein). This is depicted in Eq. (1) for the specific case of divalent metal ions reacting with the sulfide ion ... 

In considering photoactivity on metal oxide and metal chalcogenide semiconductor surfaces, we must be aware that multiple sites for adsorption are accessible. On titanium dioxide, for example, there exist acidic, basic, and surface defect sites for adsorption. Adsorption isotherms will differ at each site, so that selective activation on a particular material may indeed depend on photocatalyst preparation, since this may in turn Influence the relative fraction of each type of adsorption site. The number of basic sites can be determined by titration but the total number of acidic sites is difficult to establish because of competitive water adsorption. A rough ratio of acidic to basic binding sites on several commercially available titania samples has been shown by combined surface ir and chemical titration methods to be about 2.4, with a combined acid/base site concentration of about 0.5 mmol/g . 

The C/fb for n- and p-Si5) and that for metal chalcogenides such as n-CdS, n-CdSe and CdTe4,6) do not obey the above law, remaining nearly constant in a range of pH lower than about 6 for Si and about 10 for n-CdS. This is most probably because the semiconductor surface has no OH group in this pH range. It shoud be mentioned that the U for the metal chalcogenide semiconductors... 

Most common metal oxide and metal chalcogenide semiconductors have valence-band edges that lie positive of the oxidation potentials of most organic functional groups, and thermodynamics will thus favor photocatalytic oxidation. For efficient processes to take place, an easily oxidizable donor is required, but a whole range of substrates have been shown to be useful for this application. For example, a Japanese group has shown that this purpose is served not only by pure compounds, but even by wastes such as polyvinyl chloride, algae, protein, dead insects, and animal excrement, which function as electron sources [104]. Thus, synthetic utility is attained only if this wide reactivity is controlled. In practice, selectivity is best controlled by the adsorption and oxidation potential effects [105],... 

This chapter covers the most recent advances in the synthesis of metal chalcogenide semiconductor nanocrystals and their chemical processing and assembly into ordered entities. In addition the application of this important class of materials in the broad fields of electronics and biomedicine is also described. 

Turk T, Resch U, Fox M A, and Vogler A, (1992) Cadmium Benzenethiolate Clusters of Various Size Molecular Models for Metal Chalcogenide Semiconductors. J Phys Chem 96 3818 Fischer Ch-H and Henglein A, (1989) Photochemistry of Colloidal Semiconductors. 31. Preparation and Photolysis of CdS Sols in Organic Solvents. J Phys Chem 93 5578... 

Nanocrystals of metal chalcogenide semiconductors immobilized into polymeric matrices exhibit Imninescent properties. This is illustrated by nanocrystals of CdSe, >i. >2 cdS-Ag, >3 ZnS, and ZnS-CuS. Composites based on ZnS-CuS,... 

Among the compound semiconductor materials, metal chalcogenide semiconductor nanocrystals have been extensively studied and widely used for linear and nonlinear optical devices and photovoltaic solar cells. The use of these materials as nanocrystals for large-scale fabrication of films with applications in solar energy conversion and other optoelectronic applications is an emerging and important area in materials science. Compared to the... 

Low-temperature solvents are not readily available for many refractory compounds and semiconductors of interest. Molten salt electrolysis is utilized in many instances, as for the synthesis and deposition of elemental materials such as Al, Si, and also a wide variety of binary and ternary compounds such as borides, carbides, silicides, phosphides, arsenides, and sulfides, and the semiconductors SiC, GaAs, and GaP and InP [16], A few available reports regarding the metal chalcogenides examined in this chapter will be addressed in the respective sections. Let us note here that halide fluxes provide a good reaction medium for the crystal growth of refractory compounds. A wide spectrum of alkali and alkaline earth halides provides... 

The wide use of p-block and early transition metal chalcogenide materials for electronics applications (semiconductors, semi-metals, battery materials, etc.) has resulted in a large amount of work concerned with CVD using mixtures of metal halides and chalcogenoethers as dual source precursors and preformed complexes as single sources.166... 

Abstract This review highlights how molecular Zintl compounds can be used to create new materials with a variety of novel opto-electronic and gas absorption properties. The generality of the synthetic approach described in this chapter on coupling various group-IV Zintl clusters provides an important tool for the design of new kinds of periodically ordered mesoporous semiconductors with tunable chemical and physical properties. We illustrate the potential of Zintl compounds to produce highly porous non-oxidic semiconductors, and we also cover the recent advances in the development of mesoporous elemental-based, metal-chalcogenide, and binary intermetallic alloy materials. The principles behind this approach and some perspectives for application of the derived materials are discussed. 

So far, the synthesis of mesoporous metal chalcogenides remains an open challenge but progress is being made. A few examples have been reported, including 11-VI group-type semiconductors such as CdS [68, 69], ZnS [70], and CdTe [17]. 

Studies include wet-cell photoelectrochemical measurements (42,60,72,90), STM measurements on single MS particles in thin films (55,56,81), and conductivity measurements of metal chalcogenides in LB films (20,21,23). Many such studies are driven by the search for cheaper methods and materials for the fabrication of semiconductors suitable for photoelectrochemical devices. Moreover, the ability to tune optical properties via the Q-state effect and the versatility of LB fabrication make the LB films an attractive medium for semiconductor production. The photo-... 

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