bluuebunny/crossref_metadata_2025 huggingface dataset:
Organization of a Major International Sporting Event in the Midst of Covid-19 Pandemic in Eastern India: An Observational Review Detailing Health and Safety Measures
Authors: Kar Sonali , Kar Ansuman , Priyanka B. Lakshmi
Published: February 2023

Sports have been long neglected in our country both in terms of excelling in any sport and hosting events. Even if the country hosts, usually the opportunity goes to the capital city or other metros. Covid 19 pandemic had further compounded the stalemate over the last two years due to evidence against crowd events. But, Odisha state has taken everyone by surprise by hosting the World cup men’s hockey and the study is a basic descriptive observational showcase of health-related safety measures that were ascertained during the matches. The event not only let 3 cities in the state namely Bhubaneswar, Rourkela, and Cuttack get a makeover in terms of tourist destinations but also a fast track check was done on the safety preparations within the stadium. Tool used was a self-devised pre-tested checklist as per Event management standards and the results were that almost international standards were adhered to in terms of crowd management for parking, entry points, sitting arrangements, water, and toilets. Covid appropriate behavior was disregarded due to zero case reporting for over a year. Public was also satisfied with the preparedness and there was a renewed enthusiasm for sports for all age groups, which was a welcome sight after the restricted activity during Covid. The state has taken baby steps towards establishing itself on the Global map as a state that could take up Global sporting events effortlessly. It has added advantage of propagating the rich heritage and culture of the state as well as promoting sports among the public.
Eco-friendly Management of Fruit Fly (Bactrocera cucurbitae) Infesting Bitter Gourd
Authors: Akter Mst. Munjuri , Zohora Fatema Tuz , Akter Most. Mahmuda , Farhana Fatima
Published: February 2023

Aims: This study aimed to evaluate some Bio insecticide   and management against fruit fly in bitter gourd.

Study Design: The experiment was laid out at a randomized complete block design with three replications.

Place and Duration of Study: Experimental farm of Sher-e-Bangla Agricultural University, Bangladesh during the period from February,2022 to july,2022.

Methodology: The experiment consisted of seven treatments viz. T1(Lycomax 2g/lit of water+ Cutrac+ Yellow Sticky trap+ Sanitation), T2(Lycomax 2g/lit of water+ Ceranock+ Yellow Sticky trap+ Cultural control), T3 (Biomax M 1.2 EC+ Cuelure+ Yellow Sticky trap), T4 (Lycomax 2g/ lit of water+ Yellow Sticky trap), T5 (Biomax M 1.2 EC + Ceronock+ Cutrac), T6 Sanitation+ Cultural control+ Cuelure), T7 (Untreated Control) were used at 7 days interval.

Results: The degree of the fruit fly (Bactrocera cucurbitae) infestation at various phases of bitter gourd ripening was investigated in the field and in the lab, as well as the effectiveness of some bio-pesticides and other control methods used in combination. Among all treatments the highest number of fruit fly was captured in Lycomax 2g/lit of water+ Ceranock+ Yellow Sticky trap+ Cultural control treated plot.Healthy fruit per plant (9.50 fruit/plot) also found from T2 treated plot. whereas the maximum amount of infested fruit number (12.21 fruit/plot), number of punctures per fruit (6.74 puncture/fruit) and infested fruit weight (77.13gm) was found from the control plot. The highest percentage reduction of puncture number over control resulted in treatment T2 treated plot which was 92.58% which is near to treatment T4 (85.16%) and also highest amount of healthy fruit weight (232.75 gm) came from T2. In terms of maximum yield (2.54 kg/ plot) gained from Lycomax 2g/lit of water+ Ceranock+ Yellow Sticky trap+ Cultural control treated plot (T2). From the study it was found that all the treatments except control (T7) work effectively against fruit fly infestation.

Conclusion: It is concluded that T2 treatment (Lycomax 2g/lit of water+ Ceranock+ Yellow Sticky trap+ Cultural control) was the best one among the all trerments.
Design and Fabrication of Portable Motor-Operated Tiller Machine
Authors: Saxena Rahul
Published: February 2023

Agriculture has been an integral part of the human ecosystem. However, traditional farming methods require a lot of human effort and are very time-consuming. Farm tilling is one of the most labor intensive operations in agriculture. Manual tiling of fields is very strenuous task while tractors incur high capital along with heavy fuel consumption costs. This low-cost portable motor-operated tiller machine is a one-stop modern solution to enhance the conventional agriculture methods of farming, as it reduces the human effort, at a very negligible price using motorized tilling mechanism. The electric power tiller helps reduce the time and cost involved in tilling using a smart portable design thereby increasing the productivity and efficiency in agriculture.
The Effect of Industrial Waste Effluent on Waterquality: A Case Study of Otamiri River, Owerri, Imo State
Authors: Mmonwuba N. C. , Mmaduabuchi Anaduaka , Azubuike Ohamadike , Nzube Theophilus Nweke , Chukwuemelie Chioke
Published: February 2023

The study assessed the impact of effluent discharges on the quality of Otamiri River in Imo state, Nigeria. Six water samples were collected at discharge points where the industries discharge their effluents and abattoir. Samples that were collected upstream and downstream were analyzed in the field and in the lab using standard procedures.  The source of pollution is attributable to industrial and abattoir activities whose effluent discharges impact the quality of Otamiri River. Therefore, without any treatments, the River cannot be used for any residential purposes in its current condition. It is advised that the river be periodically monitored and that cost-effective manufacturing technology, such as on-site waste separation and reduction, effluent recycling techniques, be introduced.
Primary structures of two homologous subunits of PA28, a γ‐interferon‐inducible protein activator of the 20S proteasome
Authors: Joon Young Ahn  , Nobuyuki Tanahashi  , Kin-ya Akiyama  , Hiroshi Hisamatsu  , Chiseko Noda  , Keiji Tanaka  , Chin Ha Chung  , Naoki Shibmara  , Willy Patricia J. , Mott Joni D. , Slaughter Clive A. , DeMartino George N.
Published: July 2002

