Bradby, J. E.Williams, J. S.Wong-Leung, JenniferSwain, M. V.Munroe, P.2015-10-122015-10-120003-6951http://hdl.handle.net/1885/15876The mechanical deformation by spherical indentation of both crystalline InP and GaAs was characterized using cross-sectional transmission electron microscopy (XTEM) and atomic force microscopy. All load–unload curves show a discontinuity (or “pop in”) during loading. Slip bands oriented along {111} planes are visible in XTEM micrographs from residual indentations in both materials and no evidence of any phase transformations was found. Higher load indentations (35 mN for InP and 50 mN for GaAs) also revealed subsurface cracking. In contrast no cracking was found beneath a 25 mN InP indent although the hardness and modulus data are almost identical to those of the cracked sample. The subsurface cracks are thought to be nucleated by high stress concentrations caused by dislocation pileup.http://www.sherpa.ac.uk/romeo/issn/0003-6951..."Publishers version/PDF may be used on author's personal website, institutional website or institutional repository" from SHERPA/RoMEO site (as at 12/10/15). Copyright 2001 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics. The following article appeared in Applied Physics Letters and may be found at https://doi.org/10.1063/1.13722072001-05-2110.1063/1.13722072015-12-10