bluuebunny/crossref_metadata_2025 huggingface dataset:
O Brasil nas ruas e longe do mundo: como a crise político-econômica levou ao colapso da política externa brasileira
Authors:   Fundação Getúlio Vargas, Casarões Guilherme
Published: March 2022

Após uma década de crescente envolvimento e projeção internacionais, que levaram o Brasil a ser considerado uma potência emergente, desde 2013 o país vive um prolongado período de retração internacional. Neste capítulo, argumentamos que a política externa passou a ser conduzida não mais pelos objetivos e interesses de longo prazo do país, tendo em vista as possibilidades globais, mas pela conjuntura doméstica imediata. É possível identificar três grandes fases nesse processo, que coincidem com as estratégias dos governos de turno: (1) a fase de retração, em que Dilma Rousseff buscou rebaixar o status brasileiro de potência emergente (e, portanto, detentora de certos compromissos internacionais ambiciosos) para o de potência média, de ambições mais limitadas e geralmente circunscritas a temas de baixa política (como comércio, meio ambiente e direitos humanos); (2) a fase de normalização, em que Michel Temer buscou garantir a legitimidade e a sobrevivência de seu frágil governo transitório por meio do reforço da agenda comercial, com vistas à recuperação econômica do país; (3) a fase de redefinição, em que Jair Bolsonaro, político de extrema direita, fortemente antissistema, buscou reposicionar o Brasil como nação cristã e conservadora por meio da submissão dos objetivos internacionais do país à nova correlação de forças que chegou ao poder em 2018. Buscamos contribuir aos estudos de política externa brasileira ao recontar a história recente sob o ângulo dos constrangimentos domésticos à projeção internacional do Brasil.
Rituales fúnebres afectivos frente a la crisis del sida en Buenos Aires de los años 80
Authors:   CONICET/UNSAM, Suarez Marina Fernanda
Published: March 2022

Durante los años 80 en Buenos Aires comenzaron a multiplicarse los casos de una enfermedad mortal que afectaba especialmente a jóvenes. Silenciosa y desconocida, generó pánico y estigmatización hacia quienes la contraían ya que no se conocía las verdaderas formas de contagio y la muerte de los infectados resultaba inminente. En esos años, el sida fue catalogado como “peste rosa” o “un justo castigo divino” por sectores vinculados a la iglesia que acusaban a los enfermos de prácticas promiscuas y vergonzosas. El presente trabajo se propone describir el impacto del HIV/sida en la comunidad del underground porteño y en particular analizar el caso del actor Batato Barea, para pensar algunas cuestiones diferenciales tanto de la enfermedad como de la manera que encontró la comunidad artística y LGTB de lidiar colectivamente con ella, mientras ni el Estado ni la comunidad científica internacional articulaban planes de acción efectivos para su cura. En consonancia con este planteo, indagaremos puntualmente en la ceremonia fúnebre de Batato Barea y su vínculo con los velorios festivos, en torno al HIV/sida, que se efectuaron en la comunidad artística en esos años. Analizaremos su impronta característica en relación a otros modos colectivos de enfrentar la muerte y reclamar por una cura, en los funerales del grupo activista ACT UP (Coalición del sida para desatar el poder), realizados en Estados Unidos y Europa. En suma, postulamos que este tipo de funerales festivos, como el de Batato Barea, buscaban preservar la integridad anímica, sobre todo, de quienes estando infectados luchaban contra la enfermedad.
Os terremotos brasileiros: uma breve história econômica no século XXI
Authors:   Fundación Getúlio Vargas - Pontificia Universidad Católica de São Paulo, Villaverde João
Published: March 2022

El articulo describe la historia reciente de la economía brasileña, trazando la trayectoria seguida desde el gobierno de Fernando Henrique Cardoso hasta el momento actual, pasando por los años de gobierno del Partido de los Trabajadores, destacando sus políticas sociales y sus efectos.
Multi-period activity, the European Marine Science Park, Dunstaffnage, Argyll
Authors: Ellis Clare , Hamilton Derek , Ramsay Susan , Boyle Angela , MacSween Anne , Cruickshanks Gemma , Ballin Torben Bjarke
Published: March 2022

Excavation in advance of development of the European Marine Science Park at Dunstaffnage in Argyll (NGR: NM 87878 34063) revealed multi-phased activity from the Neolithic into the Early Historic period. An irregular row of firepits, interpreted as funerary pyres, was orientated east–west and incorporated an infant inhumation and a cobble path. Dating of charcoal revealed that the fire-pits were probably in use for a number of generations during the Late Iron Age. The fire-pits were located on the edge of wet ground and it is postulated that these were deliberately located on what may have been perceived as a liminal boundary to aid passage into the afterlife. Activity shifted to the drier ground in the Early Historic period, late 7th to 9th century, in the form of an extended farmstead within which barley and oats were being dried in a kiln. Evidence for possible barns and/or houses survives in the form of a post-hole structure, a post-built wattle and daub structure, at least one basket pit boiler and a number of cobble hearths. One pit contained ten metal artefacts thought to be derived from agricultural implements or a dismantled structure. The duration of use of the farmstead appears to have been relatively short and it may have been seasonally occupied.
Implementation of VAR (Virtual Augmented Reality) based Educational Games in Harapan Bunda Islamic Kindergartens in Semarang City
Authors: Kurniasih Eem , Haryati Yuli , Masduki Lusi Rachmiazasi , - -
Published: March 2022

