Shift Of Fundamental Absorption Edge Research Articles

Effect of erbium nanoparticles on structural and spectroscopic properties of bio-silica borotellurite glasses containing silver oxide

Er3+ NPs doped bio-silica borotellurite glasses containing silver oxide were prepared using melt quenching techniques. The silica used was extracted from rice husk by acid leaching process. Optical absorption and photoluminescence properties of the glass samples were studied. The samples were confirmed to be amorphous in nature from the XRD results. The FTIR results reveal the existing functional groups in the glass structure. XRF result shows that 98.6% silica was obtained from the rice husk. The optical absorption spectra revealed that fundamental absorption edge shifts to longer wavelength as the content of erbium NPs increases. The value of band gap had been calculated and shown to be increased with an increase content of erbium NPs. The Urbach energy was shown to be linearly decreased with an increase in content of erbium NPs oxides. The introduction of silver oxides modifies the optical properties of the glass. The emission cross-section (δe) and gain bandwidth (FWHM ×δe) for 4I13/2→4I15/2 transition were calculated from the McCumber theory. The photoluminescence spectra revealed three emission bands corresponding to 4H11/2-4I15/2 (470 nm), 4S3/2-4I15/2 (561 nm) and 4F9/2→4I15/2 (758 nm) transitions assigned to green and red emissions respectively. The results suggest that these glasses might be used as a promising candidate as well as gain media for solid state lasers.

Room temperature stabilized TiO2 doped ZrO2 thin films for teeth coatings–A sol-gel approach

Zirconia (ZrO2) is a strong, osseoconductive, transparent ceramic thus can be used as protective coatings. Moreover, its ivory color makes it suitable for teeth coatings. The aim of this study is to prepare transparent, dense and single-phase coatings. Sol-Gel spin coating method is used to synthesize TiO2 doped ZrO2 coatings. Dopant concentration is varied in the range of 1 to 5 wt%. Rietveld refined X-ray diffraction results of as-deposited thin films depict the formation of phase pure tetragonal zirconia (t-ZrO2) at 3 wt% of TiO2 content. Crystallite size for phase pure t-ZrO2 is observed to be ∼13 nm with reduced unit cell volume of 136.5 Å3. High X-ray density (∼5.75 g/cm3) and low porosity (∼6%) of thin films result in high value of hardness (∼1363HV). Phase pure t-ZrO2 thin films, with 3 wt% TiO2 doping, show ∼80% transmission along with direct energy band gap value of 5.15eV. Shift in fundamental absorption edge from 220 nm to 240 nm has been observed revealing the band gap in the range of 5.15–5.6eV for 1 to 5 wt% TiO2 content. The high refractive index is an indication of high x-ray density of doped ZrO2 coatings. FTIR and Raman fundamental tetragonal bands appearing at 470 cm−1 and 148 cm−1, respectively, confirm the formation of t-ZrO2 for 3 wt% TiO2 content. High grain-boundary resistance (0.597MΩ) and high dielectric constant (∼36) along with low tangent loss are observed at 3 wt% TiO2 concentration. Here we report TiO2 stabilized t-ZrO2, at room temperature with high density, low porosity, high hardness and better transparency, a potential material for teeth coatings. To the best of our knowledge TiO2 doped ZrO2 thin film with pure tetragonal phase (t-phase), at very low dopant concentration (3 wt%), under as deposited conditions is one of its kind report.

The effect of erbium oxide in physical and structural properties of zinc tellurite glass system

In this research, the melt-quenching method was used to synthesize a series of zinc tellurite glass systems doped with erbium oxide with the chemical composition of [(TeO2)0.7 (ZnO)0.3]1−x (Er2O3)x at different molar fraction, x = 0, 0.01, 0.02, 0.03, 0.04 and 0.05. X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, density, molar volume, elastic and optical measurements were used to characterize the prepared glass samples. At room temperature, the result of the XRD, FTIR, density, elastic and optical properties were all recorded. An amorphous nature of glass samples is proven by the XRD spectra. The analysis of FTIR spectra shows the presence of functional vibration of tellurite network. It is observed that the density of the glass system increase with the molar fraction of Er2O3. The value of molar volume is found to be directly proportional to the density. Thus, the increment in the density value causes the increment of the molar volume due to the increase of erbium concentration. This in turn results in the creation of excess free volume due to the difference of atomic radius between erbium and tellurite. On the other hand, ultrasonic velocity was used to determine the elastic moduli of the glass systems. The elastic moduli such as longitudinal modulus, shear modulus, bulk modulus and Young's modulus give a fluctuating trend against the concentration of Er2O3. The increase of the elastic moduli is due to the mix former effect. In contrast, the decrease of the elastic moduli is due to the breakdown of Er2O3 in the zinc tellurite glass system which weakens the glass structure of the ternary tellurite system. The optical properties of the prepared glasses were determined by UV–vis analysis. The optical absorption was recorded at room temperature in the wavelength ranging from 220 nm to 800 nm. The optical absorption spectra reveal that fundamental absorption edge shifts to higher wavelength as the content of erbium oxide increase. The values of direct and indirect band gap have been calculated and are observed to decrease with the increase content of erbium oxide. However, the Urbach energy, refractive index, molar refraction and electronic polarizability are shown to be increased with an addition content of erbium oxides.

