In this paper we evaluate the need for a reinforcement learning algorithm to optimize the gait of OctoRoACH, a hand-sized eight-legged robot. We then perform an evaluation of a likelihood-ratio gradient policy and compare it against our hand-tuned results. Finally, we suggest a different approach to reduce the policy search space that can make the problem more manageable.

关键词：腿式机器人；步行机；强化学习算法；搜索范围

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We have investigated a wet chemical process for nanoscale texturing of sulfur-doped silicon (Si) surfaces, which results in substantial suppression of the reflectivity in a broad spectral range, leading to black Si surfaces. The blackened surface was characterized optically and with Veeco micro- profiler. We fabricated metal semiconductor metal (MSM) test devices using the aforementioned black silicon and electrically characterized them for current- voltage (I-V), optical response, zero biased quantum efficiency (QE), and optical responsivity. We observe increased optical response and responsivity for the blackened silicon. One key observation we have made is the extension of the detectivity up to 1.2 m, which is beyond 1.1 m for a typical silicon detector. This observation was made under zero bias to the detector. We conclude that anneling and metal enhanced chemical etching (MECE) treatment prior to fabrication of the devices have enhanced the detectivity of the devices beyond the typical bandgap of 1.1 m of silicon.

关键词：电子信息；半导体；光电探测器；黑硅

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This research investigates the degree to which optical injection improves the communication capability of directly modulated semiconductor lasers and evaluates the suitability of optical injection for telecommunications applications. An end-to-end digital communication system which directly modulates the bias-current of a Fabry–Pérot laser diode is used to investigate the bit-rate-distance improvements achieved using optically injected Fabry–Pérot laser diodes. The injection strength and detuning frequency of the injection signal was varied to determine their impact on the optical communication link’s characteristics. This research measured a 25 fold increase in the bit-rate-distance product using optical injection locking as compared to the injected laser’s free-running capability.A 57 fold increase was measured in the bit-rate-distance product when signal power is considered in a power-penalty measurement. This increased performance is attributed to the injected signals tolerance to dispersion given its reduced linewidth and chirp. This work also investigates the suitability of optical injection for radio over fiber applications using the period-one dynamic of optical injection. The all-optically generated, widely tunable microwave subcarrier frequency, well above the 3-dB cutoff frequency of the laser’s packaging electronics, is modulated with the same baseband electronics. This optically carried, ultra-wide spread spectrum signal is transported 50km through standard single-mode fiber. After detection with a high-speed photodetector followed by removal of the baseband modulation component, the resultant signal was found to be suitable for broadcasting with an antenna or added to a frequency division multiplexed channel.

关键词：电子信息；半导体；激光器；通信

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We perform characterization of the pulse shape and noise properties of quantum dot passively mode-locked lasers (PMLLs). We propose a novel method to determine the RF linewidth and timing jitter, applicable to high repetition rate PMLLs, through the dependence of modal linewidth on the mode number. Complex electric field measurements show asymmetric pulses with parabolic phase close to threshold, with the appearance of waveform instabilities at higher currents. We demonstrate that the waveform instabilities can be overcome through optical injection-locking to the continues wave (CW) master laser, leading to time-bandwidth product (TBP) improvement, spectral narrowing, and spectral tunability. We discuss the benefits of single- and dual-tone master sources and demonstrate that dual-tone optical injection can additionally improve the noise properties of the slave laser with RF linewidth reduction below instrument limits (1 kHz) and integrated timing jitter values below 300 fs. Dual-tone injection allowed slave laser repetition rate control over a 25 MHz range with reduction of all modal optical linewidths to the master source linewidth, demonstrating phase-locking of all slave modes and coherence improvement.

关键词：电子信息；半导体；激光器；光注入

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We synthesized a variety of wide bandgap nanowires using GaN and ZnO and made functional devices from them for sensing, electronics and photonics.These included a very sensitive glucose sensor and hydrogen sensors with ppm sensitivity at room temperature.

关键词：电子信息；半导体；纳米线；宽能隙

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The goal of this project was to develop spin injection and detection techniques to enable spin transport to enhance the speed and design of CMOS VLSI circuits. Progress toward this goal over the duration of the award specifically impacts: (1) Understanding extrinsic origins of spin depolarization at interfaces and with localized impurity states; and (2) Quantifying the extent to which physical processes and boundary conditions affect spin dephasing in vertical-transport devices. The results of these efforts were the following. We analytically derived the impulse response (Green's function) of a current-sensing spin detector. We showed that spin diffusion and concomitant spin dephasing could be greatly enhanced with respect to charge diffusion. We showed that strong spin relaxation at oxide interfaces yielded a spin lifetime of ~lns, orders of magnitude lower than lifetimes in bulk Si. Experimental evidence of spin precession during travel through the doped Si channels indicated delays associated with electron capture or reemission in shallow impurity traps. These results helped to significantly improve the understanding of spin transport in silicon.

关键词：电子信息；半导体；自旋电子；技术

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CdSe quantum dot (QD)-sensitized solar cells (QDSCs) were synthesized by adsorbing CdSe QDs onto TiO_2 nanostructured electrodes with different morphologies, i.e., nanoparticles, nanotubes, and inverse opals. The optical absorption, photoelectrochemical, and photovoltaic properties of the QDSCs were characterized and the dependences of these properties on the QD deposition time and the TiO_2 nanostructure are discussed. To improve the photovoltaic performance of the CdSe QDSCs, surface passivation with a ZnS coating was introduced and CU_2S counter electrodes were applied. All aspects of the photovoltaic performance, including the short-circuit photocurrent density, open-circuit voltage, fill factor, and efficiency, were found to be significantly improved by the surface modification with ZnS. For the counter electrode, the Cu_2S electrode was demonstrated to be more efficient than platinum against the polysulfide electrolytes usually used as redox couples in CdSe QDSCs. Moreover, CdS QD adsorption on the TiO_2 electrodes prior to CdSe QD adsorption also resulted in better solar cell performance. In addition, we found that the morphology of the TiO_2 electrodes had a great influence on the photovoltaic properties of the QDSCs. Finally, a power conversion efficiency as high as 4.9was achieved for a combined CdS/CdSe QDSC under solar illumination of 100 mW/cm~2.

