SrTiO3金属-绝缘体-半导体结构的介电与界面特性

采用金属有机分解法在p型Si衬底上制备了SrTiO3（STO）薄膜.研究了STO薄膜金属 绝缘体 半导体(MIS)结构的介电和界面特性.结果表明，STO薄膜显示出优异的介电性能，在10kHz处的介电常数约为105，损耗低于001，这来源于多晶结构和良好的结晶性；MIS结构中的固定电荷密度Nf和界面态密度Dit分别约为15×1012cm-2和(14—35)×1012cm-2eV-1，这主要与Si/STO界面处形成的低介电常数界面层有关. 关键词： SrTiO3薄膜 MIS结构 介电性能 Si/STO界面     

SrTiO3金属-绝缘体-半导体结构的介电与界面特性

采用金属有机分解法在p型Si衬底上制备了SiTiO3(STO)薄膜.研究了STO薄膜金属-绝缘体-半导体(MIS)结构的介电和界面特性.结果表明,STO薄膜显示出优异的介电性能,在10kHz处的介电常数约为105,损耗低于0.01,这来源于多晶结构和良好的结晶性;MIS结构中的固定电荷密度Nf和界面态密度Dit分别约为1.5×1012cm-2和(1.4-3.5)×1012 cm-2 eV-1,这主要与Si/STO界面处形成的低介电常数界面层有关.     

光波导技术同步测量棱镜及波导薄膜参数

依据全反射理论和棱镜耦合原理,实现了对棱镜折射率及波导薄膜材料折射率和厚度的同步测量。使用高准直半导体激光器激光入射到棱镜内部与波导膜的分界面上,逐步旋转棱镜或改变棱镜的入射角,得到棱镜耦合M线,曲线前面几组的波谷为波导模激发,在M线左侧收尾处有一个不完整波峰,其反射光强随入射角迅速衰减,为全反射时的临界点,由此可实现棱镜及波导薄膜参数的同步测量;用此法测量了棱镜耦合一体化平面波导棱镜的折射率和聚甲基丙烯酸甲酯(PMMA)聚合物波导薄膜的折射率和厚度。测量棱镜折射率精度为±1.9×10-4,波导薄膜折射率和厚度的精度分别为±6.2×10-4 μm和±1.6×10-2 μm。     

两种不同(Ba,Sr)TiO3薄膜介电-温度特性的研究

研究并比较了两种不同(Ba_0.5,Sr_0.5)TiO₃(BSTO)薄膜介电-温度特性.采用脉冲激光沉积技术在Pt/Ti/SiO₂/Si(100)衬底上制备BSTO薄膜，发现制备条件的不同，可以得到介电性质完全不同的BSTO薄膜.在550℃和氮气氛下制备的BSTO薄膜在常温下具有很高的介电常数，在10kHz下，超过2500，并在200K温度以上介电常数基本不变.它的一些电学性质不同于在正常条件(650℃和氧气氛下)制得的BSTO薄膜，而类似于目前广泛报道的巨介电常数材料如CaCu_３Ti_４O₁₂.两种薄膜介电性质测试结果表明: 氧气氛下制备的BSTO薄膜呈现铁电-顺电相变，符合居里-外斯定律；低温氮气氛下制备的BSTO薄膜，介电弛豫时间和温度的关系符合德拜模型，是热激发弛豫.文中给出了产生这种介电特性的初步解释. 关键词： 薄膜 脉冲激光沉积 介电弛豫     

双层锰氧化物薄膜的制备及其物理性质

用脉冲激光沉积(PLD)方法成功地制备了双层钙钛矿结构的La2-2xSr1+2xMn2O7(x=032)单相薄膜.这种薄膜生长在具有不同晶格参数的两种衬底上.测量发现，两种衬底上生长的La2-2xSr1+2xMn2O7(x=032)薄膜具有迥然不同的金属-绝缘体转变温度TM-I及其他物性.界面应力的研究表明这是衬底晶格常数不同引起膜内应变的结果.在衬底的压应力下，薄膜的电阻-温度曲线的峰值(TM-I)向高温移动且电阻率(ρ)下降；相反，对于衬底张应力下的薄膜，TM-I下降ρ上升.这些结果可以用双交换模型做很好的解释. 关键词： CMR 双层锰氧化物薄膜 PLD 应力     

