Tailored Macroporous SiCN and SiC Structures for High‐Temperature Fuel Reforming

The catalytic reforming of hydrocarbons in a microreformer is an attractive approach to supply hydrogen to fuel cells while avoiding storage and safety issues. High‐surface‐area catalyst supports must be stable above 800 °C to avoid catalyst coking; however, many porous materials lose their high surface areas below 800 °C. This paper describes an approach to fabricate macroporous silicon carbonitride (SiCN) and silicon carbide (SiC) monoliths with geometric surface areas of 10⁵ to 10⁸ m² per m³ that are stable up to 1200 °C. These structures are fabricated by capillary filling of packed beds of polystyrene or silica spheres with low‐viscosity preceramic polymers. Subsequent curing, pyrolysis, and removal of the spheres yielded SiCN and SiC inverted beaded monoliths with a chemical composition and pore morphology that are stable in air at 1200 °C. Thus, these structures are promising as catalyst supports for high‐temperature fuel reforming.     

Template‐Synthesized Protein Macroporous Biofilms: Conformational Related Direct Electron Transfer

We report on the synthesis of three‐dimensionally ordered structure (3D) of macroporous cytochrome c (cyt‐c) biofilms by using the inverted colloidal polystyrene crystal template technique and Triton X‐100 as entrapping matrix. Electrochemical impedance spectroscopic (EIS) measurements reveal that the immobilized cyt‐c molecules exhibit fast interfacial electron‐communication rate. We found that the orientation of the cyt‐c molecules entrapped in the 3D macroporous structure was determined by the interfacial electric field. Higher interfacial electric field limits the reorientational flexibility of the entrapped cyt‐c molecules, resulting in lower intermolecular electron‐communication rate constant (k°). Therefore, the highest intermolecular electron‐communication rate constant can only be obtained at potentials approaching to the potential of zero charge of the gold electrode, since k° is mainly determined by the molecular orientation in the biofilm. In addition, the prepared biofilms with enhanced functional density could find potential application in the bioelectronic sensing system.     

Synthesis and Patterning of Prussian Blue Nanostructures on Silicon Wafer via Galvanic Displacement Reaction

Nanoscale materials directly interfacing semiconductors is a new area of nanoscience and nanotechnology. Tremendous attention has been paid to inorganic nano size crystals in recent years because of their significant properties. Prussian blue (PB) and its analogues could play important roles in the field of molecule‐based magnets, electrochromic materials, ion selectivity electrodes and biosensors. In this study, we report on fabricating Prussian blue patterns on silicon surface by combining the photolithographic techniques and galvanic displacement reaction, and the resulting patterns were characterized by scanning electron microscopy (SEM) and scanning electrochemical microscopy (SECM) on the basis of detection of catalytic current for the oxidation of H₂O₂.     

Frontal Polymerization Synthesis of Monolithic Macroporous Polymers

A frontal polymerization method is used to produce highly porous polymer monoliths. The method is an approach to polymer synthesis that exploits the heat produced by the reaction itself. This heat triggers polymerization of neighboring monomer molecules, leading to a self‐sustaining hot front, which propagates along the reacting vessel. Dissolved or microencapsulated foaming agents are decomposed only at the fronts, synchronizing the polymerization and the foaming. The ultimate pore structures appear to depend on the polymerization‐front velocity and temperature. The resultant materials are porous, exhibiting tunable pore volume and a multimodal pore size distribution. No organic solvents or high‐pressure equipment are used in the process, and no solvent residues are left in the resulting materials. Specifically, this route allows for the synthesis of large‐scale samples with the additional advantages of high velocity, low energy cost, and the avoidance of multiple process steps. Substitution of hydrophilic acrylamide, N‐isopropylacrylamide, with hydrophobic styrene and methyl methacrylate also leads to porous monolithic materials, suggesting that frontal polymerization represents a powerful and facile method for an exothermic polymerization reaction and the creation of porous polymers.     

