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Publications
Publications (35)
Radiation-induced segregation is well known in metals, but has been rarely studied in ceramics. We discover that radiation can induce notable segregation of one of the constituent elements to grain boundaries in a ceramic, despite the fact that the ceramic forms a line compound and therefore has a strong thermodynamic driving force to resist off-st...
Low-temperature solid-phase epitaxy is a promising route for the synthesis of thin films of ScAlMgO4, a compound with lattice spacings close to compound semiconductors for which there are no practical lattice-matched bulk substrates. Amorphous ScAlMgO4 films deposited by sputtering on c-plane sapphire, (0001) Al2O3, were crystallized by subsequent...
The growth of single crystals of Ge-rich SiGe alloys in an extended composition range is demonstrated using the nanomembrane (NM) platform and III-V growth substrates. Thin films of high-Ge-content SiGe films are grown on GaAs(001) to below the kinetic critical thickness and released from the growth substrate by selectively etching a release layer...
The metal-organic vapor phase epitaxy (MOVPE) of the quaternary alloy In1-xGaxAs1-yBiy has been explored on InAs and InP substrates to determine the group III and group V incorporation kinetics and their inter-dependences during low temperature growth. Under the growth conditions investigated, Ga did not incorporate into the epitaxial InAs1-yBiy on...
The thermodynamic stability of Bi-containing III-V quaternary alloys was determined using the delta lattice parameter (DLP) model in conjunction with density functional theory (DFT) calculations. The DLP model and DFT-calculated enthalpy of mixing show remarkably good agreement for the In1-yGayAs1-xBix and GaAs1-x-yBixPy systems. Binodal and spinod...
The impact of post‐growth thermal annealing on the internal device parameters such as internal loss (αi), internal differential quantum efficiency (η0d) and modal material gain (Γg0J) of a single‐quantum well (QW) laser diodes employing GaAs0.965Bi0.035/GaAs0.75P0.25 active regions and emitting near λ∼980 nm was investigated. Parameter extraction f...
Single junction solar cells employing 30-period and 50-period GaAs0.965Bi0.035/GaAs0.75P0.25 (Eg ∼ 1.2 eV) multiple quantum wells (MQWs) as base regions were grown by metal organic vapor phase epitaxy. Room temperature photoluminescence measurements indicated a peak spectral emission at 1.18 eV, and the spectral dependence of the external quantum e...
Laser diodes employing a strain-compensated GaAs1−xBix/GaAs1−yPy single quantum well (SQW) active region were grown by organometallic vapor phase epitaxy (OMVPE). High resolution x-ray diffraction, room temperature photoluminescence, and real-time optical reflectance measurements during the OMVPE growth were used to find the optimum process window...
The integration of emerging complex-oxide compounds into sophisticated nanoscale single-crystal geometries faces significant challenges arising from the kinetics of vapor-phase thin-film epitaxial growth. A comparison of the crystallization of the model perovskite SrTiO3 (STO) on (001) STO and oxidized (001) Si substrates indicates that there is a...
We investigate the change of the valence band energy of GaAs1-xBix (0<x<0.025) as a function of dilute bismuth (Bi) concentration, x, using x-ray photoelectron spectroscopy (XPS). The change in the valence band energy per addition of 1 % Bi is determined for strained and unstrained thin films using a linear approximation applicable to the dilute re...
Laser diodes employing strain-compensated GaAs1-xBi x /GaAs1-yP y quantum well (QW) active regions were grown by metalorganic vapor phase epitaxy (MOVPE). High resolution x-ray diffraction, room temperature photoluminescence, and in situ optical reflectance monitoring during the MOVPE growth provided valuable feedback for the optimization of the ma...
The effects of a 45 min anneal at 800 C on the physical properties and microstructure of a five-period GaAs1-xBi x /GaAs1-yBi y superlattice with y ≠ were studied using room-temperature photoluminesence spectroscopy, high-resolution x-ray diffraction, high-angle annular-dark-field scanning transmission electron microscopy (HAADF-STEM), and atom pro...
The influence of the surface step termination on the metal-organic vapor phase epitaxy of GaAs1-yBiy was explored by examining the epitaxial layer growth rate, composition, and morphology characteristics on the offcut and mesa-patterned (001) GaAs substrates. Vicinal surfaces offcut to (111)B with a high density of As-terminated steps ('B-steps') i...
The three-dimensional distribution of Bi atoms in a GaAs1-xBix/GaAs superlattice grown by metalorganic vapor phase epitaxy (MOVPE) was studied using atom probe tomography (APT). The Bi distribution in the growth direction deduced from APT agreed quantitatively with the complex Bi concentration profile that was discovered using high-angle annular da...
div class="title"> Bismuth Particle Formation in Annealed Dilute GaAs i-x-y P y Bi x Alloys
- Volume 22 Issue S3 - Z. R. Lingley, B. Foran, M. Brodie, Y. Sin, N.P. Wells, S. C. Moss, K. Forghani, Y. Guan, L. Mawst, H. Kim, T.-H. Kim, T. F. Kuech
Metal oxide coatings on cathodes can improve electrochemical stability and longer life cycle of rechargeable Li-ion batteries. Such coatings protects the cathode surface from the direct contact with electrolyte, helps to prevent the formation of SEI (solid electrolyte interphase) layer, reduce ionic dissolution and that results in improved capacity...
