Optical, structural and laser-induced damage threshold properties of HfO2 thin films prepared by electron beam evaporation

We prepare HfO2 thin films by electron beam evaporation technology. The samples are annealed in air after deposition. With increasing annealing temperature, it is found that the absorption of the samples decreases firstly and then increases. Also, the laser-induced damage threshold (LIDT) increases firstly and then decreases. When annealing temperature is 473K, the sample has the highest LIDT of 2.17J/cm(2), and the lowest absorption of 18 ppm. By investigating the optical and structural characteristics and their relations to LIDT, it is shown that the principal factor dominating the LIDT is absorption.

Structure and optical properties of ZnS thin films grown by glancing angle deposition

The glancing angle deposition (GLAD) technique was used to deposit ZnS films by electron beam evaporation method. The cross sectional scanning electron microscopy (SEM) image illustrated a highly orientated microstructure composed of slanted column. The atomic force microscopy (APM) analysis indicated that incident flux angle had significant effects on the nodule size and surface roughness. Under identical nominal thickness, the actual thickness of the GLAD films is related to the incident flux angle. The refractive index and in-plane birefringence of the GLAD ZnS films were discussed, and the maximum bireffingence Delta n = 0.036 was obtained at incident flux angle of alpha = 80 degrees. Therefore, the glancing angle deposition technique is a promising way to create a columnar structure with enhanced birefringent property. (c) 2005 Elsevier B.V. All rights reserved.

Y2O3 stabilized ZrO2 thin films deposited by electron beam evaporation: Structural, morphological characterization and laser induced damage threshold

Four kinds of Y2O3 stabilized ZrO2 (YSZ) thin films with different Y2O3 content have been prepared on BK7 substrates by electron-beam evaporation method. Structural properties and surface morphology of thin films were investigated by X-ray diffraction (XRD) spectra and scanning probe microscope. Laser induced damage threshold (LIDT) was determined. It was found that crystalline phase and microstructure of YSZ thin films was dependent on Y2O3 molar content. YSZ thin films changed from monoclinic phase to high temperature phase (tetragonal and cubic) with the increase of Y2O3 content. The LIDT of stabilized thin film is more than that of unstabilized thin films. The reason is that ZrO2 material undergoes phase transition during the course of e-beam evaporation resulting in more numbers of defects compared to that of YSZ thin films. These defects act as absorptive center and the original breakdown points. (c) 2006 Elsevier B.V. All rights reserved.

High laser-induced damage threshold HfO2 films prepared by ion-assisted electron beam evaporation

HfO2 films were deposited by electron beam evaporation with different deposition parameters. The properties such as refractive index, weak absorption, and laser induced damage thresholds (LIDTs) of these films have been investigated. It was found that when pulsed Nd:YAG 1064 nm laser is used to investigate LIDT of films: Metallic character is the main factor that influences LIDTs of films obtained from Hf starting material by ion-assisted reaction, and films prepared with higher momentum transfer parameter P have fewer metallic character; The ion-assisted reaction parameters are key points for preparing high LIDT films and if the parameters are chose properly, high LIDT films can be obtained. (c) 2004 Elsevier B.V. All rights reserved.

1064nm倍频波长分离膜的制备与性能研究

通过对主膜系添加匹配层并借助计算机对膜系进行优化，设计出结构规整、性能优良的1064ilm倍频波长分离膜。用电子束蒸发及光电极值监控技术在K9玻璃基底上沉积薄膜，将样品置于空气中在260℃温度下进行3h热退火处理。然后用Lambda 900分光光度计测量了样品的光谱性能；用表面热透镜(STL)技术测量了样品的弱吸收值；用调Q脉冲激光装置测试了样品的抗激光损伤阈值(LIDT)。实验结果发现，样品的实验光谱性能与理论光谱性能有很好的一致性。退火前后其光谱性能几乎没有发生温漂，说明薄膜的温度稳定性好；同时退火使

高真空室中的水蒸气对HfO2薄膜性能的影响

本文研究了在镀膜过程中真空室内水蒸气的含量对HfO2薄膜物理性能的影响。用电子束蒸发和光电极值监控的方法在BK7基底上制备HfO2薄膜。利用残余气体分析仪在线监测了真空室内的残余气氛组成。分别用Lambda 900光谱仪、X射线衍射方法、表面热透镜技术和1064nm的激光器测试了薄膜的光学性能、微结构、吸收和激光损伤阈值。实验发现，附加冷阱装置有助于我们有效控制镀膜过程中的水汽含量，且在水蒸气含量较少的真空室内镀制的薄膜具有较高的折射率，较小的晶粒尺寸，较低的弱吸收值和较高的损伤阈值。

Comparison of TiO2 and ZrO2 films deposited by electron-beam evaporation and by sol-gel process

TiO2 and ZrO2 films are deposited by electron-beam (EB) evaporation and by sol-gel process. The film properties are characterized by visible and Fourier-transform infrared spectrometry, x-ray diffraction analysis, surface roughness measure, absorption and laser-induced damage threshold (LIDT) test. It is found that the sol-gel Elms have lower refractive index, packing density and roughness than EB deposited films due to their amorphous structure and high OH group concentration in the film. The high LIDT of sol-gel films is mainly due to their amorphous and porous structure, and low absorption. LIDT of EB deposited film is considerably affected by defects in the Elm, and LIDT of sol-gel deposited film is mainly effected by residual organic impurities and solvent trapped in the film.

