基于AlAs/InGaAs/GaAs共振隧穿效应的纳机电声传感器研制

本工作设计了一种基于AlAs/InGaAs/GaAs量子隧穿效应的纳机电拍子式声传感器,并采用ANSYS有限元分析软件对敏感元件的布置位置进行了最优化仿真设计.在加工工艺上,采用双空气桥技术和Au/Ge/Ni合金膜系欧姆接触技术有效降低了电容、电阻等对器件结构性能的影响;在传感器的具体加工过程中,共振隧穿结构(RTS)和拍子结构是通过控制孔技术一次流片完成的.对所加工的传感器进行了初步测试,结果表明,传感器频响能较好的与仿真结果相吻合,1.3KHz时同时具有较好的线性特性.     

肖特基栅型共振隧穿三极管器件模型的研究

基于共振隧穿二极管(RTD)的电流-电压方程,结合对肖特基栅型共振隧穿三极管(SGRTT)物理机制的分析和计算,推导出了SGRTT器件的器件模型。根据实际器件的材料结构、版图参数等指标计算得到的SGRTT器件模型,能很好地与实际器件的特性相吻合。利用PSPICE软件,该模型可准确快捷地实现电路功能验证和仿真,此项研究的结果为共振隧穿器件的电路集成和研制奠定了基础。     

短稳标准高Q值超导腔的研究

针对频率标准用超导腔的设计,通过理论分析及编程计算得到了影响微波腔指标的参数,并对不同温度下微波腔的品质因数（Q值）进行计算得到了温度变化曲线,通过此曲线可以确定达到指标所需要的温度。所设计的微波腔参数为：工作模式为TM₀₁₀模式,直径D为60mm,高度l为50mm,频率为4.4GHz,Q值在液氦温度4.2K时达到3.9×10⁷,在减压降温到2K时达到1.9×10⁹,实验结果与计算结果吻合。     

极化效应对AlN/GaN共振隧穿二极管电流特性的影响

本文采用半经验紧束缚能带理论,通过自洽计算薛定谔方程和泊松方程研究了AlN/GaN共振隧穿二极管中极化效应对电流的影响.结果发现,极化效应导致电流曲线发生不对称性,并影响电流的共振电压位置,这与实验报道的结果相一致.并且随着极化电荷的增加,在一定的偏压条件下,只能观测到一个子能级隧穿或者根本没有负微分电阻现象发生.     

隧穿型量子效应薄膜材料制备技术

探讨了隧穿型量子效应薄膜材料制备技术,并应用分子束外延方法制备了典型结构外延材料GaAs基共振隧穿二极管,经过器件验证,得到了较好的结果.重点讨论了关键制备技术,包括束流精细控制和间歇式生长方式,主要是为了生长出更接近完美的晶体结构和晶体表面,并分析了测试结果和器件验证结果,最终得出整套隧穿型量子效应薄膜材料制备技术.     

金纳米锥阵列与金薄膜耦合结构表面等离子体折射率传感研究

设计了基于SiO₂薄膜间隔的金纳米锥与金薄膜耦合结构表面等离子体共振折射率传感器。使用时域有限差分法研究了复合结构中的表面等离子体共振模式,复合结构不仅能够激发局域表面等离子体共振,也可激发传播表面等离子体共振。入射电磁波的能量部分通过单个金纳米锥耦合到局域表面等离子体,部分通过金纳米锥阵列二维光栅耦合到传播表面等离子体。在待测物折射率1.30～1.40的范围内,对复合结构的反射光谱进行了模拟研究,发现共振波长与分析物折射率呈线性关系,且由于局域和传播表面等离子体的高效激发,反射光谱共振峰处的反射率几乎为零。此外,在最优的金纳米锥几何参数下,传播表面等离子体共振模式的半高全宽非常窄,灵敏度和品质因数分别达到770 nm/RIU和113 RIU^-1,具有良好的折射率传感性能。所设计的复合结构作为表面等离子体共振传感器有望广泛应用于生物检测领域。     

新工艺生长的InGaN量子点的结构与电学性质研究

利用金属有机化学气相沉积（MOCVD）技术，采用一种称为低温钝化的新生和方法成功地生长出多层InGaN/GaN量子点。这种方法是对GaN表面进行钝化并在低温下生长，从而增加表面吸附原子的迁移势垒。采用原子力显微镜清楚地观察到该方法生长的样品中岛状的量子点。从量子点样品的I-V特性曲线观察到了共振隧穿引起的负阻效应，其中的锯齿状峰形归因于零维量子点的共振隧穿。     

