Temperature dependent electrical behaviour of Cu2SnS3 films

Abstract

The temperature dependent electrical properties of the dropcasted Cu2SnS3 films have been measured in the temperature range 140 K to 317 K. The log I versus √V plot shows two regions. The region at lower bias is due to electrode limited Schottky emission and the higher bias region is due to bulk limited Poole Frenkel emission. The ideality factor is calculated from the ln I versus V plot for different temperatures fitted with the thermionic emission model and is found to vary from 6.05 eV to 12.23 eV. This large value is attributed to the presence of defects or amorphous layer at the Ag / Cu2SnS3 interface. From the Richardson's plot the Richardson's constant and the barrier height were calculated. Owing to the inhomogeneity in the barrier heights, the Richardson's constant and the barrier height were also calculated from the modified Richardson's plot. The I-V-T curves were also fitted using the thermionic field emission model. The barrier heights were found to be higher than those calculated using thermionic emission model. From the fit of the I-V-T curves to the field emission model, field emission was seen to dominate in the low temperature range of 140 K to 177 K. The temperature dependent current graphs show two regions of different mechanisms. The log I versus 1000/T plot gives activation energies Ea1 = 0.367095 − 0.257682 eV and Ea2 = 0.038416 − 0.042452 eV. The log (I/T2) versus 1000/T graph gives trap depths Φo1 = 0.314159 − 0.204752 eV and Φo2 = 0.007425 − 0.011163 eV. With increasing voltage the activation energy Ea1 and the trap depth Φo1 decrease. From the ln (IT1/2) versus 1/T1/4 graph, the low temperature region is due to variable range hopping mechanism and the high temperature region is due to thermionic emission.