Large photocurrent-response observed at Pt/InP Schottky interface formed on anodic porous structure

A photoelectric-conversion device—based on an InP porous structure utilizing the large surface area inside pores and the low reflectance on the porous surface—is proposed. The InP walls inside the pores are covered with thin platinum films that form a Schottky barrier yielding an electric field that separates photo carriers generated under illumination. The coverage of the platinum film and its optical reflectance depended largely on the surface morphology of the porous structure. Removal of the irregular top layer formed at the initial stage of the pore formation effectively improved the coverage of the platinum film, which showed a very low optical reflectance (i.e., below 3.2%). According to current-voltage measurements under illumination, the platinum/porous InP showed larger photocurrents and higher responsivity than those of a reference planar sample.     

A high-coverage nanoparticle monolayer for the fabrication of a subwavelength structure on InP substrates

Subwavelength structures (SWSs) were fabricated on the Indium Phosphide (InP) substrate by utilizing the confined convective self-assembly (CCSA) method followed by reactive ion etching (RIE). The surface condition of the InP substrate was changed by depositing a 30-nm-thick SiO2 layer and subsequently treating the surface with O2 plasma to achieve better surface coverage. The surface coverage of nanoparticle monolayer reached 90% by using O2 plasma-treated SiO2/InP substrate among three kinds of starting substrates such as the bare InP, SiO2/InP and O2 plasma-treated SiO2/InP substrate. A nanoparticle monolayer consisting of polystyrene spheres with diameter of 300 nm was used as an etch mask for transferring a two-dimensional periodic pattern onto the InP substrate. The fabricated conical SWS with an aspect ratio of 1.25 on the O2 plasma-treated SiO2/InP substrate exhibited the lowest reflectance. The average reflectance of the conical SWS was 5.84% in a spectral range between 200 and 900 nm under the normal incident angle.     

多级开孔壳聚糖海绵的细胞行为分析

使用冰滴为致孔剂制备表面大孔、内部孔洞相连的新型壳聚糖(HPCS)支架,将其与聚乳酸复合制备出三维蜂窝状孔洞结构的复合支架(THCP).对HPCS和THCP进行了表面形貌、力学性能、细胞相容性等方面的表征,并与常规冻干法所制备的壳聚糖(CS)海绵进行了对比.结果表明,在HPCS海绵表面均匀分布着大而开放的孔洞,大孔内部...     

Effect of porous silicon stain etched on large area alkaline textured crystalline silicon solar cells

This work shows the effects of porous silicon stain etched on alkaline textured antireflection coatings of large area monocrystalline silicon solar cells. The texturization process has been produced by immersion of the silicon wafers in different carbonate-based solutions. The porous silicon layers were formed by stain etching in a HNO₃/HF aqueous solution before or after the texturization process. We study the effects of different alkaline and acidic solutions and the etching times on the solar cell parameters and the surface reflectance of the device. We have found that the average reflectance of the surface is lowered when the porous etching is combined with the texturization in the alkaline solution. However, the solar cell characteristics are not improved.     

Porous SnIn4S8 microspheres in a new polymorph that promotes dyes degradation under visible light irradiation

Porous SnIn(4)S(8) microspheres were initially synthesized through a facile solvothermal approach and were investigated as visible-light driven photocatalysts for dyes degradation in polluted water. The photocatalysts were characterized by XRD, SEM, TEM, N(2) adsorption-desorption, and UV-vis diffuse reflectance techniques. Results demonstrated that the as-synthesized SnIn(4)S(8) was of a new tetragonal polymorph, showing a band-gap of 2.5 eV, a specific surface area of 197 m(2) g(-1), and an accessible porous structure as well. The photocatalytic activity of the porous SnIn(4)S(8) was evaluated by decomposition of several typical organic dyes including methyl orange, rhodamine B, and methylene blue in aqueous solution under visible light irradiation. It is demonstrated that porous SnIn(4)S(8) was highly photoactive and stable for dyes degradation, showing photocatalytic activity much higher than binary constituent sulfides like In(2)S(3), SnS(2), or even ternary chalcogenide ZnIn(2)S(4) photocatalyst. The excellent photocatalytic performance of porous SnIn(4)S(8) is the consequence of its high surface area, well-defined porous texture, and large amount of hydroxyl radicals.     

