Thermal Stability of YBaCuO-Films Deposited by the Method of Laser Ablation

Russian Physics Journal - The influence of the rate of heating YBa2Cu3Oy films on the stability of their superconducting properties is investigated. The heating rate limit is identified, within...     

Study of Tb/Fe multilayers by temperature-dependent CEMS

A comparative study is accomplished in the domain where iron layers are amorphous. The dependence of the magnetic structure of Tb/Fe multilayered films on temperature have been investigated by Mössbauer spectrometry. When the iron layer is thinner than 2.3 nm, the average hyperfine field at the iron site remains nearly constant at 4.2 K, while it decreases strongly for iron thickness higher than 1.5 nm at room temperature. This decrease of H is due to the decrease of the Curie temperature, which can be explained from the structure of iron layers.     

直流磁控溅射沉积含He钛膜的研究

研究了用He/Ar混合溅射气体的直流磁控溅射制备钛膜中，He的掺入现象.分析结果表明，大量的He原子（He/Ti原子比高达56%）被均匀地引入到Ti膜中，其He含量可由混合溅射气体的He分量精确控制.通过调节溅射参数，可实现样品中He的低损伤引入.研究还发现，溅射沉积的含氦Ti膜具有较高的He成泡剂量和高的固He能力，这可能是溅射沉积形成了纳米晶Ti膜所致.纳米晶Ti膜较粗晶材料具有很高浓度的He捕陷中心，使He泡密度增大而泡尺寸减小.随He引入量的增加，Ti膜的晶粒尺寸减小，He引起的晶体点阵参数和X射线衍射峰宽度增大，晶体的无序程度增加.Helium trapping in the Ti films deposited by DC magnetron sputtering with a He/Ar mixture was studied. He atoms with a surprisingly high concentration (He/Ti atomic ratio is as high as 56%)incorporate evenly in deposited film. The trapped amount of He can be controlled by the helium partial amount. The introduction of the helium with no extra damage(or very low damage) can be realized by choosing suitable deposition conditions. It was also found that because of the formation of nanophase Ti film a relative high He flux for bubble formation is needed and the amount of the retain He in sputtering Ti films is much higher than that in the coarse grain Ti films. The nanophase Ti film can accommodate larger concentration of trapped sites to He, which results in a high density and small size of the He bubbles. With the increasing He irradiation flux, the grain size of Ti film decreases and the lattice spacing and width of the X ray diffraction peak increase due to the He introduction, and the film tends to amorphous phase.     

激光烧蚀法制备的纳米金属胶体及表面的特性研究

本文利用Nd∶YAG激光器1064nm激发光照射金、银等贵金属,通过改变激发光的照射时间,制备出各种金、银胶体。对上述胶体进行了透射电镜(TEM)测量金属粒子的尺寸大小及形态表明这些胶体为粒径介于5～25nm的纳米体系,并对该体系进行了紫外—可见—近红外吸收光谱的研究;在制备胶体的同时还获得了纳米级粗糙金属表面,对该表面进行了扫描电镜(SEM)的测量。     

Nanoparticles by Laser Ablation

This review concerns nanoparticles collected in the form of nanopowder or a colloidal solution by laser ablating a solid target that lies in a gaseous or a liquid environment. The paper discusses the advantages of the method as compared with other methods for nanoparticle synthesis, outlines the factors on which the properties of the produced nanoparticles depend, explains the mechanisms and models involved in the generation of nanoparticles by laser ablation, clarifies the differences between nanoparticle generation in gaseous and liquid environments, presents some experimental desigins and equipment used by the several groups for nanoparticle generation by laser ablation, describes the techniques used for “tuning” the width of the nanoparticles size distribution, and finally presents a few interesting examples of nanoparticles generated by laser ablation.     

CEMS analysis of Fe thin films

The application of the Conversion Electron Mössbauer Spectroscopy (CEMS) to the structural and magnetic analysis of ultrathin films and their interfaces is reported. Fe(110) films were deposited on W(110) under UHV conditions and analyzed in situ using CEMS. The changes ofB _hf from layer to layer across the film are discussed with respect to the modifications of magnetic properties caused both by the finite film thickness and by the specific electronic structure of the interfaces.     

