Persistent Photoconductivity Study on Ion Irradiated Carbon Films
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ABSTRACT Conducting carbon films are irradiated by high energy ion beam and persistent photoconductivity has been found from the irradiated samples. A complex distribution of traps created mostly by random displacement of carbon atoms by energetic ion beam from its polymeric matrix showed a persistent photoconductivity at low temperatures down to 50K. From the photo decay constants and the magnitude of photocurrent the density of traps and the corresponding activation energies have been calculated. INTRODUCTION: During irradiation by high energy ion beam the carbon atoms are displaced from their position creating a change in its polymeric matrix [1], [2] which introduces some more defects, in the as-prepared amorphous carbon film. As a result some localized traps can be created in the pseudo-gap region of the material. Photo conductivity is a good technique to determine defect centres and distribution of traps in the photosensitive materials both in crystalline and amorphous state. One of the objects of such an experiment is to determine the trap parameter of the system. Transient photocurrent measurements with pulsed excitation have been extensively used to study the states in the band-gap as well as the properties of carrier transport and recombination in the amorphous semiconductors. A power-law decay of photocurrent like 1' VP is observed, where 0
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