Electrochemical deposition of zinc selenide and cadmium selenide onto porous silicon from aqueous acidic solutions

An electrochemical deposition process of ZnSe and CdSe compound semiconductors from aqueous acidic solutions onto silicon substrates with porous silicon layers formed on their surfaces was studied by the voltammetry method. The experimental data obtained were compared with the deposition data onto metal and silicon substrates, and the optimal conditions for the binary compound deposition onto porous silicon were determined. Semiconductor films deposited were studied by scanning electron microscopy, X-ray diffractometry, and X-ray microanalysis. The films are shown to have the crystalline structure and a nearly stoichiometric composition with a minor Se excess. Further annealing in air for 15 min allowed the Se concentration to be decreased.     

Epitaxial growth of relaxed germanium layers by reduced pressure chemical vapour deposition on (110) and (111) silicon substrates

The growth of Ge on (110) and (111) oriented Si substrates is of great interest to enhance the mobility of both holes and electrons in complementary metal oxide semiconductor transistors. However, the quality of thick, relaxed Ge layers grown epitaxially on these surfaces is usually much lower than similar layers grown on (100) Si, resulting in both higher defect densities (i.e. threading dislocations and stacking faults) and rougher surfaces. In this work we have investigated the growth of Ge layers on (110) and (111) Si substrates by reduced-pressure chemical vapour deposition using a two temperature process. We have found that the combination of suppressing the Ge seed layer roughness and high temperature post-growth annealing can reduce the rms surface roughness of (110) Ge layers to below 2 nm and the threading dislocation density to below 1 × 10⁷ cm^− 2. Thick (111) Ge layers were found to exhibit a very high density of stacking faults, that could not be reduced by post-growth annealing and a higher rms surface roughness of around 12 nm, which was limited by the Ge seed layer.     

Hollow Structures Based on Prussian Blue and Its Analogs for Electrochemical Energy Storage and Conversion

Due to their special structural characteristics, hollow structures grant fascinating physicochemical properties and widespread applications, especially in electrochemical energy storage and conversion. Recently, the research of Prussian blue (PB) and its analog (PBA) related nanomaterials has emerged and has drawn considerable attention because of their low cost, facile preparation, intrinsic open framework, and tunable composition. Here, the recent progress in the study of PB‐ and PBA‐based hollow structures for electrochemical energy storage and conversion are summarized and discussed. First, some remarkable examples in the synthesis of hollow structures from PB‐ and PBA‐based materials are illustrated in terms of the structural architectures, i.e., closed single‐shelled hollow structures, open hollow structures, and complex hollow structures. Thereafter, their applications as potential electrode materials for lithium‐/sodium‐ion batteries, hybrid supercapacitors, and electrocatalysis are demonstrated. Finally, the current achievements in this field together with the limits and urgent challenges are summarized. Some perspectives on the potential solutions and possible future trends are also provided.     

One-step synthesis and self-organization of polypyrrole ultrathin films inlayed with Prussian blue nanoparticles induced by a drop of toluene solution on water surface

A strategy was described for one-step synthesis and self-organization of polypyrrole (PPy) ultrathin films inlayed with Prussian blue (PB) nanoparticles. The formation of ultrathin films is induced by a drop of toluene solution on aqueous surface, and the organization process is accompanied by the shrinkage of organic layer area on water surface due to the evaporation of toluene. On the one hand, the combination of the downward gravity force from the toluene solution of pyrrole and its upward buoyancy force drives the toluene solution of pyrrole to collapse downwards and scatter outwards on water surface. On the other hand, the strong adhesion ability of PPy and the hydrophobic action between the toluene solution of pyrrole and water drives the upper organic layer to reunite. In addition, the dispersion of toluene solvent toward pyrrole monomers and the retraction of its evaporation kinetics toward the produced PPyPB nanocomposites play a great role here. All of these forces yield a close-packed ultrathin PPy films with inlayed PB nanoparticles. The suggested strategy for preparing ultrathin films of PPy inlayed with PB nanoparticles is very simple. Due to the existence of PPy, the obtained composite films could be easily transferred and anchored onto the solid surface.     

