Search

The synthesis of rare-earth (RE)-based silica glass is currently a key challenge for the development of integrated optics devices such as lasers and optical amplifiers. In this work, Tm3+-doped 80SiO2−10ZrO2−10Al2O3 thin films were prepared by sol-gel and dip-coating methods. The structural and optical properties of thin films with different number of coating layers: 15, 20, 25 and 30 layers were investigated. It can be observed from X-ray diffraction (XRD) results that the thin films showed an amorphous characteristic with some crystalline peaks for samples with 20 and 25 layers. From Fourier transform infrared (FTIR) spectroscopy analysis observed that the presence of hydroxyl (OH) absorption and its vibrational (phonon) energy at the band of 3100 cm−1 to 3470 cm−1 which can reduce luminescence characteristic, and significantly affect the optical device performance. The refractive index increases with increasing number of coating layers due to the increase in density, whereas the thickness of the samples become less as the coating layers become denser.

The effect of annealing temperature on the optical and structural properties of Er3+-doped 80SiO2−10ZrO2− 10Al2O3 films fabricated on fused SiO2 glass by sol-gel-dip-coating are investigated. In this paper, the optical and structural properties were characterized by thin film analyzer, X-ray diffraction (XRD) and Fourier transform infrared (FTIR). From thin film analyzer, it showed that the film thickness decreased with the increment of annealing temperature while the refractive index exhibited the opposite trend. OH peak at the range of 3400 cm−1 to 3700 cm−1 which is obtained from FTIR spectra disappear for sample that were annealed at 800°C and 850°C due to absent of OH and water molecules. The XRD pattern shows a broad peak for all samples indicating the amorphous nature of the fabricated film. However, there is one crystalline peak detected at 2θ = 28.4° for sample 850° which is correspond to ZrO2.

Ru doping in charge-ordered Pr0.75Na0.25Mn1-xRuxO3 (x = 0–0.1) manganites was studied to investigate its effect on structure, electrical transport, magnetic properties, and magnetotransport properties. DC electrical resistivity (ρ), magnetic susceptibility, and χ’ measurements showed that sample x = 0 exhibits insulating behavior within the entire temperature range and antiferromagnetic (AFM) behavior below the charge-ordering (CO) transition temperature TCO of 221 K. Ru4+ substitution (x>0.01) suppressed the CO state, which resulted in the revival of paramagnetic to ferromagnetic (FM) transition at the Curie temperature Tc, increasing from 120 K (x = 0.01) to 193 K (x = 0.1). Deviation from the Curie–Weiss law above Tc in the 1/χ’ versus T plot for x = 0.01 doped samples indicated the existence of Griffiths phase with Griffith temperature at 169 K. Electrical resistivity measurements showed that Ru4+ substitution increased the metallic-to-insulating transition temperature TMI from 144 K (x = 0.01) to 192 K (x = 0.05) due to enhanced double-exchange mechanism, but TMI decreased to 176 K (x = 0.1) probably due to the existence of AFM clusters within the FM domain. The present work also discussed the possible theoretical models at the resistivity curve of Pr0.75Na0.25Mn1-xRuxO3 (x = 0–0.1) for the entire temperature range.

The band alignment of Ta2O5/GaN has been measured experimentally. The HCl cleaning has been found to be effective in removing oxygen from the GaN surface and was used prior to deposition of the Ta2O5 films by radio frequency magnetron sputtering. Variable angle spectroscopic ellipsometry was performed to measure the thickness, optical constants and band gap of GaN and Ta2O5/GaN samples. The valence band offset of Ta2O5/GaN was measured by X-ray photoelectron spectroscopy using Kraut's method, and found to be 0.700.25eV. The results provide experimental evidence of an earlier theoretical study of higher effective barrier for holes than for electrons in the Ta2O5/GaN material system. Display Omitted The band alignment of Ta2O5/GaN has been measured experimentally.The HCl treated GaN surface showed the lowest oxygen and carbon contamination.Ta2O5 films of thicknesses up to 10nm were deposited by RF magnetron sputtering.The valence band offset was calculated to be 0.700.25eV using Kraut's method.The band gaps were found by ellipsometry: 3.34eV for GaN and 4.4eV for Ta2O5.

BaO addition to ternary (80–x)TeO2-20ZnO-xBaO (x = 0–20 mol.%) glasses resulted in a decrease in ultrasonic velocities and independent elastic moduli; this result indicated that the rigidity of the glass network weakened possibly because non-bridging oxygen increased. Thermal analysis results showed that glass transition temperature increased as BaO content increased because of the stabilizing effect of Ba2+ on the glass network. Additional analyses using bulk compression and ring deformation models revealed that the ratio between theoretical bulk modulus and experimental bulk modulus increased; this result indicated that the compression mechanism mainly involved isotropic ring compression. Furthermore, the increase in non-bridging oxygen formation with BaO addition caused a decrease in optical energy gap and an increase in refractive index. An increase in Urbach energy indicated that the degree of disorder in the glass system also increased.

Sr doping in the charge-ordered compound Nd0.3La0.2Ca0.5−xSrxMnO3 has been systematically studied to examine its effect on ultrasonic velocity and elastic moduli as well as magnetic and electrical transport properties. DC electrical resistivity, ρ and AC susceptibility, χ′ measurements showed all samples exhibit metal-insulator (MI) behavior accompanied by ferromagnetic-paramagnetic (FM-PM) transition where the MI transition temperature, TMI and FM-PM transition temperature, TC increased with Sr content indicating the enhancement of double-exchange mechanism. Analysis of the resistivity change with respect to temperature, dlnρ/dT−1 versus T indicates onset of charge-ordering (CO) state where its CO transition temperature, TCO decreased with Sr content indicating weakening of the CO state. On the other hand, both absolute longitudinal and shear velocities as well as elastic moduli measured at 80 K increased significantly with Sr doping indicating improvement in elastic properties, which is suggested to be due to the increase in formation of ferromagnetic domains. A longitudinal velocity anomaly characterized by a slope change around the vicinity of TCO was observed for all samples. The longitudinal elastic anomaly is attributed to the Jahn–Teller (JT) effect of Mn3+ ions where analysis of the anomaly using the mean-field theory suggests involvement of the JT effect in the samples, which transforms from dynamic to static type with decreasing temperature. The elastic anomaly shifted down from 222 K (x=0) to 205 K (x=0.05) indicating that the static JT effect was weakened with Sr content.

Elastic properties of lead vanadate (55 − x )V 2 O 5 –45PbO–( x )ZnO glasses were investigated using ultrasonic velocity measurements by pulse-echo-overlap technique at room temperature. Results from the study showed that both longitudinal and shear velocities decreased at x = 5 mol% with the increase of ZnO concentration. The independent longitudinal and shear moduli, C L and μ and Young's modulus ( Y ) also showed decreasing trend at x = 5 mol% as the fraction of ZnO increases. FTIR analysis showed an increase in non-bridging oxygen (NBO) as indicated by the increase in intensity of VO 4 assigned peaks at x = 5 mol% while the increase in intensity of VO 5 assigned peaks at x > 5 mol% indicates increasing bridging oxygen (BO). Analysis of the experimental results using the bulk compression and ring deformation models showed that the calculated value of K bc was higher than that of K e but K bc / K e ratio drops from 2.16 ( x = 5 mol%) to 1.94 ( x = 10 mol%) indicating that bond bending or ring deformation was slightly reduced with addition of ZnO.