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Excitation Functions for Reactions of Bev Protons on Indium (Master's Thesis)

Description: Abstract: "Indium was bombarded with protons in the energy range 2 to 6 Bev. Cross sections are reported for the (p,px+), (p,pn), and (p,p') reactions, as well as those for the formation of Be-7 and several neutron deficient isotopes of cadmium and indium. It was found that the (p,pn) yield increases slowly in the energy range 2 to 6 Bev, while the (p,px+) and (p,p') yields are approximately constant. The variation of the (p,pn) and (p,px+) yields with target thickness is discussed. The yields of several isomeric levels are correlated with their nuclear spin."
Date: January 1957
Creator: Nethaway, David Robert
Partner: UNT Libraries Government Documents Department

Thorium-carbon alloys

Description: A report about a study of the methods of melting and fabricating the dilute alloys of carbon in thorium. The results of the study are reported here.
Date: 1953
Creator: Goldhoff, R. M.; Ogden, Horace R. & Jaffee, Robert Isaac, 1917-
Partner: UNT Libraries Government Documents Department

The Determination of Indium in Indium Plutonium Solutions

Description: Abstract: "A gravimetric procedure is described for the analysis of indium-plutonium solutions. This procedure consists of a preliminary separation of the plutonium as the peroxide, followed by the quantitative precipitation of indium diethyl dithio carbamate from a slightly acid solution. The precipitate is dried at 105 C and weighed. Recoveries of 99.4 - 100.5% with an average precision of 2.3/100 were obtained on known Pu-In solutions containing 5 - 50 mg of indium per sample."
Date: December 12, 1950
Creator: Waterbury, Glenn R.
Partner: UNT Libraries Government Documents Department

Characterizing Composition Modulations in InAs/AIAs Short-Period Superlattices

Description: The formation of quantum wires has much interest due to their novel electronic properties which may lead to enhanced optoelectronic device performance and greater photovoltaic efficiencies. One method of forming these structures is through spontaneous lateral modulation found during the epitaxial growth of III/V alloys. In this paper, we report and summarize our investigations on the formation of lateral moduation in the MBE grown InAlAs/InP(001) system. This system was grown as a short-period superlattice where n-monolayers of InAs are deposited followed by m-Monolayers of AlAs (with n and m~2) and this sequence is repeated to grown a low strain InAlAs ternary alloy on InP(001) that exhibits lateral modulation. Films were grown under a variety of condition (growth temperature, effective alloy composition, superlattice period, and growth rate). These films have been extensively analyzed using X-ray diffraction, atomic force microscopy, and transmission electron microscopy (TEM) and microcharacterization, in addition to photon-based spectroscopes. Here we present results of several microstructural characterizations using a wide range of TEM-based techniques, and compare them to results from the other methods to obtain a unified understanding of composition modulation. Two strong points consistently emerge: 1) The lateral modulation wavelength is insensitive to growth temperature and effective alloy composition, but the strength of the lateral modulation is greatest near an effective alloy composition of In(0.46)Al(0.54)As, which corresponds to a slightly tensile global strain with respect to InP. 2) The composition variation for the strongly modulated films is as much as 0.38 InAs mole fraction. In addition, for these strongly modulated films, the modulation wave is asymmetric showing strongly peaked, narrower InAs-rich regions separated by flat AlAs-rich regions. We discuss these results and their possible implications in addition to detailing the techniques used to obtain them.
Date: April 26, 1999
Creator: Ahrenkiel, S.P.; Follstaedt, D.M.; Jones, E.D.; Lee, S.R.; Mascarenhas, A.; Millunchick, J. Mirecki et al.
Partner: UNT Libraries Government Documents Department

Inductively Coupled Plasma Etching in ICl- and IBr-Based Chemistries: Part II. InP, InSb, InGaP and InGaAs

Description: A parametric study of Inductively Coupled Plasma etching of InP, InSb, InGaP and InGaAs has been carried out in IC1/Ar and IBr/Ar chemistries. Etch rates in excess of 3.1 prrdmin for InP, 3.6 prnh-nin for InSb, 2.3 pm/min for InGaP and 2.2 ~rrdmin for InGaAs were obtained in IBr/Ar plasmas. The ICP etching of In-based materials showed a general tendency: the etch rates increased substantially with increasing the ICP source power and rf chuck power in both chemistries, while they decreased with increasing chamber pressure. The IBr/Ar chemistry typically showed higher etch rates than IC1/Ar, but the etched surface mophologies were fairly poor for both chemistries.
Date: November 23, 1998
Creator: Abernathy, C.R.; Cho, H.; Hahn, Y.B.; Hays, D.C.; Hobson, W.S.; Jung, K.B. et al.
Partner: UNT Libraries Government Documents Department

Investigation of the effects of compressive uniaxial stress on the hole carriers in p-type InSb

