In-rich Phase Research Articles

Thermally stable radiative recombination centers within trench structures of red multi-quantum wells

High-Indium (In)-content multi-quantum wells (MQWs) are generally thermally unstable due to poor crystal quality resulting from low-temperature growth. In this study, red emission was achieved by modulating trench structures using dual-colour MQW structures. Impressively, the red MQWs inside deep trenches showed excellent thermal stability despite being grown at low temperatures. After high-temperature annealing at 950 °C for 30 min, the photoluminescence (PL) intensity of red MQWs exhibited a significant reduction of 91.9% outside trenches, while it dropped by only 9.3% inside trenches, as confirmed by confocal PL mapping. Transmission electron microscopy results show that massive In-rich phases and stacking faults appeared in the MQWs outside trenches after annealing. By contrast, the red MQWs inside deep trenches remained intact in lattice arrangement without being significantly damaged. The superior thermal stability of red MQWs inside deep trenches was mainly attributed to the low-defect-density epitaxy of InGaN layers in strain-relaxed states.

The effect of In-doping on the evolution of microstructure, magnetic properties, and corrosion resistance of NdFeB magnet

Abstract The grain boundary phase affects the magnetic properties and corrosion resistance of sintered NdFeB magnets. In this work, a small amount of Indium (In) was added to the NdFeB magnet by induction melting to systematically investigate its effect on the evolution of the microstructure, magnetic properties, and corrosion resistance of the NdFeB magnet. The microstructural analysis illustrated that minor In-addition generated more grain boundary phases and an abundant amorphous phase at the triple junction grain boundary. While the addition of In element failed to enhance the magnetic isolation effect between adjacent matrix grains, fortuitously, its incorporation elevated the electrochemical potential of the In-containing magnets. Besides, during corrosion, an In-rich precipitate phase formed, hindering the ingress of the corrosive medium into the magnet. Consequently, this significantly bolstered the corrosion resistance of sintered NdFeB magnets. The phase formation, magnetic properties, and corrosion resistance of In-doped NdFeB magnets are detailed in this work, which provides a new prospect for the preparation of high-performance sintered NdFeB magnets.

Decomposition in Mn50Ni40In10 melt-spun ribbons and its influence on magnetic properties

The phase stability, decomposition and its influence on the martensitic transformation and magnetic properties of magnetic shape memory alloy (MSMA) Mn50Ni40In10 melt-spun ribbons were investigated experimentally and theoretically. As-spun Mn50Ni40In10 was fine single Heusler phase with pronounced martensitic and magnetic transition below room temperature. However, in differential scanning calorimetry measurement an exothermic peak at 690 K and an endothermic peak at 765 K is observed during the heating of as-spun ribbons. The two peaks correspond to the growing of the punctiform precipitates in the grain interiors and the formation of a large amount of grain boundary segregation, respectively. After annealing at 870 K, the ribbon samples decompose into a cubic In-rich phase at grain boundaries and In-poor 7 M−modulate martensitic phase in the matrix. After annealing at 690 K and above, the martensitic transformation below room temperature is strongly weakened. Annealing temperature also has obvious influence on the 5 and 300 K saturation magnetization Ms of Mn50Ni40In10. Theoretical calculations on Mn2Ni1.5In0.5 (Mn50Ni37.5In12.5) give a negative formation energy (-0.11 eV/ f.u.) and a positive decomposition energy (0.22 eV/f.u.), indicating that this alloy can be metastable and tends to decompose into Mn2NiIn cubic phase and NiMn martensite, agreeing with the experimental results qualitatively.

Effect of in-situ Zn doping on suppression of phase separation in InxAl1−xAs epitaxial layer on InP(001) grown by MOCVD

The effect of Zn impurities on the surface morphology evolution and phase separation behavior of the InAlAs layer on InP(001) substrates is investigated using metal organic chemical vapor deposition (MOCVD). The phase separation of InAlAs occurs at a relatively low growth temperature (T < 620 °C), accompanied by surface roughening and bandgap lowering. According to the microstructural analyses, indium (In) and aluminum (Al) atoms have high reactivity with In-rich or Al-rich columns in a certain growth region. The addition of Zn impurities during InAlAs growth at the phase-separating temperature results in the suppression of phase separation, which can be attributed to a high probability of Zn incorporation into the sites, which generates an In-rich and Al-rich phase column in the phase-separated InAlAs layer. Based on atomic force microscopy (AFM) and high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) analysis, we classify four types of InAlAs surface morphology as a function of the growth temperature and flow rate of Zn impurities.

