Porous indium oxide thin films deposited by electrostatic spray deposition technique

This paper presents the preparation process of porous indium oxide (In₂O₃) films using a novel deposition technique, i.e., electrostatic spray deposition (ESD). The films were deposited on platinum-coated alumina substrates using as precursor solution indium chloride in ethanol and acetic acid. The films were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. The nanocrystalline structure of the films was evidenced by TEM and also by XRD studies. The Raman spectroscopy and XRD measurements revealed the cubic phase of In₂O₃ films. Considering the obtained results, we conclude that the ESD technique is an efficient, cheap and successful method for the preparation of porous indium oxide films.     

Combined photoelectrochemical conditioning and surface analysis of InP photocathodes: II. Photoelectron spectroscopy

The photoelectrochemical modification of p-InP(111) surfaces in HCl and H₂SO₄ is investigated. In 0.5 M HCl a photoreduction/oxidation procedure via cyclic voltammetry leads to a solar energy conversion efficiency of the p-InP/vanadium^2+,3+—4 M HCl/C photoelectrochemical solar cell (PECS) of η=11.6% in natural sunlight. The optimisation procedures are followed by surface analysis methods performed ex-situ at the modified InP electrodes after cathodic and after anodic polarisation in the supporting acidic electrolytes and in the redox solution. X-ray photoelectron spectroscopy (XPS), ultraviolet photoelectron spectroscopy (UPS) and low energy electron diffraction (LEED) are used. At cathodic polarisation in H₂SO₄, XPS shows formation of indium metal and In_x(SO₄)_y compounds, whereas in HCl a stable interfacial film consisting of indium monochloride to a smaller extent of indium oxides is formed. This film is optimised by cycling in HCl having a thickness of 10±3 Å. Cyclic polarisation in the vanadium redox electrolyte changes the composition and thickness. Whereas in HCl, the optimised interphase consists of 0.7 parts InCl and 0.3 parts In(PO₃)₃, phosphates are absent after optimisation in V^2+/3+ and more indium oxide is found. The film thickness is reduced to 6±2 Å for the InCl component and about 0.6 monolayers of indium oxide are found. UPS measurements are mainly used to derive an energy band diagram of the semiconductor/film/electrolyte junction. The results show in that the stabilisation of the film in chloride containing electrolytes can be explained by the relative conduction band positions of p-InP with respect to cathodic decomposition energies. Since the electron affinity increases with surface phase formation in HCl, whereas it stays low in sulphuric acid, the ongoing corrosion in the latter solution can be understood, the LEED data show that the surface phase is ordered with lattice constants close to InP, indicating the formation of a hitherto unknown InOCl phase. According to the results we propose reaction mechanisms for dissolution and stabilisation and present schematic energy band diagrams which explain the corrosion processes in H₂SO₄ and the passivation phenomenon in HCl. The influence of the properties of the interfacial film on the functioning of the solar cell is outlined.     

Flüssig/Flüssig‐Extraktion von Indium aus sauren Lösungen

The extraction of indium from a synthetic sulfate‐containing solution using commercial reagents (Cyanex 272, DEHPA, and Cyanex 923) is evaluated on a comparative basis. The extraction profiles of indium (III) were examined with regard to the reagent concentration, the pH value of the aqueous solution, and the indium concentration in a low phase ratio of 1:10. DEHPA and Cyanex 272 are, in contrast to Cyanex 923, very well suited for the extraction of indium. Re‐extraction with HCl and H₂SO₄ is compared.     

