Pulsed plasma-assisted PVD sputter-deposited alumina thin films

Crystalline γ-Al2O3 thin films have been deposited using reactive sputtering of aluminum targets. To prevent arcing, a dual magnetron configuration was used, while the targets were powered by a bipolar pulse power generator at 50 kHz. Scanning electron microscopy (SEM) revealed that films grown at 550 °C have a fine-grained morphology. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis revealed that approximately 80% of the film has been condensed and grown in the γ-phase crystal structure. Film hardness and elastic modulus values obtained by nanoindentation on ∼2-μm-thick films were measured as approximately 25 GPa and 350 Gla respectively at 300 mN load. Constant particle bombardment of the growing films was important and the film morphology could be changed from a strong columnar to a dense compact structure.