Influence of PH3 exposure on silicon substrate morphology in the MOVPE growth of III-V on silicon multijunction solar cells

Dual-junction solar cells formed by a GaAsP or GaInP top cell and a silicon bottom cell seem to be attractive candidates to materialize the long sought-for integration of III-V materials on silicon for photovoltaic applications. One of the first issues to be considered in the development of this structure will be the strategy to create the silicon emitter of the bottom subcell. In this study, we explore the possibility of forming the silicon emitter by phosphorus diffusion (i.e. exposing the wafer to PH3 in a MOVPE reactor) and still obtain good surface morphologies to achieve a successful III-V heteroepitaxy as occurs in conventional III-V on germanium solar cell technology. Consequently, we explore the parameter space (PH3 partial pressure, time and temperature) that is needed to create optimized emitter designs and assess the impact of such treatments on surface morphology using atomic force microscopy. Although a strong degradation of surface morphology caused by prolonged exposure of silicon to PH3 is corroborated, it is also shown that subsequent anneals under H-2 can recover silicon surface morphology and minimize its RMS roughness and the presence of pits and spikes

Chemical vapour deposition synthetic diamond: materials, technology and applications

Substantial developments have been achieved in the synthesis of chemical vapour deposition (CVD) diamond in recent years, providing engineers and designers with access to a large range of new diamond materials. CVD diamond has a number of outstanding material properties that can enable exceptional performance in applications as diverse as medical diagnostics, water treatment, radiation detection, high power electronics, consumer audio, magnetometry and novel lasers. Often the material is synthesized in planar form, however non-planar geometries are also possible and enable a number of key applications. This article reviews the material properties and characteristics of single crystal and polycrystalline CVD diamond, and how these can be utilized, focusing particularly on optics, electronics and electrochemistry. It also summarizes how CVD diamond can be tailored for specific applications, based on the ability to synthesize a consistent and engineered high performance product.Comment: 51 pages, 16 figure

Institute of Computer Technology,

Abstract – Robot-aided care for handicapped and elderly people is expected to be a key factor in future building automation. Teams of specialized service robots shall assist autonomously in tasks of everyday life. To fulfill the demands of this application field, robotic design has to face new challenges in behavioral design. In this paper a new approach for a general architecture of behavior for mobile robots and automation systems is presented. Based on the psychoanalytic model of the human mind, emotional evaluation mechanisms shall facilitate a fast estimation of complex and unpredictable situations based on environmental data acquired by the sensors of the robot. Emotional intelligence is used to narrow the focus of attention leading to a reduction of the computational load, and to improve the cooperative behavior among the robots. In order to show the advantages of the emotional arbitration architecture, the model has been tested in simulations based on the characteristics of an existing mobile robot. I

An advanced tabu search approach to the dynamic airlift loading problem

This research effort presents a tabu search algorithm to solve the dynamic airlift loading problem. Given a set of palletized cargo items which require transportation from an aerial port of embarkation to an aerial port of debarkation within a pre-specified time frame, the dynamic airlift loading problem seeks to partition the pallets into aircraft loads, select an efficient and effective subset of aircraft from available aircraft, and assign the pallets to allowable positions on those aircraft. The dynamic airlift loading problem differs from many partitioning and packing problems described in the literature because, in addition to spatial constraints, factors such as allowable cabin load, balance restrictions, and temporal restrictions on cargo and aircraft are included. The algorithm developed in this research, the dynamic airlift loading problem-tabu search, was tested on a variety of problem instances. Since real-world solutions are hand generated by subject matter experts and no previous research effort has solved this specific problem, the algorithmic results are compared to compute lower bounds on the number of aircraft trips required