bluuebunny/crossref_metadata_2025 huggingface dataset:
Laboratory Predictors for Morbidity and Mortality after Thermal Burns in Pediatrics
Authors: Matar Mohamed Ebrahim , Elsharkawy Ahmed Elsayed , Mahmoud Wael Hussein , Elheniedy Mohamed A.
Published: November 2022

Background: The utility of laboratory values to predict complications in pediatric burn                    patients is poorly understood. This study assessed the laboratory investigations’ role                              in morbidities and mortalities prediction after moderate and severe thermal burn in                    pediatrics.

Methods: This prospective cohort study was carried out on 40 children with moderate                          and major thermal burn. All patients were subjected to clinical evaluation and laboratory investigations such as CBC, c-reactive protein (CRP), serum albumin, serum creatinine and             urea.

Results: Patients were subdivided into two groups: uncomplicated group (n=25) and complicated group (n=15). CRP, serum albumin, platelet count, serum creatinine and urea can significantly predict sepsis incidence with AUC of 0.922, 0.912, 0.911, 0.807, 0.810, at cut off >12, ≤2, ≤194, >0.7, >23, with sensitivity of 100%, 90.91%, 100 %,100 %, 85.71%, specificity of 86.21 %, 86.21%, 79.31%, 24.24%, 39.39%, PPV of 73.3 %, 71.4%, 64.7%, 21.9% , 23.1% and NPV of 100 %, 96.2 %, 100 %, 100 % , 92.9% respectively. Serum creatinine and urea can significantly predict incidence of acute kidney injury (AKI) with AUC of 0.807, 0.810 At cut off >0.7, >23, with sensitivity of 100.00 %, 85.71%, specificity of 24.24%, 39.39%, PPV of 21.9%, 23.1% and NPV of 100.0%, 92.9% respectively. Percent of burn, total ABSI, CRP, platelet, inhalation injury, albumin, creatinine and urea were dependent predictors for mortality. Sex, inhalation injury, percent of burn, total ABSI, hemoglobin, CRP, platelet, albumin, and creatinine were dependent predictors for sepsis. Sex, inhalation injury, percent of burn, total ABSI, CRP, hemoglobin, platelet, albumin and creatinine were dependent predictors for complication of acute kidney disease.

Conclusions: CRP, serum albumin, platelet count, serum creatinine and urea are good predictors of sepsis, AKI and mortalities after moderate to severe burn in pediatrics.
A Proposed Air-land Distribution Network for Delivery of Emergency Supplies in Mexico
Authors: Garcia-Martinez Ramon-Gabriel , Reyes-Ortiz Tania-Lucero , Herrera-Cortina Gloria-Karina , Belmonte-García Eduardo , Calihua-Pacheco Lizbeth , Caballero-Morales Santiago-Omar
Published: November 2022

Within logistics and the COVID-19 pandemic, the distribution of vaccines represented an important challenge as time was vital to attend the needs of the world population. This aspect involved an efficient the distribution chain between vaccine producers and consumers. For this purpose, appropriate transportation infrastructure, analysis of demand rate, inventory planning, and vaccine distribution locations were needed. The present work proposes an air-land distribution network which can be adapted for the delivery of vaccines, or prompt delivery of other emergency resources. This network is aimed to decentralize the international reception of these goods through an alternative of main international airports which can connect to local airports to speed up their delivery. Then a land distribution network is designed to reach the final application centers. The results of the network on a test instance provided insights regarding the challenges and practical implications for a real implementation.
An Assessment of the Impact of Corporate Social Responsibility on the Planning and Implementation of Real Estate Development in the Port Harcourt Metropolis
Authors: Ogban M. , Akujuru V. A. , Brown I.
Published: November 2022

In recent times, the failure of most Real Estate development in the Port Harcourt Metropolis could be attributed to the developers' poor implementation of Corporate Social Responsibility. This study, therefore, examines the impact of Corporate Social Responsibility of Real Estate Development within the Port Harcourt metropolis, such as the Rivtaf Golf Estate, on host communities - Okuru-Ama Community, Port Harcourt Local Government Area. The study adopts a quantitative approach enabled by survey research, as data for the study were collected through primary and secondary sources. Due to the concise nature of the study area, a total of seventy (70) questionnaires were judgementally selected as the sample size. These questionnaires were administered, filled out and returned by respondents from the Okuru Ama Community and some Rivtaf Golf Estate staff members. Field data were analysed using the Statistical Package for Social Studies (SPSS) version 22, and results were displayed in descriptive and inferential statistics in addition to the Relative Importance Index (RII). Available results indicate that Rivtaf Golf Estate has a good relationship with its host community and adheres strictly to its Corporate Social Responsibilities, significantly impacting Real Estate Development. The result further revealed that Rivtaf Golf Estate provides employment opportunities to some indigenes of the Okuru Ama community, makes contributions to the community scholarship purse, maintains the primary access road to the Estate through the community and sometimes sends Christmas packages to the community. The study recommends that there should be effective implementation of corporate social responsibility entered with host communities. Real Estate Developers should be socially responsible and sensitive to the interests of various stakeholders, especially the host community, by caring about the environment, community welfare and society in general.
O desatar da imaginação sociológica com a juventude alfenense
Authors: Conceição Marcelo , Nagahiro Lucas Costa , Aires dos Santos Mateus
Published: November 2022

