Mechanical Deformation Induced in Si and GaN Under Berkovich Nanoindentation

Details of Berkovich nanoindentation-induced mechanical deformation mechanisms of single-crystal Si(100) and the metal-organic chemical-vapor deposition (MOCVD) derived GaN thin films have been systematic investigated by means of micro-Raman spectroscopy and cross-sectional transmission electron microscopy (XTEM) techniques. The XTEM samples were prepared by using focused ion beam (FIB) milling to accurately position the cross-section of the nanoindented area. The behaviors of the discontinuities displayed in the loading and unloading segments of the load-displacement curves of Si and GaN thin films performed with a Berkovich diamond indenter tip were explained by the observed microstructure features obtained from XTEM analyses. According to the observations of micro-Raman and XTEM, the nanoindentation-induced mechanical deformation is due primarily to the generation and propagation of dislocations gliding along the pyramidal and basal planes specific to the hexagonal structure of GaN thin films rather than by indentation-induced phase transformations displayed in Si

Public Capital and Economic Growth: A Critical Survey

This article provides an overview of both theoretical and empirical literature on the link between public investment (capital) and economic growth (national income). We first survey the channels through which public capital can conceivably affect growth. We then turn to reviewing the existing empirical literature, and we conclude that although not all studies find a growth-enhancing effect of public capital, there is now more consensus than in the past that public capital furthers economic growth. However, the impact reported by recent studies is not as big as some earlier studies suggested. We conclude with an overview of what is known about the optimality of public capital stocks. Copyright 2007 die Autoren Journal compilation 2007, Verein für Socialpolitik und Blackwell Publishing Ltd.