Due to the contemporary state of game - based learning, the advancement is so rapid that one criterion is that kindergarten children are active playing games on the side - lines of their parents' busy lifestyles; this is absolutely a chance to generate game - based learning that are tailored to the developmental level of kindergarten children, so that educational games are able to be produced. enhance kindergarten children's sensorimotor abilities since this technology may offer virtual and augmented reality that appeals to toddlers and is capable of increasing kindergarten children 's studying enthusiasm, research methodologies based on the ADDIE R & D model (Analysis, Design, Develop, Implementation, & Evaluation) In this second year, product validation was obtained by 91 % of material expertise, 87 % of medium expertise, and 95 % of teacher response, indicating that such a game-based learning product is appropriate for use in kindergarten classroom studies, Based on the findings of the first year, the product has been upgraded appropriately and efficiently accordance to preschool or childhood years cognitive ability, and the average posttest teacher with education game is 84,29, which is in the excellent category.
Implementation and Evaluation of Using Digital Book Media with Contextual Approach to Learning Citizenship Education Material in University
Authors: Widodo Suwarno , dia Muh , Buchori Achmad , Wardani Theodora Indriati
Published: March 2022

The objective of this research is to examine the procedure of advancement, feasibility, amount of accuracy, and medium efficacy of an online book with CTL (Contextual Teaching and Learning) to increase university students' problem-solving capabilities in civic education courses. The R&D research method was used, along with the ADDIE development model. The subject of the research are college students of civic education at Universitas PGRI Semarang, USM and IVET University in the academic year 2019/2020. After qualified media and material validation, this product was tested for gaining the research hypothesis using a one-party t-test, which revealed tcount = 6.320 and ttable = 2.004; if tcount > ttable, 6,324 > 2,004, then Ho is rejected. As a result, it can be reached the conclusion that students who use media digital books with the CTL learning model are effective in resolving citizenship education problems than students who use traditional learning. So that in the second year, more universities in Semarang will use this digital citizenship book, and it is hoped that more than 90% of students and lecturers will be interested in using it.
Platelet plasma membrane in subjects with primary nocturnal enuresis: Effect of desmopressin
Authors: Giorgi Pier Luigi , Fiorini Rosamaria , Biraghi Maurizio , Kantar Ahmad
Published: July 2002

Summry— Plasma membrane fluidity of platelets (PLT) obtained from subjects with primary nocturnal enuresis (PNE) and healthy controls was investigated before and after addition of desmopressin (DDAVP). Membrane fluidity was studied by measuring steadystate fluorescence anisotropy of 1‐(4‐trimethylammoniumphenyl)‐6‐phenyl‐1, 3, 5‐hexatriene incorporated into PLT plasma membrane. Our results show an increase in membrane fluidity at the surface level of PLT from subjects with PNE. Moreover, the addition of DDAVP induces a stable and significant decrease of membrane fluidity in both groups. These results suggest alterations of the lipid order in the exterior part of the PLT plasma membrane from patients with PNE.
Superconductivity and paramagnetism in ErBa2Cu3O7−y
Authors: Xu Yunhui , Guan Weiyan
Published: July 2002

We report detailed magnetic susceptibility and magnetization studies for the high Tc oxide superconductor ErBa2Cu3O7−y. The magnetic susceptibility χ of ErBa2Cu3O7−y follows a Curie–Weiss law both above and below Tc with the magnetic moment Peff=9.2μB, which is close to that of 9.58μB deduced from the ground state of Er3+ ion. Magnetization data at various temperatures have revealed a very large magnetic hysteresis. By analyzing the hysteretic magnetization data, we obtain the critical current density Jc(H) and the reversible magnetization Me(H) at 4.2 K. The saturation of Me in high fields at low temperature can be explained by the standard theory of paramagnetism with a Brillouin function. We find that superconductivity and paramagnetism in ErBa2Cu3O7−y exist largely independently of one another.
Solid phase epitaxial regrowth of Si1−xGex/Si strained-layer structures amorphized by ion implantation
Authors: Chilton B. T. , Robinson B. J. , Thompson D. A. , Jackman T. E. , Baribeau J.-M.
Published: July 2002

Strained-layer structures consisting of ∼30–35 nm Si1−xGex (x=0.16–0.29) and 33 nm Si deposited by molecular beam epitaxy on a (100)Si substrate have been amorphized by ion implantation at 40 K with 120 keV As+. Rutherford backscattering/channeling measurements using 2 MeV He+ ions have been used to measure the thickness of the amorphous layer and monitor the subsequent epitaxial regrowth occurring as a result of annealing at 560–600 °C. Angular scans across the {110} planar channels indicate that the initial crystallinity and strain was recovered for x=0.16; however, for x=0.29 crystal quality was greatly reduced and the coherency at the substrate-alloy layer interface was destroyed.
Long-range [111] ordering in GaAs1−xPx
Authors: Jen H. R. , Cao D. S. , Stringfellow G. B.
Published: July 2002

The observation of ordering in GaAsP alloys is reported. The CuPt structure with ordering along the 〈111〉 directions on the anion sublattice was observed by transmission electron diffraction patterns in GaAs1−xPx alloys at compositions of x=0.3 and 0.4. Only two of the four CuPt variants were observed. The degree of ordering along the 1/2[1̄11] direction is higher than for the other variant, ordered along the 1/2[11̄1] direction. In addition, the degree of ordering decreases when x is reduced from 0.4 to 0.3.
Production of disilane and silyl sticking coefficients during plasma-enhanced chemical vapor deposition of hydrogenated amorphous silicon
Authors: McCaughey Michael J. , Kushner Mark J.
Published: July 2002

