• Volume 2, Issue 5

      December 1980,   pages  1-380

    • Preface

      C N R Rao S C Agarwal

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    • Amorphous semiconducting Si:H

      H Fritzsche

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      Glow discharge decomposition of silane produces amorphous semiconductors which can be doped to be eithern-type orp-type. Since these amorphous silicon films contain between 10–20 atomic per cent hydrogen, the density of undesired defects and localized gap states is very low. As a consequence of the high semiconductor quality of the a-Si:H films, space charge layers adjacent to the surface and substrate interface play an important role in the transport properties. We describe the effect of illumination, thermal treatments and surface layers on the conductance and discuss some difficulties in interpreting the field effect in terms of the bulk density of gap states. The preparation and some characteristic properties of the silicon-hydrogen alloys are described.

    • Amorphous hydrogenated silicon films prepared from a glowdischarge

      S Guha

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      From a detailed study of electrical and optical properties of amorphous hydrogenated silicon prepared from a mixture of 10% silane and 90% hydrogen, it is shown that the properties of the films compare favourably with the best reported results on those prepared from 100% silane.

    • AC conductivity of amorphous semiconductors

      Abhai Mansingh

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      The models for dielectric relaxation which confine to well defined dielectric loss peaks suggested by the workers from dielectric school and that of frequency dependent ac conductivity suggested by the workers from semiconductor school are briefly reviewed. A brief description of the spurious effects which can give similar relaxation behaviour are also presented. Attempt has been made to explain the observed frequency and temperature dependence of ac conductivity in transition metal ion phosphate glasses by assuming two mechanisms. The first mechanism is responsible for well defined but broad dielectric loss peaks and dominate in the region where measured ac conductivity approaches dc conductivity. Such a mechanism can give a slope of 0·5 over several decades of frequency even in the region where measured ac conductivity is substantially higher than dc conductivity. The second mechanism is responsible for almost linear or sublinear frequency dependent ac conductivity and dominates in the temperature and frequency region where measured ac conductivity is substantially higher than dc conductivity. Measurements of dielectric constant in other amorphous systems in the region where measured ac conductivity approaches dc conductivity are needed to check the validity of the model and the exact origin of the two mechanisms of ac conductivity.

    • Theory of susceptibility of a-Ge and a-Si

      A Mookerjee S C Agarwal

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      We propose a model of the thin films of a-Ge and a-Si with microvoids as frustrated spin glasses. Within this model the various qualitative aspects of the experimental results can be reasonably explained.

    • Ionic sulphate glasses

      K J Rao

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      Sulphate glasses are typical ionic glasses in the sense they are constituted of discrete anions. In this review various physical properties of K2SO4, Na2SO4 and ZnSO4 glasses have been reported. A model of random close packing of ions has been suggested and used to interpret several properties including the origin of mixed alkali effect.

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