Transparent conducting amorphous Zn-Sn-O films deposited by simultaneous dc sputtering

The films of ZnO-SnO2 system were deposited on glass substrates by simultaneous dc magnetron sputtering apparatus, in which ZnO and SnO2: Sb (Sb2O5 3 wt % doped) targets faced each other. The substrate temperatures were maintained at 150, 250, and 350degreesC, respectively. As an experimental parameter, current ratio sigma=I-Zn/(I-Zn+I-Sn,), which corresponds to ZnO target current (I-Zn) divided by the sum of ZnO and SnO2: Sb target currents (I-Zn + I-Zn), was adopted. Amorphous transparent films appeared for 0.50less than or equal to8less than or equal to0.73, which could be correlated to compositions as [Zn]/([Sn]+[Zn])=0.33-0.67 by x-ray fluorescent analysis. At [Zn]/([Sn]+[Zn])=1/2 (sigma =0.62), 2/3 (sigma=0.73) and all other ratios in as-deposited films, neither crystalline ZnSnO3 nor Zn2SnO4 was obtained. Minimum resistivity of 4-6 X 10(-2) Omega cm was found at delta = 0.50, whose composition was approximately SnO2.ZnSnO3. Resistivity increased linearly with an increase of the current ratio, until the composition reached Zn2SnO4. The amorphous phase showed a constant Hall mobility of similar to10. cm(2)/V s and a linear decrease in carrier concentration with increasing Zn content. (C) 2004 American Vacuum Society.