Structural, morphological and optical properties of ZnO thin films grown on gamma-LiAlO2 substrate by pulsed laser deposition

ZnO thin films were deposited on the substrates of (100) gamma-LiAlO2 at 400, 550 and 700 degrees C using pulsed laser deposition (PLD) with the fixed oxygen pressure of 20 Pa, respectively. When the substrate temperature is 400 degrees C, the grain size of the film is less than 1 mu m observed by Leitz microscope and measured by X-ray diffraction (XRD). As the substrate temperature increases to 550 degrees C, highly-preferred c-orientation and high-quality ZnO film can be attained. While the substrate temperature rises to 700 degrees C, more defects appears on the surface of film and the ZnO films become polycrystalline again possibly because more Li of the substrate diffused into the ZnO film at high substrate temperature. The photoluminescence (PL) spectra of ZnO films at room temperature show the blue emission peaks centered at 430 nm. We suggest that the blue emission corresponds to the electron transition from the level of interstitial Zn to the valence band. Meanwhile, the films grown on gamma-LiAlO2 (LAO) exhibit green emission centered at 540 nm, which seemed to be ascribed to excess zinc and/or oxygen vacancy in the ZnO films caused by diffusion of Li. from the substrates into the films during the deposition.

Ce：Lu2Si2O7闪烁晶体的结构和光谱特性

采用中频感应提拉法生长出Ce：Lu：Si2O7(Ce：LPS)晶体．通过x射线粉末衍射分析，晶体结构属单斜晶系的C21m空间群·光学显微镜下可观测到晶体的(110)解理．在室温下测试了Ce：LPS晶体的吸收光谱、激发光谱和发射光谱。结果表明，Ce：LPS晶体的吸收峰只有两个，分别位于302和349nm，且与激发峰的位置一致，归因于Ce^3+的4f^1→5d^1跃迁的特征吸收所致．发射光谱具有Ce^3+典型的双峰特征，经Gaussian多峰值拟合，带状谱是由384和407nm两个发射峰叠加而成，且后者的强度

Yb:Y2-2xLa2xO3激光透明陶瓷的光谱性能

It was first reported the spectral properties of a low-temperature sintered transparent Yb: Y2-2x La-2x O-3 laser ceramics. Yb: Y2-2x La-2x O-3 laser ceramics have broad absorption band and large absorption cross- section of 4.0 x 10(-20) cm(2) at wavelengths 977nm of the highest absorption peak. Its fluorescence lifetime is 1.1 ms, and the emission cross-sections are 1.0 x 10(-20) cm(2) and 0.7 x 10(-20) cm(2) at wavelengths 1033nm and 1077nm, respectively. All the optical properties are similar to those of single crystals.

Diode-pumped Yb : GSO femtosecond laser

Compact femtosecond laser operation of Yb:Gd2SiO5 (Yb:GSO) crystal was demonstrated under high-brightness diode-end-pumping. A semiconductor saturable absorption mirror was used to start passive mode-locking. Stable mode-locking could be realized near the emission bands around 1031, 1048, and 1088 nm, respectively. The mode-locked Yb: GSO laser could be tuned from one stable mode-locking band to another with adjustable pulse durations in the range 1 similar to 100 ps by slightly aligning laser cavity to allow laser oscillations at different central wavelengths. A pair of SF10 prisms was inserted into the laser cavity to compensate for the group velocity dispersion. The mode-locked pulses centered at 1031 nm were compressed to 343 fs under a typical operation situation with a maximum output power of 396 mW. (c) 2007 Optical Society of America.

