Indium Substrate Research Articles

Optical properties of chromium-selenide films designed for terahertz applications

Herein the effects of indium substrates on the properties of chromium selenide thin films are reported. Chromium selenide thin films and indium substrates are prepared by the thermal evaporation technique under a vacuum pressure of 10−5 mbar. It is observed that indium sublayers alters the atomic stoichiometry of chromium selenide. It induces the formation of Cr2Se3 phase instead of CrSe2 phase which grow onto glass substrates. Both of the glass/CrSe2 and In/Cr2Se3 films displayed direct and indirect energy band gaps. The respective gaps are 2.60 eV and 3.19 eV and 2.25 eV and 2.83 eV. The Urbach tails states exhibited a width of 2.24 eV in glass/CrSe2 and showed value of 0.85 eV in In/Cr2Se3. In addition a light absorbability enhancement of more than 45% is reached at the In/Cr2Se3 interfaces in the visible range of light. Moreover, as terahertz resonators, In/Cr2Se3 films showed larger optical conductivity. It also displayed a spectral terahertz cutoff frequency in the range of 3.0–35 THz. Furthermore, when utilized as terahertz resonators, In/Cr2Se3 films demonstrate heightened optical conductivity and a spectral terahertz cutoff frequency ranging from 3.0 to 35 THz. Analyzing these terahertz oscillators using Drude-Lorentz models reveals that the density of free charge carriers increases with higher oscillator energy, while the drift mobility of these carriers within the terahertz resonators varies between 1.10 and 3.09 cm²/Vs. The array of features showcased by In/Cr2Se3 thin films, including their performance as terahertz resonators, positions them as strong contenders for applications in optical and terahertz technologies.

Optical and electrical dynamics at the In/CuSe interfaces

Herein, thin films of copper selenide are coated onto glass and 150 nm thick transparent indium substrates. The effect of indium substrates on the structural, morphological, compositional, optical, dielectric and electrical properties of CuSe are explored. Replacement of glass by indium, increased the crystallite and grain sizes, decreased the micro-strains, the stacking faults, the stress and the defect densities. Remarkable change in the shape of grains from wire like to rectangular shaped is forced by indium. Indium substrates also caused shrinkage in the energy band gap, enhanced the light absorbability and increased the dielectric constant values. The Drude-Lorentz analyses on the dielectric spectra have shown that the replacement of glass by indium increases the optical conductivity, increases the scattering time constant at femtosecond level and widens the range of plasma frequencies. On the other hand, dynamical electrical measurements which were carried out for In/CuSe/In devices, reveal the ability of using CuSe active media for fabrication of negative capacitance thin film transistors. Hopping conduction of charged particles over correlated barriers of height of 0.26 eV is dominant in the In/CuSe/In devices. The impedance spectroscopy analyses have shown that CuSe films can be used as bandstop filter appropriate for 5 G technologies.

Determination of Metallic Impurities in Carbon Nanotubes by Glow Discharge Mass Spectrometry.

A method for the rapid assessment of metallic impurities in carbon nanotubes (CNTs) by pin-cell source geometry glow discharge mass spectrometry (GDMS) is presented. Pins were prepared by pressing CNT powder onto an indium substrate. GDMS analysis was performed using high-carbon-content nanotube and coal-certified reference materials for calibration purposes. This approach enables the calibrated measurement of 41 elemental impurities in CNTs. The method was validated by the analysis of NIST SRM 2483 single-wall CNTs (raw soot) with good agreement with the certified values. The proposed measurement approach could also be applied not only for CNTs but also for the assessment of precursor materials used in the synthesis of CNTs and for quality control during the entire manufacturing process. The ability to assess the presence of all metallic impurities in a simple, reliable, high-throughput manner will allow the industry to real-time monitor any changes in the product process, access its toxicity, and environmental impact. As sample preparation is maintained to a minimum, this allows the determination of metallic impurities at concentration levels that are usually not attainable by most techniques.

