Specific features of the photodielectric effect in amorphous As2Se3 layers

The photodielectric effect (PDE) in amorphous arsenic triselenide (As₂Se₃) layers has been studied in a weakly varying electric field. As the field frequency decreases in the infra-low-frequency range, the experimentally measured function of relative conductivity coincides with the theoretically predicted behavior. It is established that the frequency dependence of the recombination coefficient exhibits a minimum.     

Ellipsometry and optical measurements on amorphous thin films of As2Se3

Thin films of amorphous AsSe_3/2 have been prepared by thermal evaporation of the material under a vacuum of 1.33×10^?3 Pa. Reflectivity, transmission and ellipsometric measurements of the films have been carried out. The optical energy gap and the absorption coefficient as a function of wavelength were obtained. Two absorption bands were observed and interpreted in terms of defects in the AsSe_3/2 system (homopolar bonds). Analysis of reflection and transmission spectra shows that the electron density at band tails of both conduction and valency bands follows N(E)?E^1/2 (Taue plots). No considerable variations were observed on changing the film thickness.     

Atomic scale structure and dynamics characteristics simulation of amorphous SrTiO3 by molecular dynamics

The atomic scale structure and dynamics characteristics of amorphous SrTiO₃ was simulated by molecular dynamics with potential function including Coulomb interaction, short range repulsion potential, Van der Waals interaction and Morse potential. From the energy and volume’s dramatic increase during heating, the melting point was estimated to be about 2440 K, in good agreement with the experimental value. The amorphous SrTiO₃ was obtained by quenching the liquid to room temperature. The correlation function and coordination numbers of the crystalline, liquid, and amorphous states were analyzed. The diffusion coefficients at various temperatures calculated from the auto correlation function of velocity verified that the melting occurred at 2440 K.     

Pulsed light effects in amorphous As2S3: review

Journal of Materials Science: Materials in Electronics - It is known that amorphous chalcogenide materials exhibit unique optical phenomena, including high nonlinearity, photodarkening, and phase...     

2R optical regenerator in As2Se3 chalcogenide fiber characterized by a frequency-resolved optical gating analysis

We present a detailed analysis of a 2R optical regenerator based on self-phase modulation in As(2)Se(3) chalcogenide glass fiber using frequency-resolved optical gating (FROG). We obtain good agreement between the FROG measurements and theory, and confirm that the output pulses are near-transform limited. We show that two-photon absorption improves the profile of the power transfer function while not degrading the temporal performance.     

Photo-induced changes in optical properties of As2S3 and As2Se3 films deposited at normal and oblique incidence

Photostructural transformations in amorphous chalcogenide films have been a subject of intensive research so far. In this paper we discuss the changes in the optical properties of typical As-based chalcogenide glasses (As₂S₃ and As₂Se₃) on exposure to ultraviolet (UV) light. An attempt has been made to systematically investigate the optical parameters like extinction coefficient, refractive index and optical bandgap of the films by measuring the same for as-grown and UV-exposed amorphous films of As₂S₃ and As₂Se₃ prepared by vacuum evaporation technique.     

Atomic scale structure and dynamics characteristics simulation of amorphous SrTiO3 by molecular dynamics

The atomic scale structure and dynamics characteristics of amorphous SrTiO₃ was simulated by molecular dynamics with potential function including Coulomb interaction, short range repulsion potential, Van der Waals interaction and Morse potential. From the energy and volume’s dramatic increase during heating, the melting point was estimated to be about 2440 K, in good agreement with the experimental value. The amorphous SrTiO₃ was obtained by quenching the liquid to room temperature. The correlation function and coordination numbers of the crystalline, liquid, and amorphous states were analyzed. The diffusion coefficients at various temperatures calculated from the auto correlation function of velocity verified that the melting occurred at 2440 K.     

