bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of Wide Bandgap Semiconductor Photonic Device Structures by Excimer Laser Micromachining
Authors: Zhao Qiang , Lukitsch Michael , Xu Jie , Auner Gregory , Niak Ratna , Kuo Pao-Kuang 
Published: September 2012

AbstractExcimer laser ablation rates of Si (111) and AlN films grown on Si (111) and r-plane sapphire substrates were determined. Linear dependence of ablation rate of Si (111) substrate, sapphire and AlN thin films were observed. Excimer laser micromachining of the AlN thin films on silicon (111) and SiC substrates were micromachined to fabricate a waveguide structure and a pixilated structure. This technique resulted in clean precise machining of AlN with high aspect ratios and straight walls.
Metal/GaN Contacts Studied by Electron Spectroscopies
Authors: Dumont J. , Caudano R. , Sporken R. , Monroy E. , Muñoz E. , Beaumont B. , Gibart P. 
Published: September 2012

AbstractAu/GaN and Cu/GaN Schottky contacts have been studied using X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Clean and stoechiometric GaN samples were obtained using in situ hydrogen plasma treatment and Ga deposition. The growth of Cu and Au follows Stranski-Krastanov and Frank van der Merwe modes respectively. The interfaces are sharp and non-reactive. Schottky barriers of 1.15eV for Au/GaN and 0.85eV for Cu/GaN were measured using XPS.
Focused Ion Beam Etching of Nanometer-Size GaN/AlGaN Device Structures and their Optical Characterization by Micro-Photoluminescence/Raman Mapping
Authors: Kuball M. , Benyoucef M. , Morrissey F.H. , Foxon C.T. 
Published: September 2012

AbstractWe report on the nano-fabrication of GaN/AlGaN device structures using focused ion beam (FIB) etching, illustrated on a GaN/AlGaN heterostructure field effect transistor (HFET). Pillars as small as 20nm to 300nm in diameter were fabricated from the GaN/AlGaN HFET. Micro-photoluminescence and UV micro-Raman maps were recorded from the FIB-etched pattern to assess its material quality. Photoluminescence was detected from 300nm-size GaN/AlGaN HFET pillars, i.e., from the AlGaN as well as the GaN layers in the device structure, despite the induced etch damage. Properties of the GaN and the AlGaN layers in the FIB-etched areas were mapped using UV Micro-Raman spectroscopy. Damage introduced by FIB-etching was assessed. The fabricated nanometer-size GaN/AlGaN structures were found to be of good quality. The results demonstrate the potential of FIB-etching for the nano-fabrication of III-V nitride devices.
Spectroscopy in Polarized and Piezoelectric AlGaInN Heterostructures
Authors: Wetzel C. , Takeuchi T. , Amano H. , Akasaki I. 
Published: September 2012

AbstractUniaxial wurtzite group-III nitride heterostructures are subject to large polarization effects with significant consequences for device physics in optoelectronic and transport device applications. A central aspect for the proper implementation is the experimental quantification of polarization charges and associated fields. In modulated reflection spectroscopy of thin films and heterostructures of AlGaInN we observe pronounced Franz-Keldysh oscillations that allow direct and accurate readings of the field strength induced by polarization dipoles at the heterointerfaces. In piezoelectric GaInN/GaN quantum wells this dipole is found to induce an asymmetry in barrier heights with a respective splitting of interband transitions. This splitting energy appears to reflect in the transitions of spontaneous and stimulated luminescence in the well. From these experiments the polarization dipole is identified as controllable type-II staggered band offset between adjacent barrier layers which can extend the flexibility in AlGaInN bandstructure design. The derived field values can serve as important input parameters in the further interpretation of the entire system.
A Tem study of GaN Grown by ELO on (0001) 6H-SiC
Authors: Ruterana P. , Beaumont B. , Gibart P. , Melnik Y. 
Published: September 2012

AbstractThe misfit between GaN and 6H-SiC is 3.5% instead of 16% with sapphire, the epitaxial layers have similar densities of defects on both substrates. Moreover, the lattice mismatch between AlN and 6H-SiC is only 1%. Therefore, epitaxial layer overgrowth (ELO) of GaN on AlN/6H-SiC could be a route to further improve the quality of epitaxial layers. AlN has been grown by Halide Vapour Phase Epitaxy (HVPE) on (0001) 6H-SiC, thereafter a dielectric SiO2 mask was deposited and circular openings were made by standard photolithography and reactive ion etching. We have examined GaN layers at an early stage of coalescence in order to identify which dislocations bend and try to understand why. The analysed islands have always the same hexagonal shape, limited by {0110} facets. The a type dislocations are found to fold many times from basal to the prismatic plane, whereas when a+c dislocations bend to the basal plane, they were not seen to come back to a prismatic one.
Growth Kinetics of GaN Thin Films Grown by OMVPE Using Single Source Precursors
Authors: Fischer R. A. , Wohlfart A. , Devi A. , Rogge W. 
Published: September 2012