The rate of production of disilane (Si2H6) in silane (SiH4) plasmas by gas phase and surface-catalyzed processes is examined. The discussion is based on results from plasma chemistry and surface deposition computer models. The surface model simulates the adsorption of silane radicals from the plasma on a growing amorphous silicon film and the subsequent desorption from the surface of the nonadhering SiH3 radicals as Si2H6. The rate of generation of Si2H6 from the surface reactions is compared to the rate of generation due to plasma reactions. We find that for conditions which are typical of those used for deposition of amorphous silicon, production of disilane is likely dominated by surface-catalyzed processes. The rate of production, though, depends on the sticking coefficient of SiH3, which we find to be a function of plasma conditions.
Quantum-confined field-effect light emitters with high-speed switching capability
Authors: Kan Y. , Yamanishi M. , Okuda M. , Mukaiyama K. , Ohnishi T. , Kawamoto M. , Suemune I.
Published: July 2002

The field control of luminescent characteristic is observed with the three-terminal quantum-confined field-effect light-emitting device at a high temperature of 100–300 K. The modulation scheme caused by the field-induced change in radiative lifetime without change in carrrier density is demonstrated in the practical device. A fast switching of the spontaneous emission intensity free from lifetime limitation is obtained.
Period doubling in directly modulated InGaAsP semiconductor lasers
Authors: Chusseau Laurent , Hemery Eric , Lourtioz Jean-Michel
Published: July 2002

We report on period doubling in a directly modulated InGaAsP semiconductor laser at 1.3 μm. This behavior is obtained for modulation frequencies between fr and 1.6fr, where fr is the laser resonant frequency measured under weak current modulation. The domain of period doubling as well as the time responses of the optical output is well interpreted using a rate equation model.
Extremely high electron mobility in a GaAs-GaxIn1−xP heterostructure grown by metalorganic chemical vapor deposition
Authors: Razeghi M. , Defour M. , Omnes F. , Dobers M. , Vieren J. P. , Guldner Y.
Published: July 2002

On studying the magnetoresistivity of GaAs-GaInP heterostructures grown by low-pressure metalorganic chemical vapor deposition in magnetic fields up to 12 T and at liquid-helium temperatures, we have observed extremely high electron mobilities. Using the persistent photoconductivity effect, by illumination with red light, we reached a mobility of 780 000 cm2/(V s) at an electron density of 4.1×1011 cm−2. This high electron mobility is confirmed by cyclotron resonance measurements.
Direct areal density measurement by activation technique for plastic hollow shell implosion experiments
Authors: Nakaishi H. , Miyanaga N. , Setsuhara Y. , Azechi H. , Takagi M. , Saito M. , Yamanaka M. , Yamanaka T. , Nakai S. , Kobayashi K. , Kimura I.
Published: July 2002

The fuel areal density ρR measurement of imploded plastic hollow shell targets by use of a neutron activation technique is reported. Silicon was doped as an activatable tracer into a hollow shell of tritium-contained deuterated polymer(CDTSi). This target was imploded by 0.53 μm Nd:glass laser light and the induced radioactivity of 28 Al was measured with a β-γ coincidence counting system. The collection efficiency was calibrated by the use of radioactive tracer 24 Na and was verified by comparing the estimated ρR with that simultaneously measured by a knock-on method.
Superhigh-rate plasma jet etching of silicon
Authors: Bárdos L. , Berg S. , Blom H-O.
Published: July 2002

A new, very high rate dry etching system based on the plasma jet principle is presented. In this device the active gases are fed into the processing vacuum chamber through a small 0.5 mm i.d. nozzle. By applying radio frequency power (13.56 MHz) a hollow cathode discharge is created inside the nozzle. This discharge will be very intense and effective in dissociating the gas mixture used for reactive etching. A jet stream of radicals will be formed. By placing a silicon substrate in front of this jet stream it is possible to perform very high rate reactive etching of silicon. Etch rates as high as 0.1–0.2 mm/min can be easily obtained. It is demonstrated that the etch rate and the width of the etching crater are sensitive to different processing conditions. The width of the etching crater may be smaller than the diameter of the nozzle exit under certain conditions.
Quantum-confined Stark effect in very small semiconductor crystallites
Authors: Hache F. , Ricard D. , Flytzanis C.
Published: July 2002

Experimental study of the change δα in the absorption spectrum due to a static electric field is reported for very small CdSSe crystallites. We observe oscillations of δα as a function of the wavelength, which are well explained as a Stark effect for the quantized electronic levels. A perturbation calculation is performed, which gives good theoretical fits of the experimental curves.
Demonstration of all-optical phase modulation in polydiacetylene waveguides
Authors: Thakur M. , Krol D. M.
Published: July 2002

We present the first demonstration of all-optical phase modulation in the waveguides of an organic material {poly[bis-(p-toluene sulfonate) of 2, 4-hexadiyne-1, 6-diol]}. The phase change as a function of optical intensity has been measured via the Mach–Zehnder interferometric method. A π phase shift has been observed for a 2-mm-long waveguide as the peak intensity is increased by ∼7 MW/cm2 for polarization parallel to the chain axis (λ=1.06 μm). Through detailed polarization-selective measurements we have established that the observed phase change is electronic (nonthermal) in origin. The results are highly encouraging in terms of all-optical device applications of the material.
Morphology and distribution of atomic steps on Si (001) studied with scanning tunneling microscopy
Authors: Dijkkamp D. , Hoeven A. J. , van Loenen E. J. , Lenssinck J. M. , Dieleman J.
Published: July 2002

We have studied the morphology and distribution of atomic steps on Si(001) with scanning tunneling microscopy. We find that native oxide removal at temperatures up to 1350 K leads to step pinning and bunching. Cleaning at temperatures above 1450 K leads to regular step distributions which reflect the macroscopic misorientation of the sample. Steps running parallel to the 2×1 dimer rows on the upper terrace are straight, whereas steps perpendicular to these rows are ragged.
Attenuation at a wavelength of 0.86 cm due to fibrous aerosols
Authors: Bruce C. W. , Ashmore D. R. , Pittman P. C. , Pedersen N. E. , Pedersen J. C. , Waterman P. C.
Published: July 2002