Edge Absorption of (Y0.06Ga0.94)2O3 Thin Films

Fundamental absorption edge of (Y0,06Ga0,94)2O3 thin films, obtained by radio-frequency ion-plasmous sputtering, was investigated using the method of optical spectroscopy. It was established that these films are formed in the monoclinic structure of β-Ga2O3. The optical band gap of these films is greater than β-Ga2O3 films and is 4.66 eB for films annealed in oxygen atmosphere, 4.77 eV for the films annealed in argon atmosphere and 4.87 eV for the films, restored in a hydrogen atmosphere. Consolidated effective mass of free charge carriers in (Y0,06Ga0,94)2O3 films after annealing and after reconstitution in hydrogen was estimated. It was found that the concentration of charge carriers after annealing in oxygen atmosphere is 1.32×1018 cm-3, after annealing in argon atmosphere - 3.41×1018 cm-3 and after reconstitution in hydrogen is 5.20×1018 cm-3, which is typical for degenerated semiconductors. It was shown that the shift of fundamental absorption edge in (Y0,06Ga0,94)2O3 thin films is caused by Burstein-Moss effect.

Synthesis and characterization of bismuth phosphate nanoparticle in glass matrix

Glasses having composition 5Li2O–5ZnO– xBi2O3 –(90 − x) P2O5 (x = 5, 10, 15, 20 and 25 mol%) were prepared by the normal melt quenching technique. Nanocomposite glass containing bismuth phosphate BiPO4 nanocrystals was obtained, which can be attributed to homogeneous nucleation process. The formation of BiPO4 nanocrystals was confirmed and characterized by X-ray diffraction patterns (XRD), transmission electron microscopy (TEM), differential scanning calorimetry, optical absorption (UV–Vis) and micro-hardness studies. The morphological analysis by XRD and TEM microscopy showed the formation of hexagonal BiPO4 nanocrystals, and its estimated nanocrystalline sizes were found to be varying from 5.35 to 11.53 nm depending on the Bi2O3 concentrations. The density (ρ) and molar volume (V m) were also determined and found to be in compositional dependence. Glass transition temperature (T g) and glass crystallization temperature (T c) were obtained and found to be increased (from 240.0 to 337.2 °C) with increasing Bi2O3 up to 20 mol% and then decreased (from 337.2 to 331.8 °C) due to the structural changes in the glass network. Effect of BiPO4 content on the optical properties had been investigated. From the UV–Vis spectra, it was observed that the fundamental absorption edge shifts toward lower wavelengths, i.e., blueshifts with increasing Bi2O3 mol% up to 20 mol%, and then shifts toward higher wavelengths, i.e., redshifts beyond 20 mol%. It was also observed that the obtained E opt (for indirect and direct transitions) increases with gradual increase in Bi2O3 content up to 20 mol% and then decreases beyond 20 mol%. This may be due to the introduction of Bi cations into the glass network as a network former up to 20 mol% causing a decrease in ΔE values, beyond 20 mol%, the introduction of Bi ions into the glass network interstitially leads to increase the values of ΔE. The optical properties of the present nanocrystallized glasses showed a quantum size dependence, in which the optical band gap energy (E opt) was changed as a function of BiPO4 nanocrystalline sizes.

