Electrochemical Micromachining as an Enabling Technology for Advanced Silicon Microstructuring

Based on previous theoretical and experimental results on the electrochemical etching of silicon in HF‐based aqueous electrolytes, it is shown for the first time that silicon microstructures of various shapes and silicon microsystems of high complexity can be effectively fabricated in any research lab with sub‐micrometer accuracy and high aspect ratio values (about 100). This is well beyond any up‐to‐date wet or dry microstructuring approach and is achieved using a wet etching, low‐cost technology: silicon electrochemical micromachining (ECM). Dynamic control of the etching anisotropy (from 1 to 0) as the electrochemical etching progresses allows the silicon dissolution to be switched in real‐time from the anisotropic to the isotropic regime and enables advanced silicon microstructuring to be achieved through the use of high‐aspect‐ratio functional and sacrificial structures, the former being functional to the microsystem operation and the latter being sacrificed for accurate microsystem fabrication. World‐wide dissemination of the ECM technology for silicon microstructuring is envisaged in the near future, due to its low cost and high flexibility, with high‐potential impact on, though not limited to, the broad field of microelectronics and microfabrication.     

硅光子学

硅光子学有六个主要研究领域,包括产生光、在硅中选择地引导和传输光、编码光、探测光、包装器件和智能地控制这一切光子功能。综述了以上各领域的研究进展。     

Silicon Photonics

After dominating the electronics industry for decades, silicon is on the verge of becoming the material of choice for the photonics industry: the traditional stronghold of III-V semiconductors. Stimulated by a series of recent breakthroughs and propelled by increasing investments by governments and the private sector, silicon photonics is now the most active discipline within the field of integrated optics. This paper provides an overview of the state of the art in silicon photonics and outlines challenges that must be overcome before large-scale commercialization can occur. In particular, for realization of integration with CMOS very large scale integration (VLSI), silicon photonics must be compatible with the economics of silicon manufacturing and must operate within thermal constraints of VLSI chips. The impact of silicon photonics will reach beyond optical communication-its traditionally anticipated application. Silicon has excellent linear and nonlinear optical properties in the midwave infrared (IR) spectrum. These properties, along with silicon's excellent thermal conductivity and optical damage threshold, open up the possibility for a new class of mid-IR photonic devices     

Nanostructured Bulk Silicon as an Effective Thermoelectric Material

Thermoelectric power sources have consistently demonstrated their extraordinary reliability and longevity for deep space missions and small unattended terrestrial systems. However, more efficient bulk materials and practical devices are required to improve existing technology and expand into large‐scale waste heat recovery applications. Research has long focused on complex compounds that best combine the electrical properties of degenerate semiconductors with the low thermal conductivity of glassy materials. Recently it has been found that nanostructuring is an effective method to decouple electrical and thermal transport parameters. Dramatic reductions in the lattice thermal conductivity are achieved by nanostructuring bulk silicon with limited degradation in its electron mobility, leading to an unprecedented increase by a factor of 3.5 in its performance over that of the parent single‐crystal material. This makes nanostructured bulk (nano‐bulk) Si an effective high temperature thermoelectric material that performs at about 70% the level of state‐of‐the‐art Si_0.8Ge_0.2 but without the need for expensive and rare Ge.     

面向中红外应用的硅基光电子学最近研究进展

随着信息传递、处理以及存储能力要求的不断提升,传统的近红外通信波段已呈“容量紧缩”之势。而工艺与CMOS兼容、结构简单、成本低廉的硅基光电子技术在中红外信号传输和处理方面已经显示出独特优势,有望在中红外波段实现大规模集成,在非线性光学等领域实现新的飞跃。首先介绍了硅基光电子技术在中红外应用中的优势以及目前研究过程中所遇到的困难和挑战;其次结合材料属性和结构特性对一些基本元件（如波导、分束/合束器、二极管）等在中红外领域的最新研究成果进行了介绍;最后对近5年来在中红外波段所实现传感应用的非线性光学硅基器件（基于FWM的非线性光学器件、频率梳）和面向中红外通信应用的激光器、调制器、光电探测器进行了成果介绍,并对研究进展进行了总结。     

Fabrication of Silicon Nanostructures for Application in Photonics

Semiconductors - Silicon is the primary material of modern electronics. It also possesses bright potentials for applications in nanophotonics. At the same time optical properties of bulk silicon do...     

