RESUMEN
Gadolinium oxide is an excellent optical material that offers high transmission in a wide wavelength range of 200-1600 nm and exhibits a high bulk refractive index of â¼1.80 at 550 nm. In the present study, a set of Gd2O3 thin films has been deposited on fused silica substrates by RF sputtering of a Gd2O3 target under various O2 to Ar flow ratios. The samples have been characterized by grazing incidence x-ray diffraction (GIXRD) to study the long range structural behavior, by GIXR to study density and surface roughness of the films, by atomic force microscopy measurements to study morphological properties, by Rutherford backscattering measurements for compositional studies, and by transmission spectrophotometry and spectroscopic ellipsometry techniques to study their optical properties. It has been observed that the films deposited with 10% oxygen partial pressure have low density, high surface roughness, and high void content, which results in a low value of refractive index of this film, and film quality improves as oxygen partial pressure is further increased. Extended x-ray absorption fine structure measurement with synchrotron radiation has also been employed to extract local structural information around Gd sites, which has in turn been used to explain some of the observed macroscopic properties of the films.
RESUMEN
Two sets of HfO2 thin film have been deposited by the radio frequency magnetron sputtering technique at various oxygen partial pressures, one set without any substrate bias and another set with a 50 W pulsed dc substrate bias. The films have been characterized by extended x-ray absorption fine structure (EXAFS) measurements at the Hf L3 edge, and the structural information obtained from analysis of the EXAFS data has been used to explain the macroscopic behavior of the refractive index obtained from spectroscopic ellipsometry measurements. It has been observed that the variation of refractive index with oxygen partial pressure depends on the Hf-Hf bond length for the set of films deposited without substrate bias, while for the other set of films deposited with pulsed dc substrate bias, it depends on the oxygen coordination of the nearest neighbor shell surrounding Hf sites.
RESUMEN
ZrO2 thin films with 0%, 7%, 9%, 11%, and 13% Gd doping have been prepared by RF magnetron sputtering and have been characterized by grazing incidence x-ray diffraction, spectroscopic ellipsometry, and optical transmission measurements to probe their structural and optical properties. Extended x-ray absorption fine structure (EXAFS) measurements have also been carried out on the samples at the Zr K- and Gd L3-edges. It has been observed that Gd goes to Zr sites up to 9%-11% doping concentration, and for Gd doping concentrations beyond 11%, Gd precipitates out as a separate Gd2O3 phase. The local structure information surrounding the Zr and Gd sites obtained from the analysis of the EXAFS studies have also been used to explain the macroscopic optical properties of the samples.
RESUMEN
Tantalum pentoxide (Ta2O5) thin films have been deposited on fused silica substrates using a novel asymmetric bipolar DC magnetron sputtering technique under a mixed ambient of oxygen and argon. Films have been prepared at different oxygen-to-argon ratios, and the sputtering ambient and optical properties of the films have been investigated by spectroscopic ellipsometry, while the structural analysis of the films has been carried out by grazing incidence x-ray diffraction and extended x-ray absorption fine structure (EXAFS) measurements. The concentration of oxygen and tantalum in the Ta2O5 films has been estimated by Rutherford backscattering spectrometry (RBS). The variation of the optical constants of the films with changes in deposition parameters has been explained in the light of the change in average Ta-O bond lengths and oxygen coordination around Ta sites as obtained from EXAFS measurements. The trend in variation of the oxygen-to-tantalum ratio in the films obtained from RBS measurement, as a function of oxygen partial pressure used during sputtering, is found to follow the trend in variation of the oxygen coordination number around Ta sites obtained from EXAFS measurement.