AbstractWe report the growth kinetics of GaN thin films using the single source precursor bisazido dimethylaminopropyl gallium (BAZIGA) in a cold wall reactor. Transparent, smooth, epitaxial (FWHM of the αGaN 0002 rocking curve = 129.6 arcsec) and stoichiometric GaN films were grown on c-plane Al2O3 substrates in the temperature range of 870 – 1320K and high growth rates were obtained (up to 4000 nm/hr). Film growth was studied as a function of substrate temperature as well as reactor pressure. Although high quality films were obtained without using any additional source of nitrogen such as ammonia, we have investigated the effect of ammonia on the growth and properties of the resulting films. The films obtained were characterized by XRD, RBS, XPS, AES, AFM, SEM and the room temperature PL spectroscopy of GaN films grown exhibited the correct near band edge luminescence at 3.45 eV.
Structure and Morphology Characters of GaN Grown by ECR-MBE Using Hydrogen-Nitrogen Mixed Gas Plasma
Authors: Araki Tsutomu , Chiba Yasuo , Nanishi Yasushi 
Published: September 2012

AbstractGaN growth by electron-cyclotron-resonance plasma-excited molecular beam epitaxy using hydrogen-nitrogen mixed gas plasma were carried out on GaN templates with a different polar-surface. Structure and surface morphology of the GaN layers were characterized using transmission electron microscopy. The GaN layer grown with hydrogen on N-polar template showed a relatively flat morphology including hillocks. Columnar domain existed in the center of the hillock, which might be attributed to the existence of tiny inversion domain with Ga-polarity. On the other hand, columnarstructure was formed in the GaN layer grown with hydrogen on Ga-polar template.
Formation and Stability of the Prismatic Stacking Faultin Wurtzite (Al,Ga,In) Nitrides
Authors: Ruterana P. , Béré A. , Nouet G. 
Published: September 2012

AbstractThe formation of the {1210} stacking fault, which has two atomic configurations in wurtzite (Ga,Al,In)N, has been investigated by high resolution electron microscopy and energetic calculations. It originates from steps at the SiC surface and it can form on a flat (0001) sapphire surface. A modified Stillinger-Weber potential was used in order to investigate the relative stability of the two atomic configurations. They have comparable energy in AlN, whereas the 1/2<10 11>{1 210} configuration is more stable in GaN and InN. In GaN layers, only the 1/2<10 11>{1 210} configuration was observed. The 1/6<20 2 3> configuration was found in small areas inside the AlN buffer layer where it folded rapidly to the basal plane, and when back into the prismatic plane, it took the 1/2<10 11>{1 210} atomic configuration.
Surface Activity of Magnesium During GaN Molecular Beam Epitaxial Growth
Authors: Ramachandran V. , Feenstra R. M. , Northrup J. E. , Greve D. W. 
Published: September 2012

AbstractExposure of wurtzite GaN films grown on Si-polar 6H-SiC(0001) to magnesium during molecular beam epitaxy (MBE) has been studied. In the nitrogen rich regime of MBE growth, GaN films are known to grow with rough morphology. We observe on GaN(0001) that small doses of Mg act as a surfactant, smoothing out this roughness. An interpretation of this surfactant behavior is given in terms of electron counting arguments for the surface reconstructions. Previously, we have reported that larger doses of Mg lead to inversion of the Ga-polar GaN film to produce N-polar GaN. Several Mg-related reconstructions of the resulting GaN(000 ) surface are reported.
Effect of the Doping and the Al Content on the Microstructure and Morphology of Thin AlxGa1-xN Layers Grown by MOCVD.
Authors: Mazur J.H. , Benamara M. , Liliental-Weber Z. , Swider W. , Washburn J. , Eiting C.J. , Dupuis R. D. 
Published: September 2012

