Effect of pulsed off-times on the reactive HiPIMS preparation of zirconia thin films

The pulsed off-time is a crucial parameter in reactive high power impulse magnetron sputtering (HiPIMS). In this work, zirconia thin films were deposited using reactive HiPIMS. The mean ionization distance of zirconium atoms was calculated as a function of electron energy and plasma density. The peak current and power density of the target increased with increasing off-times during the sputtering process. Furthermore, the microstructural, optical, and electrical properties of thin films fabricated using various off-times were investigated. Atomic force microscopy revealed a minimal RMS roughness of less than 1.7 nm was obtained. The transmittances of all films exceeded 89.3%. The energy band gap shifted to high energy as the pulsed off-time was increased. The film prepared with a pulsed off-time of 2500 μs yielded the highest energy band gap (5.93 eV) and the lowest leakage current density (0.7 × 10^-7 A/cm²).