Magnetron Sputtered Oxide Thin Films Research Articles

Ga-doped ZnO films magnetron sputtered at ultralow discharge voltages: Significance of controlling defect generation

In magnetron sputtered oxide thin films, both the structure and physical properties are affected by bombardment-induced defects and their annihilation. Ga-doped zinc oxide (GZO) films with low Ga content (~1.7 at.%) were magnetron sputtered at various discharge voltages (70–220 V) and the growth temperatures (130 °C and 380 °C). The microstructure was characterized by X-ray Diffractometry, Raman Spectroscopy, and Transmission Electron Microscopy. Meanwhile, the electrical and optical properties were measured by Hall-effect measurement and Spectroscopic Ellipsometry, respectively. We found that reducing the discharge voltage led to higher structural quality and better electrical properties, independent of the growth temperature. The benefit, from using a high temperature (i.e., 380 °C), of the structural improvement, can only be achieved when the discharge voltage has been decreased to ultralow (i.e., 70 V). Our results suggest that for high quality GZO films deposition, controlling the defect generation should be preferable to simply increasing the growth temperature.

Microstructure evolution of radio-frequency magnetron sputtered oxide thin films in the Cr–Zr–O system

Oxide thin films in the Cr–Zr–O system with various microstructures and properties were synthesized by reactive radio-frequency magnetron sputtering of a segmented chromium–zirconium target. Nanocrystalline Cr–Zr–O thin films with continuously changing compositions from chromium-rich to zirconium-rich were obtained in a single deposition process. The Cr–Zr–O thin films were characterized by electron probe microanalysis, X-ray diffraction and transmission electron microscopy. Up to a zirconium content of 12at.% films with a metal/oxygen concentration ratio of 2/3 were deposited. These films revealed a single-phase solid solution (Cr,Zr)2O3 corundum structure. An increasing zirconium (and decreasing chromium) concentration promoted the formation of ZrO2 structures accompanied by a change of the metal/oxygen concentration ratio towards 1/2. First, a cubic, then a tetragonal phase was formed, while at the highest zirconium content a monoclinic phase evolved in addition to the tetragonal phase. Microindentation analysis showed for the single-phase corundum films an increase in hardness of about 20% to 19GPa with an increase of the zirconium content from 8at.% to 12at.%. Films with a ZrO2 structure exhibited indentation hardness values superior to those reported for bulk cubic and monoclinic ZrO2.