Optical band gap tuning of Sb-Se thin films for xerographic based applications

In the present paper we have studied the effect of Sb addition on the optical band gap tuning of thermally evaporated SbxSe100-x (x = 0, 5, 20, 50 and 60) thin films. The structural investigations revealed that all thin films were amorphous in nature. Transmission spectrum was taken in the range 400–2500 nm shows that all films are highly transparent in the near infrared region. The fundamental absorption edge shifts towards longer wavelength with Sb incorporation. The optical band gap decreases with addition of antimony in a-Se thin films. A good correlation has been drawn between experimentally estimated and theoretically calculated optical band gap. The decrease in optical band gap of thin films has been explained using chemical bond approach and density of states model. Decrease in optical band gap with Sb addition increases the concentration of electron deep traps which increases the X-ray sensitivity of Sb-Se thin films. Thus by tuning the optical band gap of Sb-Se alloy, it could be utilized for xerographic based applications.

Optical and Vibrational Spectra of CsCl-Enriched GeS2-Ga2S3 Glasses.

Optical and FTIR spectroscopy was employed to study the properties of 80GeS2-20Ga2S3-CsCl chalcohalide glasses with CsCl additives in a temperature range of 77–293 K. It is shown that CsCl content results in the shift of fundamental absorption edge in the visible region. Vibrational bands in FTIR spectra of (80GeS2-20Ga2S3)100 − х(СsCl)x (x = 5, 10, and 15) are identified near 2500 cm−1, 3700 cm−1,, around 1580 cm−1, and a feature at 1100 cm−1. Low energy shifts of vibrational frequencies in glasses with a higher amount of CsCl can be caused by possible thermal expansion of the lattice and nanovoid agglomeration formed by CsCl additives in the inner structure of the Ge-Ga-S glass.

Effect of Samarium Nanoparticles on Optical Properties of Zinc Borotellurite Glass System

The glass series of samarium nanoparticles (NPs) doped zinc borotellurite glasses were successfully fabricated by using conventional melt-quenching technique. The structural properties of the prepared glasses were investigated by X-ray diffraction (XRD) analysis and FTIR analysis. It was confirmed that the prepared glasses are amorphous in nature. The bonding parameters of the glasses were analyzed by using FTIR analysis and were found the formation of non-bridging oxygen. The density of these glasses were measured and found to be increased with increasing samarium NPs content. The optical absorption spectra of these glasses were revealed that the fundamental absorption edge shifts to higher wavelengths as the content of Sm2O3 (NPs) increases. The optical energy band gap are found to be decreased linearly with an increasing samarium NPs concentration which is due to the formation of non-bridging oxygen in the glass system.KeywordsBorotellurite glass; optical band gap, Samarium nanoparticles.

Effect of compositional dependence on physical and optical parameters of Te17Se83−xBix glassy system

In the present paper we have studied the effect of Bi addition on the physical and optical properties of thermally evaporated Te17Se83−xBix thin films. With Bi addition the density, mean coordination number, mechanical constraints, glass transition temperature increases. The other parameters theoretical energy gap, lone pair electron, deviation from stoichiometry decreases. Transmission spectra have been taken in the spectral range 400 nm–2500 nm using ultraviolet–visible–near infrared spectrophotometer. The fundamental absorption edge shifts towards longer wavelength with Bi incorporation. Optical energy gap and linear refractive index have been determined using transmission spectra. A good correlation has been drawn between the optical and theoretical parameters. Using linear optical parameters, the nonlinear optical susceptibility and nonlinear refractive index have been estimated.

Edge Absorption of thin Films –Ga2O3

Fundamental absorption edge of b–Ga2O3 thin films, obtained by radio-frequency ion-plasmous sputtering, was investigated, using the method of optical spectroscopy. It was ascertained that the optical band gap Eg increases from 4.60 to 4.65 eV after the heat treatment films in argon atmosphere and to 5.20 eV after the reduction of annealed films in a hydrogen atmosphere. Consolidated effective mass of free charge carriers in b–Ga2O3 films after annealing and after reduction in hydrogen was estimated. It was found that the concentration of charge carriers after heat treatment in argon atmosphere is 7.30´1017 cm–3 and after reduction in hydrogen, is 2.62´1019 cm–3, which is typical for degenerated semiconductors. It was shown that the shift of fundamental absorption edge in thin films b–Ga2O3 after reduction in hydrogen is caused by Burstein-Moss effect.