Neste trabalho são relatadas parte das atividades desenvolvidas pelo projeto de extensão "A imaginação sociológica e o sul de Minas", da Universidade Federal de Alfenas, com estudantes do ensino médio do município de Alfenas. Partindo do conceito de imaginação sociológica, elaborado por Wright Mills, o projeto tem buscado estimular estudantes da rede pública estadual de ensino a relacionarem as transformações sociais que ocorrem em contextos mais amplos, com as mudanças imediatas em suas vidas cotidianas. Dentre as atividades desenvolvidas, desde 2017, destacaram-se: levantamento feito com os estudantes sobre seus interesses e seu perfil, e discussões sobre o mercado de trabalho e o Exame Nacional do Ensino Médio. As ações nas escolas promoveram debates sobre as perspectivas de futuro, o acesso à educação superior pública e a realidade social. Os questionamentos e inquietações dos estudantes indicaram ter ocorrido o início de um desatar da imaginação sociológica da juventude alfenense.
CD45 phosphatase in Jurkat cells is necessary for response to applied ELF magnetic fields
Authors: Lindström Ewa , Berglund André , Mild Kjell Hansson , Lindström Per , Lundgren Erik
Published: July 2002

Oscillations of free intracellular calcium [Ca2+]i were seen in individual Jurkat cells as response to a 50 Hz, 0.15 mT magnetic field (MF). In contrast, a CD45‐deficient Jurkat cell line was unable to respond to MF stimulation. The phosphatase activity of CD45 has been implicated to regulate p56
lck
tyrosine kinase activity by removing an inhibitory phosphate. By using Jurkat cells that expressed a chimeric molecule, comprising the cytoplasmic phosphatase domain of CD45, the MF induced calcium response was restored. This showed the necessity for an intact signal transduction pathway leading to a calcium increase as a result of stimulation of cells by MF. Thus, our data suggest that the target for the applied MF are molecules involved in early events in the signalling pathway from the T cell antigen receptor.
Stimulation of cloned human glucagon‐like peptide 1 receptor expressed in HEK 293 cells induces cAMP‐dependent activation of calcium‐induced calcium release
Authors: Gromada Jesper , Rorsman Patrik , Dissing Steen , Wulff Birgitte S.
Published: July 2002

The actions of glucagon‐like peptide‐1(7–36)amide (GLP‐1(7–36)amide) on cellular signalling were studied in human embryonal kidney 293 (HEK 293) cells stably transfected with the cloned human GLP‐1 receptor. The cloned GLP‐1 receptor showed a single high‐affinity binding site (K
d = 0.76 nM). Binding of GLP‐1(7–36)amide stimulated cAMP production in a dose‐dependent manner (EC50 = 0.015 nM) and caused an increase in the intracellular free Ca2+ concentration ([Ca2+]i). The latter effect reflected Ca2+‐induced Ca2+ release and was suppressed by ryanodine. We propose that the ability of GLP‐1(7–36)amide to increase [Ca2+]i results from sensitization of the ryanodine receptors by a protein kinase A dependent mechanism.
A human homolog of the mitochondrial protein import receptor Mom19 can assemble with the yeast mitochondrial receptor complex
Authors: Seki Naohiko , Moczko Martin , Nagase Takahiro , Zufall Nicole , Ehmann Bruno , Dietmeier Klaus , Schäfer Eberhard , Nomura Nobuo , Pfanner Nikolaus
Published: July 2002

Import of preproteins into mitochondria requires transport machineries in both mitochondrial membranes that have been characterized in Saccharomyces cerevisiae and Neurospora crassa. By cDNA analysis, we identified a human protein of 16 kDa with significant overall homology to the fungal mitochondrial import receptor Mom19, including the three typical characteristics: a hydrophobic N‐terminal segment, a tetratrico peptide motif in the middle and a negatively charged C‐terminus. The human Mom19 homolog is expressed in all tissues analyzed. When synthesized in vitro, the human Mom19 homolog is targeted to isolated yeast mitochondria and specifically associates with the outer membrane receptor complex, suggesting that indeed a mitochondrial import receptor was identified.
Inflation Insurance
Authors: Bodie Zvi
Published: July 2002

This article uses the concepts of option theory to explore the possibility of providing annuities that offer partial protection against inflation at a cost acceptable to retirees. A contract to insure a future payment against inflation is equivalent to a European call option on the consumer price index. This equivalence makes it possible to apply the techniques of modern contingent claims analysis to the production and pricing of inflation-protected annuities that have deductibles and caps. The method synthesizes a CPI call option through a dynamic trading strategy of borrowing and investing in CPI-linked bonds. The price of the insurance is the cost of implementing the strategy. The article also considers the question of who can provide the CPI-linked bonds that are the ultimate basis for the inflation insurance. l?ie Journal of Risk and Insurance, Vol. LVII, No. 4 (December 1990), pp. 634-645. (Reprinted with permission of The Journal of Risk and Insurance.)
Leveraged Real Estate Investments by Tax-Exempt and Taxable Investors
Authors: Menna Gilbert G.
Published: July 2002

This article evaluates real estate investments by entities that include tax- exempt and taxable investors where the investor leverages its acquisitions. The advantages and disadvantages of four investment vehicles-partnerships, REITs, special-purpose trusts, and a multiple-entity structure that combines a partnership with a REIT-are discussed. The author concludes that the most flexible investment vehicle is the multiple-entity partnership/ REIT structure.

