The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Paul C Mcintyre - One of the best experts on this subject based on the ideXlab platform.
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hexagonal close packed structure of au nanocatalysts solidified after ge nanowire vapor liquid solid growth
Nano Letters, 2010Co-Authors: A F Marshall, Irene A Goldthorpe, Hemant Adhikari, Makoto Koto, Youngchung Wang, Eva Olsson, Paul C McintyreAbstract:We report that approximately 10% of the Au catalysts that crystallize at the tips of Ge nanowires following growth have the close-packed hexagonal crystal structure rather than the equilibrium face-centered-cubic structure. Transmission electron microscopy results using aberration-corrected imaging, and diffraction and compositional analyses, confirm the hexagonal phase in these 40−50 nm particles. Reports of hexagonal close packing in Au, even in nanoparticle form, are rare, and the observations suggest metastable pathways for the crystallization process. These results bring new considerations to the stabilization of the liquid Eutectic alloy at low Temperatures that allows for vapor−liquid−solid growth of high quality, epitaxial Ge nanowires below the Eutectic Temperature.
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metastability of au ge liquid nanocatalysts ge vapor liquid solid nanowire growth far below the bulk Eutectic Temperature
ACS Nano, 2007Co-Authors: Hemant Adhikari, A F Marshall, Irene A Goldthorpe, Christopher E D Chidsey, Paul C McintyreAbstract:The vapor–liquid–solid mechanism of nanowire (NW) growth requires the presence of a liquid at one end of the wire; however, Au-catalyzed Ge nanowire growth by chemical vapor deposition can occur at ∼100 °C below the bulk Au−Ge Eutectic. In this paper, we investigate deep sub-Eutectic stability of liquid Au−Ge catalysts on Ge NWs quantitatively, both theoretically and experimentally. We construct a binary Au−Ge phase diagram that is valid at the nanoscale and show that equilibrium arguments, based on capillarity, are inconsistent with stabilization of Au−Ge liquid at deep sub-Eutectic Temperatures, similar to those used in Ge NW growth. Hot-stage electron microscopy and X-ray diffraction are used to test the predictions of nanoscale phase equilibria. In addition to Ge supersaturation of the Au−Ge liquid droplet, which has recently been invoked as an explanation for deep sub-Eutectic Ge NW growth, we find evidence of a substantial kinetic barrier to Au solidification during cooling below the nanoscale Au−Ge...
Reinoud F. Wolffenbuttel - One of the best experts on this subject based on the ideXlab platform.
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low Temperature intermediate au si wafer bonding Eutectic or silicide bond
Sensors and Actuators A-physical, 1997Co-Authors: Reinoud F. WolffenbuttelAbstract:Abstract The actual mechanism involved in Au-Si wafer bonding is controversial. Usually a titanium or chromium layer is deposited in between the (oxidized) silicon substrate and the gold layer to ensure adhesion. The resulting bond of two such wafers after annealing is generally considered to be Eutectic, however, the bond Temperature required is higher than would be expected from the Au-Si Eutectic Temperature. Moreover, silicide grains are formed at the bonding interface. In this paper it is proposed that the actual bonding is initiated by the dissolution of the oxide layer by silicidation of the titanium adhesion/barrier layer. The subsequent direct Au-Si contact enables the formation of the euteetic phase. The silicidation is required to obtain the Eutectic alloy with 19 at.% Si despite the Ti diffusion barrier. The bonding Temperature required is, therefore, set by the silicidation process rather than by the Eutectic phase. Several experiments have been designed to support this theory. AI-Si Eutectic bonding has been investigated, as it is not complicated by an adhesion metal and experiments demonstrate reliable bonding close to its Eutectic Temperature. Moreover, a Ti/Au/Si/Au stack has been fabricated to be used as a Eutectic solder, giving bonding at a Temperature not affected by silicidation. Keywords Eutectic bonding Gold Silicide bonding Silicon Wafer bonding
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Low-Temperature silicon wafer-to-wafer bonding using gold at Eutectic Temperature
Sensors and Actuators A: Physical, 1994Co-Authors: Reinoud F. Wolffenbuttel, Kensall D. WiseAbstract:Abstract Micromechanical smart sensor and actuator systems of high complexity become commercially viable when realized as a multi-wafer device in which the mechanical functions are distributed over different wafers and one of the wafers is dedicated to contain the readout circuits. The individually-processed wafers can be assembled using wafer-to-wafer bonding and can be combined to one single functional electro-mechanical unit using through-wafer interconnect, provided that the processes involved comply with the constraints imposed by the proper operation of the active electrical and micromechanical subsystems. This implies low-Temperature wafer-to-wafer bonding and through-wafer interconnect. Au/Si Eutectic bonding has been investigated as it can conveniently be combined with bulk-micromachined through-wafer interconnect. The Temperature control in Eutectic bonding has been shown to be critical.
Stefan Sellner - One of the best experts on this subject based on the ideXlab platform.