The primary structures of two proteins that comprise PA28, an activator of the 20S proteasome, have been determined by cDNA cloning and sequencing. These protein subunits, termed PA28α and PA28β, are about 50% identical to one another and are highly conserved between rat and human. PA28α and PA28β are homologous to a previously described protein, Ki antigen, whose function is unknown. PA28α, but neither PA28β nor Ki antigen, contains a ‘KEKE motif’, which has been postulated to promote the binding of proteins having this structural feature. PA28α and PA28β were coordinately regulated by γ‐interferon, which greatly induced mRNA levels of both proteins in cultured cells. The mRNA level of the Ki antigen also increased in response to γ‐interferon treatment, but the magnitude of the increase was less than that for the PA28s, and the effect was transient. These results demonstrate the existence of a new protein family, at least two of whose members are involved in proteasome activation. They also provide the basis for future structure/function studies of PA28 subunits and the determination of their relative physiological roles in the regulation of proteasome activity.
Two different modes of cyclin Clb2 proteolysis during mitosis in Saccharomyces cerevisiae
Authors: Bäumer Matthias , Braus Gerhard H , Irniger Stefan
Published: July 2002

Sister chromatid separation and mitotic exit are triggered by the anaphase‐promoting complex (APC/C) which is a multi‐subunit ubiquitin ligase required for proteolytic degradation of various target proteins. Cdc20 and Cdh1 are substrate‐specific activators of the APC/C. It was previously proposed that Cdh1 is essential for proteolysis of the yeast mitotic cyclin Clb2. We show that Clb2 proteolysis is triggered by two different modes during mitosis. A fraction of Clb2 is degraded during anaphase in the absence of Cdh1. However, a second fraction of Clb2 remains stable during anaphase and is degraded in a Cdh1‐dependent manner as cells exit from mitosis. Most of cyclin Clb3 is degraded independently of Cdh1. Our data imply that degradation of mitotic cyclins is initiated by a Cdh1‐independent mechanism.
Structural alterations of the mitotic apparatus induced by the heat shock response in Drosophila cells
Authors: Debec Alain , Marcaillou Christiane
Published: July 2002

The general architecture of the mitotic apparatus was studied at the ultrastructural level in Drosophila cultured cells. Its two main characteristics are a very polarized spindle and a strong compartmentalization, ensured by large remnants of the nuclear envelope. Such compartmentalization has previously been reported for the rapid syncytial divisions of the early embryo; a similar finding in these cells with a long cycle strongly suggests that this organization constitutes a general mechanism for mitosis in Drosophila. We followed the modifications of these structures after a heat shock of 20, 50 or 120 min at 37°C. Contrary to interphase cells, mitotic cells appear very sensitive to hyperthermia. This stress treatment induced a disruption of the mitotic spindle, a reappearance and an extension of the Golgi apparatus, an inactivation of microtubule nucleation and a disorganization of the centrosome. This organelle seems the first to be affected by the heat shock response. The centrosome is not only inactivated, but also is structurally affected. During the recovery phase after heat stress, the mitotic cells presented a remarkable ring‐shaped accumulation of electrondense material around the centrioles. We conclude that in Drosophila cells the mitotic phase, and more specifically the centrosome, are targets of the stress response.
Programmed Escherichia coli Cell Lysis by Expression of Cloned T4 Phage Lysis Genes
Authors: Morita Masatomo , Asami Kazuhiro , Tanji Yasunori , Unno Hajime
Published: July 2002

Self‐disruptive Escherichia coli that produces foreign target protein was developed. E. coli was co‐transformed with two vector plasmids, a target gene expression vector and a lysis gene expression vector. The lytic protein was produced after the expression of the target gene, resulting in simplification of the cell disruption process. In this study, the expression of cloned T4 phage gene e or t was used for the disruption of E. coli that produced β‐glucuronidase (GUS) as a model target protein. The expression of gene e did not lead to prompt cell disruption but weakened the cell wall. Resuspension with deionized water facilitated cell lysis, and GUS activity was observed in the resuspended liquid. Expression of gene e at mid logarithmic growth phase was the optimal induction period for GUS production and release. On the other hand, the expression of gene t induced immediate cell lysis, and intracellular GUS was released to the culture medium. Maximum GUS production was obtained when gene t was induced at late logarithmic growth phase.
Mist Deposition onto Hairy Root Cultures: Aerosol Modeling and Experiments
Authors: Wyslouzil Barbara E. , Whipple Michelle , Chatterjee Chinmay , Walcerz Douglas B. , Weathers Pamela J. , Hart Douglas P.
Published: July 2002

