  This work reports the electrical transport and temperature-dependent
photoconductivity in tungsten diselenide (WSe2) thin films. The electrical
conductivity analysis shows the presence of the three regions with temperature
variation. At lower temperatures (<190K), carriers become localized to small
regions in the film due to the Mott hopping mechanism. The middle region (190
to 273 K) follows Seto parameters and obtained low barrier height (0.0873 eV)
may be responsible for the improved carrier mobility. At higher temperature
(>273K) region, thermally activated conduction is dominated with two activation
energies of ~138 meV and 98 meV. The peaks obtained in photoluminescent
analysis attributes to the presence of mid-bandgap states or defect states
which play an important role in the photoconductivity of WSe2. The transient
photoconductivity measurements show consistent temperature-dependent behaviour.
The effect of light intensity and wavelength variation on the photoconductivity
of WSe2 thin films is also discussed. The photocurrent is 1.19*10-5 A at 125 K
while at 350 K it was observed to be 3.12*10-4 A. The light-on/off current
cycles show that the current can recover to its initial state which points to
the stable and outstanding reversible properties of the WSe2 thin film device
to be used in photodetector applications.
