bluuebunny/crossref_metadata_2025_split huggingface dataset:
Growth and Characterization of the Binary Defect Alloy Cu2-xSe and the Relation to II–VI/I–III–VI Heterojunction Formation
Authors: Nelson Art J. , Sinha K. , Moreland John 
Published: April 2011

AbstractSynchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the development of the electronic structure at the CdS/Cu2Se heterojunction interface. Cu2−xSe layers were deposited on GaAs (100) by molecular beam epitaxy from Cu2Se sources. Raman spectra reveal a strong peak at 270 cm−1, indicative of the Cu2−xSe phase. Atomic force microscopy reveals uniaxial growth in a preferred (100) orientation. CdS overlayers were then deposited in-situ, at room temperature, in steps on these epilayers. Photoemission measurements were acquired after each growth in order to observe changes in the valence band electronic structure as well as changes in the Se3d and Cd4d core lines. The results were used to correlate the interfacial chemistry with the electronic structure and to directly determine the CdS/Cu2−xSe and heterojunction valence band discontinuity and the consequent heterojunction band diagram. These results are compared to the valence band offset (ΔEv) for the CdS/CuInSe2 heterojunction interface.
Enhanced Hydrogenation Due to Ultrasound Treatment in Polycrystalline Silicon: New Approach to Thin Film Defect Engineering
Authors: Ostapenko S. , Henley W. , Karimpanakkel S. , Jastrzebski L. , Lagowski J. 
Published: April 2011

AbstractWe applied the ultrasound treatment (UST) to improve properties of poly-Si thin films on glass substrates for thin-film transistor applications. A strong decrease of the sheet resistivity in hydrogenated films subjected to UST was observed. UST improves the film homogeneity as monitored by spatially resolved surface photovoltage mapping. Studies of hydrogenated thin-film transistors demonstrated remarkable UST induced improvement in transistor characteristics, especially, a reduction of leakage current by as much as one order of magnitude. All these effects are explained in terms of UST enhanced hydrogenation of poly-Si film.
Characterization of Fast Diffusing Charged Defects in Semiconductors
Authors: Heiser T. , Zamouche A. , Mesli A. 
Published: April 2011

AbstractA novel technique is introduced to study fast diffusing charged defects in semiconductors. It is based on the capacitance change induced by ion drift in a reverse biased Schottky barrier. It is shown that such charge movement yields exponential capacitance transients, which contain information about the defect concentration and mobility. The method is checked on Li-diffused samples, where the extracted diffusion coefficient are in good agreement with literature data. It is next applied to interstitial copper (Cui) in silicon. In the proposed experiment Cui gives rise to a well defined signal which enables us to investigate near room temperature defect reactions involving Cui. The diffusion data extracted from copper diffused and quenched silicon samples establishes the origin of the signal. Near room temperature precipitation kinetics of Cui are studied and energy barriers are extracted.
Photoluminescence of Extended Defects in Silicon-on-Insulator Formed by Implantation of Oxygen
Authors: Qian Y. H. , Evans J. H. , Giles L. F. , Nejim A. , Hemment P. L. F. 
Published: April 2011

AbstractPL and TEM have been carried out on SIMOX structures before and after thinning the silicon overlayer by a process of sacrificial oxidation. The implantation and high temperature annealing schedules involved in fabricating SIMOX material result in threading dislocations and stacking fault tetrahedra and pyramidals in the silicon overlayer. The optical activity of these extended defects is found to be low. However, after the sacrificial oxidation, strong dislocation related luminescence is observed, which is attributed to the presence of oxidation-induced stacking faults now present in the overlayer.
Type II Dislocation Loops and their Effect on Strain in Ion Implanted Silicon as Studied by High Resolution X-ray Diffraction
Authors: Thompson R. H. , Krishnamoorthy V. , Liu J. , Jones K. S. 
Published: April 2011

AbstractP-type (100) silicon wafers were implanted with 28Si+ ions at an energy of 50 keV and to doses of 1 × 1015, 5 × 1015 and 1 × 1016 cm−2, respectively, and annealed in a N2 ambient at temperatures ranging from 700°C to 1000°C for times ranging from 15 minutes to 16 hours. The resulting microstructure consisted of varying distributions of Type II end of range dislocation loops. The size distribution of these loops was quantified using plan-view transmission electron microscopy and the strain arising from these loops was investigated using high resolution x-ray diffraction. The measured strain values were found to be constant in the loop coarsening regime wherein the number of atoms bound by the loops remained a constant. Therefore, an empirical constant of 7.7 × 10−12 interstitial/ppm of strain was evaluated to relate the number of interstitials bound by these dislocation loops and the strain. This value was used successfully in estimating the number of interstitials bound by loops at the various doses studied provided the annealing conditions were such that the loop microstructure was in the coarsening or dissolution regime.
Ellipsometric Monitoring of Defects Induced by Electron Cyclotron Resonance Etching of GaAs
Authors: Snyder P. G. , Ianno N. J. , Wigert B. , Pittal S. , Johs B. , Woollam J. A. 
Published: April 2011

