Papers by Keyword: Optical Band Gap Energy

Abstract: The purpose of this research is to study the interrelation between Urbach energy (E_u), optical band gap energy (E_g), and complex dielectric constant (ε) in relation to the disorder induced properties of SiO₂/rGO thin films. The rGO-like carbon was created by annealing coconut shell carbon (csc) at different temperatures of 400°C, 600 ^oC, and 800 ^oC. From the analyses, it obtained E_g which was varied from 2.01 eV until 2.67 eV. While E_u from 0.13 eV until 0.26 eV. The results showed that the E_u varied inversely to the E_g. The Penn model and hydrogen-like atom model theories were used to investigate the interrelation between E_u and ε. Finally, it is shown that the Urbach energy is linearly and inversely related to the imaginary and real parts of dielectic constant, respectively.

Abstract: This research presents effect of sintering temperature T and structural transition process on magnetic and optical properties of as-prepared magnetite Fe²⁺Cr_0.2Fe_1.8O₄ nanoferrites which synthesized by Co-precipitation method and sintered at different T. Structural phase of crystal lattice was converted from-cubic magnetite-to-maghemite-to-hexagonal hematite with T. Specific surface area S revealed decrease against crystallite size R. Saturation magnetization M_S proved dependence on R and porosity P. Strain behavior Ԑ enhanced band gap energy E_g.

Abstract: This paper presents the optical properties of erbium doped tellurite glasses with the composition of 55TeO₂-2Bi₂O₃-35ZnO-5PbO-(3-x)Na₂O-xEr₂O₃ where x = 0, 0.5, 1.0, 1.5, 2.0, 2.5, and 3.0 mol% . Refractive index of the glasses was measured using Brewster’s angle method and their optical absorption spectra were measured in spectral range 200 – 1100 nm recorded at room temperature. The results show that the glass refractive index increases with the increase of Er³⁺ ion content in the glass and the optical band gap energy decreases with the increase of erbium content in the glass.

Abstract: The track etch detector, CR-39, in common use is the most sensitive to recording charged particles. The CR-39 polymer samples were irradiated with alpha particle at different energies (2.17 MeV and 3.95 MeV) and fixed fluence followed by chemical etching with different times (1.50, 3.00 and 6.00 hrs). The formed tracks in CR-39 due to irradiations were visualized by using etching technique. The optical properties of CR-39 polymer after etching processes were studied with ultraviolet-visible (UV-vis) spectroscopy. Moreover, the optical band gap energy was calculated for the different etching times (1.50, 3.00 and 6.00 hrs). The average value of the track diameter of irradiation at 2.17 MeV and etching time 1.5 hr is fairly large compared with its value at 3.95 MeV. This is due to the production of defect levels in the band gap of polymer at the 2.17 MeV. The virgin and 2.17 MeV samples at 3.00 and 6.00 hrs have the same optical behavior resulted in the etching solution at those etching times has reached the end of the alpha particle path and progress in all the directions in the bulk of CR-39 with the same rate.

Abstract: Effect of substrate temperature on lanthanide oxide material Gd2O3 thin films deposited by e-beam evaporation has been reported in the present work. Optical properties and surface morphology of as deposited films have been measured using spectrophotometry and atomic force microscopy respectively. Optical constants such as refractive index, extinction coefficient, band gap and Urbach energy have been determined by analysis of experimentally recorded absorption, transmittance and reflection data in wavelength range 200-800nm. Optical band gap energy shows decreasing while Urbach energy shows increasing behavior with increasing temperature. Extinction coefficient and refractive index with varying wavelengths are also calculated. Surface topographies of all samples are studied by atomic force microscope (AFM) and root mean square (RMS) value of roughness is observed increasing with increasing substrate temperature.