The Journal of Real Estate Taxation, Vol. 17, No. 3 (Spring 1990), pp. 231- 249. (Reprinted with permission of Warren, Gorham & Lamont, Inc. All rights reserved.)
An Exploration of an Individual’s Decision-Making Regarding Tax-Deferred Investment Plans
Authors: Behzad M. Hadi , Lee Patrick S. , Vora Gautam
Published: July 2002

Several decision making models are presented in this article for allocating an individual’s savings in tax-deferred opportunities. Because the models are general, they can examine any number of tax-deferred opportunities. The resource allocation problem is formulated as a linear program. Historical or forecast values of costs and returns are used as exogenous parameters of the linear program. The model is simulated under different scenarios to demonstrate that the linear programming approach can be fruitful, simple, and insightful in bridging the gap between theoret- ical findings and actual investment in various tax-deferred opportunities. The _/our- naZofRiskandZnsurance, Vol. LVIII, No. 2 (June 1991), pp. 205-226. (Reprinted with permission of The Journal of Risk and Insurance.)
Dermatophyte granulomas caused by Trichophyton mentagrophytes in a dog
Authors: Bergman Robert L. , Medleau Linda , Hnilica Keith , Howerth Elizabeth
Published: July 2002

Abstract Multiple, dermal and subcutaneous nodules developed in a young female Manchester Terrier dog that had a chronic history of superficial dermatophytosis. Skin biopsy specimens of the nodules revealed granulomatous inflammation in the deep dermis and subcutis with branching fungal organisms. Cultures of multiple biopsy specimens from the nodules all yielded Trichophyton mentagrophytes. The lesions in this dog were similar to granulomatous dermatophytosis, a skin disease that has been reported in Persian cats and one Yorkshire Terrier dog.
Cytotoxic T‐lymphocyte antigen‐4 microsatellite polymorphism is associated with multiple myeloma
Authors: Zheng Chengyun , Huang DeRen , Liu Li , Björkholm Magnus , Holm Göran , Yi Qing , Sundblad Anne
Published: July 2002

Multiple myeloma (MM) is a B‐lineage malignancy with unknown aetiology. It has been considered that predisposing genetic factors might be implicated in the disease. In this study, the microsatellite polymorphism in the exon 3 of the cytotoxic T‐lymphocyte antigen‐4 (CTLA‐4) gene was analysed in patients with MM and monoclonal gammopathy of undetermined significance (MGUS), together with ethnically matched healthy controls. The results showed that frequencies of the genotype 86/86 and of the allele 86 were significantly decreased in MM and MGUS compared with matched healthy controls, indicating that the CTLA‐4 microsatellite polymorphism might represent a susceptibility locus for MM and MGUS.
The relationship between bone age, chronological age and dental age in children with isolated growth hormone deficiency
Authors: Vallejo‐Bolaños E. , España‐López A.J. , Muñoz‐Hoyos A. , Fernandez‐Garcia J.M.
Published: July 2002

Aim. To relate dental age and bone age to chronological age in a group of children with isolated growth hormone deficiency (GHD).

Design. A group of 25 children between the ages of 6 and 18 years, diagnosed as having GHD were studied. Of these, 16 were male and nine were female, undergoing replacement therapy with growth hormone (GH) over 2·5 years. Dental age (DA) was estimated from orthopantograms (Haavicko Methods) and compared to bone age (BA) by Greulich and Pyle Standards, and chronological age (CA).

Results. CA versus BA – there was a statistically significant difference of 1·52 years between the average chronological age and bone age (t = 5·61, P < 0·001). CA versus DA – there was a statistically significant difference of 0·92 years between the average chronological age and dental age (t = 3·93, P < 0·001). BA versus DA – statistically nonsignificant differences were found between the average bone age and dental age (t = –0·60, P = 0·10).

Conclusion. After 2·5 years of therapy with growth hormone both DA and BA showed a significant delay compared to CA. Despite the fact that some catch‐up occurs in speed of growth there is no evidence from the children in our study that might support the occurrence of a similar speed‐up in dental age.
Three‐dimensional force measurements on oral implants: a methodological study
Authors: Duyck J. , Van Oosterwyck H. , De Cooman M. , Puers R. , Vander Sloten J. , Naert I.
Published: July 2002

This paper describes a methodology that allows in vitro and in vivo quantification and qualification of forces on oral implants. Strain gauges are adapted to the outer surface of 5·5 and 7 mm standard abutments (Brånemark System®, Nobel Biocare, Sweden). The readings of the strain gauges are transformed into a numerical representation of the normal force and the bending moment around the X‐ and Y‐axis. The hardware and the software of the 3D measuring device based on the strain gauge technology is explained and its accuracy and reliability tested. The accuracy level for axial forces and bending moments is 9.72 N and 2.5 N·cm, respectively, based on the current techniques for strain gauged abutments. As an example, an in vivo force analysis was performed in a patient with a full fixed prosthesis in the mandible. Since axial loads of 450 N and bending moments of 70 N·cm were recorded, it was concluded that the accuracy of the device falls well within the scope of our needs. Nevertheless, more in vivo research is needed before well defined conclusions can be drawn and strategies developed to improve the biomechanics of oral implants.
Tensile stress variations of chemically etched GaAs films grown on Si substrates
Authors: Lee Henry P. , Liu Xiaoming , Lin Hong , Smith John S. , Wang Shyh , Huang Yi-He , Yu Peter , Huang Yi-Zhu
Published: July 2002

Photoluminescence (PL) at 77 K is used to study tensile stress variations in chemically etched stripes of a 3-μm-thick GaAs film grown on Si substrate. The etched patterns consist of 1-mm-long stripes with widths ranging from 100 to 4 μm and 4 μm by 4 μm squares. We observed monotonic shift of PL peaks towards shorter wavelength for decreasing stripe width. In particular, when the width of the stripe is less than 7 μm, tensile stress is essentially uniaxial as evident from the magnitude of shift in PL peaks. The polarization characteristics of the PL spectra of these uniaxially stressed stripes are investigated and found to agree well with theoretical predictions.
Elastic properties of silicon oxynitride films determined by picosecond acoustics
Authors: Grahn H. T. , Maris H. J. , Tauc J. , Hatton K. S.
Published: July 2002