硅光子中波分复用技术研究

介绍了硅光子互连中4种波分复用器及相关单片集成发射接收芯片,其中硅纳米线阵列波导光栅及刻蚀衍射光栅波分复用器单个芯片就可以成倍扩展通道数,非常适合大通道数密集波分复用,马赫-曾德尔结构及微环谐振型波分复用器芯片通道数增大时需要多个单元级联,波长准确性及间隔不易控制,比较适合通道数少的芯片应用。同时,给出了自主设计和制备的硅纳米线阵列波导光栅和刻蚀衍射光栅,通过采用阵列波导展宽方法,有效抑制了阵列波导的串扰,实现串扰小于-15 d B;通过在刻蚀衍射光栅反射面引入二维光子晶体反射镜,降低了刻蚀衍射光栅的反射损耗,损耗比普通刻蚀衍射光栅减小了3 d B。     

A special issue on Silicon Photonics

The tremendous demand on low cost optoelectronic systems that may be used for high-density data communications,real time sensing/detection and high-speed control/actuation has heated up the research and development in silicon photonics,which studies the principles and technologies of merging electronics and photonics into the silicon platform.To make a silicon photonic system reality,the compatibility in device size and integration processing between the photonics and electronics is essential.Over the past years,unprecedented advancement on individual silicon photonic devices,such as waveguide,beam splitter,light source,modulator,and detector,have been reported,yet the progress in size and processing issues are still under development.     

Silicon Photonics: CMOS Going Optical

For almost 50 years, silicon microelectronics has been the engine of the modern information revolution. Complex microprocessors, dense memory circuits, and other digital and analog electronics produced by the $100 billion silicon industry mainly serve a single goal - to process more and more data faster and faster using smaller and smaller components. In this everlasting quest, the silicon industry has successfully overcome many critical issues that were initially considered to be impassible road blocks. Recent progress in silicon compatible photonics is driving high density integration of photonic and electronic components manufactured by CMOS-based technology on the same platform.This Special Issue presents a set of review papers addressing major challenges and summarizing recent progress in the several subfields of Si-based photonics.     

Fast Reversible Phase Change Silicon for Visible Active Photonics

Both amorphous and crystalline silicon are ubiquitous materials for electronics, photonics, and microelectromechanical systems. On‐demand control of Si crystallinity is crucial for device manufacturing and to overcome the limitations of current phase‐change materials (PCM) in active photonics. Fast reversible phase transformation in silicon, however, has never been accomplished due to the notorious challenge of amorphization. It is demonstrated that nanostructured Si can function as a PCM, since it can be reversibly crystallized and amorphized under nanosecond laser irradiation with different pulse energies. Reflection probing on a single nanodisk's phase transformations confirms the distinct mechanisms for crystallization and amorphization. The experimental results show that the relaxation time of undercooled silicon at 950 K is 10 ns. The phase change provides a 20% nonvolatile reflectivity modulation within 100 ns and can be repeated over 400 times. It is shown that such transformations are free of deformation upon solidification. Based on the switchable photonic properties in the visible spectrum, proof‐of‐concept experiments of dielectric color displays and dynamic wavefront control are shown. Therefore, nanostructured silicon is proposed as a chemically stable, deformation free, and complementary metal–oxide‐semiconductor compatible (CMOS) PCM for active photonics at visible wavelengths.     