AbstractSpectroscopic ellipsometry (SE) measurements were made during and after electron cyclotron resonance (ECR) etching of GaAs. The spectral range for ex situ measurements, 1.24–5 eV, included the E1, E1+A1 critical points. The Ej, Ei+Aj structure was red shifted by about 50 meV, and broadened, by etching with a mixture of methane, argon, and hydrogen. Exposure to a pure H2 plasma caused greater red shifting and broadening, while a pure Ar ECR plasma produced only a slight red shift. The red shift is consistent with an increase in lattice constant of the order of 1%, in the top 10-30 nm. Broadening is consistent with crystalline lattice damage.
Degradation of InGaAs High Electron Mobility Transistors: The Role of Channel Composition and Thickness
Authors: Meshkinpour Marjohn , Goorsky Mark S. , Streit Dwight C. , Block Thomas R. , Wojtowicz Mike 
Published: April 2011

AbstractIn this study, we examined the performance of AlGaAs/InGaAs/GaAs pseudomorphic high electron mobility transistors with varying channel layer thicknesses for indium mole fractions of 0.21 and 0.24. For both compositions, we find that there is an optimum channel thickness above which the device performance is impaired. As expected the effective critical thickness of the In0.2iGa0.79As layer is higher. Surprisingly, however, transmission electron microscopy of the device structures indicates that the device performance is not impaired by the presence of a linear array of misfit dislocations. In fact, the devices with highest performance have misfit dislocations indicating that defect engineering may lead to improved performance in these structures. Furthermore, we find that device structures with poor performance have misfit dislocations along both of the <110> directions. Triple axis x-ray diffraction provides a non-destructive estimate of the dislocation densities present.
Effect of Fermi Level Pinning at the Surface During OMVPE Growth
Authors: Cohen R. M. , Chen C. Y. , Li W. M. , Simons D. S. , Chi P. H. 
Published: April 2011

AbstractDuring organometallic vapor phase epitaxy of GaAs, the Fermi energy is found to be pinned ≈200 meV below the intrinsic Fermi energy on a (lOO)-oriented surface. This was determined by making the first comparison of Zn concentration, Nzn. obtained from growth with that obtained at equilibrium, all under the same nominal ambient conditions. Donor solubility has been found to be virtually unchanged during growth of n- or p-type GaAs, and this is strong evidence that the Fermi level remains pinned at essentially the same energy during growth of n- or p-type GaAs. Consistent with Fermi level pinning, we find (1) the NZn is supersaturated in the epilayer for the ambient growth conditions used, (2) a large excess concentration of positively charged Ga interstitials can be grown into n-type GaAs and which diffuses into nearby p-type layers, causing (3) the Zn diffusivity, DZn ∼10−13 cm2/s, out of buried npn layers to be essentially independent of the ambient conditions. Annealing of a heavily Zn-doped layer at the surface can lead to 10−16<DZn<10−13 cm2/s at T=800°C simply by varying the Zn partial pressure over its commonly used range. Use of In-doped spikes in n- and p-type GaAs suggest that interstitial point defects have a strong effect on the group III diffusion.
Computation of the Onset of Point Defect Aggregation in Crystalline Silicon Using an Empirical Interatomic Potential
Authors: Sinno T. , Brown R.A. 
Published: April 2011

AbstractThe Stillinger-Weber interatomic potential is used in molecular dynamics simulations to investigate the equilibrium, transport and aggregation properties of self-interstitials and vacancies in crystalline silicon at temperatures ranging from 500K to the melting point. The simulations predict equilibrium configurations of a < 110 > dumbbell for the single self-interstitial and an inwardly relaxed structure for the single vacancy. Both single-defect structures exhibit significant derealization at high temperatures resulting in strongly temperature dependent entropies of formation, as suggested by diffusion experiments. Diffusion coefficients and mechanisms for the single defects are predicted as a function of temperature. The results for the single point defects are discussed in the context of the existing literature values. Aggregation of two point defects is investigated by the computation of binding energies and entropies for these structures. Interstitials exhibit significant aggregation driving forces across the entire temperature range under simulation conditions, while vacancies aggregate less readily.
Defect Reaction and Electrical Properties of Iron in N-Type Silicon
Authors: Kitagawa Hajime , Tanaka Shuji 
Published: April 2011

