We continue to investigate possible signatures of a pre-inflationary anisotropic phase in two-point and three point correlation functions of the curvature perturbation for high-momentum modes which exit the horizon well after isotropization. The late time dynamics of these modes is characterized by a non-Bunch Davies vacuum state which encodes all the information about initial anisotropy in the background space-time. We observe that, unlike the non-planar momenta, there exist regimes of planar momenta for which scale invariance of the power spectrum is strongly broken. This regime of planar momenta gives rise to enhanced non-Gaussianity in certain squeezed triangle configurations, although the enhancement of the f N L parameter is limited by the breakdown of linear perturbation theory at "exact planarity". Finally, we demonstrate that for the range of planar modes for which scale invariance of the power spectrum is preserved, non-Gaussianity in the curvature perturbation spectrum is naturally constrained to be extremely small.

Photothermal Deflection Spectroscopy (PDS) technique was used to study undoped and copper (Cu) doped cadmium sulphide (CdS) thin films. Variation in grain size and lattice strain due to Cu doping were analysed using X‐ray diffraction (XRD). Changes in mobility of carriers in CdS with Cu concentration was studied using PDS technique for the first time and results are compared with the earlier ones. Thickness of Cu diffused region in CdS was also calculated and compared with results from X‐Ray Photoelectron Spectroscopy (XPS) and Ellipsometry. Results from PDS technique are found to be agreeing with those from other experiments. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Trap levels in n- and p-type spray pyrolysed CdS thin films were analysed using thermally stimulated current (TSC) and dark-conductivity measurements. TSC measurements of the n-type sample revealed the presence of only one peak under light excitation for a short period due to mobility of sulphur vacancies, but longer excitation could give evidence of one more level which was due to a complex of cadmium and sulphur vacancies. TSC spectra of the p-type sample indicated the presence of two levels of comparable cross section irrespective of light excitation time, which correspond to mobility of the sulphur vacancy and copper impurity. TSC measurements on air annealed n-type samples indicated the presence of a level due to the sulphur vacancies and another level may be due to chemisorbed oxygen. However vacuum annealed samples showed results similar to those of as-prepared n-type samples. The dark-conductivity measurements of these samples were found to be in good agreement with the TSC measurement results.

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