We analyzed the applicability of the standard models for aerosol deposition in randomly packed fibrous filter beds to mist deposition across a bed of hairy roots in the nutrient mist bioreactor. Although the assumptions inherent in the models are met on a local level, the overall structure of the root bed introduces some uncertainty into the correct choice of root packing fraction and gas velocity required by the model. For reasonable parameter values, the minimum in the deposition efficiency curves is close to the peak in the mist number and mass distributions, and good penetration of the root bed is possible. We then measured the deposition of mist across a packed bed of Artemisia annua transformed roots as a function of droplet size, bed length, and gas flow rate at a root packing fraction α = 0.5. We compared the experimental measurements with the predictions of the aerosol deposition model and found good agreement between the measured and predicted values for the diameter where the deposition efficiency across the bed is 50%, D0.5. Agreement between the model and the experiments broke down when the flow rate was increased to the point where the creeping flow assumptions were no longer valid.
Population‐based study of infants born at less than 28 weeks’ gestation in New South Wales, Australia, in 1992–3
Authors: Sutton  , Bajuk  , And The New South Wales Neonatal Intensive Care Unit Study G
Published: July 2002

The aims of the study were to use the population base of New South Wales (NSW) to study all births from 20 to 27 weeks’ gestation in 1992–3 and to compare two data sources for perinatal deaths. The prospective population‐based statewide audit (NICUS) of infants admitted to tertiary neonatal intensive care units (NICUs) in NSW was used to collect data on infants less than 28 weeks’ gestation registered in 1992–3. This audit also surveyed the 160 obstetric hospitals in NSW to ascertain information on stillbirths and early neonatal deaths in the study period. The NSW midwives data collection (MDC) was the other source of information on stillbirths and labour ward deaths. Data were analysed using SAS. In 1992–3 in NSW 1170 infants were born at 20–27 weeks’ gestation. There were 556 stillbirths and 614 live births, of whom 180 (29.3%) died in the labour ward and 434 (70.7%) were admitted to a tertiary NICU. Sixty‐six per cent of stillbirths were identified by both data collections, 16.5% by the MDC only and 17% by NICUS only. There was a high major congenital anomaly rate (18.5%) among the stillbirths. Two‐thirds of the infants admitted to NICUs survived to 1 year. Information was available on at least one follow‐up parameter for 89% (255/288) of the survivors to 12 months (corrected age). Of the 244 infants who had a neurological assessment by a paediatrician, 17% were diagnosed to have cerebral palsy. Eleven per cent of the 239 who had a formal Griffiths developmental assessment had a major intellectual disability. Five (2% of 255) of the 1‐year‐olds were blind, and 12 (4.7% of 255) had bilateral hearing aids. Seventy‐one per cent of the infants examined at 1 year did not have a major disability. For accurate perinatal death data, collection from more than one source is recommended. Infants born at 20–27 weeks’ gestation contribute 40% of all stillbirths in NSW, most of the costs of neonatal intensive care as well as the costs of long‐term morbidity. In Australia in the early 1990s, the survival of infants born at less than 28 weeks’ gestation was best from 26 weeks gestational age onwards. Long‐term morbidity did not change from that of earlier cohorts. The most common major disability was cerebral palsy.
Changes in Public Attitudes Toward Epilepsy in Hungary: Results of Surveys Conducted in 1994 and 2000
Authors: Mirnics Zsuzsanna , Czikora Györgyi , Závecz Tibor , Halász Péter
Published: July 2002

Summary: Our study investigated public attitudes toward epilepsy, and knowledge and understanding of epilepsy in Hungary. We compared changes of public attitudes in the last six years, hypothesizing a trend of positive changes because of recent national initiatives for acceptance and integration of people with epilepsy (e.g., participation of Hungary in the “Out of the Shadows” world campaign). We also studied how the demographic background of the respondents affects awareness, understanding, and attitudes toward epilepsy. Using a questionnaire design, we conducted a public opinion poll with a representative sample of 1,000 people in 1994 and 6 years later, in 2000. Hungarian respondents were most prejudiced regarding employment of people with epilepsy. In recent years, significant decreases in prejudice rates were found regarding all attitude aspects (marriage, children associating, work). Significant background effects of demographic variables were also apparent: differences by age, education, residence, and family status were found. Some culture‐specific characteristics of understanding epilepsy could be observed. Significant positive attitude changes from 1994 to 2000 confirm the need for and potentialities of education of the public and informational initiatives. Demographic influences and culture‐specific characteristics could be of relevance in designing public education for different target groups.
Breast Reconstruction with the Free Bipedicled Inferior TRAM Flap by Anastomosis to the Proximal and Distal Ends of the Internal Mammary Vessels
Authors: Li Senkai , Mu Lanhua , Li Yangquin , Xu Jun , Yang Mingyong , Zhao Zhenmin , Liu Yuanbo , Li Junlai , Ling Yichun
Published: July 2002

Breast reconstruction after traditional radical mastectomy is particularly challenging for the plastic surgeon. Not only the breast, but subclavian and anterior axillary-fold deformities need to be corrected. An entire TRAM flap (including zone IV) is required, and bipedicled deep inferior epigastric vessels are needed to insure that the entire flap will survive completely. However, on the chest, it is difficult to locate the two suitable sets of recipient vessels for the two pedicles. The thoracodorsal vessels have usually been damaged during axillary dissection or radiation therapy.

In the past, the proximal ends of the internal mammary artery and vein (IMA, IMV) have been used as recipient vessels with free flaps, with ligation of the distal ends. These authors have used both the proximal and distal ends of the IMA and IMV as recipient vessels for end-to-end anastomoses to the bipedicled deep inferior epigastric vessels (DIEA, DIEV) in seven clinical cases, with very satisfactory results obtained.

Anatomic studies of the IMA and IMV were done in 10 dogs and two active patients, including studying hemodynamic changes at the proximal and distal ends of the IMA, and evaluation of perfusion units in the free bilateral TRAM flap. In the animal experiments, the mean pressure at the distal ends was 86/77 mmHg (left sides) and 87/78 mmHg (right sides); pressure was 63 to 71 percent of the proximal ends (p<0.05). There was no statistically significant difference between the pressures on the left and right sides. In the two patients, and in 5 others, the pressure at the distal ends was 66 and 58 mmHg, which was 75 to 77% of the pressure at the proximal ends. The blood flow at the two anastomotic stomas was similar in a 5-year follow-up.

