Band gap and structure characterization of Tm2O3 films

Single crystalline Tm2O3 films were grown on Si (001) substrates by molecular beam epitaxy using metallic Tm source and atomic oxygen source. X-ray photoelectron spectroscopy, atomic force microscopy and high-resolution transmission electron microscopy were employed to investigate the compositions, surface morphology and microstructure of the sample. A very flat surface with a root mean square roughness of 0.3 nm could be reached, and a sharp interface between the film and the Si substrate was achieved. The result of optical spectrum at ultraviolet and visible wavelengths showed that the band gap of the Tm2O3 film was 5.76 eV.