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题名	基于表面等离子体共振的探针辅助光存储技术
作者	洪小刚
学位类别	博士
答辩日期	2010
授予单位	中国科学院上海光学精密机械研究所
导师	徐文东
关键词	近场光存储 表面等离子体共振 时域有限差分方法 场增强 探针
其他题名	Probe assisting optical storage technology based on Surface Plasmon Resonance
中文摘要	二十一世纪是信息的时代，随着计算机技术，特别是多媒体技术的迅猛发展，人们对信息存储品质、容量和速度的要求不断提高，而现有的存储技术已不能满足要求，为此人们对信息存储领域进行了许多深入和开创性地研究。本博士论文基于近场光学原理提出了一种新的光存储技术——基于表面等离子体共振的探针辅助光存储技术(Probe assisting optical storage technology based on Surface Plasmon Resonance，PSPR)。该技术利用Kretschmann型表面等离子体共振(Surface Plasmon Resonance，SPR)结构激发SPR，获得增强倏逝场，再利用探针的局域场增强效应使得处于倏逝场中的探针在针尖处获得二次场增强，从而在近场范围内实现对记录材料的光刻。它可采用低功率、小聚焦程度的入射激光获得高记录功率并实现纳米光刻。论文重点采用时域有限差分方法(Finite Difference Time Domain method，FDTD)对该光存储技术进行模拟分析，并在实验上验证其可行性，还对PSPR的一些关键技术进行了理论探索，其内容主要包括以下几个部分： 1) 综述、理论和研究方法部分。论文首先是综述了近场光学存储技术，简述各种光存储技术的原理、最新进展、优缺点和研究方向，并提出本论文的主要研究内容；其次是介绍本论文提出的光存储技术的理论基础，包括SPR以及探针的局域场增强效应；最后是对本论文所采用的FDTD方法做了简介。 2) FDTD数值模拟PSPR，并实验验证其可行性。论文首先采用FDTD模拟获得了SPR曲线及共振角度。随后模拟了基模高斯光束激发SPR，并选用针尖曲率半径为10 nm的Si材料AFM探针作为记录探针，结果表明当探针距离记录层表面5 nm时，在记录层表面可获得半高全宽(Full Width at Half Maximum, FWHM)为15 nm的场强分布峰，且对应的主峰值明显大于次峰值，在理论上证明了该光存储技术的可行性。在实验分析上，论文对三种SPR结构进行了实验，分别是单层Ag膜结构，双层Ag/AgOx结构和三层Ag/SiO2/AgOx结构。实验首先对SPR结构的共振角进行了测量，结果显示对于单层Ag膜结构，理论和实验符合的较好，而双层和三层的却相差较大，分析得出这主要是由所镀膜层的表面粗糙度引起。光刻实验也出现了类似的实验结果，膜层越多效果越差，最好的结果是在单层30 nm Ag膜上获得了直径80 nm，深15 nm的记录点。造成这种现象的原因除了膜层表面粗糙外，还有SPR结构的共振场增强效应小以及探针对SPR的影响。 3) 优化SPR膜系结构。第二部分中提出实验结果不理想一部分是因为SPR结构的共振场增强不大，为此论文对PSPR所采用的三种膜系结构进行了优化设计。优化设计首先修正了全反射时多层介质结构的透射系数计算公式，并采用FDTD方法进行了验证，随后分别优化设计了三种SPR结构：单膜层结构，最佳Ag膜厚度是46 nm；对于双膜层结构，其最优解是Ag膜层厚40 nm，AgOx膜层厚10 nm；三膜层结构的最优解是Ag膜层的厚度为44 nm，SiO2膜层的厚度为180 nm，AgOx膜层厚度为10 nm，此三膜层结构的最大透射系数是所有结构中最大的，只是透射系数曲线的FWHM太小。此外计算结果也表明：对于双膜层和三膜层结构，随着非金属膜层的增厚，膜系结构的透射系数呈“周期性变化”，并且每个周期内的最大透射系数对应的入射角都为临界全反射角。 4) 模拟分析PSPR记录探针。第二部分中提出的探针对SPR的影响也是导致实验不理想的一个重要原因。论文的这部分主要通过数值模拟探针在共振场中的场分布，分析探针材料、针尖曲率半径以及探针到记录层表面的距离对光刻的影响。在探针材料方面，模拟结果表明一般情况下金属探针的局域场增强要比非金属的强，但由于金属探针性质较活泼，不稳定，目前主要是在Si探针上镀膜制成，其针尖曲率半径较大，相比之下非金属探针的针尖曲率半径小，在一定程度上可获得较金属探针更强的局域场增强，此外非金属探针的散射系数较金属探针的小，同等条件下可获得更深的记录点。在针尖曲率半径方面，记录层表面电场强度振幅分布主峰的FWHM几乎由针尖曲率半径决定，此外模拟分析显示针尖曲率半径越大，次峰高度反而越小。在探针到记录层的距离方面，虽然距离对探针的局域场增强因子影响较小，但由于散射场的指数衰减特性且探针处于倏逝场中，使得记录层表面的电场强度振幅随距离的增大而快速减小，这就导致了探针的工作距离很小，一般不超过25 nm。由此得出采用局域场增强效应大的金属探针或采用针尖曲率半径小的非金属探针工作在接触模式下是PSPR的最佳方案。 本博士论文总结了作者在博士期间关于该课题的主要研究成果。作者在论文最后做了一些总结和展望，相信随着对PSPR的深入研究，其必能真正被用于超高密度光存储。
英文摘要	21st Century is an information age. As the development of the computer technology, especially the multimedia technology, people’s requirements for the information storage’s quality, capacity and speed are increasing continuously. But the existing storage technologies can not meet the demands. So people are doing deeper and groundbreaking researches on the information storage technologies. Based on near-field optics principle, this dissertation presented a new storage technology named Probe assisting optical storage technology based on Surface Plasmon Resonance (PSPR). This storage technology utilizes a Kretschmann Surface Plasmon Resonance (SPR) structure for exciting SPR to get an enhanced field, and achieves photoetching on the recording medium in near field using local field enhancement effect of tip. It can get a high recording power and achieve recording in a small size area by using a low power and low focus level illuminating laser. In this dissertation PSPR was simulated and analysed by Finite Difference Time Domain method (FDTD), and was verified experimently. Furthermore, some key technologies of this storage technology were studied theoretically. Several parts are included in this dissertation: 1) Reviews, theory and research method. In this dissertation we reviewed the near-field optical storage technologies, introduced the principles, new developments, merit and demerit of these optical storage technologies and current research topics firstly. Then we introduced PSPR’s theories including the theory of SPR and the probe local field enhancement effect. At last of this part, FDTD method was introduced. 