The clinical and experimental studies showed that the distal IMA has reduced perfusion pressure, but that it provides excellent flow and flap perfusion, allowing reliable use of two pedicles for survival of the entire flap.
Negative transconductance via gating of the quantum well subbands in a resonant tunneling transistor
Authors: Beltram Fabio , Capasso Federico , Luryi Serge , Chu Sung-Nee G. , Cho Alfred Y. , Sivco Deborah L.
Published: July 2002

Operation of a new resonant tunneling transistor is reported in the AlGaAs/GaAs material system. The device contains an undoped quantum well collector separated from a heavily doped emitter by a thin tunnel barrier. The collector is gated and the gate field controls resonant tunneling characteristics ‘‘from behind’’ via a combination of the generalized Stark effect and the quantum capacitance effect. The common-collector characteristics show negative differential resistance at a fixed gate bias and negative transconductance at a fixed emitter bias. Excellent agreement is found between the measured and calculated shifts of the peaks of the current-voltage characteristics.
First cw operation of a Ga0.25In0.75As0.5P0.5-InP laser on a silicon substrate
Authors: Razeghi M. , Defour M. , Blondeau R. , Omnes F. , Maurel P. , Acher O. , Brillouet F. , C-Fan J. C. , Salerno J.
Published: July 2002

We report the first successful room-temperature cw operations of a Ga0.25 In0.75 As0.5 P0.5 -InP buried ridge structure laser emitting at 1.3 μm grown by two-step low-pressure metalorganic chemical vapor deposition on a silicon substrate. An output power of 20 mW with an external quantum efficiency of 16% at room temperature has been obtained. A threshold current as low as 45 mA under cw operation at room temperature has been measured. The first cw aging test at room temperature, at 2 mW during 5 h, shows a very low degradation (ΔI/I≤5%).
Raman spectroscopy of InSb/CdTe heterostructures: Improved interface quality obtained by Cd overpressure during molecular beam epitaxial growth
Authors: Zahn D. R. T. , Williams R. H. , Golding T. D. , Dinan J. H. , Mackey K. J. , Geurts J. , Richter W.
Published: July 2002

In recent photoemission and Raman experiments interfacial layers of indium telluride together with liberated antimony were found to be formed during the molecular beam epitaxial growth of CdTe on InSb(100) at elevated substrate temperatures (TS≥200 °C). We have previously suggested that the application of a sufficiently large Cd overpressure during growth is likely to suppress the formation of interfacial layers and enable successful epitaxial growth of CdTe. In this letter we present Raman spectra revealing that a flux ratio of Cd/Te=3 during growth effectively suppresses indium telluride formation leading to largely improved InSb/CdTe interfaces.
Surface recombination current and emitter compositional grading in N
p
n and P
n
p GaAs/AlxGa1−xAs heterojunction bipolar transistors
Authors: de Lyon T. J. , Casey H. C. , Enquist P. M. , Hutchby J. A. , SpringThorpe A. J.
Published: July 2002

An experimental study of current gain in Npn and Pnp GaAs/AlxGa1−xAs heterojunction bipolar transistors (HBTs) with either compositionally graded or abrupt base-emitter heterojunctions is reported. In both Npn and Pnp device structures, linear compositional grading increases the amount of base current and lowers the transistor current gain from that observed in devices with abrupt base-emitter heterojunctions. Analysis of the dependence of the base current on emitter mesa size indicates that surface recombination dominates the Npn and Pnp base current in both the abrupt and graded devices. Taken together, these results suggest that the magnitude of the surface recombination current in Npn and Pnp GaAs/AlxGa1−xAs HBTs depends not only on the surface recombination velocity of the GaAs base free surface, but also on the energy barrier presented by the emitter to minority carriers attempting to enter the surface channel at the emitter mesa surface. Linear compositional grading of the emitter results in a lowering of this barrier and an increase in base current associated with carrier injection to the transistor surface.
Selective area laser photodeposition of transparent conductive SnO2 films
Authors: Kunz R. R. , Rothschild M. , Ehrlich D. J.
Published: July 2002

The deposition of SnO2 films has been demonstrated using an ArF (193 nm) excimer laser to drive the photochemical reactions of mixed SnCl4 and N2 O vapors. Without any annealing, films 100 nm thick grown on room-temperature substrates have resistivities as low as 0.04 Ω cm. The optical band gap of 3.20 eV and transmission cutoff wavelength of 330 nm compare favorably with the best films obtained using alternate higher temperature techniques. Subsequent annealing does not increase the film’s conductivity. Selective area growth of 10-μm-wide lines has been performed using proximity printing. The maximum temperature excursion during the laser pulse is estimated to be 300–400 °C.
Heteroepitaxial growth of Ge films on (100) GaAs by pyrolysis of digermane
Authors: Eres Djula , Lowndes Douglas H. , Tischler J. Z. , Sharp J. W. , Geohegan D. B. , Pennycook S. J.
Published: July 2002

