长脉冲Nd:YAG激光器的实验研究

报道重复频率 １ｋ Ｈｚ 的长脉冲 Ｎｄ： Ｙ Ａ Ｇ 激光器,实验研究了氪灯的发光特性和激光脉冲特性。当激光的重复频率为 １ｋ Ｈｚ、占空比为 ５０％ 时,激光平均功率为 ６３ Ｗ ,峰值功率为 １２６ Ｗ 。     

氧压与ZnO薄膜发光特性的关系研究

在不同的环境氧压下用脉冲激光沉积方法在Si(111)衬底上生长了ZnO薄膜,以325 nm He-Cd激光器为激发源获得了薄膜的荧光光谱以研究其发光特性,用X射线衍射仪(XRD)和原子力显微镜(AFM)研究了薄膜的晶体结构和表面形貌,结果表明氧压在20 Pa和50Pa之间制备的ZnO薄膜具有良好的紫外发光特性和较好的晶体质量.分析了ZnO薄膜的发光机理,认为薄膜紫外峰源自自由激子复合发光,绿光峰的发光机制与锌位氧OZn关系密切,氧空位是蓝光发射的重要原因.     

激光刻蚀柔性薄膜太阳电池复合背反射层的研究

柔性聚酯膜衬底薄膜电池通过激光刻蚀等工艺形成集成串联,激光刻蚀柔性薄膜太阳电池复合背反射层(Ag/ZnO)是其中的重要工艺。首先对聚酰亚胺(PI)、Ag、ZnO材料的光学特性进行了分析,然后采用1 064nm脉冲激光与532nm脉冲激光分别对柔性薄膜太阳电池复合背反射层进行刻蚀研究。通过改变重复频率、激光功率、扫描速度和焦点位置等参数,分析了激光刻蚀物理机制,获得了好的刻蚀效果。结果表明,1 064nm纳秒脉冲激光更适合刻蚀柔性PI衬底复合背反射层Ag/ZnO,在激光功率860mW、刻蚀速度800mm/s和重复频率50kHz下,获得了底部平整、两侧无尖峰的刻线,刻线宽为32μm,满足柔性薄膜太阳电池集成串联组件的制备工艺要求。     

激光能量对脉冲激光沉积法制备ZnO薄膜性能的影响

脉冲激光沉积技术(PLD)易于获得高质量的氧化物薄膜已成为一种重要的制备ZnO薄膜的技术.采用脉冲激光沉积(PLD)(KrF准分子激光器:波长248 nm,频率5 Hz,脉冲宽度20 ns)方法在氧气气氛中以高纯Zn(99.999%)为靶材、在单晶硅和石英衬底表而成功生长了ZnO薄膜.通过X射线衍射仪、表面轮廓仪、荧光光谱仪、紫外可见分光光度计对合成薄膜材料的晶体结构、厚度、光学性质等进行了研究,分析了激光能量变化对其性能的影响.实验结果表明我们使用PLD法可以制备出(002)结晶取向和透过率高于75%的ZnO薄膜,激光能量为450 mJ的ZnO薄膜的发射性能较好,但激光能量的增加不能改善薄膜的透光率.     

能量密度和重复频率对PLD法制备ZnS薄膜性质的影响

利用脉冲激光沉积法在玻璃基片上、以不同的能量密度和重复频率制备了一系列ZnS薄膜。利用X射线衍射、X射线能量色散谱、紫外-可见-近红外分光光度计,对ZnS薄膜的晶体结构、化学组分、光学特性等进行表征。结果表明:所制备ZnS薄膜为富硫贫锌,结晶质量良好,为(002)晶面择优取向生长。能量密度为7.5 J/cm~2、重复频率为2 Hz是生长高质量ZnS薄膜的条件,其所制备的ZnS薄膜为纤锌矿结构,结晶程度最高,择优取向度最高(189.2),Zn/S摩尔比值接近化学计量比,堆积密度最大(0.967),可见光透过率高,禁带宽度为3.55 eV。     

基于国产大模场面积双包层光纤的高重复频率纳秒脉冲光纤放大器

以单模1064 nm激光二极管(LD)光纤级联放大构成的全光纤化模块为种子光源,以国产大模场面积(LMA)双包层掺镱光纤为放大器,构成了高重复频率纳秒脉冲主振荡功率放大(MOPA)系统.实现了平均功率为59 W的脉冲放大激光输出,中心波长1064 nm,脉冲宽度22.7 ns(重复频率50 kHz时),重复频率50～150 kHz连续可调.实验研究了激光脉冲的时域和光谱特性,分析了光纤功率放大对激光脉冲波形的影响.     

