脉冲激光制备类金刚石薄膜及原位激光等离子体发射光谱

用ＹＡＧ脉冲激光轰击真空室内的石墨靶,可以形成包含碳素的激光等离子体,并在硅或石英衬氏上淀积形成某种类型的碳膜。用光学多道分析仪原位测量了激光等离子体的发射光谱,给出反应空间可能存在的反应基团有碳原子、碳离子、碳分子等,用拉曼光谱研究了薄膜的结构,证明所形成的薄膜为类金刚石膜,并得出碳原子和碳离子与薄膜的类金刚石结构有关。制备过程中,氢的参与有利于薄膜中金刚石成分的形成。空间分辨的原位激光等离子体发射光谱表明,在反应空间存在薄膜形成的最佳位置。     

新型软X-射线透射光栅光谱仪的研制

研制了一种新型的由带前置轮胎镜成像系统、高密度透射光栅和软Ｘ光ＣＣＤ相机等组成的软Ｘ射线光谱仪,摄谱范围为０．５－１．５ｎｍ,光谱分辩为为０．０５ｎｍ。光谱仪没有像散,实现了点对点成像。由于其高效率激光系统产生的等离子体Ｘ光谱,特别适合于超短飞秒强激光脉冲产生的等离子体的研究。     

薄膜靶整形强激光脉冲的理论分析和数值模拟

超强超短脉冲激光广泛应用于粒子加速以及新型X射线辐射源产生。较长的激光脉冲上升前沿直接影响激光应用效果。等离子体薄膜靶作为新型光学介质开关,可以有效降低超强激光脉冲前沿上升时间,优化激光等离子体相互作用参数。采用一维理论分析和粒子模拟方法研究了等离子体薄膜靶实现超强激光脉冲整形的机制。研究结果表明,薄膜靶通过对激光脉冲的非线性调制,可有效实现脉宽缩短和脉冲陡化;对比单层靶调制结果,选择参数优化的双层靶,可进一步优化脉冲整形效果,获得更短脉宽和更高振幅的激光脉冲;对于峰值振幅高于薄膜靶击穿阈值的超强激光,脉冲上升前沿可得到明显陡化,薄膜靶的击穿是产生这种脉冲整形效果的直接原因。     

XeCl（308nm）脉冲准分子激光淀积类金刚石薄膜

利用ＸｅＣｌ（３０８ｎｍ）脉冲准分子激光淀积技术在功率密度５×１０８Ｗ／ｃｍ２、室温、真空度１０－３Ｐａ的条件下，制备出不含氢成分的类金刚石薄膜，研究了类金刚石薄膜的特性及其随制备工艺条件的变化规律。研究了激光诱导的碳等离子体发射光谱，探讨了类金刚石薄膜的形成机理。     

脉冲激光烧蚀材料等离子体反冲压力物理模型研究与应用

分析了脉冲激光烧蚀材料等离子体等温膨胀阶段的物理特性,建立了脉冲激光烧蚀材料等离子体压力三维方程与动力学模型.应用所建模型,数值分析了单脉冲激光烧蚀青铜金刚石砂轮等离子体相关特性,得到等离子体的反冲压力最大值870 Pa出现在约25 ns后,距离砂轮表面距离约0.05 mm处.相关条件下开展脉冲激光烧蚀青铜金刚石砂轮试验,采用高速相机观测烧蚀砂轮过程中的飞溅现象;采用光栅光谱仪测量等离子体空间发射光谱,计算了等离子体电子温度、电子密度以及反冲压力.实验表明脉冲激光烧蚀青铜金刚石砂轮等离子体反冲压力可以不计,同时也验证了气体方程与动力学模型的正确性和可行性,对脉冲光纤激光烧蚀工艺优化具有启示意义.     

激光尾波场中光子加速研究

在SILEX-Ⅰ激光装置上,测量了超短超强激光脉冲与稀薄等离子体相互作用之后的透射谱. 实验中发现,激光尾波场产生的密度扰动导致等离子体折射率随时间空间不断变化,导致光子的加速/减速. 透射谱上主要表现为激光频率谱峰的劈裂和随密度变化的展宽,没有发现与前向受激拉曼散射或自调制不稳定性相联系的边频波. 同时,利用LPIC++无碰撞粒子模拟程序模拟了超短超强激光与稀薄等离子体相互作用后的透射谱,模拟结果也发现了明显的光子加速过程. 关键词： 超短超强激光脉冲 透射谱 光子加速/减速     

时空分布的超短激光脉冲烧蚀电介质材料时等离子体的产生

若考虑聚焦平面内固定区域,脉冲空间分布可简化为一维问题.在此基础上,从脉冲的传输过程出发,本文分析了时空分布的超短激光脉冲与电介质材料相互作用时等离子体形成模式.在材料内部累积的能量与脉冲宽度、与空间相关的损伤区域、等离子体形成时间及其吸收系数有关.     