光子学在材料加工中的应用

光子学应用于材料加工已经三十多年,但是就其应用的深度和广度而言,相对于传统技术仍是一门新兴技术。评述了最近几年中光子学在材料加工的常规加工、激光成型、溶胶一凝胶技术、微加工和光学平版印刷术应用中的最新进展。     

光子学在材料工业中的应用

评述光子学在材料工业的光学硅、纳米材料、光子晶体和集成光路中的应用。     

Strained Interface Defects in Silicon Nanocrystals

The surface of silicon nanocrystals embedded in an oxide matrix can contain numerous interface defects. These defects strongly affect the nanocrystals’ photoluminescence efficiency and optical absorption. Dangling‐bond defects are nearly eliminated by H₂ passivation, thus decreasing absorption below the quantum‐confined bandgap and enhancing PL efficiency by an order of magnitude. However, there remain numerous other defects seen in absorption by photothermal deflection spectroscopy; these defects cause non‐radiative recombination that limits the PL efficiency to <15%. Using atomistic pseudopotential simulations, we attribute these defects to two specific types of distorted bonds: Si‐Si and bridging Si‐O‐Si bonds between two Si atoms at the nanocrystal surface.     

Wide Bandgap Phase Change Material Tuned Visible Photonics

Light strongly interacts with structures that are of a similar scale to its wavelength, typically nanoscale features for light in the visible spectrum. However, the optical response of these nanostructures is usually fixed during the fabrication. Phase change materials offer a way to tune the properties of these structures in nanoseconds. Until now, phase change active photonics has used materials that strongly absorb visible light, which limits their application in the visible spectrum. In contrast, Sb₂S₃ is an underexplored phase change material with a bandgap that can be tuned in the visible spectrum from 2.0 to 1.7 eV. This tuneable bandgap is deliberately coupled to an optical resonator such that it responds dramatically in the visible spectrum to Sb₂S₃ reversible structural phase transitions. It is shown that this optical response can be triggered both optically and electrically. High‐speed reprogrammable Sb₂S₃ based photonic devices, such as those reported here, are likely to have wide applications in future intelligent photonic systems, holographic displays, and microspectrometers.     

360-nm Photoluminescence from Silicon Oxide Films Embedded with Silicon Nanocrystals

Si-rich silicon oxide films were deposited by RF magnetron sputtering onto composite Si/SiO2 targets. After annealed at different temperature, the silicon oxide films embedded with silicon nanocrystals were obtained. The photoluminescenee（PL） from the silicon oxide films embedded with silicon nanocrystals was observed at room temperature. The strong peak is at 360 nm, its position is independent of the annealing temperature. The origin of the 360-nm PL in the silicon oxide films embedded with silicon nanoerystals was discussed.     

PIN二极管用硅外延材料

介绍了研制适用于大功率PIN二极管的硅外延材料的工艺过程,采用CVD化学气相外延生长技术,对硅源流量与掺杂剂浓度的精确控制,实现了快速外延生长和高浓度掺杂.通过大量实验,利用4.0 μm/min的生长速率得到了掺杂浓度为2.0×1019 cm-3的超高浓度的掺杂外延层,其外延层表面光亮,满足了PIN二极管的使用要求.     

Oxidized Porous Silicon Nanostructures Enabling Electrokinetic Transport for Enhanced DNA Detection

Nanostructured porous silicon (PSi) is a promising material for the label‐free detection of biomolecules, but it currently suffers from limited applicability due to poor sensitivity, typically in micromolar range. This work presents the design, operation concept, and characterization of a novel microfluidic device and assay that integrates an oxidized PSi optical biosensor with electrokinetic focusing for a highly sensitive label‐free detection of nucleic acids. Under proper oxidation conditions, the delicate nanostructure of PSi can be preserved, while providing sufficient dielectric insulation for application of high voltages. This enables the use of signal enhancement techniques, which are based on electric fields. Here, the DNA target molecules are focused using an electric field within a finite and confined zone, and this highly concentrated analyte is delivered to an on‐chip PSi Fabry–Pérot optical transducer, prefunctionalized with capture probes. Using reflective interferometric Fourier transform spectroscopy real‐time monitoring, a 1000‐fold improvement in limit of detection is demonstrated compared to a standard assay, using the same biosensor. Thus, a measured limit of detection of 1 × 10^?9 m is achieved without compromising specificity. The concepts presented herein can be readily applied to other ionic targets, paving way for the development of other highly sensitive chemical and biochemical assays.