Increasing Indium Content Research Articles

Synthesis, structure and optical properties of thin films from GeS2–In2S3 system deposited by thermal co-evaporation

This paper deals with the properties of the glasses and thin films from multi-component chalcogenide prepared by co-evaporation technique. The thin chalcogenide layers from GeS2–In2S3 system were deposited by thermal co-evaporation of GeS2 and In2S3. Using X-ray microanalysis it was found that the film compositions are closed to the expected ones. X-ray diffraction analysis shows that the thin films deposited by co-evaporation are amorphous. The refractive index, n and the optical band gap, Egopt were calculated from the transmittance and reflectance spectra. The thin film's structure was investigated by infrared spectroscopy. It was found that the photo-induced optical changes decrease with increase of indium content while significant thermo-induced changes in the optical properties and structure were observed at 14at.% indium. The infrared spectra demonstrated high transmittance of the thin films in the range 4000–500cm−1. The far-infrared spectra indicated that the indium participates in the glass network of the layers from Ge–S–In system in four coordinated InS4/2− tetrahedral and six-coordinated InS6/23− octahedral units. The changes in infrared spectra after annealing of the thin films evidence an increase of population of ethane-like S3Ge–GeS3 units and/or structural or phase change of indium contain units.

Structural and optoelectronic properties of indium doped SnO2 thin films deposited by sol gel technique

Indium doped tin oxide (SnO2:In) thin films were deposited on glass substrates by sol–gel dip coating technique. X-ray diffraction pattern of SnO2:In thin films annealed at 500 °C showed tetragonal phase with preferred orientation in T (110) plane. The grain size of tin oxide (SnO2) in SnO2:In thin films are found to be 6 nm which makes them suitable for gas sensing applications. AFM studies showed an inhibition of grain growth with increase in indium concentration. The rms roughness value of SnO2:In thin films are found to 1 % of film thickness which makes them suitable for optoelectronic applications. The film surface revealed a kurtosis values below 3 indicating relatively flat surface which make them favorable for the production of high-quality transparent conducting electrodes for organic light-emitting diodes and flexible displays. X-ray photoelectron spectroscopy gives Sn 3d, In 3d and O 1s spectra on SnO2:In thin film which revealed the presence of oxygen vacancies in the SnO2:In thin film. These SnO2:In films acquire n-type conductivity for 0–3 mol% indium doping concentration and p type for 5 and 7 mol% indium doping concentration in SnO2 films. An average transmittance of >80 % (in ultra-violet–Vis region) was observed for all the SnO2:In films he In doped SnO2 thin films demonstrated the tailoring of band gap values. Photoluminescence spectra of the films exhibited an increase in the emission intensity with increase in indium doping concentration which may be due structural defects or luminescent centers, such as nanocrystals and defects in the SnO2.

Atomistic simulations of InGaN/GaN random alloy quantum well LEDs

AbstractIn this work, a random distribution of Indium in a quantum well has been considered to study the effect on the energy gap of a GaN/InGaN/GaN LED device. Monte Carlo sampling technique has been used to generate hundreds of atomistic model structures of the device active region. In order to calculate pseudomorphic strain and internal deformations of the alloy, a multiscale method combining continuous media elasticity and atomistic valence force field models has been used. A multiphysic quantum/classical simulation coupling driftdiffusion with empirical tight‐binding in order to compute the electron and hole states of the system has been performed. The reliable sp3d5s* parametrization has been used in the calculations of the eigenstates. We have found an energy gap difference of 50.9 meV for x (In) = 0.1 molar fraction between using virtual crystal approximation and a random distribution of In which increase with increasing Indium concentration. Moreover, electrons wave function seems to be more sensitive than holes due to Indium fluctuations

Atmospheric Spatial Atomic Layer Deposition of In-Doped ZnO

Indium-doped zinc oxide (ZnO:In) has been grown by spatial atomic layer deposition at atmospheric pressure (spatial-ALD). Trimethyl indium (TMIn), diethyl zinc (DEZ) and deionized water have been used as In, Zn and O precursor, respectively. The metal content of the films is controlled in the range from In/[In+Zn] = 0 to 23% by co-injecting the vaporized metal precursors (i.e. DEZ and TMIn) in the deposition region and varying their flows. A high doping efficiency (up to 95%) is achieved, resulting in films with very high carrier density (6·1020 cm−3), low resistivity (3 mΩ·cm) and high transparency in the visible range (> 85%). The morphology of the films changes from polycrystalline to amorphous with increasing indium content above 15%, while maintaining a low resistivity value (< 7 mΩ·cm). Spatial-ALD combines a fine tuning of the composition, morphology and electrical properties of ZnO:In films with high deposition rates (> 0.1 nm/s).