脉冲激光沉积制备CsPbBr3厚膜及其蓝-绿光转换性能

金属卤化物钙钛矿CsPbBr3具有优异的光学性能,是作为波长转化层在液晶显示中实现全彩显示的理想材料。为了实现高效的蓝光到绿光的光转换,采用脉冲激光沉积技术(PLD)制备CsPbBr3微米级厚膜,通过设定激光脉冲数实现膜厚的有效调控,并借助扫描电子显微镜(SEM)、X射线粉末衍射(XRD)、紫外-可见吸收光谱等测试手段对其形貌、晶体结构和光学性质进行分析。然后,将CsPbBr3微米级厚膜沉积在发射波长为460 nm的蓝光发光二极管上,并测试光转换性能。实验结果表明,制备的CsPbBr3厚膜由(100)取向的柱状晶体组成,且膜厚与激光脉冲数呈线性关系,在膜厚为2.252μm时,在460 nm的蓝光激发下实现了完全、有效绿光的发射。此外,在空气氛围(温度20℃,湿度25%)下放置18 d,光致发光强度无明显衰退。     

脉冲激光沉积法在多孔铝衬底上生长的ZnO薄膜的结构与光学性质

ZnO是一种性质优良很有前途的紫外光电子器件材料,多孔铝是一种良好的模板型衬底,试图将二者结合起来以制备出一种全新的光电功能材料。制备了三种不同孔径多孔铝衬底,采用脉冲激光沉积法,在真空背景下,在多孔铝衬底上生长了氧化锌薄膜。利用扫描电子显微镜、X射线衍射和光致荧光对样品进行了测试和分析。研究表明:利用不同孔径的多孔铝衬底生长的氧化锌薄膜的结构和光学性质差异很大。样品A的光致发光主要是394nm的紫外发射和498nm的蓝绿光发射;样品B的光致发光主要是417nm的紫光发射和466nm蓝光发射;样品C的光致发光主要是415nm的紫光发射和495nm的蓝绿光发射。由于薄膜是富锌的,随着在空气中氧化的进行,光谱发生变化。利用固体能带理论对光谱进行了全面的分析。     

White Light Emission from ZnS:Mn Thin Films Deposited on GaN Substrates by Pulsed Laser Deposition

ZnS:Mn thin films are grown on GaN substrates by pulsed laser deposition.The structure,morphology and optical properties are investigated by x-ray diffraction,scanning electron microscopy and photoluminescence(PL).The obtained ZnS:Mn thin films are grown in preferred orientation along β-ZnS(111) direction corresponding to crystalline structure of cubic phase.The deposition temperature has an obvious effect on the structure,surface morphology and optical properties of ZnS:Mn thin films.PL measurements show that there are two emission bands located at 440 nm and 595 nm when the films are deposited at temperatures from 100℃ to 500℃.The relative integrated intensity of the blue emission and orange-red emission is determined by the deposition conditions.At the proper deposition temperature of 300℃,the color coordinate is closest to(0.33,0.33).The ZnS:Mn films on GaN substrates can exhibit white fight emission.     

化学浴沉积法制备CdS多晶薄膜

利用化学浴沉积法制备适合于铜铟镓硒薄膜太阳能电池缓冲层材料的CdS多晶薄膜,研究了在不同温度和不同时间下沉积薄膜的性质．薄膜生长开始由ion-by-ion机制控制,随着时间的进行,cluster-by-cluster机制占据主导．薄膜的生长速度随着沉积温度的升高而快速增加,直到达到饱和厚度．并且饱和厚度随温度升高而相应降低．SEM表明随沉积时间增加以及温度升高,薄膜表面形貌从多孔到粗糙的不均匀转变．XRD结果显示,薄膜由立方和六方两相结构组成,控制沉积时间对薄膜的主要晶相结构很关键．所有温度下沉积的CdS     

Nanoparticle Formation by Laser Ablation

The properties of nanoparticle aerosols of size ranging from 4.9nm to 13nm, generated by laser ablation of solid surfaces are described. The experimental system consisted of a pulsed excimer laser, which irradiated a rotating target mounted in a cylindrical chamber 4cm in diameter and 18-cm long. Aerosols of oxides of aluminum, titanium, iron, niobium, tungsten and silicon were generated in an oxygen carrier gas as a result of a reactive laser ablation process. Gold and carbon aerosols were generated in nitrogen by non-reactive laser ablation. The aerosols were produced in the form of aggregates of primary particles in the nanometer size range. The aggregates were characterized using a differential mobility analyzer and electron microscopy. Aggregate mass and number concentration, electrical mobility size distribution, primary particle size distribution and fractal dimension were measured. System operating parameters including laser power (100mJ/pulse) and frequency (2Hz), and carrier gas flow rate (1l/min) were held constant.A striking result was the similarity in the properties of the aerosols. Primary particle size ranged between 4.9 and 13nm for the eight substances studied. The previous studies with flame reactors produced a wider spread in primary particle size, but the order of increasing primary particle size follows the same trend. While the solid-state diffusion coefficient probably influences the size of the aerosol in flame reactors, its effect is reduced for aerosols generated by laser ablation. It is hypothesized that the reduced effect can be explained by the collision-coalescence mechanism and the very fast quenching of the laser generated aerosol.     