Silicon Nanowire Sensors for Bioanalytical Applications: Glucose and Hydrogen Peroxide Detection

Silicon nanowire films have been modified with boron and used as sensors to measure glucose in aqueous solution. These sensors have a wide linear range (0–10 mM glucose), high sensitivity (172 nA mmol^–1), good reproducibility, and long‐term stability. Silicon nanowire films have also been modified with magnesium and shown to perform as sensors for detecting hydrogen peroxide in aqueous solution.     

Peptides for the Biofunctionalization of Silicon for Use in Optical Sensing with Porous Silicon Microcavities

Addressing the surface chemistry of silicon is of fundamental scientific and technical significance due to the wide use of this material in electronics and optics. A novel method of functionalizing silicon (Si) via short peptides with binding specificity for Si is presented. The peptide presenting the highest affinity for Si is identified via phage display technology, and the 12‐mer LLADTTHHRPWT and SPGLSLVSHMQT peptides were found to be specific for the n⁺‐Si and p⁺‐Si surfaces, respectively. In our sensing application, the obtained peptides are used as functionalizing linkers to allow porous silicon microcavities to bind biotin and then capture streptavidin. Molecular detection is monitored via reflectometric interference spectra as shifts in the resonance peaks of the cavity structure. An improved streptavidin sensing (21 times lower detection limit) with peptide‐functionalized porous silicon microcavities is demonstrated, compared to sensing performed with devices functionalized with the commonly used silanization method, suggesting that the modification of Si via Si‐specific peptides provides better interface layers for molecular detection. High‐resolution atomic force microscopy images corroborate this result and reveal the formation of ordered nanometer‐sized molecular layers when peptide‐route functionalization is performed.     

Functionally Modified Macroporous Membrane Prepared by using Pulsed Laser Deposition

Pulsed laser deposition (PLD) is used to deposit pure metals (Pt and Au) and a mixture of metals (Pt–Ru) at the surface of a porous aluminum anodic oxide (AAO) substrate. In the case of Pt, thick films (> 300 nm) with pore diameters larger than 150 nm (macroporous), replicating the pore structure of the underlying AAO substrate, are obtained when PLD is performed at high (> 50 eV at^–1) kinetic energy (E_k) conditions. At lower E_k conditions, the characteristic structure of the AAO membrane is not discernable in the deposited film. In that case, the substrate is entirely covered by a film, the structure of which is not different from that of a Pt film deposited on a flat Si substrate under the same conditions. AAO membranes modified by macroporous Au and Pt–Ru alloy films are also prepared, demonstrating that the concept can be applied to a wide range of materials. The mechanisms responsible for the replication of the substrate pore structure in the metallic layer are discussed. These functionally modified macroporous membranes are electroactive and this aspect has been emphasized by studying the electrocatalytic properties of Pt and Pt–Ru modified macroporous membranes for CO oxidation.     

Macroporous Zeolitic Membrane Bioreactors

A simple and effective method is described for the fabrication of robust zeolitic membranes with three‐dimensional (3D) interconnected macroporous structures. The membranes were prepared by electrostatically seeding mesoporous silica sphere (MSS) self‐assembled films with silicalite‐1 nanoparticles, followed by hydrothermal treatment. The membrane thickness, which is determined by the MSS film thickness, can be easily adjusted from tens to hundreds of micrometers by varying the concentration of the MSS dispersion and the solution volume. Biomacromolecule‐functionalized macroporous zeolitic membrane bioreactors were subsequently prepared via the layer‐by‐layer (LbL) electrostatic assembly of polyelectrolytes and enzyme (catalase) on the 3D macroporous membranes. The enzyme‐modified membranes with interconnected macroporous structures display enzyme loading amounts and activities that are one order of magnitude higher than corresponding 3D zeolite films with closed macropores, and approximately three orders of magnitude higher than their non‐porous planar film counterparts assembled on silica substrates. The enzyme loadings and activities were found to be approximately linearly dependent on the thicknesses of the membranes. Furthermore, the immobilized enzyme exhibits enhanced reaction stability in comparison with enzyme in bulk solution. These membranes are potentially useful for separations as they could be used to simultaneously perform reaction and separation steps.     

