金属薄膜厚度小于电子自由程对其光反射率的影响

提出了金属薄膜厚度对薄膜中自由电子的平均自由程影响的物理模型,并给出了薄膜中自由电子的平均自由程的修正公式.理论研究表明:当膜厚小于自由电子的平均自由程时,薄膜中电子平均自由程随膜厚的减小而减小;当膜厚大于或等于自由电子的平均自由程时,薄膜中电子的平均自由程与块状材料一样.利用薄膜中电子平均自由程的计算公式,修正了薄膜...     

飞秒激光抽运探测热反射法对金属纳米薄膜超快非平衡传热的研究

随着微电子器件尺寸的减小、 工作频率的提高, 金属薄膜中电子与声子将处于非平衡状态, 这将导致微电子器件的热阻增大. 为准确地对这些微电子器件进行热管理, 电子-声子耦合系数的测量变得越来越重要. 本文采用飞秒激光抽运-探测热 反射法研究了不同厚度的金属纳米薄膜的非平衡传热过程. 通过抛物两步模型对实验数据进行拟合, 在拟合过程中引入电子温度与声子温度对反射率影响的比例关系, 从而优化了拟合结果. 通过对不同厚度的Ni膜与Al膜的电子-声子耦合系数的研究, 表明金属薄膜中的电子-声子耦合系数并不随薄膜厚度的改变发生变化. 实验结果还验证了探测光的反射率同时受到电子温度和声子温度的影响, 并通过数据分析量化了电子温度和声子温度对反射率的影响系数.     

磁控溅射制备铬薄膜的结构和光电学性质(英文)

用直流磁控溅射技术在石英基片上制备不同厚度(5nm～114nm之间)的铬膜.使用X射线衍射仪和分光光度计分别检测薄膜的结构和光学性质,利用德鲁特模型和薄膜的透射、反射光谱计算铬膜的厚度和光学常量,并采用Van der Pauw方法测量薄膜电学性质.结果表明:制备的铬薄膜为体心立方的多晶态,随着膜厚的增加,薄膜的结晶性能提高,晶粒尺寸增大;在可见光区域,当膜厚小于32nm时,随着膜厚的增加,折射率快速减小,消光系数快速增大,当膜厚大于32nm时,折射率和消光系数均缓慢减小并逐渐趋于稳定;薄膜电阻率随膜厚的增加为一次指数衰减.     

磁控溅射制备铬薄膜的结构和光电学性质

用直流磁控溅射技术在石英基片上制备不同厚度(5 nm~114 nm之间)的铬膜.使用X射线衍射仪和分光光度计分别检测薄膜的结构和光学性质,利用德鲁特模型和薄膜的透射、反射光谱计算铬膜的厚度和光学常量,并采用Van der Pauw方法测量薄膜电学性质.结果表明:制备的铬薄膜为体心立方的多晶态,随着膜厚的增加,薄膜的结晶性能提高,晶粒尺寸增大;在可见光区域,当膜厚小于32 nm时,随着膜厚的增加,折射率快速减小,消光系数快速增大,当膜厚大于32 nm时,折射率和消光系数均缓慢减小并逐渐趋于稳定;薄膜电阻率随膜厚的增加为一次指数衰减.     

金属颗粒薄膜巨磁电阻效应的影响因素

研究金属颗粒薄膜的颗粒尺寸、磁性组分等对巨磁电阻效应的影响.在自由电子模型和自旋相关散射理论的基础上，计算了金属颗粒膜体系的电子平均散射势.在计算过程中将自旋相关项与宏观量相联系，得到了巨磁电阻效应与磁性成分比例、颗粒尺寸的关系.磁电阻效应的模拟曲线表明，增加磁性成分比例和减小磁性颗粒尺寸可增强颗粒膜的巨磁电阻效应. 关键词：     

单晶硅薄膜法向热导率分子动力学研究

采用非平衡分子动力学方法（NEMD）研究了平均温度为 500K、厚度为 2～32nm的单晶硅薄膜的法向热导率。模拟结果表明,薄膜热导率显著低于对应温度下的体硅单晶的实验值,并随膜厚度减小以接近线性的规律减小。用声子气动力论模型的分析结果与NEMD模拟相一致,表明纳米单晶硅薄膜中声子平均自由程显著减小。     