Characterization of nanoporous silicon layer to reduce the optical losses of crystalline silicon solar cells

Reduction of optical losses in crystalline silicon solar cells by surface modification is one of the most important issues of silicon photovoltaics. Porous Si layers on the front surface of textured Si substrates have been investigated with the aim of improving the optical losses of the solar cells, because an anti-reflection coating and a surface passivation can be obtained simultaneously in one process. We have demonstrated the feasibility of a very efficient porous Si AR layer, prepared by a simple, cost effective, electrochemical etching method. Silicon p-type CZ (100) oriented wafers were textured by anisotropic etching in sodium carbonate solution. Then, the porous Si layers were formed by electrochemical etching in HF solutions. After that, the properties of porous Si in terms of morphology, structure and reflectance are summarized. The structure of porous Si layers was investigated using SEM. The formation of a nanoporous Si layer on the textured silicon wafer result in a reflectance lower than 5% in the wavelength region from 500 to 900 nm. Such a surface modification allows improving the Si solar cell characteristics. An efficiency of 13.4% is achieved on a monocrystalline silicon solar cell using the electrochemical technique.     

CeO2/石墨烯的合成及其在光催化制氢中的应用

采用具有丰富分级多孔结构的豆芽为模板,经水热法合成仿生形态的纳米CeO₂/石墨烯催化剂。使用XRD、拉曼光谱（Raman）、TEM、场发射扫描电子显微镜（FESEM）、紫外-可见漫反射光谱（UV-Vis/DRS）、N₂吸附-脱附仪和光解水制氢系统等分析表征手段对CeO₂/石墨烯催化剂的结构、形貌及光催化性能进行分析。结果表明,所制备的CeO₂/石墨烯光催化剂不仅继承了豆芽模板高孔隙率和大比表面积的特点,而且保持了豆芽的形态和微观特征。该催化剂是由约5.6 nm CeO₂纳米晶与具有生物形态的仿生石墨烯片层结构结合而成。制得的CeO₂/石墨烯复合材料内部存在大量由CeO₂/石墨烯催化剂纳米颗粒堆积而成的纳米孔,其孔径集中分布于15~45 nm左右,这种微观结构使CeO₂/石墨烯催化剂具有超大的比表面积,提高了催化剂对光生电子空穴对的捕获能力。由紫外-可见漫反射吸收光谱可知,CeO₂/石墨烯复合材料的可见光利用率显著增强,光解水制氢效率6 h后可达到671 μmol（h · g）^-1,远高于标样CeO₂的51.67 μmol（h · g）^-1。     

Thermal diffusion in nanostructured porous InP

Nanostructured porous InP samples were prepared by electrochemical anodic dissolution of InP for various current densities and etching periods. The samples were characterized by SEM and photoluminescence (PL) where a blue shift was observed in PL. Thermal properties studied by photoacoustic (PA) spectroscopy revealed one order decrease in thermal conductivity of porous InP compared to the bulk. Further it is shown that the thermal conductivity of porous InP decreases with decrease in size of the particles.     

Development of titanium-dioxide-based aerogel catalyst with tunable nanoporosity and photocatalytic activity

Nanostructured highly porous TiO(2)/WO(3)/Fe(3+) aerogel composite photocatalysts are prepared, characterized and tested for model photocatalytic reactions. The catalyst structure is tailored to capture environmental pollutants and enable their decomposition in situ under both ultraviolet (UV) and visible light through oxidation to smaller benign molecules. A novel and green method is utilized to prepare the unique surfactant-templated aerogel composite photocatalyst that has a highly accessible porous nanostructure with high surface area and tailored pore size distribution. The sol-gel process is combined with supercritical extraction and drying. Supercritical drying with heat treatment results in titanium dioxide with anatase crystal form. Templates used further enable retention and tuning of the nanopore structure and surface properties. The synthesized catalysts were characterized using SEM, FIB, XRD and porosimetry prior to post-evaluation in model reactions. The bandgap of the catalyst particles was also determined using diffuse reflectance. The resulting aerogel TiO(2)/WO(3)/Fe(3+) has similar photocatalytic capability compared to highly optimized commercial Degussa P25 under UV exposure and offers much superior photocatalytic capability under visible light exposure. The model reaction utilized employed methylene blue (MB) photooxidation under visible and UV light.     

InP Quantum Dots: Synthesis and Lighting Applications

InP quantum dots (QDs) are typical III–V group semiconductor nanocrystals that feature large excitonic Bohr radius and high carrier mobility. The merits of InP QDs include large absorption coefficient, broad color tunability, and low toxicity, which render them promising alternatives to classic Cd/Pb‐based QDs for applications in practical settings. Over the past two decades, the advances in wet‐chemistry methods have enabled the synthesis of small‐sized colloidal InP QDs with the assistance of organic ligands. By proper selection of synthetic protocols and precursor materials coupled with surface passivation, the QYs of InP QDs are pushed to near unity with modest color purity. The state‐of‐the‐art InP QDs with appealing optical and electronic properties have excelled in many applications with the potential for commercialization. This work focuses on the recent development of wet‐chemistry protocols and various precursor materials for the synthesis and surface modification of InP QDs. Current methods for constructing light‐emitting diodes using novel InP‐based QDs are also summarized.     