GaAs1-xBi x /GaAs multiple quantum well heterostructures were grown by organo-metallic vapor phase epitaxy (OMVPE) at low temperatures and were subsequently in-situ annealed under an arsine (AsH3) overpressure in the OMVPE reactor. Photoluminescence (PL) measurements were performed to establish the optimized annealing condition for the highest lumi...
Metal oxide coatings can improve the electrochemical stability of cathodes and hence, their cycle-life in rechargeable batteries. However, such coatings often impose an additional electrical and ionic transport resistance to cathode surfaces leading to poor charge-discharge capacity at high C-rates. Here, a mixed oxide (Al2O3)1-x(Ga2O3)x alloy coat...
The three-dimensional distribution of Bi atoms in a GaAs1−xBix/GaAs superlattice grown by metalorganic vapor phase epitaxy (MOVPE) was studied using atom probe tomography (APT). The Bi distribution in the growth direction deduced from APT agreed quantitatively with the complex Bi concentration profile that was discovered using high-angle annular da...
Metal oxide coatings on cathodes can improve electrochemical stability and longer life cycle of rechargeable Li-ion batteries. Such coatings protects the cathode surface from the direct contact with electrolyte, helps to prevent the formation of SEI (solid electrolyte interphase) layer, reduce ionic dissolution and that results in improved capacity...
III-V multi-junction solar cells are based on a triple-junction design that consists of an InGaP top junction, a GaAs middle junction, and a bottom junction that employs either a 1eV material grown on the GaAs substrate or InGaAs grown on the Ge substrate. The most promising 1 eV materials under extensive investigation are the bulk dilute nitride s...
Metal-organic vapor phase epitaxy (MOVPE) of tensile-strained GaAs1-yPy layers on GaAs substrates was carried out over the temperature range from 380 to 650C. The P content in the GaAs1-yPy epitaxial layers initially decreases with decreasing growth temperature from 550 to 650C, while then exhibiting an increase with decreasing growth temperature f...
GaAs1−z Biz /GaAs1−y Py strained-compensated quantum well (QW) structures for laser applications were grown by metalorganic vapor phase epitaxy. The band offsets for the GaAs1−z Biz /GaAs1−y Py heterojunction were calculated by the density functional theory, and the design of strain-compensated structures was undertaken by the zero stress analysis....
TiO2-coated Co/C catalysts prepared by atomic layer deposition (ALD) were used to study the effect of TiO2 overcoating on a Co/C catalyst for electrochemical water oxidation. The Co/C catalyst with a thin layer overcoating of TiO2 (ALD(TiO2)-Co/C) demonstrated 2.5 times higher turnover frequency (TOF) than the Co/C catalyst for the reaction. The TO...
We report the use of two Raman signatures, the Bi-induced longitudinal-optical-plasmon-coupled (LOPC) mode and the GaAs Fröhlich scattering intensity, present in nominally undoped (100) GaAs
1−yBiy to predict the 300K photoluminescence intensity and Bi composition (y) in GaAs
1−yBiy. The LOPC mode is used to calculate the hole concentration in GaAs...
The growth of large lattice mismatched materials has been studied for many years in order to understand mismatch-derived defects, their mode of introduction, and their mitigation. Traditional approaches focused on the formation of ‘buffer’ layers. ‘Buffer’ layers are intermediate layers within a growing structure which allow a chemical or structura...
This study compares the effectiveness of two Bi sources, trimethyl bismuth (TMBi) and triethyl bismuth (TEBi), in the growth of GaAs1-yBiy thin films. Through optimization of the growth conditions, GaAs1-yBiy-GaAs heterostructures with high lateral homogeneity of Bi are grown. TEBi results in a lower carbon concentration than is typical of methyl-b...
A set of GaAs
1−xBix/GaAs multilayer quantum-well structures was deposited by metal-organic vapor phase epitaxy at 390 °C and 420 °C. The precursor fluxes were introduced with the intent of growing discrete and compositionally uniform GaAs
1−xBix well and GaAs barrier layers in the epitaxial films. High-resolution high-angle annular-dark-field (or...
Among several approaches proposed to achieve high-efficiency III-V multi-junction solar cells, the most promising approach is to incorporate a bottom junction consisting of a 1 - 1.25 eV material. In particular, several research groups have studied MBE- and MOVPE-grown 1 - 1.25 eV bulk (In)GaAsN(Sb) dilute nitride lattice matched to GaAs substrates...
The growth and properties of alloys in the alternative quaternary alloy system GaAs 1−y−zPyBiz were explored. This materials system allows simultaneous and independent tuning of lattice constant and band gap energy, Eg , over a wide range for potential near- and mid-infrared optoelectronic applications by adjusting y and z in GaAs 1−y−zPyBiz. Highl...
W(CO)6 and H2O2 were used in an atomic layer deposition (ALD)-like process to grow thin WOx films onto TiO2 powders in a fluidized bed reactor. Carbonyl precursors are not widely used in this application, so that deviations from an ideal ALD process, previously not examined with W(CO)6, were identified. The resulting WOx films were a result of both...
Theoretical and experimental studies have confirmed that the GaAs1-yBiy semiconductor alloy system has potential for long wavelength applications and devices with improved performance over other materials emitting at similar wavelengths. The growth of GaAs1-yBiy by metal-organic vapor phase epitaxy (MOVPE) remains a challenge; bismuth is not easily...