用光栅耦合器测量波导薄膜参数的一种方法

本文研究了用光栅耦合器测量波导薄膜参数的新方法。我们对在F1玻璃衬底上真空蒸发制作的硫化锌薄膜和在K9玻璃衬底上浸涂法制作的环氧树脂薄膜的参数进行了测量。采用的光栅周期分别为1200mm~(-1)、1800mm~(-1)和2400mm~(-1)。测量结果表明:薄膜波导模式有效折射率观测值m与计算值N_m符合得较好。计算测量有效折射率M和薄膜折射率n_f的精度高于0.1％,计算测量薄膜厚度的相对精度△W/W为2.8～0.1％。我们认为,在导波光学和半导体工艺中,光栅耦合器和棱镜耦合器一样,是快速而精确地测定波导薄膜参数的有效方法。而且,光栅耦合器尚且有它自己的特点。最后还简要地讨论了带有光栅结构的棱镜耦合器。     

Sr0.75Ba0.25Nb2O6薄膜的PLD制备及其光学性能研究

本文采用脉冲激光沉积(PLD)方法在熔石英衬底上制备了Sr0.75Ba0.25Nb2O6(SBN0.75)光波导薄膜,采用Hitachi U-3410紫外-可见分光光度计对SBN0.75薄膜的透射谱进行测量,编程计算得到了薄膜折射率色散关系,同时得到SBN0.75薄膜的厚度和光学带隙分别为647.0nm和3.97eV。采用Metricon 2010棱镜耦合仪测量得到SBN0.75光波导薄膜中能激发的TE模式有4个,TM模式有3个。波长在632.8nm处薄膜的折射率为2.2818。并利用透射谱计算得出的薄膜的折射率和厚度值,根据波导理论导光模本征值的有效折射率表达式,对SBN0.75薄膜中能激发的导光模个数及其对应有效折射率进行图解,其结果与棱镜耦合仪所测得的结果非常吻合。     

两种不同(Ba,Sr)TiO3薄膜介电-温度特性的研究

研究并比较了两种不同(Ba0.5,Sr0.5)TiO3(BSTO)薄膜介电-温度特性.采用脉冲激光沉积技术在Pt/Ti/SiO2/Si(100)衬底上制备BSTO薄膜,发现制备条件的不同,可以得到介电性质完全不同的BSTO薄膜.在550℃和氮气氛下制备的BSTO薄膜在常温下具有很高的介电常数,在10kHz下,超过2500,并在200K温度以上介电常数基本不变.它的一些电学性质不同于在正常条件(650℃和氧气氛下)制得的BSTO薄膜,而类似于目前广泛报道的巨介电常数材料如CaCu3Ti4O12.两种薄膜介电性质测试结果表明: 氧气氛下制备的BSTO薄膜呈现铁电-顺电相变,符合居里-外斯定律;低温氮气氛下制备的BSTO薄膜,介电弛豫时间和温度的关系符合德拜模型,是热激发弛豫.文中给出了产生这种介电特性的初步解释.     

TE0导模干涉刻写周期可调亚波长光栅理论研究

通过棱镜耦合激发非对称金属包覆介质波导结构中的TE₀导波模式, 利用两束TE₀模的干涉从理论上实现了周期可调的亚波长光栅刻写. 分析了TE₀模式的色散关系, 刻写亚波长光栅的周期与激发光源、棱镜折射率、光刻胶薄膜厚度及折射率之间的关系. 用有限元方法数值模拟了金属薄膜、光刻胶薄膜和空气多层结构中TE₀导模的干涉场分布. 研究发现, 激发光源波长越短, TE₀ 模干涉刻写的亚波长光栅周期越小; 光刻胶越厚, 刻写的亚波长光栅周期越小; 高折射率光刻胶有利于更小周期亚波长光栅的刻写. 相较于表面等离子体干涉光刻, 基于TE₀ 模的干涉可在厚光刻胶条件下通过改变激发光源、棱镜折射率、光刻胶材料折射率、特别是光刻胶薄膜的厚度等多种方式实现对亚波长光栅周期的有效调控.     

