Effects of Thermal Annealing on the Properties of Zirconium-Doped Mg_xZn_1-XO Films Obtained through Radio-Frequency Magnetron Sputtering

Zirconium-doped Mg_xZn_1-xO (Zr-doped MZO) mixed-oxide films were investigated, and the temperature sensitivity of their electric and optical properties was characterized. Zr-doped MZO films were deposited through radio-frequency magnetron sputtering using a 4-inch ZnO/MgO/ZrO₂ (75/20/5 wt%) target. Hall measurement, X-ray diffraction (XRD), transmittance, and X-ray photoelectron spectroscopy (XPS) data were obtained. The lowest sheet resistance, highest mobility, and highest concentration were 1.30 × 10³ Ω/sq, 4.46 cm²/Vs, and 7.28 × 10¹⁹ cm^-3, respectively. The XRD spectra of the as-grown and annealed Zr-doped MZO films contained Mg_xZn_1-xO(002) and ZrO₂(200) coupled with Mg(OH)₂(101) at 34.49°, 34.88°, and 38.017°, respectively. The intensity of the XRD peak near 34.88° decreased with temperature because the films that segregated Zr⁴⁺ from ZrO₂(200) increased. The absorption edges of the films were at approximately 348 nm under 80% transmittance because of the Mg content. XPS revealed that the amount of Zr⁴⁺ increased with the annealing temperature. Zr is a potentially promising double donor, providing up to two extra free electrons per ion when used in place of Zn²⁺.