脉冲激光溅射沉积YBCO超导薄膜

从激光与材料相互作用理论出发,分析了激光烧蚀材料等离子体羽辉的空间运动特征和成分分布;以YBCO/SrTiO_3为对象,从实验上系统研究了脉冲激光溅射沉积薄膜过程中薄膜质量与基片温度、基片-靶材距离、气体压强、激光脉冲能量以及重复频率等参数的关系;总结出在SrTiO_3(100)单晶基片上溅射沉积YBCO高温超导薄膜的最佳实验参数。     

沉积速率对硅基LiNbO3光波导薄膜特性的影响

利用脉冲激光沉积技术(PLD)在硅衬底上生长高c轴取向LiNbO3晶体薄膜,研究了激光脉冲频率即薄膜沉积速率对薄膜结晶质量及取向性的影响,发现激光脉冲频率对薄膜的c轴取向性基本没有影响,但对薄膜的结品质量影响较大,激光脉冲频率为3 Hz时获得了高结品质量的c轴取向LiNbO3晶体薄膜.XPS测试表明制得薄膜的组分符合等化学计量比,AFM测试显示制备的薄膜表面光滑,表面粗糙度为4.3 nm.棱镜耦合法测试表明制备的LiNbO3薄膜具有优异的光波导性能,光传输损耗为1.14 dB/cm.     

激光能量及重复频率对土壤等离子体特性的影响

利用波长为1064 nm的Nd∶YAG脉冲激光器作光源,以高分辨率、宽光谱段的中阶梯光栅光谱仪和增强型电荷耦合器件(ICCD)作为谱线分离与探测器件,测量并分析了激光能量及重复频率对土壤中铅元素激光诱导击穿光谱特性的影响。实验结果表明,随着激光脉冲能量(在25~105 mJ范围内)增加,谱线强度呈线性增加,随后谱线强度随脉冲能量(105~165 mJ)的变化呈非线性关系。信背比随激光能量的增加而增大,但激光能量超过60 mJ后基本上不变。激光重复频率为1 Hz时,谱线强度最大,而谱线强度的相对标准偏差则在重复频率为7 Hz时最小。     

ZnS/PS体系的结构和发光特性

用电化学阳极氧化法制备了不同孔隙率的多孔硅(PS)样品,然后用脉冲激光沉积(PLD)法在其表面生长ZnS薄膜,研究ZnS/Ps复合体系的结构和发光特性.X射线衍射仪(XRD)结果表明,ZnS薄膜的生长具有高度择优取向,在28.5°附近有一很强的衍射峰,对应于β-ZnS(111)晶向.扫描电子显微镜像(SEM)显示,ZnS薄膜表面很不平整并出现空洞,这是由于衬底PS的表面粗糙所致.ZnS/PS复合体系的光致发光(PL)谱的高斯拟合分峰表明,随着衬底孑L隙率的增大,在样品B和C的发光谱中,在光谱中间520 nm左右都出现了一个新的绿色发光峰,归因于ZnS的缺陷中心发光.位于480 nm附近的ZnS的蓝光和520 nm附近的ZnS的绿光以及位于600 nm处的PS的橙红光叠加在一起,整个znS/PS复合体系呈现出较强的白光.     

Origin of room-temperature ferromagnetism in cobalt-doped ZnO

Thin films of ZnO doped with cobalt have been grown by the pulsed laser deposition (PLD) technique in different temperatures ranging from 500°C to 650°C. The films grown on sapphire c-plane single crystal were found to be highly epitaxial. Magnetic properties of these films were studied, and the films exhibited ferromagnetic characteristics at room temperature. Detailed structural and microstructural characterization was performed to correlate the fate of the magnetic impurities, i.e., cobalt, and the cause of magnetic properties. It is established from this work that the magnetic properties of these films are inherent to the system, and any presence of second phase/nanoclusters/precipitates are ruled out as the cause of magnetic properties. The techniques used to establish these were conventional and high-resolution transmission electron microscopy (HRTEM) along with electron-energy loss spectroscopy (EELS) and scanning transmission electron microscopy-atomic number (STEM-Z) contrast studies.     

