bluuebunny/crossref_metadata_2025_split huggingface dataset:
Light Scattering Study of the Evolution of the Surface Morphology During Growth of Ingaas on GaAs
Authors: Lavoie C. , Haveman B. , Nodwell E. , Pinnington T. , Tiedje T. , Goldman R. S. , Kavanagh K. L. , Hutter J. L. , Bechhoefer J. 
Published: April 2011

AbstractIn-situ elastic light scattering is used to measure the evolution of the surface morphology of InxGa1−xAs films during molecular beam epitaxy growth on GaAs substrates. The in-situ measurements are compared with ex-situ measurements of the surface morphology on quenched films by optical scatterometry and atomic force microscopy (AFM). The AFM results are in good agreement with the rms roughness obtained from light scattering and both techniques detect the onset of misfit dislocation formation in this system.
Investigation of Local Structures Around Mn Atoms in In1-xMnxAs Diluted Magnetic Semiconductors Using Exafs
Authors: Soo Y. L. , Huang S. W. , Ming Z. H. , Kao Y. H. , Munekata H. , Chang L. L 
Published: April 2011

AbstractExtended x-ray absorption fine structure (EXAFS) techniques have been used to investigate the local structures in Inl-xMnxAs films grown by molecular beam epitaxy (MBE) under different processing conditions. For samples grown at low substrate temperatures (near 200°C) or with a low Mn concentration (about 1 atomic%), the Mn atoms can substitute for In in the InAs host, thus indicating that III-V diluted magnetic semiconductors (DMS) can indeed be prepared by substitutional doping of magnetic impurities. On the other hand, substitution dose not take place in high Mn concentration (above 10%) samples grown at high substrate temperatures (around 300°C); these samples contain a large amount of MnAs clusters and become ferromagnetic
A Real-time X-ray Scattering Study of Sputtering Growth of TiN Films
Authors: Jel J. H. , Noh D. Y. , Kim H. K. , Liang K. S. 
Published: April 2011

AbstractWe report the results of a real-time synchrotron x-ray scattering study of the growth of TiN thin films on Si(001) substrates by RF sputtering. Our experiemnts show that the morphology of the TiN films strongly depends on growth conditions. After the nucleation and growth takes place with random crystallographic orientation at the very early stage, the films grow with a preferred orientation. Such preferred orientation was found to depend on both the sputtering power and the carrier gases used in the sputtering. Generally, the final morphology assumes either (111) or (002) crystallographic orientation. Using Ar sputtering, a cross-over effect from (002) to (111) was observed at intermediate time. The nature of the observed morphological changes is discussed.
In-Situ Observation of Chemical Vapor Deposition of Thin Sige Films by Optical Reflection Interferometry
Authors: Ritter G. , Tillack B. , Weidner M. , Böbel F. G. , Hertel B. 
Published: April 2011

AbstractChemical Vapor Deposition of Si1-x Gex – films on Si (100) and of polycrystalline Si1-x Gex, layers on SiO2 – coated substrates have been performed at a pressure of 200 Pa in the temperature range of 500°C – 800°C, correspondingly. To observe the growth process and to characterize the growing thin films at deposition conditions an optical reflection interferometer (PYRITIERS) has been used. Comparing the data obtained at growth temperature with ex- situ measurements by spectroscopic ellipsometry the temperature dependence of optical constants of SiGe films have been evaluated. The reflectivity measurements during the deposition process allow to study the quality of the heteroepitaxial film, even in the initial stage of epitaxial growth.
Neutron Reflection Studies of Swelling of Chemically End-Grafted Polymer Chains
Authors: Karim Alamgir , Satija S.K. , Gallagher P. , Douglas J.F. , Fetters L.J. 
Published: April 2011

ABSTRACTNeutron reflection is used to compare the swelling of two chemically end-grafted polystyrene brushes having different grafting densities exposed to a theta solvent cyclohexane and to a good solvent toluene. The relative swelling of tie brushes with a variation of solvent quality becomes smaller and the temperature dependence becomes weaker with an increase of grafting density. This type of swelling is very similar to polymer networks where an increase of cross-linking density leads to a decreased range of swelling and diminished dependence of the swelling. Our model density profile fits to the body of both brushes is parabolic in a good solvent so that some fluctuation effects, as found generally in lower density brushes, are obtained as the brush expands.
Neutron and Gamma-Ray Scattering at the University of Missouri Research Reactor Center
Authors: Rhyne James J. 
Published: April 2011