Description: The influence of uniaxial compression upon the Hall effect ad resistivity of cadmium-doped samples of InSb at 77 K, 64 K, and 12 K are reported. Unilaxial compressions as high as 6 kbar were applied to samples oriented in the {001} and {110} directions. The net hole concentration of the samples were about 5x10^13 cm^-3 at 77 K as determined from the Hall coefficient at 24 kilogauss.
Date: December 1975
Creator: Vaughn, Bobby J.
Partner: UNT Libraries

Development of Indium Oxide Nanowires as Efficient Gas Sensors

Description: Crystalline indium oxide nanowires were synthesized following optimization of growth parameters. Oxygen vacancies were found to impact the optical and electronic properties of the as-grown nanowires. Photoluminescence measurements showed a strong U.V emission peak at 3.18 eV and defect peaks in the visible region at 2.85 eV, 2.66 eV and 2.5 eV. The defect peaks are attributed to neutral and charged states of oxygen vacancies. Post-growth annealing in oxygen environment and passivation with sulphur are shown to be effective in reducing the intensity of the defect induced emission. The as-grown nanowires connected in an FET type of configuration shows n-type conductivity. A single indium oxide nanowire with ohmic contacts was found to be sensitive to gas molecules adsorbed on its surface.
Date: December 2011
Creator: Gali, Pradeep
Partner: UNT Libraries

Microstructure of compositionally modulated InAlAs

Description: The authors have observed spontaneous, lateral composition modulation in tensile InAlAs alloy films grown as short-period superlattices on InP (001). They have analyzed these films using transmission electron microscopy, x-ray reciprocal space mapping, and polarized photoluminescence spectroscopy. They find the growth front is nonplanar, exhibiting {approximately} 2 nm deep cusps aligned with the In-rich regions of the compositionally modulated films. In addition to the measured 15 nm wavelength modulation in the [110] direction, a modulation of 30 nm wavelength is seen in the orthogonal [1{bar 1}0] direction. The photoluminescence from the modulated layer is strongly polarized and red shifted by 0.22 eV.
Date: December 31, 1996
Creator: Twesten, R.D.; Millunchick, J.M.; Lee, S.R.; Follstaedt, D.M.; Jones, E.D.; Ahrenkiel, S.P. et al.
Partner: UNT Libraries Government Documents Department

The growth of InAsSb/InAsP strained-layer superlattices for use in infrared emitters

Description: We describe the metal-organic chemical vapor deposition growth of InAsSb/InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. These SLSs were grown at 500{degrees}C, and 200 torr in a horizontal quartz reactor using TMIn, TESb, AsH{sub 3},and PH{sub 3}. By changing the layer thickness and composition we have prepared structures with low temperature ({le}20K) photoluminescence wavelengths ranging from 3.2 to 4.4 {mu}m. Excellent performance was observed for an SLS LED and both optically pumped and electrically injected SLS lasers. An optically pumped, double heterostructure laser emitted at 3.86 {mu}m with a maximum operating temperature of 240 K and a characteristic temperature of 33 K. We have also made electrically injected lasers and LEDs utilizing a GaAsSb/InAs semi-metal injection scheme. The semi-metal injected, broadband LED emitted at 4 {mu}m with 80 {mu}W of power at 300K and 200 mA average current. The InAsSb/InAsP SLS injection laser emitted at 3.6 gm at 120 K.
Date: June 1, 1997
Creator: Biefeld, R.M.; Allerman, A.A. & Kurtz, S.R.
Partner: UNT Libraries Government Documents Department

Spontaneous lateral composition modulation in InAlAs and InGaAs short-period superlattices

Description: The microstructure of spontaneous lateral composition modulation along the [110] direction has been studied in (InAs){sub n}/(AlAs){sub m} short-period superlattices grown by molecular beam epitaxy on (001) InP. X-ray diffraction and transmission electron microscopy show that global strain ({var_epsilon}) in the superlattice reduces the degree of composition modulation, which disappears for the absolute value of {var_epsilon} > 0.7%. For tensile strains of {var_epsilon} {approx} +0.4%, they find that In-rich columns become regularly spaced and correlated with cusps in the growth surface. A similar correlation is seen in (InAs){sub n}/(GaAs){sub m} short-period superlattices between the enriched columns and the peaks and valleys of {l_brace}114{r_brace}{sub A} facets on the surface. The enriched columns in the (InAs){sub n}/(GaAs){sub m} layer (and the facets) extend for much longer distances ({approximately}0.2--0.4 {micro}m) in the [1{bar 1}0] direction than do the columns in the (InAs){sub n}/(AlAs){sub m} layer ({approximately} 56 nm).
Date: July 11, 1997
Creator: Follstaedt, D.M.; Twesten, R.D.; Millunchick, J.M.; Lee, S.R.; Jones, E.D.; Ahrenkiel, S.P. et al.
Partner: UNT Libraries Government Documents Department

The growth of mid-infrared emitting InAsSb/InAsP strained-layer superlattices using metal-organic chemical vapor deposition

