Arsenide density

The first semiconductor lasers, fabricated from gallium arsenide material, were formed from a simple junction (called a homojunction because the composition of the material was the same on each side of the junction) between the type and n-ty e materials. Those devices required high electrical current density, which produced damage ia the region of the junction so that the lasers were short-Hved. To reduce this problem, a heterojunction stmcture was developed. This junction is formed by growing a number of layers of different composition epitaxially. This is shown ia Figure 12. There are a number of layers of material having different composition is this ternary alloy system, which may be denoted Al Ga his notation, x is a composition... 

In accordance with the electropositive nature of the bridgehead atoms, all di(pyridyl) substituted anions behave like amides with the electron density accumulated at the ring nitrogen atoms rather than carbanions, phosphides or arsenides. The divalent bridging atoms (N, P, As) in the related complexes should in principle be able to coordinate either one or even two further Lewis acidic metals to form heterobimetallic derivatives. According to the mesomeric structures, (Scheme 7), it can act as a 2e- or even a 4e-donor. However, theoretical calculations, supported by experiments, have shown that while in the amides (E = N) the amido nitrogen does function as... 

Barium Arsenide, Ba3As2.—By passing arsine over barium oxide at red heat Soubeiran 4 obtained a mixture of arsenide and arsenite. Lebeau 6 prepared the pure arsenide by reduction of barium arsenate with carbon in an electric furnace. Barium arsenide is very similar in properties to the arsenides of calcium and strontium it is slightly darker in colour, more readily fusible and more reactive chemically. Its density at 15° C. is 4-1. It burns spontaneously in fluorine, chlorine or bromine vapour. In oxygen it burns at about 300° C. and in sulphur vapour at dull red heat. 

Bismuth Arsenides.—When bismuth and arsenic are melted together there is no evidence of chemical combination. The two elements are only slightly miscible in the molten state 7 and separate completely on solidification if an open vessel is used, but according to Heike 8 they are perfectly miscible if melted in a sealed tube. Descamps 9 melted a mixture of bismuth and excess of arsenic under fused boric oxide, keeping the temperature as low as possible, and obtained a product of density 8-45 and approximate composition Bi3As4, but it is doubtful whether this was a definite compound. 

Cadmium Arsenides.—The freezing point, density and atomic volume curves indicate the existence of two arsenides, Cd3As2and CdAs2.n The freezing point curve was obtained by cooling mixtures of the elements melted under fused alkali chloride no mixed crystals were observed. Two other arsenides have been described Cd6As, said to... 

Di-cobalt Tri-arsenide, Co2As3, is formed when cobalt monarsenide is heated at 400° to 600° C., or when cobalt is heated with arsenic trichloride at the same temperature. According to Beutell and Lorenz,8 it is formed when cobalt is heated in arsenic vapour at 345° to 365° C., but it slowly undergoes decomposition below 400° C. to form the di-arsenide, CoAs2. It also decomposes when heated above 600° C. The density is 7-35 at 0° C. 

The density of CusAs is 6-7 to 7-7 the density calculated from crystallographic data 5 is 8-22. The hardness is 3-0 to 3-3 on Mohs scale. The specific heat is 6 0-0919. On heating, sublimation occurs at 345° to 370° C.7 The arsenide decomposes on strong heating.8 It is completely reduced when heated in hydrogen.9 It is stable towards hydrochloric acid, but is attacked by nitric acid.10... 

The arsenide Cu5As.2 has been prepared by passing a current of carbon dioxide and arsenic vapour over finely divided copper heated to the temperature of boiling sulphur 11 by the action of copper on arsenic trichloride or on arsenic dissolved in hydrochloric acid 12 and by the action of cuprous chloride on arsenic. Lustrous regular crystals of density 7-56 are obtained. These tarnish on exposure to air. When heated it loses arsenic and yields Cu3As, which at a higher temperature also decomposes. Cu5As2 dissolves in nitric acid. It is readily attacked by chlorine or bromine.13... 

It forms silver-white, rhombic crystals,7 of density 7-83, and melting point 1020° C. according to Hilpert and Dieckmann8 or 1031° C. according to Friedrich.9 It is non-magnetic. Steel-grey crystals of the arsenide of density 7-94 have been found associated with tin sulphide in the hearth of an old tin smelting furnace in Cornwall.10... 

The product, of density 7-22, which results when iron is heated in arsenic vapour at 395° to 415° C.11 agrees in composition with the formula Fe2As3. The existence of such an arsenide has not been confirmed, however, although some forms of lollingite approach this composition. 

Molybdenum Arsenide, MoAs2, is formed10 by heating powdered molybdenum for 36 hours with arsenic at 570° C., the excess of arsenic then being removed by sublimation. It is a black powder of density... 

Niobium Arsenide, NbAs2, has been prepared 6 by heating the elements together in a sealed tube at 500° C. The product, the composition of which corresponded more exactly with NbAs jg, had density 7-28 at 25° C. 

Arsine is formed also during the electrolysis of concentrated aqueous solutions of sodium acetate made acid with acetic acid and using an arsenic cathode. At constant potential difference the yield rises with increasing current density, but never attains a high value, and the electrolytic method is greatly inferior as a mode of preparation of arsine to the usual method of acting upon metallic arsenides with dilute acids. 

For high electron densities n, scattering at the pure plasmon is obtained, whereas for relatively low values of n coupled plasmon-phonon states are observed. In Fig. 8 the dispersion curves for gallium arsenide measured by Mooradian et al. 

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