Multi-technique characterisation of MOVPE-grown GaAs on Si

The heterogeneous integration of III-V materials on a Si CMOS platform offers tremendous prospects for future high speed and low power logic applications. That said this integration generates immense scientific and technological challenges. In this work multi-technique characterisation is used to investigate properties of GaAs layers grown by Metal-Organic Vapour Phase Epitaxy (MOVPE) on Si substrates - (100) with 4⁰ offset towards - under various growth conditions. This being a crucial first step towards the production of III-V template layers with a relatively lower density of defects for selective epitaxial overgrowth of device quality material. The optical and structural properties of heteroepitaxial GaAs are first investigated by micro-Raman spectroscopy and photoluminescence and reflectance measurements. High-resolution X-ray diffraction (HR-XRD) is used to investigate structural properties. Advanced XRD techniques, including double-axis diffraction and X-ray crystallographic mapping are used to evaluate degrees of relaxation and distribution of the grain orientations in the epilayers, respectively. Results obtained from the different methodologies are compared in an attempt to understand growth kinetics of the materials system. The GaAs overlayer grown with annealing at 735⁰C following As predeposition at 500⁰C shows the best crystallinity. Close inspection confirms the growth of epitaxial GaAs preferentially oriented along (100) embedded in a highly-textured polycrystalline structure

Non-destructive laboratory-based X-ray diffraction mapping of warpage in Si die embedded in IC packages

Reliability issues as a consequence of thermal/mechanical stresses created during packaging processes have been the main obstacle towards the realisation of high volume 3D Integrated Circuit (IC) integration technology for future microelectronics. However, there is no compelling laboratory-based metrology that can non-destructively measure or image stress/strain or warpage inside packaged chips, System-on-Chip (SoC) or System-in-Package (SiP), which is identified as a requirement by the International Technology Roadmap for Semiconductors (ITRS). In the work presented here, a triple-axis Jordan Valley Bede D1 X-ray diffractometer is used to develop a novel lab-based technique called X-ray diffraction 3-dimensional surface modeling (XRD/3DSM) for non-destructive analysis of manufacturing process-induced stress/warpage inside completely encapsulated packaged chips. The technique is demonstrated at room temperature and at elevated temperatures up to 115C by in situ XRD annealing experiments. The feasibility of this technique is confirmed through the charactersation of die stress inside encapsulated commercially available ultra-thin Quad Flat Non-lead (QFN) packages, as well as die stress in embedded QFN packages at various stages of the chip manufacturing proces

The Effect of Batched Production on Demand Amplification

Demand amplification is the tendency of small fluctuations in demand at the retailer end of the supply chain to be amplified as they are communicated down the chain. A brief review of the literature on this phenomenon is presented, concentrating particularly on the causes propounded. A continuous-time differential equation model of a production-inventory system is then proposed. The application of a novel optimal control algorithm is applied in order to simulate the rational behaviour of inventory managers. This algorithm allows us to mimic the discontinuous cost structures implied by the advantages of batched production. By simulating the response of the system to small changes in demand, the relationship between batch size and the magnitude of demand amplification is investigated

Magnetic and quantum entanglement properties of the distorted diamond chain model for azurite

We present the results of magnetic properties and entanglement of the distorted diamond chain model for azurite using pure quantum exchange interactions. The magnetic properties and concurrence as a measure of pairwise thermal entanglement have been studied by means of variational mean-field like treatment based on Gibbs-Bogoliubov inequality. Such a system can be considered as an approximation of the natural material azurite, Cu3(CO3)2(OH)2. For values of exchange parameters, which are taken from experimental results, we study the thermodynamic properties, such as azurite specific heat and magnetic susceptibility. We also have studied the thermal entanglement properties and magnetization plateau of the distorted diamond chain model for azurite

A threshold phenomenon for embeddings of H0mH^m_0 into Orlicz spaces

We consider a sequence of positive smooth critical points of the Adams-Moser-Trudinger embedding of $H^m_0$ into Orlicz spaces. We study its concentration-compactness behavior and show that if the sequence is not precompact, then the liminf of the $H^m_0$-norms of the functions is greater than or equal to a positive geometric constant.Comment: 14 Page

Sociocultural considerations in aging men's health: implications and recommendations for the clinician

http://dx.doi.org/10.1016/j.jomh.2009.07.00

The Strong Energy Condition and the S-Brane Singularity Problem

Recently it has been argued that, because tachyonic matter satisfies the Strong Energy Condition [SEC], there is little hope of avoiding the singularities which plague S-Brane spacetimes. Meanwhile, however, Townsend and Wohlfarth have suggested an ingenious way of circumventing the SEC in such situations, and other suggestions for actually violating it in the S-Brane context have recently been proposed. Of course, the natural context for discussions of [effective or actual] violations of the SEC is the theory of asymptotically deSitter spacetimes, which tend to be less singular than ordinary FRW spacetimes. However, while violating or circumventing the SEC is necessary if singularities are to be avoided, it is not at all clear that it is sufficient. That is, we can ask: would an asymptotically deSitter S-brane spacetime be non-singular? We show that this is difficult to achieve; this result is in the spirit of the recently proved "S-brane singularity theorem". Essentially our results suggest that circumventing or violating the SEC may not suffice to solve the S-Brane singularity problem, though we do propose two ways of avoiding this conclusion.Comment: 13 pages, minor corrections and improvements, references adde

Study of the Process e+e−→KL0KS0e^+e^- \to K^0_L K^0_S in the C.M.Energy Range 1.05-1.38 GeV with CMD-2

The process $e^+e^- \to K^0_L K^0_S$ has been studied with the CMD-2 detector using about 950 events detected in the center-of-mass energy range from 1.05 to 1.38 GeV. The cross section exceeds the expectation based on the contributions of the rho(770), omega(782) and phi(1020) mesons only.Comment: 12 pages, 3 figures, uses elsart.cls, submitted to Physics Letters

High-statistics measurement of the pion form factor in the rho-meson energy range with the CMD-2 detector

We present a measurement of the pion form factor based on e+e- annihilation data from the CMD-2 detector in the energy range 0.6<sqrt(s)<1.0 GeV with a systematic uncertainty of 0.8%. A data sample is five times larger than that used in our previous measurement.Comment: 18 pages, 10 figures. Added comparison with KLOE measurement, minor updates. Accepted by PL

Dark Matter, Light Stops and Electroweak Baryogenesis

We examine the neutralino relic density in the presence of a light top squark, such as the one required for the realization of the electroweak baryogenesis mechanism, within the minimal supersymmetric standard model. We show that there are three clearly distinguishable regions of parameter space, where the relic density is consistent with WMAP and other cosmological data. These regions are characterized by annihilation cross sections mediated by either light Higgs bosons, Z bosons, or by the co-annihilation with the lightest stop. Tevatron collider experiments can test the presence of the light stop in most of the parameter space. In the co-annihilation region, however, the mass difference between the light stop and the lightest neutralino varies between 15 and 30 GeV, presenting an interesting challenge for stop searches at hadron colliders. We present the prospects for direct detection of dark matter, which provides a complementary way of testing this scenario. We also derive the required structure of the high energy soft supersymmetry breaking mass parameters where the neutralino is a dark matter candidate and the stop spectrum is consistent with electroweak baryogenesis and the present bounds on the lightest Higgs mass.Comment: 24 pages, 8 figures; version published in Phys.Rev.