bluuebunny/crossref_metadata_2025_split huggingface dataset:
Photoconductive Properties Of A GaAs-A1GaAs Quantumwell Infrared
Photodetector
Authors: Ueda Toshiyuki , Shinohara Koji , Miyamoto Yoshihiro 
Published: March 2011

ABSTRACTWe investigated the conduction mechanism and performance of GaAs-A1GaAs
quantum-well infrared photodetectors and proposed a conduction model
consisting of Poole-Frenkel-like emission from wells and carrier relaxation
wells. The model agrees with the measured photocurrent and dark current. The
detector's noise current is given by a simple shot noise formula. Analysis
has shown that the photocurrent and the noise current are inversely
proportional to the barrier width, while the dark current is inversely
proportional to the square of the barrier width.
Growth Condition Dependence Of Rheed Pattern From GaAs (111)B
Surface
Authors: Yang K. , Li W. , Taylor A. P. , Xiao Q.-F. , Schowalter L. J. , Laurich B. K. , Smith D. L. 
Published: March 2011

ABSTRACTA 3-dimensional phase diagram is introduced to describe the dependence of
the RHEED pattern from GaAs(111)B surface on growth conditions. The 2×2,
transitional(1×1), and √19×,√19 surface reconstructions correspond to
different zones in the phase diagram. A equation is given for the planes
that separate these zones, which fit experimental data well. Homoepitaxial
films on GaAs(111)B grown in the 2×2 region generally have bad crystal
quality as determined by the ion channeling, and growth in the √19×√19
region generally yields rough surface morphology. At higher substrate
temperatures (∼ 650 °C), featureless films with minimum ion channeling
yields of less than 4% are achieved.
Quest for Compact Blue Lasers for Optical
Memories
Authors: Bhargava R. N. 
Published: March 2011

ABSTRACTA short wavelength laser offers unique opportunities in high density optical
recording as well as in laser printing. To achieve a compact blue laser, the
current effort worldwide is primarily concentrated on achieving
well-conducting p-type ZnSe and fabricating quantum well heterostructures so
as to achieve a low threshold laser at room temperature. The recent
milestone ‘an injection blue laser below room temperature’ gives us
confidence that indeed we are on the right path. In photopumped lasers in
various II-VI heterostructures, thresholds at room temperature comparable to
the theoretical limit have been reported. This not only reinforces that
indeed a room temperature injection laser is possible but when combined with
earlier electron-beam pumped laser results, a scanned compact laser is also
feasible.In recent years several breakthroughs have demonstrated that an infrared
emitting GaAs laser can be used to generate blue light through efficient
second harmonic generation (SHG) in certain non-linear optical materials.
Recent exciting results on SHG of GaAs lasers in KTP grating waveguides
resulted in a blue laser with output power in the range of several
milliwatts. Alternative schemes such as upconversion lasers and SHG in III-V
quantum wells structures are presented.In summary, various efforts to achieve compact blue lasers and their
availability in the near future are presented.
P-type Conduction in Bulk ZnSe by Nitrogen
Ion-Implantation
Authors: Jin M. K. , Yasuda T. , Shahzad K. , Merz J. L. 
Published: March 2011

ABSTRACTP-type conduction in bulk ZnSe has been achieved using 1×1016
cm−2 nitrogen (N) ionimplantation followed by a high
temperature rapid thermal annealing. Room temperature Hall effect
measurements of the sample show that the hole concentration is
∼1×1017 cm−3, and the mobility is ∼30
cm2/V-s. Photoluminescence (PL) measurements were performed to
study the optical behavior of the samples, and the results show that the ion
implantation damage can be partially repaired by thermal annealing at 900°C
or higher. Thermal degradation and recovery of the ion-implantation damage
were studied as a function of the annealing temperature.
Optoelectronic Memory Element with the Application of
Photoconducting and Electroluminescent thin Film Devices
Authors: Porada Zbigniew W. 
Published: March 2011

ABSTRACTAn optoelectronic memory element was constructed from two photoconducting
(PC) and two electroluminescent (EL) devices. Between one EL device and one
PC device an optical feedback was provided, so that these two components
constituted a bi-stable system. Experimental details of preparation of the
PC-EL type thin film systems and results of investigations of the memory
element are presented.
Measurements of Photo-Induced Changes in Conjugated
Polymers
Authors: Seager Carleton H. , Sinclair Michael B. , Branch D. Mc , Heeger A. J. , Baker G. L. 
Published: March 2011