AbstractSince the first report by our group in 1992, iron-related defects in n-type silicon has been found to exhibit unusual in-diffusion and annealing properties. We review in this paper the recent progress in understanding the electrical and diffusion properties of iron-related defects in n-type silicon. We have shown from DLTS and Hall effect that iron in n-type silicon is electrically ionized and introduce one donor level at Ec-0.41 eV (level C) and, at least, one acceptor level at Ec-0.21 eV (level B). The donor character of former level has been confirmed by a Poole-Frenkel effect. The concentrations of two centers introduced are in the order of 1013 cm−3 at maxima. In-diffusion behavior of levels B and C show that these levels are intermediate states in a consecutive reaction of iron-related complex formation. Low-temperature isothermal annealing experiments from the room temperature to 200°C suggest that iron-related donor is formed, in part, by the electrostatic attractive force between two point charges.
Blocking of Magnetic Long Range Order Between the Monolayer and the Double Layer of Fe(110) on W(110)
Authors: Elmers Hans-Joachim , Hauschild Jens , Liu Guohui , Fritzsche Helmut , KÖhler Ulrich , Gradmann Ulrich 
Published: April 2011

ABSTRACTIn extension of a recent study on submonolayer magnetism of Fe(110) on W(110) [1], we observed the interplay of morphology and magnetic order in Fe(110)-films prepared on W(110) at 300 K, in a range of coverages θ between the pseudomorphic monolayer (θ = 1) and the pseudomorphic double layer (θ = 2), using a combination of STM, SPLEED, CEMS and TOM. Whereas the Curie-temperatures of the monolayer and the double layer are given by Tc(ML) = 230K and Tc(DL) = 450K, respectively, we observe in an interval of 1.20< θ < 1.48 ML a gap of magnetic long range order, for temperatures down to 115K. In CEMS, we observe superparamagnetic fluctuations for T < Tc(ML), but magnetic short range order for T < Tc(ML). The surprising blocking of long range order in the gap can only be explained from a quasi-antiferromagnetic indirect coupling between double-layer islands.
Observation of Micromagnetic Structure in Computer Hard Disks by Lorentz Transmission Electron Microscopy
Authors: Tang K. , Visokay M.R. , Sinclair R. , Ross C.A. , Ranjan R. , Yamashita T. 
Published: April 2011

ABSTRACTWe have observed micromagnetic structure in real computer hard disks with the typical structure of C/Co alloy/Cr/NiP/Al(substrate) using Lorentz transmission electron microscopy (LTEM). A chemical etching method was introduced to successfully prepare LTEM specimens directly from the computer hard disks with both smooth and mechanically textured substrates. Micromagnetic structural features, e.g., ripples and vortices, were studied in disks in bitswritten, ac-demagnetized, and saturation remanent magnetic states.
Pair Ordering Anisotropy In Amorphous Tb-Fe Thin Films
Authors: Hufnagel T.C. , Brennan S. , Clemens B.M. 
Published: April 2011

ABSTRACTWe have studied the structural origins of perpendicular magnetic anisotropy in amorphous Tb-Fe thin films by employing high energy x-ray scattering. The as-deposited films show a clear structural anisotropy, with a preference for Fe-Tb near-neighbors to align in the out-of-plane direction. Upon annealing, the magnetic anisotropy energy drops significantly, and we see a corresponding reduction in the structural anisotropy. The radial distribution functions indicate that the number of Fe-Tb near-neighbors increases in the in-plane direction, but does not change in the out-of-plane direction. Therefore, the distribution of Fe-Tb near-neighbors becomes more uniform upon annealing. We conclude that the observed reduction in perpendicular magnetic anisotropy energy is a result of this change in structure.
Effect of The Orientation of The Magnetic Field on The Giant Magnetoresistance of Fe/Cr Superlattices
Authors: Ustinov V.V. , Minin V.I. , Romashev L.N. , Semerikov A.B. , Del A.R. 
Published: April 2011