CEMS Study on Fe–Si–Al Alloy Flakes–Polymer Composites

Hyperfine Interactions - The composites of Fe–Si–Al alloy flakes and dielectric polymer fabricated for a new noise suppression filter in high-frequency bands were characterized by...     

Carbon Nitride Thin Films Deposited by Plasma Assisted Nd:YAG Laser Ablation of Graphite in N2+H2 Atmosphere

Carbon nitride thin films are deposited on silicon wafers by 532 nm Nd:YAG laser ablation of graphite in the N2+H2 atmosphere assisted by a dc glow discharge plasma at a higher gas pressure of about 4.0 kPa. The properties of the thin films are investigated by scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffraction (XRD). The results show that the deposited films are composed of α-C3N4, β-C3N4 phase and have the N/C atomic ratio of 2.01. The optical emission spectroscopy (OES) studies indicate that the introduction of a dc glow discharge and the adoption of a higher gas pressure during the film deposition are favorable to the net generation of the atomic N, CN radicals and N+2 in B2Σ+u excited state in the plasma, which are considered to play a major role in the synthesis of carbon nitride.     

激光等离子体效应对细胞烧蚀特性研究

研究对比了激光直接辐照、聚焦辐照以及激光等离子体辐照三种辐照方式下,洋葱表皮细胞的烧蚀特征,并基于激光辐照的热力学特性对细胞的温升以及相变过程进行分析。观察发现： 直接辐照对细胞的杀伤效果很不明显;聚焦辐照会引起焦点附近细胞的断裂以及脱水;激光等离子体辐照作用下,细胞会呈现大面积的去除,断裂边缘粗糙,且细胞层有叠加现象。理论分析发现,激光等离子体具有热效应、辐射电离及冲击波效应等,会增加激光脉冲能量到细胞的沉积、以及对细胞冲击剥离等,从而会大大增加细胞的杀伤范围和效率,可用于对细胞进行大面积杀伤。     

Study of Nanocrystalline Diamond Film Deposited Rapidly by 500 W Excimer Laser

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Study of Nanocrystalline Diamond Film Deposited Rapidly by 500 W Excimer Laser

High quality nanocrystalline diamond film deposited rapidly by an XeCl excimer laser operated at high laser power (500 W) and repetition rate (300～500 Hz) is presented. A high deposition rate, 250 nm/thousand pulses, was obtained. The effects of laser energy fluence and repetition rate on the deposition of diamond film were investigated.     

Ahnormal Crystallization of Silicon Thin Films Deposited by ICP-CVD

Silicon thin films are deposited by inductively coupled plasma chemical vapour deposition （ICP-CVD） at a low temperature of 350℃ using a mixture of SiH4 and H2. The structures of the films are characterized by x-ray diffraction and Raman spectra. Under the optimum experimental conditions, we observe that the crystallinity of Si films becomes more excellent and the preferred orientation changes from （111） to （220） with the decreasing dilution of SiH4 in H2. Such an abnormal crystallization is tentatively interpreted in term of the high density, low electron temperature and spatial confinement of the plasma in the process of ICP-CVD.     

GaSb基PECVD法制备SiO2薄膜的应力研究

为了实现在GaSb衬底上获得低应力的SiO₂薄膜,研究了等离子体增强化学气相沉积法（PECVD）在晶格失配较大的GaSb衬底上沉积SiO₂薄膜的应力情况。通过改变薄膜沉积时的工艺条件,如反应温度、射频功率、反应压强、气体流量比,并基于曲率法模型,对镀膜前后的曲率半径进行了实验测量,利用Stoney公式计算相关应力值并绘制应力变化曲线。详细讨论了PECVD工艺条件的改变对SiO₂薄膜应力所产生的影响。同时通过在Si衬底上沉积SiO₂薄膜,对比分析了导致薄膜应力产生的因素及变化过程。实验结果表明,在沉积温度为300℃、射频功率为20 W、腔体压强为90 Pa、气体流量比SiH₄/N₂O为125/70 cm³·min^-1的工艺参数下,PECVD法在GaSb衬底上沉积的SiO₂薄膜应力相对较小。