ABSTRACTWe have used the highly sensitive technique of Photothermal Deflection
Spectroscopy (PDS) to measure changes in the infra-red absorption spectra of
MEHPPV, P3HT and Polydiacetylene-4BCMU induced by pumping these polymers
with light above the π - π* transition energy. In contrast to previous
chopped light transmission measurements of these effects, the PDS technique
can directly measure the buildup or decay of the absorption coefficient, m,
on the time scale of seconds to days. In the case of MEHPPV we observe that
above-gap light causes the appearance of a broad infra-red peak in α, which
continues to grow-in hours after the pump light is first applied. For this
polymer the general shape of the absorption spectra in the unpumped state
mimics the photo-induced changes, suggesting that remnant photo-induced
states determine the maximum transparency observed under normal experimental
conditions. For P3HT and to a lesser extent, MEHPPV, we also observe
irreversible photo-induced absorption components which we tentatively
identify with photo-induced oxidation of the polymer matrix.
Subgap Absorption in Conjugated Polymers
Authors: Sinclair M. , Seager C. H. , McBranch D. , Heeger A. J. , Baker G. L. 
Published: March 2011

ABSTRACTAlong with χ(3), the magnitude of the optical absorption in the
transparent window below the principal absorption edge is an important
parameter which will ultimately determine the utility of conjugated polymers
in active integrated optical devices. With an absorptance sensitivity of
< 10-5, Photothermal Deflection Spectroscopy (PDS) is ideal
for determining the absorption coefficients of thin films of “transparent”
materials. We have used PDS to measure the optical absorption spectra of the
conjugated polymers poly[1,4-phenylenevinylene] (and derivitives) and
polydiacetylene-4BCMU in the spectral region from 0.55 eV to 3 eV. Our
spectra show that the shape of the absorption edge varies considerably from
polymer to polymer, with polydiacetylene-4BCMU having the steepest
absorption edge. The minimum absorption coefficients measured varied
somewhat with sample age and quality, but were typically in the range 1
cm-1 to 10 cm-1. In the region below 1 eV,
overtones of C-H stretching modes were observed, indicating that further
improvements in transparency in this spectral region might be achieved via
deuteration or fluorination.
Vibrational Overtone Spectra in Polymeric Thin
Films
Authors: Skumanich Andrew , Moylan Christopiier 
Published: March 2011

ABSTRACTWith the enhanced sensitivity of Photothermal Deflection Spectroscopy (PDS),
vibrational overtone spectra have been obtained in organic thin films for
the first time, covering the range from the near IR to the visible (0.4 - 2
eV). The absorption spectra of polycarbonate, for instance, exhibits C-I1
stretch modes for Δn> I where n is the
vibrational quantum level. Previous measurements were constrained to either
long fibers, which pose the problem of various scattering losses not related
to absorption, or to a restricted wavelength region in the visible
accessible by dye laser sources. The unparalleled sensitivity of PDS allows
precise determination of frequency, lineshape and intensity of the various
modes, even for films ∼10μm thick over a broad energy range. The overtone
spectra can be used as a probe of various basic molecular properties. In a
manner similar to NMR spectroscopy, it is possible to study specific atomic
bonds.
Scanning Tunneling Microscopy Studies of Metal/Metal Epitaxial Growth.
Authors: Chambliss David D. , Chiang Shirley , Wilson Robert J. 
Published: March 2011

AbstractThe morphologies of submonolayer films of Ni, Fe, Au, and Ag deposited on Au(111) at room temperature are studied using scanning tunneling microscopy (STM). The structures of steps and islands on length scales up to ˜3000Å are examined to determine processes of atomic motion and island nucleation. In all cases the deposited atoms move rapidly at room temperature and their aggregation is affected by the Au(111) “herringbone” reconstruction. Ni and Fe aggregate to form island arrays with regular spacing, which are nucleated at “elbow” sites of the herringbone pattern. Au forms fewer islands, showing these atoms are less likely to stick at these elbow sites. Ag forms a complex structure of monolayer-high fingers which reflect the interaction of diffusion-controlled aggregation with energetic differences defined by the reconstruction. These studies make it clear that the final structure of an ultrathin metal film can depend sensitively on fine details of atomic structure in the substrate.
Molecular Dynamics Study of Thermal Disorder in a Bicrystal Model
Authors: Nguyen Tue , Ho Paul S. , Kwok Thomas , Nitta Cynthia , Yip Sidney 
Published: March 2011

