A comparative study of the UV optical and structural properties of SiO2, Al2O3, and HfO2 single layers deposited by reactive evaporation, ion-assisted deposition and plasma ion-assisted deposition

Growing requirements for the optical and environmental stability, as well as the radiation resistance against high-power laser radiation, especially for optical interference coatings used in the ultraviolet spectral range, have to be met by new, optimised, thin-film deposition technologies. For applications in the UV spectral range, the number of useful oxide thin film materials is very limited due to the higher absorption at wavelengths near to the electronic bandgap of the materials. Applying ion-assisted processes offers the ability to grow dense and stable films, but in each case careful optimisation of the deposition process (evaporation rate, substrate temperature, bombarding gas, ion energy and ion current density) has to achieve a balance between densification of the layers and the absorption. High-quality coatings and multilayer interference systems with SiO₂ as the low-index material can be deposited by various physical vapour deposition technologies, including reactive e-beam evaporation, ion-assisted deposition and plasma ion-assisted deposition. In order to improve the degradation stability of dielectric mirrors for use in UV free-electron laser optical cavities, a comparative study of the properties of SiO₂, Al₂O₃ and HfO₂ single layers was performed, and was addressed to grow very dense films with minimum absorption in the spectral range from 200 to 300 nm. The films were deposited by low-loss reactive electron-beam evaporation, by ion-assisted deposition using a ‘Mark II’ ion source, and by plasma ion-assisted deposition using the advanced plasma source. Optical and structural properties of the samples were studied by spectral photometry, infrared spectroscopy, X-ray diffraction and reflectometry, as well as by investigation of the surface morphology. The interaction of UV radiation with photon energy values close to the bandgap was studied. For HfO₂ single layers, laser-induced damage thresholds at 248 nm were determined in the 1-on-1 and 1000-on-1 test modes as a function of the deposition technology and film thickness.     

Properties of BGO thin films under the influence of gamma radiation

It is important to know the behaviour of materials under the influence of radiation for the effective design of novel sensor systems. Optical properties of bismuth germinate (Bi₄Ge₃O₁₂—BGO) thin films were investigated in terms of their perception to gamma radiation exposure. An Edwards E306A vacuum thermal coating system was used for thin films deposition. BGO films with a thickness of 200 nm were exposed to a disk-type ¹³⁷Cs gamma radiation source with an activity of 370 kBq. Optical properties of the films were investigated using CARY IE UV-Visible Spectrophotometer. Calculated optical band gap for as-deposited BGO thin film was 1.95 eV. Gamma radiation induced changes in the optical properties of thin films, which could be explained by the variation in the degree of disorder. From the density-of-state model, it is known that optical band gap decreases with an increasing degree of disorder of the amorphous phase.Electrical properties of BGO thin films were recorded in real time using a low power capacitive interface system with a high resolution, which is based on Delta-sigma modulator. At doses from 0 to 1.5 mGy little if any changes in the capacitance were measured. This could be explained by co-existence of two processes, namely creation and annihilation of defects under the influence of radiation. After a threshold dose of 1.5 mGy creation of defects becomes more prevailing and the BGO film capacitance has gradually increased in value from 2.97 pF to 7.09 pF after irradiation with a 2.44 mGy dose.     

Effects of gamma radiation on perfluorinated polymer optical fibers

The paper presents the first complex study of gamma radiation effects on a low-loss perfluorinated polymer optical fiber (PF-POF) based on Cytop^® polymer. Influence of gamma radiation on fiber’s optical, mechanical and climatic performance is investigated. The radiation-induced attenuation (RIA) in the visible and near-infrared region (0.4 μm–1.7 μm) is measured and its origins are discussed. Besides attenuation increase, radiation is also shown to decrease the thermal degradation stability of the fiber and to increase its susceptibility to water. With regard to complex fiber transmission performance upon irradiation, the optimal operation wavelength region of PF-POF-based systems intended for use in radiation environments is determined to be around 1.1 μm. On the other hand, the investigated fiber holds potential for low-cost RIA-based optical fiber dosimetry applications with sensitivity as high as 260 dBm⁻¹/kGy in the visible region.     