ABSTRACTThe neutron and gamma-ray scattering facilities at the University of Missouri Research Reactor Center include six elastic and inelastic neutron scattering instruments currently in operation and three additional ones under construction. A gamma-ray diffraction and quasi-elastic spectrometer are also available. The Center has no formal user program, but encourages external collaborative work particularly that involves graduate student thesis research.
Phonon Characteristics of High Tc Superconductors from Neutron Doppler Broadening Measurements
Authors: J Trela Walter , Eric lynn J , H Kwei George , Meggers Kay 
Published: April 2011

ABSTRACTStatistical information on the phonon frequency spectrum of materials can be obtained by neutron transmission techniques if they contain nuclei with low energy resonances, narrow enough to be Doppler-broadened. We have carried out measurements using this technique for the doped 2-1-4 system, La2.xBaxCuO4. Two samples with slightly different concentrations of barium, one superconducting, the other not, were examined. Pure Lanthanum Cuprate was also studied. Neutron cross section measurements have been made with high energy resolution and statistical precision on the 60m flight path of LANSCE, the pulsed spallation neutron source at Los Alamos National Laboratory. Measurements on all three materials were made over a range of temperatures from 15K to 300K, with small steps through the critical temperature region near 27K. No significant changes in the mean phonon energy of the lanthanum atoms were observed near the critical temperature of the super-conducting material. It appears however that the mean phonon energy of lanthanum in the superconductor is considerably higher than that in the non-superconductors.
Local Atomic Structure of Plzt Determined by Real-Space Refinement of Neutron-Powder-Diffraction Data
Authors: Teslic S. , Egami T. 
Published: April 2011

ABSTRACTThe local atomic structure of (Pb1-x Lax)( Zry Ti1.y)1.x/4O3 (PLZT) has been examined by means of pair-distribution function (PDF) analysis derived from neutron powder diffraction. We find that atoms are displaced from the atomic sites in the average periodic structure by a significant amount. The directions and magnitudes of the atomic displacements in PLZT are very similar to those found in Pb(Mg1/3Nb2/3)O3 (PMN). The short- and intermediate-range structural changes between ferroelectric, relaxor and antiferroelectric PLZT phases were compared.
Polarized Neutron Scattering Study Of Early Stage Phase Separation in a NI-13AT%AL Alloy
Authors: Staron P. , Kampmann R. , Wagner R. 
Published: April 2011

ABSTRACTThe nucleation stages of the decomposition reaction in a 58Ni-13at%Al alloy at T=450° C have been investigated by means of small- and wide-angle polarized neutron scattering. The use of the 58Ni isotope for the sample preparation tremendously reduced the incoherent scattering of the matrix. This, together with the application of polarized neutrons for experiments at T = 12 K, made the detection of extremely small Ni3Al clusters, not accessible to other microanalytical tools, with diameters D < 1 nm feasible.
Slowing Down of Molecular Reorientations in [Ni(NH3)6](N03)2
Authors: Janik Jerzy A. , Mayer Jacek , Krawczyk Jan , Riste Tormod , Otnes Kaare , Janik Janina M. , Stanek Teresa 
Published: April 2011

ABSTRACTQuasielastic neutron scattering measurements of [Ni(NH3)6](N03)2 were made with two different resolutions of ca. 140 and 30 μeV. The following suggestions are analyzed:1. The NH3 rotational diffusion model is more adequate than NH3 120° jump model.2. Some NH3 groups slow down whereas some rotate rapidly.3. There exists an additional QNS component close to the phase II/phase III transition.
Optical Transitions in Strained Si1−yCy and Si1−x−yGexCy Layers on Si(001)
Authors: Ostena H.J. , Kissinger W. , Weidner M. , Eichler M. 
Published: April 2011

