Transport properties of Ni-WS2 photoconductive thin films

It is shown that the annealing under Ar of sputtered WSx amorphous films deposited on Ni coated substrates gives bidimensional polycrystalline 2H-WS2 films. Ni enhances the formation of large crystallites. The temperature dependence of the mobility and its dependence versus the Ni content clearly show that transport properties are governed by grain boundaries. A basic grain boundary model like the model of Seto is well suited to explain the electrical properties. The photoconductivity enhancement resulting from nickel is assigned to a decrease of the number of the electrical barriers. However, noise measurements are not consistent with Hall measurements; a model is thus proposed to explain the 1/f noise excess in relation to the traces of Ni-W revealed by x-ray diffraction. (C) 1997 American Institute of Physics.