Growth and physical characterization of AgGa1−xInxSe2 (x=0.5) single crystals grown by modified vertical Bridgman method

AgGa1−xInxSe2 (x=0.5) polycrystalline material was successfully synthesised from high purity elements by the melt and temperature oscillation method. Large size and crack-free AgGa0.5In0.5Se2 single crystals were grown using a double wall quartz ampoule with accelerated crucible rotation technique (ACRT) by modified vertical Bridgman method. The unit cell parameters were confirmed by single crystal X-ray diffraction analysis. The composition of AgGa0.5In0.5Se2 was measured using energy dispersive spectrometry (EDS). The insignificant change in atomic percentages of Ag, Ga, In and Se along the ingot further reveals that the composition throughout its length is fairly homogeneous. The transmittance spectra of AgGa0.5In0.5Se2 single crystal was achieved in the NIR region and high transmittance of the crystals in the mid-IR region was revealed. The absorption edge of the material is near 881nm and the optical band gap energy is 1.4eV. Thermal property of AgGa0.5In0.5Se2 has been studied using Differential scanning calorimetry (DSC) technique and it confirms that the increase in Indium content reduces the super-cooling temperature. Electrical property is measured using Hall Effect measurements and it confirms the n-type semiconducting nature.

The Preparation of In&lt;sub&gt;x&lt;/sub&gt;Bi&lt;sub&gt;1-x&lt;/sub&gt;VO&lt;sub&gt;4 &lt;/sub&gt;Photocatalyst Particles and their Photocatalytic Activity

InxBi1-xVO4 photocatalyst particles were prepared by low temperature solid reaction using nitrate of indium and bismuth and NH4VO4 as the starting materials, and followed by the sintering at various temperatures. The as-prepared samples were investigated by X-ray powder diffraction (XRD), and the photocatalytic activity was carried out by the concentration change of methylene blue in the solution after visible light irradiation. The experiment results show that the orthorhombic phase InVO4 is dominant in the photocatalyst samples prepared at sintering temperature higher than 600°C. In addition, the increase in indium content in the InxBi1-xVO4 particle has greatly improved the photocatalytic activity for decomposition of aqueous methylene blue under visible light irradiation.

Effect of trivalent dopants on local coordination and electronic structure in crystalline and amorphous ZnO

Density functional theory calculations are used to investigate the structure and binding energies of clusters formed between oxygen vacancies and trivalent dopant atoms (indium, gallium and aluminium) substituted into zinc oxide. Our results show that indium atoms form stable nearest neighbour pairs with oxygen vacancies, while gallium and aluminium atoms associate with them at next nearest neighbour sites. Using a combination of classical molecular dynamics and reverse Monte Carlo methods, models of amorphous indium zinc oxide at different compositions up to 25at.% indium are created. Analysis of these models indicates that, in contrast with the trend observed in the crystal phase, indium does not tend to be undercoordinated in the amorphous phase. The value of the band gap obtained for the amorphous compositions is smaller than that of crystalline undoped ZnO by about 0.8eV and is largely independent of the indium concentration. Electron-effective masses calculated in all the amorphous models decrease with increasing amount of indium due to the larger dispersion of the In-dominated conduction bands. This trend is compared to resistivity measurements on amorphous indium zinc oxide, which also decrease with increasing indium concentration.