Experimental and theoretical investigations of structural and optical properties of copper doped ZnO nanorods

We report on structural and optical properties of undoped and Cu-doped ZnO nanorods on glass substrates by sol–gel and hydrothermal method. The grown thin film nanorods samples were characterized by X-ray diffraction, field emission scanning electron microscopy (FESEM) and UV visible spectroscopy. The XRD and FESEM reveal that grown nanorods have hexagonal wurtzite structure along the c-axis. The UV–Vis absorption spectra for all samples displayed a band gap absorption peak at about 365 nm. The band gap value has decreased since 5 and 10 % doped ZnO indicates a red shift in comparison with undoped ZnO and 15 and 20 % doping concentration shows blue shift compared with lower doping. However, with doping, a decrease in the band gap value of undoped sample was observed by indicating a red shift of fundamental absorption edge. Photoluminescence spectra of the nanorod arrays samples show that a higher concentration of Cu exhibited a 61.82 % increased IUV/IDLE ratio compared with undoped samples. Oxygen insufficiencies were reduced with doped samples. Cu doping diminishes the recombination of electrons and holes by bonding with electrons in singly ionized oxygen vacancies. As a result, green emission was abridged, and the optical properties have improved with Cu incorporated in host lattice. The observed experimental band gap value was tuned from 3.21 eV (ZnO) to 3.07 eV (Zn0.9Cu0.1O), which was closer to the theoretical band gap values confirmed by first principle calculations that combined generalized gradient approximation with included scissor operator.

Effect of Erbium Nanoparticles on Optical Properties of Zinc Borotellurite Glass System

Erbium nanoparticles (NPs) doped zinc borotellurite glasses have been prepared by conventional melt‐quenching technique with the chemical composition (where y = 0.005, 0.01, 0.02, 0.03, 0.04, 0.05). The structural properties of the prepared glasses were determined via X‐ray diffraction (XRD) analysis and FTIR analysis. It was confirmed that the prepared glasses are amorphous. The bonding parameters of the glasses were analyzed by using FTIR analysis and were confirmed to be ionic in nature. The refractive index increases as the content of erbium NPs increases. The optical absorption spectra revealed that fundamental absorption edge shifts to longer wavelength as the content of erbium NPs increases. The value of band gap had been calculated and shown to be decreased with an increase content of erbium NPs. The Urbach energy was shown to be linearly increased with an increase content of erbium NPs oxides.

Electro-Optical Properties of Different HxLi1-xNbO3 Phases in Proton-Exchanged LiNbO3 Waveguides

Optical LiNbO3 waveguides were fabricated by annealed proton exchange technique. Red shift of fundamental absorption edge has been related to the polarization-induced decrease of band-gap energy. Raman and IR-reflection spectroscopy were used for evaluation of the phase composition, as well as for estimation of structural disorder in waveguides. Electro-optical properties of the waveguides have been found to be depending on the phase composition that was changed intentionally by variation of fabrication conditions. The experimental phase modulators fabricated with the optimal technological conditions exhibit an improved electro-optical efficiency compared to LiNbO3 modulators produced with the standard fabrication parameters.

Photoelectrochemical property of ZnFe 2O 4/TiO 2 double-layered films

ZnFe 2O 4/TiO 2 double-layered films on indium-tin oxide (ITO) substrate were prepared by a dip-coating method, and the optical absorption and photocurrent of the as-prepared films were measured. In the double-layered films, the onset of fundamental absorption edge shifts to a longer wavelength, and even shifts to a longer wavelength than that of ZnFe 2O 4-only film as the ZnFe 2O 4 layer thickness increases. Application of the coupled photoanodes double-layered films composed of ZnFe 2O 4 and TiO 2 can obviously increase the photocurrent. It was found that the photocurrent density of ZnFe 2O 4/TiO 2 double-layered films first increased and then decreased with increasing the ZnFe 2O 4 layer thickness. A five-fold increase in the photocurrent density was obtained compared with TiO 2-only films under optimum condition.

Optical properties of CdSe and CdTe nanoparticles embedded in SiO2 films

ABSTRACTCdSe and CdTe nanoparticles dispersed in silicon dioxide films have been grown by magnetron sputtering technique followed by thermal annealing. Effect of thermal annealing conditions on the structural and optical properties of CdTe and CdSe nanoparticles has been studied. Glancing angle x-ray diffraction (GAXRD), optical absorption (OA), transmission electron microscope (TEM) and spectroscopic ellipsometry (SE) techniques have been used to study the crystal structure, particle size and dielectric function spectra of nanoparticles. ε2 spectra of CdTe nanoparticles show a decrease in dielectric constant values in comparison to bulk CdTe. ε2″ spectrum of CdTe nanoparticles show four critical points in the electronic band structure of CdTe. Optical absorption studies in the case of CdTe and CdSe nanoparticles clearly show the blue shift of fundamental absorption edge due to quantum confinement effect.

