Epitaxial NiO layers have been grown on GaN templates with the out-of-plane and in-plane epitaxial relationship of [111]NiO ǁ [0001]GaN and [-110]NiO ǁ [-12-10]GaN, respectively. The epitaxial NiO layer is found to have two domain structures oriented along the [111] direction with an in-plane rotation of ∼60° with respect to each other. A type-II band alignment with valence and conduction band offset values of 1.4 ± 0.1 eV and 1.9 ± 0.1 eV, respectively, has been obtained from photoemission spectroscopy. The determined band offset values and band alignment are helpful to determine charge transport and recombination mechanisms in optoelectronic devices based on the NiO/GaN heterojunction.

The optical gap of Ni1−xCoxO solid solutions neither varies linearly with Co composition nor shows any bowing in the complete composition range. The nature of this variation of the gap is governed by the position of conduction band edge.

A study has been carried out on the build-up of burn up wave in neutron absorbing and diffusive media. New parameters, i.e., transient length and transient time elapsing in establishing the steady burn up wave, have been introduced. The wave characteristics are expressed in terms of these new parameters and Full Width at Half Maxima (FWHM) and Full Width at 1 % of Maximum (FW1M). These characterization parameters would be useful in understanding the neutron burn up wave development and their approach to the equilibrium (steady) state.