Energy offset between valence band anti-crossing and optical polarization switching in semipolar InGaN quantum wells

Light emitted from a semipolar InGaN quantum well parallel to the surface normal is partially polarized, in contrast to the unpolarized emission of c-plane quantum wells. Anti-crossing of the two topmost valence bands causes polarization switching between ordinary and extraordinary polarizations for certain semipolar quantum well orientations with increasing indium content. Two properties of the two measured spectra, their polarization resolved but spectrally integrated intensity and their measured energy splitting, are associated with anti-crossing. Here, we show that only the observable energy splitting coincides with band anti-crossing, while the switching point of the polarization can deviate from the anti-crossing point.

Thermal (Kapitza) resistance of interfaces in compositional dependent ZnO-In2O3 superlattices

Compositionally dependent superlattices, In2O3(ZnO)k, form in the ZnO-rich portion of the ZnO-In2O3 phase diagram, decreasing thermal conductivity and altering both the electron conductivity and Seebeck coefficient over a wide range of composition and temperature. With increasing indium concentration, isolated point defects first form in ZnO and then superlattice structures with decreasing interface spacing evolve. By fitting the temperature and indium concentration dependence of the thermal conductivity to the Klemens-Callaway model, incorporating interface scattering and accounting for conductivity anisotropy, the Kapitza resistance due to the superlattice interfaces is found to be 5.0 ± 0.6 × 10−10 m2K/W. This finding suggests that selecting oxides with a compositionally dependent superlattice structure can be a viable approach, unaffected by grain growth, to maintaining low thermal conductivity at high temperatures.

Structural order and anomaly of liquid gallium–indium during isothermal dissolution of indium in liquid gallium

The behaviour of the excess entropy of the isothermal dissolution of indium in liquid gallium is examined in this article. We show the presence of a structural anomaly using the pair distribution function and excess entropy analysis when particles move from a far distance to the first coordination shell with increasing indium content, indicating that the structural anomaly depends only on what happens up to the local shell. These findings are in agreement with results of earlier studies. Moreover, the translational order parameter is introduced to quantify the disorder in liquid gallium–indium. The order mapped together with the two-body excess entropy shows that with an increase in indium content, the ‘true’ liquid changes to the liquid containing solid-like clusters.

Spatially resolved investigation of strain and composition variations in (In,Ga)N/GaN epilayers

The strain state and composition of a 400 nm thick (In,Ga)N layer grown by metal-organic chemical vapor deposition on a GaN template are investigated by spatially integrated x-ray diffraction and cathodoluminescence (CL) spectroscopy as well as by spatially resolved CL and energy dispersive x-ray analysis. The CL investigations confirm a process of strain relaxation accompanied by an increasing indium content toward the surface of the (In,Ga)N layer, which is known as the compositional pulling effect. Moreover, we identify the strained bottom, unstrained top, and gradually relaxed intermediate region of the (In,Ga)N layer. In addition to an increase of the indium content along the growth direction, the strain relaxation leads to an enhancement of the lateral variations of the indium distribution toward the surface.

Influence of In doping on the structure, stability and electrical conduction behavior of Ba(Ce,Ti)O3 solid solution

Pure perovskite structured proton conductive BaCe0.95−xInxTi0.05O3−δ (x=0.1, 0.2, 0.3, 0.4) powders were prepared by a modified Pechini method. The influences of indium doping on the performance of Ba(Ce,Ti)O3 solid solution, especially on the chemical stability and electrical conductivity were systematically investigated. With the increase of indium concentration, the chemical stability against the atmosphere containing CO2 and H2O (94%N2+3%CO2+3%H2O) was gradually enhanced. At the In doping level of 0.3 and 0.4, almost no any phase change is found in the powders at 700°C after 80–100h treatment, which is comparable to the widely-recognized BaCe0.4Zr0.4Y0.2O3−δ proton conductor. The specimen with the In content of 0.3 displayed the highest conductivity under all the atmospheres studied. Comparison between BaCe0.65In0.3Ti0.05O3−δ and BaCe0.4Zr0.4Y0.2O3−δ on the basis of electrochemical impedance spectroscopy analysis further demonstrated that the Ba(Ce,Ti)O3 solid solution containing proper indium content is more conductive and also a potential proton conductor to be used as electrolytes for solid oxide fuel cells.