Influence of in volatilization on photoluminescence in InGaN/GaN multiple quantum wells

Two multiple quantum well (MQW) InGaN/GaN structures emitting green light, without (A) and with (B) an indium (In) volatilization suppression technique (IVST) during growth of the active region, were fabricated. The dependencies of the photoluminescence (PL) spectra upon temperature at different levels of excitation power were investigated. The results indicate that an IVST can increase the In content while suppressing the phase separation caused by volatilization of that In incorporated in the well layers. Also, compared with Structure B with IVST, which contains one phase structure, Structure A without IVST, which contains two separate phases (i.e., an In-rich phase and an In-poor phase), exhibits higher internal quantum efficiency (IQE) at low excitation power and lower IQE at high excitation power. The former is mainly attributed to the stronger In-rich phase-related localization effect of Structure A, because the In-rich phase-related emission dominates the PL spectra of Structure A at a low excitation power; the latter is mainly due to the In-poor phase-related weaker localization effect of Structure A, because the In-poor phase-related emission dominates the PL spectra of Structure A at high excitation power because localized states in this In-rich phase are saturated.

Influences of Ag and In Alloying on Microstructure and Mechanical Properties of Sn-58Bi Solder

Ag (2.0 wt.%) and In (1.5 wt.%) were alloyed into Sn-58Bi eutectic solder, and the individual and combined influences of Ag and In on the microstructure, microhardness, and impact toughness of the SnBi solder were investigated. The results reveal that the microstructures of the SnBiAg, SnBiIn, and SnBiAgIn alloyed solders are coarser than that of the SnBi eutectic solder. Fine Ag3Sn particles are formed in the SnBiAg and SnBiAgIn solders, while small regions of In-rich phases appear in the SnBiIn and SnBiAgIn solders. The microhardness of the three alloyed solders are higher than the SnBi solder, and the Sn-rich phases in the alloyed solders show higher nanohardness, while the nanohardness of the Bi-rich phases with Ag and In addition changes little. The impact toughness of the SnBiAg, SnBiIn, and SnBiAgIn solders are observed to be higher than the SnBi solder, especially in the case of the SnBiAgIn solder. The improvement in ductility of the Sn-rich phase induced by the In solution, and the strengthening effect from the Ag3Sn particles are predicated to be the reason for the increase in impact toughness. The fracture surfaces demonstrate that plastic deformation of the SnBiAgIn solder during the impact process is more obvious. Overall, the combined addition of Ag and In can increase the microhardness and impact toughness of SnBi eutectic solder.

Corrosion behavior of as-cast Mg–5Sn based alloys with In additions in 3.5 wt% NaCl solution

The corrosion behavior of as-cast Mg–5Sn–xIn (x = 0, 1, 2, 3, 4, all in wt%) alloys in 3.5 wt% NaCl solution was investigated using weight loss, hydrogen evolution and electrochemical test. The results showed that the microstructures of all alloys consisted of typical coarse dendrites without the presence of any In-rich phase. The corrosion resistance of Mg–5Sn–xIn alloys was enhanced monotonously with increasing In content up to 3 wt%. The electrochemical measurements revealed that such improvements could be mainly attributed to the retardation of cathodic reaction, decreasing the rate of hydrogen evolution.

Microstructure and shear property of In-Sn-xAg solder joints fabricated by TLP bonding

Transient liquid phase (TLP) bonding was applied to prepare Cu/In-Sn-xAg/Cu (x = 20, 30, 40, 50, 60, 70 wt%) solder joints, and the effect of Ag particle content on joint microstructure, shear property and growth mechanism of intermetallic compound (IMC) was studied. The results indicated that the microstructure of solder joint consists of interfacial diffusion reaction zone and particle in situ reaction zone. The IMC in interfacial diffusion reaction zone is Cu3(In, Sn) phase and the IMCs in in situ reaction zone is composed of In-rich phase + Ag particle + ζ-Ag3In + Ag3(In, Sn). With the increasing Ag particle content, the thickness of IMC layer in diffusion reaction zone is decreased, the total amount of In-rich phase and Ag3(In, Sn) phase in in situ reaction zone is decreased, the quantity of Ag particles and ζ-Ag3In phase is grew. The AgIn2 phase is a stable IMC formed as a preferential reaction because it requires less Gibbs free energy than Sn-Ag phase, and it is transformed to ζ-Ag3In phase with increasing bonding time to 10 min. The void ratio of solder joints is decreased firstly and then increased with increasing Ag content. The shear strength of the joint is increased firstly and then decreased with increasing Ag particle content, and the maximum shear strength 22.2 MPa is obtained by Cu/In-Sn-50Ag/Cu solder joints. The shear fracture mechanism of solder joints is changed from ductile–brittle mixed fracture to brittle fracture.