隧穿结对具有中间层的非晶硅/微晶硅叠层电池的影响

为了改善非晶硅/微晶硅叠层电池的载流子输运效果,将隧穿结引入到具有中间层结构的叠层电池中,研究了隧穿结的结构、掺杂浓度、厚度等条件对叠层电池性能的影响。实验结果表明,叠层电池中引入隧穿结构成"隧穿结-中间层"结构,可以进一步改善电池性能,经过结构和参数优化的隧穿结可以提高子电池的电流密度匹配度,提升叠层电池转换效率。加入"隧穿结-中间层"结构的叠层电池具有较高的转换效率和光照稳定性,并且得到了初始转换效率12.2%,光照衰退率9%的叠层电池。     

基于共振隧穿结构的压阻系数

以共振隧穿结构为压阻器件可以得到较高的灵敏度,但是当实验选择不同的工作偏压时,这种压阻效应表现得极其不同.由于高灵敏度是依靠较高的I-V曲线斜率获得的,因此最初人们希望选择具有较高峰谷比结构作为器件.但是有些区域的斜率过大,以至于压阻效应失去线性及稳定性而变得没有实用价值.另外,在某些工作区域由于共振隧穿结构本身具有的双稳态特性,而使其完全失去压阻特性.本文对这些问题进行了系统分析,并对一个具体的结构,分析其工作区域及特性,给出最高灵敏度可达700左右.     

多晶硅/氧化硅/多晶硅非平面结构中Fowler-Nordheim隧穿及氧化层退化研究(英文)

Fowler-Nordheim隧穿被广泛应用于EEPROM和闪存中的擦除操作。多晶硅到多晶硅的F-N隧穿具有较高的隧穿效率。本论文基于分栅闪存存储器的结构,对于多晶硅/隧穿氧化层/多晶硅非平面结构的F-N隧穿及其引起的氧化层退化进行了研究。相比于平面结构,非平面结构显示出更高的F-N隧穿效率,且隧穿效率还可通过降低氧化层厚度或者增加预热氧化处理的方法进一步提高。较低的F-N隧穿电流密度显示出较慢的隧穿氧化层退化速率。降低氧化层厚度或者增加热氧化处理也可减缓隧穿氧化层的退化。另外,论文还讨论了研究结果对于改善分栅闪存擦除特性以及耐久性的意义。     

Enigmas of optical and matter-wave soliton nonlinear tunneling

The method of mathematical analogies opens the possibility to study optical and matter-wave solitons in parallel and, due to the evident complexity of experiments with matter wave solitons, offers remarkable possibilities in studies of the BEC systems by performing experiments in the nonlinear optical systems and vice versa. We discuss previous misinterpretations of the binding soliton energy and investigate all possible scenarios of nonlinear soliton tunneling of Schrödinger solitons including soliton splitting on a potential barrier, leading to partial reflection and partial transmission, sub-barrier soliton tunneling and over-barrier soliton reflection. We reveal the most significant modifications of soliton tunneling scenarios due to increasing the binding energy, and show that the self-compressing soliton resembles more the classical particle case than a quantum mechanical behavior. The enhancement of the soliton binding energy is of decisive importance in the testing of a long-standing theoretical result which predicts that an optical soliton can tunnel between two regions of anomalous dispersion across a forbidden region of normal dispersion (enhanced soliton spectral tunneling effect).     

Optical tunneling effect calculation of a solid immersion lens for use in optical disk memory

A solid immersion lens (SIL) has the advantage of easily decreasing the spot size for high data density in optical recording. To accurately obtain the optical tunneling effect for a high-N.A. SIL, we calculated the optical tunneling beam characteristics, using electromagnetic theory. Tunneling beam spot-size dependence on polarization direction and energy-transfer efficiency are also clearly shown.     

Optical actuation of micromechanical tunneling structures with applications in spectrum analysis and optical computing

An efficient method for optically actuating a micromechanical cantilever is presented for the first time to our knowledge. Measurable responses can be obtained for moderate light sources if electron tunneling occurs between the cantilever tip and a metallic contact below it. The small deflection of the cantilever that is due to light pressure is sufficient then to produce large tunneling current variations. On the basis of this effect several applications such as a miniaturized spectrum analyzer and one-step optical computing units for addition, integration, or differentiation of one-dimensional or two-dimensional optical signals are presented.     

Photon tunneling in a uniaxial crystal film

A method for studying photon tunneling in uniaxial crystal films is presented. The complex refractive index and the complex angle of refraction of the evanescent wave in a crystal are calculated for the most general case. The reflectance and transmittance resulting from the tunneling effect in crystal films are discussed, and the relations among these coefficients and the optical parameters of crystal are found. These relations provide a theoretical basis for characterizing crystal films by means of photon tunneling.     