Extinction efficiency was measured for fibrous aerosol particles arrayed on a diaphragm in a plane orthogonal to the Poynting vector of the incident radiation. Very small quantities of material can be characterized in this static fashion. Two-dimensional extinction efficiencies for a series of graphitic fibers of various resistivities are shown to agree with results of a variational theory. Particle interaction distances initiate at approximately the value of the length of the particle.
Annealing of implantation damage and redistribution of impurities in SiC using a pulsed excimer laser
Authors: Chou S. Y. , Chang Y. , Weiner K. H. , Sigmon T. W. , Parsons J. D.
Published: July 2002

A 6Hα-SiC crystal sample, which has a surface amorphous layer resulting from a high-dose Ga implantation, was heated using a pulsed excimer laser at several energy fluences. At an energy fluence of 1.66 J/cm2, the in situ reflectivity measurement of the surface during laser processing indicates that melting of the SiC surface has occurred. Rutherford backscattering and channeling analysis shows that the molten amorphous SiC recrystallizes using the substrate as a seed, and that the recrystallized layer has good crystal quality. Secondary-ion mass spectrometry measurements indicate that the melting, resulting from the excimer laser pulse, results in significant redistribution of the implanted Ga. This result, the first reported for SiC, suggests that the pulsed ultraviolet process can anneal the implantation damage through a melt recrystallization process, and thus could be used to dope SiC through a gas phase adsorption process.
Room-temperature photopumped operation of an InGaAs-InP vertical cavity surface-emitting laser
Authors: Deppe D. G. , Singh S. , Dupuis R. D. , Gerrard N. D. , Zydzik G. J. , van der Ziel J. P. , Green C. A. , Pinzone C. J.
Published: July 2002

Data are presented demonstrating the room-temperature operation of an InP-InGaAs vertical cavity surface-emitting laser. The laser structure has an active region consisting of a 2-μm-thick bulk InGaAs layer and has an emission wavelength of 1.65 μm. Both the front and rear mirrors consist of quarter-wave stacks of four pairs of electron beam evaporated layers of Si and SiO2 which have been optimized for maximum reflectivity. The structures are characterized in the transmission mode using a pump beam from a Nd:YAG laser at 1.06 μm.
Real time i
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u observation of the film growth of hydrogenated amorphous silicon by infrared reflection absorption spectroscopy
Authors: Toyoshima Yasutake , Arai Kazuo , Matsuda Akihisa , Tanaka Kazunobu
Published: July 2002

The growth of hydrogenated amorphous silicon films on Al substrates in a flow reactor was studied using infrared reflection absorption spectroscopy. All three hydride species (SiHx , x=1–3) in the growing films were detected as stretching and bending absorption bands in P polarization spectra. The dominant absorption band, initially originating from higher hydrides, was shifted to lower wave numbers with an increase of film thickness. A steep rise in absorption intensity at the initial stage and a time delay in SiH emergence are discussed in terms of the enhancement of detection sensitivity in a hydrogen-rich layer and the time needed for the formation of a bulk-network structure, respectively.
Effect of polymer matrices on hopping charge transport in molecularly doped polymers
Authors: Kanemitsu Yoshihiko , Einami Jiro
Published: July 2002

We have studied the effect of polymer matrices on time-of-flight (TOF) photocurrent pulse shape and the drift mobility of holes in polymers doped with 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-1, 3-oxazole in order to understand the nature of hopping charge transport in molecularly doped polymers (MDPs). The TOF pulse shapes in oxazole-doped polymers are classed into two groups: near rectangular or dispersive shapes. The drift mobility of holes in MDPs exhibiting near-rectangular TOF shape is large compared with that exhibiting dispersive. Moreover, the drift mobility of holes depends on the dielectric constant and the glass transition temperature of polymers. These results show that the polarization and phonon mode of polymers play an important role in hopping charge transport in MDPs.
Very low drive voltage optical waveguide modulation in an InGaAs/InAlAs superlattice
Authors: Bigan E. , Allovon M. , Carre M. , Voisin P.
Published: July 2002

We report the first room-temperature observation of Wannier–Stark localization under waveguide configuration in a short-period InGaAs-InAlAs superlattice. Using the ‘‘oblique’’ transition connecting a hole localized in a well with an electron localized in the adjacent well we have achieved a modulator having a 20 dB extinction ratio and a 3 dB attenuation with a drive voltage as low as 0.8 V. Our device is a 560-μm-long waveguide operating at 1.55 μm under TE polarization mode.
Improved value for the silicon intrinsic carrier concentration at 300 K
Authors: Sproul A. B. , Green M. A. , Zhao J.
Published: July 2002

A recent review suggests that the commonly cited value of 1.45×1010 cm−3 for the silicon intrinsic carrier concentration at 300 K is inconsistent with the best experimental and theoretical results. An alternative value of 1.08×1010 cm−3 was suggested. A new experimental measurement of 1.01×1010 cm−3 is reported with an estimated one standard deviation uncertainty of only 3%. This appears to be the most accurate experimental determination of this parameter at any temperature.
Barrier layers for realization of high capacitance density in SrTiO3 thin-film capacitor on silicon
Authors: Sakuma Toshiyuki , Yamamichi Shintaro , Matsubara Shogo , Yamaguchi Hiromu , Miyasaka Yoichi
Published: July 2002

