Plasticity and size effects in germanium: From cryogenic to elevated temperatures
October 1-6, 2017
Germanium is extensively used as a substrate in functional components of devices and microelectromechanical systems (MEMS) because of its tunable band structure and carrier mobility via. strain engineering . The mechanical properties of Ge with a diamond-cubic structure at such small scales, i.e. in range of micro/nano-meter, are expected to be extraordinary since the improved strength and ductility of brittle crystals with minimized geometries . Recent advances in nano-mechanical testing systems enable the investigation of the size- and temperature-dependent deformation behaviors and relevant parameters .
In the present study, micro-compression of FIB-machined micropillars is conducted to obtain a thorough understanding of the plasticity and size effects of Ge from cryogenic to elevated temperatures, i.e. in the range of -100°C to 600°C, shown in Figure 1(a). Dislocation motion in Ge is quantitatively evaluated as a function of sample size and crystalline orientation at the low temperature regime. Furthermore, the brittle-to-ductile transition is investigated to study the transition of deformation mechanisms, i.e. full to partial dislocation motion on the glide set, at the elevated temperatures regime . Deformed regions in micropillars are subsequently characterized using HRTEM to track dislocations and microtwins. An unambiguous interpretation of dislocation processes in the diamond-cubic structure will be presented.
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Ming Chen, Jeffrey M. Wheeler, and Ralph Spolenak, "Plasticity and size effects in germanium: From cryogenic to elevated temperatures" in "Nanomechanical Testing in Materials Research and Development VI", Karsten Durst, Technical University of Darmstadt, Germany Eds, ECI Symposium Series, (2017). http://dc.engconfintl.org/nanomechtest_vi/20