玻璃空间电离辐照着色损伤动力学研究

空间电离辐照主要由能量连续变化的粒子组成, 绝大多数粒子穿透能力小, 因此, 空间电离辐照对玻璃的着色损伤必然随深度而呈现一种复杂的变化, 针对这一现象, 并且考虑到玻璃中色心的弛豫消失, 本工作建立了一种适用于玻璃空间电离辐照着色损伤动力学研究的方法. 以K9-HL玻璃为研究对象, 利用空间电离辐照作用在玻璃中随深度变化的Monte Carlo模拟结果, 研究了该玻璃在轨(近地点350 km, 远地点425 km, 轨道倾角51.6°)电离辐照着色损伤过程, 讨论了航天器用玻璃抗辐照性能考核方法, 分析了玻璃空间电离辐照着色损伤的深度分布, 提出了航天器用玻璃材料抗电离辐照损伤加固的关键点. 此外, 对不同石英玻璃防电离辐照层保护的K9-HL玻璃在轨光学性能做了研究.     

Effect of gamma radiation on optical and electrical properties of tellurium dioxide thin films

Gamma radiation induced changes in the optical and electrical properties of tellurium dioxide (TeO₂) thin films, prepared by thermal evaporation, have been studied in detail. The optical characterization of the as-deposited thin films and that of the thin films exposed to various levels of gamma radiation dose clearly show that the optical bandgap decreases with increase in the gamma radiation dose up to a certain dose. At gamma radiation doses above this value, however, the optical bandgap has been found to increase. On the other hand, the current vs voltage plots for the as-deposited thin films and those for the thin films exposed to various levels of gamma radiation dose show that the current increases with the gamma radiation dose up to a certain dose and that the value of this particular dose depends upon the thickness of the film. The current has, however, been found to decrease with further increase in gamma radiation dose. The observed changes in both the optical and electrical properties indicate that TeO₂ thin films can be used as the real time gamma radiation dosimeter up to a certain dose, a quantity that depends upon the thickness of the film.     

Effect of UV‐Radiation on the Packaging‐Related Properties of Whey Protein Isolate Based Films and Coatings

The high oxygen barrier properties of whey protein based films and coatings means these materials are of great interest to the food and packaging industry. However, these materials have poor mechanical properties such as the tensile strength, Young's modulus and elongation at break. Up until now, the influence of ultraviolet (UV) radiation on whey protein films has not been reported in the literature. This study thus investigates the influence of UV‐radiation on the properties of whey protein based films. UV‐irradiated films showed increased tensile strength and a yellowing that was dependent on the radiation time. After irradiation, the films showed no significant change in the barrier properties, Young's modulus or elongation at break. In addition, a protein solubility study was undertaken to characterize and quantify changes in structure‐property relationships. The significant decrease in protein solubility in buffer systems which break disulfide and non‐covalent bonds indicates that additional molecular interactions arise with increasing radiation dose. This study provides new data for researchers and material developers to tailor the characteristics of whey protein based films according to their intended application and processing. Copyright © 2015 John Wiley & Sons, Ltd.     

The effects of PEG assisted synthesis and zinc addition on gamma irradiated bioactive glasses

Zinc containing bioactive glasses were prepared by means of sol–gel procedure, in the presence of polyethylene glycol (PEG) considered as surfactant agent. Fourier transform infrared spectroscopy (FTIR), UV–Vis absorption spectroscopy and electron paramagnetic resonance spectroscopy (EPR) were employed to reveal the bioactive glass response to gamma irradiation in terms of defects generation. The results proved that gamma irradiation induces structural changes within the glass matrix, which are strongly dependent on the sample composition. ZnO addition to the glasses network was found to confer structural stability against gamma irradiation, while the use of PEG during the samples preparation favoured the generation of network defects especially in ZnO containing samples.     

Electrical conductivities and dielectric constants of some sodium tetraborate glasses containing CuO, irradiated with a low-level fast neutron beam

A number of glass samples were prepared from a mixture of Na2B4O7 and CuO. The prepared glasses were irradiated with a low-level fast neutron beam (flux density 108 n cm-2). The alternating current (a.c.)-electrical conductivity and the dielectric constant at a frequency of 1 kHz of these glasses have been studied as a function of temperature in the range 300–600 K. The measurements showed that an amorphous–crystalline phase transition characterized these samples. This phase transition was affected by neutron irradiation. Also a decrease in the activation energy for the irradiated undoped sample and an increase in the activation energy for the irradiated doped samples were found. After irradiation, the maximum peak, which characterized the dielectric constant of the samples before irradiation, disappeared. © 1998 Chapman & Hall     

Stability,UV shielding properties,and light conversion behavior of Eu(BMDM)3@polysiloxane nanoparticles in water and polyurethane films

Bifunctional Eu(BMDM)₃@polysiloxane nanoparticles were prepared through reprecipitation–encapsulation methods using 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedione (BMDM) ligand and octyltrimethoxysilane (OTS) precursor and embedded into waterborne polyurethane (PU) coatings to fabricate transparent optical composite films. The photostability and thermostability of the nanoparticles in water and their ability to block UV and convert light when embedded in PU films were investigated. In comparison with the control Eu(BMDM)₃ nanoparticles, the Eu(BMDM)₃@polysiloxane nanoparticles, especially those prepared at a Eu(BMDM)₃/OTS mole ratio of 1:2, exhibited far superior stability under storage conditions, UV irradiation, and heating. They also showed excellent UV-shielding and highly efficient light conversion properties because of the protective polysiloxane.     