The sound velocity and elastic modulus of a series of amorphous silicon oxynitride films produced by reactive sputtering have been measured as a function of nitrogen content. The acoustic pulses were generated and detected with ultrashort light pulses. The sound velocity was found to depend linearly on the nitrogen content.
Memory phenomena in heterojunction structures: Evidence for suppressed thermionic emission
Authors: Beltram Fabio , Capasso Federico , Walker John F. , Malik Roger J.
Published: July 2002

The physics of a new GaAs/AlGaAs floating-gate memory device is investigated. Long electron storage times (e.g., 4 h at 140 K) have been measured and linked to the indirect nature of the GaAs-AlAs conduction-band discontinuity. A simple analysis of the structure shows that scattering-assisted tunneling processes and band-structure effects, not included in standard thermionic emission theories, must be considered to properly account for the observed long retention times.
Electromigration behavior of ionized cluster beam deposited aluminum films on SiO2
Authors: Hummel R. E. , Yamada I.
Published: July 2002

Unpassivated, pure aluminum films on 7000-Å-thick SiO2 were prepared by ionized cluster beam deposition in a vacuum of 2×10−6 Torr from a carbon crucible which had a nozzle of 2 mm diameter. The resulting particle beam was ionized by impact of electrons and accelerated by an electrical potential towards the substrate. The activation energy for electromigration for these films at temperatures between 125 and 200 °C was found to be 1.1 eV. The initial resistivity of the films was about 12 μΩ cm which decreased to 8 μΩ cm due to annealing at temperatures between 400 and 450 °C.
Measurements of gain, saturation, and line competition in an electron beam pumped high-pressure Ar/Xe laser
Authors: Suda Akira , Wexler Bernard L. , Feldman Barry J. , Riley Kevin J.
Published: July 2002

Using a small electron beam device, we have observed time-dependent competition among the 1.73, 2.03, 2.63, and 2.65 μm lines of the xenon laser in a high-pressure argon buffer. The small-signal gain and saturation intensity for each of these lines have also been measured. The maximum specific energy output of the laser was 1.7 J/ℓ  and the efficiency was 2.3%.
Optically controlled absorption modulator based on state filling of InxGa1−xAs/GaAs quantum wells
Authors: Iannelli J. M. , Maserjian J. , Hancock B. R. , Andersson P. O. , Grunthaner F. J.
Published: July 2002

We report the first demonstration of an optically controlled absorption modulator based on state filling in a periodically doped InxGa1−xAs/GaAs multiple quantum well structure. Differential absorption of approximately 104 cm−1 is observed in the quantum wells of our test structure at saturation pump powers. Photoluminescence and time-resolved modulation measurements confirm the predicted behavior of carrier recombination and give a measure of enhanced carrier lifetime of approximately 1 ms. These initial results show the potential for developing these structures into optically addressed spatial light modulators.
Observation of chemical laser oscillation in the visible range
Authors: Yoshida S. , Shimizu K. , Sawano T. , Tokuda T. , Fujioka T.
Published: July 2002

A new visible chemical laser analogous to excimer lasers in lasing principle has been studied. Laser oscillation has been observed in the red spectral range. To our knowledge this is the first demonstration of chemical laser oscillation in the visible spectral range.
Early stages of plasma synthesis of diamond films
Authors: Meilunas R. , Wong M. S. , Sheng K. C. , Chang R. P. H. , Van Duyne R. P.
Published: July 2002

The early stages of diamond film nucleation and growth in a microwave plasma have been studied in detail as a function of important deposition parameters. The influence of the substrate temperature on the diamond nucleation rate, quality, and final film morphology has been elucidated through Raman spectroscopy and scanning electron microscopy measurements. Using transmission infrared spectroscopy and x-ray diffraction, it is found that a carbide layer is initially formed on the substrate prior to the growth of the diamond film. Furthermore, the final film morphology is also a strong function of the plasma starting condition, the gas composition, and the substrate temperature.
Photoluminescence studies of pseudomorphic modulation-doped AlGaAs/InGaAs/GaAs quantum wells
Authors: Dodabalapur A. , Kesan V. P. , Hinson D. R. , Neikirk D. P. , Streetman B. G.
Published: July 2002

We discuss the photoluminescence (PL) properties of pseudomorphic modulation-doped Al0.15Ga0.85As/In0.2Ga0.8As/GaAs quantum wells as a function of temperature. At 4.2 K, hole localization influences the PL linewidth; however, at higher temperatures (77 K) the thermal energy of photoexcited holes is sufficiently large to obtain a reliable measure of sheet carrier density from the PL linewidth. Our results also suggest that information about the interface quality can be obtained from an analysis of the PL linewidth at 77 and 4.2 K. The spectra taken from several samples clearly show that the PL transition energy exhibits a free-carrier density dependence due to band-gap renormalization and electric field effects.
New shearing interferometer for real-time characterization of cryogenic laser fusion targets
Authors: Kong Hong-Jin , Wittman Mark D. , Kim Hyo-gun
Published: July 2002

Optimum performance of a laser-driven cryogenic target requires spherical symmetry and uniformity of the deuterium-tritium (DT) condensate on the interior surface of the fuel capsule. These characteristics are determined, in general, by interferometry. We have developed a shearing interferometer that is free from spherical and chromatic aberration. The detailed structure of the inteferometer is elucidated, and interferograms with a constant phase background and a tilted fringe background are presented.
Identification of band-gap states by deep level transient spectroscopy on radioactive probes: The case of Au and Pt in silicon
Authors: Petersen Jon Wulff , Nielsen Jacob
Published: July 2002

