Indium Sites Research Articles

Molecular structure of the unusual tris(tribromoindate)methane anion, [HC(InBr3)3]3−

The title molecule, which is obtained as the tetraphenylphosphonium salt following the reaction of InBr and HCBr3, is shown to involve pseudo-tetrahedral carbon and indium(III) sites; it is a member of a series of related [H4–nC(InBr3)n]n– anions.

Effects of Tin Doping and Oxygen Vacancies on the Electronic States of Indium Oxide

The electronic states of indium oxide are calculated by a molecular orbital method. The conduction band consists mainly of oxygen 2p and indium 5p. The valence band consists of O-2p. When there is an oxygen vacancy in the indium oxide, a localized orbital appears at the indium site near the oxygen vacancy, which forms a vacancy level below the bottom of the conduction band. When there are many oxygen vacancies in the indium oxide, the vacancy level is unlocalized. When Sn atoms are substituted for In atoms, localized molecular orbitals of Sn-5p and O-2p appear at the high-energy part of the conduction band. On the other hand, when Sn atoms are inserted into interstitial positions, vacancy levels appear below the bottom of the conduction band. When there are many oxygen vacancies in both cases, the oxygen vacancy levels appear between the conduction band and the valence band. The complex formed by In, Sn and O forms the doping level.

Catalytic performance of indium-supported TiO2-ZrO2 for the selective reduction of nitrogen monoxide in the presence of oxygen

The catalytic activity of indium-supported TiO2- ZrO2 binary metal oxide for the selective reduction of NO with propene in the presence of oxygen was investigated. The supported indium caused a drastic enhancement of NO reduction activity of TiO2-ZrO2. It was suggested that the ``dispersed phase'' of indium oxide, which is reduced at lower temperature in temperature-programmed reduction (TPR), is responsible for the high activity. Propene served as the most efficient reducing agent, while oxygenated hydrocarbons were not good ones. A reaction mechanism was proposed that N2 is formed through the reaction of propene and NO2, which was formed on the acid sites of TiO2-ZrO2, on the indium sites.

Properties of carbon-doped InGaAs grown by atmospheric pressure metalorganic chemical vapor deposition using CCl 4

This paper shows the results of a van der Pauw-Hall analysis of carbon-doped InGaAs epilayers grown by atmospheric pressure metalorganic chemical vapor deposition using CCl 4 gas. Heavily C-doped In x Ga 1 − x As ( x = 0 to 0.52) epilayers were obtained by varying the V III ratio from 1.3 to 32 and at a low growth temperature of 550°C, while keeping the flow rate of CCl 4 constant. For up to an InAs mole fraction of 0.43, a hole concentration of about 1.1 × 10 19 cm −3 was obtained. In the case of as-grown samples, a type conversion from p-type to n-type to n-type occurred at an InAs mole fraction of 0.48. This work also describes the effects of a rapid thermal annealing (RTA) on the electrical properties, particularly on a type conversion of InGaAs. After the RTA process at an annealing temperature of 750°C for 5 s, as-grown In 0.44Ga 0.56As with the p-type of 5.6 × 10 17 cm −3 was converted into the n-type of 3.9 × 10 17 cm −3. This can be attributed to the breaking of the CH or CH x bonds after the RTA process. The broken carbon atoms could enter into arsenic sites or indium (or gallium) sites in the epilayers. With increasing InAs mole fraction, more carbon atoms were supposed to enter into indium sites rather than arsenic sites, due to a lower binding energy of InC than that of AsC.

Nuclear magnetism of PrIn3

The specific heat of Van Vleck paramagnet PrIn3 has been measured in the temperature range between 0.07 mK and 10 mK. The crystal structure is a cubic Cu3Au type. Praseodymium(Pr) site has a cubic symmetry but Indium(In) site has no cubic symmetry. The specific heat result shows two anomalies. One is a broad anomaly which can be well-explained by a Schottky specific heat of the nuclear quadrupole interaction of In. The obtained nuclear quadrupole coupling constant ishvq=+228 MHz and the sign is positive. The other is a sharp anomaly at 0.13mK. This anomaly indicates the magnetic ordering of Pr in the nuclear regime. This ordering temperature is the lowest among the transition temperatures of the Van Vleck paramagnets.

