bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ic Compatible Processing of Si:Er for Optoelectronics
Authors: Ren F. Y. G. , Michel J. , Sun-Paduano Q. , Zheng B. , Kitagawa H. , Jacobson D.C. , Poate J.M. , Kimerling L. C. 
Published: March 2011

AbstractWe have fabricated the first Si:Er LED, operating at 300 K, based on an understanding of the Si-Er-O materials system. Er-doped Si (Si:Er) provides an exciting opportunity for the monolithic integration of Si based opto-electronics. In this paper, Er-Si reactivity, and Er diffusivity and solubility have been studied to establish Si:Er process compatibility with a silicon IC fabline. Er3Si5 is the most stable silicid formed; and it can be oxidized into Er2O3 at high temperature under any oxidizing conditions. Among Er compounds, Er2O3 luminesces and Er3Si5 and ErN do not. The diffusivity of Er in Si is low and SIMS analysis yields a diffusivity D(Er) ∼ 10−12cm2/s at 1300 C and ∼ 10−15cm2/s at 900 C, and a migration enthalpy of ΔHm(Er) ∼ 4.6 eV. The equilibrium solubility of Er in Si is in the range of 1016 cm−3 at 1300 C. The Si:Er LED performance is compared with GaAs LEDs to demonstrate its feasibility.
Photoluminescence of Thin SI1-xGEx Quantum Wells
Authors: Lenchyshyn L.C. , Thewalt M.L.W. , Houghton D.C. , Noel J.-P. , Rowell N.L. , Sturm J.C. , Xiao X. 
Published: March 2011

AbstractWell-resolved band edge photoluminescence spectra were obtained from SiGe quantum wells of various widths. In addition to the usual shallow bound exciton features, we observed a highly efficient deeper luminescence process, under conditions of low excitation density, in thick SiGe quantum wells. This luminescence band can be attributed to excitons localized by fluctuations in alloy concentration. The binding energy of the localized exciton feature is found to decrease with decreasing well width. In the thinnest quantum well samples only a single luminescence feature is observed at all power levels, while in several other thin quantum well samples having very sharp lines the localized exciton feature appears at higher energy than the bound exciton. Despite these changes in the spectra, the localized exciton luminescence could be identified in all cases by its characteristic intensity saturation at low excitation power density, as well as its slow decay time (∼ 1 ms). The mechanism behind the changes in the localized exciton luminescence may originate from limiting the exciton motion to two dimensions in thin wells, which at low temperatures would hinder migration to the lowest energy alloy fluctuation centers.
Catalysts Examined by Electron Spin Resonance-Examples from Hydrodesulfurization Catalysis
Authors: Silbernagel Bernard G. 
Published: March 2011

ABSTRACTThe utility of electron spin resonance (ESR) for catalyst characterization is illustrated for the desulfurization catalysts used to remove sulfur, nitrogen, and organically bound metals from petroleum. These catalysts consist of active metals (Mo, W, Co, Ni) in mixed oxide and sulfide phases on high surface area alumina supports. Coordinated studies of unsupported sulfide and oxide model systems determine the chemical form and number of defect sites on the actual catalysts. Parallel catalysis studies correlate ESR defects and catalytic activity for many reactions.
The Mössbauer Effect and Some Applications in Materials Research
Authors: Shenoy G. K. 
Published: March 2011

ABSTRACTA brief introduction to the Mössbauer effect is presented. The hyperfine interactions associated with the electric monopole, magnetic dipole and electric quadrupole moments of the nuclear states involved in the Mössbauer transition are described. Their use in materials research is illustrated through examples dealing with phase analysis, binary solubility, defect interaction and surface properties.
Some Applications of Spin Precession Methods to Problems in Materials Science
Authors: Kaufmann E. N. 
Published: March 2011