The deep level transient spectroscopy technique has been applied to silicon doped with radioactive impurities. The disappearance or appearance of features in the spectra following the transmutation of the incorporated radioactive atoms identifies an impurity involved in the centers observed. Results for Au and Pt diffused in Si are presented showing that Au occupies the same lattice position as Pt, which is known from electron paramagnetic resonance measurements to be substitutional.
Effects of hydrogen atoms on the network structure of hydrogenated amorphous and microcrystalline silicon thin films
Authors: Asano A.
Published: July 2002

By alternating the deposition of a several-angstrom-thick hydrogenated amorphous silicon layer and the exposure to a hydrogen plasma, the structure of the resultant hydrogenated silicon films is varied from device-grade amorphous to microcrystalline without any change in the film precursors. On the basis of experimental results, the effects of hydrogen atoms reaching the film-growing surface on the Si-Si network structure are discussed.
Picosecond blue light pulse generation by frequency doubling of a gain-switched GaAlAs laser diode with saturable absorbers
Authors: Ohya Jun , Tohmon Genji , Yamamoto Kazuhisa , Taniuchi Tetsuo , Kume Masahiro
Published: July 2002

Picosecond blue light pulse generation by frequency doubling of a gain-switched GaAlAs laser diode in a proton-exchanged MgO:LiNbO3 waveguide is reported. High-peak fundamental pulse power of 1.23 W is obtained by employing a laser diode with saturable absorbers. Blue light pulse of 7.88 mW maximum peak power and 28.7 ps pulse width is generated in the form of Cherenkov radiation.
Direct observation of picosecond spin relaxation of excitons in GaAs/AlGaAs quantum wells using spin-dependent optical nonlinearity
Authors: Tackeuchi Atsushi , Muto Shunichi , Inata Tsuguo , Fujii Toshio
Published: July 2002

We have directly observed spin relaxation of excitons in the picosecond region using time-resolved polarization absorption measurements. With the help of spin-dependent optical nonlinearity of excitonic absorption, we obtained a fast decay of spin-up carriers and a fast accumulation of spin-down carriers with a spin relaxation time of 32 ps for a GaAs/Al0.51Ga0.49As multiple quantum well at room temperature with a time resolution of 1 ps.
Stability of crystals that grow or evaporate by step propagation
Authors: Ghez R. , Cohen H. G. , Keller Joseph B.
Published: July 2002

We analyze the linear stability of a Stefan-like problem for moving steps in the context of W. K. Burton, N. Cabrera, and F. C. Frank’s theory of crystal growth [Philos. Trans. R. Soc. (London) A 243, 299 (1951)]. Asymmetry and departures from equilibrium at steps are included. The stability criterion depends on supersaturation and average step spacing, both experimentally accessible, and on dimensionless combinations of surface diffusivity, surface diffusion length, and adatom capture probabilities at steps, which can be estimated from bond models. This stability criterion is analyzed and presented graphically in terms of these physical parameters.
Zinc-stimulated outdiffusion of iron in InP
Authors: Young E. W. A. , Fontijn G. M.
Published: July 2002

High-resistivity InP (108 Ω cm) can be grown by means of metal organic vapor phase epitaxy using ferrocene as a dopant source. Adjacent zinc-doped layers of InP annihilate the resistivity of the (intentionally) iron-doped InP. The presence of Zn dramatically enhances outdiffusion of iron out off intentionally iron-doped layers of InP into the Zn-doped InP. Diffusion of Zn into the iron-doped InP is also observed.
Transient diffusion of low-concentration B in Si due to 29Si implantation damage
Authors: Packan P. A. , Plummer J. D.
Published: July 2002

The effects of implantation damage on B diffusion are analyzed through the use of 29Si implants. Implant doses of 29Si ranging from 1×1012/cm2 to 1×1014/cm2 were used to create controlled amounts of damage. Temperatures ranging from 800 to 1000 °C were used to anneal the implant damage. For all anneal temperatures, the peak B concentration was well below the intrinsic electron concentration. Even for 29Si doses as low as 1×1012/cm2 significantly enhanced B diffusion was observed. The largest enhancement in B diffusion was observed for the highest 29Si implant dose and lowest anneal temperature. The kinetics of damage annealing determine the transient enhancement in the B profile. These results have important implications for the formation of shallow junctions using ion implantation.
Production of highly oxidized As on GaAs (110) at 20 K
Authors: Anderson Steven G. , Seo J. M. , Komeda T. , Capasso C. , Weaver J. H.
Published: July 2002

High-resolution synchrotron radiation photoemission results for O2 physisorbed on GaAs (110) show Ga-O and As-O formation that is a direct result of photon-induced reaction at 20 K. Spatially resolved studies show that the thickness and chemical composition of the semiconductor oxides vary in proporition to total beam irradiation. The extent of reaction can be controlled by varying the amount of oxygen present on the surface, and As5+-like bonding configurations can be formed. These results can only be understood when competition between thermodynamic, kinetic, photon- and electron-mediated processes are considered.
Enhanced flux pinning by phase decomposition in Y-Ba-Cu-O
Authors: Jin S. , Tiefel T. H. , Nakahara S. , Graebner J. E. , O’Bryan H. M. , Fastnacht R. A. , Kammlott G. W.
Published: July 2002

Significantly improved flux pinning has been achieved in bulk YBa2Cu3O7−δ superconductor (‘‘123’’ compound) containing fine-scale defects (<∼50 Å thick). The measured Jc intragrain of ∼105 A/cm2 at 77 K, H=0.9 T is about ten times higher than the typical values for bulk Y-Ba-Cu-O. The improved structure was produced by rapid decomposition at 920 °C of the YBa2Cu4O8 (‘‘124’’) precursor. This new and simple processing route could lead to a commercially viable processing technique for flux-pinning enhancement in bulk Y-Ba-Cu-O.
Effects of lattice mismatch on InxGa1−xAs/InP heterojunctions
Authors: Lee C. D. , Forrest S. R.
Published: July 2002