ABSTRACTThe addition of carbon atoms into Si or SiGe layers on Si opens the possibility for strain and bandstructure engineering. In this paper we will investigate the influence of carbon on the optical transitions of Si1−yCy and Si1−x−yGexCy layers grown pseudomorphically on Si(0O1) substrate using solid source MBE incluing also full strain-compensation. The layers were investigated by spectroscopic ellipsometry and electroreflectance spectroscopy for y ≤ 1.2 %. From the numerical derivatives of the measured dielectric constants, we determined the critical points energies E01, E1 and E2 as a function of the carbon content y. This shift was analyzed by measuring and fitting electroreflectance spectra at 80K and ellipsometry data at room temperature, resulting in a weak and nearly linear dependence on the carbon content at all transitions. These dependencies indicate that the interpretation of optical spectra of C-containing alloys can not be performed straightforward by simple interpolating between the appropriate band structures of silicon, germamum and carbon. An analysis based on only strain-induced contributions also does not describe the experimental results correctly. For a description of the observed energy shifts for pseudomorphic Si1−X−yGexCy we have to consider at least strain-induced effects and effects due to alloying.
Strain-Compensation in InAsP/GaInP Multiple Quantum Wells for 1.3 μm Wavelength
Authors: Mei X. B. , Tu C.W. 
Published: April 2011

ABSTRACTWe show that high-quality strain-compensated InAsxP1−x/GayIn1−yP multiple quantum wells (MQWs) can be grown by gas-source molecular beam epitaxy on InP substrates even though the InAsxP1−x quantum wells have a large lattice mismatch (∼ 1.3%) with respect to InP. Very sharp satellite peaks in double-crystal X-ray diffraction and narrow line width in low-temperature photoluminescence (FWHM of 4 meV at 9 K) are obtained from MQWs of up to 50 periods. Strain compensation allows a wide range of the net strain around the ideally compensated point, where the net strain equals zero, without degrading crystalline quality.
Triangular Step Instability and 2D/3D Transition During the Growth of Strained Ge Films on Si(100)
Authors: Chen K. M. , Jesson D. E. , Pennycook S. J. , Mostoller M. , Kaplan T. , Thundat T. , Warmack R. J. 
Published: April 2011

ABSTRACTWe show that an activation energy barrier exists to the formation of wavy step edges due to stress-driven 2D instability. The barrier height and the barrier width depend sensitively on the surface stress anisotropy and step free energy. The large misfit strain of Ge films significantly reduces the barrier by lowering the SB step energy, inducing SA steps to undergo a triangular instability even during low temperature growth of Ge on Si(100). The step instability results in a novel arrangement of stress domains, and the interaction between the domains causes a spatial variation of surface strain with a surprisingly large influence on the energy barrier for island nucleation. Calculations indicate a dramatic enhancement in the nucleation of 3D islands at the apex regions of triangular steps, in good agreement with our experimental measurements.
GexSi1−x Heterojunction Internal Photoemission Structures by Ultra High Vacuum Chemical Vapor Deposition
Authors: Strong R. , Greve D.W. , Schlesinger T.E. , Weeks M.M. , Pellegrini P.W. 
Published: April 2011

ABSTRACTGexSi1−x, heterojunction internal photoemission devices for detection of infrared radiation have been fabricated from films grown by ultra high vacuum chemical vapor deposition (UHV/CVD). Films and devices were characterized by Fourier transform infrared spectroscopy (FTIR), photoresponse, and electrical measurements. Detector efficiencies were found to increase substantially (from ∼ 1.5 to ∼ 20% per eV) as the boron concentration in the absorbing layer was increased from 1×1020 to 2.5×1020 cm−3. Increases in boron concentration beyond 2.5×1020 cm−3 did not significantly improve device performance. This result is attributed to incomplete dopant activation at higher boron concentrations.
Structural and Optical Properties of Sigec Alloys and Multi-Quantum Wells Grown by Rapid Thermal Chemical Vapor Deposition
Authors: Boucaud P. , Guedj C. , Julien F. H. , Bouchier D. , Boulmer J. , Lourtioz J.-M. , Bodnar S. , Regolini J. L. , Finkman E. 
Published: April 2011

ABSTRACTWe have investigated structural and optical properties of SiGeC layers. Bulk and multiquantum wells heterostructures were grown by rapid thermal chemical vapor deposition. The photoluminescence of these structures exhibits two distinct features : deep level photoluminescence associated with localized states and bandedge photoluminescence which gives an indication of the band gap variation due to carbon incorporation in substitutional sites. In the case of multiquantum wells heterostructures, a strong segregation is reported as the growth temperature is decreased. An alternate technique to incorporate carbon in SiGe layers, the pulsed laser induced epitaxy with an excimer laser, is presented. The incorporation of carbon in substitutional sites is evidenced by Raman spectroscopy. As the laser flux is increased, new Raman lines associated to carbon-induced disorder are observed in the spectra.
A Dodson-Tsao Relaxation Approach to The Crystallographic Tilting In (100) Heteroepitaxial Systems
Authors: Riesz Ferenc 
Published: April 2011