PHOTODIODE BASED ON THE EPITAXIAL PHOSPHIDE GALLIUM WITH INCREASED SENSITIVITY AT A WAVELENGTH OF 254 nm

The paper shows the results of the development of a photodiode technology based on gallium phosphide structure n+-n-GaP-Au with high sensitivity. It provides the ion etching of the surface of the gallium phosphide before an application of a leading electrode of gold. The barrier layer of a 20 nm thick gold is applied to the substrate in the magnetic field of GaP. When forming the contact with the reverse side of the indium substrate at 600°C, there occurs the annealing of the gold barrier layer. At the maximum of the spectral characteristics obtained by the photodiode, it has a sensitivity of 0.13 A/W, and at a wavelength of 254 nm – about 0.06 A/W. The dynamic range of the photodiode is not less than 107.

Hydration of magnesia cubes: a helium ion microscopy study.

Physisorbed water originating from exposure to the ambient can have a strong impact on the structure and chemistry of oxide nanomaterials. The effect can be particularly pronounced when these oxides are in physical contact with a solid substrate such as the ones used for immobilization to perform electron or ion microscopy imaging. We used helium ion microscopy (HIM) and investigated morphological changes of vapor-phase-grown MgO cubes after vacuum annealing and pressing into foils of soft and high purity indium. The indium foils were either used as obtained or, for reference, subjected to vacuum drying. After four days of storage in the vacuum chamber of the microscope and at a base pressure of p < 10−7 mbar, we observed on these cubic particles the attack of residual physisorbed water molecules from the indium substrate. As a result, thin magnesium hydroxide layers spontaneously grew, giving rise to characteristic volume expansion effects, which depended on the size of the particles. Rounding of the originally sharp cube edges leads to a significant loss of the morphological definition specific to the MgO cubes. Comparison of different regions within one sample before and after exposure to liquid water reveals different transformation processes, such as the formation of Mg(OH)2 shells that act as diffusion barriers for MgO dissolution or the evolution of brucite nanosheets organized in characteristic flower-like microstructures. The findings underline the significant metastability of nanomaterials under both ambient and high-vacuum conditions and show the dramatic effect of ubiquitous water films during storage and characterization of oxide nanomaterials.

Effect of Microtextured Surface Topography on the Wetting Behavior of Eutectic Gallium–Indium Alloys

Liquid-embedded elastomer electronics have recently attracted much attention as key elements of highly deformable and "soft" electromechanical systems. Many of these fluid-elastomer composites utilize liquid metal alloys because of their high conductivities and inherent compliance. Understanding how these alloys interface with surfaces of various composition and texture is critical to the development of parallel processing technology, which is needed to create more complex and low-cost systems. In this work, we explore the wetting behaviors between droplets of gallium-indium alloys and thin metal films, with an emphasis on tin and indium substrates. We find that metallic droplets reactively wet thin metal foils, but the wettability of the foils may be tuned by the surface texture (produced by sputtering). The effects of both composition and texture of the substrate on wetting dynamics are quantified by measuring contact angle and droplet contact diameter as a function of time. Finally, we apply the Cassie-Baxter model to the sputtered and native substrates to gain insight into the behavior of liquid metals and the role of the oxide formation during interfacial processes.

SIMS depth profile analysis of particles collected in an urban environment

AbstractAnalytical procedures of collection and sample preparation of micro‐ and nanoparticles from urban environment as well as results of analyses are presented. Particulate matter is collected from indoor and outdoor urban air by several methods using mechanical collectors: personal cascade impactor and quartz filters. The other method treats human organisms as collectors: the method is based on induced sputum. Elemental analysis of the collected material performed by spark‐source mass spectrometry (SSMS) on magnetic sector JEOL JMS‐1BM2 mass analyzer, gives concentration of over 20 elements with ppb sensitivity. SIMS depth profile analysis is performed on SAJW‐05 apparatus with quadrupole QMA‐410 analyzer and Physical Electronics ion gun. Indium substrate covered with particulate matter is scanned with 100 µm diameter 5 keV Ar+ ion beam. Particles collected by cascade impactor were deposited at indium substrates. Four aerodynamic diameter classes were analyzed, i.e. 10–2.5 µm, 2.5–1 µm, 1–0.5 µm and 0.5–0.25 µm. Depth profile analysis was performed up to 100 nm depth of eroded material. Results were obtained on sets of particles, and the measured secondary ion currents gave integral values of the analyzed material. Assuming average surface composition of the analyzed particles some hints on the compositional morphology of the type of ‘core‐shell’ are extracted. Obtained data on the bulk elemental composition and SIMS depth profile results show the dependence on the grain size. Copyright © 2010 John Wiley &amp; Sons, Ltd.