The conduction-band discontinuities and interface charge densities of several n-N isotype InxGa1−xAs/InP (x≂0.53) heterojunctions with lattice mismatches (Δa/a) ranging from +0.26 to −0.24% were measured using capacitance-voltage techniques. To facilitate these measurements, organic-on-inorganic contact barrier diodes were used. Extremely low interface charge densities (<1×1010 cm−2) are obtained for all the samples, which are approximately one order of magnitude lower than previously reported values for these heterojunctions. We find that the interface charge density is independent of the magnitude of lattice mismatch and temperature. All the samples show a clear peak-and-notch in their apparent free-carrier concentration profiles at temperatures as low as 83 K. This is in contrast to results reported previously where the notch is observed to disappear at low temperature. The measured heterojunction conduction-band discontinuity is also found to be temperature independent, with a value of 0.22±0.02 eV.
Effective barrier height, conduction-band offset, and the influence of p-type δ doping at heterojunction interfaces: The case of the InAs/GaAs interface
Authors: Shen T.-H. , Elliott M. , Williams R. H. , Westwood D.
Published: July 2002

We demonstrate that the effective band discontinuity at an n-isotype heterojunction interface can be significantly modified by introducing p-type δ doping close to the interface during molecular beam epitaxy growth. This is shown for the case of the relaxed InAs-GaAs interface where the band discontinuities with and without δ doping have been measured by the I-V technique coupled with appropriate numerical modeling of the interface.
Electrical characterization of molecular beam epitaxial GaAs with peak electron mobilities up to ≊4×105 cm2 V−1 s−1
Authors: Stanley C. R. , Holland M. C. , Kean A. H. , Stanaway M. B. , Grimes R. T. , Chamberlain J. M.
Published: July 2002

The effect of varying the temperature (Tcr) of an As4→As2 cracker furnace between 600 and 700 °C on the properties of GaAs grown by molecular beam epitaxy has been evaluated using 4–300 K Hall measurements and 4.2 K far-infrared photoconduction spectroscopy, in an extension of earlier work on high-mobility material (Ref. 1). The residual donors are silicon and sulphur with mid-1013 cm−3 concentrations under As2-growth conditions (Tcr=700 °C). By lowering Tcr, the silicon concentration is reduced substantially, leaving sulphur as the principal impurity. A 15-μm-thick layer grown with Tcr=650 °C has measured free-electron densities of ≊2.8×1013 cm−3 and peak mobilities ≊4×105 cm2 V−1 s−1 at ≊28–42 K, the highest ever recorded in bulk GaAs.
Methane/hydrogen-based reactive ion etching of InAs, InP, GaAs, and GaSb
Authors: Werking James , Schramm Jeff , Nguyen Chanh , Hu Evelyn L. , Kroemer Herbert
Published: July 2002

Reactive ion etching (RIE) of InAs, InP, GaAs, and GaSb using CH4/H2 mixtures has been studied to determine the resulting etch profiles and surface morphologies, as well as the dependence of etch rates on cathode temperature, chamber pressure, and electrode self-bias. These materials are found to etch slowly and controllably, with etched samples having smooth surfaces and nearly vertical sidewalls. Our results demonstrate that CH4/H2 RIE is a promising technology for fabricating electronic devices using the newly emerging InAs/GaSb/AlSb material system as well as the better established InP material system.
Diffusion versus oxidation rates in silicon-germanium alloys
Authors: Eugène J. , LeGoues F. K. , Kesan V. P. , Iyer S. S. , d’Heurle F. M.
Published: July 2002

We have studied the oxidation of SiGe alloys of different compositions (between 25 and 75 at.% Ge). All of the oxidations were performed at 900 °C in wet atmosphere on 7500-Å-thick films grown by molecular beam epitaxy. Below 50 at.% Ge, the oxidation remains similar to what has been described previously, i.e., initially, the rate is enhanced by the presence of Ge, the oxide formed is pure SiO2 and a Ge pileup forms at the SiO2/Si-Ge interface. In these relatively thick films, we propose that after extended oxidation, the decrease of Si concentration at the interface slows down oxidation rates enough so that eventually, the oxide thickness for the SiGe alloys ends up smaller than that of pure Si. For alloys containing above 50 at.% Ge, a markedly different behavior is found: A two-layer oxide is formed, consisting of a mixed (Si,Ge) O2 layer near the surface, and a pure SiO2 layer underneath. The rates of oxidation in this case are even faster, since both Ge and Si are being oxidized. The general behavior is explained in terms of the balance of Si and Ge diffusion fluxes, to and from the interface, needed to sustain oxidation.
Theoretical and experimental investigation of conversion of phase noise to intensity noise by Rayleigh scattering in optical fibers
Authors: Wu S. , Yariv A. , Blauvelt H. , Kwong N.
Published: July 2002

The conversion of laser phase noise to intensity fluctuation noise in optical fibers due to mixing with Rayleigh scattered light is considered. A theory combining the laser quantum phase dynamics and the statistical scattering in the fiber leads to simple expressions for the spectral densities of the intensity fluctuations in a number of generic cases. These are compared with experiments involving distributed feedback semiconductor lasers and low-loss fibers with lengths up to 20 km.
Observation of misfit dislocations in epitaxial CoSi2/Si (111) layers by scanning tunneling microscopy
Authors: Stalder Roland , Sirringhaus Henning , Onda Nico , von Känel Hans
Published: July 2002