Selective catalytic reduction of nitrogen monoxide by methane on zeolite catalysts in an oxygen-rich atmosphere

Selective reduction of NO by CH 4 on zeolite catalysts has been studied. After an investigation of the catalytic features of various cation-exchanged zeolites, we found that Ga-ZSM-5 and In-ZSM-5 were highly active and selective for NO reduction by CH 4. We also showed that this reaction was moderately promoted even by H-form ZSM-5, mordenite, and ferrierite. From the catalytic performance of Ga-and In-ZSM-5 in NO-CH 4-O 2, NO 2-CH 4-O 2, and NO-O 2 reactions, it is concluded that the selective reduction of NO on these catalysts proceeds in two stages: (1) NO is oxidized to NO 2 on zeolite acid sites, (2) NO 2 and CH 4 react on gallium or indium sites. The highly selective features of Ga and In in the zeolite for the NO 2-CH 4 reaction seem to be attributed to the coordinatively unsaturated nature of these sites which adsorb both of these reactants on the same site. Effect of water vapor on NO conversion was also investigated. It was found that Ga-ZSM-5 was strongly inhibited by steam, while In-ZSM-5 was fairly active even in the presence of 10% steam.

Electron Spin Resonance Study of CuInSe2 Single Crystals

Imperfections relating to iron contamination in undoped CuInSe2 single crystals have been studied using Electron Spin Resonance at liquid He temperature. A fine structure of the S=5/2 state attributed to Fe3+ has been observed for crystals of Cu/In ∼ 1. On the other hand, some of indium-rich (Cu/In<1) crystals show a single line of geff∼10. Fe2+ is one of the possible candidates for this line. The two different ionization states of iron in CuInSe2 suggest that iron atoms substitute copper sites in Cu-deficient system rather than indium sites which are preferably occupied by Fe3+ in nearly stoichiometric system.

Structural Study of Tin‐Doped Indium Oxide Thin Films Using X‐Ray Absorption Spectroscopy and X‐Ray Diffraction: II . Tin Environment

Thin films of tin‐doped (ITO for indium tin oxide) with different tin contents produced by a powder pyrolysis technique have been investigated by x‐ray absorption spectroscopy and x‐ray diffraction. In a previous paper, an extended x‐ray absorption fine structure (EXAFS) study at the indium K‐edge and diffraction measurements were presented. From the EXAFS investigations at the indium edge, it has been shown that the indium atomic environment becomes disordered during the doping process. In the present work, the EXAFS results at the tin K‐edge and x‐ray diffraction data are discussed. Both methods show that the tin solubility in the film is higher than in the powder form of ITO. The EXAFS study confirms that the tin atoms are located at indium sites as inferred from the electrical properties of ITO. Also observed is a relaxation of the first oxygen polyhedron around the dopant atoms that increases with the tin content. The disorder of the host network and of the tin metallic environment is clearly related to the changes observed in the Sn‐O shell.

Structural Study of Tin‐Doped Indium Oxide Thin Films Using X‐Ray Absorption Spectroscopy and X‐Ray Diffraction: I . Description of the Indium Site

Thin films of tin‐doped , with different tin contents produced by a powder pyrolysis technique have been investigated by x‐ray absorption spectroscopy and x‐ray diffraction. At the indium K‐edge, extended x‐ray absorption fine structure (EXAFS) investigations reveal that the indium atomic environment is modified by the doping. Even at low tin concentrations, the first oxygen polyhedron and the metallic In‐In coordination shells are disordered. This disorder increases with increasing tin content, and, for a large tin content (39% Sn), the In‐O shell is locally similar to that of the hexagonal high pressure phase of , that is also known to be stabilized at atmospheric pressure by the insertion of small foreign cation (such as Sn4+) in the indium oxide structure. The x‐ray diffraction experiments also support the idea of a disordered network; the x‐ray reflections decrease in magnitude but remain sharp even for a high tin concentration. This indicates that the structural disorder observed by EXAFS only induces a damping of the x‐ray reflections (the network is still ordered within large domains). The following modifications of the host network were observed; an increase in the lattice parameter, a decrease in the size of coherence of the diffraction domains with increasing the tin content (from 1200 Å to 700 Å), and a <100> preferential orientation, which disappears for the high dopant concentrations.

