Abstract
Molecular dynamics simulations were conducted to study the nanoindentation of monocrystalline germanium. The path of phase transformation and distribution of transformed region on different crystallographic orientations were investigated. The results indicate the anisotropic behavior of monocrystalline germanium. The nanoindentation-induced phase transformation from diamond cubic structure to β-tin-Ge was found in the subsurface region beneath the tool when indented on the (010) plane, while direct amorphization was observed in the region right under the indenter when the germanium was loaded along the [101] and [111] directions. The transformed phases extend along the < 110 > slip direction of germanium. The depth and shape of the deformed layers after unloading are quite different according to the crystal orientation of the indentation plane. The study results suggest that phase transformation is the dominant mechanism of deformation of monocrystalline germanium film in nanoindentation.
Highlights
Germanium plays a significant role in various fields such as solar cell, infrared optics, semiconductor, and photoelectric detection
To identify the different phases of silicon and germanium formed in nanoindentation or nanocutting by molecular dynamics (MD) simulation, the coordination number is usually taken into consideration
It is widely accepted that the atoms with coordination number 4 indicate the diamond cubic structure and the sixfold coordinated atoms are considered as the β-tin phase [7,9,11,16,25]
Summary
Germanium plays a significant role in various fields such as solar cell, infrared optics, semiconductor, and photoelectric detection. Many researchers have focused on phase transformations in silicon during nanoindentation by both experiments and molecular dynamics simulations. The explanation was that the initial plastic deformations were the twinning and dislocation slip. When the propagations of twinning and dislocation slip were blocked by increasing the load, the phase transformation started [12]. Molecular dynamics simulation of nanoindentation of germanium is rarely found except for Zhu and Fang’s study [16]. They proposed that a pressure-induced phase transformation was the dominant deformation mechanism of the monocrystalline Ge film instead of dislocation-assisted plasticity
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