金属铟促进的各类反应

金属铟在室温下不能被空气或氧气氧化,这与其它金属比起来是一个很大的优势。铟促进的反应在室温下在水中就可顺利进行,不需要加热也不需要超声波进行辅助。综述了金属铟近年来参与的各类有机反应,诸如烯丙基化反应、炔丙基化反应等,总结了这些化学反应的最新研究进展并介绍了金属铟促进的一些新型反应的特点及其优势。     

Electrodeposition of indium onto Mo/Cu for the deposition of Cu(In,Ga)Se2 thin films

A study of the electrodeposition and the oxidation process of indium on Mo/Cu substrates from a bath containing 0.008 M InCl₃, 0.7 M LiCl at pH 3 is described in this work. The voltamperometric study showed a reduction process which corresponds to the conversion of In³⁺ to In⁰ and an oxidation process which takes place in different steps. Utilizing the chronoamperometric technique the total efficiency of process, the number of monolayers, the film thickness and the diffusion coefficient were evaluated. The analysis of current transients, using theoretical growth model, showed that the electrodeposition of indium adjusts to a three-dimensional growth under instantaneous nucleation limited by diffusion. The kinetic growth parameters were evaluated through a non-linear fit. The films were characterized by X-ray diffraction and scanning electron microscopy techniques. These studies showed that the films were of crystalline in nature with compact and uniform surface, even for the film with a deposition time of 1 min.     

Palladium nanoparticles on InP for hydrogen detection

Layers of palladium (Pd) nanoparticles on indium phosphide (InP) were prepared by electrophoretic deposition from the colloid solution of Pd nanoparticles. Layers prepared by an opposite polarity of deposition showed different physical and morphological properties. Particles in solution are separated and, after deposition onto the InP surface, they form small aggregates. The size of the aggregates is dependent on the time of deposition. If the aggregates are small, the layer has no lateral conductance. Forward and reverse I-V characteristics showed a high rectification ratio with a high Schottky barrier height. The response of the structure on the presence of hydrogen was monitored.     

The accelerating and retarding effects of hydrogen on carbon deposition on metal surfaces

Carbon deposition of benzene on iron was studied at 550–700°C with 0–1 atm hydrogen in the carrier gas. At least three types of carbon are formed: amorphous, graphitic and carbidic (Fe₃C). The surface of Fe₃C is essentially inactive for benzene decomposition. In the presence of H₂, a metallic surface is maintained resulting in a high activity and hence an accelerating effect by H₂. In the reaction system five competing reactions are involved and the net rate of carbon deposition is the sum of the individual rates. Based on the results in this study, the retarding effects of H₂ on carbon deposition reported in the literature can also be explained. The methanation reaction of surface carbon by H₂ becomes important under conditions when the surface is relatively inactive for hydrocarbon decomposition, and under such conditions, H₂ has a retarding effect on carbon deposition.     

Zinc deposition and dissolution in sulfuric acid onto a graphite–resin composite electrode as the negative electrode reactions in acidic zinc-based redox flow batteries

Electrodeposition and dissolution of zinc in sulfuric acid were studied as the negative electrode reactions in acidic zinc-based redox flow batteries. The zinc deposition and dissolution is a quasi-reversible reaction with a zinc ion diffusion coefficient of 4.6 × 10^?6 cm² s^?1 obtained. The increase of acid concentration facilitates an improvement in the kinetics of zinc electrodeposition–dissolution process. But too high acid concentration would result in a significant decrease in charge efficiency. The performance of the zinc electrode in a three-electrode system with magnetic stirring was also studied as a function of Zn(II) ion concentration, sulfuric acid concentration, current density, and the addition of additives in 1 M H₂SO₄ medium. The optimum electrolyte composition is suggested at high zinc(II) concentration (1.25 M) and moderate sulfuric acid concentration (1.0–1.5 M) at a current density range of 20–30 mA cm^?2. Whether in acid-free solution or in sulfuric acid solution with or without additives, no dendrite formation is observed after zinc electrodeposition for 1 h at 20 mA cm^?2. The energy efficiency is improved from 77 % in the absence of additives in 1 M H₂SO₄ medium to over 80 % upon the addition of indium oxide or SLS–Sb(III) combined additive as hydrogen suppressants.     

