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The physics of the growth mechanisms, characterization of epitaxial structures and device properties of GaAs and other compound semiconductors on Si are reviewed in this paper. The nontrivial problems associated with the heteroepitaxial growth schemes and methods that are generally applied in the growth of lattice mismatched and polar on nonpolar material systems are described in detail. The properties of devices fabricated in GaAs and other compound semiconductors grown on Si substrates are discussed in comparison with those grown on GaAs substrates. The advantages of GaAs and other compound semiconductors on Si, namely, the low cost, superior mechanical strength, and thermal conductivity, increased wafer area, and the possibility of monolithic integration of electronic and optical devices are also discussed.

The possibility induction of light emission from silicon, an indirect bandgap material in which radiative transitions are unlikely, raises several interesting and technologically important possibilities, especially the fabrication of a truly integrated optoelectronic microchip. In this article, the natural considerations that constrain silicon from emitting light efficiently are examined, as are several engineered solutions to this limitation. These include intrinsic and alloy-induced luminescence; radiatively active impurities; quantum-confined structures, including zone folding and the recent developments in porous silicon; and a hybrid approach, the integration of direct bandgap materials onto silicon.

A new class of corrosion inhibitors, namely, polyamino-benzoquinone (PAQ) has been synthesized and its inhibiting action on the corrosion of mild steel in 1N H2SO, and 1N HC1 has been investigated by various corrosion monitoring techniques. A preliminary screening of the inhibition efficiency of the polymer was carried out by self corrosion studies. PAQ is found to behave better in 1N H2SO, than 1N HC1. Potentiodynamic polarization studies clearly reveal the fact that PAQ is a mixed-type inhibitor. PAQ is able to reduce considerably the permeation current through the steel surface in both the acids. Changes in impedance parameters (R~t and C~) are indicative of adsorption of PAQ on the metal surface leading to the formation of a protective film which grows with increasing exposure time. The adsorption of this polymer is also found to obey Temkin's adsorption isotherm in both acids thereby indicating that the main process of inhibition is by adsorption. UV spectral studies were also carried out to establish the actual mechanism of inhibition of corrosion.

Alternatives to platinum-based catalysts are required to sustainably produce hydrogen from water at low overpotentials. Progress has been made in utilizing tungsten carbide-based catalysts, however, their performance is currently limited by the density and reactivity of active sites, and insufficient stability in acidic electrolytes. We report highly active graphene nanoplatelet-supported tungsten carbide-nitride nanocomposites prepared via an in situ solid-state approach. This nanocomposite catalyzes the hydrogen evolution reaction with very low overpotential and is stable operating for at least 300 h in harsh acidic conditions. The synthetic approach offers a great advantage in terms of structural control and kinetics improvement.