ABSTRACTNuclear and electron resonance and the Mössbauer effect are techniques which observe the interaction of moments with fields directly in the energy domain. An energy splitting, however, also implies the precession of the moment in the field. When a means exists to determine the orientation of the moment then the precession can be observed in the time domain. The direction of radiation emitted in a nuclear, muonic or atomic decay is correlated to the direction of corresponding moments (spins) and can thus act as a detector of spin precession. In the language of nuclear, muonic and atomic physics, these methods are called perturbed angular correlations (PAC), muonic spin rotation, and quantum beats, respectively. Below, these methods will be illustrated by displaying some examples of the application of perturbed angular correlations to a variety of materials systems.
Low-Lying Excitations and Local Motions in Na β-Alumina
Authors: Villa Marco , Bjorxstam John L. 
Published: March 2011

ABSTRACTWe present an NMR study of sodium motion and distribution in Na β-alumina below 160K. The 23Na lineshape shows that a rearrangement of sodiums occurs near 100K. Below this “transition”, a fraction of the sodium ions undergo a local motion that is an efficient mechanism for 23Na spin-lattice relaxation in the interval 50÷80K. This motion does not have a major influence upon the 27A1 relaxation. Below 50K the low-lying excitations typical of glasses control the spin-lattice relaxation processes of 27AI and, to a certain extent, 23Na.
Mixed Alkali Effects in δ-Aluminas
Authors: Bjorkstam John L. , Villa Marco , Aldrovaidi Sergio , Corti Maurizio , Frye Jamies S. 
Published: March 2011

ABSTRACTThis paper presents a NMR study of mixed alkali effects in δ-aluminas. It is shown that the BPP theory of relaxation does not describe the NMR results. However, with an elementary analysis of the data, NMR yields information about the cation dynamics which substantially agrees with the diffusion measurements.
Microscopic Study of Metal Hydrides using Electron Spin resonance
Authors: Venturini E. L. 
Published: March 2011

ABSTRACTElectron spin resonance (ESR) of dilute paramagnetic ions in nonmagnetic metallic hydrides provides microscopic information about the hydrogen ions in the immediate vicinity of the impurity. By comparing ESR spectra for different host metals and several hydrogen/metal ratios, one can determine material properties including host lattice symmetry, phase boundaries and occupation of available sites by hydrogen. Examples are presented of ESR of dilute Er in group IIIB and IVB metal hydrides, demonstrating the sensitivity and versatility of ESR as a spectroscopic technique.
MÖssbauer Effect Investigation of Hydrogen Rich Ternary Hydrides of YFe2 , DyFe2 and ErFe2
Authors: Viccaro P. J. , Niarchos D. , Shenoy G. K. , Dunlap B. D. 
Published: March 2011

ABSTRACTThe hydrogen rich ternary hydride phases of RFe2Hx (R=Y Dy, Er) with x>4 have been investigated using 57Fe, 161Dy and 166Er Mössbauer spectroscopy and bulk magnetization. In all cases, the presence of hydrogen results in a dramatic reduction in the moment on Fe as well as the magnetic transition temperature. The data also imply a simultaneous weakening of the R-Fe magnetic exchange.
Laser-Pulse Melting of Hafnium-Implanted Nickel Studied with Tdpac and Rbs/Channeling Techniques
Authors: Buene L. , Kaufmann E. N. , Mcdonald M. L. , Kothaus J. , Vianden R. , Freitag K. , Draper C. W. 
Published: March 2011

ABSTRACTThe perturbed angular correlation technique has been applied to study the local environment of tantalum in nickel after ion implantation of hafnium and after laser-pulse melting. The magnetic hyperfine interaction at the daughter nucleus tantalum in nickel is used to determine the uniqueness of the tantalum lattice site. Several hafnium concentrations were employed and auxiliary measurements using ion-beam channeling, Rutherford backscattering and Auger electron spectroscopy were performed.
The Electric Field Gradient in Noncubic Metals and Alloys
Authors: Witthuhn W. , De U. , Engel W. , Hoth S. , Keitel R. , Klinger W. , Seeböck R. 
Published: March 2011