Imaging of resonant quenching of surface plasmons by quantum dots

In scanning tunneling microscopy (STM), confinement of surface plasmons to the optical cavity formed at the metallic tunneling gap stimulates the emission of light. We demonstrate that quantum dots (QDs) found in such a cavity give rise to discrete, observable transitions in the tunneling luminescence spectrum due to the resonant extinction of the plasmon. The observed resonances represent a fingerprint of the QD and occur at the optical band gap owing to the nearly simultaneous transfer of carriers from both sides of the tunneling gap to the QD. The resonant quenching of surface plasmons enables a new imaging technique, dubbed plasmon resonance imaging, with a spatial resolution potentially similar to that of STM and the energy resolution of optical spectroscopies. This detection and imaging strategy is not restricted to QDs, being of great interest to an entire spectrum of nanostructures, from molecular assemblies and biomolecules to carbon nanotubes.     

Adsorption on straight and bent optical fibers considered as a perturbation problem

The effect of a thin adsorbed layer of a foreign material on the modal propagation constant in an optical fiber is calculated by the use of a time-independent perturbation theory. The effect is measured on a straight fiber but is enhanced on a bent fiber because of tunneling, which is analogous to the Zener effect in quantum mechanics. Experimental results obtained with a fiber interferometer are presented.     

Resonant Tunneling Spectroscopy to Probe the Giant Stark Effect in Atomically Thin Materials

Each atomic layer in van der Waals heterostructures possesses a distinct electronic band structure that can be manipulated for unique device operations. In the precise device architecture, the subtle but critical band splits by the giant Stark effect between atomic layers, varied by the momentum of electrons and external electric fields in device operation, has not yet been demonstrated or applied to design original devices with the full potential of atomically thin materials. Here, resonant tunneling spectroscopy based on the negligible quantum capacitance of 2D semiconductors in resonant tunneling transistors is reported. The bandgaps and sub-band structures of various channel materials could be demonstrated by the new conceptual spectroscopy at the device scale without debatable quasiparticle effects. Moreover, the band splits by the giant Stark effect in the channel materials could be probed, overcoming the limitations of conventional optical, photoemission, and tunneling spectroscopy. The resonant tunneling spectroscopy reveals essential and practical information for novel device applications.     

Variable-temperature scanning tunneling microscopy and scanning tunneling spectroscopy study on copper phthalocyanine ultrathin films on a Au(111) surface

Variable-temperature high-resolution scanning tunneling microscopy (STM) images reveal that well-ordered copper phthalocyanine (CuPc) strips can be self-assembled by depositing CuPc molecules on a Au(111) surface. The self-assembled strips are supposed to result from the balance of the intermolecular interaction and the interaction between the molecules and substrate during annealing. The energy band (approximately 1.9-2.1 eV) of CuPc, measured by scanning tunneling spectroscopy (STS), is comparable to the optical band gap (approximately 1.7 eV). Spectroscopic measurements confirm that a dipole layer and/or an effect of image force exist at the CuPc/Au(111) interface.     

Various and Tunable Transport Properties of WSe2 Transistor Formed by Metal Contacts

The abundant electronic and optical properties of 2D materials that are just one‐atom thick pave the way for many novel electronic applications. One important application is to explore the band‐to‐band tunneling in the heterojunction built by different 2D materials. Here, a gate‐controlled WSe₂ transistor is constructed by using different work function metals to form the drain (Pt) and source (Cr) electrodes. The device can be gate‐modulated to exhibit three modes of operation, i.e., the tunneling mode with remarkable negative differential resistance, the transition mode with a second electron tunneling phenomenon for backward bias, and finally the conventional diode mode with rectifying characteristics. In contrast to the heterojunctions built by different 2D materials, these devices show significantly enhanced tunneling current by two orders of magnitude, which may largely benefit from the clean interfaces. These results pave the way toward design of novel electronic devices using the modulation of metal work functions.     

Voltage-controlled optical precursors in quantum dot molecules

Abstract

Optical precursors generated in a quantum-dot-molecule system by an incident square-modulated pulse are theoretically investigated. Voltage-controlled electron tunneling couples two quantum dots instead of a laser field, and a narrow transparency window appears with normal dispersion. The main pulse is delayed due to slow-light effect and the precursor pulses are obtained. We examine the linear susceptibility and find that its one part exhibits normal dispersion and the other one presents anomalous dispersion. Competition between the two parts leads to normal dispersion for the linear susceptibility, which contributes to the above results. Voltage-controlled precursors may be useful to design novel optical devices for generating precursors.