The influence of deposition conditions upon the structural and electrical properties of amorphous thin films, deposited by radio-frequency sputtering at substrate temperatures of 220C (glass substrates) and 400C (Mo and ITO/glass substrates), was studied by using both X-ray diffraction and electrical dark conductivity measurements at −150 to 150C. An increase in sputtering Ar pressure, PAr, led to the growth of an amorphous structure and reduced the room-temperature dark conductivity, σRT, which suggested a reduction in the density of defects. Similar results were obtained with a decrease in the direct-current self-bias voltage, Vp, of radio-frequency electrodes. These results suggested that the density of defects was reduced with decreasing energy of the bombarding species, while increasing PAr or decreasing Vp. The product of the target-to-substrate distance and the Ar pressure, (dPAr), confirmed some published results which indicated that the density of defects could be significantly reduced by reducing the energy of the bombarding species while increasing PAr or decreasing Vp. High-resistivity (108Ωcm) materials were obtained using low Vp or high dPAr values. Annealing considerably reduced the room-temperature dark conductivity.

Structural and Electrical Properties of Amorphous GaAs Sputtered at High Substrate Temperature (220 and 400C). B.El Hadadi, H.Carchano, J.L.Seguin, H.Tijani: Vacuum, 2005, 80[4], 272-83