2) PSPR Simulated by FDTD, and verifying feasibility experimently. By FDTD method, the SPR reflectivity curve and the resonance angle were obtained. Then we simulated SPR excited by a fundamental mode Gaussian beam, and chose a Si AFM probe with a tip radius of 10 nm for the recording probe. The simulation results show that when the tip is 5 nm far from the recording layer, the main peak FWHM of the electric field amplitude distribution on the surface of recording layer is 15 nm, and the main peak is obviously higher than the secondary peak, so PSPR is feasible in theory. Then we experimented on three kinds of SPR structures, including single Ag film structure, Ag / AgOx two films structure and Ag/ SiO2/AgOx three films structure. At first we measured the resonance angles for different structures. It shows that the experiment result fits well with the theoretical one for single Ag film structure, but not very well for two or three films structures. That’s primarily because of the roughness of the films. So are the recording experiments. In these experiments we can only get a smallest spot with a diameter of 80 nm and a depth of 15 nm on single 30 nm Ag film structure. That is not only because of the film roughness, but also for the field enhancement level of SPR and the effect of the probe on SPR. 3) Optimization of the SPR structure. Low field enhancement of SPR structure is one of the reasons for the non ideal experimental results. In this dissertation, we optimized three kinds of SPR structures. A computing formula for calculating the transmission coefficients of the multilayer when total internal reflection took place was corrected and was verified by FDTD method at the beginning. Then we designed the SPR structures: Ag 46 nm for single film structure, Ag 40 nm / AgOx 10 nm for two films structure and Ag 44 nm / SiO2 180 nm / AgOx 10 nm for three films structure. Among these structures, the optimized three films structure has a biggest field enhancement factor, but a small FWHM of the transmission coefficient curve. In additional, the calculated results show that for two and three films structures, the transmission coefficient changes quasi-periodically and the resonance angle for the biggest transmission coefficient is the total internal reflection critical angle in every period except for the first one. 4) Simulation and analysis on PSPR probe. Effect of the probe on SPR is another important reason for the non ideal experimental results. In this part, by simulating the electrical field intensity distribution, we analyzed the effects of the probe on SPR with different materials, tip radiuses and the distances of the probe from the recording layer. For probe material, generally, the metallic probe can obtain a stronger field enhancement than the nonmetallic ones. But because of the instability, the metallic probes are always made by coating metallic film on Si probes, which makes the tip radiuses bigger than nonmetallic ones, and some may generate a smaller field enhancement effect. Moreover, for the smaller scattering coefficient, the nonmetallic probe can get deeper spots with the same recording conditions. The FWHM of the electrical field intensity distribution on the surface of the recording layer is determined by the tip radius. And the results also show that the bigger the tip radius is the lower the secondary peak is. For the distance of probe from the recording layer, the results show that the distance has weak influence on the field enhancement factor. However, the scattering field is the exponential decay and probe is in the evanescent field. These lead to the probe working distance is short and always less than 25 nm. It follows that by using a metallic probe with a big field enhancement effect or a nonmetallic probe with a small tip radius and working in contact mode is the best scheme for PSPR. This dissertation summarizes all the achievements of PSPR when the author was working as a Ph.D candidate. In the last section of the dissertation, it gives a conclusion and an outlook. And the author believes that with deeper researches, PSPR can get a practical application in ultra-high density optical storage.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15620]
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	洪小刚. 基于表面等离子体共振的探针辅助光存储技术[D]. 中国科学院上海光学精密机械研究所. 2010.

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