Properties and microstructure changes in Au-Cu-based alloy with indium addition

In this work, the effects of indium addition on the microstructure, corrosion resistance and hardness in as-cast Au-Cu-based alloys were investigated. The experimental results indicated that as-cast Au-Cu-based shown a typical dendritic structure, and the secondary dendrite arm spacing of alloy was significantly decreased by adding indium element, especially when the In-rich phase existed at interdendritic region. The as-cast samples without indium and with 1 wt.% In were a single Au-Cu-based solid solution with face-centered cubic (f.c.c.) structure. Moreover, the In-rich phase of the alloy with 3 wt.% In shown granular structure, but with 5 wt.% In was network structure. With the indium content increasing, the hardness of alloy was significantly increased and exhibited better Hall-Petch type relationship with the secondary dendrite arm spacing. Minor indium addition enhanced the corrosion resistance of alloy, but when an In-rich phase generated at interdendritic region, the corrosion rate was increased due to the micro-galvanic effect and also affected by the structure of the In-rich phase.

Structural variations in indium tin tellurides and their thermoelectric properties

Indium-doped tin tellurides are promising and thoroughly investigated thermoelectric materials. Due to the low solubility of In2Te3 in SnTe and vice versa, samples with the nominal composition (SnTe)3-3x(In2Te3)x with 0.136 ≤ x ≤ 0.75 consist of a defect-rocksalt-type Sn-rich and a defect-sphalerite-type In-rich phase which are endotaxially intergrown and form nanoscale heterostructures. Such nanostructures are kinetically inert and become more pronounced with increasing overall In content. The vacancies often show short-range ordering. These phenomena are investigated by temperature-dependent X-ray diffraction and HRTEM as well as STEM with element mapping by X-ray spectroscopy. The combination of real-structure effects leads to very low lattice thermal conductivity from room temperature up to 500°C. Thermoelectric figures of merit ZT of heterostructured materials with x = 0.136 reach ZT values up to 0.55 at 400°C.

Mesoporous In-Sn binary oxides of crystalline framework with extended compositional variation

Indium-tin oxide is considered a highly promising mixed-metal oxide system, because it shows good performance in various industrial processes. Therefore, it will be of great importance to explore the possibility of obtaining new In-Sn oxides with controlled contents whose properties could be tailored. However, In or Sn content in In-Sn oxides has generally been restricted to <10% because of their low solid solubility into counterpart metal oxide framework. Herein, we report for the first solvothermal synthesis of crystalline mesoporous In-Sn oxides with a broad range of In/Sn ratios and their opto-electrochemical properties. For the synthesis, we use phenolic polymer as a structure-directing agent. Surprisingly, we observe that the phenolic polymer plays a critical role in overcoming their low solubility by manipulating kinetics of crystal nucleation and subsequet growth. As a result, we obtain In-rich rutile SnO2 phase without phase separation with up to 50% In content and Sn-rich rhombohedral In2O3 structure with higher In content. The synthesized materials are highly transparent regardless of In content. The electrochemical properties are sensitive to In content. Our strategy offers possibility of realizing crystalline mesoporous mixed-metal oxides with tunable contents, thus opening a new perspective for the development of optoelectronic materials.

Phase segregation, interfacial intermetallic growth and electromigration-induced failure in Cu/In–48Sn/Cu solder interconnects under current stressing

The evolution of microstructure in Cu/In–48Sn/Cu solder bump interconnects at a current density of 0.7 × 104 A/cm2 and ambient temperature of 55 °C has been investigated. During electromigration, tin (Sn) atoms migrated from cathode to anode, while indium (In) atoms migrated from anode to cathode. As a result, the segregation of the Sn-rich phase and the In-rich phase occurred. A Sn-rich layer and an In-rich layer were formed at the anode and the cathode, respectively. The accumulation rate of the Sn-rich layer was 1.98 × 10−9 cm/s. The atomic flux of Sn was calculated to be approximately 1.83 × 1013 atoms/cm2s. The product of the diffusivity and the effective charge number of Sn was determined to be approximately 3.13 × 10−10 cm2/s. The In–48Sn/Cu IMC showed a two layer structure of Cu6(Sn,In)5, adjacent to the Cu, and Cu(In,Sn)2, adjacent to the solder. Both the cathode IMC and the anode IMC thickened with increasing electromigration time. The IMC evolution during electromigration was strongly influenced by the migration of Cu atoms from cathode to anode and the accumulation of Sn-rich and In-rich layers. During electromigration, the Cu(In,Sn)2 at the cathode interface thickened significantly, with a spalling characteristic, due to the accumulation of In-rich layer and the migration of Cu atoms - while the Cu(In,Sn)2 at the anode interface reduced obviously, due to the accumulation of Sn-rich layer. The mechanism of electromigration-induced failure in Cu/In–48Sn/Cu interconnects was the cathode Cu dissolution-induced solder melt, which led to the rapid consumption of Cu in the cathode pad during liquid-state electromigration and this finally led to the failure.