水系钠离子电池普鲁士蓝正极材料的制备与电化学性能研究

普鲁士蓝(PB)是一种金属有机骨架配合物, 作为正极材料在水系钠离子电池中有广泛的应用前景。本文采用单一源法制备PB, 系统研究了反应温度、反应时间以及盐酸浓度对PB形貌结构和电化学性能的影响。研究结果表明, 升高反应温度能提高PB结晶性和循环稳定性, 以80 ℃合成的PB为正极材料组装的电池在100圈充放电循环后容量保持率为93.9%。延长反应时间可以使PB粒径增大, 但是反应时间超过6 h后PB粒径基本保持不变。延长反应时间有利于提高循环性能, 10 h所合成PB组装的电池在100圈充放电循环后容量保持率可以达到90%。提高盐酸浓度会改变PB的表面形貌, 同时改善电化学性能。盐酸浓度为0.20 mol/L时, 所得PB组装的电池经过100个循环后, 比容量仍有67.5 mAh/g。本研究可以为制备高性能PB基水系钠离子电池提供理论和实验指导。     

Hot-wire chemical vapor deposition of silicon nanoparticles on fused silica

Silicon nanoparticles on fused silica have potential as recombination centers in infrared detectors due quantum confinement effects that result in a size dependent band gap. Growth on fused silica was realized by etching in HF, annealing under vacuum at 700-750 °C, and cooling to ambient temperature before ramping to the growth temperature of 600 °C. Silicon particles could not be grown in a thermal chemical vapor deposition (CVD) process with adequate size uniformity and density. Seeding fused silica with Si adatoms in a hot-wire chemical vapor deposition (HWCVD) process at a disilane pressure of 1.1 × 10^− 5 Pa followed by thermal CVD at a disilane pressure of 1.3 × 10^− 2 Pa, or direct HWCVD at a disilane pressure of 2.1 × 10^− 5 Pa led to acceptable size uniformity and density. Dangling bonds at the surface of the as-grown nanoparticle were passivated using atomic H formed by cracking H₂ over the HWCVD filament.     

Electroless deposition of bismuth on Si(111) wafer from hydrogen fluoride solutions

Thin Bi layers were deposited by simple immersion of silicon chip into diluted HF aqueous solution, containing bismuth(III) ions. Bi nanoparticles or continuous up to 300 nm thick Bi film can be grown on silicon by the variation of the temperature and deposition time. Prepared surfaces have been characterized by atomic force microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, Raman scattering, photoluminescence and resistivity measurement methods. It was found that thinner Bi layers have a yellowish colour.     

Hot-wire chemical vapor deposition of high hydrogen content silicon nitride for solar cell passivation and anti-reflection coating applications

The stoichiometry and hydrogen content of hot-wire (HW)-grown silicon nitride was examined as a function of SiH₄/NH₃ flow ratio. The effect of post-deposition hydrogenation treatment on overall film hydrogen content was determined. The hydrogen release properties in Si-rich and N-rich nitride layers were characterized by annealing treatments. Defect hydrogenation was studied using Fourier transform infrared spectroscopy on platinum-diffused silicon substrates. HW nitride layers were deposited onto diffused emitter String Ribbon silicon substrates, producing cells with comparable short circuit current density, open circuit voltage, fill-factor, and efficiency to those fabricated using plasma chemical vapor deposition nitride layers.     

Ultrafast deposition of silicon nitride and semiconductor silicon thin films by hot wire chemical vapor deposition

The technology of Hot Wire Chemical Vapor Deposition (HWCVD) or Catalytic Chemical Vapor Deposition (Cat-CVD) has made great progress during the last couple of years. This review discusses examples of significant progress. Specifically, silicon nitride deposition by HWCVD (HW-SiN_x) is highlighted, as well as thin film silicon single junction and multijunction junction solar cells. The application of HW-SiN_x at a deposition rate of 3 nm/s to polycrystalline Si wafer solar cells has led to cells with 15.7% efficiency and preliminary tests of our transparent and dense material obtained at record high deposition rates of 7.3 nm/s yielded 14.9% efficiency. We also present recent progress on Hot-Wire deposited thin film solar cells. The cell efficiency reached for (nanocrystalline) nc-Si:H n-i-p solar cells on textured Ag/ZnO presently is 8.6%. Such cells, used in triple junction cells together with Hot-Wire deposited proto-Si:H and plasma-deposited SiGe:H, have reached 10.9% efficiency. Further, in our research on utilizing the HWCVD technology for roll-to-roll production of flexible thin film solar cells we recently achieved experimental laboratory scale tandem modules with HWCVD active layers with initial efficiencies of 7.4% at an aperture area of 25 cm².     

