激光干涉结晶技术制备二维有序分布纳米硅阵列

利用结合移相光栅掩模 (PSGM) 的激光结晶技术在超薄a-SiN_x/a-Si:H/ a-SiN _x三明治结构样品中制备出二维有序分布的纳米硅阵列.原始样品是用等离子体 增强化学气相淀积法生长.a-Si:H层厚为10nm，a-SiN_x 为50nm，衬底材料为SiO ₂/Si或 熔凝石英.原子力显微镜、剖面透射电子显微镜、高分辨透射电子显微镜对样品表面形貌和 微结构的观测结果表明，采用该方法可以在原始淀积的a-Si:H层中得到位置可控的晶化区域 ：每个晶化区域直径约250nm，具有同PSGM一致的2μm周期；晶化区域内形成的纳米硅 颗粒尺寸接近原始淀积的a-Si:H层厚，且晶粒的择优取向为<111>. 关键词： 纳米硅 激光结晶 定域晶化 移相光栅     

激光干涉结晶法制备一维周期结构的纳米硅阵列

利用激光干涉结晶方法,采用周期为400 nm的一维(1D)移相光栅掩模调制KrF准分子激光器的脉冲激光束斑的能量分布,在不同厚度的超薄氢化非晶硅(a-Si:H)膜内直接制备1D有序纳米硅(nc-Si)阵列.拉曼散射谱表明,样品上呈条状分布的受辐照区域发生晶化.原子力显微镜和透射电子显微镜测试结果表明：1D的nc-Si阵列的周期和移相光栅掩模一样.随着a-Si:H膜厚度从10nm降至4nm,通过控制激光的能量密度,每个周期中nc-Si条状分布区宽度可达到30nm.nc-Si条状分布区的高分辨电子显微镜照片显 关键词： 纳米硅 激光干涉结晶 移相光栅 定域晶化     

激光晶化形成纳米硅材料的场电子发射性质研究

利用KrF准分子激光退火超薄非晶硅膜,并结合热退火技术制备了单层纳米硅薄膜并研究了薄膜的场电子发射性质.在晶化形成的纳米硅薄膜中可以观测到稳定的场电子发射现象,其开启电场从原始淀积的非晶硅薄膜的17V/μm降低到8.5V/μm,而场发射电流密度可以达到0.1mA/cm².激光晶化后形成的纳米硅材料的场电子发射特性的改善可以从薄膜表面形貌的改变以及高密度纳米硅的形成所导致的内部电场增强作用来解释. 关键词： 纳米硅 场发射 激光晶化     

Nickel-disilicide-assisted excimer laser crystallization of amorphous silicon

Polycrystalline silicon (poly-Si) thin film has been prepared by means of nickel-disilicide (NiSi多晶硅 受激准分子激光器结晶 结晶化 界面晶粒生长polycrystalline silicon, excimer laser crystallization,Ni-disilicide, Ni-metal-induced lateral crystallization, two-interface grain growthProject supported by the National High Technology Development Program of China (Grant No 2002AA303250) and by the National Natural Science Foundation of China (Grant No 60576056).9/7/2005 12:00:00 AM3/6/2006 12:00:00 AMPolycrystalline silicon （poly-Si） thin film has been prepared by means of nickel-disilicide （NiSi2） assisted excimer laser crystallization （ELC）. The process to prepare a sample includes two steps. One step consists of the formation of NiSi2 precipitates by heat-treating the dehydrogenated amorphous silicon （a-Si） coated with a thin layer of Ni. And the other step consists of the formation of poly-Si grains by means of ELC. According to the test results of scanning electron microscopy （SEM）, another grain growth model named two-interface grain growth has been proposed to contrast with the conventional Ni-metal-induced lateral crystallization （Ni-MILC） model and the ELC model. That is, an additional grain growth interface other than that in conventional ELC is formed, which consists of NiSi2 precipitates and a-Si. The processes for grain growth according to various excimer laser energy densities delivered to the a-Si film have been discussed. It is discovered that grains with needle shape and most of a uniform orientation are formed which grow up with NiSi2 precipitates as seeds. The reason for the formation of such grains which are different from that of Ni-MILC without migration of Ni atoms is not clear. Our model and analysis point out a method to prepare grains with needle shape and mostly of a uniform orientation. If such grains are utilized to make thin-film transistor, its characteristics may be improved.     