ABSTRACTWe study the magnetoresistance of [Fe/Cr]30/MgO superlattices grown by molecular beam epitaxy at a various magnetic field directions. The theory of the orientation dependence of the effect is developed. It is shown that the magnetic field strength dependence of magnetoresistance can be calculated for arbitrary orientation of magnetic field if this dependence is known for in-plane and perpendicular-to-plane magnetic fields. It is noted that the magnetization curve can be obtained by making use of the results of the magnetoresistance measurements.
The Effect of Impurity Doping of The Magnetic Layer on the Magnetoresistance and Saturation Field of FeCr/Cr and CoCu/Cu Multilayers
Authors: Daniels B.J. , Clemens B.M. 
Published: April 2011

ABSTRACTThe effect of doping the magnetic layer on the magnetoresistance and saturation field of epitaxial, sputter-deposited FeCr/Cr(001) and CoCu/Cu(001) multilayers was examined. FeCr/Cr films with a composition of [14 Å Fe1−xCrx(001)/8 Å Cr(001)]50 where x was varied from 0 to 0.5 and CoCu/Cu films with a composition of [8 Å Co1−xCux(001)/21 Å Cu(001)]40 where x was varied from 0 to 0.2 were deposited onto single crystal MgO(001). The bilayer period and epitaxial orientation of these films were determined by x-ray diffraction. In the FeCr/Cr system the room temperature magnetoresistance was constant at approximately 31% for x≤0.2 and decreased for larger Cr concentrations. The spin-dependent scattering (Δp) is increased over the x=0 value for x=0.1 and x=0.2. The magnetic field required to saturate these multilayers decreases linearly with increasing Cr concentration. The net result is that the sensitivity of these films is increased by Cr doping of the Fe layer. In the CoCu/Cu system the room temperature magnetoresistance, saturation field, and saturation magnetization decrease with the addition of Cu to the Co layer. In contrast to the FeCr/Cr system Δp does not increase with doping of the ferromagnetic layer. However, as in the FeCr/Cr films the sensitivity of these multilayers is increased with respect to that of the x=0 CoCu/Cu multilayer.
Magnetic Studies of Paramagnetic Clusters Encapsulated within the Sodalite Cage
Authors: Woodall Lee J. , Anderson P. A. , Armstrong A. R. , Edwards P. P. 
Published: April 2011

ABSTRACTThe magnetic properties of alkali-doped zeolites have been investigated using magnetic resonance spectroscopy. Although paramagnetic centres have been detected, the predominant species, in many cases, is spin-paired.
Nmr Studies of Bulk and Interface Structure in Co Based Multilayers
Authors: Panissod P. , Jay J.P. , Meny C. , Wojcik M. , Jedryka E. 
Published: April 2011

ABSTRACTOwing to the sensitivity of the hyperfine field to the topological and chemical environment of the probe nuclei, NMR spectra can be considered as histograms of the short range order ruling the structure of the material under investigation. Complementary to diffraction techniques this gives a local insight on the structure in the direct space. We review recent structural investigations of cobalt layers imbedded in Co/X multilayers and particularly of buried interfaces. Special attention has been given to the way intermixing takes place at the interfaces as its influence on the multilayer properties may be of considerable importance. Co/Cu multilayers, a case of weakly miscible elements, have been specially investigated owing to their GMR properties. But also cases of solid solution forming elements (Co/Ru or Co/Cr) or compound forming elements (Co/Fe) have been thoroughly studied. The latter case, which shows a stabilization of a bcc Co phase, will be discussed against the bulk alloy phase diagram.
Interactions of Phenol Resin Precursor and Calcium Aluminates
Authors: Hasegawa Masaki , Pushpalal G. K. Dinilprem , Takata Tomonori , Maeda Naomi , Kobayashi Tadashi 
Published: April 2011

ABSTRACTHere we investigated the interactions of phenol resin precursor and calcium aluminates, in relation to a recently innovated cement based material having a high flexural strength of more than 120MPa. An anhydrous phenol resin precursor was used as the binder and water was not contained in the initial composition.The method of processing consists of mixing of the cement, the phenol resin precursor, and small amounts of N-methoxymethyl 6-nylon and glycerol under high shear. Addition of the 6-nylon and glycerol was necessary to produce viscoelastic cement paste through a twin roll mill. Setting of calendered sheets takes place during the heat curing at 200° C. The best combination for high flexural strength among all the cements tested is the mixture of calcium aluminate cement and the resole type of phenol resin. Resulting outstanding affinity suggested specific interactions between the phenol resin and calcium aluminate.We here propose the interaction evidence of phenol moiety-calcium aluminate, based on the experimental data of differential scanning calorimetry and conduction calorimetry.
Rheological Properties of Silica Filled Poly (Methyl Methacrylate)
Authors: Rucker Derek P. , Bike Stacy G. 
Published: April 2011