AbstractThis work studies a (310) θ = 36.86° <001> symmetrical-tilt bicrystal model using an Embedded Atom Method aluminum potential. Based on explicit results obtained from the simulations regarding structural order, energy, and mobility, we find that our bicrystal model shows no evidence of pre-melting (complete melting below Tm). Both the surface and the grain-boundary interface exhibit thermal disorder at temperatures below Tm, with complete melting occurring only at, or very near, Tm. Concerning the details of the onset of melting, the data show considerable disordering in the interfacial region starting at about 0.93 Tm. The interfaces exhibit metastable behavior in this temperature range, and the temperature variation of the interfacial thickness suggests that the disordering induced by the interface is a continuous transition, a behavior that has been predicted by a theoretical analysis.
Correlations Between Grain Boundary Structure and Energy
Authors: Merkle K. L. , Wolf D. 
Published: March 2011

AbstractHigh-resolution electron-microscopy (HREM) and computer simulations of <110> tilt grain boundaries (GBs) in Au are used to investigate correlations between atomic-scale GB structure and energy. The energies calculated for a variety of symmetric and asymmetric GBs suggest that asymmetric GB-plane orientations are often preferred over symmetric ones. The experimentally observed faceting behavior agrees with the computed energies. Computer simulations indicate general interrelations between GB energy and (i) volume expansion and (ii) the number of broken bonds per unit area of GB. These atomic-scale microstructural GB parameters, as evaluated from HREM observations, are compared to simulation results.
The Mechanical Behavior of a Grain Boundary-Rich (Nanocrystalline) Metal
Authors: Mayo M. J. 
Published: March 2011

AbstractNanocrystalline copper has been produced by two different techniques -- gas phase condensation and mechanical wear. Both nanocrystalline coppers have hardnesses and strain rate sensitivities that are greater than those of conventional, large-grained copper. These properties differences are tentatively explained on the basis of the two routes by which grain boundaries traditionally influence plastic deformation: by acting as barriers to dislocation glide, and by providing the vacancy sources and sinks necessary to facilitate diffusional flow. Additionally, there are notable differences in the mechanical properties of the two nanocrystalline coppers. Although the materials appear quite similar microstructurally, nanoindentation experiments show that the wear debris is 50% harder and 3 times more strain rate sensitive than the gas phase condensation-produced copper. These differences indicate that the microstructures are probably not as similar as first perceived, and that a previously overlooked microstructural feature may be influencing deformation in one or both of the materials.
Analysis of Brittle Intergranular Crack Propagation During Stress Corrosion
Authors: Jones Russell H. 
Published: March 2011

AbstractCrack growth rates during intergranular stress corrosion, in materials such as Fe in Ca(NO3)2 at +750 mV (SCE), appear to exceed rates which can occur by dissolution and ion transport within the crack. Brittle crack jumps induced by a corrosion or stress corrosion process, and which magnify the dissolution supported crack velocity by a factor of up to 103, could explain this behavior. Hydrogen can induce these very fast crack growth rates, but these rates have been obtained at electrochemical potentials where H reduction is not thermodynamically possible. Other possible mechanisms for this accelerated crack growth include: 1) intergranularcorrosion altered tearing modulus, 2) grain boundary dealloying, or 3) adsorption induced brittle fracture. Examination of each of these mechanisms suggests that intergranular corrosion could reduce the tearing modulus through changes in the crack shape. However, crack opening analysis clearly shows that the crack tip is shielded from the applied stress intensity and that an embrittlement process which reduces the interface toughness is need for brittle intergranular crack jumps to occur. Further research is in progress to identify the source of this embrittlement.
Structural Relaxation by Precipitation in Al-Li I. Growth Kinetics of Precipitates
Authors: Kamel R. , Gobran N. K. , Danial M. M. 
Published: March 2011

AbstractChanges in electrical resistance measured by the four probe method was adopted as a structure sensitive physical property used to trace changes in the atomic microstructure below and above the δ'-solvus line in the Al-Li binary alloys. The kinetics of the growth and dissolution of δ' phase (Al3Li) and the formation of δ phase (AlLi), below and above δ'-solvus line, during the coarsening process were studied by isochronal and isothermal investigations. The diffusional growth of δ'-phase, below the δ'-solvus line, was found to be activated by 0.24 eV. Interpretation of the results showed that this energy involved two events during the coarsening process. The first event seemed to be a breakdown of the bonding between the vacancy-Lithium pair and the second event involved the transport of Li atoms to Al-particles to coarsen δ'; (Al3Li) particles. Furthermore, the study of the temperature dependence of electrical resistance of the stable phases δ' and δ of Al-Li alloys was found to be accompanied by difference in the temperature coefficient of the electrical resistance and was attributed to the change in structure of the two phases considered.
Precipitation at Transformation Interfaces
Authors: Khalid F. A. , Edmonds D. V. 
Published: March 2011