ABSTRACTThe electric field gradient (efg) present in noncubic solids causes an energy–splitting of the nuclear levels via the quadrupole hyperfine interaction. During the last few years the perturbed angular correlation method has proved a unique experimental tool for investigating this interaction especially in metals. The basic principles of the method are discussed. Recent experimental results are given for pure metals and highly diluted systems as well as for alloys and intermetallics. The last section deals with theoretical aspects of the temperature dependence of the efg in pure metals.
Magnetic Resonance as a Probe of Anisotropic Conductors
Authors: Clark W. G. 
Published: March 2011

ABSTRACTA review is given of the wide range of magnetic resonance methods used to study the special properties of quasi onedimensional (1-d) conductors. Specific examples are presented which show how magnetic resonance methods have been exploited (a) to tell if the conduction is 1-d, (b) to locate the conduction electrons on a molecular distance scale, (c) to probe the unusual effects of disorder in 1-d conductors, (d) to study the charge density wave transition, and (e) to verify exotic electrical transport mechanisms, such as charged solitons in trans-(CH)x.
Nmr and Mössbauer Effect Studies on Diluted Heisenberg Ferromagnets and Spin-Glasses: EuxSr1−xS
Authors: Lütgemeier H. , Sauer Ch. , Zinn W. 
Published: March 2011

ABSTRACTThe systematic variations of experimentally determined exchange and hyperfine (h.f.) interactions between Eu2+ ions are compared firstly within the EuX (X=0,S,Se,Te) series of compounds and secondly in the magnetic dilution system EuxSr1−xS. Reasonably relations can be established between the individual nearest and next nearest neighbour exchange interactions (J1,J2 ) and the transferred h.f. interactions (ΔB1 , ΔB2 ), respectively, by considering their variations with the Eu–Eu distances (R1,R2). Using these results, the measured mean hyperfine field, BI(x), and the ferromagnetic saturation h.f. field, B↑↑ (x), of the EuxSr1−xS system can be related reasonably well to the ferro- and paramagnetic phase boundaries, Tc(x) and θ (x), respectively.
Nuclear Spin Relaxation Investigations on the Influence of Impurities and Temperature on the Mean Free Path of Mobile Dislocations in Nacl
Authors: Alsem W. H. M. , Th. J. , De Hosson M. , Tamler H. , HackelÖEr H. J. , Kanert O. 
Published: March 2011

ABSTRACTDislocation motion in alkali halide single crystals is strongly impeded by the presence of impurities, apart from obstacles built by the forest dislocations. The mean free path L of stepwise moving dislocations is measured by determination of the spin-lattice relaxation rate 1/T1ρ as a function of the strain rate έ, varying the content of impurities and the temperature. The latter influences the distribution of the point defects and the activation rate of dislocations before obstacles, while the former merely shorten L, thereby raising 1/T1ρ.
μ+e-Hyperfine Interactions in Quartz Crystals
Authors: Brewer J.H. , Fleming D.G. , Spencer D.P. 
Published: March 2011

ABSTRACTLongitudinal muonium spin relaxation/modulation in zero magnetic field (zf-MSR) has been used to study muonium (μ+e-) atoms in single-crystal α-quartz between 5 K and room temperature. At 6 K, three frequencies are observed, corresponding to a triaxial hyperfine matrix whose principal values are close to those observed for hydrogen atoms frozen into known sites. For intermediate temperatures the Mu atoms “hop” between sites, causing a relaxation whose rate first increases with the hop rate and then decreases due to motional narrowing. Finally, at room temperature, a single-frequency oscillation is observed, corresponding to a uniaxial motionally-averaged hyperfine interaction.
The Motionally Narrowed Nmr Line Shape of Ammonium Selenate,
Authors: Yao Ching , Hallsworth R. , Lowe I. J. 
Published: March 2011