AbstractAlxGa1−xN {x=30% (doped and undoped), 45% (doped)} thin films were grown by MOCVD on ∼2 µm thick GaN layer using Al2O3 substrate. These films were designed to be the active parts of HFETs with nsí product of about 1016(Vs)−1. The layers were then studied by means of transmission electron microscopy (TEM) techniques. In this paper, it is shown that the AlxGa1−xN layer thickness was non-uniform due to the presence of Vshaped defects within the AlxGa1−xN films. The nucleation of these V-shaped defects has taken place about 20 nm above the AlxGa1−xN/aN interface. Many of these Vshaped defects were associated with the presence of the threading dislocations propagating from the GaN/Al2O3 interface. We show that the density of these V-shaped defects increases with the doping level and also with the Al mole fraction in the films. The formation mechanism of the V-shaped defects seems to be related to the concentration of dopants or other impurities at the ledges of the growing film. This suggestion is supported by high resolution TEM analysis. The growth front between the V-shaped defects in the lower Al concentration thin films was planar as compared with F99W3.77 the three-dimensional growth in the doped, higher Al concentration film. This interpretation of the origin of the V-shaped defects is consistent with the observed lowering of the Schottky barrier height in n-doped AlGaN/Ni Schottky diodes.
Electrical Properties of Oxygen Doped GaN Grown by Metalorganic Vapor Phase Epitaxy
Authors: Korotkov R.Y. , Wessels B.W. 
Published: September 2012

AbstractDeliberate oxygen doping of GaN grown by MOVPE has been studied. The electron concentration increased as the square root of the oxygen partial pressure. Oxygen is a shallow donor with a thermal ionization energy of 27 ±2 meV. A compensation ratio of Θ = 0.3-0.4 was determined from Hall effect measurements. The formation energy of ON of EF = 1.3 eV, determined from the experimental data, is lower than the theoretically predicted value.
Activation of Beryllium-Implanted GaN by Two-Step Annealing
Authors: Sun Yuejun , Tan Leng Seow , Chua Soo Jin , Prakash Savarimuthu 
Published: September 2012

AbstractFor the first time, p-type doping through beryllium implantation in gallium nitride was achieved by using a new annealing process, in which the sample was first annealed in forming gas (12% H2 and 88% N2), followed by annealing in pure nitrogen. Variable temperature Hall measurements showed that sheet hole concentrations of the annealed samples were about 1×1013 cm−2 with low hole mobilities. An ionization energy of 127 meV was estimated with a corresponding activation efficiency of ∼ 100%. SIMS results revealed a relationship between the enhanced diffusion of Be and activation of the acceptors.
GaN 20-mm Diameter Ingots Grown from Melt-Solution by Seeded Technique
Authors: Sukhoveyev V.A. , Ivantsov V.A. , Nikitina I.P. , Babanin A.I. , Polyakov A.Y. , Govorkov A.V. , Smirnov N.B. , Mil'vidskii M.G. , Dmitriev V.A. 
Published: September 2012

AbstractIn this paper, we describe the seeded growth of ∼20 mm diameter 15 mm long GaN ingots from the melt-solution. This is the first successful attempt to conduct growth of GaN boule-crystals. GaN ingots were grown from Ga-based melt in the temperature range of 800-1000°C at less than 2 atm ambient pressure. Growth was performed at ∼2 mm/hr growth rate. X-ray diffraction revealed polycrystalline structure of the ingots. Homoepitaxial GaN layers were deposited by HVPE technique on the substrates, which were fabricated from the grown GaN ingots.
Preparation and Characterization of Single-crystal Aluminum Nitride Substrates
Authors: Schowalter Leo J. , Rojo J. Carlos , Yakolev Nikolai , Shusterman Yuriy , Dovidenko Katherine , Wang Rungjun , Bhat Ishwara , Slack Glen A. 
Published: September 2012

AbstractLarge (up to 10mm diameter) aluminum nitride (AlN) boules have been grown by the sublimation-recondensation method to study the preparation of high-quality single crystal substrates. The growth mechanism of the boules has been studied using AFM. It has been determined that large single crystal grains in those boules grow with a density of screw dislocations below 5×104 cm−3 while edge dislocations are at lower density (none were observed). High-quality AlN single crystal substrates for epitaxial growth have been prepared and characterized using Chemical Mechanical Polishing (CMP) and AFM imaging, respectively. Also, the differential etching effect of KOH solutions on the N and Al-terminated faces of AlN on vicinal c-faces has been investigated. In order to identify the N or Al-terminated face, convergent beam electron diffraction has been used.
Sol-Gel Non-hydrolytic Synthesis of a Nanocomposite Electrolyte for Application in Lithium-ion Devices
Authors: Souza Flávio L. , Bueno Paulo R. , Faria Ronaldo C. , Longo Elson , Leite Edson R. 
Published: September 2012

