A comparative study on Zn0.8Cd0.2O films deposited on different substrates

Highly (0 0 2)-oriented Zn0.8Cd0.2O crystal films were prepared on different substrates, namely, glass, Si(1 1 1) and α-Al2O3(0 0 1) wafers by the dc reactive magnetron sputtering technique. The Zn0.8Cd0.2O/α-Al2O3 film has the best crystal quality with a FWHM of (0 0 2) peak of 0.3700°, an average grain size of about 200 nm and a root-mean-square surface roughness of about 70 nm; yet the Zn0.8Cd0.2O/glass holds the worst crystal quality with a much larger FWHM of 0.6281°. SIMS depth profile shows that the Zn and O compositions change little along the film depth direction; the Cd incorporation also almost holds the line towards the top surface other than an accumulation at the interface between the film and the substrate. The Cd content in the film is nearly consistent with that in target.