Studies of radiation defects in cerium,europium and terbium activated oxyfluoride glasses and glass ceramics

Terbium, cerium and europium activated oxyfluoride glasses and glass ceramics have been studied by thermally stimulated luminescence (TSL) and optical absorption techniques after the X-ray irradiation. A creation of colour centres in oxyfluoride glass matrix and TSL peaks depending on the activator type were observed. LaF₃ and rare earth activators were analysed by SEM–EDS.     

具有超亲水光催化性能的λ/4-λ/2型两层宽频增透膜的制备和性能研究

以多孔SiO₂/TiO₂复合膜为膜层材料, 采用溶胶-凝胶法制备得到λ/4-λ/2型无峰两层宽频增透膜, 此工艺制备过程简, 单且对膜层折射率要求较低, 镀制两层膜的K9基片在500~700 nm波段维持较高的透过率, 在此区间透过率平均值为99.4%, 在可见光区400~800 nm的平均透过率为99.0%。两层膜表现出优异的超亲水性能, 在无需紫外光照的条件下, 其在0.5 s的水接触角仅为2.2°, 且超亲水性能能够维持超过20 d。同时, 两层膜表现出一定的光催化降解有机污染物的能力。     

Effects of laser irradiation on the structure and optical properties of ZnO thin films

The effects of laser irradiation on the surface microstructure and optical properties of ZnO films deposited on glass substrates were investigated experimentally and compared with those of thermal annealing. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements showed that the irradiation treatment with an Ar⁺ laser of 514 nm for 5 min improves the crystalline quality of ZnO thin films through increasing the grain size and enhancing the c-axis orientation, with the effects similar to those of the thermal annealing at 500 °C for 1 h. Laser irradiation was found to be more effective both for the relaxation of the residual compressive stress in the as-grown films and for the modification of the surface morphology. A significant increase in the UV absorption and a widening in the optical band-gap of the films were also observed after laser irradiation.     

Refractive-index changes caused by proton radiation in silicate optical glasses

We have studied experimentally, by using a differential interferometric technique, the effect of proton radiation on the refractive index of commercial (Schott) silicate crown glasses, BK7 and LaK9, and their radiation-resistant counterparts. The strongest effect was observed for the radiation-hard lanthanum crown LaK9G15: At a 0.65-Mrad dose the index change was approximately 3 x 10(-5). Radiation-hard glasses are used in optical systems operating in radiation environments because they prevent spectral transmission degradation in the visible. However, such glasses are not protected against radiation-induced refractive-index perturbations, and a diffraction-limited optical system based on such glasses may fail owing to radiation-induced aberrations.     

Formation and thermo-assisted stabilization of luminescent silver clusters in photosensitive glasses

Various photo-induced silver luminescent centres were obtained in photosensitive zinc and phosphate glasses containing silver ions after exposure to gamma or ultraviolet nanosecond pulsed-laser radiation. Gamma-irradiation of the glasses results mainly in the formation within the glass of electron-trapped and hole-trapped silver centres as evidenced by optical absorption, luminescence and electron spin resonance spectroscopies. For the highest irradiation doses silver clusters are obtained. Under ultraviolet nanosecond pulsed-laser exposure similar species are generated along the beam propagation direction as proven by the analogous optical and luminescence signatures. In this case for high irradiation doses few silver clusters are created. The evolution of the luminescence spectra with respect to the temperature and to the duration of the heat treatment after ultraviolet nanosecond pulsed-laser irradiation evidences the presence of potential barriers determining the stability limits of some species such as the Ag²⁺ hole-trapped centres or the Ag_m^x+ clusters composed of silver ions and silver atoms. A heat treatment of several hundreds of degrees is identified as a the key parameter for tailoring the optical properties and controlling the formation of Ag_m^x+ clusters in the photosensitive glasses.     