二维移相光栅光强分布的计算及在制备有序纳米硅阵列中的应用

从菲涅耳衍射积分的一般形式出发,结合二维（2D）移相光栅掩模(PSGM)的具体参数,通过数值计算得到了作用于样品表面的光强分布.实验上,采用激光干涉晶化的方法,利用周期为400 nm的2D-PSGM调制KrF准分子激光器的脉冲激光束斑的能量分布,在氢化非晶硅（a-Si:H）薄膜上直接制备了2D的有序纳米硅（nc-Si）阵列.测试结果表明：2D的nc-Si阵列的周期和PSGM的相一致,晶化区域与理论模拟的结果符合得很好. 关键词： 纳米硅 激光干涉晶化 移相光栅 菲涅耳衍射     

脉冲激光晶化超薄非晶硅膜的分子动力学研究

利用准分子脉冲激光晶化非晶硅薄膜是制备高密度尺寸可控的硅基纳米结构的有效方法之一.本文将脉冲激光对非晶硅超薄膜的影响处理为热传导问题,采用了基于Tersoff势函数的分子动力学方法模拟了在非晶氮化硅衬底上2.7 nm超薄非晶硅膜的脉冲激光晶化过程.研究了不同激光能量对非晶硅薄膜晶化形成纳米硅的影响,发现在合适的激光能量窗口下,可以获得高密度尺寸可控的纳米硅薄膜,进而模拟了在此能量作用下非晶硅膜中成核与生长的机理与微观过程,并对晶化所获得的纳米硅薄膜的微结构进行了分析. 关键词： 非晶硅 分子动力学 脉冲激光晶化     

Ag掺杂对高重复频率飞秒激光诱导Gd2O3-MoO3-B2O3玻璃析晶

将800nm高重复频率250 kHz的飞秒激光分别聚焦到掺Ag和没有掺Ag的Gd2O3-MoO3- B2O3玻璃表面,研究掺Ag对飞秒激光诱导析晶的影响。对激光辐照的区域显微拉曼分析发现对于没掺Ag玻璃,诱导玻璃析晶需要的激光功率和辐照时间比掺了Ag的玻璃要大要长,这说明Ag的掺入促进了玻璃的析晶。其机理可能为飞秒激光的多光子吸收效应,导致玻璃基质中桥氧键断裂,产生非桥氧空穴和自由电子,玻璃中的Ag离子捕获电离出来的电子被还原成Ag原子,Ag原子在热动力的驱动下移动聚集形成银纳米颗粒,形成的银纳米团簇作为核促进了钼酸盐玻璃的析晶。     

碳化硅薄膜脉冲激光晶化特性研究

采用XeCl准分子激光对非晶碳化硅(a-SiC)薄膜的脉冲激光晶化特性进行了研究.通过原子力显微镜（AFM）和Raman光谱技术对退火前后薄膜样品的形貌、结构及物相特性进行了分析.结果表明，选用合适的激光能量采用激光退火技术能够实现a-SiC薄膜的纳米晶化.退火薄膜中的纳米颗粒大小随着激光能量密度的增加而增大；Raman谱分析结果显示了退火后的薄膜的晶态结构特性并给出了伴随退火过程存在的物相分凝现象.根据以上结果并结合激光退火特性，对a-SiC的脉冲激光晶化机理进行了讨论. 关键词： 激光退火 晶化 碳化硅     

