30,860 research outputs found

    High efficiency solar cell processing

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    At the time of writing, cells made by several groups are approaching 19% efficiency. General aspects of the processing required for such cells are discussed. Most processing used for high efficiency cells is derived from space-cell or concentrator cell technology, and recent advances have been obtained from improved techniques rather than from better understanding of the limiting mechanisms. Theory and modeling are fairly well developed, and adequate to guide further asymptotic increases in performance of near conventional cells. There are several competitive cell designs with promise of higher performance ( 20%) but for these designs further improvements are required. The available cell processing technology to fabricate high efficiency cells is examined

    Recent developments in thin silicon solar cells

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    Fifty micron thick cells 2x4 sq cm area with coplanar back contacts were made with good yield, and with output equivalent to conventional top/bottom contact cells of the same thickness. A wraparound junction (WAJ) design was selected, and used successfully. The low alpha cells delivered were all above 12%, the average efficiency was 13% and the best was 14%. The overall yield was 35 to 40%, comparable to that for conventional 50 micron cells. The process sequence was moderately complex, but showed good reproducibility. The CBC cells performed wall under several important environmental tests. High alpha CBC cells were made, with about 1% increase in conversion efficiency. The most important design criteria were the choice of back surface N+ and P+ areas

    Silicon solar cells for space use: Present performance and trends

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    A technology assessment of present performance levels and current fabrication methods and designs is presented

    Radio Continuum Sources Associated with AB Aur

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    We present high angular resolution, high-sensitivity Very Large Array observations at 3.6 cm of the Herbig Ae star AB Aur. This star is of interest since its circumstellar disk exhibits characteristics that have been attributed to the presence of an undetected low mass companion or giant gas planet. Our image confirms the continuum emission known to exist in association with the star, and detects a faint protuberance that extends about 0.30\rlap.{''}3 to its SE. Previous theoretical considerations and observational results are consistent with the presence of a companion to AB Aur with the separation and position angle derived from our radio data. We also determine the proper motion of AB Aur by comparing our new observations with data taken about 17 years ago and find values consistent with those found by Hipparcos.Comment: 6 pages, 1 figur

    VLA Imaging of the Disk Surrounding the Nearby Young Star TW Hya

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    The TW Hya system is perhaps the closest analog to the early solar nebula. We have used the Very Large Array to image TW Hya at wavelengths of 7mm and 3.6 cm with resolutions 0.1 arcseconds (about 5 AU) and 1.0 arcseconds (about 50 AU), respectively. The 7mm emission is extended and appears dominated by a dusty disk of radius larger than 50 AU surrounding the star. The 3.6 cm emission is unresolved and likely arises from an ionized wind or gyrosynchrotron activity. The dust spectrum and spatially resolved 7mm images of the TW Hya disk are fitted by a simple model with temperature and surface density described by radial power laws, T(r)r0.5T(r)\propto r^{-0.5} and Σ(r)r1\Sigma(r) \propto r^{-1}. These properties are consistent with an irradiated gaseous accretion disk of mass 0.03 M\sim0.03~{\rm M_{\odot}} with an accretion rate 108 Myr1\sim10^{-8}~{\rm M_{\odot}yr^{-1}} and viscosity parameter α=0.01\alpha = 0.01. The estimates of mass and mass accretion rates are uncertain as the gas-to-dust ratio in the TW Hya disk may have evolved from the standard interstellar value.Comment: 13 pages, 3 figures, accepted by ApJ Letter

    Circumbinary Molecular Rings Around Young Stars in Orion

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    We present high angular resolution 1.3 mm continuum, methyl cyanide molecular line, and 7 mm continuum observations made with the Submillimeter Array and the Very Large Array, toward the most highly obscured and southern part of the massive star forming region OMC1S located behind the Orion Nebula. We find two flattened and rotating molecular structures with sizes of a few hundred astronomical units suggestive of circumbinary molecular rings produced by the presence of two stars with very compact circumstellar disks with sizes and separations of about 50 AU, associated with the young stellar objects 139-409 and 134-411. Furthermore, these two circumbinary rotating rings are related to two compact and bright {\it hot molecular cores}. The dynamic mass of the binary systems obtained from our data are \geq 4 M_\odot for 139-409 and \geq 0.5 M_\odot for 134-411. This result supports the idea that intermediate-mass stars will form through {\it circumstellar disks} and jets/outflows, as the low mass stars do. Furthermore, when intermediate-mass stars are in multiple systems they seem to form a circumbinary ring similar to those seen in young, multiple low-mass systems (e.g., GG Tau and UY Aur).Comment: Accepted by Astronomy and Astrophysic

    SMA observations of the proto brown dwarf candidate SSTB213 J041757

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    Context. The previously identified source SSTB213 J041757 is a proto brown dwarf candidate in Taurus, which has two possible components A and B. It was found that component B is probably a class 0/I proto brown dwarf associated with an extended envelope. Aims. Studying molecular outflows from young brown dwarfs provides important insight into brown dwarf formation mechanisms, particularly brown dwarfs at the earliest stages such as class 0, I. We therefore conducted a search for molecular outflows from SSTB213 J041757. Methods. We observed SSTB213 J041757 with the Submillimeter Array to search for CO molecular outflow emission from the source. Results. Our CO maps do not show any outflow emission from the proto brown dwarf candidate. Conclusions. The non-detection implies that the molecular outflows from the source are weak; deeper observations are therefore needed to probe the outflows from the source.Comment: 7 pages, 4 figures, accepted for publication in A&

    Thermal stability of titanium nitride for shallow junction solar cell contacts

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    To demonstrate the thermal stability of titanium nitride as a high-temperature diffusion barrier, the TiN-Ti-Ag metallization scheme has been tested on shallow-junction (~2000 Å) Si solar cells. Electrical measurements on reference samples with the Ti-Ag metallization scheme show serious degradation after a 600 °C, 10-min annealing. With the TiN-Ti-Ag scheme, no degradation of cell performance is observed after the same heat treatment if the TiN layer is >~1700 Å. The glass encapsulation of cells by electrostatic bonding requires such a heat treatment

    Characterization Of Thermal Stresses And Plasticity In Through-Silicon Via Structures For Three-Dimensional Integration

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    Through-silicon via (TSV) is a critical element connecting stacked dies in three-dimensional (3D) integration. The mismatch of thermal expansion coefficients between the Cu via and Si can generate significant stresses in the TSV structure to cause reliability problems. In this study, the thermal stress in the TSV structure was measured by the wafer curvature method and its unique stress characteristics were compared to that of a Cu thin film structure. The thermo-mechanical characteristics of the Cu TSV structure were correlated to microstructure evolution during thermal cycling and the local plasticity in Cu in a triaxial stress state. These findings were confirmed by microstructure analysis of the Cu vias and finite element analysis (FEA) of the stress characteristics. In addition, the local plasticity and deformation in and around individual TSVs were measured by synchrotron x-ray microdiffraction to supplement the wafer curvature measurements. The importance and implication of the local plasticity and residual stress on TSV reliabilities are discussed for TSV extrusion and device keep-out zone (KOZ).Microelectronics Research Cente
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