纳米TiO_2-WO_3复合涂层及纳米TiO_2/WO_3叠层涂层的制备及性能

为了解决电子池材料改性TiO2涂层暗态下无阴极保护作用的问题,用溶胶-凝胶法及浸渍提拉技术在304不锈钢表面制备了纳米TiO2-WO3复合涂层与纳米TiO2/WO3叠层涂层,用扫描电镜(SEM)、X射线光电子能谱仪(XPS)研究了2种涂层的表面形貌、成分,并用电化学方法研究了2种涂层的光阴极保护特性及耐腐蚀性能。结果表明:2种涂层表面均连续均匀,由Ti,W,O,C组成;紫外光照1 h时2种涂层均对304不锈钢有一定的光阴极保护作用,闭光后纳米TiO2/WO3叠层涂层的延时阴极保护作用远好于纳米TiO2-WO3复合涂层;2种涂层均对304不锈钢有防腐蚀作用,紫外光照射时纳米TiO2-WO3复合涂层的防腐蚀性比纳米TiO2/WO3叠层涂层的好。     

Thermal, structural, optical, and dielectric properties of (100 - x)Li2B4O7 - x(BaO-Bi2O3-Nb2O5) glasses and glass-nanocrystal composites

Transparent glasses in the system (100 - x)Li2B4O7 - x(BaO-Bi2O3-Nb2O5) (x = 10, 20, and 30) were fabricated via the conventional melt-quenching technique. The amorphous and glassy characteristics of the as-quenched samples were established by the differential thermal analyses (DTA) and X-ray powder diffraction (XRD) studies. Glass-nanocrystal composites (GNCs) i.e., the glasses embedded with BaBi2Nb2O9 (BBN) nanocrystals (10-50 nm) were produced by heat-treating the as-quenched glasses at temperatures higher than 500 degrees C. Perovskite BBN phase formation through an intermediate fluorite-like phase in the glass matrix was confirmed via XRD and transmission electron microscopic (TEM) studies. The optical transmission properties of these GNCs were found to have a strong compositional (BBN content) dependence. The refractive index (n = 1.90) and optical polarizability (alphao = 15.3 x 10(-24) cm3) of the GNC (x = 30) were larger than those of as-quenched glasses. The temperature dependent dielectric constant (epsilonr) and loss factor (D) for the glasses and GNCs were determined in the 100-40 MHz frequency range. The epsilonr was found to increase with increase in heat-treatment temperatures, while the loss of the glass-nanocomposites was less than that of as-quenched glasses. The sample heat-treated at 620 degrees C/1 h (x = 30) exhibited relaxor behavior associated with a dielectric anomaly in the 150-250 degrees C temperature range. The frequency dependence of the dielectric maximum temperature was found to obey the Vogel-Fulcher relation (Ea = 0.32 eV and Tf = 201 K).     

Absorptance behavior of optical coatings for high-average-power laser applications

A modified photothermal deformation technique is used to measure the absorptance behaviors of optical multilayered dielectric coatings for a high-power laser system. The surface thermal-lensing modification uses an enlarged probe beam to facilitate alignment of the laser beam and data acquisition. The coatings, both reflective and transmissive types, are made by a physical vapor-deposition process. Coating absorptances are observed to depend on the laser's exposure time and power density. Time-dependent absorptance defect models are proposed. Also, micrometer-sized sites of high absorptance and an area with physical damage can be found during the spatial scans. It is proposed that absorptance values reported for coatings in high-repetition-rate or cw-laser systems include time- and power-dependent behaviors in addition to other relevant irradiation parameters.     

Effect of ionizing radiation on optical and lasing properties of Y3Al5O12 single crystals doped with Nd, Er, Ho, Tm, Cr ions

The influence of gamma irradiation on optical and lasing properties of YAG:Er, YAG:CTH, YAG:Nd and YAG:Cr⁴⁺ single crystals were studied. For no thermal annealed rods from YAG:Er and YAG:CTH crystals the increase of laser output energy was established. The mechanisms of radiation sensibilization are discussed.     

玻璃空间电离辐照着色研究

对几种玻璃(K9-HL玻璃、JGS3石英玻璃、K509玻璃以及JGS1石英玻璃)在电离辐照(质子、电子)作用下的光学稳定性进行了系统研究, 并以此为基础, 通过空间电离辐照在玻璃作用的模拟计算, 对这几种玻璃在轨(近地点350 km, 远地点425 km, 轨道倾角51.6^o)光学寿命进行了预测. 在该轨道使用10年时, K9-HL玻璃可见光透过率可能出现明显下降, 而JGS3石英玻璃、K509玻璃以及JGS1石英玻璃的可见光透过率保持不变或变化很小. 由于绝大多数空间粒子穿透能力小, 空间电离辐照仅能造成玻璃表层的着色. 因此, 长期在轨航天器舷窗可加一防电离辐照层以减少内层玻璃接受的电离辐照量, 而该层玻璃可采用石英玻璃.