Impact of deposition temperature on microstructure and properties of erbium oxide antireflective films deposited on CVD diamond substrates

To improve the transmittance of chemical vapor deposition (CVD) diamond, erbium(III) oxide (Er2O3) antireflective films were deposited on CVD diamond substrates by radio frequency (RF) magnetron sputtering. Effects of deposition temperature on structure, chemical composition and properties of the samples were investigated. A strong correlation was observed between the deposition temperature and crystalline structure evolution of the Er2O3 antireflective films. With rising deposition temperature, the deposition rate, grain size and surface roughness of the Er2O3 antireflective films increased. Changes of composition and chemical bonding of the films were analyzed. Results showed that the amount of bonding between Er and O atoms surface as the temperature increased. The films were structured by amorphous, monoclinic and cubic phase, with preferential orientations of C-Er2O3 {222} at deposition temperature increased to 400 degrees C. A thickness of 10 nm transition layer was observed between the Er2O3 antireflective films and the CVD diamond substrates by transmission electron microscopy (TEM). Moreover, the transition layer feature primarily consisted of Er, O and C. The hardness and modulus of Er2O3 antireflective films were increased for higher deposition temperature, which positively affects the IR transmittance and adhesion strength of the Er2O3 antireflective films on CVD diamond substrates.