Heat Treatment of Dc-Sputtered Tin Dioxide Thin Films

Tin dioxide thin films were deposited by dc glow discharge sputtering using a compressed powder target. The conductivity of these films varied from 3 X 10^{-5 -1}cm^-1for pure SnO2to 1 ^-1cm^-1for SnO2which was doped by adding 9 percent Sb2O3to the target. Transparency was above 85 percent. Films sputtered from targets containing more than 10 percent Sb2O3were highly resistive as a result of lattice disorder. Such films, however, became conductive upon post-deposition heat treatment. This paper presents the results of the heat treatment of these antimony-doped tin dioxide films. The variation of resistivity with temperature was found to be very complex. It not only depends on the previous heat-treatment history but also on the ambient sputter gas used during deposition. Heating beyond 400°C resulted in a general decrease in the conductivity of SnO2films. Below this temperature, successive heating and cooling in nitrogen caused increased conductivity and improved stability.