Cu膜的光学特性尺寸效应及最小连续膜厚研究

采用离子束溅射在K9玻璃基底上沉积了不同厚度的Cu膜,利用Lambda-900分光光度计,测量了波长为310 nm到1300 nm范围内Cu膜的反射率和透射率.选定波长为310、350、400、430、550、632、800、1200 nm时对薄膜的反射率、透射率和吸收率随膜厚变化的关系进行研究.同时,对Cu膜的光学常量也进行了讨论.结果显示,Cu膜的光学特性都有明显的尺寸效应.将波长为550 nm时的反射率和透射率随Cu膜厚度变化关系的交点对应厚度作为特征厚度, 该厚度可认为是金属Cu膜生长从不连续膜进入连续膜的最小连续膜厚.根据这一特征判据,离子束溅射沉积Cu膜样品的最小连续膜厚为33 nm.利用原子力显微镜观测了膜厚在特征厚度附近时Cu膜的表面形貌.     

金属薄膜的量子输运理论

运用格林函数方法和久保公式研究金属薄膜中的电子输运．考虑了量子尺寸效应及来自杂质和两个粗糙表面的散射，计算单粒子格林函数和平行电导率．计算结果表明：（1）在薄膜系统中，电子数密度、平均自由程以及来自杂质和表面散射的电导率都以π/k_F（k_F为费密波矢的数值）为周期随厚度d振荡；（2）在薄膜和厚膜的两种极限、以及取表面粗糙度的最低阶近似下的结果可以推出用半经典和量子方法所得的金属薄膜的电导公式 关键词：     

三维a-IGZO薄膜中的电子—电子散射

本文利用射频磁控溅射法制备了一系列厚度约800 nm的非晶铟镓锌氧化物(a-IGZO)薄膜,并对其电输运性质和低温的电子退相干机理进行了系统的研究.研究发现,所有a-IGZO薄膜中,载流子浓度均不随温度变化,高温区的电阻-温度系数为正,说明样品具有类金属导电特性.通过对薄膜低温磁电阻的测量,获得了电子退相干散射率与温度的关系.分析表明,薄膜中电子-声子散射率远小于小能量转移电子-电子散射率,小能量转移电子-电子散射率主导电子退相干散射率与温度的依赖关系.     

磁控溅射不同厚度银膜的微结构及其光学常数

用直流溅射法在室温K9玻璃基底上制备了8.2nm—107.2nm范围内不同厚度的Ag薄膜，并用X射线衍射及计算机辅助优化程序对薄膜的微结构和光学常数进行了测试分析. 结构分析表明：制备的Ag薄膜均呈多晶状态，晶体结构均呈面心立方；随着膜厚的增加，薄膜的平均晶粒尺寸逐渐增大，晶面间距逐渐减小. 计算机辅助优化编程计算的薄膜光学常数分析表明：在波长550nm处，当膜厚小于17.5nm时，随着膜厚的增加，折射率n快速减小，消光系数k则快速增大；当膜厚大于17.5nm时，n和k逐渐趋于稳定. 关键词： 直流溅射镀膜 银膜 微结构 光学常数     

Conductivity of single-crystal and polycrystalline bilayer metal films under the conditions of interdiffusion

The electrical conductivity of a bilayer film with a single-crystal or polycrystalline structure is theoretically investigated under the conditions of metal interdiffusion at an arbitrary ratio between the thickness of layers and the mean free path of electrons in the layers. It is shown that analysis of the changes in the electrical conductivity of the bilayer film due to diffusion annealing allows one to elucidate the nature of the processes of bulk and grain-boundary diffusion, to determine the effective depth of penetration of impurity atoms into the bulk and grain boundaries of the sample, and to obtain information on the bulk and grain-boundary diffusion coefficient.     

Effect of Boundary Conditions on the Electrical and Galvanomagnetic Properties of a Thin Metal Film

The problem of determining the high-frequency electrical conductivity and Hall constant for a thin metal film placed in a transverse stationary magnetic field and in a longitudinal alternating electric field is solved by the kinetic method. The relation between the film thickness and electron free path length is supposed to be arbitrary. The skin effect is not taken into account. The diffuse-specular mechanism of electron reflection from the film boundaries is considered with similar specular-reflection coefficients for the upper and lower surfaces of the film taken into account. The electrical conductivity and Hall constant are studied as functions of dimensionless parameters: electric-field frequency, magnetic-field induction, and film thickness.     

