Nanocomposites and nanomaterials

Mechanical properties of SiGe core-shell nanowires: molecular dynamics simulations
Semchuk S.S., Kuryiluk V.V.
Faculty of Physics, Taras Shevchenko National University of Kyiv. 64/13, Volodymyrska Street, City of Kyiv, Ukraine, 01601.  
E-mail: cavej85@gmail.com, kuryliuk@knu.ua 

Recently, Si/Ge core–shell nanowires (NWs) have been studied extensively, both experimentally and theoretically for their promising use in the current [1] and, potentially, the next generation of nanodevices [2,3]. In current planar technology essentially all high-performance Si-based microprocessors incorporate strain to enhance their performance. Core-shell structure offers a unique opportunity to control Young's modulus of the NW since it allows to rearrange Si and Ge atoms without compromising the electric properties of the NW.
This work focuses on the study of the mechanical properties of Si/Ge and Ge/Si core-shell NWs using molecular dynamics method. Young’s modulus and failure mechanism of the NWs is determined by calculating stress-strain dependencies. We first apply and test two different interatomic potentials, Tersoff and MEAM, to define the one that represents the mechanical properties of Si and Ge NW most accurately. Testing Tersoff and MEAM potentials for stress-strain dependence of Si and Ge NWs show that Tersoff potential fails to represent mechanical properties of Si and Ge nanowires in a way that would correspond to experimental data, while MEAM potential accurately displays both Young's modulus and failure mechanisms of the NWs.
Further study of mechanical properties of Si/Ge core-shell NWs shows that with the increase of Si to Ge ratio Young's modulus increases while staying within the limits of Young's modulus of Si and Ge respectively. Meanwhile, the ultimate strength of the NWs can exceed the corresponding value for pristine Si and Ge NWs. These results have a mirrored effect with Ge/Si core-shell NWs.

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