激光诱导的钛酸钡等离子体的时间分辨光谱

利用光学多通道分析仪（ＯＭＡⅢ）研究脉冲激光沉积钛酸钡薄膜过程中的激光诱导等离子体的时间分辨发射光谱，利用各种粒子不同时刻发射的谱线强度描绘成该粒子的飞行时间谱，表征了等离子体中该粒子的空间浓度分布，根据飞行时间谱的特征，推算了粒子束脉冲（等离子体）的空间宽度及其与缓冲气体压力的关系，提出了在激光沉积多元氧化物薄膜过程中的合适的缓冲气体压力范围，解释了激光原位沉积高温超导薄膜中所需氧气分压达３０Ｐ     

超短超强激光在稀薄等离子体中的自聚焦传输

 开展超短超强激光与次稠密等离子体相互作用实验,采用探针光对激光等离子体相互作用区域进行阴影成像,研究了不同激光功率与临界功率比值及不同激光脉冲长度与等离子体波波长比值下的激光在次稠密等离子体中的自聚焦传输。结果表明:相对论效应是超短脉冲在次稠密等离子体中的主要自聚焦机制,激光功率与临界功率比值是影响超短脉冲在次稠密等离子体中形成自聚焦的关键条件。     

超短脉冲激光在均匀等离子体中的一维演化

研究了均匀等离子体中超短脉冲激光在传输过程中的脉宽、峰值功率随时间，空间变化的解析式，结果表明，对于２５ｆｓ左右的超短脉冲，由等离体色散引起的脉宽变长及峰值功率降低效应是明显的。     

飞秒激光制备硅窗口增透保护类金刚石膜

采用飞秒激光(800 nm,120 fs,3 W,1 000 Hz)制备类金刚石膜,研究了不同偏压、生长温度和氧气氛等辅助手段对激光沉积类金刚石膜的影响,实验发现在室温(25℃)、无偏压和低气压氧气氛(2 Pa)条件下沉积的类金刚石膜性能最优。在单面预镀普通增透膜的硅红外窗口材料上镀制出了无氢类金刚石膜,3~5μm波段平均透过率达到90%以上,纳米硬度高达40 GPa,用压力为9.8 N的橡皮磨头,摩擦105次,膜层未见磨损,并且通过了军标规定的高温、低温、湿热、盐雾等环境试验,所制类金刚石膜可对红外窗口起到较好的增透保护作用。     

高脉冲功率能量PLD法制备MgZnO薄膜中的沉积机理

用PLD法成功制备了一系列高质量的MgZnO薄膜。实验中发现高脉冲能量沉积薄膜的结构和发光特性随基片温度的变化规律与低脉冲能量下的结果不一样:基片在室温时高脉冲能量制备薄膜的XRD峰的半峰全宽比高基片温度时的结果相对更小;AFM显示其颗粒变大,柱状生长突出;PL谱紫峰与绿峰强度比最大,结晶质量反而提高。另一方面,与低脉冲能量时相反,增大氧气压强后高脉冲能量沉积的薄膜XRD半峰全宽变窄。结合实验现象和表征,合理解释了高脉冲能量沉积的机理。室温制备高质量MgZnO薄膜的PLD沉积机理对于以后在柔性衬底上沉积薄膜的研究有重要的参考价值。     

Nanosecond and femtosecond ablation of La0.6Ca0.4CoO3: a comparison between plume dynamics and composition of the films

Thin films of La_0.6Ca_0.4CoO₃ were grown by pulsed laser ablation with nanosecond and femtosecond pulses. The films deposited with femtosecond pulses (248 nm, 500 fs pulse duration) exhibit a higher surface roughness and deficiency in the cobalt content compared to the films deposited with nanosecond pulses (248 nm, 20 ns pulse duration). The origin of these pronounced differences between the films grown by ns and fs ablation has been studied in detail by time-resolved optical emission spectroscopy and imaging. The plumes generated by nanosecond and femtosecond ablation were analyzed in vacuum and in a background pressure of 60 Pa of oxygen. The ns-induced plume in vacuum exhibits a spherical shape, while for femtosecond ablation the plume is more elongated along the expansion direction, but with similar velocities for ns and fs laser ablation. In the case of ablation in the background gas similar velocities of the plume species are observed for fs and ns laser ablation. The different film compositions are therefore not related to different kinetic energies and different distributions of various species in the plasma plume which has been identified as the origin of the deficiency of species for other materials.     

射频磁控溅射法制备高质量ZnO薄膜的激光特性研究

用射频磁控溅射方法在SiO2衬底上制备ZnO薄膜。在室温下观测到了A、B激子吸收以及在19K下发现的A、B、C激子的反射表明所制备的ZnO薄膜具有很好的纤锌矿结构。我们获得了来自于电子空穴等离子体的受激发射。进一步研究我们发现由大量窄峰所组成的激光发射，窄峰的间距都为0.5nm左右。根据理论计算，产生激光发射的自成腔的长度为31.5 μm。我们认为ZnO薄膜中产生激光发射的自成腔的形成与其六角型结构有重要关系。     

Pulsed laser deposition and characterization of multilayer metal-carbon thin films