Pyrolysis of high-purity digermane (Ge2 H6 ) has been used to grow epitaxial Ge films of high crystalline quality on (100) GaAs substrates in a low-pressure environment. X-ray double-crystal diffractometry shows that fully commensurate, coherently strained epitaxial Ge films can be grown on (100) GaAs at digermane partial pressures of 0.05–40 mTorr for substrate temperatures of 380–600 °C. Amorphous films also were deposited. Information about the crystalline films surface morphology, growth mode, and microstructure was obtained from scanning electron microscopy, cross-section transmission electron microscopy, and in situ reflectivity measurements. The amorphous-to-crystalline transition temperature and the morphology of the crystalline films were both found to depend on deposition conditions (primarily the incidence rate of Ge-bearing species and the substrate temperature). Epitaxial growth rates using digermane were found to be about two orders of magnitude higher than rates using germane (GeH4 ) under similar experimental conditions.
Zinc-blende MnTe: Epilayers and quantum well structures
Authors: Durbin S. M. , Han J. , O Sungki , Kobayashi M. , Menke D. R. , Gunshor R. L. , Fu Q. , Pelekanos N. , Nurmikko A. V. , Li D. , Gonsalves J. , Otsuka N.
Published: July 2002

Epilayers of the previously hypothetical zinc-blende MnTe have been grown by molecular beam epitaxy. Epitaxial layers (0.5 μm thick) of MnTe were characterized using x-ray diffraction and transmission electron microscopy; optical reflectance measurements indicate a band gap of ∼3.2 eV. A series of strained single quantum well structures was fabricated with zinc-blende MnTe forming the barrier to CdTe quantum well regions; photoluminescence spectra indicate optical transitions corresponding to strong electron and hole confinement.
Selectively doped double-heterojunction lateral current injection ridge waveguide AlGaAs/GaAs laser
Authors: Yasuhira N. , Suemune I. , Kan Y. , Yamanishi M.
Published: July 2002

A new type of laser structure which utilizes the selectively doped double-heterojunction (SDH) structure for lateral current injection (LCI) was proposed. A ridge waveguide AlGaAs/GaAs laser based on the SDH-LCI scheme was demonstrated to lase at the very low threshold current of 11.5 mA. The compatibility of this new laser structure with electronic devices is discussed.
Carbon implantation in InGaAs and AlInAs
Authors: Pearton S. J. , Hobson W. S. , Kinsella A. P. , Kovalchick J. , Chakrabarti U. K. , Abernathy C. R.
Published: July 2002

It is shown for the first time that carbon behaves predominantly as an acceptor in InGaAs and AlInAs under co-implantation conditions. The co-implanted ion, regardless of species, acts to create vacant lattice sites for occupation by the carbon. Implantation of 40 keV carbon ions alone at doses between 5×1012 and 5×1014 cm−2 followed by annealing in the range 600–950 °C for 10 s does not produce any measurable electrical activity in either material. In InGaAs, carbon implantation at 5×1014 cm−2 produced net acceptor activations of 20, 11, or 6% for Ga, Ar, or As co-implantation, respectively, at the same doses after 700 °C, 10 s anneals. Similar results were obtained for AlInAs after annealing at 900 °C. The diffusion coefficient for carbon is estimated from secondary-ion mass spectrometry measurements to be less than 3.3×10−14 cm2  s−1 at 800 °C in both materials.
Self-mode-locking of a semiconductor laser using positive feedback
Authors: Derickson D. J. , Helkey R. J. , Mar A. , Morton P. A. , Bowers J. E.
Published: July 2002

A new mode-locking technique, self-mode-locking, is described which uses the detected optical pulses from the mode-locked laser as the active driving source. This technique forms narrow-width mode-locked optical pulses at low repetition rates without the use of a microwave synthesizer.
Does luminescence show semiconductor interfaces to be atomically smooth?
Authors: Warwick C. A. , Jan W. Y. , Ourmazd A. , Harris T. D.
Published: July 2002

Luminescence spectra from quantum wells are routinely interpreted in terms of atomically smooth and atomically abrupt interfaces. Here we show that this interpretation is inconsistent with photoluminescence, photoluminescence excitation, and quantitative microscopic (chemical lattice imaging) results. We argue that the discussion of interfacial roughness in terms of ‘‘an island size’’ is too naive. A full characterization of an interface requires the description of a ‘‘roughness spectrum,’’ specifying the amplitude of the interfacial corrugation versus corrugation wavelength over the relevant length scale.
Room-temperature InAsxSbyP1−x−y light-emitting diodes for CO2 detection at 4.2 μm
Authors: Krier A.
Published: July 2002

By using a graded composition InAsSbP quaternary layer grown by liquid phase epitaxy it was possible to fabricate light-emitting diodes which emit near 4.2 μm at room temperature, corresponding to the fundamental absorption of CO2 gas.
Carrier recombination rate in GaAs-AlGaAs single quantum well lasers under high levels of excitation
Authors: Wang P. , Lee K. K. , Yao G. , Chen Y. C. , Waters R. G.
Published: July 2002

The carrier recombination rate in GaAs-AlGaAs single quantum well layers is investigated using a small-signal technique for carrier densities from 1017 to 1019/cm3. For carrier densities up to mid 1018/cm3, the inverse of the differential carrier lifetime, 1/τd, increases linearly with the carrier density. The differential rate, however, saturates at higher carrier densities and remains nearly constant for carrier densities higher than 1019/cm3. The deviation from the bulk recombination behavior is due to a portion of the injected carriers populating the semicontinuum states where the rate for the radiative transition is much smaller. The experimental data indicate that the runaway increase of threshold current with decreasing cavity length commonly observed in the short-cavity lasers is mainly due to the loss of carrier confinement at high carrier densities rather than due to fast carrier-depleting processes, such as Auger recombination.
Optical and structural characterization of evaporated zirconia films
Authors: Krishna M. Ghanashyam , Rao K. Narasimha , Mohan S.
Published: July 2002