AbstractAlloy carbide precipitation associated with the transformation interface between austenite and ferrite, and austenite and pearlite in steels can result in a fine particle dispersion that can contribute significantly to strength in a wide range of commercial carbon steels. Studies of this precipitation reaction are hindered by the fact that the transformation interface is lost upon cooling to room temperature, either by further transformation or by decomposition of the residual austenite phase to martensite. In the present work this has been avoided by developing an alloy in which the precipitation reaction occurs, but in which the austenite is stabilised to room temperature, thus allowing a detailed examination by TEM and APFIM techniques of the interfacial region.
Grain Boundary Chemistry in Al-Cu Metallizations as Determined by Analytical Electron Microscopy
Authors: Michael J. R. , Romig A. D. , Frear D. R. 
Published: March 2011

AbstractAl with additions of Cu is commonly used as the conductor metallizations for integrated circuits (ICs). As the packing density of ICs increases, interconnect lines are required to carry ever higher current densities. Consequently, reliability due to electromigration failure becomes an increasing concern. Cu has been found to increase the lifetimes of these conductors, but the mechanism by which electromigration is improved is not yet fully understood. In order to evaluate certain theories of electromigration it is necessary to have a detailed description of the Cu distribution in the Al microstructure, with emphasis on the distribution of Cu at the grain boundaries. In this study analytical electron microscopy (AEM) has been used to characterize grain boundary regions in an Al-2 wt.% Cu thin film metallization on Si after a variety of thermal treatments. The results of this study indicate that the Cu distribution is dependent on the thermal annealing conditions. At temperatures near the θ phase (CuAl2) solvus, the Cu distribution may be modelled by the collector plate mechanism, in which the grain boundary is depleted in Cu relative to the matrix. At lower temperatures, Cu enrichment of the boundaries occurs, perhaps as a precursor to second phase formation. Natural cooling from the single phase field produces only grain boundary depletion of Cu consistent with the collector-plate mechanism. The kinetic details of the elemental segregation behavior derived from this study can be used to describe microstructural evolution in actual interconnect alloys.
Grain Boundary Structure and Diffusion Induced Grain Boundary Migration
Authors: King A. H. 
Published: March 2011

AbstractWe present a review of systematic studies of diffusion induced grain boundary migration (DIGM). The results are compared with structural models for the grain boundaries in order to assess the effects of structure upon DIGM. The nucleation of DIGM is also assessed in the light of grain boundary structure and it is demonstrated that changes of grain boundary solute concentration can induce large enough energy changes to drive novel grain boundary dissociation reactions.
Ultra-Fast Melting and Solidification Behaviour of Amorphous and Crystalline Silicon
Authors: Cullis A.G. , Webber H.C. , Chew N.G. 
Published: March 2011

ABSTRACTSubnanosecond ultra-violet radiation pulses are used to produce relatively thick, large area amorphous layers onSi crystals by transient melting and solidification. The different behaviours of (001) and (111) Si orientations are highlighted. Observations of crystal growth phenomena during solidification at velocities lower than required for amorphization are correlated with theoretical predictions. Computer modelling of heat flow in amorphous silicon is refined.
Raman Scattering in Ultra Heavily Doped Si and Ge: The Dependence on Free Carrier and Substitutional Dopant Densities
Authors: Compaan A. , Contreras G. , Cardona M. , Axmann A. 
Published: March 2011

ABSTRACTWe present the results of a systematic study of phonon softening due to free electrons and holes in extremely heavily doped Si and Ge. Metastable concentrations of Bi, Sb, As, P, Al and B were implanted and pulsed laser annealed (ruby or XeCl) to produce substitutional concentrations up to 4×1021 cm−3 . We find softening of the zone center optic phonon of as much as ˜5% in p-type Ge, ˜5.4% in p-type Si, and 2% in n-type Si. The shifts are explained by phonon coupling to single particle electronic excitations. In addition we discuss the density dependence of the Raman-active vibrational local modes of P and Al in Ge and of B in Si which we demonstrate can provide a convenient measure of substitutional concentrations of these low mass dopants.
Instability at the Melting Threshold of Laser Irradiated Silicon as the Underlying Origin of the Ripples Formation
Authors: Combescot M. , Bok J. , Guillaume C. Benoit A La 
Published: March 2011

