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题名	相变存储材料的飞秒激光诱导击穿光谱研究
作者	蔡志龙
学位类别	硕士
答辩日期	2015
授予单位	中国科学院上海光学精密机械研究所
导师	王阳
关键词	飞秒激光诱导击穿光谱 相变存储材料 溅射薄膜 时间分辨光谱
其他题名	Study on the femtosecond laser induced breakdown spectra of phase change memory materials
中文摘要	激光诱导击穿光谱（Laser induced breakdown spectroscopy，LIBS），又称激光诱导等离子体光谱（LIPS），是一种激光取样的原子/离子发射光谱。由于这种谱线带有明显的元素特征信息，使其成为一种元素分析的有效手段；此外，由于其携带了大量有关等离子体的复杂原子跃迁过程的信息，对深入理解激光与材料相互作用机制也很有帮助。近年来，飞秒激光诱导击穿光谱（fs-LIBS）技术因其激光脉冲作用时间短、峰值功率高，具有可抑制自吸收效应和热效应等优势而受到关注，成为LIBS技术发展的重要新方向之一。 相变信息存储材料是可擦写相变光盘和相变随机存储器(PCRAM)的存储介质，主要是由金属和半导体组成的化学计量比或者非化学计量比多元合金。相变存储材料的光谱性质（如椭圆偏振光谱、反射光谱等）对薄膜器件设计，以及对材料结构、相变机制的认识等具有重要的参考价值，但目前对其LIBS光谱的研究报道还非常少。 本论文主要通过fs-LIBS技术从时间分辨等离子体光谱、成分定量分析和薄膜深度剖析等方面对几种典型的相变存储材料（包括薄膜样品）进行了系统研究。 论文首先介绍了LIBS相关的概念和工作原理，重点阐述了飞秒激光与物质的相互作用过程及相应的激光等离子体的演化特征。介绍了通过测量谱线Stark展宽获得等离子体电子密度以及通过Boltzmann曲线方法获得电子温度的方法。介绍了定标曲线和自由定标定量分析方法。最后简略介绍了相变存储材料的研究进展和意义。 论文详细描述了自行构建的fs-LIBS实验装置，其特点是增加了样品反射率同步监控系统和等离子体羽瞬态、原位成像系统，可以改善LIBS光谱的实时监控能力以及薄膜深度剖析能力。 采用fs-LIBS技术研究了金属相变材料——Cu-Al合金溅射薄膜和靶材的时间分辨等离子体光谱特性。通过分析Al I 396.2nm谱线的Stark展宽情况，计算了等离子体中的电子密度。采用定标曲线和自由定标方法对Cu-Al合金溅射薄膜进行了定量成分分析，并比较了其与溅射靶材成分之间的差异。结合同步瞬态反射率测试对Cu-Al薄膜样品进行了fs-LIBS深度剖析，可以准确找到薄膜与玻璃基底的界面，单脉冲平均取样深度约90nm。 测量了半导体相变合金材料及其主要组元（包括Sb、Te、Bi、Sb70Te30、Ge2Sb2Te5等）的飞秒激光诱导时间分辨等离子体光谱，分析了谱线的Stark展宽特性，并且计算获得了在不同延迟时间下的等离子体密度和温度，比较了不同样品中特征谱线的演化过程差异。结合同步瞬态反射率系统，对玻璃基底上Sb单层和双层薄膜进行了fs-LIBS深度剖析，准确找到薄膜间及与玻璃基底的界面，单脉冲平均取样深度约133nm。
英文摘要	Laser induced breakdown spectroscopy (LIBS), which is also called laser induced plasma spectroscopy (LIPS), is a kind of atoms emission spectrometry (AES) with laser sampling. Since its spectral lines have characteristic information of elements, it becomes an efficient method for component analysis. Besides, it is helpful for us to deeply understand the interaction mechanism between laser and materials, because there is a large number of relevant information about the complex atomic transition process of plasma. Recently, femtosecond laser induced breakdown spectroscopy (fs-LIBS) has become an important branch since femtosecond laser pulse, which has much shorter pulse width and higher peak power, can reduce the self-absorption and thermal effects during sampling. Phase change memory materials are the recording media of rewritable optical disks and PCRAMs. They are often stoichiometric or non-stoichiometric alloys composed of metal and semiconductor elements. The spectral properties of phase change memory materials, such as ellipsometry and reflection spectra, are instructive for the design of multilayer devices and the understanding of the material structures and phase transition mechanisms. But the laser induced breakdown spectra of phase change memory materials are seldom reported until now. In this dissertation, fs-LIBS was employed to analyze several typical phase change memory materials including thin film samples. The time-resolved plasma spectra, quantitative analysis of the components and depth profiling of thin films were studied systematically. At first, the relevant concepts and principle of LIBS were introduced. The interaction process of femtosecond laser with samples was emphasized. Then, the method for obtaining electron density by Stark broadening effect and that for obtaining plasma temperature by Boltzmann curve were well introduced. Furthermore, the calibration curve and calibration free methods for quantitative analysis were described. Finally, the significance and research progress of phase change memory materials were briefly introduced. A home-made set-up of fs-LIBS was described in detail. Synchronous real-time reflectance monitoring and plasma plume imaging sub-systems were added to the standard spectrometer, which can improve the ability of real-time monitoring and film depth profiling. Cu-Al phase change alloy sputtering targets and thin films were analyzed by fs-LIBS. The Stark broadening effects were analyzed for the Al I line at 396.2nm. Quantitative component analysis for the thin films was carried out with the calibration curve and the calibration free method respectively. The composition difference between the thin films and corresponding targets was compared as well. Additionally, depth profiling was carried out for Al67Cu33 thin films. The thin film/substrate interface could be found accurately and an average ablation depth of 90nm per pulse was obtained. The time-resolved plasma spectra of semiconductor phase change materials and several constituent elements, such as Sb, Te, Ge, Bi, Sb70Te30 and Ge2Sb2Te5, were measured by fs-LIBS. The Stark broadening effect was studied and the electron density and temperature were calculated out. The evolution difference of characteristic spectral lines between the samples was compared as well. Depth profiling was performed on Sb single- and bi-layer films and the sampling depth per pulse could be about 133nm.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16924]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	蔡志龙. 相变存储材料的飞秒激光诱导击穿光谱研究[D]. 中国科学院上海光学精密机械研究所. 2015.

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