Oxalate as an intermediate in the base-catalysed water-gas shift reaction

The conversion of CO to H₂ and CO₂, in the presence of 1.0 M solutions of sodium carbonate, hydroxide and formate has been studied in the temperature range 200–350 °C. The decomposition of 1.0 M solutions of sodium formate, oxalate and carbonate under argon pressure was investigated using the same reaction conditions. It is shown that carbonate reacts readily with CO to produce oxalate, which decomposes easily to formate and CO₂. The formate is the most stable intermediate under the reaction conditions and only decomposes rapidly to carbonate and H₂ above 300 °C, making the water-gas shift reaction truly catalytic. Sodium hydroxide is not an intermediate in this reaction but first reacts with CO₂, formed during the reaction, to produce carbonate. Based on these results a new mechanism is proposed for the base-catalysed water-gas shift reaction.     

Fabrication and characterization of Ag-Decorated indium–tin-oxide nanoparticle based ethanol sensors using an enhanced electrophoretic method

In this paper different Indium Tin Oxide (ITO)-based ethanol vapor sensors (fabricated as thin films and nanoparticles) are presented, and their structural and sensing properties are investigated. An Electrophoretic Deposition (EPD)-Enhanced method is proposed for the fabrication of pure, and Ag-decorated indium tin oxide sensors. The proposed sensors are then compared to conventional indium tin oxide sensors fabricated by sputtering (thin film), and drop-casting method in terms of response, and working temperature. It is shown that the electrophoretic deposition method has decreased the final particle size of the indium tin oxide nanoparticles by limiting the agglomeration of nanoparticles, and increased the sparsity of the particles forming the sensing material. Results suggest that compared to the conventional sensors, the sensors fabricated by the proposed electrophoretic deposition method (i.e., the pure-indium tin oxide (EPD-TF), and the Ag-decorated indium tin oxide (Ag-EPD) sensors), has considerably better performance for the detection of the ethanol vapors, showing reduced working temperature (110 and 130 °C, respectively), higher response, and better selectivity over CO, methane, methanol, and acetone. Moreover, the response and recovery time of the proposed sensors were found to be lower than most of the previously reported indium tin oxide-based ethanol sensors, approving the positive effect of the electrophoretic method as a simple, controllable method for sensor fabrication.     

Preparation and characterization of single crystalline In2O3 films deposited on MgO (110) substrates by MOCVD

Epitaxial indium oxide (In₂O₃) films have been prepared on MgO (110) substrates by metal-organic chemical vapor deposition (MOCVD). The deposition temperature varies from 500 °C to 700 °C. The films deposited at each temperature display a cube-on-cube orientation relation with respect to the substrate. The In₂O₃ film deposited at 600 °C exhibits the best crystalline quality. A clear epitaxial relationship of In₂O₃ (110)|MgO (110) with In₂O₃ [001]|MgO [001] has been observed from the interface area between the film and the substrate. The average transmittance of the prepared films in the visible range is over 95%. The band gap of the obtained In₂O₃ films is about 3.55–3.70 eV.     

Indium droplet formation in InGaN thin films with single and double heterojunctions prepared by MOCVD

Indium gallium nitride (InGaN) samples with single heterojunction (SH) and double heterojunction (DH) were prepared using metal-organic chemical vapor deposition. SH has a layer of InGaN thin film (thicknesses, 25, 50, 100, and 200 nm) grown on an uGaN film (thickness, 2 μm). The DH samples are distinguished by DH uGaN film (thickness, 120 nm) grown on the InGaN layer. Reciprocal space mapping measurements reveal that the DH samples are fully strained with different thicknesses, whereas the strain in the SH samples are significantly relaxed with the increasing thickness of the InGaN film. Scanning electron microscopy results show that the surface roughness of the sample increases when the sample is relaxed. High-resolution transmission electron microscopy images of the structure of indium droplets in the DH sample indicate that the thickness of the InGaN layer decreases with the density of indium droplets. The formation of these droplets is attributed to the insufficient kinetic energy of indium atom to react with the elements of group V, resulting to aggregation. The gallium atoms in the GaN thin film will not be uniformly replaced by indium atoms; the InGaN thin film has an uneven distribution of indium atoms and the quality of the epitaxial layer is degraded.     