Effects of substrate surfaces in matrix‐assisted laser desorption/ionization mass spectrometry

For matrix-assisted laser desorption/ionization (MALDI) mass spectra, undesirable ion contamination can occur due to the direct laser excitation of substrate materials (i.e., laser desorption/ionization (LDI)) if the samples do not completely cover the substrate surfaces. In this study, comparison is made of LDI processes on substrates of indium and silver, which easily emit their own ions upon laser irradiation, and conventional materials, stainless steel and gold. A simultaneous decrease of ion intensities with the number of laser pulses is observed as a common feature. By the application of an indium substrate to the MALDI mass spectrometry of alkali salts and alkylammonium salts mixed with matrices, 2,5-dihydroxybenzoic acid (DHB) or N-(4-methoxybenzylidene)-4-butylaniline (MBBA), the mixing of LDI processes can be detected by the presence of indium ions in the mass spectra. This method has also been found to be useful for investigating the intrinsic properties of the MALDI matrices: DHB samples show an increase in the abundance of fragment ions of matrix molecules and cesium ions with the number of laser pulses irradiating the same sample spot; MBBA samples reveal a decrease in the level of background noise with an increase in the thickness of the sample layer.

In Situ Growth of Self-Assembled and Single In2O3 Nanosheets on the Surface of Indium Grains

Self-assembled In2O3 nanosheet networks and flowerlike nanoarchitectures, as well as single In2O3 nanosheets, have been grown in situ on indium substrate by heating indium grains at 900−950 °C under the flow of O2 in the presence of a small quantity of P2O5. The as-synthesized In2O3 nanosheets were characterized by transmission electron microscopy, scanning electron microscopy, and Raman spectrum. It was found that the In2O3 nanosheets were single crystals with body-centered cubic structure and dimensions of about 0.5−3 μm. A possible mechanism for the In2O3 nanosheet growth was also proposed on the basis of the results of the present and previous works. This mechanism not only can explain all the experimental observations but also helps to clarify the growth mechanism of other nanostructures in the gas phase. A strong and narrow photoluminescent (PL) peak at 428 nm was observed from the nanosheets, which is attributed to radiative recombination between an electron on an oxygen vacancy and a hole on an indium−oxygen vacancy center in the In2O3 nanosheets.

Core–shell morphology of welding fume micro- and nanoparticles

Welding fume particles were analyzed using low energy ion erosion in secondary ion mass spectrometry. The particles were collected during the welding process of steel performed with three different techniques: electron beam welding (EBW), gas tungsten arc welding (GTAW) and shielded metal arc welding (SMAW). The first process was performed in vacuum while the two others in atmosphere. A 300–400nm diameter fraction of particles emitted in atmosphere was separated using a nine-stage impactor.Ion erosion of particles embedded in indium substrates was performed with 2keV, 100μm diameter, Ar+ ion beam at 45° ion incidence angle with respect to the substrate surface. The results show that all three types of particles have core–shell morphology. Particles formed in vacuum (EBW) have a shell enriched in oxygen, fluorine, chlorine, and potassium, with respect to the core composed mainly of iron, chromium and manganese. The GTAW particles are more oxidized than the EBW particles. Chlorine and fluorine dominate in the shell, however, their concentration in the core is higher than in the EBW particles. The SMAW particles are oxidized much more than two other types of particles. The shell is rich in chlorides, fluorides and potassium while the core is composed mainly of iron, chromium and manganese oxides.