在钛酸锶衬底上外延生长ZnO薄膜及其性能研究

用脉冲激光淀积法（PLD）在（111）面SrTiO3衬底上外延生长ZnO单晶薄膜。样品分别在衬底温度为350℃、500℃、600℃下外延生长。X射线衍射（XRD）的结果表明,所得的ZnO单晶薄膜结晶性能好,只出现（002）和（004）两个衍射峰,（002）峰的半高宽度（FWHM）为0.23°。在荧光光谱中我们只观察到来源于带边激子跃迁的强UV发射,并且随着生长温度的升高,紫外峰的强度逐渐增强。样品的SEM图像表明所得ZnO薄膜表面平整,晶粒均匀。衬底温度为600℃时,所得到的ZnO薄膜结构完整,晶粒尺寸最

Spectroscopic properties of Yb:YAP crystal

The 10at% Yb-YAP crystal has been grown by the Czochralski method. The absorption and emission spectra and fluorescence lifetime of Yb:YAP crystal at room temperature were studied. There is a strong absorption band centered at 959 nm and the absorption cross-section of 1.51 × 10^-20 cm². The emission cross-section at 1040 nm is 0.6 × 10^-20 cm² and the fluorescence lifetime is about 1.2 ms. The effects of O₂-annealing on the spectral properties were studied. The spectroscopic properties strongly depended on the axis direction and b axis was the best direction for laser output. The spectrum parameters of Yb:YAP and Yb:YAG crystal were compared.}

γ-LiAIO2上非极性ZnO薄膜制备及其光谱性质研究

利用激光脉冲沉积（PLD）技术在（302）γ-LiAIO2衬底上成功生长了非极性的a面（112^-0）γZnO薄膜．衬底温度为350℃时，薄膜是混合取向（a向和C向），以c面ZnO为主，且晶粒尺寸分布很宽；提高温度达500℃，薄膜变为单一的（1120）取向，摇摆曲线半高宽O.65^o，晶粒尺寸分布趋窄，利用偏振透射谱可以明显看出其面内的各向异性．衬底温度650℃下制备的样品晶粒继续长大，虽然摇摆曲线半高宽变大，但光致发光谱（PL）带边发射峰半高宽仅为105meV，比在350℃，500℃下制备的样品小1／5

Growth and characterization of ZnO films on (0 0 1), (1 0 0) and (0 1 0) LiGaO2 substrates

ZnO films were fabricated on LiGaO2 (0 0 1), (10 0) and (0 10) planes by RF magnetron sputtering. The structural, morphological and optical properties of as-grown ZnO films were investigated by X-ray diffraction (XRD), atomic force microscopy (AFM), Raman spectra and photoluminescence (PL) spectra. It is found that the orientation of ZnO films is strongly dependent on the substrate plane. [0 0 0 11, [1 (1) over bar 00] and [11 (2) over bar0] oriented ZnO films are deposited on LiGaO2 (001), (100) and (010), respectively. AFM shows the (0001) ZnO film consists of well-aligned regular hexagonal grains. Raman spectra reveal a tensile stress in the (0 0 0 1) ZnO film and a compressive stress in (110 0) and (112 0) ZnO films. PL spectra of all ZnO films exhibit only a near-band-edge UV emission peak. (C) 2008 Elsevier B.V. All rights reserved.

Anisotropic crystallographic properties, strain, and their effects on band structure of m -plane GaN on LiAlO2 (100)

The m-plane GaN films grown on LiAlO2(100) by metal-organic chemical vapor deposition exhibit anisotropic crystallographic properties. The Williamson-Hall plots point out they are due to the different tilts and lateral correlation lengths of mosaic blocks parallel and perpendicular to GaN[0001] in the growth plane. The symmetric and asymmetric reciprocal space maps reveal the strain of m-plane GaN to be biaxial in-plane compress epsilon(xx)=-0.79% and epsilon(zz)=-0.14% with an out-of-plane dilatation epsilon(yy)=0.38%. This anisotropic strain further separates the energy levels of top valence band at Gamma point. The energy splitting as 37 meV as well as in-plane polarization anisotropy for transitions are found by the polarized photoluminescence spectra at room temperature. (c) 2008 American Institute of Physics.

Holmium laser in-band pumped by a thulium laser in the same host of YAlO3

We report on the room-temperature continuous-wave (CW) operation of a Ho:YAlO3 laser that is resonantly end pumped at 1.94 mu m by a diode-pumped thulium-doped laser in the same host. Through the use of a 1 at % Ho3+-doped 20-mm-long YAlO3 crystal (b cut), the Ho:YAlO3 laser generated 1 W of linearly polarized (E//c) output at 2118 nm and 0.55 W of E//a output at 2128.5 nm for an incident pump power of 5 W, with an output coupler transmission of 14 and 3%, respectively. An optical-to-optical conversion efficiency of 20% and a slope efficiency of 33% were achieved at 2118 nm corresponding to an incident pump power.

