Sputtering deposited ternary Zn1−xCdxO crystal films on Si(111) substrates

Using the d.c. reactive magnetron sputtering method we have successfully deposited completely (002)-oriented ternary Zn1−xCdxO (0≤x≤0.6) alloy crystal films without Cd segregation on Si(111) substrates. X-Ray photoelectron spectroscopy measurements show that Cd/Zn ratios in the films are nearly consistent with those in the targets. The Zn and Cd exist only in oxidized states, no evidence of metallic Zn or Cd was observed. The O/(Cd+Zn) atomic ratios of the films are in the range of 0.89–0.98. Transmission electron microscopy measurements show that for the (002)-oriented films the grains are columnar structures with the c-axis perpendicular to the Si substrate. By post-annealing treatments in O2 ambient, the crystal quality of the Zn1−xCdxO films can be improved. For the sample of x=0.2, the optimal annealing temperature is 500 °C.