硅芯硅棒自动清洗设备的研制

通过分析硅芯硅棒清洗方式的现状,提出其自动清洗设备研制的必要,介绍了全自动硅芯硅棒清洗机的技术参数和工艺流程,详细分析了设备的结构设计,包括工艺清洗系统、传动系统、电气控制系统、排风系统、管路系统和设备主体等。     

Integration of a Chemical‐Responsive Hydrogel into a Porous Silicon Photonic Sensor for Visual Colorimetric Readout

The incorporation of a chemo‐responsive hydrogel into a 1D photonic porous silicon (PSi) transducer is demonstrated. A versatile hydrogel backbone is designed via the synthesis of an amine‐functionalized polyacrylamide copolymer where further amine‐specific biochemical reactions can enable control of cross‐links between copolymer chains based on complementary target–probe systems. As an initial demonstration, the incorporation of disulfide chemistry to control cross‐linking of this hydrogel system within a PSi Bragg mirror sensor is reported. Direct optical monitoring of a characteristic peak in the white light reflectivity spectrum of the incorporated PSi Bragg mirror facilitates real‐time detection of the hydrogel dissolution in response to the target analyte (reducing agent) over a timescale of minutes. The hybrid sensor response characteristics are shown to systematically depend on hydrogel cross‐linking density and applied target analyte concentration. Additionally, effects due to responsive hydrogel confinement in a porous template are shown to depend on pore size and architecture of the PSi transducer substrate. Sufficient copolymer and water is removed from the PSi transducer upon dissolution and drying of the hydrogel to induce color changes that can be detected by the unaided eye. This highlights the potential for future development for point‐of‐care diagnostic biosensing.     

Confinement of Thermoresponsive Hydrogels in Nanostructured Porous Silicon Dioxide Templates

A thermoresponsive hydrogel, poly(N‐isopropylacrylamide) (poly(NIPAM)), is synthesized in situ within an oxidized porous Si template, and the nanocomposite material is characterized. Infiltration of the hydrogel into the interconnecting nanoscale pores of the porous SiO₂ host is confirmed by scanning electron microscopy. The optical reflectivity spectrum of the nanocomposite hybrid displays Fabry–Pérot fringes characteristic of thin film interference, enabling direct, real‐time observation of the volume phase transition of the confined poly(NIPAM) hydrogel. Reversible optical reflectivity changes are observed to correlate with the temperature‐dependent volume phase transition of the hydrogel, providing a new means of studying nanoscale confinement of responsive hydrogels. The confined hydrogel displays a swelling and shrinking response to changes in temperature that is significantly faster than that of the bulk hydrogel. The porosity and pore size of the SiO₂ template, which are precisely controlled by the electrochemical synthesis parameters, strongly influence the extent and rate of changes in the reflectivity spectrum of the nanocomposite. The observed optical response is ascribed to changes in both the mechanical and the dielectric properties of the nanocomposite.     

二十一世纪的纳米硅电子技术

装置技术为适应电子市场的需求而发展 ,纳米硅电子技术伴随着电子信息产业的发展应运而生 ;本文综述了纳米硅电子技术的产生、现状及未来的发展趋势 ;并分析了纳米硅电子技术与信息产业发展的关系     

多孔硅秃腔微结构的AFM和SEM研究

多孔硅微腔是采用交替变化脉冲腐蚀电流密度的方法制成的多孔度周期性变化的多孔硅结构。用原子力显微镜（AFM）和扫描电子显微镜（SEM）对多孔硅微腔的侧向解理的截面进行了观测，得到了不同多孔层及其界面处的图像。微腔截面的扫描电镜图像清楚地显示出第Ⅱ型多孔硅微腔的“三明治”结构，即中心发光层被夹在两个Bragg反射镜之间，这些结果表明结合分子束外延技术和电化学腐蚀方法可以很容易得到多孔硅微腔。     