InP/InGaAsP异质结ICP刻蚀表面损伤(英文)

本文详细研究了采用Cl_2/H_2刻蚀气体时,ICP刻蚀系统对InP/InGaAsP材料表面损伤的影响。通过设计特殊结构的InP/InGaAsP多量子阱结构,测量刻蚀区域及非刻蚀区域的光荧光强度的变化,并结合高斯深度分布模型对刻蚀损伤进行定量研究。详细研究ICP刻蚀系统中的压强、ICP功率、RF功率以及Cl_2/H_2刻蚀气体组分对损伤程度的影响。基于这些结果优化得到一组低损伤参数,最终实现刻蚀损伤深度小于16nm。     

Simulation of the spectra and determination of the optical constants of online low-emission glass from visible to mid-infrared region

Online low emissivity glass (Low-E glass) is a promising glass product. Simulation of the spectra and determination of the optical constants of online Low-E glass are of practical interest for many applications such as product design, adjustment of coating process and comparison of samples produced using different methods. The online Low-E glass investigated here has two layers of films on 6 mm thick float glass substrate, which include the functional layer (the upper layer) and the transition layer (the lower layer). In this paper, the relation between transmittance and the parameters used in the model in the visible and near-infrared region was derived, so was the relation between reflectance and the parameters used in the model in the infrared region. The parameters used in the model were obtained by fitting the measured and simulated spectra. From the obtained parameters, the optical constants of the functional layer of online Low-E glass in the visible region and the infrared region were obtained, respectively. The sheet resistance and the infrared reflectance of Low-E glass were also calculated from the obtained fitting parameters. The simulated results are well consistent with the experimental ones.     

Optical characterization of porous silicon and crystalline silicon by the Kramers-Kronig method

The electronic structure of porous silicon (PS) has been characterized by optical reflectance spectra analyses. Using a Cary-500 spectrometer, the reflectance spectra of PS are measured in the photon energy range of 0.4-6 eV. The spectral responses of optical constants are calculated for PS and Si by Kramers-Kronig analysis. The analysis clarified strong evidence for widening and direct bandgaps for PS samples. Also, the optical constants of PS layers as a function of porosity have been studied. Our results indicate that PS retains some of the characteristic optical features of crystalline Si. However, in the visible region, PS shows that the imaginary part of the complex refractive index increases, and the real part decreases as porosity increases. This feature could be related to the surface roughness of PS and its role in surface absorption and scattering.     

Study by AES and EELS spectroscopies of antimony and phosphorus evaporated on massive indium and on cleaned InP

In this paper, we give some results related to interaction mechanism between the elements V such as antimony or phosphorus with the metal indium. We used both powerful spectroscopy methods the Auger electron spectroscopy (AES) and the electron energy loss spectroscopy (EELS) for which the spectra were recorded in direct mode N(E). The antimony was evaporated on pure In metal or on cleaned InP surface involving the In metal because of its cleaning by the argon ion bombardment at low energy 300 eV. The antimony flow composed of Sb₄ species arrived with a thermal energy on the In metal surface. Such an energy was sufficient to their diffusion into the In matrix because of the low melting point of In metal (123 °C). A nucleation phenomenon occurred between Sb₄ and the In metal to form small islands of antimony metal in bulk. Further antimony evaporation enabled to increase the size of these islands towards the surface. However, the antimony evaporated on cleaned InP reacted chemically with the In metal distributed on the InP surface to form a thin layer of InSb. The inner stoichiometric layers of InP and the size of Sb₄ species and also the stability of InP versus the temperature impeded the interdiffusion phenomenon of antimony to occur deeply into the InP matrix. The InSb layer played the role to stabilise the surface of the InP compound versus the heating at 450 °C and the electron irradiation of 4 KeV energy. But, the phosphorus evaporation on In metal or on cleaned InP led to form chemical bonds InP. The phosphorus flow included chemical species P and P₂ with a thermal energy able to stimulate the chemical reactivity process between indium and phosphorus to form the InP compound.     