Growth of highly oriented LiTaO3 thin film on Si with amorphous SiO2 buffer layer by pulsed laser deposition

High-quality single-phase, c-axis textured LiTaO₃ thin films have been deposited on Si(100) substrate with amorphous SiO₂ buffer layer for optic waveguide application by pulsed laser deposition under optimized conditions of 30 Pa oxygen pressure and 650 °C. The amorphous SiO₂ buffer layer with a thickness of 100 nm was coated on the Si(100) by thermal oxidation at 1000 °C. Li-enriched LiTaO₃ ceramic target was used during the deposition. In order to study the influence of oxygen pressure on the orientation, crystallinity and morphology, different oxygen pressures (10 Pa, 20 Pa, 30 Pa and 40 Pa) were used. X-ray diffraction (XRD) results showed that LiTaO₃ thin films exhibited highly c-axis orientation under 30 Pa. It was observed by scanning electron microscopy (SEM) that the as-grown film in the optimal conditions was characterized by a dense and homogeneous surface without cracks, and the average grain size was in the order of 25 nm.     

Fabrication of Ta nanoparticles induced by nanosecond laser ablation in ethanol: the study of laser fluence effects

Tantalum nanoparticles (Ta NPs) were synthesized in ethanol solution by ablation with a 1064 nm Nd:YAG laser. Prepared NPs were investigated by UV-visible absorption spectroscopy, Transmission electron microscopy, X-ray diffraction and Photoluminescence measurement. The average sizes of NPs were calculated to be in the range of 12–18 nm. From the UV-visible studies, the plasmon peak position of Ta NPs was observed in the spectral range of 206–208 nm. The XRD spectra clearly showed the crystalline structure of NPs and various peaks of Ta and Ta₂O₅. Moreover, the UV region in the PL spectrum included the free exciton and the bound exciton emission correlated with the defect concentration. In fact, the laser ablation in the organic and inorganic solvents is a strong technique to obtain some NPs with particular structures, which are impossible to produce by conventional methods.     

Crystal growth and photoluminescence characteristics of Ca2MgSi2O7:Eu3+ thin films grown by pulsed laser deposition

Ca₂MgSi₂O₇:Eu³⁺ films were deposited on Al₂O₃ (0 0 0 1) substrates by pulsed laser deposition. The films were grown at various oxygen pressures ranging from 100 to 400 mTorr. The crystallinity and surface morphology of the films were examined by X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. XRD and AFM respectively showed that the Ca₂MgSi₂O₇:Eu³⁺ films had a zircon structure and consisted of homogeneous grains ranging from 100 to 400 nm depending on the deposition conditions. The radiation emitted was dominated by a red emission peak at 620 nm. The maximum PL intensity of the Ca₂MgSi₂O₇:Eu³⁺ films grown at 300 mTorr was increased by a factor of 1.3 compared to that of Ca₂MgSi₂O₇:Eu³⁺ films grown at 100 mTorr. The crystallinity, surface roughness and photoluminescence of the thin-film phosphors were strongly dependent on the deposition conditions, in particular, the oxygen partial pressure.     

As2Se3-AsTe-CuI系统玻璃的形成和结构研究

为了探索新的透红外材料,本文研究了As₂Se₃－AsTe－CuI系统玻璃的形成区,制备了一系列不同ASTe和CuI含量的玻璃．研究表明：该系统玻璃的形成范围相当大,AS₂Se₃－ASTe二元系统可以任何比例形成玻璃,AS₂Se₃－CuI和AsTe-CuI二元系统,当CSI含量分别达70和40mol％时,仍可形成稳定的玻璃,直径在20mm厚度在50mm以上的玻璃样品很容易得到．研究了部分玻璃样品的远红外光谱,结果表明：该系统玻璃的结构单元主要是：［AS（SeTe）_3-xI_x］（x＝0～3）、［As₂Te₄］和［CuI₄］,随玻璃的成分不同,这些结构单元的相对比例也不同,根据研究结果提出了该系统玻璃的结构模型．     

Some characteristics of mixing and relaxation in Co2 gas-dynamic laser with selective excitation

It is demonstrated by numerical simulation using the simplified Navier-Stokes equations that the geometric arrangement of the nozzle apparatus affects the energy characteristics of a gas-dynamic laser with parallel supersonic mixing of the components.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 1, pp. 90–95, January, 1987.     