Investigation of the light emission properties and carrier dynamics in dual-wavelength InGaN/GaN multiple-quantum well light emitting diodes

Three dual-wavelength InGaN/GaN multiple quantum well (MQW) light emitting diodes (LEDs) with increasing indium content are grown by metal-organic chemical vapor deposition, which contain six periods of low-In-content MQWs and two periods of high-In-content MQWs. For the low-In-content MQWs of three studied samples, their internal quantum efficiency (IQE) shows a rising trend as the emission wavelength increases from 406 nm to 430 nm due to the suppression of carriers escape from the wells to the barriers. However, for the high-In-content MQWs, the sample IQE falls rapidly with a further increase of emission wavelength from 496 nm to 575 nm. Theoretical calculation reveals that the electron-hole wave function overlap in the high-In-content MQWs is reduced because of an increase in the internal polarization field as indium content is increased. In addition, time-resolved photoluminescence decay curves show that the carriers generated in the low-In-content MQWs can be effectively transferred to the high-In-content part through the reabsorption process. However, the transfer time gradually becomes longer as emission wavelength increases, which means a reduction of carrier transfer rate between the different indium content MQWs. Furthermore, nonradiative recombination is enhanced in the high-In-content MQWs with longer emission wavelength due to the decline of crystal quality. Therefore, the fast drop of IQE for high-In-content MQWs can be attributed to the increase of the internal polarization field, the decrease of carrier transfer efficiency, and the enhanced nonradiative recombination. This research has a certain guiding value for an understanding of the recombination mechanism in the InGaN/GaN MQWs and for achieving high quality multiple-wavelength LEDs with better performance.

Room-temperature heteroepitaxy of single-phase Al1 − xInxN films with full composition range on isostructural wurtzite templates

Al1−xInxN heteroepitaxial layers covering the full composition range have been realized by magnetron sputter epitaxy on basal-plane AlN, GaN, and ZnO templates at room temperature (RT). Both Al1−xInxN single layers and multilayers grown on these isostructural templates show single phase, single crystal wurtzite structure. Even at large lattice mismatch between the film and the template, for instance InN/AlN (~13% mismatch), heteroepitaxy is achieved. However, RT-grown Al1−xInxN films directly deposited on non-isostructural c-plane sapphire substrate exhibit a polycrystalline structure for all compositions, suggesting that substrate surface structure is important for guiding the initial nucleation. Degradation of Al1−xInxN structural quality with increasing indium content is attributed to the formation of more point- and structural defects. The defects result in a prominent hydrostatic tensile stress component, in addition to the biaxial stress component introduced by lattice mismatch, in all RT-grown Al1−xInxN films. These effects are reflected in the measured in-plane and out-of-plane strains. The effect of hydrostatic stress is negligible compared to the effects of lattice mismatch in high-temperature grown AlN layers thanks to their low amount of defects. We found that Vegard’s rule is applicable to determine x in the RT-grown Al1−xInxN epilayers if the lattice constants of RT-sputtered AlN and InN films are used instead of those of the strain-free bulk materials.

Effect of ternary mixed crystals on interface optical phonons in wurtizte InxGa1−xN/GaN quantum wells

The effect of ternary mixed crystals on the interface optical phonons in wurtizte InxGa1−xN/GaN quantum wells is studied based on the modified random-element isodisplacement model and dielectric continuum model. The results show that the interface optical phonons appear different frequency range with different indium concentration. The frequencies of interface optical phonons in the high frequency range decrease almost linearly with increasing indium concentration and do not vary almost linearly in the low frequency range. The indium concentration has more important effect on the electron-phonon interaction in low frequency range.

Thermodynamic and electrochemical hydrogenation properties of LaNi5 − xInx alloys