介电润湿液体光学棱镜

为实现光束控制系统的无机械化、快速化和微小化,研制基于介电润湿效应的液体光学棱镜。分析界面形状随电压的变化,推导接触角与两侧工作电压的关系,测量系统对光束的偏转角,讨论接触角饱和及液体折射率对系统控光能力的影响。采用COMSOL软件仿真研究液体粘性对棱镜性能的影响。结果表明,在不同电压组合下,双液体界面从初始弯曲界面变为与水平方向呈不同倾斜角的平界面,从而实现对入射光束方向的控制和偏转。受电润湿饱和现象的影响,该液体棱镜的偏转范围为-10°~+10°。若选用的液体组合可降低甚至消除接触角饱和,且具有大的折射率比,则系统的控光能力将得到大幅提高。当动力粘度取0.03Pa·s时,系统的响应速度和稳定性能最佳。     

Nonlinear s-polarized surface plasmon polaritons

We have examined the dispersion relations for s-polarized surface plasmon polaritons, guided by (a) the interface between a semi-infinite metal and dielectric medium, and (b) a metal film bounded by semi-infinite dielectric media for situations in which one or more of the dielectric media are characterized by an intensity-dependent refractive index. We found that s-polarized waves satisfy the dispersion relations for very thin metal films bounded by nonlinear dielectric media. These waves exist only for power levels above a threshold that depends on the material parameters. We also comment on the experimental feasibility of observing these waves.     

Charge interaction in layered systems with spatial dispersion

The potential electrostatic energy of a charge near the surface of a metal with a metal or a dielectric coating (adsorbate), on the interface between metal (semimetal) and insulator (electrolyte) and in layered thin-film sandwich-type systems (MIS structures) has been calculated. The influence of the metal and the dielectric epitaxial coatings of the metal surface upon the interaction of charges is investigated. Taking into account the spatial dispersion effects, it is shown that in thin films surrounded by a medium with a large dielectric constant, the Coulomb repulsion between electrons decreases.     

Absorption of surface plasmons in a metal-cladding layer-air structure in the terahertz frequency range

The effect of a thin dielectric cladding layer of a metal on the absorption of surface plasmons (SPs) in the terahertz frequency range is studied experimentally and numerically. It is found that, as the radiation wavelength increases, the attenuation of SPs caused by the cladding layer can increase by a factor of ～10⁴ as compared to the absorption of SPs propagating along the unperturbed metal-air interface. Data obtained in experiments with germanium-cladded aluminum specimens using radiation from a terahertz free-electron laser (v = 90 cm^?1) confirm that application of a dielectric cladding on the metal surface causes the SP absorption to increase.     

Film thickness measurement by frustrated total reflection fluorescence

If the interface between a dielectric surface and an adjacent, fluorescing, medium of lower refractive index is illuminated by a collimated light beam, an exponentially decaying evanescent wave is generated in the fluorescing medium. The electric field of the evanescent wave generates easily measurable fluorescence. If part of the surface is covered with a dielectric film, the fluorescence generated is smaller, since some of the decaying wave occurs in a non-fluorescing medium. Measurement of the difference between the fluorescing signals enables the non-destructive measurement of the film thickness to be made. Several questions arise, for example (i) what angle of incidence should be used, (ii) how is the sensitivity influenced by the substrate refractive index, (iii) should p-or s-polarized light be used, (iv) what sensitivity is attainable? This paper answers these questions and indicates that films of the order of a nanometre in thickness are detectable.     