厚度对Si衬底上生长的ZnO薄膜性能的影响

采用金属有机化学气相沉积方法,在Si(100)衬底上生长出具有高度C轴择优取向的ZnO薄膜.通过X射线衍射、原子力显微镜和室温光致发光谱研究了厚度对ZnO薄膜的结构、表面和光学性能的影响.X射线衍射图显示ZnO薄膜只有单一的(0002)峰,具有高度择优取向.AFM和PL测试表明,在取样薄膜厚度范围内,薄膜的表面质量和发光性能没有随着薄膜厚度的增加而提高.这是因为薄膜在厚度增加的生长过程中,生长模型变化且晶粒增大.     

脉冲激光沉积法制备氧化锌薄膜

ZnO是一种新型的Ⅱ-Ⅵ族半导体材料,具有优良的晶格、光学和电学性能,其显著的特点是在紫外波段存在受激发射。利用脉冲激光沉积法(PLD)在氧气氛中烧蚀锌靶制备了纳米晶氧化锌薄膜,衬底为石英玻璃,晶粒尺寸约为28-35 nm。X射线衍射(XRD)结果和光致发光(PL)光谱的测量表明,当衬底温度在100-250℃范围内时,所获得的ZnO薄膜具有c轴的择优取向,所有样品的强紫外发射中心均在378-385 nm范围内,深能级发射中心约518-558 nm,衬底温度为200℃时,得到了单一的紫外光发射(没有深能级发光)。这归因于其较高的结晶质量。     

Growth-Temperature-Controlled Optical Properties of Textured MgxZn1?xO Thin Films

Pulsed laser deposition was used to grow magnesium zinc oxide thin films on amorphous fused silica substrates at several temperatures between room temperature and 750°C. In this study, the effect of growth temperature on the optical properties of textured Mg _x Zn_1−x O thin films was examined. The optical properties of the films were measured using absorption and photoluminescence spectrometry. Absorption spectra revealed that the bandgap values of textured Mg _x Zn_1−x O thin films were enhanced in films grown at higher temperatures. The absorption spectra near the absorption edge were fitted using the Urbach equation in order to investigate the effects of growth temperature on exponential band tail and bandgap. The photoluminescence spectra were measured for magnesium zinc oxide thin films deposited at 250°C, 350°C, 450°C, 550°C, and 650°C. The film grown at 350°C provided the highest excitonic peak intensity. On the other hand, the film grown at 250°C exhibited the lowest excitonic peak intensity. The excitonic peak intensity was considerably reduced in magnesium zinc oxide thin films grown at temperatures greater than 350°C. The ability to perform substrate-temperature-dependent bandgap engineering of Mg _x Zn_1−x O will enable use of this material in next-generation optical and optoelectronic devices.     

Epitaxial growth of ZnO on GaN/sapphire substrate by radio-frequency magnetron sputtering

Zinc oxide (ZnO) thin films were grown on n-GaN/sapphire substrates by radio-frequency (RF) magnetron sputtering. The films were grown at substrate temperatures ranging from 400 to 700 ℃ for 1 h at a RF power of 80 W in pure Ar gas ambient. The effect of the substrate temperature on the structural and optical properties of these films was investigated by X-ray diffraction (XRD), atomic force microscopy (AFM) and photoluminescence (PL) spectra. XRD results indicated that ZnO films exhibited wurtzite symmetry and c-axis orientation when grown epitaxially on n-GaN/sapphire. The best crystalline quality of the ZnO film is obtained at a growth temperature of 600 ℃. AFM results indicate that the growth mode and degree of epitaxy strongly depend on the substrate temperature. In PL measurement, the intensity of ultraviolet emission increased initially with the rise of the substrate temperature, and then decreased with the temperature. The highest UV intensity is obtained for the film grown at 600 ℃ with best crystallization.     