ABSTRACTCeramic fiber spinning is critical to the manufacture of fibrous monolith ceramics, and understanding the interactions between the polymer matrix and ceramic particle filler is necessary to predict the flow properties of these systems. In this study, poly (methyl methacrylate) (PMMA) was filled with octadecanol-coated St6ber silica, and the rheological behavior of the filled polymers investigated at various filler volume fractions. The rheological behavior of these materials was studied in both dynamic and steady-state experiments. The time required for filled PMMA to reach steady-state behavior under constant shear stress was found to be long, on the order of an hour. The steady-state viscosities increased as expected with filler volume fraction, but did not correlate well with existing models. This is hypothesized to be a result of matrix-filler surface interactions, and will be investigated further in future work.
Chemical Stability of SC1-Cleaned Hydrogen Terminated Si(100) Surfaces
Authors: Bjorkman C. H. , Nishimura H. , Yamazaki T. , Alay J. L. , Fukuda M. , Hirose M. 
Published: April 2011

ABSTRACTSurface contamination and chemical stability of hydrogen terminated Si(100) surfaces have been studied using Fourier Transform Infrared Attenuated Total Reflection (FT-IR-ATR) spectroscopy and X-ray Photoelectron Spectroscopy (XPS). Hydrogen terminated Si(100) is obtained by removing the chemical oxide, formed in a low-concentration-NH4OH SC1 clean, in various HF based solutions. Using standard cleaning and loading conditions, we find a direct correlation between surface roughness and the amount of adsorbed C contamination. Oxidation during water rinsing and wafer loading observed by both FT-IR-ATR and XPS indicates that dihydride terminated silicon atoms are preferentially oxidized. Optimizing the water rinse and wafer loading conditions reduces total atomic concentration of C, O, and F surface contamination from 20–30 at.% to less than 6 at.%. These clean surfaces enable XPS-identification of the Si-Hx components of the Si 2p core-level spectra as well as estimation of the relative surface concentration of Si-Hx and contamination species.
Study on Sulfur Passivation for CuInSe2 Polycrystalline Thin Film With (NH4)2SX Solution
Authors: Cheng Y. H. , Tseng B. H. , Loferski J. J. , Hwang H. L. 
Published: April 2011

ABSTRACTIn this work, we studied the removal of the native oxide on polycrystalline CuInSe2 thin films by KCN and effect of subsequent chemical sulfurization with (NH4)2Sx solution on these films. As a result of the treatment, a portion of the selenide film was transformed into Culn(S,Se)2 The Auger Electron Spectroscopy and X-ray photoelectron spectroscopy studies showed that KCN removed the oxygen and the sulfurization prevented regrowth of the oxides. The optical bandgap of the sulfurized films increased about 0.27 eV. From these experiments, we concluded that sulfur atoms are incorporated in the CuInSe2 to form a stable and higher bandgap layer, Culn(S,Se)2 which may passivate the CuInSe2 and improve the performance of polycrystalline photovoltaic cells made from it.
Surface Properties of GaAs Passivated With (NH4)2Sx Solution
Authors: Suh Kyung-Soo , Park Hyung-Ho , Lee Jong-Lam , Kim Haechon , Cho Kyung-Ik , Kim Kyung-Soo 
Published: April 2011

ABSTRACTSurface properties of GaAs passivated with (NH4)2Sx solution have been compared with HCl-treated GaAs using X-ray photoelectron spectroscopy, Sulfur treatment on GaAs surface results in the formation of S-Ga and S-As bonds, which remain after successive rinsing for I minute in DI water. The evolution of Ga 2p3 and As 3d peaks in the sulfidation treated GaAs was monitored with the exposing time to air. After 10 days exposure to air, the Ga-O and As-O bonds slightly increased, but maintained almost constant for further exposure. The increase of Ga-O and As-O bonds induces the partial decomposition of sulfur bonds. Decomposition and evaporation behaviors of sulfur and oxygen were observed through the heat treatment of sulfidation treated GaAs under ultra high vacuum (less than l × 10-9 torr). After anneal at 350 – 450 °C, slight decrease of sulfur and oxygen due to the decomposition of As-O bond were observed. No more sulfur was found after anneal at 550 – 650 °C, where the decomposition of Ga-O bond was completed.