Sb2Te基薄膜的飞秒激光诱导相变与二次谐波产生研究
文献类型：学位论文
| 作者 | 江明徽 |
| 文献子类 | 硕士 |
| 导师 | 王阳 |
| 关键词 | 相变存储材料 phase change memory material 飞秒激光 femtosecond laser 二次谐波产生（SHG） second harmonic generation (SHG) |
| 其他题名 | Femtosecond laser induced phase transition and second harmonic generation of Sb2Te-based thin films |
| 英文摘要 | 基于相变材料的可擦重写相变光盘和非易失性相变随机存储器已成功商业化。高性能相变材料和快速相变机制是其中的关键科学和技术问题，随着应用的深入，仍有待进一步研究、探索。近年来，超短脉冲激光诱导相变获得越来越多的关注，超短的操作时间除了可以获得更高的数据读写速率，还有利于对相变薄膜晶化程度实现精确控制。 富含Sb元素的硫系相变材料（如Sb2Te）的晶化机制是生长主导型，一般认为更适合用于快速擦写，然而，却面临热稳定性不够高等问题。研究表明，在Sb2Te合金中加入Cr等元素能有效提高材料的性能，然而对其超快激光诱导相变动力学过程鲜有研究、报道。 本论文用飞秒激光激发实时反射率探测装置研究了CrxSb2Te薄膜在多脉冲飞秒激光诱导下的晶化过程。系统地分析了材料组分、脉冲数量和脉冲能量密度对反射率对比度变化的影响。研究了单脉冲飞秒激光诱导CrxSb2Te薄膜的时间分辨晶化、非晶化和烧蚀过程。分析了Cr元素的掺入对Sb2Te薄膜超快存储性能的影响。 作为激光激发相干光学过程，二次谐波产生（SHG, Second Harmonic Generation）具有很高的方向性、灵敏度，能反映材料的对称性信息，对晶体的各向异性、材料的表面结构纹理十分敏感，适合作为无损、原位探测手段研究材料的结构转变过程。 本文将表面SHG探测技术用于相变存储材料研究中。搭建了飞秒激光激发表面SHG探测系统，通过多级滤波、放大实现了相变薄膜微弱SHG信号的检测。研究了Sb2Te薄膜在不同相态的SHG光谱，分析了Ge2Sb2Te5薄膜SHG强度随泵浦光偏振方向的变化规律及其与晶粒取向分布的关系。 研究结果对发展新型快速相变材料，深入理解极端非平衡条件下的相变机制，以及拓展相变材料的非线性光学应用等具有重要参考价值。; The rewritable phase-change optical disk and nonvolatile phase-change random access memory based on phase change materials have been commercialized successfully. High performance phase change materials and fast phase transition mechanism are the key scientific and technical issues in this field. Further study and exploration are still needed with the deepening and extension of its application. In recent years, ultrashort laser pulse induced phase transition is gaining more and more attention. The ultrashort operation time can get super-high data transfer rate for memories, and are helpful for precise control of the crystallization degree of phase change thin films. Sb-rich chalcogenide phase change materials (such as Sb2Te) generally have a growth-dominated crystallization mechanism. They are often considered to be more suitable for fast reading and writing operations. However they are often suffering from low thermal stability. Recent researches show that the addition of Cr or other elements into Sb2Te alloy can effectively improve its properties. However, the ultrafast laser induced phase transition process of them has seldom been studied and reported. In this dissertation, the femtosecond laser pulse induced phase transition dynamics of CrxSb2Te films was studied by real-time reflectivity measurements. The influence of the doping contents, the number of pulses and the pulse fluences on the reflectivity contrast was systematically studied. The time-resolved crystallization, amorphization, and ablation processes of CrxSb2Te films induced by single-shot femtosecond laser pulses were also studied. The improvement of the ultrafast data storage characteristics the films by Cr doping was analyzed comprehensively. As the laser excited coherent optical process, second harmonic generation (SHG) with high directionality and sensitivity, can reflect the symmetry of materials. It is very sensitive to the anisotropic structure of crystals and the surface texture (orientation) of materials, and suitable for the nondestructive and in-situ detection of structural transformation processes. In this dissertation, the surface SHG detection technique was used for the study of phase change memory materials. A femtosecond laser excited surface SHG pump-probe system was built up, and the detection of weak SHG signals of phase change films was realized by multi-stage filtering and amplification. The SHG spectra of Sb2Te thin films at different phases were studied. The change of SHG intensity of Ge2Sb2Te5 films with the polarization direction of the pumping laser and the orientation distribution of crystalline grains were analyzed in detail. These research results have important reference value for developing new ultrafast phase change materials, understanding the phase transition mechanism under extreme non-equilibrium conditions, and extending applications of phase change materials in nonlinear optics. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30998]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 江明徽. Sb2Te基薄膜的飞秒激光诱导相变与二次谐波产生研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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