Incorporation of iron cations into epitaxial sapphire thin films by co-evaporation and subsequent thermal annealing

Abstract

Iron-doped sapphire thin films have been successfully epitaxially grown onto sapphire single crystal substrates by electron beam deposition and subsequent thermal annealing. Amorphous Al{sub 2}O{sub 3} thin films, about 280--390 nm thick, cation doped with iron have been deposited on [0001] oriented sapphire substrates. Iron doping with cation concentrations (a ratio of Fe content to total cation content) up to 5 at % can be incorporated into the octahedral sites of Al-cation sublattice during the epitaxial regrowth process at 1,000--1,400 C, as determined by Rutherford Backscattering Spectrometry and ion channeling measurements. Cross-sectional Transmission Electron Microscopy shows the presence of two distinct regions in the annealed films. One exhibits the epitaxial relationship with the sapphire substrate and the second region has amorphous type of contrast. External optical transmittance measurements in the ultra violet and visible light range have exhibited the absorption associated with Fe{sup 3+}. This study has demonstrated a simple method of incorporating dopants into single crystal sapphire, which has potential in the fabrications of thin film planar optical waveguides.