激光限制结晶技术制备nc-Si/SiO2多层膜

在等离子体增强化学气相淀积系统中，采用aSi:H层淀积和原位等离子体氧化相结合的逐层生长技术制备了aSi:H/SiO_2多层膜.在激光诱导限制结晶原理基础上，使用KrF准分子脉冲激光为辐照源，对aSi:H/SiO_2多层膜进行辐照，使纳米级厚度的aSi:H子层晶化.Raman散射谱和电子衍射谱的结果表明，经过激光辐照后纳米Si颗粒在原始的aSi:H子层内形成，晶粒尺寸可以根据aSi:H层的厚度精确控制.还研究了样品的光致发光（PL）特性以及激光辐照能量密度对PL性质的影响. 关键词： 脉冲激光 多层膜 限制结晶     

Fabrication of Au thin film gratings by pulsed laser interference

We report that one-dimensional (1D) and two-dimensional (2D) metal thin film gratings can be directly fabricated by interfering Nd-YAG pulsed laser beams (wavelength = 1064 nm, pulse width = 6 ns) incident from the backside of glass substrate. This process utilizes a laser-induced thermo-elastic force which plays a role to detach the film from the substrate. Micro-scale Au transmission gratings with a minimum feature size of 1 μm could be generated by interference-driven periodic detachment. The fabrication of tube-structured patterns as well as stripes was also possible by adjusting the pulse power and this is explained with the effect of film cohesion.     

低压下气流对激光沉积纳米硅晶化及尺寸的影响

纳米硅具有明显的光致发光效应和量子尺寸效应,广泛的应用在现代电子工业和太阳能光伏工业中.尺寸影响着纳米硅的实际用途,因此制备尺寸可控的纳米硅晶粒具有很重要的实际意义.本文采用脉冲激光沉积(PLD)技术,在烧蚀点水平方向、距靶2 cm处引入一束流量为5 sccm的氩(Ar)气流,在0.01-0.5 Pa的Ar气压下烧蚀高阻抗单晶硅(Si)靶.在管口正下方1 cm处水平放置衬底来沉积纳米Si薄膜;并用同一装置,在0.08 Pa的Ar气压下分别引入流量为0,2.5,5,7.5,10 sccm的Ar气流沉积纳米Si薄膜.利用原子力显微镜(AFM)、X射线衍射(XRD)、Raman散射对样品表面形貌和微观结构进行分析表征.结果表明:不引入气流时出现纳米Si晶粒的阈值气压是0.1Pa,引入气流后出现纳米Si晶粒的阈值气压为0.05 Pa.晶粒尺寸随着气流流量的增大而减小.     

Radiation effects on poly(methyl methacrylate) induced by pulsed laser irradiations

Poly(methyl methacrylate) (PMMA) was irradiated using a medical UV-ArF excimer laser operating at the fundamental wavelength of 193 nm. Characterized by a beam diameter of 1.8 mm and energy of 180 mJ with a Gaussian energy profile, it operates in a single mode or at 30 Hz repetition rate. Mechanical profilometry was carried out on ablation craters in order to study the rugosity and the ablation yield in the various operative conditions. Optical transmission and reflection measurements at six wavelengths were conducted in order to characterize the optical properties of the irradiated surfaces. Measured crater depths in PMMA were lower with respect to the forecasted ones in corneal tissue, while the lateral crater aperture was maintained. The rugosity produced at the crater bottom after irradiation was about 0.3 μm, and the ablation yield was about 10¹⁵ molecules/laser pulse, while etching depth and diameter show a roughly linear dependence on the number of laser shots. These experiments constitute a base for deeper clinical investigations.     

Electroluminescence with micro-watt output from ultra-small sized Si quantum dots/amorphous SiO2 multilayers prepared by laser crystallization method

We report the fabrication of Si quantum dots (QDs)/SiO₂ multilayers by using KrF excimer laser (248 nm) crystallization of amorphous Si/SiO₂ multilayered structures on ITO coated glass substrates. Raman spectra and transmission electron microscopy demonstrate the formation of Si QDs and the size can be controlled as small as 1.8 nm. After laser crystallization, Al electrode is evaporated to obtain light emitting devices and the room temperature electroluminescence (EL) can be detected with applying the DC voltage above 8 V on the top gate electrode. The luminescent intensity increases with increasing the applied voltage and the micro-watt light output is achieved. The EL behaviors for samples with different Si dot sizes are studied and it is found that the corresponding external quantum efficiency is significantly enhanced in sample with ultra-small sized Si QDs.     

