High temperature processing of poly-SiC substrates from the vapor phase for wafer-bonding

The transfer by wafer-bonding of single-crystalline SiC thin films to a polycrystalline SiC substrate to obtain a “quasi-wafer” requires high quality polycrystalline substrates with controlled bulk properties (thermal conductivity, electrical resistivity) as well as with very low surface roughness (RMS < 5 nm) and bowing (< 10 μm). Currently, available polycrystalline SiC wafers are processed by sintering or by Chemical Vapor Deposition (CVD). Sintered ceramic wafers are very heterogeneous (mixture of 3C, 6H, 4H and silicon), while CVD ones are of better quality (homogeneous and textured 3C). The aim of this paper is to investigate the fabrication and the properties (bulk and surface) of SiC substrates with large (0.1 to a few mm) grains. To meet these requirements, two high temperature processes (around 2000 °C) for single crystal growth were used: Physical Vapor Transport (PVT) and the recently developed CVD Feed Physical Vapor Transport (CF-PVT). Structural investigations performed on large grain wafers sliced and polished from the grown ingots showed an important influence of the initial seed on the grain size, polytype and crystallographic texture. Chemical and Mechanical Polishing (CMP) of such structures was studied and optimized to obtain low surface roughness. The intra-grain roughness is very low (RMS < 0.5 nm) but a few nanometer of height steps were observed between grains. The relations between bulk properties, surface functionalization and process conditions are discussed. This first seeding step with commercial substrates is necessary for the creation of original substrates which can be used for the fabrication of new substrates.     

Optimized growth conditions and properties of N-type and insulating GaN

The nucleation and growth of gallium nitride on sapphire have been studied. By an optimization of the different growth parameters, smooth, reproducible, transparent and large area layers of gallium nitride were obtained. Multi-layer structures of zinc doped GaN on N-type GaN have been grown. Devices made on these structures exhibit electroluminescence from orange to dark blue. This luminescence is obtained for voltage as low as 2.4 volts for orange, 2.6 volts for yellow, 2.8 volts for green and 3.2 volts for blue. The external power efficiency is about 10^?3 for dark green and blue light emitting devices.     

Etude de nouveaux pnictures ternaires de metaux de transition isostructuraux des phases G,Ni16Mn6P7, Ni16Mn6As7

The structural properties of the new ternary phosphide and arsenide of nickel and manganese Ni₁₆Mn₆P₇ and Ni₁₆Mn₆As₇ have been investigated. This crystal structure as determined by powder X-ray diffraction was found to be the well known structure of the G phases of germanides and silicides.     

Jewish culture and the WISC and WAIS test patterns.

Analyzed data from previous studies on the WISC performance of Jewish children, and conducted a WISC study with 185 5-15 yr old Israeli children. Results reveal a highly consistent and stable WISC pattern, characterized by relatively low scores on Picture Completion, Picture Arrangement, Block Design, and Object Assembly. It is suggested that some of these findings might best be understood by reference to relative weakness of Jewish Ss on tasks related to psychological differentiation. The results point to (a) the need to temper clinical interpretation of WISC score profiles by reference to the culture group under study and (b) the danger of oversimplified adjustment of WISC norms when dealing with different cultural or subcultural groups. Evidence from other previous studies suggests that this pattern may be equally true with regard to adult performance on the WAIS. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Structure antiferroma gnetique de Fe1. 125Te accompagnee d'une deformation monoclinique

The antiferromagnetic structure of the tetragonal phase Fe_{1. 125}Te has been determined. Below the magnetic-order temperature x-ray and neutron diffraction show a monoclinic deformation.     

Angular dependence of the magnetoresistivity of Pd2Si

We present the magnetoresistivity at high magnetic field measured on single crystals of Pd₂Si of very good quality. The magnetoresistance depends on the orientation of field and current directions relative to the crystallographic axis. It shows that this suicide behaves like a compensated metal (i.e. equal numbers of electrons and holes) with open orbits along the main crystallographic directions.     

Imaging of delta- and mu-opioid receptors in temporal lobe epilepsy by positron emission tomography

The authors report the postoperative magnetic resonance (MR) imaging findings in 36 patients with advanced Parkinson's disease who underwent unilateral microelectrode-guided posteroventral pallidotomy. The lesions were placed within 1 mm of the ventral border of the globus pallidus internus (GPi) to include pallidothalamic outflow pathways. Sequential MR studies were obtained within 1 to 3 days postoperatively and at 6-month follow-up examination. Thirty-four (94%) of the 36 patients enjoyed sustained moderate or marked improvement of their parkinsonian symptoms 6 months postoperatively. Transient side effects occurred in five patients (14%), but there were no persistent complications. The pallidal radiofrequency lesions were prolate spheroid shaped and were composed of three concentric zones in the early postoperative studies. The mean volume of the middle zone, corresponding to the area of hemorrhagic coagulation necrosis, was 44.4 +/- 17.6 mm3; the mean lesion volume as defined by the outer zone, corresponding to perilesional edema, was 262.2 +/- 111.6 mm3. Additional edema spreading to the internal capsule was noted in 32 of 34 cases and to the optic tract in 11 of 34 cases. In two patients small ischemic infarctions involving the corona radiata were found, and in one a venous infarction was detected. Ischemic infarction resulted in mild transient Broca's aphasia in one patient, but there was no detectable neurological deficit in the other two. The mean volume of late-phase (6 months) lesions was 22 +/- 28.8 mm3. In three patients no lesion was identified despite sustained clinical improvement. The lesion was located in the posteroventral GPi in all cases except in one patient in whom it was confined to the GP externus (GPe). This 49-year-old woman did not experience sustained benefit. The authors found no consistent correlations between lesion size and location and clinical outcome as measured by a global outcome score, the Unified Parkinson's Disease Rating Scale motor, activities of daily living, and bradykinesia "off" scores or rating of dyskinesias. Lesioning of pallidal and subpallidal pathways may contribute to the sustained clinical benefit in this series. Magnetic resonance imaging analysis showed that intraoperative microelectrode recording facilitated accurate placement of the lesion in this critical area.     

Hantavirus pulmonary syndrome in the United States: a pathological description of a disease caused by a new agent

An outbreak of an acute respiratory disease in the southwestern United States has led to the recognition of a new hantaviral illness. This report describes a unique spectrum of antemortem and postmortem pathological findings seen in a case series of nine surviving patients and 13 who died. Clinical, laboratory, and autopsy findings were derived from a consecutive series of individuals confirmed to have hantavirus pulmonary syndrome. Laboratory studies included chemical, hematological, and bone marrow analyses as well as flow cytometric and immunohistochemical phenotyping. Autopsy tissues were examined by routine histological stains, immunohistochemical methods, and transmission electron microscopy. The lung is the primary target organ in this illness. Pulmonary abnormalities include pleural effusions, alveolar edema and fibrin, and an interstitial mononuclear cell infiltrate. Large immunoblast type cells are seen in the lungs, blood, bone marrow, lymph nodes, liver, and spleen. A tetrad of hematological findings includes left-shifted neutrophilic leukocytosis, thrombocytopenia, hemoconcentration in severe cases, and circulating immunoblasts. In contrast to previously described nephropathic hantaviral syndromes, hantavirus pulmonary syndrome is characterized by a unique constellation of pulmonary, hematological, and reticuloendothelial pathological findings. The pulmonary findings are distinguishable from fatal adult respiratory distress syndrome. The data suggest a capillary leak syndrome restricted to the pulmonary circulation. Likewise, the hematological picture is unique and may be valuable in the rapid identification of cases for further diagnostic studies.