| 题名 | Sb掩膜型超分辨近场光存储技术及机理研究 |
| 作者 | 魏劲松 |
| 学位类别 | 博士 |
| 答辩日期 | 2004 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 干福熹 |
| 关键词 | Sb薄膜 光存储 超分辨 近场 热透镜 结构转变 脉冲激光 FDTD方法 超分辨反射膜 只读式光盘 |
| 其他题名 | Study on the Sb-type Super-resolution Near-field Structure Optical Storage Technique and Mechanism |
| 中文摘要 | 本文的主要内容包括以下几个方面的研究工作：Sb和SIN等薄膜的制备及光学性能研究；脉冲激光作用下sb薄膜的结构变化及相应的光学性能；激光作用下Sb薄膜的折射率随温度的变化；Sb薄膜的超分辨自聚焦近场热透镜模型及光场分布的FDTD法模拟；基于Sb掩膜的超分辨近场结构（SuPer-RENS）的静态记录性能；基于超分辨反射膜结构的只读式光盘研究．首先较全面地综述了超大容量、超高密度光存储技术的研究现状及发展趋势，对掩膜超分辨及近场光存储技术的原理、研究历程及各自的优缺点进行了分析和比较，重点分析和讨论了掩膜超分辨近场结构的研究发展进程，提出了本论文研究的具体内容．通过直流磁控溅射法制备了Sb、SiN、Si、Ti和Al薄膜，优化得到Sb和SiN薄膜的溅射工艺条件为：①最佳的SiN薄膜的制备工艺为溅射气压O.70pa、氧氢比4:3和溅射功率为500W，溅射速率为Inm／s，所得到的SIN薄膜的在可见光波长（350一85onm）的透射率为80一90％，复折射指数为n＋ik=1.86（土0.03）＋10.0025（士0.001）；②sb薄膜的最佳制备工艺为溅射功率220w、溅射气压0.70Pa和溅射速率为0.80nm／s，所得薄膜的平均表面粗糙度为8一10A．对于厚度为20nm的sb薄膜而言，在可见光波长内（（350一850nm）的折射率n随波长线性增加，消光系数k随波长先增大再减小，其晶态到熔化态的温度转变区间为550一600℃，相应地透射率从10.5％突变到16.5％．研究了Sb薄膜在脉冲激光作用下的结构转变（晶态～熔化态一固态（晶态））过程，该过程分为三个阶段：激发光渗入深度内材料的形核熔化、熔前传播和晶化过程．随着激发光功率密度的增加，形核熔化时间降低．熔前传播时间也逐渐降低．然而，晶化时间不随激发光功率密度的变化而显著变化，基本维持在150ns左右．采用熔化形核理论、熔前传播过程和结晶原理得到了上述三个过程的计算方程及分析模型，通过该模型计算得到的结果与实验数据基本吻合．通过时间分辨的热透镜效应方法得到了sb薄膜的折射率随温度的变化规律：在低于865K时，折射率基本不随温度的变化；在865一928K，折射率随温度升高而呈线性增加，在高于928K时折射率基本不变．采用Lorentz-Lorenz关系分析发现折射率随温度变化的机理是由于Sb薄膜由晶态到非晶态（熔化态）转变的过程中的温度升高使得其结构变成较为离解的状态，这个离解态导致原子群（atomic groupings）的尺寸降低，因此电子极化率增加，从而使得电子极化率的温度系数为正数，因此折射率也相应增加．根据Sb薄膜折射率随温度变化规律，提出了Sb薄膜在记录或读出激光束作用下的超分辨自聚焦近场热透镜模型，即Sb薄膜首先在聚焦激光光斑的中央形成一个动态的超分辨“光孔”，由于“光孔”内折射率的高斯分布，聚焦光斑会发生自聚焦，因此将该“光孔”看作一个超分辨自聚焦热透镜，通过计算发现，Sb薄膜超分辨自聚焦热透镜在近场距离内不仅能进一步减小光斑，且光斑强度得到了增强，利用该结果成功地解释了Sb薄膜在该结构中的工作机理．同时通过FDTD方法对·该热透镜的近场光分布进行模拟，发现在距Sb薄膜的出射面大约16nm处形成一个聚焦的椭圆光斑，其直径小于100nm，强度较入射前明显增强，使用Sb掩膜超分辨近场结构的试样，“SiN（120nm／Sb（30nm）／SiN（15nm）／Ge2Sb2Te5（15nm）”在静态装置上（激光波长650nm、物镜的数值孔径0.90）得到了直径为25028Onm的记录点，该记录点小于测试装置的分辨极限（44onxn），这也与我们的Sb薄膜超分辨自聚焦近场热透镜模型基本相符．提出一种新的超分辨反射膜结构“介电层／超分辨反射膜／介电层”，并应用于只读式超分辨光盘，以SiN作为介电层，分别以Sb、Si和Ti作为超分辨反射膜，在读出激光波长为632.8nm，光学头数值孔径为0.40的动态装置上成功地实现了直径为380nm的超分辨记录点的读出，其中读出信噪比均随着超分辨反射膜的厚度增加而先增大再减小．对于Sb超分辨反射膜结构，最佳的Sb薄膜厚度为30nm，相应地超分辨记录点的读出信噪比为38-4OdB；对于Si超分辨反射膜结构，最佳的Si薄膜厚度qw为18nm，相应地超分辨记录点的读出信噪比为30-32dB；对于Ti超分辨反射膜结构，最佳的Ti薄膜厚度为16-18泌，相应地超分辨记录点的读出信噪比为28-3OdB． |
| 英文摘要 | The dissertation is made up of the preparation and optical properties of Sb and SiN thin films, the structural and the corresponding optical properties change of Sb thin films under pulse laser irradiation, the super-resolution self-focusing near-field thermal lens model of Sb thin films and its near-field optical simulation by FDTD method, the static recording properties of Sb-type super-resolution near-field structure (super-RENS), and the read-only super-resolution optical disk by the super-resolution reflective film structure. At first, the current status and the development trend of the ultrahigh density and ultra-large capacity optical storage techniques are reviewed. A detailed and comprehensive overview on the principles and their improvement of mask super-resolution and near-field optical storage techniques, at the same time, the research subject in my work is also proposed. The SK SINN SK Ti and Al thin films are prepared by the d.c. sputtering method. The optimum preparation conditions of SiN thin films are that the sputtering pressure is 0.70Pa, the ratio of Ar to O2 is 4:3, the sputtering power is 500W, and the sputtering rate .is lnm/s; The transmission of SiN thin films prepared by above optimum conditions is 80～90%, and the complex refractive index at wavelength of 632.8nm N = (n + ik) is 1.86(±0.03) + 0.0025(±0.001)i . The optimum preparation conditions of Sb thin films are that the sputtering pressure is 0.70Pa, the sputtering power is 220W, and the sputtering rate is 0.8nm/s; the rms thickness of thin films is 8-10A. For the Sb thin films with a thickness of 20nm, the refractive index n linearly increases, however, the extinction coefficient k increases at first, and then decreases with the change of wavelength from 350nm to 850nm, the structural transformation temperature between crystalline and melted states ranges from 550 to 600 ℃, correspondingly, the transmission abruptly changes from 10.5% to 16.5%. The structural transformation (crystalline-smelted crystalline)of Sb thin films under pulse laser irradiation is investigated. It can be divided into three stages: the first stage is the nucleation and melting of Sb within the penetration depth of laser; the second stage is melting front propagation; the third is crystallization of melted Sb thin films. The results show that the time of nucleation melting and the melting front propagation decreases with the increase of laser power density, however, the crystallization time is basically unchanged and keeps at about 150ns. By using the melting nucleation theory, melting front propagation process, and the crystallization principle, the calculating and analytical equations and model on the above three stages are derived, and the calculated results are basically consistent with those of experiments. The change law of refractive index n of Sb thin films with temperature is measured by the time-resolved thermal lens effect method, and its mechanism is analyzed. According to the experimental results, a super-resolution self-focusing near-field thermal lens model of Sb thin films in super-RENS is proposed, correspondingly, the working mechanism is given by using this model. At the same time, the near-field optical profiles of the model are simulated by the FDTD method, the results show that an intensity enhanced and focused optical spot can be formed through the Sb thin films, its size is further smaller than the optical wavelength, and the intensity is greatly increased. Using a super-resolution near-field structure "SiN(120nm)/Sb(30nm)/SiN(15nm)/Ge2Sb2Te5(15nm)", the recording domains with a size of250～280nm are obtained by the static recording setup whose laser wavelength is 650nm, and numerical aperture of lens is 0.90, which indirectly testifies the super-resolution self-focusing near-field thermal lens model of Sb thin films in super-RENS. A novel super-resolution reflective film structure "dielectric layer/reflective layer/dielectric layer" is proposed, and is applied to read-only optical disk. Using the SiN as the dielectric layer, Sb > Si and Ti as the reflective layer, respectively, the super-resolution pits with a diameter of 38Onm, and depth of 50nm are read out in the dynamic setup whose laser wavelength is 632.8nm, numerical aperture of lens is 0.40. For Sb thin films, the optimum thickness is 30nm, the corresponding readout carrier-to-ratio (CNR) is 38～40dB; for Si thin films, the optimum thickness is 18nm, the corresponding CNR is 30～32dB; for Ti thin films, the optimum thickness is 16-18nm, the corresponding CNR is 28-3OdB. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15360]  |
| 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 | 魏劲松. Sb掩膜型超分辨近场光存储技术及机理研究[D]. 中国科学院上海光学精密机械研究所. 2004. |
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