Microstructure Evolution in Nitrogen Implanted Sapphire
Low-energy 14N+ ions were implanted with 23 keV under normal incidence into C-axis (0001) sapphire at room temperature. DYNAMIC-TRIM calculations were performed to calculate the N depth profiles for the various fluences from 1x1016 to 1017 cm-2. Electron Beam Annealing (EBA) was performed at a sample temperature of 700 °C for 10 min to allow the implanted and substrate atoms in the implanted layer to move to energetically preferable positions. Nuclear Reaction Analysis revealed the implanted nitrogen ion concentrations. Atomic Force Microscopy and Scanning Electron Microscopy show some nanostructures at the surface of the sapphire substrate exhibiting an average width of 139 ± 25 nm and height of 37 ± 7 nm using the lowest fluence of 1x1016 ions cm-2. Notably for samples implanted with the highest fluence of 1x1017 ions cm-2, bubble/holes like structures appeared after EBA due to out-diffusion of nitrogen that causes blistering and exfoliation effects.
George Ferguson, Ashvin Thambyah, Michael A Hodgson and Kelly Wade
J. Kennedy et al., "Microstructure Evolution in Nitrogen Implanted Sapphire", Advanced Materials Research, Vol. 275, pp. 222-225, 2011