Abstract Hydrogenation properties of LaNi 5 − x In x alloys ( x = 0.1, 0.2 and 0.5) were examined by their direct reaction with gaseous hydrogen and by cathodic charging in 6 M KOH solution. The gas phase measurements were carried out using Sievert's type apparatus in 300–400 K temperature range and at hydrogen pressures up to 40 bars. Indium substitution for Ni in LaNi 5 significantly modifies the hydrogenation behavior, decreasing the equilibrium pressure of hydrogen and limiting the hydrogen capacity as compared to LaNi 5 . The LaNi 4.9 In 0.1 revealed a distinct presence of two pressure plateaus on the high temperature isotherms. Apart from the α -phase (hydrogen solid solution) and β -phase (LaNi 5 H 6 hydride), formation of a new σ* -hydride phase was postulated at the hydrogen content extended over the region of H/f.u. = 1.3–1.8. Thermodynamic functions: enthalpy and entropy of the hydrogen absorption process were calculated from the H 2 -pressure/composition ( p–c ) isotherms at several temperatures, applying the Van't Hoff's (ln p − 1/ T ) dependence. Electrochemical galvanostatic hydrogenation experiments at 185 mA/g charge/discharge rate revealed the greatest discharge current capacity of 319 mAh/g for LaNi 4.9 In 0.1 alloy after 4–5 cycles. The hydrogen discharge capacities decrease with further increase of indium content in the alloy.

Phase separations in graded-indium content InGaN/GaN multiple quantum wells and its function to high quantum efficiency

Phase separations have been studied for graded-indium content InxGa1−xN/GaN multiple quantum wells (MQWs) with different indium contents by means of photoluminescence (PL), cathodeluminescence (CL) and time-resolved PL (TRPL) techniques. Besides the main emission peaks, all samples show another 2 peaks at the high and low energy parts of the main peaks in PL when excited at 10 K. CL images show a clear contrast for 3 samples, which indicates an increasing phase separation with increasing indium content. TRPL spectra at 15 K of the main emissions show an increasing delay of rising time with indium content, which means a carrier transferring from low indium content structures to high indium content structures.

Effect of indium additive on thermal transport properties of Se–Te–Cd multi-component chalcogenide glasses

Abstract The thermal conductivity, thermal diffusivity and specific heat per unit volume of twin pellets of Se75Te15–xCd10Inx (x = 0, 5, 10 and 15) glasses, were carried out at room temperature by transient plane source technique. Results indicated that both values of thermal conductivity (λ) and thermal diffusivity (χ) are varied with In (indium) content and highest for 5 at.% of In, whereas the specific heat per unit volume is almost constant with increase of indium concentration. This shows that Se75Te10Cd10In5 glass can be considered as a critical composition at which the alloy becomes chemically ordered and most thermally stable than other compositions. This compositional dependence behaviour of thermal conductivity and thermal diffusivity can explained in terms of iono-covalent type bond which In makes with Se and Te as it is incorporated in Se–Te–Cd glasses.

Large optical polarization anisotropy due to anisotropic in-plane strain in m-plane GaInN quantum well structures grown on m-plane 6H-SiC

We investigated the optical polarization anisotropy of m-plane GaInN/GaN quantum well structures on m-plane SiC and bulk GaN substrates. On bulk GaN, the degree of polarization increases with increasing indium content according to the larger strain-induced separation of the topmost valence bands. On m-plane SiC, however, we observe constantly large polarization ratios of around 90% and more. From an x-ray strain state analysis and calculations of the valence band energies, we find that an anisotropic strain of the GaN buffer layer leads to a very strong separation of the topmost valence bands resulting in a large degree of polarization.

First principle study of the elastic properties of InGaAs with different doping concentrations of indium

The electronic structure and elastic properties of the InGaAs crystal with different doping concentrations of indium are studied by the plane-wave pseudopotential method based on density functional theory with Cambridge Serial Total Energy Package programme. The density of states and the elastic constants of the InGaAs crystal with different doping concentrations of indium are obtained. The elastic modulus is also calculated from the theoretical elastic constants by Voigt–Reuss–Hill averaging scheme. The band gaps of the InGaAs crystal decrease monotonically with increasing indium concentration. Similarly, the elastic constants of the InGaAs crystal with the symmetry of cubic crystal system decrease monotonically with increasing indium concentration. With increasing indium concentration, the brittleness of the InGaAs crystal decreases and the ductility of the InGaAs crystal increases monotonically, resulting in the tangential deformation of the supercells which is more prone to occur. The values of the elastic constants obtained will be helpful in analysing the elastic properties of InGaAs/GaAs semiconductor saturable absorber mirror and in guiding the application of InGaAs/GaAs as a saturable absorber in passively Q-switched laser.