Ultrasonic attenuation of metals at low temperatures

At very low temperatures when the mean free path of the electrons in metals becomes large but less than the wavelength of sound wave a relationship between electrical conductivity and attenuation in the normal state has been deduced byMason using the mean free path associated with the electrical conductivity. Similarly, a relationship between thermal conductivity and attenuation can be deduced using the mean free path associated with the thermal conductivity. It has been shown from experimental results that the relationship thus deduced agrees better in the temperature region discussed in the paper. When the mean free path becomes greater than the wavelength, α_s/α_n, the ratio of superconducting attenuation to that in the normal state can be determined in accordance with the theory ofBardeen, Cooper andSchrieffer. It is apparent from experimental results that in the limited region where the scattering of electrons is predominantly by lattice vibrations, K_s/K_n, the ratio of superconducting thermal conductivity to that in the normal state is equal to α_s/α_n.     

Calculation of the RF Conductivity and Hall Constant of a Thin Metal Film

The kinetic problem of finding the rf conductivity and Hall constant of a thin metal film placed in a transverse steady magnetic field and a longitudinal variable electric field has been considered. It has been assumed that electrons diffusely reflect from the upper and lower surfaces of the film. No limitations have been imposed on the relationship between the thickness of the film and the electron free path. The dependences of the conductivity and Hall constant on dimensionless parameters, namely, electric field frequency, magnetic field induction, and thickness of the film, have been studied. Calculation results have been compared with the experimental data.     

Ultrasonic mean free path in a granular aluminum film

The ultrasonic mean free path has been measured and compared to the electrical mean free path of a thin granular aluminum film. They have been found to differ by an order of magnitude which is believed to indicate that mean free path determined ultrasonically is for the Al metal while the one determined electrically is for the Al-Al₂O₃ matrix structure.     

Optical properties change of oxide film — metal system during the film growth: computer simulation

Results of computer simulation of reflective properties of the oxide film-metal system in the process of oxidation in the air environment are presented. The complex refractive indices for oxide film and metal were used as the initial data. Thin films (the thickness is comparable with the wavelength of incident radiation) and thick films (thickness is much larger than the wavelength of incident radiation) are considered. The parameter characterizing the cyclic character of system reflectivity during the growth of film thickness was derived for the thin film. It is shown that the cyclic parameter does not depend on optical properties of a metal substrate. In the air environment, this parameter is determined by a complex refractive index of the film, its thickness, and direction of incident radiation. Relationships for the estimate of system reflectivity in the process of oxide film growth are presented for the thick film.     

基于SPR的类铬型金属膜厚在线纳米测量研究

当具有足够大发散角的柱面光照射在匀厚金属薄膜表面时,由表面等离子体振荡产生的光反射率角分布是膜厚的函数,用CCD接收反射光分布信息并经过计算机分析处理,可实时、在线测量10nm内的铬、钛等金属膜厚,这类金属的复介电常数的实部相对虚部是较小的负数,故具有强反射锐峰及较平坦的吸收峰,该两峰点可作为膜厚测量依据的特征标记点,并通过建库进行曲线匹配而获得膜厚数值。实验结果表明,该方法的平均测量误差可低于0.4nm。     

Investigating the surface morphology and magnetic contrast of epitaxial ferromagnetic structures

The surface morphology of nickel thin films is investigated via atomic force microscopy. The multistage film growth mechanism is found to be dependent on substrate temperature and film thickness. It is shown that conduction electron scattering from the irregularities of the outer and inner surfaces of structures are influenced by the surface morphology and determined by an integrated contribution of the surface’s fluctuation density spectrum. The morphology influence can be decreased under certain growth conditions so that the residual mean free path of conduction electrons can reach 1000 nm, exceeding the film thickness. Epitaxial nanostructures with high electron mobility have been fabricated. Investigation of their magnetic structure has shown that their magnetic domain dimensions are less than the residual mean free path of electrons determined by the surface morphology.