High dielectric constant SrTiO3 thin films were sputter deposited on barrier layers/Si substrate to fabricate a capacitor for dynamic random access memories. Dielectric constant (εr) values of 140–210 were achieved for the 150-nm-thick SrTiO3 films using a Pt/Ti or Pt/Ta double-layer barrier. In the Pt(50 nm)/Ti(10 nm), Pt(50 nm)/Ti(50 nm), and Pt(50 nm)/Ta(10 nm) barrier, effective εr decreased by annealing in the temperature range between 450 and 550 °C, where the interdiffusion of Pt and Si was confirmed by x-ray diffraction analysis and cross-sectional transmission electron microscopy. In the Pt(50 nm)/Ta barrier, increase of the Ta thickness from 10 to 50 nm brought out a remarkable improvement of endurance to high-temperature annealing. That is, in the Pt(50 nm)/Ta(50 nm) barrier, large εr value (∼200) was maintained even with annealing at up to 700 °C.
Electroabsorption in II-VI multiple quantum wells
Authors: Partovi A. , Glass A. M. , Olson D. H. , Feldman R. D. , Austin R. F. , Lee D. , Johnson A. M. , Miller D. A. B.
Published: July 2002

We report the first study of the room-temperature electroabsorption effects in CdZnTe/ZnTe multiple quantum well structures which exhibit sharp excitonic absorption peaks. The magnitude of the Franz Keldysh and quantum-confined Stark Effects are found to be comparable to those of III-V semiconductors. With optimized structures we expect II-VI semiconductors to be important components for information processing in the visible spectrum.
Characterization of Ga2Se3 at ZnSe/GaAs heterovalent interfaces
Authors: Qiu J. , Menke D. R. , Kobayashi M. , Gunshor R. L. , Li D. , Nakamura Y. , Otsuka N.
Published: July 2002

Despite the valence difference across the junction, it has been shown that ZnSe/GaAs epilayer/epilayer interface state densities can be reduced to values comparable to the (Al,Ga)As/GaAs interface. We have previously reported a transmission electron microscopy study indicating that ZnSe/GaAs structures exhibiting low interface state densities are associated with the formation of an interfacial layer of zinc-blende Ga2Se3. In this letter we describe a procedure whereby an interfacial layer can be deliberately introduced prior to nucleation of ZnSe. In situ x-ray photoelectron spectroscopy is used to study the nature of the bonding at the interfacial layer. A comparison of the Se 3d core level features from the ZnSe epilayer surface, a Se-reacted GaAs surface, and from a separately grown Ga2Se3 epilayer, clearly indicates the same Se bonding characteristic for the Se-reacted interfacial layer and the Ga2Se3 epilayer.
Enhanced annealing kinetics in ion-implanted InxAl1−xAs studied by x-ray diffractometry
Authors: Clarke Roy , Dos Passos Waldemar , Chan Yi-Jen , Pavlidis Dimitris
Published: July 2002

We report a rapid thermal annealing (RTA) enhancement of the structural coherence of Si-implanted InxAl1−xAs (x≊0.54) layers on (100)InP. Under these annealing conditions (750 °C for 30 s), the enhancement occurs only in implanted samples and is characterized by the appearance of pendellösung fringes in double-crystal x-ray diffraction. Measurements of the parallel (ε∥) and perpendicular (ε⊥) lattice mismatch show a slight relaxation in ε⊥ during RTA without significant generation of dislocations (ε∥=0). The results suggest an electronic mechanism for the increased efficiency of RTA in implanted samples.
Demonstration of laser-assisted epitaxial deposition of GexSi1−x alloys on single-crystal Si
Authors: Lombardo S. , Smith Paul Martin , Uttormark M. J. , Brunco D. P. , Kramer K. , Thompson Michael O.
Published: July 2002

We report initial results of a novel technique for epitaxial growth of GexSi1−x alloys on single-crystal Si. During electron beam deposition of amorphous GexSi1−x, an incident XeCl excimer laser, operating at 308 nm with a 30 ns pulse duration, melts and crystallizes the amorphous layer in situ after each ≊5 nm of deposition. This laser-induced melt extends approximately 20 nm and provides epitaxy from the underlying substrate (or previous layers) at each stage of deposition. This melt/solidification process can be repeated continuously until the final desired alloy thickness is achieved. For layers up to 260 nm with Ge concentrations of 1.5–3 at. %, MeV ion channeling and cross-sectional transmission electron microscopy confirm epitaxial growth.
Compound formation at the interaction of Pd with strained layers of Si1−xGex epitaxially grown on Si(100)
Authors: Buxbaum A. , Eizenberg M. , Raizman A. , Schaffler F.
Published: July 2002

The interaction of thin Pd films deposited on strained layers of Si1−xGex epitaxially grown on Si(100) was studied. The Ge concentration in the molecular beam epitaxy grown Si1−xGex films was x=0.16, and their thickness 2300 Å. A highly textured ternary compound (Pd2Si1−yGey) formed concurrently with the PdGe phase, at annealing temperatures between 200 and 550 °C. Above 500 °C, a region of Si1−xGex alloy with high Ge concentration formed between the fully reacted compound and the unreacted Si1−xGex layer.
Light-induced changes in hydrogenated and deuterated amorphous silicon films and solar cells
Authors: Nevin W. A. , Yamagishi H. , Asaoka K. , Nishio H. , Tawada Y.
Published: July 2002

Optical, electronic, and structural properties of high-quality a-Si:H and a-Si:D films are compared. While having essentially similar electrical properties, a-Si:D shows higher stability of the photoconductivity (σph) under illumination, and faster thermal recovery of the degraded σph. These differences may originate from differences in the Si—Si and Si—H/D bonding structures, indicated by Raman scattering and infrared measurements. In agreement, single-junction solar cells with an intrinsic a-Si:D layer show smaller light-induced changes than a-Si:H cells.
Optical determination of carrier density in pseudomorphic AlGaAs/InGaAs/GaAs hetero-field-effect transistor structures by photoluminescence
Authors: Brugger H. , Müssig H. , Wölk C. , Kern K. , Heitmann D.
Published: July 2002