Synthesis of Indium Nanowires by Galvanic Displacement and Their Optical Properties

Single crystalline indium nanowires were prepared on Zn substrate which had been treated in concentrated sulphuric acid by galvanic displacement in the 0.002 mol L⁻¹ In₂(SO₄)₃-0.002 mol L⁻¹ SeO₂-0.02 mol L⁻¹ SDS-0.01 mol L⁻¹ citric acid aqueous solution. The typical diameter of indium nanowires is 30 nm and most of the nanowires are over 30 μm in length. XRD, HRTEM, SAED and structural simulation clearly demonstrate that indium nanowires are single-crystalline with the tetragonal structure, the growth direction of the nanowires is along [100] facet. The UV-Vis absorption spectra showed that indium nanowires display typical transverse resonance of SPR properties. The surfactant (SDS) and the pretreatment of Zn substrate play an important role in the growth process. The mechanism of indium nanowires growth is the synergic effect of treated Zn substrate (hard template) and SDS (soft template).     

Stable Hydrogen Production from Ethanol through Steam Reforming Reaction over Nickel-Containing Smectite-Derived Catalyst

Hydrogen production through steam reforming of ethanol was investigated with conventional supported nickel catalysts and a Ni-containing smectite-derived catalyst. The former is initially active, but significant catalyst deactivation occurs during the reaction due to carbon deposition. Side reactions of the decomposition of CO and CH₄ are the main reason for the catalyst deactivation, and these reactions can relatively be suppressed by the use of the Ni-containing smectite. The Ni-containing smectite-derived catalyst contains, after H₂ reduction, stable and active Ni nanocrystallites, and as a result, it shows a stable and high catalytic performance for the steam reforming of ethanol, producing H₂.     

Effect of carbon deposition over carbonaceous catalysts on CH<Subscript>4</Subscript> decomposition and CH<Subscript>4</Subscript>-CO<Subscript>2</Subscript> reforming

An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH₄-CO₂ reforming. Thermogravimetry (TG) and X-ray diffraction (XRD) were employed to study the characteristics of carbon deposition. It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH₄-CO₂ reforming. The trend of methane decomposition at lower temperatures is similar to that at higher temperatures. The methane conversion is high during the initial of stage of the reaction, and then decays to a relatively fixed value after about 30 min. With temperature increase, the methane decomposition rate increases quickly. The reaction temperature has significant influence on methane decomposition, whereas the carbon deposition does not affect methane decomposition significantly. Different types of carbon deposition were formed at different methane decomposition reaction temperatures. The carbon deposition Type I generated at 900°C has a minor effect on CH₄-CO₂ reforming and it easily reacts with carbon dioxide, but the carbon deposition Type II generated at 1000°C and 1100°C clearly inhibits CH₄-CO₂ reforming and it is difficult to react with carbon dioxide. The results of XRD showed that some graphite structures were found in carbon deposition Type II.     

Effect of carbon deposition over carbonaceous catalysts on CH4 decomposition and CH4-CO2 reforming

An investigation was made using a continuous fixed bed reactor to understand the influence of carbon deposition obtained under different conditions on CH₄-CO₂ reforming. Thermogravimetry (TG) and X-ray diffraction (XRD) were employed to study the characteristics of carbon deposition. It was found that the carbonaceous catalyst is an efficient catalyst in methane decomposition and CH₄-CO₂ reforming. The trend of methane decomposition at lower temperatures is similar to that at higher temperatures. The methane conversion is high during the initial of stage of the reaction, and then decays to a relatively fixed value after about 30 min. With temperature increase, the methane decomposition rate increases quickly. The reaction temperature has significant influence on methane decomposition, whereas the carbon deposition does not affect methane decomposition significantly. Different types of carbon deposition were formed at different methane decomposition reaction temperatures. The carbon deposition Type I generated at 900°C has a minor effect on CH₄-CO₂ reforming and it easily reacts with carbon dioxide, but the carbon deposition Type II generated at 1000°C and 1100°C clearly inhibits CH₄-CO₂ reforming and it is difficult to react with carbon dioxide. The results of XRD showed that some graphite structures were found in carbon deposition Type II.     