AbstractA new nanocomposite electrolyte was synthesized using a simple non-hydrolytic sol-gel route without specific treatment of the reagents. The nanocomposite ion conductor was prepared with citric acid, tetraethyl orthosilicate and ethylene glycol, forming polyester chains. The time-consuming drying step that is a necessary part of most chemical syntheses was not required in the preparation of the present nanocomposite electrolyte of the polyelectrolyte class, because only Li+ is mobile in the polymeric chain. The effects of the concentration of Li, SiO 2 and SnO2nanoparticles were investigated in terms of Li+ ionic conductivity. Conductivity measurements as a function of the metal oxide nanocrystal content in the nanocomposite revealed a significant increase in conductivity at approximately 5 and 10 wt % of nanoparticles. The new nanocomposite conductor proved to be fully amorphous at room temperature, with a vitreous transition temperature of approximately 228K (−45°C). The material is solid and transparent, displaying an ionic conductivity of 10−4to 10−5 (O.cm)−1at room temperature presenting excellent reproducibility of all these characteristics. Cyclic voltammetry measurements indicate that the hybrid electrolyte possesses outstanding electrochemical stability.
Preparation, Characterization and Electrochemical Property of ZnCl2-doped Carbon Nanometer Material as the Anode of Lithium-ion Battery
Authors: Zhou D.F. , Zhao Y.L. , Chen Y.G. , Zhang X.Y. , Wang R.S. 
Published: September 2012

AbstractPhenolic resin-based nanoscopic carbonaceous materials have been prepared by doping different proportions of ZnCl2 into phenolic resin (PR) precursor at various heat-treatment temperatures and characterized by means of Brunner-Emmett-Teller method (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy analyses. The results show that as the ratio of PR to ZnCl2 is 1:3, the average size of grains and apertures are about from 40 to 60 nm and 3.86 nm, respectively, reaching nanometer level. When this material is used as electrode material of lithium ion battery, the reversible capacity the battery could be kept at 370 mA•h•g−1 after 10 charge/discharge cycles.
The Role of Lung Metastasis Resection in Improving Outcome of Colorectal Cancer Patients: Results From a Large Retrospective Study
Authors: Tampellini Marco , Ottone Azzurra , Bellini Elisa , Alabiso Irene , Baratelli Chiara , Bitossi Raffaella , Brizzi Maria P. , Ferrero Anna , Sperti Elisa , Leone Francesco , Miraglia Stefania , Forti Laura , Bertona Erica , Ardissone Francesco , Berruti Alfredo , Alabiso Oscar , Aglietta Massimo , Scagliotti Giorgio V. 
Published: September 2012

Abstract

Background.
The role of surgery for lung metastases (LM) secondary to colorectal cancer (CRC) remains controversial. The bulk of evidence is derived from single surgical series, hampering any definitive conclusions. The aim of this study was to compare the outcomes of CRC patients with LM submitted to surgery with those who were not.

Patients and Methods.
Data from 409 patients with LM as the first evidence of advanced disease were extracted from a database of 1,411 patients. Patients were divided into three groups: G1, comprised of 155 patients with pulmonary and extrapulmonary metastases; G2, comprised of 104 patients with LM only and no surgery; G3, comprised of 50 patients with LM only and submitted to surgery.

Results.
No difference in response rates emerged between G1 and G2. Median progression-free survival (PFS) times were: 10.3 months, 10.5 months, and 26.2 months for G1, G2, and G3, respectively. No difference in PFS times was observed between G1 and G2, whereas there was a statistically significant difference between G2 and G3. Median overall survival times were 24.2 months, 31.5 months, and 72.4 months, respectively. Survival times were longer in resected patients: 17 survived &gt;5 years and three survived &gt;10 years. In patients with LM only and no surgery, four survived for 5 years and none survived &gt;10 years.

Conclusions.
Even though patients with resectable LM are more likely to be those with a better outcome, our study provides evidence suggesting an active role of surgery in improving survival outcomes in this patient subset.
Chemotherapy-Induced Ovarian Failure as a Prototype for Acute Vascular Toxicity
Authors: Ben-Aharon Irit , Meizner Israel , Granot Tal , Uri Shiri , Hasky Noa , Rizel Shulamith , Yerushalmi Rinat , Sulkes Aaron , Stemmer Salomon M. 
Published: September 2012

Abstract

Background.
Chemotherapy-related amenorrhea is a frequent side effect observed in young breast cancer patients. Studies in mice revealed that chemotherapy-induced gonadal toxicity may result from vascular damage. We prospectively evaluated ovarian blood flow and function in young breast cancer patients following chemotherapy.