A photoluminescence (PL) analysis of a highly degenerate two-dimensional electron gas (2DEG) in pseudomorphic modulation-doped AlGaAs/InGaAs/GaAs transistor structures is reported. The PL response from samples with one or two populated electron subbands is dominated by one or two spectral bands, respectively, with a high-energy intensity cutoff. The spectral width varies linearly with the measured 2DEG sheet density ns or with a Schottky barrier depletion voltage, which directly reflects the two-dimensional density of states (2DDOS) below the Fermi level. We used the effective electron mass from cyclotron resonance experiments to evaluate the 2DDOS and can thus directly determine ns from the spectral width via the 2DDOS. Independent ns values were obtained from Shubnikov–de Haas measurements and agree excellently with ns values from PL.
High hydrogen concentrations produced by segregation into p+ layers in silicon
Authors: Marwick A. D. , Oehrlein G. S. , Wittmer M.
Published: July 2002

Gallium-implanted p+ layers in Si were exposed to atomic hydrogen from a plasma. It was found that very large hydrogen concentrations, up to 7.5 times larger than the peak Ga concentration of 7×1019/cm3, segregated into the p+ layer during treatment at 200 °C. The shape of the hydrogen concentration profile was similar to that of the Ga profile. Ion channeling showed that the H atoms did not occupy simple high-symmetry sites in the lattice, and electron microscopy revealed the presence of extended {111} stacking fault defects associated with the layer of high hydrogen concentration. A mechanism to account for these findings is suggested.
Observation of reflection high energy electron diffraction intensity oscillations during Si molecular beam epitaxial growth from disilane
Authors: Mokler S. M. , Liu W. K. , Ohtani N. , Joyce B. A.
Published: July 2002

Reflection high energy electron diffraction (RHEED) intensity oscillations have been used to monitor the growth of Si(001) during gas source molecular beam epitaxy (Si-GSMBE) from disilane. Oscillations are easily obtained on well-prepared surfaces on which a buffer layer has been grown. Oscillations of the specular beam in the [010] azimuth have been measured as a function of temperature and disilane flow rate. Strong and damped oscillations were observed between 610 and 680 °C in the two-dimensional growth regime. At higher temperatures, growth by step propagation dominated, while at lower temperatures growth became three-dimensional (3D) and consequently oscillations were weak or absent. Growth rates, as determined from the oscillations, are found to be independent of incident beam flux at substrate temperatures below 600 °C, but become dependent at higher temperatures. An Arrhenius plot indicates an activation energy (EA) of 40.7 kcal/mol in the low-temperature regime (T<600 °C) and an apparent EA dependence on disilane flux in the high-temperature regime.
Electrical properties of InP grown by gas-source molecular beam epitaxy at low temperature
Authors: Liang B. W. , Lee P. Z. , Shih D. W. , Tu C. W.
Published: July 2002

InP grown by gas-source molecular beam epitaxy at low temperature has been studied by Hall effect and admittance spectroscopy measurements. Contrary to GaAs, InP grown at low temperature is n-type and has low resistivity. The electron concentration of InP increases dramatically with decreasing growth temperature. A deep level at Ec−ED=320±50 meV is found to be the dominant donor in InP grown at low temperature.
High-resolution electron microscopy of growth interruption effect on AlAs/GaAs interfacial structure during molecular beam epitaxy
Authors: Ikarashi Nobuyuki , Tanaka Masaaki , Sakaki Hiroyuki , Ishida Koichi
Published: July 2002

Step structures at an AlAs/GaAs interface grown by molecular beam epitaxy (MBE) and the effects of growth interruption were investigated by high-resolution transmission electron microscopy (HRTEM) of the interface in the [11̄0] imaging orientation. In order to accomplish this, we developed a new TEM specimen preparation technique and determined an observation condition for HRTEM of the interface. Atomic steps were clearly observed at the AlAs-on-GaAs interface grown by conventional MBE, and the step intervals ranged from a few nm to several tens of nm. When 120 s growth interruption was employed, the interfacial steps were smoothed out and the step intervals become larger than several tens of nm.
Photoluminescence characterization of gated pseudomorphic AlGaAs/InGaAs/GaAs modulation-doped field-effect transistors
Authors: Gilpérez J. M. , Sánchez-Rojas J. L. , Muñoz E. , Calleja E. , David J. P. R. , Hill G. , Castagné J.
Published: July 2002

Electric field effects on gated pseudomorphic AlGaAs/InGaAs/GaAs quantum wells, where the Fermi level is modulated with a reverse gate voltage, are studied by low-temperature photoluminescence. A fit of the measured transition energies, with a self-consistent solution of the coupled Schrödinger–Poisson equations, gives the Fermi energy and the sheet carrier density. The absolute and relative intensities, from the first and second electron subbands to the first-hole subband transitions, are analyzed as a function of the carrier density and the Fermi level position. A very good agreement is found between data and calculations. No photoluminescence intensity enhancement, assigned to the Fermi-energy-edge singularity effects, has been observed.
Damage accumulation during ion implantation of unstrained Si1−xGex alloy layers
Authors: Haynes T. E. , Holland O. W.
Published: July 2002

