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 \Omega -1cm-1for pure SnO 2 to 1 \Omega -1cm-1for SnO 2 which was doped by adding 9 percent Sb 2 O 3 to the target. Transparency was above 85 percent. Films sputtered from targets containing more than 10 percent Sb 2 O 3 were 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 SnO 2 films. Below this temperature, successive heating and cooling in nitrogen caused increased conductivity and improved stability.