关键词：电子信息；半导体；太阳能；光阳极

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The spectral and spatial radiative properties of coherent thermal emission in the mid-infrared and far-infrared through the use of micro- structured and nano-structured metal-semiconductor materials were demonstrated experimentally. Using an implementation of the Rigorous Coupled Wave Analysis (RCWA) numerical technique and Computer Simulation Technology (CST) electromagnetic modeling software, two structures were designed to selectively emit at mid- and far-IR wavelengths: a one-dimensional (1-D) truncated multilayer resonator and a three-dimensional (3-D) hybrid photonic crystal- multilayer (PC-multilayer) structure. A High Impulse Power Magnetron Sputtering (HIPIMS) deposition technique was used to fabricate two silver-germanium-silver (Ag-Ge-Ag) resonating structures with layer thicknesses of 6-240-160 nm for one sample and 6-700-200 nm for the other. The design thicknesses of each sample were verified through both reflectance and standard spectral ellipsometric measurements at wavelengths from 2-15 micrometers. Reflectance measurements demonstrated spectrally selective absorption at the designed IR wavelengths whose general behavior was largely unaffected by a wide range of incident angles. Ellipsometric measurements showed significant disagreement between HIPIMS-deposited material properties and bulk values found in literature. Radiance measurements taken at various high temperatures showed that spectral emittance was directly derived and compared to the emittance inferred from reflectance measurements. Inferring emittance can help to approximate the expected emission from a structure, but it is not an exact method of determining the actual emittance of a thermal source. Using CST, the PC- multilayer structure was modeled to examine its spatial coherence. Initial fabrication results of the PC-multilayer involving both HIPIMS deposition of a Ge-Ag-Ge-Ag (4-12-270-200 nm) multilayer and focused ion beam milling of a square hole array also are presented.

关键词：电子信息；半导体；纳米结构；热辐射

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The unique versatility of micro-Raman spectroscopy (μ-RS) in semiconductor physics remains in Raman imaging. Numerous applications cover the whole development of modern electronic and optoelectronic devices: from semiconductor growth to advanced device inspection tools. In this chapter, a wide variety of semiconductors (SiC, graphene, GaN, GaAs, SiGe, strained Si, sSOI, SGOI) and devices (FETs, lasers, MEMS) are addressed. First, it will be shown how Raman mapping enables to check the crystalline quality, the composition, the doping, and the uniformity of as-grown semiconductors. Then, we will focus on the most popular application in microelectronics: strain measurements either at the device or at the full wafer scale. Finally, we will show how μRS imaging can be used for final device inspection through the temperature mapping of operating devices (FETs, lasers, actuators). Since the first report by Raman in 1928 [1, 2], Raman spectroscopy has become increasingly popular in materials science and, especially, in semiconductor physics and microelectronics. Basically Raman scattering probes the inelastic scattering of a monochromatic light (incoming-photons) by the atomic vibrations in a medium (solid, liquid, or gas). In crystalline solids, the atomic vibrations are quantized (phonons) and they are very sensitive to internal and external perturbations, such as doping and stress. The frequency of the scattered light (out-coming photons) is then a local probe of the perturbation experienced (or not) by the medium. Today, the large number of results collected on semiconductors, combined with a good theoretical understanding of the scattering mechanisms, allows to predict reli- ably the effect of an external perturbation on the electronic and vibrational properties of the investigated medium (either ordered or disordered). Raman spectroscopy can then be used to identify the constituting species, study the compositional uniformity, crystallinity, doping level, and to probe locally the temperature and stress. At the industrial level, in modern clean room facilities micro-Raman spectroscopy (ixRS) has become (like many other optical techniques) a very attractive characterization tool. This is because of its contactless and nondestructive nature. Thanks to recent turnkey Raman systems, one can perform repetitively large area mapping with spatial resolution down to 300 nm. The use of several laser wavelengths enables then to probe the in-depth profile of a given semiconductor or device. All these features confirm the unique versatility and potentialities of |xRS imaging in microelectronics. In this chapter, we illustrate how this unique characterization tool covers the whole process flow of fabrication of modern electronic and optoelectronic devices. The first section will give some background considerations on Raman imaging in semiconductor physics. The second section will be devoted to the study of advanced wafers manufacturing and epitaxial layers development, such as graphene, Si _(1-x)Ge_x alloys, and strained Si wafers. The third section will focus on the most popular application of Raman imaging in microelectronics: stress monitoring. Finally the fourth one will address how Raman imaging can contribute to the final device inspection.

关键词：电子信息；半导体；拉曼成像；微电子材料

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The chapter starts with a comparison of methods to generate digital optical signals: direct laser modulation, electroabsorption and Mach-Zehnder interferometer modulators. Next follows an in-depth treatment of physical effects which are utilized for semiconductor-based modulators (Plasma, Franz-Keldysh, quantum-confined Stark, and electro-optic (Pockels) effect), and their exploitation for InP-and GaAs-based modulators with specific emphasis on aspects of high-speed modulator design. Modulator characteristics including eye diagrams obtained for different implementations and various operation conditions illustrate the current state-of-the-art, and the chapter concludes with a section on modulators for higher order modulation formats.

关键词：电子信息；半导体；调节器

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