Fabrication of smooth Al nanolayers at different temperatures

In e-beam physical vapour deposition (PVD) system 70 and 110 nm thick aluminium films are deposited on epi-polished fused silica and sapphire substrates. We compare average values of four surface morphology parameters: peak-to-peak height, average roughness, root mean square (RMS) roughness and grain size diameter measured on Al films fabricated in three temperatures 170, 297 and 450 K. Variable surface roughness of these films results from the competitive interaction of two opposing influences: the mismatch of expansion coefficients of materials involved Al, SiO₂ and Al₂O₃ and the diffusivity of Al atoms on cooled/heated substrates. Temperature of substrates is measured within one centigrade accuracy. Surface morphology parameters are measured using atomic force microscope. The best RMS is achieved in Al films deposited on sapphire at 170 K.