ABSTRACTThe increase of reflectivity associated with a strong decrease of the laser penetration depth at the melting threshold of laser irradiated silicon induces a symmetry breaking with formation of a mixture of solid and liquid regions. We present a steady state solution in the case of solid and liquid stripes and we show that the liquid regions are slightly hotter than solid ones in contradiction with the previous idea of an undercooled liquid. The pattern size has to be smaller than a critical value of the order of the laser penetration depth, and can be selected by additional interference and diffraction effects.
Initial Obsevation of the Crystal-Amorphous Transition and the Formation of Ripple Patterns on Silicon Induced by 7 ps Pulses at 1.05 µm
Authors: Boyd Ian W. , Moss Steven C. , Boggess Thomas F. , Smirl Arthur L. 
Published: March 2011

ABSTRACTWe describe our preliminary observations of the interaction of short pulse 1 µm radiation with crystalline silicon. In particular we find that for 7 ps pulses, but not for 46 ps pulses, the crystal-amorphous transition can be induced on the Si surface. Additionally, we have measured the single shot melting threshold for c-Si to be 0.6 ± 0.2 J cm-2 for 7 ps pulses. The formation of ripple patterns and other surface structures with pulses as short as 4 ps is also reported.
Wetting Angles and Surface Tension in the Crystallization of Thin Liquid Films
Authors: Yablonovitch Eli , Gmitter T. 
Published: March 2011

ABSTRACTThe behaviour of thin liquid films is known to be dominated by surface tension forces. We show that the crystallization of thin liquid films requires that two wetting angle conditions be simultaneously satisfied: (i) relating to the liquid–vapour interface and (ii) relating to the crystal–liquid interface. The balance between capillary pressure and thermal gradient forces shows that the equilibrium freezing point of thin films is actually depressed below the bulk freezing point. The magnitude of the effect is 1°K in an 800 Å thick film. These observations suggest that small–scale thickness fluctuations may be responsible for the initiation of sub–grain boundaries in the growth of crystalline silicon films.
Formation of Buried Oxide in Silicon by High-Dose Oxygen Implantation, and Application of this Technology to CMOS Devices
Authors: Izumi K. , Omura Y. , Nakashima S. 
Published: March 2011

ABSTRACTSIMOX (Separation by Implanted Oxygen) technology has been developed for realization of oxygen-ion implanted SOI. The distribution of implanted oxygen was analyzed by Auger electron spectroscopy and Rutherford backscattering spectroscopy. The properties of the silicon oxide formed by oxygenion implantation were investigated by infrared spectra, capacitance-voltage characteristics, dielectric strength, and dielectric constants. The crystallinity of the top layer silicon and of the epitaxially-grown silicon layer was deter mined by electron-beam diffraction. An electric-field-shielding effect was observed in the polycrystalline silicon region which was formed between the top layer silicon and the buried oxide. High-speed digital and high-voltage analogue CMOS LSIs, a 1kb CMOS RAM and a BSH LSI, were successfully fabricated using SIMOX technology.
Comparison of Pulsed Laser and Furnace Annealing of Nitrogen Implanted Silicon
Authors: Smith T. P. , Stiles P. J. , Augustyniak W. M. , Brown W. L. , Jacobson D. C. , Kant R. A. 
Published: March 2011

ABSTRACTFormation of buried insulating layers and redistribution of impurities during annealing are important processes in new semiconductor device technologies. We have studied pulsed ruby laser and furnace annealing of high dose (D>1017 N/cm2) 50 KeV nitrogen implanted silicon. Using He Back scattering and channeling, X-ray diffraction, transmission electron microscopy, and infrared transmission spectroscopy, we have compared liquid and solid phase regrowth, diffusion, impurity segregation and nitride formation. As has been previously reported, during furnace annealing at or above 1200C nitrogen redistributes and forms a polycrystalline silicon nitride (Si3N4 ) layer. [1–4] In contrast, pulsed laser annealing produces a buried amorphous silicon nitride layer filled with voids or bubbles below a layer of polycrystalline silicon.