Description: We describe the metal-organic chemical vapor deposition os InAsSb/InAsP strained-layer superlattice (SLS) active regions for use in mid-infrared emitters. These SLSs were grown at 500 {degrees}C, and 200 torr in a horizontal quartz reactor using trimethylindium, triethylantimony, AsH{sub 3}, and PH{sub 3}. By changing the layer thickness and composition we have prepared structures with low temperature ({le}20K) photoluminescence wavelengths ranging from 3.2 to 5.0 {mu}m. Excellent performance was observed for an SLS light emitting diode (LED) and both optically pumped and electrically injected SLS layers. An InAsSb/InAsP SLS injection laser emitted at 3.3 {mu}m at 80 K with peak power of 100 mW.
Date: October 1, 1997
Creator: Biefeld, R.M.; Allerman, A.A.; Kurtz, S.R. & Burkhart, J.H.
Partner: UNT Libraries Government Documents Department

Detection of lateral composition modulation by magnetoexciton spectroscopy

Description: An experimental signature for detecting spontaneous lateral composition modulation in a (InAs){sub n}/(GaAs){sub m} short period superlattice on an InP substrate based on magnetoexciton spectroscopy described. The authors find by aligning the magnetic field in three crystallographic directions, one parallel to and the other two perpendicular to the composition modulation direction, that the magnetoexciton shifts are anisotropic and are a good indicator for the presence of composition modulation.
Date: July 10, 1997
Creator: Jones, E.D.; Millunchick, J.M.; Follstaedt, D.; Lee, S.; Reno, J.; Twesten, R.D. et al.
Partner: UNT Libraries Government Documents Department

Optical Properties of InGaAsN: A New 1eV Bandgap Material System

Description: InGaAsN is a new semiconductor alloy system with the remarkable property that the inclusion of only 2% nitrogen reduces the bandgap by more than 30%. In order to help understand the physical origin of this extreme deviation from the typically observed nearly linear dependence of alloy properties on concentration, we have investigated the pressure dependence of the excited state energies using both experimental and theoretical methods. We report measurements of the low temperature photohnninescence energy of the material for pressures between ambient and 110 kbar. We describe a simple, density-functional-theory-based approach to calculating the pressure dependence of low lying excitation energies for low concentration alloys. The theoretically predicted pressure dependence of the bandgap is in excellent agreement with the experimental data. Based on the results of our calculations, we suggest an explanation for the strongly non-linear pressure dependence of the bandgap that, surprisingly, does not involve a nitrogen impurity band. Addhionally, conduction-band mass measurements, measured by three different techniques, will be described and finally, the magnetoluminescence determined pressure coefficient for the conduction-band mass is measured.
Date: January 25, 1999
Creator: Allerman, A.A.; Fritz, I.J.; Jones, E.D.; Kurtz, S.R.; Modine, N.A.; Tozer, S.T. et al.
Partner: UNT Libraries Government Documents Department

High-performance, lattice-mismatched InGaAs/InP monolithic interconnected modules (MIMs)

Description: High performance, lattice-mismatched p/n InGaAs/lnP monolithic interconnected module (MIM) structures were developed for thermophotovoltaic (TPV) applications. A MIM device consists of several individual InGaAs photovoltaic (PV) cells series-connected on a single semi-insulating (S.I.) InP substrate. Both interdigitated and conventional (i.e., non-interdigitated) MIMs were fabricated. The energy bandgap (Eg) for these devices was 0.60 eV. A compositionally step-graded InPAs buffer was used to accommodate a lattice mismatch of 1.1% between the active InGaAs cell structure and the InP substrate. 1x1-cm, 15-cell, 0.60-eV MIMs demonstrated an open-circuit voltage (Voc) of 5.2 V (347 mV per cell) and a fill factor of 68.6% at a short-circuit current density (Jsc) of 2.0 A/cm{sup 2}, under flashlamp testing. The reverse saturation current density (Jo) was 1.6x10{sup {minus}6} A/cm{sup 2}. Jo values as low as 4.1x10{sup {minus}7} A/cm{sup 2} were also observed with a conventional planar cell geometry.
Date: October 1, 1998
Creator: Fatemi, Navid S.; Wilt, David M.; Hoffman, Richard W., Jr.; Stan, Mark S.; Weizer, Victor G.; Jenkins, Phillip P. et al.
Partner: UNT Libraries Government Documents Department

Spectral utilization in thermophotovoltaic devices

Description: Multilayer assemblies of epitaxially-grown, III-V semiconductor materials are being investigated for use in thermophotovoltaic (TPV) energy conversion applications. It has been observed that thick, highly-doped semiconductor layers within cell architectures dominate the parasitic free-carrier absorption (FCA) of devices at wavelengths above the bandgap of the semiconductor material. In this work, the wavelength-dependent, free-carrier absorption of p- and n-type InGaAs layers grown epitaxially onto semi-insulating (SI) InP substrates has been measured and related to the total absorption of long-wavelength photons in thermophotovoltaic devices. The optical responses of the TPV cells are then used in the calculation of spectral utilization factors and device efficiencies.
Date: December 31, 1997
Creator: Clevenger, M.B. & Murray, C.S.
Partner: UNT Libraries Government Documents Department