Thin films of zirconia have been deposited using a reactive electron beam evaporation technique onto unheated alumina and fused silica substrates. The films were post annealed in the range 300–850 °C. The influence of post-deposition conditions on the optical properties like refractive index and absorption and nonoptical properties like structure have been studied. The structural transitions were determined using infrared (IR) absorption and x-ray diffraction. Preliminary results of studies on the correlation between x-ray diffraction and IR absorption data for structural characterization are reported. It has been shown that the refractive index values change considerably with each structural transition, although the optical absorption does not seem to be very adversely affected by post-deposition annealing. Post-deposition annealing resulted in the formation of the cubic phase at 500 °C which transformed to the tetragonal phase at 700 °C and finally monoclinic phase at 800 °C. The above-mentioned phases were only the major phases and post-deposition annealing did not result in single-phase material.
Characterization of the native oxide of CuInSe2 using synchrotron radiation photoemission
Authors: Nelson Art J. , Gebhard Steven , Kazmerski L. L. , Colavita Elio , Engelhardt Mike , Höchst Hartmut
Published: July 2002

Synchrotron radiation soft x-ray photoemission spectroscopy was used to investigate the native oxide of n-type single-crystal CuInSe2. Photoemission measurements were acquired on the oxide surface before and after removal using sputter etching. Observed changes in the valence-band electronic structure as well as changes in the In 4d and Se 3d core lines were correlated with the interface chemistry at the oxide/CuInSe2 interface. These results show the native oxide to be composed of an In2O3 outer layer (no SeO2) with an additional Cu2Se interface layer.
Effect of oxygen on minority-carrier lifetime and recombination currents in Si1−xGex heterostructure devices
Authors: Ghani T. , Hoyt J. L. , Noble D. B. , Gibbons J. F. , Turner J. E. , Kamins T. I.
Published: July 2002

A p+-i-n diode structure is presented which is suitable for determining the recombination lifetime in thin Si1−xGex layers grown on Si. Electrical measurements and computer simulations are used to extract carrier lifetimes in Si1−xGex layers with various oxygen concentrations. The minority-carrier lifetime increases dramatically as the oxygen concentration in the Si1−xGex decreases from 3×1020 to less than 3×1017 cm−3. Lifetimes extracted from the p+-i-n diodes are consistent with those obtained from measurements on heterojunction bipolar transistors with high oxygen concentrations in the Si1−xGex base.
Scanning tunneling optical spectroscopy of semiconductors
Authors: Qian L. Q. , Wessels B. W.
Published: July 2002

Photoenhanced tunneling currents are measured with a scanning tunneling microscope (STM) for semiconductors illuminated with monochromatic light. The spectral response of the STM tunnel junction was measured over the spectral range of 0.8–1.5 eV. Optical spectra for p-type (111)Si, epitaxial n-type (100)InP, and p-type (100)GaAs were obtained.
Atomic layer epitaxy of gallium arsenide with the use of atomic hydrogen
Authors: de Keijser M. , van Opdorp C.
Published: July 2002

Monolayer atomic layer epitaxy of GaAs has been achieved between 430 and 500 °C by using alternating pulses of AsH3, Ga(CH3)3, and atomic hydrogen. Maintaining the susceptor temperature below 500 °C suppresses the unfavorable thermal decomposition of Ga(CH3)3 to Ga in the gas phase. The basic point of our growth method is that, notwithstanding these low temperatures, sufficiently fast surface kinetics for growth are maintained by activation with the atomic hydrogen pulses.
cw high-power diffraction-limited-beam operation from resonant optical waveguide arrays of diode lasers
Authors: Mawst L. J. , Botez D. , Roth T. J. , Peterson G. , Rozenbergs J.
Published: July 2002

Monolithic phase-locked resonant arrays of antiguides, resonant optical-waveguide (ROW) arrays, have been optimized for efficient in-phase-mode operation. Diffraction-limited, in-phase-mode continuous-wave (cw) operation is obtained from 20-element uniform arrays to 250 mW output power, with (front facet) external differential quantum efficiencies of 41%. Single longitudinal mode operation is observed below 100 mW cw. In-phase-operating devices with and without Talbot-type spatial filters are compared, and it is found that for ROW arrays Talbot-type spatial filters are not required.
Dichlorosilane effects on low-temperature selective silicon epitaxy
Authors: Lou Jen-Chung , Galewski Carl , Oldham William G.
Published: July 2002

Low-temperature selective silicon epitaxial growth using a dichlorosilane-hydrogen mixture in a low-pressure chemical vapor deposition hot-wall reactor has been studied. A simple HF vapor treatment effectively removes surface oxides and passivates the Si surface prior to reactor loading. The addition of a small concentration of dichlorosilane to the H2 ambient during the prebake at a temperature of 900 °C improves selective epitaxial quality both by maintaining an oxide-free surface, and by suppressing undercut of oxide-covered regions. With these process improvements defect-free, selectively overgrown Si epitaxial layers are achieved at deposition temperatures between 800 and 850 °C.
Oscillation wavelength and laser structure dependence of nonlinear damping effect in semiconductor lasers
Authors: Uomi K. , Tsuchiya T. , Aoki M. , Chinone N.
Published: July 2002

For the first time, the oscillation wavelength and the laser structure dependence of the K factor and of the nonlinear gain suppression coefficient ε in semiconductor lasers were systematically investigated. As a result, we suggest that the nonlinear gain effect can be explained by the spectral hole burning theory.
Three-terminal operation of the double-heterostructure optoelectronic switching laser
Authors: Taylor G. W. , Claisse P. R. , Cooke P.
Published: July 2002

