Influence of substrate temperature, deposition rate, surface texture and material on the structure of uhv deposited erbium films

Structure of erbium films of 600 nm thickness deposited onto molybdenum substrates of different surface roughness (R_q=151, 500 and 850 nm), glass substrates, and amourphous carbon substrates, for substrate temperatures between 300 and 860 K, at 0.55 and 2.5 nm s^-1 deposition rates, are investigated by electron microscopy and X-ray diffraction. The microstructures of the films broadly follow the trends of the Movchan and Demchishin and Thornton zone models, but show some departures in all zones, particularly prominent growth steps and layering. The grain size at a 2.5 nm s^-1 deposition rate is found to be between two and five times larger, depending on substrate temperature, than at 0.55 nm s^-1 under corresponding conditions, and the variation of grain size with temperature is found to be consistent with the activation energy model of Grovenor et al. X-ray diffraction analysis shows a (002) preferred orientation which reaches a maximum at a 575-775 K substrate temperature, and is stronger for the higher deposition rate. The microstructures and preferred orientations of erbium films are found to be influenced by the surface roughness and material of the substrate.