INFLUENCE OF THE SUBSTRATE-TEMPERATURE ON THE STRUCTURE AND SURFACE-ROUGHNESS OF CD0.18SB0.64TE0.18 FILMS

Using a radiofrequency sputtering deposition technique, ternary Cd0.18 Sb0.64Te0.18 thin films have been grown on glass substrates at several substrate temperatures (50-250 degrees C). The samples have an Sb con tent of about 63 at %, as measured by Auger spectroscopy. The surface roughness, the structural and the electrical properties of the films w ere studied as a function of substrate temperature. X-ray diffraction (XRD) measurements showed that the structure of the films changes from an amorphous phase, when deposited at lower substrate temperatures, t o a mixture of two crystalline phases (CdTe and Sb) for higher substra te temperatures. Atomic force microscopy shows an increase in the surf ace roughness with an increase in the substrate temperature, clearly s howing the formation of crystalline phases with microcrystallite sizes in good agreement with those determined from XRD measurements. The am orphous-to crystalline transition is accompanied by an abrupt increase in the room temperature electrical conductivity of the films. This in crease in the conductivity as well as its temperature dependence in th e range of room temperature to 150 degrees C can be understood in term s of an electrical percolation process through the conducting Sb cryst allites.