Crystallinity of Gallium-Doped Zinc Oxide Films Deposited by DC Magnetron Sputtering Using Ar, Ne or Kr Gas

Gallium-doped zinc oxide (GZO) films were deposited at RT by dc planar magnetron sputtering under various total gas pressures ( P tot ) ranging from 0.25 Pa to 2.5 Pa using Ar as the sputtering gas and a GZO ceramic oxide target. The GZO films showed highest crystallinity at P tot = 2.0 Pa and showed clear degradation at a lower or higher P tot . For a comparative study, Ne or Kr was also used as a sputtering gas. The mechanisms of degradation were investigated, considering the effects of bombardment of high-energy particles on the growing film surface and the energy of sputtered particles, where kinetic energies of these particles were estimated by Monte Carlo simulation. It was shown that sputtered particles lost sufficient energy for surface migration to form a crystalline structure at a higher P tot . The high-energy neutrals of the sputtering gas (Ar 0 , Ne 0 , and Kr 0 ) which recoiled from the target surface should be primarily responsible for the structural damage in the film at a lower pressure.