Methods.
Young female patients with localized breast cancer undergoing adjuvant or neoadjuvant anthracycline- or taxane-based chemotherapy were evaluated using transvaginal ultrasound prior to initiation of and immediately after cessation of chemotherapy. Doppler-flow velocity indices of the ovarian vasculature—resistance index (RI), pulsatility index (PI)—and size measurements were visualized. Hormonal profiles, anti-Müllerian hormone (AMH) levels, and menopausal symptoms were assessed at the same time points.

Results.
Twenty breast cancer patients were enrolled in the study. The median age was 34 ± 5.24 years. Ovarian blood flow was significantly reduced shortly following chemotherapy: RI decreased by 52.5% and PI decreased by 24.2%. The mean ovarian size declined by 19.08%. Patients who were treated with sequential chemotherapy experienced further reductions in ovarian blood flow and ovarian size after the second sequence. AMH levels dropped dramatically in all patients following treatment. Hormonal profiles after treatment depicted a postmenopausal profile for most patients, accompanied by related symptoms.

Conclusions.
Our results may imply a mechanism of chemotherapy-induced ovarian toxicity manifested by decreased ovarian blood flow accompanied by a reduction in ovarian size and diminished post-treatment AMH levels. Based upon our former preclinical studies, we assume that this may derive from an acute insult to the ovarian vasculature and may represent an initial event triggering a generalized phenomenon of end-organ toxicity.
Familial Factors in the Association between Preeclampsia and Later ESRD
Authors: Vikse Bjørn Egil , Irgens Lorentz M. , Karumanchi S. Ananth , Thadhani Ravi , Reisæter Anna Varberg , Skjærven Rolv 
Published: September 2012

SummaryBackground and objectivesWomen with preeclampsia have increased risk of developing ESRD. This study assessed whether this can be explained by preeclampsia itself or by familial aggregation of common risk factors.Design, setting, participants, & measurementsSince 1967, the Medical Birth Registry of Norway has registered data on all births in the country. By linkage with the Norwegian Population Registry, different, but overlapping, cohorts were defined: the first and second cohorts included women and a sibling (first cohort) or child (second cohort) with a registered first birth between 1967 and 2008. Similar cohorts were defined for men. The Norwegian Renal Registry provided data on ESRD from 1980 to June 2009.ResultsCohort 1 was used for the main analyses and included 570,675 women, 291 of whom developed ESRD after a median 18.2 years. Compared with women without preeclampsia and no siblings with preeclampsia, women without preeclampsia but a sibling with preeclampsia had a relative risk (RR) of ESRD of 0.96 (95% confidence interval, 0.59–1.6), women with preeclampsia but no siblings with preeclampsia had a RR of 6.0 (4.4–8.1), and women with preeclampsia and a sibling with preeclampsia had a RR of 2.8 (0.88–8.6). Further analyses of women showed no increased risk of ESRD if a child had preeclampsia in first pregnancy.ConclusionsFamilial aggregation of risk factors does not seem to explain increased ESRD risk after preeclampsia. These findings support the hypothesis that preeclampsiaper semay lead to kidney damage.
Peritoneal Dialysis–Associated Peritonitis with Simultaneous Exit-Site Infection
Authors: Mehrotra Rajnish , Singh Harmanjit 
Published: September 2012

Summary
With the implementation of best demonstrated clinical practices, peritonitis has become an infrequent complication of peritoneal dialysis in many centers around the world. Yet the gains in reduction in risk of peritonitis are not uniform. Most episodes of peritonitis do not require hospitalization and it is possible to achieve cure rates of 70%–80%. Some circumstances, however, necessitate the removal of the peritoneal dialysis catheter. These include patients with inadequate response to antimicrobial therapy, those with fungal peritonitis, or those with Staphylococcus aureus or Pseudomonas peritonitis with coexisting exit-site infection with the same organism. If the peritoneal dialysis catheter is removed in the presence of active intraperitoneal infection, replacement of the peritoneal dialysis catheter should be deferred by 2–4 weeks. However, simultaneous removal and replacement is possible in selected circumstances such as in patients with S. aureus or Pseudomonas peritonitis who also have exit-site infection with the same organism, after the intraperitoneal infection has responded to antibiotic therapy.