Toward low-cost large-area CIGS thin film: Compositional and structural variations in sequentially electrodeposited CIGS thin films

In this study, we investigated the material growth and the local compositional homogeneity of CIGS thin films selenized from elemental Cu, In, Cu, Ga, and Cu stacked layers prepared by sequential electrodeposition, which is considered to be a promising production method for large-area thin film solar cells. It showed that the stacked layers first formed mixed metallic phases after a pre-heat treatment at 150°C in vacuum. Several intermediate phases such as CuInSe2, CuInrichGapoorSe2, Cu2Se, InSe/In2Se3, CuGa2, and CuInpoorGarich formed in Se vapor at a lower temperature (e.g., <350°C). Moreover, separation of the Ga-rich phase from the In-rich one was found in the film after selenization at 350°C, which is due to relatively slow growth for the Ga-related grains that was buried by the In-rich phase growing faster in the out-of-plane orientation. All metallic phases converted to separate CuInSe2 and CuGaSe2 phases when selenized at 450°C. Additional heat treatment at 550°C in Ar improved the Ga distribution, which enhanced the light absorbance.

Surface structures of In-Pd intermetallic compounds. I. Experimental study of In thin films on Pd(111) and alloy formation.

A combination of experimental methods was used to study the structure of In thin films deposited on the Pd(111) surface and the alloying behavior. X-ray photoelectron spectroscopy (XPS), low-energy electron diffraction (LEED), and scanning tunneling microscopy results indicate that surface alloying takes place at room temperature. Below 2 monolayer equivalents (MLEs), the LEED patterns show the formation of three rotational domains of InPd(110) of poor structural quality on top of the Pd(111) substrate. Both core-levels and valence band XPS spectra show that the surface alloy does not yet exhibit the electronic structure characteristic of the 1:1 intermetallic compound under these conditions. Annealing the 1 MLE thin film up to 690 K yields to a transition from a multilayer InPd near-surface intermetallic phase to a monolayer-like surface alloy exhibiting a well ordered (√3×√3) R30(∘) superstructure and an estimated composition close to In2Pd3. Annealing above 690 K leads to further In depletion and a (1 × 1) pattern is recovered. The (√3×√3) R30(∘) superstructure is not observed for thicker films. Successive annealing of the 2 MLE thin film leads the progressive disappearance of the InPd diffraction spots till a sharp (1 × 1) pattern is recovered above 690 K. In the high coverage regime (from 4 to 35 MLE), the formation of three rotational domains of a bcc-In7Pd3 compound with (110) orientation is observed. This In-rich phase probably grows on top of interfacial InPd(110) domains and is metastable. It transforms into a pure InPd(110) near-surface intermetallic phase in a temperature range between 500 and 600 K depending on the initial coverage. At this stage, the surface alloy exhibits core-level chemical shifts and valence band (VB) spectra identical to those of the 1:1 InPd intermetallic compound and resembling Cu-like density of states. Annealing at higher temperatures yields to a decrease of the In concentration in the near-surface region to about 20 at.% and a (1 × 1) LEED pattern is recovered.

Phase Separation in Single InxGa1–xN Nanowires Revealed through a Hard X-ray Synchrotron Nanoprobe

In this work, we report on the composition, short- and long-range structural order of single molecular beam epitaxy grown In(x)Ga(1-x)N nanowires using a hard X-ray synchrotron nanoprobe. Nano-X-ray fluorescence mapping reveals an axial and radial heterogeneous elemental distribution in the single wires with Ga accumulation at their bottom and outer regions. Polarization-dependent nano-X-ray absorption near edge structure demonstrates that despite the elemental modulation, the tetrahedral order around the Ga atoms remains along the nanowires. Nano-X-ray diffraction mapping on single nanowires shows the existence of at least three different phases at their bottom: an In-poor shell and two In-rich phases. The alloy homogenizes toward the top of the wires, where a single In-rich phase is observed. No signatures of In-metallic precipitates are observed in the diffraction spectra. The In-content along the single nanowires estimated from X-ray fluorescence and diffraction data are in good agreement. A rough picture of these phenomena is briefly presented. We anticipate that this methodology will contribute to a greater understanding of the underlying growth concepts not only of nanowires but also of many nanostructures in materials science.

