Dc and ac conductivity of amorphous CuInTe2 thin films

摘要

Dc and ac conductivity studies were made on a-CuInTe$-2$/ thin films deposited onto substrates held at liquid nitrogen temperatures. The dc results may be understood in terms of three modes of current paths, viz., hopping of carriers near the valence band tail, near an acceptor induced defect state and near the Fermi level at appropriate temperature ranges. A reasonable fit to the ac loss data could be made using the extended pair approximation due to Summerfield. Dc conductivity measurements were made using a two probe gap cell configuration. Thick Cu/In strips with well-defined parallel edges were deposited on the sample for electrical contacts. Film thicknesses ranged from 1500 to 6000 A. One electrode of the film was connected to a constant dc voltage source, and the other electrode was grounded through a Keithley 610 electrometer. The applied voltage was 5 V (corresponding to a field of 5 Vcm$+$MIN@1$/), which was well within the ohmic region of the film's I -V characteristics in the temperature region scanned. Cooling and warming up rates used in the measurements were of the order of 0.3 deg min$+$MIN@1$/. The current noise was below 10$+$MIN@15$/ A and the drift of the electrometer during the experiment was checked periodically. As deposited, all the films were p-type in nature as envisaged by the hot probe method.