Influence of annealing temperature on structure, optical loss and laser-induced damage threshold of TiO2 thin films

TiO2 thin films are prepared on fused silica with conventional electron beam evaporation deposition. After annealed at different temperatures for 4h, the spectra and XRD patterns of the TiO2 thin film are obtained. Weak absorption of coatings is measured by the surface thermal lensing technique, and laser-induced damage threshold (LIDT) is determined. It is found that with the increasing annealing temperature, the transmittance of TiO2 films decreases. Especially when coatings are annealed at high temperature over 1173K, the optical loss is very serious. Weak absorption detection indicates that the absorption of coatings decreases firstly and then increases, and the absorption and defects play major roles in the LIDT of TiO2 thin films.

Structural and optical properties of nanostructured TiO2 thin films fabricated by glancing angle deposition

TiO2 films deposited by electron beam evaporation with glancing angle deposition (GLAD) technique were reported. The influence of flux angle on the surface morphology and the microstructure was investigated by scanning electron microscopy. The GLAD TiO2 films are anisotropy with highly orientated nanostructure of the slanted columns. With the increase of flux angle, refractive index and packing density decrease. This is caused by the shadowing effect dominating film growth. The anisotropic structure of TiO2 films results in optical birefringence, which reaches its maximum at the flux angle alpha = 65 degrees. The maximum birefringence of GLAD TiO2 films is higher than that of common bulk materials. It is suggested that glancing angle deposition may offer an effective method to obtain tailorable refractive index and birefringence in a large continuous range. (c) 2006 Elsevier B.V. All rights reserved.

Preparation and characterization of nanostructured ZrO2 thin films by glancing angle deposition

ZrO2 films were prepared by electron beam evaporation with glancing angle deposition (GLAD) technique. The as-deposition and annealed ZrO2 films are all amorphous, different from that deposited at normal incidence. Due to the shadowing effect, a highly orientated structure composed of slanted columns formed, and the obtained films became the mixture of slanted columns and voids. The relationship among the effective refractive index, packing density and flux incident angle was investigated. The refractive index and packing density of ZrO2 films decrease with the increase of the incident angle. The in-plane birefringence of GLAD ZrO2 films was calculated. At the packing density of 0.576, the maximum birefringence is 0.037. (c) 2006 Elsevier B.V. All rights reserved.

Optical and electrical properties of TiOx thin films deposited by electron beam evaporation

The TiOx thin films were prepared by electron beam evaporation using TiO as the starting material. The effect of the annealing temperature on the optical and electrical properties was investigated. The spectra of X-ray photoelectron spectroscopy reveal that Ti in the films mainly exist in the forms of Ti2+ and Ti3+ below 400 degrees C 24h annealing. The charge transfer between different titanium ion contribute greatly to the color, absorption, and electrical resistance of the films. (c) 2006 Elsevier Ltd. All rights reserved.

Influence of oxygen plasma treatment on properties of ZrO2 films prepared by e-beam evaporation techniques

Zirconia films were prepared by e-beam evaporation, and oxygen plasma treatment was used to modify film properties. Spectrophotometry, x-ray diffractometry (XRD), and atomic force microscopy were used to characterize refractive index, extinction coefficient, rnicrostructure, and surface roughness, respectively. The experimental results indicate that both refractive index and extinction coefficient of the films were reduced slightly after oxygen plasma treatment, with the decrease of intrinsic stress and surface roughness. From XRD spectra, the intensity decrease of the T(110) diffraction peak was clearly observed after the treatment, which was caused by the restructuring of the film atoms. (C) 2008 Elsevier Ltd. All rights reserved.

Working pressure dependence of properties of Al2O3 thin films prepared by electron beam evaporation

The effects of working pressure on properties of Al2O3 thin films are investigated. Transmittance of the Al2O3 thin film is measured by a Lambda 900 spectrometer. Laser-induced damage threshold (LIDT) is measured by a Nd:YAG laser at 355nm with a pulse width of 7ns. Microdefects were observed under a Nomarski microscope. The samples are characterized by optical properties and defect, as well as LIDT under the 355 nm Nd: YAG laser radiation. It is found that the working pressure has fundamental effect on the LIDT. It is the absorption rather than the microdefect that plays an important role on the LID T of Al2O3 thin film.

Laser-induced damage of Ti O2 Si O2 high reflector at 1064 nm

A high laser-induced damage threshold (LIDT) TiO2/SiO2 high reflector (HR) at 1064 nm is deposited by e-beam evaporation. The HR is characterized by optical properties, surface, and cross section structure. LIDT is tested at 1064 nm with a 12 ns laser pulse in the one-on-one mode. Raman technique and scanning electron Microscope are used to analyze the laser-induced modification of HR. The possible damage mechanism is discussed. It is found that the LIDT of HR is influenced by the nanometer precursor in the surface, the intrinsic absorption of film material, the compactness of the cross section and surface structure, and the homogeneity of TiO2 layer. Three typical damage morphologies such as flat-bottom pit, delamination, and plasma scald determine well the nanometer defect initiation mechanism. The laser-induced crystallization consists well with the thermal damage nature of HR. (C) 2008 American Institute of Physics.

Al2O3/SiO2 films prepared by electron-beam evaporation as UV antireflection coatings on 4H-SiC

Al2O3/SiO2 films have been deposited as UV antireflection coatings on 4H-SiC by electron-beam evaporation and characterized by reflection spectrum, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The reflectance of the Al2O3/SiO2 films is 0.33% and 10 times lower than that of a thermally grown SiO2 single layer at 276 nm. The films are amorphous in microstructure and characterize good adhesion to 4H-SiC substrate. XPS results indicate an abrupt interface between evaporated SiO2 and 4H-SiC substrate free of Si-suboxides. These results make the possibility for 4H-SiC based high performance UV optoelectronic devices with Al2O3/SiO2 films as antireflection coatings. (C) 2007 Elsevier B.V. All rights reserved.