Optical characterization of oxynitride films in the visible-ultraviolet range

Oxynitride optical properties in the visible-ultraviolet spectral range are very interesting, due to their use in electronic device manufacturing. This paper presents spectra of refractive index and extinction coefficient of oxynitride films deposited on silicon with different composition, as derived from spectroscopic ellipsometry measurements on the basis of an effective medium approach. These data evidence the presence of a Si-rich layer on the oxynitride/silicon interface. Electronic polarizability and energy gap of all compounds were evaluated. Moreover, absolute reflectance of the samples was derived from optical functions and compared with the measured value.     

不同浓度Cu掺杂AlN的电子结构和光学性质研究

采用基于密度泛函理论的平面波超软赝势和广义梯度近似的第一性原理计算方法,对理想纤锌矿AlN及不同浓度的Cu掺AlN的超晶胞结构进行了几何优化,计算并分析了它们的电子结构、磁电性质和光学性质.结果表明,掺杂后Cu3d态电子与其近邻的N2p态电子发生杂化,在带隙中引入杂质带,6.25%和12.5%的Cu掺杂体系表现出半金属铁磁性,体系总磁矩分别为2.56μв和2.42μв,25%的Cu掺杂体系表现出金属性.随着Cu浓度的增加,体系铁磁性反而减弱.Cu掺杂后体系介电函数虚部和复折射率函数在低能区发生明显变化,增强了体系对低频电磁波的吸收.当Cu浓度增加时体系对高频电磁波的吸收也随之加强.     

双负媒质结构改善Ku波段天线辐射特性

基于负介电常数和负磁导率产生原理,采用金属细线和裂环谐振器结构,针对12.5 GHz频率开展双负媒质结构设计。通过特殊边界条件下S参数计算以及Nicolson-Ross-Weir方法,完成等效参数的提取,获得介电常数、磁导率、折射率实部均为负值,且折射率接近于0的左手材料特性。将双负媒质结构加载于Ku波段圆锥喇叭口面进行仿真优化,提高天线增益2.17 dB,在11~13 GHz频带范围内,加载天线的增益均有所改善。实验结果表明,口面加载双负媒质结构后,天线增益提高1.51 dB,后向辐射减小5.7 dB,辐射特性获得了明显改善。     

室温和液氮温度Si基底C60薄膜的微观结构与光学特性比较研究

在室温和液氮温度（77K）下用蒸镀法在Si(111)衬底上制备C60薄膜，用扫描电子显微镜（SEM）研究两种不同基底上制备薄膜的微观结构，并用椭圆偏振光谱仪测量了光学参数（包括吸收光谱，折射率及光频介电常数），结果表明，衬底温度降低，薄膜更均匀，颗粒更细，光学吸收峰位置出现蓝移且在整个光频范围吸收增强。     

Surface exciton modes for plane and spherical semiconductor-metal interfaces

An approximate method is developed for investigating the nature of interface exciton modes in a composite spatially dispersive medium. The method is general enough to be applicable to any composite system, in which each component is described by an arbitrary bulk dielectric functionε(q, ω). It is based on the extension of the usual electrostatic-image method of solving the Poisson’s equation, in the presence of an external point charge in the system. We have applied our general method to a composite system of a finite metal slab surrounded by a semiconductor on one side and the vacuum on the other side. Similarly, we have also considered the case of a metallic sphere of radiusR, surrounded by a semiconductor, with a spherical interface between them. With assumed spatially dispersive model dielectric functions for the bulk metal and the bulk semiconductor, the nature of the electron-electron interaction and the interface exciton modes in the metallic region are obtained in both the cases. For the relevant size of the metal large compared to the atomic dimensions over which the bulk dielectric functions are non-local due to the spatial dispersion, it is shown that one can obtain the interface exciton modes by first defining new effective dielectric functions for each of the media making the particular interface, and then using the usual expression which determines the modes in the non-dispersive case.