Study of transport properties of Ni ion irradiated Ge20Se74Bi6 for different ion fluences

Amorphous semiconductors in the system Ge20Se80-xBix exhibit p-n transition in the electronic transport. This makes them an interesting class of amorphous semiconductors. Amorphous thin films of Ge20Se74Bi6 prepared by flash evaporation in a vacuum of 10(-5) Torr were characterized in XRD, XRF, DSC, EPMA. Samples were irradiated with 75 MeV Ni ions at fluences varying from 5x10(12) to 10(14) ions/cm(2). The ion induced effects on the properties of the unirradiated and irradiated films studied by measuring dc electrical conductivity, optical band gap and thermoelectric power. Dc electrical conductivity measured from 77K to 476K, optical spectra were recorded in the range 200nnn to 800nm while the thermoelectric power measurements carried out using differential dc method in the temperature range 4.2K to 300K. Both the electrical activation energy and the optical band gap decreases with increasing ion fluence. The results thus obtained suggest increase in band tailing