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RESEARCH PAPER

Understanding mechanical properties and failure mechanism of germanium-silicon alloy at nanoscale Md. Habibur Rahman & Emdadul Haque Chowdhury & Md Mahbubul Islam

Received: 8 May 2020 / Accepted: 6 October 2020 # Springer Nature B.V. 2020

Abstract We use molecular dynamics simulations to investigate the material properties of cubic zinc blende Si0.5Ge0.5 alloy nanowire (NW). We elucidate the effect of nanowire size, crystal orientations, and temperature on the material properties. We found that the reduction in the NW cross-sectional area results in lower ultimate tensile strength (UTS) and Young’s modulus. The [111] and [110] oriented NWs exhibit the highest fracture strength and fracture toughness, respectively. The increased temperature degrades the strength of the material and facilitates failure. The vacancy defects introduced via removal of either Si or Ge atoms exhibit similar behavior, and linear reduction of UTS and Young’s modulus are realized with an increased vacancy concentration. We observed intrinsic failure characteristics of the NW as insensitive to the temperature. Overall, the new understanding of material properties and failure characteristics of Si0.5Ge0.5 NW elicited in this study will be a guide for designing Si–Gebased nanodevices.

Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11051-020-05040-0) contains supplementary material, which is available to authorized users. M. H. Rahman : E. H. Chowdhury Department of Mechanical Engineering, Bangladesh University of Engineering and Technology, Dhaka 1000, Bangladesh M. M. Islam (*) Department of Mechanical Engineering, Wayne State University, Detroit, MI 48202, USA e-mail: [email protected]

Keywords Silicon-germanium . Molecular dynamics . Tersoff potential . Nanodevices . Thermoelectric . Nanostructures

Introduction Silicon-germanium (SixGe1-x) is an alloy with any molar ratio of silicon (Si) and germanium (Ge). SixGe1-x is a semiconducting and thermoelectric material that has been successfully deployed in heterojunction bipolar transistor, strained metal-oxide-semiconductor (MOS), complementary metal-oxide-semiconductor (CMOS), and many other electronic systems (Haddara et al. 2017; Wang et al. 1995). Recently, nanowires (NW) have received significant attention in the scientific community for their distinctive thermal, mechanical, electronic, and optical properties and extensively studied for potential applications as building blocks in nanoelectromechanical devices (NEMS) (Lu and Lieber 2006; Hochbaum and Yang 2010; Rurali 2010). The NWs are excellent candidates for optoelectronic and nanoelectronics devices (Zhang et al. 2011), detectors, and sensors for biological and chemical applications (Eom et al. 2011), ultrahigh-frequency resonators (Feng et al. 2007), and energy harvesting (Lee et al. 2012). The Si NWs are extensively studied because of their exceptional properties and enormous applications in electrical and optical nanodevices and NEMS (Morales and Lieber 1998;