The effect of argon dilution on deposition of microcrystalline silicon by microwave plasma enhanced chemical vapor deposition

Microwave plasma-enhanced chemical vapor deposition (PECVD) is a very promising method for industrial scale fabrication of microcrystalline silicon solar cells since the technique is well applicable for large areas, and high deposition rates can be obtained. We have investigated the effect of Ar dilution on the growth process and the material properties of microcrystalline silicon. The major benefit of Ar addition in the MWPECVD process, using H₂ and SiH₄ as reactant gases, is an improved stabilization of the plasma, in particular at low pressure and MW power. We show, however, that material properties of the microcrystalline silicon layers deteriorate if we partly substitute H₂ by Ar during the deposition. The density of the layers - as expressed by the refractive index - decreases, and the defect density (measured by Fourier transform photocurrent spectroscopy) increases with increasing Ar flow. Investigation of the plasma by optical emission study shows that Ar atoms play a very active role in the dissociation processes of H₂ and SiH₄. Substitution of H₂ by Ar decreases the SiH^? emission and increases the Si^? emission. On the other hand, the H_α/H_β ratio increases upon substitution of H₂ by Ar. The latter effect shows that Ar addition does not lead to higher electron temperatures and we conclude that the changes of SiH^? and Si^? emissions are due to dissociation of SiH₄ by Ar^? (quenching reactions). The precise role of Ar in MWPECVD of microcrystalline silicon needs further investigation, but we conclude that the usage of this gas should be minimized in order to maximize the quality of the silicon layers.     

Immobilization of dendrimers on Si-C linked carboxylic acid-terminated monolayers on silicon(111)

Poly(amidoamine) dendrimers were attached to activated undecanoic acid monolayers, covalently linked to smooth silicon surfaces via Si-C bonds. The resulting ultra-thin dendrimer films were characterized by X-ray photoelectron spectroscopy (XPS), X-ray reflectometry (XR) and atomic force microscopy (AFM). XPS results suggested amide bond formation between the dendrimer and the surface carboxylic acid groups. XR yielded thicknesses of 10 Å for the alkyl region of the undecanoic acid monolayer and 12 Å for the dendrimer layer, considerably smaller than the diameter of these spherical macromolecules in solution. This was consistent with AFM images showing collapsed dendrimers on the surface. It was concluded that the deformation arose from a large number of amine groups on the surface of each dendrimer reacting efficiently with the activated surface, whereby the dendrimers can deform to fill voids while spreading over the activated surface to form a homogeneous macromolecular layer.     

A Prussian blue route to nitrogen-doped graphene aerogels as efficient electrocatalysts for oxygen reduction with enhanced active site accessibility

Developing high-performance nonpredous-metal electrocatalysts for the oxygen reduction reaction (ORR) is crudal for a variety of renewable energy conversion and storage systems.Toward that end,rational catalyst design principles that lead to highly active catalytic centers and enhanced active site accessibility are undoubtedly of paramount importance.Here,we used Prussian blue nanoparticles to anchor Fe/Fe3C species to nitrogen-doped reduced graphene oxide aerogels as ORR catalysts.The strong interaction between nanosized Fe3C and the graphitic carbon shell led to synergistic effects in the ORR,and the protection of the carbon shell guaranteed stability of the catalyst.As a result,the aerogel electrocatalyst displayed outstanding activity in the ORR on par with the state-of-the-art Pt/C catalyst at the same mass loading in alkaline media,good performance in acidic media,and excellent stability and crossover tolerance that rivaled that of the best nonprecious-metal ORR electrocatalysts reported to date.     

Direct electrochemistry and electrocatalytic behavior of hemoglobin entrapped in chitosan/gold colloid/3-aminopropyl triethylene silane/Prussian blue composite film

Direct electrochemistry of hemoglobin (Hb) is achieved by immobilizing Hb-chitosan on a gold colloid/3-aminopropyl triethylene silane/Prussian blue composite film-modified glassy carbon electrode. The modified electrode exhibits a pair of well defined and quasi-reversible peaks with a formal potential of 0.205 V. The immobilized Hb retains its biological activity and shows high catalytic activity to the reduction of hydrogen peroxide. Experimental conditions influencing the biosensor performances such as pH and potential are optimized and assessed. Under the optimized conditions, the catalytic currents are linear to the concentrations of H₂O₂ in the ranges of 2-480 μM. The detection limit is 0.1 μM (S/N = 3). The electrochemical sensor has high stability and good reproducibility. Ultraviolet visible absorption spectra and Fourier transform infrared spectroscopy show that Hb keeps almost natural structure in the composite film. Therefore, the composite film is an alternative matrix for protein immobilization and biosensor preparation.     