Cavity formation at indium impurities in bcc metals

The defect formation in the bcc metals W and Mo above annealing stage III and the influence of rare gases on this process were investigated by means of the perturbed angular correlation technique using111In as radioactive probe. In both metals a relatively high electric field gradient (EFG) could be observed at the indium site, characterized by the quadrupole interaction frequencies υQ=263 MHz, ν=0 and υQ=220 MHz, ν≈0.15 for W and Mo, respectively. The observations are assigned to the growth of threedimensional vacancy clusters at the probe atoms with the indium atoms situated in the inner surface of this cavities, thus experiencing the corresponding surface EFG.

Effects of dopant concentration on the microstructure of tin- doped indium oxide thin films

To understand the electronic conduction mechanism in Sn-doped indium oxide thin films, it is important to study the effect of dopant atoms on the neighbouring indium oxide lattice. Ideally Sn is a substitutional dopant at random indium sites. The difference in valence (Sn4+ replaces In3+) requires that an extra electron is donated to the lattice and thus contributes to the free carrier density. But since Sn is an adjacent member of the same row in the periodic table, the difference in the ionic radius (In3+: 0.218 nm; Sn4+: 0.205 nm) will introduce a strain in the indium oxide lattice. Free carrier electron waves will no longer see a perfect periodic lattice and will be scattered, resulting in the reduction of free carrier mobility, which will lower the electrical conductivity (an undesirable effect in most applications).One of the main objectives of the present investigation is to understand the effects of the strain (produced by difference in the ionic radius) on the microstructure of the indium oxide lattice when the doping level is increased to give high carrier densities. Sn-doped indium oxide thin films were prepared with four different concentrations: 9, 10, 11 and 12 mol. % of SnO2 in the starting material. All the samples were prepared at an oxygen partial pressure of 0.067 Pa and a substrate temperature of 250°C using an Edwards 306 coating unit with an electron gun attachment for heating the crucible. These deposition conditions have been found to give optimum electrical properties in Sn-doped indium oxide films. A JEOL 2000EX transmission electron microscope was used to investigate the specimen microstructure.

An AES/XPS study of oxygen involved reactions on InSb

AbstractThe oxidation of ion‐etched InSb(110)‐cleavage planes was investigated by means of AES and XPS, respectively. Whereas the sticking coefficient of oxygen at indium sites was found to reach a saturation value after slight ion bombardment, the oxygen uptake rate of antimony remains low (sticking probability in the 10−7 range) with raising ion dose to a point where a drastical change in oxidation behaviour occurs at ion doses in the 10−2 As · cm−2 range. Then indium and antimony are nearly simultaneously oxidized with sticking coefficients of roughly 10−3. Cluster formation is discussed as one possible mechanism to explain the experimental findings. Adsorption experiments on disordered surfaces can contribute to a better understanding of surface reactions during gas phase growth of single crystals, since the in‐growth situation of the top layer of the latter is far away from the ideal situation that is prepared by in situ cleaving only.

The effect of pressure and temperature on the electric field gradient at111Cd on In sites in intermetallic In-Bi

The time-dependent perturbed angular correlation (TDPAC) technique was used to measure the electric field gradient (EFG) as a function of pressure for the compounds InBi, In2Bi and In5Bi3 and as a function of temperature for In5Bi3 111Cd as probe on the indium sites. It was possible to identify the phase transition induced by pressure in the compound In2Bi as a transformation to the structure of the compound In5Bi3 with defects. Estimates were made of the volume and the explicit temperature dependences of the EFG for the compounds In2Bi and In5Bi3. The high values of the volume dependence of the EFG obtained for In2Bi is comparable to the known values for pure metals. The importance of anharmonic effects in the EFG shows up for In5Bi3.

Influence of rare gases on cavity formation at indium impurities in copper.

