Characterisation of aluminium oxide thin films deposited on polycarbonate substrates by reactive magnetron sputtering

Amorphous aluminium oxide thin films were deposited on polycarbonate substrates by direct current (d.c.) reactive magnetron sputtering. The thicknesses of the thin films varied between 250 nm and 3.0 μm. The phenomena during the processing were investigated by mass spectrometer connected directly to the process chamber. Hydrocarbon radicals were observed during the plasma treatment. The thin films properties of interest were nanohardness, elastic modulus, adhesion force, film density, ratios of Al/O and Ar/Al, and transmittance. Film cracking was observed probably due to high residual stresses. Thermal stress represented slight compressive nature. Improved thin film performance was observed when the substrates were pre-treated with argon plasma. Cross-linking and chemical modifications of the substrate occurred due to VUV-radiation of plasma. The XPS results showed the breakage of CO and C–H bonds at the surface of the treated substrates.