The growth of damage induced by ion implantation in unstrained Si1−xGex epilayers is examined as a function of epilayer composition and of implant temperature and dose rate. Relaxed, epitaxial layers having compositions x=0.15, 0.50, and 0.80 were implanted with 30Si+ ions at energies of 80–90 keV, doses of 1 and 6×1014/cm2, and temperatures between −100 and +140 °C. Damage in the implanted layers was measured by ion channeling at room temperature (RT). For RT implantation, the amount of ion-induced damage increased with Ge fraction x at a rate much greater than expected from calculations of the displacement rate. In addition, the damage growth was suppressed in each of these alloys as the implantation temperature was increased such that over a range of ion doses, the damage yield approached zero at a temperature, T0, which increased with the Ge fraction, x. Furthermore, the damage was found to become strongly dependent on the dose rate at elevated implantation temperatures near T0. Based upon comparisons to a simple model, these observations suggest that increasing the Ge fraction progressively reduces the mobilities of primary defects within the collision cascades.
Cesiated thin-film field-emission microcathode arrays
Authors: Macaulay J. M. , Brodie I. , Spindt C. A. , Holland C. E.
Published: July 2002

The effect of adsorbed cesium on the performance of thin-film field-emission microcathode arrays with molybdenum tips is discussed. A reduction in the voltage required to extract an average of 1 nA per tip from 50 to 15 V is reported. Cesiated arrays have exhibited stable performance when operated continuously for up to 650 h at array current densities up to 100 A/cm2, with minimal leakage current. Using the Fowler–Nordheim theory, analysis of current-voltage characteristics of a heavily cesiated emitter array gives values for the emitting area, work function, and geometrical factor.
Nitrogen and oxygen incorporation during rapid thermal processing of Si in N2O
Authors: Kuiper A. E. T. , Pomp H. G. , Asveld P. M. , Bik W. Arnold , Habraken F. H. P. M.
Published: July 2002

Using a special detector setup in elastic recoil detection measurements, the incorporation of nitrogen during rapid thermal processing of Si(100) in N2O has been quantified for the first time. During oxidation at 1150 °C, the equivalent of a monolayer of silicon nitride is formed at the SiO2/Si interface. This retards the oxidation rate but it does not inhibit further oxide growth, which implies that gate oxides with thicknesses up to several tens of nm can be produced in N2O.
Interface-trap generation induced by hot-hole injection at the Si-SiO2 interface
Authors: Ogawa Shigeo , Shiono Noboru
Published: July 2002

The individual role of hot holes, hot electrons, and their recombination in interface-trap generation at the Si-SiO2 interface during hot-carrier injection has been investigated with an emphasis on its oxide thickness dependence (7–30 nm). Hot holes are found to be able to generate interface traps and to be much more effective for interface-trap generation at low-level injections than both hot electrons and electron-hole recombination. The experimental evidence of no thickness dependence of the hot-hole-induced interface-trap generation suggests that this is an interfacial process occurring at the Si-SiO2 interface.
Differences between light induced and native midgap states in intrinsic hydrogenated amorphous silicon obtained from detailed modeling of photoconductivities and subband-gap absorption
Authors: Gunes Mehmet , Wronski Christopher R.
Published: July 2002

The nature and densities of states near-midgap of intrinsic hydrogenated amorphous silicon (a-Si:H) were derived from detailed numerical analysis of magnitudes and intensity dependence of both subband-gap absorption and steady-state photoconductivities. Self-consistent results were obtained for a wide range of intensities only with the introduction of defects states above midgap which are different from those in the annealed state. These states, which are not detected by CPM, have densities and electron capture cross sections which are greater than those of the nativelike defects associated with the dangling bond. This is consistent with the rapid decreases in photoconductivity that occur upon initial light soaking and previously reported evidence for two types of SWE defects.
Gate quality Si3N4/Si/n-In0.53Ga0.47As metal-insulator-semiconductor capacitors
Authors: Wang Z. , Mui D. S. L. , Demirel A. L. , Biswas D. , Reed J. , Morkoç H.
Published: July 2002

In this letter, we report on gate quality Si3N4/Si/n-In0.53Ga0.47As capacitors representing significant improvement over that which has been previously obtained. These capacitors are formed by in situ nitride and Si layer deposition on as-grown molecular-beam epitaxy structure and are characterized by a small frequency dispersion, small hysteresis, a flat band voltage close to zero, and a minimum interface trap density of 2.4×1011 eV−1 cm−2.
Microstructural transition and degraded opto-electronic properties in amorphous SiGe:H alloys
Authors: Jones S. J. , Chen Y. , Williamson D. L. , Zedlitz R. , Bauer G.
Published: July 2002

The microstructure of amorphous Si1−xGex:H films with x<0.40 was studied using small-angle x-ray scattering (SAXS) and the results compared with those from opto-electronic and density measurements. The SAXS, the sub-band-gap absorption determined from photothermal deflection spectroscopy, and the photo/dark conductivity ratio all show relatively sharp changes above x=0.2. A corresponding sharp change in the anisotropic character of the SAXS is consistent with a transition to a columnar-like microstructure above x=0.2. The correlated results provide strong evidence for a direct link between degraded opto-electronic properties and the increased heterogeneity associated with the microstructural transition.
Intersubband optical transients in multi-quantum-well structures
Authors: Luc F. , Rosencher E. , Bois Ph.
Published: July 2002

We show that optical transients due to the intersubband photoionization of the electrons from quantum wells may be observed by inserting a multi-quantum-well structure in the space-charge layer of a Schottky diode. This method provides a direct measurement of the photoionization cross section of a quantum well. The escape probability of the photoexcited electron from the quantum well can thus be unambiguously deduced. Its variation with the electric field may be described by a simple model based on the statistical fluctuation of the quantum-well width.
Waveguiding in substrate supported and freestanding films of insoluble conjugated polymers
Authors: Mittler-Neher Silvia , Otomo Akira , Stegeman George I. , Lee Charles Y.-C. , Mehta Rajeev , Agrawal Ashwini K. , Jenekhe Samson A.
Published: July 2002