多金属普鲁士蓝类化合物亚铁氰化铜镍钴对铯离子的吸附

采用共沉淀法制备了一种多金属普鲁士蓝类化合物——亚铁氰化铜镍钴(CNC-PB),采用TEM、FTIR对其进行了表征,并利用XRF和穆斯堡尔谱对CNC-PB吸附交换铯离子的机理进行了初步分析。通过静态吸附实验,研究了吸附时间、pH值、Na~+浓度、初始Cs~+浓度、CNC-PB投加量等因素对吸附效果的影响,分析了吸附过程的反应动力学和吸附等温线。结果表明,随着溶液pH值的增大,CNC-PB对Cs~+的吸附量先增大后减少,吸附速度较快;在氯化钠溶液中,CNC-PB对Cs~+具有极高的选择性吸附能力;CNC-PB对Cs~+的吸附过程符合准二级动力学方程模型和Langmuir单分子吸附模型,最大吸附量为130.81mg/g。     

Electrochemical deposition and superhydrophobic behavior of ZnO nanorod arrays

Vertically aligned ZnO nanorod arrays with different heights are grown on the ZnO seeded indium tin oxide substrate by cathodic electrochemical deposition from zinc nitrate at two temperatures of 60 °C and 80 °C. As-grown ZnO nanorods exhibit wurzite crystal structure and their heights can be well controlled by different deposition times. The fluorination coating tends to induce a superhydrophobicity of ZnO nanorods, i.e., the maximal value of contact angle: 166.9°. The super water repellency can be attributed to the fact that an air layer is confined in the nanorod arrays, and thus leads to water droplets sitting on the ZnO surfaces, referring as Cassie state. Interestingly, their water contact angles are found to vary with the heights of ZnO nanorods, ranged from 99.8 to 746 nm. The superhydrophobicity of ZnO surfaces can be well predicted by a proposed model that is capable of determining the wetted fraction of ZnO pillars. This satisfactory result would shed one light on how the variation of rod height would induce the superhydrophobic behavior of ZnO nanorod arrays.     

Growth of long aligned carbon nanotubes on amorphous hydrogenated silicon nitride by thermal chemical vapor deposition

Vertically aligned long carbon nanotubes in the range of 80-100 µm have been synthesized on amorphous hydrogenated silicon nitride (a-SiN_x:H) coated silicon substrate by thermal chemical vapor deposition of ferrocene and xylene. It is observed that high temperature annealing in oxygen ambient results in formation of crystalline silicon dioxide in the matrix of amorphous silicon nitride due to out diffusion of hydrogen. It is suggested that active sites created on silicon dioxide and a-SiN_x:H clusters provide mechanical support for the alignment of long carbon nanotubes. It is proposed that a thin layer of a-SiN_x:H prevents silicide formation between the catalyst (Fe) and silicon thus lengthening the catalyst life.     

热化学气相沉积法在硅纳米丝上合成碳纳米管

利用热化学气相沉积法在负载不同厚度催化剂的硅纳米丝(SiNW)表面生长碳纳米管(CNTs),探讨了生长条件对所合成SiNW-CNT的结构和场发射特性的影响.这种类似树状的三维结构具有较高碳纳米管表面密度及降低的电场筛除效应等潜在优势.使用拉曼光谱( Raman)、电子显微镜(SEM)、透射电子显微镜(TEM)、能量扩散分光仪(EDS)分析了碳纳米管的结构性质,并在高真空下施加电场测得碳纳米管的场发射特性.结果表明:随硅纳米丝上负载催化剂镍膜厚度的变化,所合成碳纳米管的表面特性、结晶结构及功函数改变,导致电子发射难易程度的改变,进一步影响碳纳米管的场发射特性.     

Si(111)衬底上生长GaN晶绳的研究

利用热壁化学气相沉积在Si(111)衬底上获得GaN品绳,采用傅里叶红外吸收谱(FTIR)、扫描电子显微镜(SEM)、选区电子衍射(SAED)、X射线衍射(XRD)和光致发光谱(PL)对晶绳进行组成、结构、形貌和光学特性分析。初步结果证明：在Si(111)衬底上获得择优生长的六方纤锌矿结构的GaN晶绳。SEM显示在均匀的薄膜上出现φ6μm的晶绳,FTIR显示GaN薄膜的主要成分为GaN同时含有少量的C污染,由XRD和SAED的综合分析得出晶绳呈六方纤锌矿单晶结构,PL测试表明晶绳呈现不同于GaN薄膜的发光特性。