ABSTRACTThe proton free induction decay f(t) of ammonium selenate is measured from temperatures of no apparent effects of lattice motion (−185°C) upon f(t), to substantial motional effects (−145°C) upon f(t). Our measured results are consistent with a classical hindered rotational motion of the ammonium group. The deviation of f(t) from the rigid-lattice fid fo(t) can be expanded in a Taylor series asFrom the Δ1f(t) data, a3 and a4 are derived, and they are well fitted by the simple relationswhere ν is the jump frequency of the rotational motion, T1r is the rotating-frame spin-lattice relaxation time, and ω1 the strength of the rotating magnetic field in frequency units. α, C3 and C4 are calculable constants of order unity.
Impurity Diffusion by NMR
Authors: Beckett James R. , Pourquié Jean , Ailion David C. 
Published: March 2011

ABSTRIACTWe discuss a recently developed technique for studying the diffusion of spins with a small gyromagnetic ratio and apply it to investigate the nature of Ag+diffusion in AgF. We also investigate the potential application of this technique to the observation of diffusing impurities. Experimental studies on Cu:3% Al and (P2O5).8(Li2O).2 glass are described.
Use of a Native Oxide of AlxGa1−xAs in the Fabrication of Integrated Laser/Modulators
Authors: Burton R.S. , Schlesinger T.E. 
Published: March 2011

ABSTRACTA planar self-aligned process for fabricating integrated lasers and modulators is described. This process employs a native oxide of AlxGa1−xAs to form the waveguide structure and dielectric passivation layer. Wet oxidation of AlxGa1−xAs is being investigated to determine possible processing parameters that result in good quality oxides and a reliable fabrication process. Variations in the mechanical properties were observed with changes in processing parameters.
Many Body Effects in Strained Quantum Well Lasers
Authors: Banerjee S. , Srivastava A. K. , Bandyopadhyay A. , Chand N. 
Published: March 2011

ABSTRACTUnusually large transverse magnetic component has been observed at energy corresponding to the edge of heavy hole band in the optical emission from unstrained and strained layer single quantum well lasers above threshold condition. The existing model of Fermi sea shake-up is inadequate to explain the enhancement in the TM component beyond lasing threshold. Our results indicate that under lasing conditions the directional properties of the emitting dipole arising from electronic transitions to the heavy hole band is modified such that the dipole moment has equal projections in x, y and z directions.
Fabrication Techniques for GaAs Based HBTS and FETs
Authors: Ren F. 
Published: March 2011

ABSTRACTProcess technologies for self-aligned AlGaAs/GaAs and lnGaP/GaAs heterojunction bipolar transistors (HBTs) as well as dry etching fabrication schemes for submicron AlGaAs/GaAs based field effect transistors (FETs) are presented. Multiple energy F+ and H+ ions were used to isolate the active devices for HBTs. The resistance of test wafers at 200 °C showed no change over periods of 50 days. Highly selective dry and wet etch techniques for InGaP/GaAs and AlGaAs/GaAs material systems were used to uniformly expose junctions. Reliability of the alloyed ohmic contact and feasibility of the non-alloyed ohmic contact metallizations for both p and n type GaAs layers will be discussed. The reproducible gate recess etching is one of the critical steps for AlGaAs/GaAs based FETs. The etching selectivity, damage, pre and post-clean procedure were studied in terms of device performance. A simple low temperature SiNx deposition and an etch-back process with optical stepper were used to demonstrate 0.1 μm Y-shape gate feature.
Magnetron Dry Etching for Photonic Device Fabrication
Authors: Arnot H. E. G. , Zappe H. P. , Epler J. E. , Graf B. , Widmer R. , Lehmann H. W. 
Published: March 2011

