Electrical and structural properties of tin-doped indium oxide films deposited by DC sputtering at room temperature

Tin-doped indium oxide (ITO) films were deposited on soda-lime glass plates without substrate heating by de magnetron sputtering. Crystallinity and electrical properties of the films were investigated by X-ray diffraction and Hall-effect measurements, which showed clear dependence on target-substrate distance (T-S) and on total gas pressure (P-tot) during deposition. Degradation in crystallinity was observed at relatively high or low P-tot, where the upper or lower P-tot level for depositing films with high crystallinity was increased with decreasing T-S. Based on a hard sphere collision model, the crystallinity of the films was considered to be strongly affected both by the kinetic energy of sputtered In (or Sn) particles and by the bombardment of high energy particles arriving at the growing film surface. The former could enhance the crystallinity, whereas the latter degraded both the crystallinity and conductivity. Such degradation in electrical properties was mainly due to a decrease in carrier density.