用于高能啁啾脉冲压缩的光子晶体光栅的设计

为了克服目前高能短脉冲装置压缩光栅的损伤阈值无法满足要求的问题,针对星光Ⅲ装置皮秒激光束的压缩器,设计了由熔石英材料构成的、具有较高损伤阈值的光子晶体光栅,该光栅由2维光子晶体和表面光栅结构两部分组成,具有高反射效率和强角色散的能力。计算结果显示:经过优化设计的光子晶体光栅在波长1 053 nm,57°～77°的入射范围内,-1级衍射效率超过了92%,而当入射角为71°时,在1 040～1 090 nm光谱范围内,-1级衍射效率超过92%,性能满足使用要求。     

Ar环境气压对脉冲激光烧蚀制备纳米Si晶粒平均尺寸的影响

采用XeCl脉冲准分子激光器，烧蚀高阻抗单晶Si靶，在1—500 Pa的Ar气环境下沉积制备了纳米Si薄膜. x射线衍射谱测量证实，纳米Si晶粒已经形成.利用扫描电子显微镜观测了所形成纳米Si薄膜的表面形貌，结果表明，随着环境气压的增加，所形成的纳米Si晶粒的平均尺寸增大，气压为100 Pa时达到最大值20 nm，而后开始减小. 从晶粒形成动力学角度，对实验结果进行了定性分析. 关键词： 纳米Si晶粒 脉冲激光烧蚀 表面形貌     

The mechanism for SEU simulation by pulsed laser

~~The mechanism for SEU simulation by pulsed laser~~     

Preparation and characterization of pulsed laser deposition (PLD) SiC films

Si K-edge XAFS was used to characterize a stoichiometric SiC film prepared by pulsed KrF laser deposition. The film was deposited on a p-type Si(1 0 0) wafer at a substrate temperature of 250 °C in high vacuum with a laser fluence of ∼5 J/cm². The results reveal that the film contains mainly a SiC phase with an amorphous structure in which the Si atoms are bonded to C atoms in its first shell similar to that of crystalline SiC powder but with significant disorder.     

脉冲激光烧蚀制备纳米Si晶粒成核区位置的确定

为了确定纳米Si晶粒气相成核的位置，采用XeCl准分子激光器，在10Pa氩气环境下，烧蚀高阻抗单晶Si靶，在距离等离子羽正下方2.0cm处、与其轴线平行放置一系列单晶Si或玻璃衬底，沉积制备了纳米Si薄膜. X射线衍射、Raman散射、扫描电子显微镜和原子力显微镜结果均显示，纳米Si晶粒只在距靶约0.5—2.8cm平行距离范围内的样品上形成，在此范围内，随着离靶平行距离的增大，所形成的纳米Si晶粒的平均尺寸逐渐减小，并且晶粒尺寸的分布也发生变化. 根据成核区起始和终止的突变特征，结合晶粒形成后的平抛运动规律，对晶粒气相成核的位置进行了估算. 关键词： 纳米Si晶粒 脉冲激光烧蚀 成核区     

用于高能啁啾脉冲压缩的光子晶体光栅的设计

 为了克服目前高能短脉冲装置压缩光栅的损伤阈值无法满足要求的问题,针对星光Ⅲ装置皮秒激光束的压缩器,设计了由熔石英材料构成的、具有较高损伤阈值的光子晶体光栅,该光栅由2维光子晶体和表面光栅结构两部分组成,具有高反射效率和强角色散的能力。计算结果显示:经过优化设计的光子晶体光栅在波长1 053 nm,57°～77°的入射范围内,-1级衍射效率超过了92%,而当入射角为71°时,在1 040～1 090 nm光谱范围内,-1级衍射效率超过92%,性能满足使用要求。