The double-heterostructure optoelectronic switch is demonstrated as a three-terminal laser. The basic laser structure employs a graded index single quantum well (GRIN SQW) and implements the third-terminal injector as a self-aligned implant to the inversion channel. The implant simultaneously serves as the optical confining layer. Threshold currents of 500 A/cm2 are obtained and complete control of the switching characteristic is obtained with an input current density of 0.8 A/cm2.
Effect of annealing Sb/InP(110) interfaces and Schottky barrier formation of Ag on annealed Sb/InP(110) surfaces
Authors: Yamada Masao , Wahi Anita K. , Meissner Paul L. , Herrera-Gomez Alberto , Kendelewicz Tom , Spicer William E.
Published: July 2002

The effect of annealing one monolayer of Sb on p-InP on the surface Fermi level position and the band bending due to Ag deposition on these well-ordered surfaces have been studied using photoemission spectroscopy. The adsorption of one monolayer of Sb on p-InP gives a Fermi level position 0.85 eV above the valence band maximum (VBM). However, with increasing annealing temperature, the band bending decreases and recovers to nearly the flatband condition above 200 °C. The Fermi level movement of annealed InP shows a correlation with the surface stoichiometry of phosphorus and indium. Ag deposition on these annealed Sb/p-InP interfaces gives an anomalously low band bending of 0.5 eV above the VBM.
Low-temperature selective epitaxy by ultrahigh-vacuum chemical vapor deposition from SiH4 and GeH4/H2
Authors: Racanelli M. , Greve D. W.
Published: July 2002

Selective epitaxy of GexSi1−x in an ultrahigh-vacuum chemical vapor deposition reactor from SiH4 and GeH4/H2 is reported for the first time. Growth is performed at 600 °C on patterned wafers after an 800 °C bake which provides a clean silicon surface. Selective growth is maintained during a short incubation time. GeH4/H2 is found to increase the incubation time and the growth rate improving selectivity. Diodes fabricated from selectively grown films demonstrate high material and film/oxide interface quality.
Room-temperature cw operation at 2.2 μm of GaInAsSb/AlGaAsSb diode lasers grown by molecular beam epitaxy
Authors: Choi H. K. , Eglash S. J.
Published: July 2002

Gain-guided Ga0.84In0.16As0.14Sb0.86/Al0.75 Ga0.25As0.06Sb0.94 double-heterostructure lasers emitting at ∼2.2 μm have been operated cw at heat sink temperatures up to 30 °C. The maximum output powers obtained at 5 and 20 °C were 10.5 and 4.6 mW/facet, respectively. For pulsed operation of broad-stripe lasers 300 μm wide and 1000 μm long, the threshold current density was as low as 940 A/cm2, the lowest room-temperature value reported for diode lasers emitting beyond 2 μm.
Compensation effects in nitrogen-doped diamond thin films
Authors: Mort J. , Machonkin M. A. , Okumura K.
Published: July 2002

Diamond thin films have been doped with nitrogen during growth by the hot-filament technique. For nitrogen concentrations in the films, determined by quantitative secondary ion-mass spectroscopy (SIMS) exceeding about 3×1018 atoms/cc, a decrease of several orders of magnitude is observed in the electrical conductivity for temperatures at or above room temperature. Qualitatively, this decrease is as expected, assuming compensation of existing acceptor states in nominally undoped diamond thin films by substitutional nitrogen which is known to introduce a deep-lying donor level.
Properties of DX centers in AlxGa1−xAs co-doped with boron and silicon
Authors: Mooney P. M. , Tischler M. A. , Parker B. D.
Published: July 2002

AlxGa1−xAs co-doped with Si and B was investigated to determine the effect of B on the properties of DX centers. We found the deep level transient spectroscopy (DLTS) peak of the DX center to be unchanged and also observed large persistent photoconductivity (PPC), in samples containing boron in concentrations up to 6×1018 cm−3. Our finding that B has no significant effect on DX centers differs from an earlier report that the presence of low concentrations of B modified the DLTS spectrum of Si-doped GaAs under hydrostatic pressure.
Measurement of magnetic anisotropy of ferrimagnets near compensation
Authors: Hellman F.
Published: July 2002

The problem of measuring the magnetic anisotropy of a ferrimagnet is considered. It is shown that near magnetic compensation, an anomalous drop in the apparent magnitude of this anisotropy will be observed due to the effect of finite interlattice exchange coupling. Such a drop has been observed in the macroscopic anisotropy of amorphous rare-earth transition metal alloys and appeared previously inexplicable.
Low threshold, 290 fs erbium-doped fiber laser with a nonlinear amplifying loop mirror pumped by InGaAsP laser diodes
Authors: Nakazawa Masataka , Yoshida Eiji , Kimura Yasuo
Published: July 2002

290 fs soliton pulses at 1.56 μm have been successfully obtained for the first time from a laser-diode pumped erbium-doped fiber laser with a nonlinear amplifying loop mirror. The laser was pumped by InGaAsP laser diodes and the threshold for starting the pulse oscillation was 50 mW. The passive mode-locking continued to a pump power level as low as 10 mW. The repetition rate was uncontrollable and varied between the fundamental repetition rate of 5 MHz and 1.2–2 GHz.
Bragg confinement of carriers in a shallow quantum well
Authors: Salzman J. , Lenz G. , Baruch E. , Finkman E.
Published: July 2002

