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Molecular dynamics investigations of mechanical behaviours in monocrystalline silicon due to nanoindentation at cryogenic temperatures and room temperature.

Du X, Zhao H, Zhang L, Yang Y, Xu H, Fu H, Li L - Sci Rep (2015)

Bottom Line: Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K.By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process.The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science and Engineering, Jilin University, Renmin Street 5988, Changchun, Jilin 130025, China.

ABSTRACT
Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K. Furthermore, the load-displacement curves were obtained and the phase transformation was investigated at different temperatures. The results show that the phase transformation occurs both at cryogenic temperatures and at room temperature. By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process. The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter. Moreover, through the degree of alignment of the metastable phases along specific crystal orientation at different temperatures, it was found that the temperature had effect on the anisotropy of the monocrystalline silicon, and the simulation results indicate that the anisotropy of monocrystalline silicon is strengthened at low temperatures.

No MeSH data available.


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Three-dimensional MD model of the monocrystalline silicon and the nanoindenter.
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f1: Three-dimensional MD model of the monocrystalline silicon and the nanoindenter.

Mentions: For the simulation, a three-dimensional MD nanoindentation model was constructed, which is as illustrated in Fig. 1. The simulation model consists of a monocrystalline silicon substrate and a rigid spherical indenter with a radius of 5.0 nm. The model scale had to be large enough to eliminate the size effect, which would make the simulation computationally expensive24. Thus, a reasonable specimen volume was selected (21.7 nm × 13.57 nm × 21.7 nm), containing 325,240 atoms, based on the assumption that the velocities and displacements of the atoms during the nanoindentation simulation were not affected by the controlled volume. Periodic boundary conditions4182425 were chosen for the X and Z direction to reduce the effect of the simulation scale. The silicon atoms in the substrate were divided into three kinds of atoms, i.e., boundary atoms, thermostatic atoms and Newtonian atoms. The boundary atoms at the bottom of the substrate were fixed at their initial lattice position to provide structural stability and prevent the specimen from translating during the nanoindentation process. The next layers of atoms adjacent to the boundary atoms were considered to be thermostatic atoms to ensure a reasonable outward heat conduction. The remaining atoms were considered to be Newtonian atoms, i.e., their motion (as well as the motion of the thermostatic atoms) was set to obey Newton’s second law of motion.


Molecular dynamics investigations of mechanical behaviours in monocrystalline silicon due to nanoindentation at cryogenic temperatures and room temperature.

Du X, Zhao H, Zhang L, Yang Y, Xu H, Fu H, Li L - Sci Rep (2015)

Three-dimensional MD model of the monocrystalline silicon and the nanoindenter.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4633730&req=5

f1: Three-dimensional MD model of the monocrystalline silicon and the nanoindenter.
Mentions: For the simulation, a three-dimensional MD nanoindentation model was constructed, which is as illustrated in Fig. 1. The simulation model consists of a monocrystalline silicon substrate and a rigid spherical indenter with a radius of 5.0 nm. The model scale had to be large enough to eliminate the size effect, which would make the simulation computationally expensive24. Thus, a reasonable specimen volume was selected (21.7 nm × 13.57 nm × 21.7 nm), containing 325,240 atoms, based on the assumption that the velocities and displacements of the atoms during the nanoindentation simulation were not affected by the controlled volume. Periodic boundary conditions4182425 were chosen for the X and Z direction to reduce the effect of the simulation scale. The silicon atoms in the substrate were divided into three kinds of atoms, i.e., boundary atoms, thermostatic atoms and Newtonian atoms. The boundary atoms at the bottom of the substrate were fixed at their initial lattice position to provide structural stability and prevent the specimen from translating during the nanoindentation process. The next layers of atoms adjacent to the boundary atoms were considered to be thermostatic atoms to ensure a reasonable outward heat conduction. The remaining atoms were considered to be Newtonian atoms, i.e., their motion (as well as the motion of the thermostatic atoms) was set to obey Newton’s second law of motion.

Bottom Line: Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K.By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process.The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter.

View Article: PubMed Central - PubMed

Affiliation: School of Mechanical Science and Engineering, Jilin University, Renmin Street 5988, Changchun, Jilin 130025, China.

ABSTRACT
Molecular dynamics simulations of nanoindentation tests on monocrystalline silicon (010) surface were conducted to investigate the mechanical properties and deformation mechanism from cryogenic temperature being 10 K to room temperature being 300 K. Furthermore, the load-displacement curves were obtained and the phase transformation was investigated at different temperatures. The results show that the phase transformation occurs both at cryogenic temperatures and at room temperature. By searching for the presence of the unique non-bonded fifth neighbour atom, the metastable phases (Si-III and Si-XII) with fourfold coordination could be distinguished from Si-I phase during the loading stage of nanoindentation process. The Si-II, Si-XIII, and amorphous phase were also found in the region beneath the indenter. Moreover, through the degree of alignment of the metastable phases along specific crystal orientation at different temperatures, it was found that the temperature had effect on the anisotropy of the monocrystalline silicon, and the simulation results indicate that the anisotropy of monocrystalline silicon is strengthened at low temperatures.

No MeSH data available.


Related in: MedlinePlus