多孔硅（PS）制备新方法

介绍了两种制备多孔硅的方法：电火花刻蚀法和激光辐射腐蚀法。讨论了这两种新方法制备的多孔硅样品的结构和发光特性，同时，与电化学法制备的多孔硅的结构和发光特性进行了比较。最后指出这两种新方法对于多孔硅形成机理和发光机制研究是有所帮助的。     

深硅槽开挖工艺

本文介绍了硅槽应用,即硅槽隔离和硅槽电容,对器件性能的改善。并介绍了硅槽隔离和硅槽电容的形成步骤及硅槽刻蚀剖面的形貌控制,CBrF_3刻蚀硅槽侧壁保护层的形成等等。     

硅的等离子体形成及相变微微秒时间分辨的探测

本文利用微微秒时间分辨的反射率与透射率的变化研究0.53μm约30ps脉冲激光激发的硅的电子-空穴等离子体形成及相变中的动态性质.实验结果证实了光能可以在小于30ps的时间内转移给晶格,晶格加热、相变可以在激光作用期间完成.实验指出,Auger 复合可以限制等离子体浓度的增加.从实验结果中还推导了高激光下等离子体的一些参量.     

Growth and Structural Characterization of Spherical Silicon Crystals Grown from Polysilicon

The growth process for spherical silicon crystals using melting and recrystallization of polysilicon powder and polysilicon granules is investigated and the structural properties of the fabricated silicon spheres are characterized. The recrystallization conditions that influence the crystallinity of the spheres are studied. It is shown by means of defect delineation that crystalline structures are obtained when the melt is solidified at temperatures above 1400°C. The results of electron backscattering confirm the formation of single-grain structures. When solidification takes place at temperatures below 1400°C, double- and multiple-grain structures start to form. The concentration of impurities during the recrystallization of the spheres, monitored by secondary-ion mass spectroscopy, show that the rate of impurity removal from the crystalline phase is much lower than predicted by segregation at the melt–solid interface, which is attributed to the nonequilibrium conditions in the solidification process.     

硅/硅直接键合的界面杂质

用SIMS和扩展电阻测试研究了常规p~+/n和n~+/n硅/硅键合界面的杂质O,H,C,N,Fe,Ni以及掺杂原子B,P的行为。经1 100℃ 1小时键合后,界面的H消失;O,C,N稳定;重金属杂质Fe,Ni仍在界面附近;掺杂原子B,P的扩散小于2μm。     

Silicon ribbons made by roller quenching methods

Polycrystalline silicon ribbons were prepared by Roller Quenching Methods. Ribbons were obtained flexible and of virtually continuous length, 20μ m to 200μ m in thickness, and 1 mm to 50 mm in width. Microscopic observations of etched ribbon surfaces showed that the average grain sizes were 20μ m to 30μ m. Cross-sectional views showed the ribbons to have a columnar grain structure. Unwanted impurities were undetectable by Auger analysis, except very thin oxygenated layer was present on the surface of the ribbons. By means of DC conductivity and Hall measurements of intentionally doped silicon ribbons, it was found that the active carrier concentration of the ribbons was nearly the same as the doped carrier concentration, from 10¹⁴/cm³ to 10²⁰/cm³ , the resistivity of the ribbons were about one order of magnitude higher than that of silicon single crystals, and the Hall mobility parallel to the ribbon axis and perpendicular to the ribbon plane was 1 to 150 cm² · V^-1 · sec⁻¹ and 50 to 700 cm² · V^−l · sec⁻¹, respectively. A solar cell using the present ribbon was made by means of a CVD silicon deposition method. Satisfactory diode characteristics and a conversion efficiency of about 5 % were obtained.