The interaction of implanted gases such as He, Ne, Ar, Kr, and Xe with substitutional indium impurities in copper has been studied by the time-differential perturbed angular correlation technique. In spite of the very different size of the gas atoms, in all cases identical electric field gradients were observed at the indium site. It is shown that the gas implantation initiates the growth of large cavities at the indium impurity and the observed electric field gradient is due to indium atoms situated at the inner surface of the cavities. The influence of the gas atoms inside the cavities on the observed electric field gradient can be neglected.

Photoluminescence in polycrystalline CuInSe 2 solar cells

Photoluminescence (PL) data have been reported by several workers for both single-crystal and polycrystalline CuInSe 2, including actual solar cells. Careful comparison shows a substantial agreement among the PL transitions reported and a consistent defect energy level diagram. Correction is made for the electrostatic term in the PL transition energy, which can be quite large for polycrystalline material and which can be used to estimate defect densities. Plausible physical arguments are presented to identify the primary levels. The dominant donor proposed is the selenium vacancy, a double donor which would have ionization energies near 40 and 70 meV. The dominant acceptor proposed is copper on an indium site, also a double level with near-hydrogenic energies of 40 and 80 meV.

Anomalous diffusion of acceptors in InP

Diffusion or implantation of acceptors into InP substrates are important techniques for forming device junctions. Some recent studies of Be, Zn, Mg, Mn implants revealed anomalous post-annealed profiles with relatively flat tails and abrupt leading edges, especially in Fe-doped semi-insulating substrates. Such deep tails are detrimental for obtaining shallow p-n junctions. The experiments to be described were carried out using SIMS on two sets of InP samples: Be-implanted, Mn- or Zn-doped substrates; Zn-implanted n-ty InP substrates whose electron concentrations ( n ) varied from 5 × 10 15 to 2 × 10 18 e cm −3 . After anneal, the study of the correlations between the movement of the dopants in the substrates and the Be, Cr, Zn implants show that the flat tails and the abrupt leading edges depend strongly on: i) the presence and the concentrations of impurities, or dopants, located on indium sites; ii) the solubility of the p-type in-diffusing element; iii) the occupancy of the phosphorus sites by other substitutional elements, as sulphur for example.

Chromium absorption in InP

Absorption spectra of n-type InP:Cr samples consist mainly of two bands associated with two sets of zero-phonon lines (ZPL). The first band at about 0.8 eV and the associated ZPL around 0.756 eV are due to Cr2+ at an indium site. The second band has a zero-phonon structure around 0.886 eV which coincides exactly with the zero-phonon structure of the chromium-related luminescence in InP; it is shown that the nature of this transition is the same as that of the 1.03 eV transition in GaP:Cr, the origins of which are still not definitively established.

Optical properties and defect chemistry of p-CuInS 2

The absorption and photoconductivity spectra of p-CuInS 2 single crystals, grown by chemical vapour transport method, were obtained at 76 and 300 K. An acceptor level at about 150 meV, observed in as-grown and sulphur annealed samples of p-CuInS 2, has been attributed as due to copper atoms on indium sites. Also, a donor level at about 30 meV is observed, which could be identified with sulphur vacancies.

Structural investigation of indium halide compounds: Single crystal Raman study of monohydrated potassium hexachloroindate

The Raman spectrum of K 3InCl 6, H 2O single crystal is assigned on the basis of the crystal structure knowledge. The main feature is the splitting of the ν 1 vibrational band into two components, that are assigned in relation to the indium site occupation ratio. In Raman spectroscopy, the superposition of the internal mode frequency range (characteristic of different anionic species), does not contribute to any improvement of the ionic isomerisation found by X-ray investigation.

Pressure dependence of the electrical resistivity and the ionization energy of Cr In n-type InP

The electrical resistance of chromium-doped, n-type InP has been found to increase exponentially with hydrostatic pressure (up to 4.7 kbar) at 273 K, 301 K, and 344 K. The resistivity activation energy increases by 6.5 × 10 -6 eV/bar. This rate equals the difference between the pressure dependences of the lowest conduction band minimum at k = (000) and the <111> subsidiary minima determined by others. Our results indicate that pressure increases the ionization energy of a Cr donor level whose wave function has a large contribution from the <111> minima. It is suggested the Cr donor level is due to Cr +3 occupying an indium site.