Ternary CuInS2 photoelectrodes created using the sulfurization of Cu–In metal precursors for photoelectrochemical applications

Copper indium disulfide semiconductor layers are deposited onto glass substrates or fluorine-doped tin oxide-coated glass substrates with the reactive sulfurization and the sputtering of Cu–In metal precursors. X-ray diffraction patterns and energy dispersive analysis of X-ray results reveal that the samples change from the Cu-rich tetragonal CuInS2 to the In-rich CuInS2 phase with an increase in the [In]/[In+Cu] molar ratio in the metal precursors. The thicknesses and direct band gaps of the samples, determined from surface profile measurements and transmittance and reflectance spectra, are in the ranges of 0.82–1.29μm and 1.39–1.53eV, respectively. The carrier density and mobility of samples are in the ranges of 3.29×1014–1.9×1020cm−3 and 0.58–17.41cm2/Vs, respectively. A sample with an [In]/[In+Cu] molar ratio of 0.53 has a maximum photo enhancement current density of 5.81mA/cm2 at an applied bias of 0.4V vs. an Ag/AgCl electrode in aqueous Na2S (0.35M)+K2SO3 (0.25M) solution.

Enhanced thermoelectric performance in n-type Bi2Te2.994Cl0.006/In2Te3 composite

In the present study, we prepared n-type Bi2Te2.994Cl0.006/xwt.% In2Te3 samples by zone melting method and investigated their thermoelectric (TE) performance. The power factor (S2σ) was increased and the lattice thermal conductivity (κL) was decreased simultaneously, mainly due to the introduction of the nano-lamellar-like In-rich phase in the BiTeCl matrix. As a result, a peak ZT value of 0.94 was obtained, which was 20% higher than that of the matrix.

Characterization of (AgCu)(InGa)Se$_{\bf 2}$ Absorber Layer Fabricated by a Selenization Process from Metal Precursor

In this paper, the effects of Ag-alloying in the selenization of metal precursors to form (AgCu) (InGa)Se <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex></formula> are investigated. Metal precursors with different structures were prepared by sputtering from Cu <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{0.77}$</tex></formula> Ga <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{0.23}$</tex></formula> , Ag, and In targets. The phases and the composition of the precursor films were evaluated by X-ray diffraction, scanning electron microscopy (SEM), and energy dispersive X-ray spectrometry. The addition of a Ag layer between the Mo and Cu–Ga–In layers resulted in much less islanding of In-rich phases than typically observed in sputtered Cu–Ga–In films. Selenization at 475 °C of Ag-containing precursors resulted in better adhesion than precursors without Ag. After the selenization reaction, Ag and Cu were uniformly distributed through the film, although Ga remained near the back of the film, as was observed in precursors without Ag. A (AgCu)(InGa)Se <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$_{2}$</tex> </formula> -based solar cell with 13.9% efficiency was demonstrated.

Remarkable enhancement in photocurrent of In0.20Ga0.80N photoanode by using an electrochemical surface treatment

The photocurrent and incident photon conversion efficiency of In0.20Ga0.80N increased about 2 times after a simple electrochemical surface treatment. X-ray photoelectron spectroscopy and photoluminescence analysis suggested that In-rich InGaN region on the surface of the In0.20Ga0.80N electrode was removed by using the electrochemical surface treatment. The enhancement of the photocurrent was attributed to the removal of In-rich InGaN phases caused by indium segregations on the surface of the electrode, which played a major role as surface recombination centers of photo-generated electron-hole pairs.

Quantum Dots obtained by LPE from under-saturated In-As liquid phases on GaAs substrates

In this work we inform about quantum dots (QD) obtained by Liquid Phase Epitaxy (LPE) on GaAs substrates from under-saturated In-As liquid phases. In our processes, we have prepared saturated In-rich liquid phases by dissolving an InAs wafer at one of the temperatures interval from 450 to 414 C for 60 minutes. The contact between In-As liquid phase and the GaAs substrate was always done at a constant temperature of 444 C for 5 seconds. Thus, the growth temperature for most of the samples was higher than the liquidus temperature. We think that the growth driving force is related to a transient process that occurs when the system is trying to reach equilibrium. Under the atom force microscope (AFM) we have observed nano-islands on the surfaces of the samples obtained from under-saturated liquid phases prepared at 438, 432 and 426 C. The 25 K photoluminescence spectrum shows a peak at a 1.33 eV, in addition to the GaAs related line.