Effect of deposition distance and temperature on electrical, optical and structural properties of radio-frequency magnetron-sputtered gallium-doped zinc oxide

Abstract: Films of gallium-doped zinc oxide (GZO) were deposited on glass substrates by radio-frequency magnetron sputtering using a ceramic target of Ga:ZnO (4at.% Ga vs. Zn). Both the substrate temperature (T s) and the target–substrate distance (d ts) were varied and the effect on electrical, optical and structural properties of the resulting films were measured. The highest conductivity of 3200S/cm was obtained at a deposition temperature of 250°C, at a d ts of 51mm. This sample had the highest carrier concentration in this study, 9.6×1020/cm3. Optical transmittance of all films was <90% in the visible range. The grain size of the film grown at d ts =51mm was smaller than the grain size for films grown with a shorter d ts; moreover, the films with d ts =51mm exhibited the smoothest surface, with a root mean square surface roughness of 2.7nm. Changes in T s have a more pronounced effect on conductivity compared to changes in d ts; however, variations in structure do not appear to be well-correlated with conductivity for samples in the 2000–3200S/cm range. These results suggest that incorporation and activation of Ga is of key importance when attempting to obtain GZO films with conductivities greater than 2000S/cm. [ABSTRACT FROM AUTHOR]