ABSTRACTMagnetron dry etching using SiCl4, combined with a smooth reflowed photoresist masking technique has been used to fabricate GaAs/AlGaAs ridge waveguides. The effect of pressure, flowrate and power on etch rate and sidewall smoothness has been studied. Waveguides fabricated using optimum parameters exhibited optical losses lower than those achievable using wet etching. This process was further used in the fabrication of Fabry Perot ridge lasers, detectors and phase modulators.
Schottky Contacts Formed on Phosphidized InGaAs
Authors: Sugino Takashi , Sakamoto Yoshifumi , Ninomiya Hideaki , Matsuda Koichiro , Shirafuji Junji 
Published: March 2011

ABSTRACTThe surface of InGaAs (In 53 %) lattice-matched to InP has been phosphidized using phosphine plasma. X-ray photoelectron spectroscopy analysis indicates that substitution of phosphorus for arsenic and deposition of phosphorus layer occur due to phosphidization. Formation of indium and arsenic oxides is suppressed at the phosphidized surface of InGaAs, while phosphorus oxide is observed. Tunneling metal-insulator-semiconductor type Schottky contacts are formed on phosphidized InGaAs by evaporating various metals such as Au, Cu, Ti and Al. An effective barrier height as high as 0.7 eV is evaluated from the room temperature current-voltage characteristic for Au/InGaAs Schottky contacts. The true barrier height estimated from the Richardson plot varies depending on the metal work function.
Behavior of Zinc During Formation of Au(Zn) Ohmic Contacts to P-Type GaAs
Authors: Kamińska E. , Piotrowska A. , Mizera E. , Zarecka R. , Adamczewska J. , Dynowska E. 
Published: March 2011

ABSTRACTThe reactions between (100) GaAs and Au, Zn, and Au(Zn) ohmic contact metallization have been investigated by the use of transmission electron microscopy and x-ray diffraction. Emphasis is placed on the particular role of Zn during consecutive stages of the formation of an ohmic contact to p-GaAs. The most significant feature of the interaction of Zn with GaAs is the penetration of Zn atoms into the native oxide, which remains at the surface of GaAs after chemical treatment. Moreover, the presence of Zn in Au-based metallization is found to considerably suppress the thermally induced growth of metallization grains, making the microstructure of the contact virtually intact upon annealing at temperatures up to 460°C.
Low Contact Resistivity Mn/Au/Ti/Pd/Au P-Ohmic Contacts for HBTs
Authors: Vetanen B. , Haynes C. , Prasad S.J. , Beers I. , Park S. 
Published: March 2011

ABSTRACTObtaining good p-ohmics to the base layers of AlGaAs/GaAs HBTs have been difficult due to metal spiking and instability of the contacts to subsequent processing temperatures. To avoid spiking, non-alloyed contacts have been traditionally used. In this paper, we present a stable, non-spiking, low contact resistivity alloyed p-ohmic contact to HBT structures.
Current Transport in Low-Resistance Metal-InP Contacts
Authors: Clausen Thomas , Leistiko Otto 
Published: March 2011

ABSTRACTThe limiting transport processes for current flow across metal-semiconductor (MS) ohmic contacts to n- and p-type InP have been investigated for Au-based metallizations containing the doping elements Germanium and Zinc. It has been found that the Schottky barrier is lowered and in some cases vanishes during annealing. The current flow for an optimal ohmic contact is diffusion limited by a Fermi potential difference between the alloyed metallization and the bulk InP. For non-optimal ohmic contacts the current flow is also limited by thermionic emission across a low effective Schottky barrier.
Unexpected Penetration of AuGe/Pt Metal into a Interface Between a Atmospheric Chemical Vapor Deposition Silicon Dioxide Film and GaAs Wafer Surface
Authors: Saito Yasuyuki 
Published: March 2011