SIMS depth profiling of working environment nanoparticles

Morphology of working environment nanoparticles was analyzed using sample rotation technique in secondary ion mass spectrometry (SIMS). The particles were collected with nine-stage vacuum impactor during gas tungsten arc welding (GTAW) process of stainless steel and shielded metal arc welding (SMAW) of mild steel. Ion erosion of 300–400 nm diameter nanoparticles attached to indium substrate was performed with 2 keV, 100 μm diameter, Ar + ion beam at 45° ion incidence and 1 rpm sample rotation. The results show that both types of particles have core-shell morphology. A layer of fluorine, chlorine and carbon containing compounds covers stainless steel welding fume particles. The cores of these particles are enriched in iron, manganese and chromium. Outer shell of mild steel welding fume particles is enriched in carbon, potassium, chlorine and fluorine, while the deeper layers of these nanoparticles are richer in main steel components.

New evidence of an organic layer on marine aerosols

An extraordinary episode of fine particles (diameter mainly &lt;2.5 μm) occurred in Helsinki, southern Finland, at the end of February 1998. The air masses came from the North Atlantic Ocean and passed over France, Germany, and southern Scandinavia. Particles were collected during the episode as well as before and after it. Uncoated particle samples were adhered to an indium substrate and were studied by a scanning electron microscope (SEM) coupled with an energy dispersive X‐ray microanalyzer (EDX). A great proportion of the particles behaved differently than aerosols previously studied by microscopic techniques. The particles (size mainly 0.5–1 μm) did not exhibit solid shape. They were “bubbling” or “pulsating” continually, enlarging in one part and shrinking in another. Some particles were broken down, especially when the beam of the electron microscope was focused on them. EDX analyses showed that the particles contained much carbon together with oxygen, sulfur, and sodium. Ion analyses by ion chromatography revealed high concentrations of sodium, sulfate, nitrate, and ammonium. The particles were identified as marine sea‐salt aerosols, which had accumulated anthropogenic emissions and lost chloride during their flow through continental polluted air. The shape fluctuations and the high carbon content observed by SEM/EDX led to the conclusion that the aerosols were enclosed by an organic membrane. Direct insertion probe/mass spectrometry investigations showed remarkable amounts of fragmented aliphatic hydrocarbons, which were considered as an evidence of a lipid membrane on the surface of the particles. The impact of the posited organic film on the properties of sea‐salt particles, as well as on Earth's climate, is discussed.

Thin oxide films on indium: impedance spectroscopy investigation of reductive decomposition

The kinetics of cathodic reduction of an In 2O 3 film grown on a bare indium substrate under dynamic conditions was studied by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) in borate buffer, pH 10. Reductive decomposition of In 2O 3 up to metallic In proceeds in the solid phase, via a solid-state mechanism: In 2 SO 3( s) + 2 H 2 O ( aq) + 6 e − ↔ 2 In ( s) + 6 OH − ( aq . Impedance spectra obtained between 40 mHz and 50 kHz, in the potential range of oxide film stability, its decomposition, new metal phase extraction and hydrogen evolution were interpreted on the basis of equivalent electrical circuits using a suitable fitting procedure. EIS has shown to be a valuable tool in the characterization of the solid/liquid interface: (i) the passive In 2O 3 film behaved as a simple dielectric, the interface of a passive electrode was blocking and in Bode and Nyquist plots a capacitive feature appeared; whereas (ii) in the vicinity of the In In 2O 3 redox potential a Warburg low-frequency feature was obtained, which was associated with diffusion processes in the solid phase as the rate-determining step; (iii) the interface of the freshly segregated metallic phase was a close-to-perfect RC feature, which was associated with charge transfer as the rds for the hydrogen evolution reaction on the bare metal surface. Cyclic voltammetry has revealed more details of the reduction processes giving further insight into the mechanism of reductive decomposition of In 2O 3 up to metallic In.

OEIC WDM transceiver modules for local access networks

The authors report measurements of fibre-optic transceiver modules which use a single optoelectronic integrated circuit (OEIC) subsystem. The optical circuit contains a DFB laser, 3 dB coupler, WDM, monitor photodiode and pin photodetector elements, which are monolithically integrated on a semi-insulating substrate indium phosphide chip. This assembly is designed to provide complete subscriber-termination functionality for bidirectional telephony and unidirectional broadband communication links for access networks. The dual-in-line module provides single fibre network interfacing, is physically compact, is stable for domestic and business environments, requires no cooling, and has the potential to be manufacturable at low cost.

