Explanations of inconsistencies in capacitance–voltage profiles of normal and inverted heterostructures

The carrier distributions, obtained from capacitance–voltage measurements on semiconductor heterojunctions, are widely different, depending on whether the Schottky barrier is on the higher band gap semiconductor or on the lower band gap semiconductor. The actual carrier distributions as calculated in both cases are quite dissimilar from the measured distributions. Explanations for such observations have been sought through rigorous studies based on self-consistent solutions of Schrödinger and Poisson equations applied to the widely used GaAs/AlGaAs heterojunctions. It emerges that the nature of the carrier distributions is mostly dependent on the effects of the Debye smearing on the two dimensional and three dimensional components of the capacitances at the heterostructures. The applied electric field, necessary for measurements does not have a significant effect on the carrier distribution.     

On first integrals of second-order ordinary differential equations

Here we discuss first integrals of a particular representation associated with second-order ordinary differential equations. The linearization problem is a particular case of the equivalence problem together with a number of related problems such as defining a class of transformations, finding invariants of these transformations, obtaining the equivalence criteria, and constructing the transformation. The relationship between the integral form, the associated equations, equivalence transformations, and some examples are considered as part of the discussion illustrating some important aspects and properties.     

Green chemistry and the textile industry

In contrast to non-sustainable, non-renewable fossil-fuel-based conventional chemical processes, so-called green reactions are sustainable, highly-efficient (fewer steps, fewer resources, less waste) and stable under ambient conditions and much more eco-friendly (achieved by the use of non-hazardous solvents and less-hazardous, minimized waste). They are assessed by 12 principles established by Anastas and Warner [Green Chemistry: Theory and Practice, Oxford University Press, New York, 1998]. Recently steps have been taken to make textile materials and processing more environmentally friendly (or ‘greener’), including fibre production, dyes and auxiliaries, solvents, optimized and efficient processing with recycling of water and chemicals, bio-processing, the elimination of hazardous chemicals and the recycling of textile materials, and whilst it is acknowledged that mechanical aspects of textile processing also contribute to achievement of sustainability, this review focuses on the chemistry deployed.