ABSTRACTIt was observed that thin metal (catalytic metal: platinum) penetrated into a interface between a chemical vapor deposition (CVD) silicon dioxide film and a Si–implanted electric thermal furnace, on the way to carrying out experiments on alloyed ohmic–metals with Si–implanted electrically conductive n–type GaAs crystal layers in order to obtain stable and uniform ohmic contact electrodes of low specific ohmic contact resistances for metal–semiconductor field–effect–transistor arrays as a observation tool of semi–insulating GaAs–crystal crystallographic uniformity.
Differences of Damage Production in GaAs and InP after MeV and Low Energy Ion Implantation
Authors: Wendler E. , Bachmann T. , Wesch W. 
Published: March 2011

ABSTRACTIon implantation induced damage production in GaAs and InP is investigated using Rutherford backscattering spectrometry in combination with channeling techniques and near-edge optical measurements. 200 keV and 1.6 MeV Ar+ ions are implanted at room temperature in GaAs and InP with ion doses varying between 2 × 1012 cm−2 and 3 × 1015 cm−2. Our results show that InP behaves similar for the two implantation energies and no influence of energy loss in electronic processes is found. In GaAs in the region of maximum nuclear energy deposition almost no difference in the damage production occurs for the two implantation energies. But for 1.6 MeV Ar+ implantation within the first 500 nm the defect concentration is very low in comparison to the nuclear energy deposition, which may be the consequence of ionizationinduced defect annealing and/or of the fact that in this depth region the amount of nuclear energy deposition is less than a critical value being necessary for the production of heavily damaged and amorphous zones.
Thermal Equilibrium Concentrations and Effects of Ga Vacancies in n-TYPE GaAs
Authors: Tan Teh Y. , You Homg-Ming , Gösele Ulrich M. 
Published: March 2011

ABSTRACTWe have calculated the thermal equilibrium concentrations of the various Ga vacancy species in GaAs. That of the triply-negatively-charged Ga vacancy, V3Ga has been emphasized, since it dominates Ga self-diffusion and Ga-Al interdiffusion under intrinsic and ndoping conditions, as well as the diffusion of Si donor atoms occupying Ga sites. Under strong n-doping conditions, the thermal equilibrium V3Ga concentration, CeqvGa.3−(n), has been found to exhibit a temperature independence or a negative temperature dependence, in the sense that the CeqvGa.3−(n) value is either unchanged or increases as the temperature is lowered. This is contrary to the normal positive temperature dependence of point defect theerqmal equilibrium concentrations, which decreases as the temperature is lowered. This CeqvGa.3−(n) property provides explanations to a number of outstanding experimental results, either requiring the interpretation thatV3−Ga has attained its thermal equilibrium concentration at the onset of each experiment, or requiring mechanisms involving point defect non-equilibrium phenomena. Furthermore, there exist also a few quantitative data which are in agreement with the presently calculated results.
Energetics of Impurity-Free Vacancy-Mediated Disordering of AlGaAs/GaAs Superlattices
Authors: Olmsted B.L. , Houde-Walter S.N. 
Published: March 2011

ABSTRACTWe report on a systematic study of impurity-free Al-Ga interdiffusion in AlGaAs/GaAs superlattices in sealed ampoules. Three ambients were explored: along the Ga-rich solidus, with no excess Ga or As in the evacuated ampoule, and with excess As less than that required to reach the As-rich solidus limit. In each of the ambients the Arrhenius dependence of the Al-Ga interdiffusion coefficient is represented by a single activation energy throughout the temperature range investigated (700-1050 °C). These results were obtained using four structures with superlattice periods ranging from 90 to 520 Å. Excellent agreement was obtained between the Al-Ga interdiffusion coefficients measured using superlattices on Sidoped and undoped GaAs substrates. With proper normalization to a constant As overpressure, PAs4 = 1 atm, the Ga- and As-rich activation energies are 3.26±0.12 eV and 4.91±0.23 eV, respectively. These activation energies are in the range predicted for Al-Ga interdiffusion mediated by group Ill-vacancy second nearest-neighbor hopping. The increase in energy when going from Ga- to As-rich conditions is attributed to a shift in the Fermi-level position towards the valence band with an increase in the ionized group Ill-vacancy concentration.