The surfaces of epitaxial CoSi2 layers grown on Si(111) have been examined by scanning tunneling microscopy (STM) in ultrahigh vacuum. The onset of strain relaxation above the critical thickness of about 40 Å has been monitored by STM for the first time. This relaxation takes place by the formation of a honeycomb network of partial dislocations lying in the interface plane. An associated network of protruding lines has been detected in STM topographs for film thicknesses up to 104 Å. The topographic cross sections perpendicular to the lines are found to have a Lorentzian shape with a height of 0.6 Å and a half-width equal to the layer thickness. Our analysis suggests that similar effects should be observable for a wider class of heteroepitaxial systems.
Intervalley scattering in GaAs and InP probed by pulsed far-infrared transmission spectroscopy
Authors: Saeta Peter N. , Federici John F. , Greene Benjamin I. , Dykaar Douglas R.
Published: July 2002

The dynamics of photoexcited electrons in GaAs and InP were studied using the transmission of 200-fs pulses of far-infrared radiation in the spectral range 15–100 cm−1. Kinetic traces of the infrared transmission as a function of delay between optical excitation and infrared probe show a probe-limited decrease in transmission followed by a more gradual (0.7–2 ps) drop to a steady value, consistent with the slow return of electrons from high-mass satellite valleys. Infrared transmission spectra, analyzed in the context of a Drude model, reveal density-dependent electron mobilities 3–4 times below equilibrium n-doped values. Electron-hole collisions likely account for the lower mobility.
Organic electroluminescent devices based on molecularly doped polymers
Authors: Kido Junji , Kohda Masafumi , Okuyama Katsuro , Nagai Katsutoshi
Published: July 2002

Electroluminescent devices were fabricated using poly(methyl methacrylate) (PMMA) molecularly doped with triphenyldiamine derivative and tris(8-quinolinolato)aluminum(III) complex (Alq). A cell structure of glass substrate/indium–tin–oxide/doped PMMA/Mg:Ag was employed. Carrier injection from the electrodes to the doped PMMA layer through the dopants and concomitant electroluminescence from Alq were observed. Green emission with luminance of 920 cd/m2 was achieved at a drive voltage of 17 V.
Minority electron transport in InP/InGaAs heterojunction bipolar transistors
Authors: Dodd Paul , Lundstrom Mark
Published: July 2002

Electron transport across the base of InP/InGaAs heterojunction bipolar transistors is examined by Monte Carlo simulation. The base transit times and electron distribution functions are examined as a function of basewidth. Clear ballistic behavior is observed only for extremely thin bases (much less than 100 Å). Over the range of basewidths of interest for devices, base transport appears diffusive, but the electrons are very far from thermal equilibrium. The diffusive behavior is shown to arise from the sensitivity of the steady-state carrier population to small amounts of large-angle scattering.
144 °C operation of 1.3 μm InGaAsP vertical cavity lasers on GaAs substrates
Authors: Dudley J. J. , Ishikawa M. , Babic D. I. , Miller B. I. , Mirin R. , Jiang W. B. , Bowers J. E. , Hu E. L.
Published: July 2002

We report lasing at temperatures as high as 144 °C in long-wavelength InGaAsP vertical cavity lasers. The devices are optically pumped and employ a novel cavity design using GaAs/AlAs quarter-wavelength stacks for one mirror. The characteristic temperature T0 of the device increases from 42 K at room temperature to 81 K at temperatures above 80 °C as the gain peak moves into resonance with the longer wavelength cavity mode.
Amorphization processes in ion implanted Si: Ion species effects
Authors: Motooka T. , Holland O. W.
Published: July 2002

Amorphization processes in Si+, P+, Ge+, and As+ ion implanted Si have been investigated using Raman spectroscopy and Rutherford backscattering spectrometry combined with computer simulations of the initial ion-beam-induced damage profiles. The crystal Si Raman peak at 520 cm−1 decreased, broadened, and shifted toward lower wave numbers as the doses were increased from 2 to 8×1014 cm−2 for both 100 keV Si+ and P+, and from 0.6 to 1.8×1014 cm−2 for both 175 keV Ge+ and As+. The maximum peak shifts prior to amorphization were ∼−6 cm−1 in all the samples suggesting that lattice softening is responsible for amorphization in all the ion species cases. The effects of ion species were analyzed by scaling the ion dose using calculated displacements per target atom (DPA). It was found that larger DPA was necessary to obtain the same peak shifts in the Si+ and P+ than in the Ge+ and As+ implantation cases. The results suggest that amorphization is controlled by divacancies generated by ion bombardment.
Metal deposition onto oxides: An unusual low initial sticking probability for copper on SiO2
Authors: Xu Xueping , Goodman D. Wayne
Published: July 2002

The initial sticking probability of copper on a thin silica film has been measured in the temperature range 90–700 K using temperature programmed desorption. The copper sticking probability depends markedly on the surface temperature, varying from 0.6±0.1 at 90 K to less than 0.1 above 400 K. Upon covering the silica surface with multilayer water, the sticking probability of copper increases to ∼1.0. These results imply that using a quartz crystal microbalance, even at 90 K, to monitor Cu deposition on silica (and likely other similar oxides) may lead to a significant error in the estimation of metal growth rate.
Electronic states created in p-Si subjected to plasma etching: The role of inherent impurities, point defects, and hydrogen
Authors: Awadelkarim O. O. , Gu T. , Mikulan P. I. , Ditizio R. A. , Fonash S. J. , Reinhardt K. A. , Chan Y. D.
Published: July 2002