Stages in the catalyst-free InP nanowire growth on silicon (100) by metal organic chemical vapor deposition

Catalyst-free InP nanowires were grown on Si (100) substrates by low-pressure metal organic chemical vapor deposition. The different stages of nanowire growth were investigated. The scanning electron microscopy images showed that the density of the nanowires increased as the growth continued. Catalyzing indium droplets could still be fabricated in the nanowire growing process. X-ray diffraction showed that the nanowires grown at different stages were single crystalline with <111 > growth direction. The photoluminescence studies carried out at room temperature on InP nanowires reveal that the blueshift of photoluminescence decreased as the growing time accumulates, which is related to the increase in the diameter, rather than the length. Raman spectra for nanowires at different growing stages show that the quality of the nanowire changes. The growth of InP nanowires at different growing stages is demonstrated as a dynamic process.     

Stereospecific Indium(III)-Catalysed Tandem Cycloisomerization of Functionalized 1,6-enynes: Scope and Mechanistic Insights

Tandem cycloisomerization reactions of functionalized 1,6-enynes under indium(III) catalysis are described. This atom-economic transformation proceeds smoothly with 5-exo-dig regioselectivity using commercial In(III) halides and 1,6-enynes furnished with alcohol, carboxylic acid or amine functional groups to give bicyclic structures in good yields and diastereoselectivities. The reaction with enynals involves a three–step mechanism to give an oxatricycle and a conjugated 1,3-diene. In the absence of the internal nucleophile the enyne cycloisomerization evolves through a skeletal rearrangement or a cyclopropanation reaction after the regioselective 5-exo-dig cyclization. The 1,6-enyne cycloisomerization is stereospecific and the stereoselectivity appears to be independent of the internal nucleophile. Experimental data support a common reaction mechanism involving an initial alkyne electrophilic π-coordination of In(III) followed by Markovnikov electrophilic alkene addition and ring-closure by nucleophilic attack. DFT studies hold up a stepwise mechanism involving the formation of a chiral non-classical carbocation intermediate that determines the diastereoselectivity of this tandem cycloisomerization reaction.     

Improvement in performance of indium gallium oxide thin film transistor via oxygen mediated crystallization at a low temperature of 200 °C

We report the fabrication of high-performance polycrystalline indium gallium oxide (IGO) thin film transistors (TFTs) at a low temperature of 200 °C. Growth of a highly aligned cubic phase with a bixbyite structure was accelerated at a certain proportion of oxygen plasma density during deposition of the IGO thin film, which leads to outstanding electrical characteristics. The resulting polycrystalline IGO TFT exhibited a high field-effect mobility of 56.0 cm²/V, a threshold voltage (V_TH) of 0.10 V, a low subthreshold gate swing of 0.10 V/decade, and a current modulation ratio of >10⁸. Moreover, the crystalline IGO TFTs have highly stable behaviors with a small V_TH shift of +0.8 and ?1.0 V against a positive bias stress (V_GS,ST ?V_TH = 20 V) and negative bias illumination stress (V_GS,ST ?V_TH = ?20 V) for 3,600 s, which is attributed to the high quality of the bixbyite crystalline structure.     

Anodic photodissolution of n-InP, under electroless conditions

In the presence of α-SiMo₁₂O₄₀⁴⁻ ions dissolved in acidic solution and under laser irradiation, the electroless photoetching of n-type InP is achieved. At the laser impact, the semiconductor is oxidized while SiMo₁₂O₄₀⁴⁻ species are reduced. The shape of the pit formed, due to the photoanodic dissolution of the material, depends on the experimental conditions, notably on the presence or not of Cl⁻ ions in the medium. It can have either a Gaussian shape or a flat bottom. To specify the charge transfer which occurs at the n-InP/solution illuminated interface, some electrochemical studies were performed on n- and p-type InP electrodes. In fact, the reduction of SiMo₁₂O₄₀⁴⁻ ions occurs by capture of electrons from the InP conduction band. Considering the energetic situation at the InP/electrolyte interface and some electrochemical results, it is concluded that the electron transfer from InP to SiMo₁₂ is mediated by surface states. The influence of Cl⁻ ions on the n-InP photodissolution process is also discussed.