ABSTRACTThe tilt of epilayer lattice planes in (100) zinc blende lattice-mismatched heterostructures is calculated numerically using the Dodson-Tsao plastic relaxation model. Tilt is calculated as a function of growth temperature, initial defect density and substrate miscut angle. The results are explained by looking at the time evolution of the excess stresses of the opposing slip systems during strain relaxation.
Parametric Characterization of Plasma Etching Processes
Authors: Mocela Michael T. , Jenkins Mary W. , Sawin Herbert H. , Allen Kenneth D. 
Published: April 2011

AbstractThe analysis of plasma etching processes has been explored for the etching of polysilicon films with CF3Cl/Ar discharges. The etching rate is well fit as a function of the macroscopic plasma parameters (power input, pressure, and composition) using Response Surface Methodology. The parametric expression obtained can be used to examine the sensitivity of the process to the operating conditions, and to optimize the process. The parametric expression also permits comparison of the experimental data with physically meaningful kinetic models.The Response Surface Method allows characterization of a wide parameter space with few experiments. The design of the experimental set is critical to the success of the parametric fit. The parametric expression must account for interactions between parameters, and the expected curvature of the response surface will dictate the required number of data points.
Dry Etching for Nanometer-Scale Fabrication
Authors: Howard Richard E. 
Published: April 2011

AbstractConventional integrated circuit fabrication is currently making the transition from wet to dry etching in the effort to shrink feature sizes to about 1 micron. These plasma etching techniques, though, are not limited to micron dimensions; devices and structures smaller than 100 nm can be made. Using e-beam lithography and reactive ion etching, patterns down to about 20 nm have been made in tri-level stencils and in semiconductor substrates. Working silicon MOSFETs with gate widths down to about 30 nm have also been made. These MOSFET devices are so small that individual electron trapping events can be observed. These devices are being studied to give a better understanding of the physics of electronic conduction in small devices and better define the limits of microfabrication.
Correlation Between Plasma Excited States and Thin Film Characteristics in He-SiH4 PECVD
Authors: Ricard A. , Chouan Y. , Collobert D. 
Published: April 2011

AbstractThe excited states of He-5 % SiH4 PECVD have been analysed by emission and absorption spectroscopy.Variations of spectral line intensities and He(23S) metastable densities have been correlated to the SiH over SiH2 bond ratio and to the deposition speed.The best correlation has been found with the He excited states, specially He(23S) metastables : SiH films without SiH2 bonds have been obtained when the He(23S) densities reach a minimum value.
Chemical Vapor Deposition of Silicon Insulating Films Induced with a Perpendicular Electron Beam
Authors: Zarnani H. , Rocca J. J. , Bishop D. , Cody N. W. , Collins G. J. 
Published: April 2011

AbstractSiO2 and Si3N4 thin films have been deposited at a substrate temperature of 350° using a glow discharge electron beam irradiating perpendicular to the wafer surface. Deposition rates up to 1000 Å/min and 250 Å/min respectively have been obtained. Films deposited over 4 inch diameter silicon wafers show uniformity of 5 percent. The deposition conditions and film properties are discussed.
Plasma Processing Reactor with Surface Magnetic Field Confinement
Authors: Mantei T. D. , Wicker T. E. , Kazmierzak D. 
Published: April 2011

AbstractA plasma reactor has been developed for dry reactive plasma etching and thin semiconductor film deposition. The system combines a multipolar magnetic field layer [1] for charged-particle confinement, and independently controlled substrate biasing. A large volume of dense (1011 cm-3), uniform, quiescent plasma is produced at low working pressure ( 1 mTorr). Anisotropic profiles can be etched into silicon in an SF6-O2 plasma with vertical etch rates ∼l um/min. In a pure silane plasma, good quality polycrystalline silicon films can be deposited at rates 1 to 10 Å/sec., at substrate temperatures 50° to 300° C.
Nondestructive Characterization of RIE Induced Radiation Damage Using Surface Acoustic Wave
Authors: Gilboa H. , Hata W. , O'Donnell K. , Tabib-Azar M. , Das P. 
Published: April 2011