The optical characteristics of plasma formed by laser erosion of CdGa2Se4 and CdGa2S4 crystals

The optical emission from fragments formed during a laser-induced erosion of the surface of CdGa₂Se(S)₄ single crystals was studied. The laser plasmas were generated by pulsed radiation of a Nd laser with a beam power density of (1–2)×10⁹ W/cm². The laser plasma exists in the form of a nucleus with a diameter of 2–3 mm, while no plasma torch is formed in the space above the target surface. In the 200–600 nm spectral range, the main emission lines observed in the spectrum of the plasma obtained from a laser-eroded CdGa₂Se₄ crystal corresponded to transitions from the lowest atomic energy levels of Ga(I), as well as to the intense transitions between the electron states of Se(II) and Se(III). The emission spectra of the plasma from a laser-eroded CdGa₂S₄ crystal surface exhibited a single intense line at 532.1 nm showing evidence of a prevailing contribution of the S(II) (4s–4p) transitions. The optical data agree with the results of the mass spectrometric analysis of the laser plasma generated from cadmium thiogallate crystals. The emission characteristics are of interest from the standpoint of the plasma diagnostics and optimization of the technology of laser sputter deposition of thin films with complicated compositions.     

Influence of Bi2O3 in the microstructure of SrBi2Ta2O3 films deposited by pulsed laser ablation

A systematic study of the microstructural features of SrBi₂Ta₂O₉ (SBT) films prepared on Pt(1 1 1)/TiO₂/SiO₂/Si by pulsed laser deposition (PLD) and heat treated at different temperatures, is presented. The films heat treated during deposition have a temperature-induced preferential growth in the (1 1 5) orientation and reach the SBT crystal structure at 600 °C, free from undesired secondary phases. From transmission electron microscopy and X-ray diffraction analysis, the morphology of the SBT and the Bi₂O₃ crystals in the films are determined. Additionally, the non-oriented polycrystalline growth and the development of cracks in films deposited at the lowest temperature (300 °C) and then annealed at high temperatures are explained. It is seen in these films that once the Bi₂O₃ crystal phase is eliminated during the post-annealing process, the growth of the SBT crystals is linear at a rate of of 0.8 nm ° C^-1. It is proposed, as a result of these studies, that a deposition temperature of at least 600 °C should be used to avoid the presence of crystalline Bi₂O₃ and cracking during the post-annealing treatment. © 2001 Kluwer Academic Publishers     

Controlled growth and characteristics of single-phase Cu2O and CuO films by pulsed laser deposition

Copper oxide, Cu₂O and CuO, thin films have been synthesized on Si (100) substrates using pulsed laser deposition method. The influences of substrate temperature and oxygen pressure on the structural properties of copper oxide films were discussed. The X-ray diffraction results show that the structure of the films changes from Cu₂O to CuO phase with the increasing of the oxygen pressure. It is also found that the (200) and (111) preferred Cu₂O films can be modified by changing substrate temperature. The formation of Cu₂O and CuO films are further identified by Fourier transform infrared spectroscopy. For the Cu₂O films, X-ray photoelectron spectroscopic studies indicate the presence of CuO on the surface. In addition, the optical gaps of Cu₂O and CuO films have been determined by measuring the transmittance and reflectance spectra.     

Luminescent properties of SrZnO2:Tb3+ hybrid thin film phosphors grown by pulsed laser deposition

Novel green-light-emitting Tb(3+)-doped SrZnO2 phosphor thin films were grown via the pulsed-laser-deposition technique. The films were grown at various substrate temperatures and oxygen pressures. The crystallinity and surface morphology of the films were investigated via X-ray diffraction (XRD) and atomic-force microscopy (AFM), respectively. The luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. The thin films showed a green emission radiated by the transitions from the 5D4 excited states to the 7FJ (J = 3-6) ground states of the Tb3+ ions found under ultraviolet excitation with a 272 nm wavelength. The crystallinity, surface morphology, and photoluminescence spectra of thin-film phosphors were found to be highly dependent on the deposition conditions, particularly the substrate temperature and oxygen pressure. The surface roughness and photoluminescence intensity of the films showed similar behaviors as a function of the substrate temperature and oxygen pressure.     

Ti:Al2O3 laser pumped by radiation from a copper-vapor laser

A scheme enabling spatial matching of copper-vapor laser radiation, which pumps a mode of an Al₂O₃:Ti laser cavity, has been developed and implemented. It is shown that copper vapor lasers as pump sources for titanium-sapphire lasers are fully capable of competing with conventional pump sources. Pis’ma Zh. Tekh. Fiz. 25, 6–11 (September 26, 1999)