A novel Bragg confining structure is proposed and analyzed. The combination of a shallow quantum well with superlattice-Bragg reflectors makes it possible to tailor separately the eigen-energy, and the wave function of the Bragg confined state. Longer lifetimes and higher effective barriers than in previously proposed Bragg confining structures is possible with the present scheme. Photoluminescence at energies close to the highest direct bandgap of the material system in use is expected from the proposed structure.
Study of magnetic domains in amorphous ribbons by scanning electron acoustic microscopy
Authors: Urchulutegui M. , Piqueras J. , Aroca C.
Published: July 2002

Scanning electron acoustic microscopy (SEAM) has been used in the observation of domain walls in iron- and cobalt-based amorphous alloys ribbons. Controlled magnetic annealing experiments enabled the direct identification of domain walls in SEAM micrographs. Walls in perpendicular anisotropy regions of the high magnetostriction samples show a particular high contrast, probably related to the wall stress field.
Current fluctuations in double-barrier quantum well resonant tunneling diodes
Authors: Lin Yayun , van Rheenen Arthur D. , Chou Stephen Y.
Published: July 2002

The measurements of the spectral intensity of the current fluctuations in double-barrier quantum well resonant tunneling diodes as a function of temperature and bias current are reported. Two types of devices were studied: one with AlAs barriers and GaAs well and contact regions, and the other has Al0.3Ga0.7As barriers. The frequency range covered is 1 Hz–100 kHz and the temperature range is 78–400 K. The noise spectra are decomposed in a 1/f part, resulting in the magnitude of the 1/f noise, and contributions due to carrier trapping, resulting in the activation energies of the traps. It is found that a reduction of the Al content in the barrier material reduces the number of traps and further that the magnitude of the 1/f noise is practically independent of the temperature and of the Al content of the barrier.
Cascadable optical switching characteristics in vertical-to-surface transmission electrophotonic devices operated as vertical cavity lasers
Authors: Ogura Ichiro , Kosaka Hideo , Numai Takahiro , Sugimoto Mitsunori , Kasahara Kenichi
Published: July 2002

We examine the optical switching characteristics in vertical cavity surface-emitting laser-type vertical-to-surface transmission electrophotonic devices (VC-VSTEPs) with a pnpn structure. It is theoretically and experimentally demonstrated that both optical input/output characteristics are strongly influenced by the structure of the vertical cavity. With improvements in optical power output due to laser oscillation, optical switching speed is enhanced by two orders of magnitude compared to spontaneous emission-type VSTEPs. A 20-μm-square VSTEP with an optimized vertical cavity structure demonstrates a low optical switching energy of 2.2 pJ with a switching time of 10 ns, as low as spontaneous emission-type VSTEPs.
Submicron Si1−xGex/Si epitaxial structure formation by wet oxidation of amorphous Si-Ge layers
Authors: Prokes S. M. , Rai A. K.
Published: July 2002

Submicron buried epitaxial SixGe1−x structures have been formed by a wet oxidation process from amorphous SixGe1−x layers. Epitaxial features in the shape of buried ‘‘donut’’ regions as well as buried Ge-rich lines have been obtained by this method using initial particulate contaminants or patterned amorphous SiGe structures as the starting features. Oxide formation above the epitaxial structures has been examined, showing that the oxides formed in this process consisted of several layers, some containing both SiO2 and GeO2. The mechanism of formation is interpreted in terms of motion of both Si and Ge during the oxidation process.
Comparison of gallium and arsenic precursors for GaAs carbon doping by organometallic vapor phase epitaxy using CCl4
Authors: Hobson W. S. , Pearton S. J. , Kozuch D. M. , Stavola M.
Published: July 2002

The carbon doping properties of GaAs grown by low pressure (30 Torr) organometallic vapor phase epitaxy at 520–700 °C with CCl4 as the dopant precursor were compared for the four possible combinations of trimethylgallium (TMGa), triethylgallium (TEGa), arsine (AsH3), and tertiarybutylarsine (TBAs). Secondary ion mass spectrometry (SIMS), Hall measurements, and infrared absorption were used to characterize the GaAs:C layers. Very high C-doping concentrations (∼1020 cm−3) could be obtained using either TMGa or TEGa and AsH3. The use of TBAs instead of AsH3 led to a significant reduction in carbon incorporation, by approximately a factor of 5–10 per mole of As precursor over the growth temperature range examined. Hydrogen at significant concentrations (1–6×1019 cm−3) was detected by SIMS in GaAs: C layers grown at ≤550 °C utilizing all four combinations of Ga/As precursors. The existence of electrically inactive C-H complexes was confirmed by observation of the C-H stretching mode at 2635 cm−1. A post-growth anneal under helium at 550 °C for 60 s removed the C-H pairs resulting in a 50%–100% increase in hole concentration. There was no change in the hole concentration for GaAs:C grown at ≥600 °C, indicating negligible hydrogen passivation.
Large blueshifting of InGaAs/InP quantum-well band gaps by ion implantation
Authors: Zucker J. E. , Tell B. , Jones K. L. , Divino M. D. , Brown-Goebeler K. F. , Joyner C. H. , Miller B. I. , Young M. G.
Published: July 2002

We demonstrate that phosphorous ion implantation in InGaAs/InP quantum wells can be used to produce large (from 1550 to 1200 nm) blueshifts of the band edge. This reproducible technique of lateral band-gap control can be used in quantum-well photonic integrated circuits to produce regions of low-loss waveguide, e.g., for interconnects or large passive cavities. Phosphorous implants with subsequent p-type InP regrowth produces blueshifted quantum-well diodes with good reverse-bias characteristics and low-loss p-i(multiple quantum well)-n waveguides.