不同衬底温度生长的La_(0.5)Sr_(0.5)CoO_3薄膜椭圆偏振光谱研究

采用脉冲激光沉积法(PLD)在不同Si(100)衬底温度下制备了La_(0.5)Sr_(0.5)CoO_3(LSCO)导电金属氧化物薄膜.X射线衍射(XRD)分析表明,随着衬底温度升高LSCO薄膜的结晶质量增加,在650℃和700℃下制备的薄膜是具有单一钙钛矿结构的多晶薄膜.通过椭圆偏振光谱仪测量了400～1100nm波长范围内该导电金属氧化物薄膜的光学性质,采用双Lorentz振子色散关系及三相结构模型(Air/LSCO/Si)拟合获得了薄膜的光学常数.结果表明,薄膜的折射率随着衬底温度的升高而减小,然而在可见-近红外波长范围内消光系数随着衬底温度的升高而增大.这主要与薄膜的晶化质量和导电性能有密切的关系.     

ZnO Grown on (111) ZnS Substrates by Plasma-Assisted Molecular Beam Epitaxy

ZnO thin films have been grown by plasma-assisted molecular beam epitaxy on (111) ZnS substrates. The films grown on Zn-face substrates showed better structural and optical properties compared with those grown on S-face substrates, as demonstrated by x-ray diffraction and photoluminescence measurements. Scanning electron microscopy measurements indicated that ZnO films grown on Zn-face substrates also have smoother surface morphology. It is also found that higher growth temperature yields films with better quality.     

ZnS/PS复合体系的制备和性能表征

以电化学阳极氧化法制备的多孔硅（PS）为衬底,用脉冲激光沉积方法分别在200和300℃下制备了ZnS薄膜,得到ZnS/PS复合体系。利用X射线衍射仪（XRD）、扫描电子显微镜（SEM）、荧光分光光度计分别对ZnS/PS复合体系的晶体结构、形貌和光致发光（PL）特性进行了研究。XRD结果表明,制备的ZnS薄膜呈立方相晶体结构,沿β-ZnS（111）晶向择优取向生长,生长温度较高的样品的XRD衍射峰强度较大。SEM图像显示,生长温度较高的ZnS薄膜表面较致密平整。室温下的PL谱表明,沉积ZnS薄膜后,PS的发光峰发生蓝移。较高的生长温度下,ZnS的自激活发光强度较大,而PS的红光强度较低且峰位红移。根据三基色叠加的原理,ZnS的蓝绿光与PS的红光叠加在一起,ZnS/PS复合体系呈现出较强的白光发射,为固态白光发射器件的实现开辟了一条新的捷径。     

Pulsed laser deposition of carbon films: Dependence of film properties on laser wavelength

We have grown thin carbon films by pulsed laser deposition and have investigated the extent to which the properties of such films, as well as the processes responsible for these properties, are laser wavelength dependent. Films were grown by ablating material from a graphite target onto room temperature Si(100) substrates with 1064 and 248 nm laser radiation. The films were analyzed byin situ electron energy loss spectroscopy and byex situ Raman spectroscopy. The results indicated that films grown with 1064 nm ablation were graphitic, while those grown with 248 nm radiation were diamond-like. We have also examined the mass and kinetic energy distributions of the particles ejected from graphite by the two laser wavelengths. The results indicated that irradiation of graphite with 1064 nm laser radiation results in the ejection of a series of carbon cluster ions C _n ⁺ (1 ≤ n ≤ 30) with mean kinetic energies less than 5 eV. Ablation of graphite with 248 nm radiation results in the ejection of primarily C ₂ ⁺ and C ₃ ⁺ with mean kinetic energies of 60 and 18 eV, respectively. These results suggest that large, low energy clusters produce graphitic films, while small, high energy clusters produce films of diamond-like carbon.     

利用金属键合和激光剥离技术制备GaN/metal /Si异质结构的研究

利用金属键合和激光剥离将生长在蓝宝石衬底上的GaN薄膜转移到Si衬底上。键合后采用波长为248nm的准分子脉冲激光辐照蓝宝石衬底,低温处理去除蓝宝石衬底。系统地研究不同键合温度和激光能量密度对GaN结构和光学特性的影响。AFM、XRD和PL测试表明：键合温度和激光剥离的能量密度较低,转移衬底后GaN的质量较好;激光剥离的阈值能量密度为300mJ/cm2;键合温度400℃的样品均方根粗糙度（RMS）约为50nm。