γ-LiAlO_2上a面ZnO薄膜的光谱特性研究

利用激光脉冲沉积(PLD)技术在(302)γ-LiAlO2衬底上成功生长了非极性的a面(1120)ZnO薄膜,光致发光谱(PL)带边发射峰半峰宽仅为115meV.研究了非极性ZnO薄膜光谱特性的面内各向异性,发现随着入射光偏振方向改变,在偏振透射光谱上,吸收边移动了20meV,这与A、B激子和C激子的能量差一致;而在拉曼光谱上,激发光偏振方向的改变导致E2模式的强度发生明显改变.

Growth of alpha-Al2O3:C crystal with highly sensitive optically stimulated luminescence

In this work. an alpha-Al2O3:C crystal was directly grown by the temperature gradient technique (TGT) using Al2O3 and graphite powders as the raw materials. The optical, optically stimulated luminescence (OSL) properties and dosimetric characteristics of as-grown crystal were investigated. As-grown alpha-Al2O3:C crystal shows strong absorption band at 205, 230 and 256 nm. Three-dimensional thermoluminescence (TL) emission spectrum of the crystal shows a single emission peak at similar to 415 nm. The OSL decay curve can be fitted to two exponentials, the faster component and the slower component. The OSL response of the crystal shows a linear-sublinear-saturation characteristic. As-grown alpha-Al2O3:C crystal shows excellent linearity in the dose range from 5 x 10(-6) to 50 Gy. For doses higher than the saturation dose (100 Gy). the OSL sensitivity decreases as the dose increases. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Enhancement of near-band edge photoluminescence of ZnO thin films by employing MgF2 buffer layer

ZnO/MgF2/ZnO sandwich structure films were fabricated. The effects of a buffer layer on structure and optical properties of ZnO films were investigated by X-ray diffraction, photoluminescence, optical transmittance and absorption measurements. Measurement results showed that the buffer layer had the effects of improving the quality of ZnO films and releasing the residual stresses in the films. The near-band edge emissions of ZnO films deposited on the MgF2 buffer layer were significantly enhanced compared with those deposited on bare substrate due to the smaller lattice mismatch between MgF2 and ZnO than that between fused silica and ZnO. (c) 2006 Elsevier B.V. All rights reserved.

Effect of microstructure of TiO2 thin films on optical band gap energy

TiO2 coatings are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for four hours, the spectra and XRD patterns of TiO2 thin film are obtained. XRD patterns reveal that only anatase phase can be observed in TiO2 coatings regardless of the different annealing temperatures, and with the increasing annealing temperature, the grain size gradually increases. The relationship between the energy gap and microstructure of anatase is determined and discussed. The quantum confinement effect is observed that with the increasing grain size of TiO2 thin film, the band gap energy shifts from 3.4 eV to 3.21 eV. Moreover, other possible influence of the TiO2 thin-film microstructure, such as surface roughness and thin film absorption, on band gap energy is also expected.

Influence of buffer layer thickness on the structure and optical properties of ZnO thin films

A series of ZnO thin films were deposited on ZnO buffer layers by DC reactive magnetron sputtering. The buffer layer thickness determination of microstructure and optical properties of ZnO films was investigated by X-ray diffraction (XRD), photoluminescence (PL), optical transmittance and absorption measurements. XRD results revealed that the stress of ZnO thin films varied with the buffer layer thickness. With the increase of buffer layer thickness, the band gap edge shifted toward longer wavelength. The near-band-edge (NBE) emission intensity of ZnO films deposited on ZnO buffer layer also varied with the increase of thickness due to the spatial confinement increasing the Coulomb interaction between electrons and holes. The PL measurement showed that the optimum thickness of the ZnO buffer layer was around 12 nm. (c) 2005 Elsevier B.V. All rights reserved.