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self consistent interpretation of the 2d structure of the liquid au 82 si 18 surface bending rigidity and the debye waller effect
Physical Review Letters, 2010Co-Authors: S Mechler, Peter S Pershan, E Yahel, S E Stoltz, Oleg Shpyrko, Binhua Lin, Mati Meron, Stefan SellnerAbstract:The structural and mechanical properties of 2D crystalline surface phases that form at the surface of liquid Eutectic ${\mathrm{Au}}_{82}{\mathrm{Si}}_{18}$ are studied using synchrotron x-ray scattering over a large Temperature range. In the vicinity of the Eutectic Temperature the surface consists of a 2D atomic bilayer crystalline phase that transforms into a 2D monolayer crystalline phase during heating. The latter phase eventually melts into a liquidlike surface on further heating. We demonstrate that the short wavelength capillary wave fluctuations are suppressed due to the bending rigidity of 2D crystalline phases. The corresponding reduction in the Debye-Waller factor allows for measured reflectivity to be explained in terms of an electron density profile that is consistent with the 2D surface crystals.
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self consistent interpretation of the 2d structure of the liquid au82si18 surface bending rigidity and the debye waller effect
Physical Review Letters, 2010Co-Authors: S Mechler, Peter S Pershan, E Yahel, S E Stoltz, Oleg Shpyrko, Binhua Lin, Mati Meron, Stefan SellnerAbstract:The structural and mechanical properties of 2D crystalline surface phases that form at the surface of liquid Eutectic Au{sub 82}Si{sub 18} are studied using synchrotron x-ray scattering over a large Temperature range. In the vicinity of the Eutectic Temperature the surface consists of a 2D atomic bilayer crystalline phase that transforms into a 2D monolayer crystalline phase during heating. The latter phase eventually melts into a liquidlike surface on further heating. We demonstrate that the short wavelength capillary wave fluctuations are suppressed due to the bending rigidity of 2D crystalline phases. The corresponding reduction in the Debye-Waller factor allows for measured reflectivity to be explained in terms of an electron density profile that is consistent with the 2D surface crystals.
Hemant Adhikari - One of the best experts on this subject based on the ideXlab platform.
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hexagonal close packed structure of au nanocatalysts solidified after ge nanowire vapor liquid solid growth
Nano Letters, 2010Co-Authors: A F Marshall, Irene A Goldthorpe, Hemant Adhikari, Makoto Koto, Youngchung Wang, Eva Olsson, Paul C McintyreAbstract:We report that approximately 10% of the Au catalysts that crystallize at the tips of Ge nanowires following growth have the close-packed hexagonal crystal structure rather than the equilibrium face-centered-cubic structure. Transmission electron microscopy results using aberration-corrected imaging, and diffraction and compositional analyses, confirm the hexagonal phase in these 40−50 nm particles. Reports of hexagonal close packing in Au, even in nanoparticle form, are rare, and the observations suggest metastable pathways for the crystallization process. These results bring new considerations to the stabilization of the liquid Eutectic alloy at low Temperatures that allows for vapor−liquid−solid growth of high quality, epitaxial Ge nanowires below the Eutectic Temperature.
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metastability of au ge liquid nanocatalysts ge vapor liquid solid nanowire growth far below the bulk Eutectic Temperature
ACS Nano, 2007Co-Authors: Hemant Adhikari, A F Marshall, Irene A Goldthorpe, Christopher E D Chidsey, Paul C McintyreAbstract:The vapor–liquid–solid mechanism of nanowire (NW) growth requires the presence of a liquid at one end of the wire; however, Au-catalyzed Ge nanowire growth by chemical vapor deposition can occur at ∼100 °C below the bulk Au−Ge Eutectic. In this paper, we investigate deep sub-Eutectic stability of liquid Au−Ge catalysts on Ge NWs quantitatively, both theoretically and experimentally. We construct a binary Au−Ge phase diagram that is valid at the nanoscale and show that equilibrium arguments, based on capillarity, are inconsistent with stabilization of Au−Ge liquid at deep sub-Eutectic Temperatures, similar to those used in Ge NW growth. Hot-stage electron microscopy and X-ray diffraction are used to test the predictions of nanoscale phase equilibria. In addition to Ge supersaturation of the Au−Ge liquid droplet, which has recently been invoked as an explanation for deep sub-Eutectic Ge NW growth, we find evidence of a substantial kinetic barrier to Au solidification during cooling below the nanoscale Au−Ge...
Kensall D. Wise - One of the best experts on this subject based on the ideXlab platform.
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Low-Temperature silicon wafer-to-wafer bonding using gold at Eutectic Temperature
Sensors and Actuators A: Physical, 1994Co-Authors: Reinoud F. Wolffenbuttel, Kensall D. WiseAbstract:Abstract Micromechanical smart sensor and actuator systems of high complexity become commercially viable when realized as a multi-wafer device in which the mechanical functions are distributed over different wafers and one of the wafers is dedicated to contain the readout circuits. The individually-processed wafers can be assembled using wafer-to-wafer bonding and can be combined to one single functional electro-mechanical unit using through-wafer interconnect, provided that the processes involved comply with the constraints imposed by the proper operation of the active electrical and micromechanical subsystems. This implies low-Temperature wafer-to-wafer bonding and through-wafer interconnect. Au/Si Eutectic bonding has been investigated as it can conveniently be combined with bulk-micromachined through-wafer interconnect. The Temperature control in Eutectic bonding has been shown to be critical.
