Integration, gap formation, and sharpening of III-V heterostructure nanowires by selective etching

Epitaxial growth of heterostructure nanowires allows for the definition of narrow sections with specific semiconductor composition. The authors demonstrate how postgrowth engineering of III-V heterostructure nanowires using selective etching can form gaps, sharpening of tips, and thin sections simultaneously on multiple nanowires. They investigate the potential of combining nanostencil deposition of catalyst, epitaxial III-V heterostructure nanowire growth, and selective etching, as a road toward wafer scale integration and engineering of nanowires with existing silicon technology. Nanostencil lithography is used for deposition of catalyst particles on trench sidewalls and the lateral growth of III-V nanowires is achieved from such catalysts. The selectivity of a bromine-based etch on gallium arsenide segments in gallium phosphide nanowires is examined, using a hydrochloride etch to remove the III-V native oxides. Depending on the etching conditions, a variety of gap topologies and tiplike structures are observed, offering postgrowth engineering of material composition and morphology

Compensation and Rewards for Environmental Services in the Developing World: Framing Pan-Tropical Analysis and Comparison

This is the first of a series of papers that review the state of knowledge and practice regarding compensation and rewards for environmental services in the developing world. The paper begins with an assessment of the historical development of compensation and reward mechanisms within a broader context of changing approaches to nature conservation and environmental policy. The assessment shows that greater interest in compensation and reward mechanisms has emerged within a policy context of changing approaches to nature conservation and flexible multi-stakeholder approaches to environmental management. In the developing world, an even greater variety of perspectives has emerged on the opportunities and threats for using compensation and rewards for environmental services. Within that background, the paper clarifies key concepts - including the distinction between compensation and reward - and presents a conceptual framework for typifying and characterizing different types of mechanisms that link ecosystem stewards, ecosystem service beneficiaries, and intermediaries

In Situ TEM Creation and Electrical Characterization of Nanowire Devices

We demonstrate the observation and measurement of simple nanoscale devices over their complete lifecycle from creation to failure within a transmission electron microscope. Devices were formed by growing Si nanowires, using the vapor-liquid-solid method, to form bridges between Si cantilevers. We characterize the formation of the the nature of the connection depends on the flow of heat and V contact between the nanowire and the cantilever, showing that electrical current during and after the moment of contact. We measure the electrical properties and high current failure characteristics of the resulting bridge devices in situ and relate these to the structure. We also describe processes to modify the contact and the nanowire surface after device formation. The technique we describe allows the direct analysis of the processes taking place during device formation and use, correlating specific nanoscale structural and electrical parameters on an individual device basis