Amorphous Er 2 O 3 films are deposited on Si (001) substrates by using reactive evaporation.This paper reports the evolution of the structure,morphology and electrical characteristics with annealing temperatures in an oxygen ambience.X-ray diffraction and high resolution transimission electron microscopy measurement show that the films remain amorphous even after annealing at 700 C.The capacitance in the accumulation region of Er 2 O 3 films annealed at 450 C is higher than that of as-deposited films and films annealed at other temperatures.An Er 2 O 3 /ErO x /SiO x /Si structure model is proposed to explain the results.The annealed films also exhibit a low leakage current density (around 1.38 × 10 4 A/cm 2 at a bias of 1 V) due to the evolution of morphology and composition of the films after they are annealed.
Stoichiometric and amorphous Er2O3 films were deposited on Si(001) substrates by radio frequency magnetron technique. Spectroscopic ellipsometry measurement showed that the refractive index of the Er2O3 film in wavelength region of 400-1000 nm was between 1.6-1.7. The reflectivity of the Er2O3 films decreased greatly with respect to that from the uncoated Si substrates. The absorption coefficient of the Er2O3 film indicated that it had an energy gap larger than 4.5 eV. The obtained characteristics indicated that Er2O3 films could be promising candidates for anti-reflection coatings in solar cells.
Amorphous Er2O3 films have been fabricated on p-type Si(001) substrates using radio frequency magnetron sputtering technique. Vacuum ultraviolet spectra were employed to investigate the samples. An optical gap of 6.17 eV for Er2O3 films was obtained from the ab-sorption coefficient spectra. A possible reason was put forward to explain the inconsistent results about the band gap of Er2O3 in literatures. Emission spectra exhibited a strong emission band at 494 nm with the incident ultraviolet light of 249 nm. The observed high density of emission bands of Er2O3 films in the visible wavelength indicated that Er2O3 films could be used in Si solar cells for increasing conversion efficiency.
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.
Er2O3-Al2O3 film was deposited on the Si(001) substrate by radio frequency magnetron technique at room temperature.The samplewas annealed at 450,600 and 750 oC for 30 min in O2 ambience,respectively.The optical constants were studied by spectroscopic ellipsometryfor both the as-deposited and the annealed samples.The proper values of refractive index indicated that it could be a useful material for solar cells.
