TRANSPORT-PROPERTIES OF NI-WS2 PHOTOCONDUCTIVE THIN-FILMS

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