AbstractReactive ion etching (RIE) is extensively used as a high resolution pattern transfer process for fabrication of silicon devices. In this work dry etching radiation damage in p-type boron doped, silicon wafers was investigated using a nondestructive surface acoustic wave (SAW) technique. The transverse acoustoelectric voltage (TAV) is monitored across the silicon wafer which is placed in proximity of a SAW delay line. TAV is developed due to the nonlinear interaction between the electric field accompanying SAW and the free carriers near the silicon surface. TAV versus bias voltage (applied across the semiconductor) was obtained to measure the flatband voltage (VFB) shift. The flatband voltage shift of the etched wafer was determined as a measure of the amount of surface charge introduced into the surface by ion bombardment. SiO2films were etched in C4F8and C2H2with 2 W/cm2input power. The ion energy was determined by the self bias dc voltage developed on the cathode. It is shown that a magnetron RF discharge introduces an order of magnitude less damage than non-magnetron discharge.
Atomic Force Microscope-Based Lithography of Titanium
Authors: Gordon A. E. , Litfin D. D. , Hagedorn M. S. , Chen J. , Fayfield R. T. , Higman T. K. 
Published: April 2011

ABSTRACTAnodization of Ti by high electric fields at the tip of a scanned probe can be used to produce nanoscale features consisting of oxides of Ti. In this manner, Ti can be used as a sacrificial resist for nanoscale lithography by exploiting the etching selectivity differences between Ti and anodized Ti. The anodization was accomplished with an atomic force microscope using Ticoated silicon nitride cantilevers. The anodizing bias voltage is applied to the tip and is independent of the feedback, unlike the scanning tunneling microscope. With this setup we were able to fabricate sub-40 nm lines by direct anodization of Ti. It is also shown that once tip and sample are brought into hard contact, subsequent bending of the cantilever has little effect on the linewidth or thickness of the anodized material.
Fluorinated SiO2 Films For Interlayer Dielectrics In Quarter-Micron Ulsi Multilevel Interconnections
Authors: Homma Tetsuya 
Published: April 2011

AbstractFluorinated SiO2 films for use as interlayer dielectrics in ULSI multilevel interconnections are investigated. The interlayer dielectric film properties and their formation techniques have to meet the following requirements: (1) a low dielectric constant, (2) a high planarization capability, (3) a high capability for narrow gap filling, and (4) a low deposition temperature for low residual stress. To satisfy these requirements, three technologies have been investigated. They are: (i) a fluorinated SiO2 (SiOF) film by room temperature chemical vapor deposition (RTCVD-SiOF) using fluorotrialkoxysilane (FTAS) and pure water as gas sources, (ii) a room temperature liquid phase deposition (LPD) SiO2 film, and (iii) a fluorinated spin-on-glass (SOG) film by fluorotrialkoxysilane vapor treatment (FAST-SOG). The dielectric constant for SiO2 films can be reduced to 3.7 at 1 MHz by the RTCVD and LPD techniques. Although the FAST and RTCVD techniques cannot achieve full planarization, the LPD technique can achieve both global and local planarization because this technique has high capability for selective SiO2 film deposition. The RTCVD, FAST and LPD techniques have shown the possibility to reduce the film formation temperature to room temperature by catalytic reactions, resulting in low residual stress. Other properties of the RTCVD-SiOF, LPD-SiO2 and FAST-SOG films are good enough for the interlayer dielectric film application. The LPD-SiO2 film shows higher endurance properties to moisture than the RTCVD-SiOF and FAST-SOG films.
Real-Time Studies of The Electrocrystallization of Nanoscale Ceramic Superlattices
Authors: Golden Teresa D. , Phillips Richard J. , Switzer Jay A. 
Published: April 2011

ABSTRACTElectrodeposition is unique among thin film deposition techniques, since the current following a potential step from open circuit to a given overpotential (i.e., driving force) provides a real-time, in situ probe of the deposition process. We have used current-time transients to determine the kinetics and dimensionality of growth, and to calculatethe composition profiles of electrodeposited superlattices in the Pb-TI-O system. The transients are indicative of 2D growth, and the height of the 2D monolayer depends on the orientation of the film. A [100] oriented film has a step height of 0.13 nm and a [210] oriented film has a step height of 0.18 nm. These heights correspond to the (400) and (220) d-spacings, respectively. Using a Cottrell analysis, we were able to both calculate and tailor the composition profile in these superlattices. Superlattices grown by pulsing between 70 and 150 mV have square profiles, while those grown by pulsing between 70 and 230 mV have graded profiles.