Hexagonal Phase of Boron Nitride by AES

Auger electron spectra of the hexagonal phase of boron nitride are presented. The line shapes of the boron and nitrogen KLL transitions are characteristic for this phase of boron nitride. Therefore, hexagonal-boron nitride can be distinguished from other phases of boron nitride based on Auger line shapes. The powder specimen was prepared by burnishing onto an indium substrate.

Biological cryosection preparation and practical ion yield evaluation for ion microscopic analysis

A mounting method utilizing an indium substrate is described for preparing freeze-dried cryosections of biological tissue for ion microscopic analysis. Using this procedure, a qualitative comparison between cryosection, conventional chemical, and freeze-substitution specimen preparations is made with rat liver tissue. Practical ion yield variations in cryosections are found to be minimal (+/- 13% relative standard deviation) in tissue-containing areas of rat liver and small intestine.

Interface reactions of copper films with polycrystalline indium or antimony and single- crystal InSb substrates

The results of investigations of interface reactions of copper films with polycrystalline indium or antimony and with InSb single crystals are presented. The interface reactions were found to take place during r.f. sputtering of copper and led to the formation of the following compounds: CuIn and Cu 4In were formed with indium substrates, Cu 2Sb with antimony substrates and Cu 2Sb and CuIn with InSb substrates. No interface reactions were observed when copper was thermally evaporated onto antimony or InSb substrates.

ChemInform Abstract: REACTIONS OF CHLORINE WITH LIQUID METALS. 1. INDIUM

AbstractDie Reaktionen von Cl2 mit flüssigen und festen In‐Oberflächen werden mit Hilfe der modulierten Molekularstrahl‐Massenspektrometrie im Temp.‐Bereich 300‐650 K und Cl2‐Äquivalentdrücken zwischen 4·10‐6 und 4·10‐4Torr sowie AES untersucht.

Reactions of chlorine with liquid metals. 1. Indium

The reactions of molecular chlorine with liquid and solid indium surfaces were studied by modulated molecular beam-mass-spectrometric methods in the temperature range 300-650 K and equivalent chlorine pressures of 4 x 10/sup -6/ to 4 x 10/sup -4/ torr. In a separate chamber, the surface was monitored by AES as a function of temperature at an effective pressure of chlorine of 5 x 10/sup -4/ torr. At high temperatures InCl was the only reaction product, while at low temperatures some InCl/sub 2/ was observed. Near the melting point the behavior of the scattered Cl/sub 2/ signal suggested a drastic change in sticking probability from that on a bare indium surface to one characterizing a chloride-covered surface. The reaction probability and phase lag of the InCl product also showed rapid variations in a temperature range approximately 30/sup 0/C on either side of the melting point of the metal. A reaction model based on dissociative adsorption of chlorine was developed from the molecular beam and AES data. The model applies to both solid and liquid indium substrates and, in accord with the data, contains no discontinuity at the melting point.

The ’’cover up’’ of particles by substrate material during ion beam sputtering

The problems associated with the contamination of particle surfaces by the support material when ion sputtering is used as a method of depth profiling individual particles in an AES study are described. Initial observations indicated that if particles are mounted on an indium substrate, then after relatively short periods of argon ion beam sputtering the particle becomes completely obscured for Auger analysis by indium. The effects of varying different parameters: argon gas pressure, angle of both the ion beam and the analyzing electron beam, the morphology of the particle, and a selection of different metal substrates are reported. It is believed that the phenomenon is caused by a direct scattering process and not backscattering from the gas phase or surface migration. The conclusion is that even if highly refractory metals, e.g., tungsten, are used as the substrate, there is little that optimization of the different parameters described can do to reduce this very serious effect. These results bring into question the validity of undertaking such measurements unless the ion beam profile is reduced to dimensions below that of the particle being analyzed.