Reactive ion etching and magnetically enhanced reactive ion etching with CHF3/O2 are employed to remove SiO2 from boron-doped Si substrates. Etch-induced gap states in the substrate are monitored using deep-level transient spectroscopy. The dominant state is found to be a donor with a hole binding energy of 0.36 eV. The state has been identified as that of the carbon-interstitial oxygen-interstitial pair. The depth profile of the pair is determined by two competing mechanisms: the pair generation and its electrical deactivation by atomic hydrogen. The latter process is especially prevalent in the presence of a magnetic field.
Strong improvement of diffusion length by phosphorus and aluminum gettering
Authors: Loghmarti M. , Stuck R. , Muller J. C. , Sayah D. , Siffert P.
Published: July 2002

The minority carrier diffusion length in polycrystalline silicon has been strongly improved by using several gettering processes. These processes include different surface treatments followed by conventional thermal annealing (CTA) performed at temperatures between 800 and 950 °C. The n+p structures with a back lapped surface exhibit a maximum increase of the diffusion length from 35 to 140 μm for 45 min annealing duration at temperatures of 900 and 950 °C. The realization of a back surface field (BSF) on the lapped surface by aluminum deposition followed by a CTA cycle at 950 °C, with slow cooling rate (2 °C/min) induces a strong additional gettering, resulting in the increase of the minority carrier diffusion length up to 350%.
X-ray diffraction reciprocal space mapping of a GaAs surface grating
Authors: Gailhanou M. , Baumbach T. , Marti U. , Silva P. C. , Reinhart F. K. , Ilegems M.
Published: July 2002

A GaAs surface grating (period 574 nm) is analyzed by four crystal-six reflection x-ray diffraction. Two-dimensional measurements in the vicinity of the 004 GaAs reciprocal lattice point show satellites in the transverse direction related to the periodicity of the grating. A cross pattern, centered on the 004 GaAs reciprocal lattice point, is formed by these satellites. An explanation is given by a model which includes the influence of transmission through the surface pattern on the substrate diffraction.
Time resolved luminescence study of recombination processes in electroluminescent polymers
Authors: Lemmer U. , Mahrt R. F. , Wada Y. , Greiner A. , Bässler H. , Göbel E. O.
Published: July 2002

Picosecond luminescence studies on poly(p-phenylene vinylene) (PPV) and related compounds in the temperature range of 10–300 K are reported. We identify a fast nonradiative and considerably slower radiative recombination channel. The fastest decay is observed in PPV. In the phenyl substituted derivative poly(phenyl-p-phenylenevinylene) a significant contribution from a slow component (∼1.3 ns) is found. Dilution of the polymer in a blend leads to an increase of the contribution of the slow component. We attribute the fast decay to luminescence quenching due to energy dependent trapping of mobile excitations whereas the slow component reflects the radiative recombination.
Band-gap narrowing in ordered Ga0.47In0.53As
Authors: Arent D. J. , Bode M. , Bertness K. A. , Kurtz Sarah R. , Olson J. M.
Published: July 2002

We report the first observation of band-gap energy reduction in Ga0.47In0.53As deposited on (100) InP by atmospheric pressure organometallic vapor phase epitaxy due to CuPt-type ordering. A reduction of more than 65 meV in the band-gap energy is observed for lattice-matched samples that show strong CuPt-like ordering by transmission electron microscopy. By comparison samples that show no CuPt-like ordering diffraction signatures, do not have reduced band-gap energies. Studies of the influence of growth parameters on the band-gap energy indicate a U-shaped dependence on the growth temperature with a minimum around 550 °C and decreasing band-gap energies with increasing growth rate (at a constant V/III ratio) over the range 0.5–4 μm/h.
Characteristics of electron traps in In0.5Ga0.5P generated by recombination enhanced defect reactions
Authors: Kim M. G. , Kwon S. D. , Kim C. H. , Lee J. B. , Choe Byung-Doo , Lim H.
Published: July 2002

We report the observation of a new type of intrinsic defect in n-In0.5Ga0.5P which can be generated by recombination enhanced defect reaction (REDR) mechanism. It is observed that the increases of the concentrations of this defect and of another native defect due to REDR have nearly linear time dependence before saturation. This observation and other experimental results suggest that the two observed defects are complex defects. Other electrical properties of these defects such as alloy broadening effect on the thermal ionization energy are also described.
Short terahertz pulses from semiconductor surfaces: The importance of bulk difference-frequency mixing
Authors: Saeta Peter N. , Greene Benjamin I. , Chuang Shun Lien
Published: July 2002

The crystallographic orientation dependence of the far-infrared (FIR) light generated at the (001) surface of a zincblende semiconductor is shown to derive principally from bulk difference-frequency mixing. A strong modulation is observed for 1-GW/cm2 pulses on InP, which demonstrates that the radiated FIR wave produced by bulk optical rectification is comparable to that generated by the transport of photoinjected carriers. Using the bulk rectification light as a clock, we show that more than 95% of the light produced from an InP (111) crystal by 100-fs, 100-μJ pulses is generated in a time shorter than the excitation pulse.
Defects in porous silicon investigated by optically detected and by electron paramagnetic resonance techniques
Authors: Meyer B. K. , Hofmann D. M. , Stadler W. , Petrova-Koch V. , Koch F. , Omling P. , Emanuelsson P.
Published: July 2002

The defect properties of as-etched and annealed porous silicon are studied by electron paramagnetic resonance (EPR) and optically detected magnetic resonance (ODMR). The paramagnetic defect observed is closely related to the Pb0 center at the Si/SiO2 interface. In EPR a minimum defect density of 1016 cm−3 is observed for the as-etched silicon, which reaches a maximum of 8×1018 cm−3 for samples annealed at about 400 °C. In the ODMR experiments, the same dangling bond center is observed on the 1.5 eV luminescence band enhancing the luminescence—but with increased sensitivity and as a decrease of the emission intensity in the infrared emission band at 1 eV of porous silicon.