We demonstrate that waveguiding is possible in substrate supported and freestanding films of insoluble conjugated polymers. Photoresist gratings were used to couple 1.06–1.53 μm radiation into the waveguides allowing the refractive indices, the birefringence, and the linear losses to be measured.
Electrical properties of the SiNx/InP interface passivated using H2S
Authors: Kapila A. , Si X. , Malhotra V.
Published: July 2002

Passivation of the electronic defect states at the SiNx/InP interface has been achieved using gaseous H2S treatments of the InP surface. Al/SiNx/InP capacitors, fabricated by depositing silicon nitride films on the H2S-treated InP, exhibit good capacitance-voltage (C-V) characteristics. The SiNx layer is deposited at 200 °C using an electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR-PECVD) technique. A minimum trap density of 3.5×1011 cm−2 eV−1 is estimated using the high-frequency C-V characteristics. These devices appear to be more uniform and reproducible than ammonium/phosphorous polysulfide-passivated SiNx/InP interfaces.
Domain inversion in KTiOPO4 using electron beam scanning
Authors: Gupta Mool C. , Risk W. P. , Nutt Alan C. G. , Lau S. D.
Published: July 2002

Domain inversion in c-cut KTiOPO4 was produced by scanning an electron beam on the −c face. The domain reversal occurred through the 1 mm thickness of the sample. Second-harmonic conversion efficiency of 7×10−5 was measured for a fifth-order grating by focusing the beam to a 7 μm spot in a 500-μm-long domain-inverted KTP crystal. This efficiency is close to the theoretical value of 9×10−5. The measured phase matching bandwidth was 1.9 nm, which is in agreement with the theoretical value of 1.5 nm indicating that the domain-inverted grating is reasonably uniform over its entire length.
Formation and characterization of cobalt 6H-silicon carbide Schottky contacts
Authors: Lundberg N. , Östling M.
Published: July 2002

Rectifying Schottky contacts using e-beam evaporation of cobalt have been demonstrated on n-type silicon face 6H-SiC. Examination of the electrical properties was performed by I-V and C-V measurements as a function of annealing temperature in the 300–900 °C range for 1 h. Excellent rectifying behavior was found up to 700 °C. Heat treatments at 800–900 °C formed different cobalt silicides (Co2Si and CoSi) containing homogeneously distributed carbon with carbon agglomerates at the surface. Consecutive annealings from 300 to 800 °C increased the barrier height from 0.8 to 1.3 eV and the ideality factor from 1.15 to 1.46. Heat treatments at 900 °C modified the contacts into an ohmic behavior.
Crystal growth of C60 thin films on layered substrates
Authors: Tanigaki Katsumi , Kuroshima Sadanori , Fujita Jun-ichi , Ebbesen Thomas W.
Published: July 2002

The process of the C60 thin film crystal growth on layered materials such as MoS2 and mica is studied in detail with a combination of atomic force microscopy (AFM) and reflection high-energy electron diffractometry, and is compared to that on alkali-halide (NaCl) substrates. AFM shows that a single crystal containing triangle-shaped grains of 1–2 μm size with a (111) surface terrace is grown on the MoS2 substrate over a large area through a layer-by-layer process, while the grains on mica are 200–400 nm in size and distribute with some disorder in the orientation. The epitaxial characteristics of the C60 crystal growth on these layered substrates are discussed in comparison with that on alkali-halides.
SiO2 formation by thermal evaporation of SiO in oxygen atmosphere used to fabrication of high performance polycrystalline silicon thin film transistors
Authors: Sameshima T. , Kohno A. , Sekiya M. , Hara M. , Sano N.
Published: July 2002

A reactive evaporation of SiO in an oxygen atmosphere was investigated for forming a good interface of SiO2/Si. SiO2 films are formed at room temperature by evaporation of a SiO powder in an oxygen atmosphere with a flow rate of 2 sccm at a pressure of 1×10−4 Torr. The interface trapping density at SiO2/Si was lower than 5×1010 cm−2 eV−1. n- and p-channel Al-gate polycrystalline silicon thin film transistors (poly-Si TFTs) were fabricated at 270 °C with the present SiO2 films as a gate oxide and laser crystallized poly-Si films formed using a pulsed XeCl excimer laser. They showed good characteristics of a low threshold voltage of 1.1 V (n-channel) and −1.2 V (p-channel), and a high carrier mobility of 450 cm2/V s (n-channel) and 270 cm2/V s (p-channel).
Unusual photoluminescence properties in amorphous silicon nanopowder produced by plasma enhanced chemical vapor deposition
Authors: Costa J. , Roura P. , Sardin G. , Morante J. R. , Bertran E.
Published: July 2002

The supralinear dependence of visible photoluminescence intensity from amorphous silicon nanopowder produced in plasma enhanced chemical vapor deposition on excitation power and its exponential dependence on pressure is reported. It is shown that this new material emits two different kinds of photoluminescence that dominate at different pressures.
Delineation of semiconductor doping by scanning resistance microscopy
Authors: Shafai C. , Thomson D. J. , Simard-Normandin M. , Mattiussi G. , Scanlon P. J.
Published: July 2002

A new technique for the two-dimensional delineation of P-N junctions is presented using a scanning resistance microscope (SRM). The SRM uses a conducting probe to perform localized resistance measurements over a surface. These measurements are used to delineate between regions of different doping type and concentration. By using contact forces of 10−4 N, the contact area is estimated to be 30 nm. Experiments have shown the SRM capable of junction delineation with a lateral spacial resolution of less than 35 nm. In addition, during resistance measurements the SRM performs simultaneous surface topography measurements.