多孔硅的高效可见光发射来自其表面

用扫描电镜继续对发光多孔硅的阴极射线发光进行了系统的研究,得到了其阴极荧光发射部位、强度分布显微照片,发现在样品的表面层脱落处（暴露着多孔层大量微孔）无阴极射线发光产生,只有表面层未脱落处才有阴极射线发光;对样品的截面实验研究同样清楚地表明多孔硅样品的阴极射线发光只来源于其表面层,多孔层、硅单晶衬底区域不发生阴极射线发光．实验还提供了阴极射线发光强度在截面上随深度变化情况显微照片．阴极射线发光光谱表明其光谱峰值位置在680nm处,相似于多孔硅的光致发光．实验结果再次表明多孔硅的可见光来源于其表面层中的荧光物质．     

VLS growth of alternating InAsP/InP heterostructure nanowires for multiple-quantum-dot structures

We investigated the Au-assisted growth of alternating InAsP/InP heterostructures in wurtzite InP nanowires on InP(111)B substrates for constructing multiple-quantum-dot structures. Vertical InP nanowires without stacking faults were obtained at a high PH(3)/TMIn mole flow ratio of 300-1000. We found that the growth rate changed largely when approximately 40 min passed. Ten InAsP layers were inserted in the InP nanowire, and it was found that both the InP growth rate and the background As level increased after the As supply. We also grew the same structure using TBAs/TBP and could reduce the As level in the InP segments. A simulation using a finite-difference time-domain method suggests that the nanowire growth was dominated by the diffusion of the reaction species with long residence time on the surface. For TBAs/TBP, when the source gases were changed, the formed surface species showed a short diffusion length so as to reduce the As background after the InAsP growth.     

辐照对红外熔石英性质的影响(英文)

研究了高能电子、高能质子辐照对红外熔石英性质、光学面形的影响。研究了高能电子对红外熔石英面形的影响 ,结果表明 ,没有明显的面形变化。研究了高能质子对红外熔石英面形、可见和红外反射特性的影响。研究结果表明 ,没有观察到高能质子辐照对红外熔石英面形和反射特性的影响     

Photocatalytic Properties of Porous Silicon Nanowires

Porous silicon nanowires are synthesized through metal assisted wet-chemical etch of highly-doped silicon wafer. The resulted porous silicon nanowires exhibit a large surface area of 337 m(2)·g(-1) and a wide spectrum absorption across the entire ultraviolet, visible and near infrared regime. We further demonstrate that platinum nanoparticles can be loaded onto the surface of the porous silicon nanowires with controlled density. These combined advancements make the porous silicon nanowires an interesting material for photocatalytic applications. We show that the porous silicon nanowires and platinum nanoparticle loaded porous silicon nanowires can be used as effective photocatalysts for photocatalytic degradation of organic dyes and toxic pollutants under visible irradiation, and thus are of significant interest for organic waste treatment and environmental remediation.     

Room-temperature formation of low refractive index silicon oxide films using atmospheric-pressure plasma

This study aims to apply atmospheric-pressure (AP) plasma to the fabrication of single-layer anti-reflection (AR) coatings with porous silicon oxide. 150 MHz very high-frequency (VHF) excitation of AP plasma permits to enhance the chemical reactions both in the gas phase and on the film-growing surface, increasing deposition rate significantly. Silicon oxide films were prepared from silane (SiH4) and carbon dioxide (CO2) dual sources diluted with helium. The microstructure and refractive index of the films were studied using infrared absorption and ellipsometry as a function of VHF power density. It was shown that significant increase in deposition rate at room temperature prevented the formation of a dense SiO2 network, decreasing refractive index of the resulting film effectively. As a result, a porous silicon oxide film, which had the lowest refractive index of 1.24 at 632.8 nm, was obtained with a very high deposition rate of 235 nm/s. The reflectance and transmittance spectra showed that the low refractive index film functioned as a quarter-wave AR coating of a glass plate.     

Single-layered porous silica films on polyethylene terephthalate substrates for antireflection coatings

Single-layered porous silica films were prepared on polyethylene terephthalate (PET) substrates as antireflection coatings for efficient, large-scale flexible optoelectronic devices. Cetyltrimethylammonium bromide (CTAB)-templated synthesis was employed to form porous silica films. Without using high temperature treatment, CTAB was removed by washing in water to create a porous structure in the films. To spin-coat on PET substrates, contact angle between silica sol and PET surface was measured to optimize the molar ratio of the solution. Pore size and surface sharpness were estimated using atomic force microscope data. The average reflectance of as-prepared AR coatings on PET substrates was ≤ 2%.