Cobalt-DLC multilayer films were deposited with increasing content of cobalt, keeping carbon content constant by pulsed laser deposition technique. A cobalt free carbon film was also deposited for comparison. Excimer laser was employed to ablate the materials onto silicon substrate, kept at 250 °C, while post-deposition annealing at 400 °C was also performed in situ. The formation of cobalt grains within the carbon matrix in Co-DLC films can be seen through scanning electron and atomic force micrographs while no grains on the surface of the cobalt-free DLC film were observed. Raman spectra of all the films show D- and G-bands, which is a confirmation that the films are DLC in nature. According to Vibrating sample magnetometer (VSM) measurements, the DLC films with cobalt revealed ferromagnetic behaviour whereas the cobalt free DLC film exhibited diamagnetic behaviour. The pure DLC film also shows ferromagnetic nature when diamagnetic background is subtracted. Spectroscopic Ellipsometry (SE) analysis showed that the optical band gaps, refractive indices and extinction coefficients of Co-DLC films can be effectively tuned with increasing content of cobalt.     

193-nm laser ablation of CVD diamond and graphite in vacuum: plume analysis and film properties

The pulsed laser ablation of chemical vapor deposition (CVD) diamond and graphite samples in vacuum has been investigated by the use of an ArF excimer laser operating at 5=193 nm. The composition and propagation of both ablation plumes has been probed via wavelength and spatially and temporally resolved measurements of the plume emission and found to be very similar. Electronically excited C atoms and C⁺ and C²⁺ ions are identified among the ablated material. Plume expansion velocities are estimated from time-gated imaging of specific C and C⁺ emissions. Langmuir probe measurements provide further insight into the propagation of the charged components in both ablation plumes. Diamond-like carbon (DLC) films grown by 193-nm laser ablation of both target materials on Si substrates maintained at room temperature have been investigated by laser Raman spectroscopy (325 nm and 488 nm excitation) and by both optical and scanning electron microscopy, and their field emission characteristics investigated. Again, similarities outweigh the differences, but DLC films grown from ablation of the diamond target appear to show steeper I/V dependencies once above the threshold voltage for field emission.     

利用脉冲激基分子激光制备大尺寸类金刚石薄膜及其均匀性分析

利用脉冲激光沉积结合计算机辅助衬底扫描技术制备了尺寸为70×66mm、均匀性为±5%的类金刚石薄膜,薄膜显微硬度最高为27GPa,薄膜结合强度达到20000转;在制备大尺寸薄膜的过程中,衬底扫描速度越慢,薄膜的均匀性越好;在应用传统清洗等方法的基础上,认为增大镀膜粒子的能量对于提高薄膜和衬底的结合强度是非常重要的.     

Effects of laser fluence on the structural properties of pulsed laser deposited ruthenium thin films

Ruthenium (Ru) has received great interest in recent years for applications in microelectronics. Pulsed laser deposition (PLD) enables the growth of Ru thin films at low temperatures. In this paper, we report for the first time the characterization of pulsed laser deposited Ru thin films. The deposition processes were carried out at room temperature in vacuum environment for different durations with a pulsed Nd:YAG laser of 355-nm laser wavelength, employing various laser fluences ranging from 2 J/cm² to 8 J/cm². The effect of the laser fluence on the structural properties of the deposited Ru films was investigated using surface profilometry, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Ru droplets, some spherical in shape and some flattened into round discs were found on the deposited Ru. The droplets were correlated to ripple formations on the target during the laser-induced ejection from the target. In addition, crystalline Ru with orientations of (100), (101), and (002) was observed in the XRD spectra and their intensities were found to increase with increasing laser fluence and film thickness. Grain sizes ranging from 20 nm to 35 nm were deduced using the Scherrer formula. Optical emission spectroscopy (OES) and energy-dispersive X-ray spectroscopy (EDS) show that the composition of the plume and the deposited Ru film was of high purity.     

激光诱导Al等离子体在背景气体中的流体现象

调Q-YAG脉冲激光（波长1.06μm,脉宽10ns,能量为250mJ/pu1se）烧蚀Al靶,用短焦距照相系统和光学多道分析仪（OMA）记录了等离子体在氩气背景气体及不同压强下所呈现的流体现象及其等离子体辐射的空间分辨光谱。实验发现,当背景气压为400Pa以下时,在靶面上存在一个明亮的发光球体,球体直径远大于激光烧蚀斑的大小,此球体向四周辐射等离子体光谱,只是在垂直靶面的方向辐射相对较强。在气压约为400Pa,等离子体辐射才以较为明显的羽状体形态向前喷散,且随气压增高,喷散的立体角变小。随着背景气压的继续升高,等离子体羽被压缩,成为一个明亮的发光小羽状体,当气压达20～30kPa,发光羽状体开始出现分解的迹象,在羽状体前端形成一个光球。气压继续升高,等离子体羽完全变成一串发光球。离开靶面越远,发光球的半径越大。用光学多道分析系统分析这些发光球的光谱特征,发现在靶面附近主要是Al等离子体的谱线,而较远的发光球,其主要谱线则来自背景气体。在气压为20kPa左右,等离子休羽呈现烧蚀点为明亮的白色亮点,而羽端为鲜艳绿色（氩的514nm）的彩色羽。