Nonlinear optical effect of co-doped Mg, Zn: LiNbO3

Two damage-resistant impurity ions, Mg and Zn, were co-doped into LiNbO3 crystals with various concentrations. Infrared and UV-VIS transmission spectra were used to characterize the co-doped crystals. Experimental results show that such co-doping leads to the crystal fundamental absorption edge shifts to shorter wavelength direction and that 3.0 mol. % Mg and more than 2.0 mol. % Zn co-doping results in shifts of the OH transmission peak. Second harmonic generation efficiencies and phase matching temperatures were also studied experimentally.

Electronic spectra and optical band gap studies in neodymium chlorophosphate glasses

The present work aims to study the variation of optical band gaps, intensity parameters, and radiative lifetimes with different metal ions in various chlorophosphate glasses. Different chlorophosphate glasses in the composition range 50P 2O 5+30Na 2HPO 4+19.5RCl (R=Li, Na, K, Ca and Pb) with 0.5 mol% Nd 2O 3 were prepared by quenching melts consisting of the above chemicals (1100–1200°C, 1.5–2 h) between two brass plates. Using the optical absorption spectra, the optical properties have been systematically studied. The position of the absorption edge and hence, the values of optical band gaps have been reported. Except for potassium, the position of the fundamental absorption edge shifts to longer wavelengths with an increase of average molecular weight of the glass. Judd–Ofelt analysis is used along with a spectral analysis to calculate the intensity parameters, radiative lifetimes and branching ratios. The lifetime of all the states are high in these chlorophosphate glasses when compared with chloroborate glasses. There is no relation between the spontaneous emission probabilities and ion packing ratios in these phosphate glasses as observed in other glass systems. The predicted radiative transition probabilities ( A), radiative lifetimes ( τ R), branching ratios ( β) and integrated absorption cross-sections ( Σ) for certain excited states of Nd 3+ doped glasses have also been reported.

Optical absorption spectra of acceptor-doped SrZrO 3 and SrTiO 3 perovskite-type proton conductors

The optical absorption spectra were investigated to study the electronic structures of perovskite-type proton conductors. The fundamental absorption edge shifts to higher energy side when an acceptor ion was doped to the perovskite-type oxides. In SrZrO 3, an absorption band was observed in the lower energy side of the fundamental absorption edge when an acceptor was doped. It is suggested that this band corresponds to the acceptor level of the proton conductors. The absorption of this band was enhanced when the proton was removed from the crystal. This suggests that the number of electrons in the acceptor level decreases when a proton is introduced to the crystal.

Optical properties of tin-lead oxide films

tometers; UV-Vis in the wavelength range 1.3-3 ~m and NIR-60 in the range 0.4-1.3 #m. The surface electrical resistance was determined using the four-probe technique. X-ray diffraction analysis of the films revealed only peaks that could be described as referred to the tetragonal structure. The calculated lattice constants were monotonic functions of the target composition in the range of values characteristic for SnOe and /3-PbO2, suggesting that the tin-to-lead ratio of the targets reproduces in the films. However, as the change of crystal parameters is generally small, the error of this estimation is relatively large. Moreover, the analysis of films deposited by this method has shown a poorer lead content in films than in targets [7]. The values of x here from the target composition should be treated only qualitatively. The measured transmission spectra for films of different composition are presented in Fig. 1. It can be seen that the fundamental absorption edge shifts towards lower energies with increasing lead content. The results presented may be referred to the previously determined optical gaps [4] listed in Table I. The data are in good agreement except for

Optical-absorption spectra of crystal-field transitions in MnPS3 at low temperatures.

The manganese thiophosphate (${\mathrm{MnPS}}_{3}$) optical-absorption spectrum has been investigated as a function of temperature from 300 down to 10 K in the visible region. With decreasing temperature, the fundamental absorption edge shifts towards higher energies without changing its shape and an additional subband-gap feature appears. This structure has been attributed to transitions between the ${\mathrm{Mn}}^{2+}$ third excited state and the ground state. All the subband-gap structures exhibit a small temperature shift, in good agreement both with the crystal-field theory and with the so-called transition-metal weakly interacting model. The temperature dependence of the crystal-field parameters Dq, B, and C has been determined from the transition energies. These results support the hypothesis that ${\mathrm{MnPS}}_{3}$ is to be considered an ioniclike compound, as already suggested in the literature.