A theoretical model of the grain boundary potential is developed by considering the presence of deep level impurities and a generalized interface state model. It is seen that the grain boundary potential is maximum at a certain value of the deep level density. This happens when the type of deep level impurities is opposite to that of shallow impurities. For similar types of deep and shallow impurities, the potential barrier remains constant over a wide range of impurity concentration for lower values of activation energy, but decreases considerably when the activation energy is increased. Copyright © 1994 WILEY‐VCH Verlag GmbH & Co. KGaA

PROJNAN CHATTOPADHYAY

Electronic Science

D P HALDAR

S CHAKRABARTI

M RAY

University of Calcutta (informally known as Calcutta University or CU) is a collegiate public state university located in Kolkata, West Bengal, India.&nbsp;Within India it is recognized as a &quot;Five-Star University&quot; and accredited &quot;A&quot; Grade by National Assessment and Accreditation Council.

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The University of Calcutta has secured the Fifth position among the Universities of India in the prestigious &quot;Indian University Ranking 2019&quot; list, released by the NIRF of the Ministry of Human Resource Development, Government of India.

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It was established on 24 January 1857, and was one of the first institutions in Asia to be established as a multidisciplinary and Western-style university. Its alumni and faculty include several heads of state, heads of government, social reformers, prominent artists, only academy award winner and Dirac medal winner in India, many Fellows of the Royal Society and five Nobel laureates as of 2019 which is highest in South Asia.

University Of Calcutta

physica status solidi (a)

The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material. © 2013 AIP Publishing LLC.

Journal	physica status solidi (a)
Publisher	-
ISSN	0031-8965
Open Access	No