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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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Number of atoms with the specified nearest number of neighbours during the nanoindentation process at different temperatures.
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f9: Number of atoms with the specified nearest number of neighbours during the nanoindentation process at different temperatures.

Mentions: Figure 9 shows the variation of the number of six-coordinated atoms during the nanoindentation process at the different temperatures. No phase transformation occurs during the initial 10,000 MD steps. As the indenter penetrates the substrate, a fraction of the silicon atoms is transformed from the initial four-coordinated diamond cubic structure to a six-coordinated body-centred tetragonal structure. The number of transformed atoms is higher for nanoindentation at lower temperatures. The maximum number of transformed atoms at a temperature of 10 K is about twice the number observed at a temperature of 300 K. In addition, the difference in the maximum number of transformed atoms is higher in the interval from 100 to 200 K compared with the interval from 200 to 300 K, mainly because of the appearance of the Si-XIII phase atoms during nanoindentation, suggesting that the appearance of Si-XIII atoms facilitates the phase transformation process of monocrystalline silicon during nanoindentation. During unloading, the number of six-coordinated silicon atoms rapidly decreases, and only a few transformed atoms are distributed in the residual deformed region after the indentation.


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)

Number of atoms with the specified nearest number of neighbours during the nanoindentation process at different temperatures.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f9: Number of atoms with the specified nearest number of neighbours during the nanoindentation process at different temperatures.
Mentions: Figure 9 shows the variation of the number of six-coordinated atoms during the nanoindentation process at the different temperatures. No phase transformation occurs during the initial 10,000 MD steps. As the indenter penetrates the substrate, a fraction of the silicon atoms is transformed from the initial four-coordinated diamond cubic structure to a six-coordinated body-centred tetragonal structure. The number of transformed atoms is higher for nanoindentation at lower temperatures. The maximum number of transformed atoms at a temperature of 10 K is about twice the number observed at a temperature of 300 K. In addition, the difference in the maximum number of transformed atoms is higher in the interval from 100 to 200 K compared with the interval from 200 to 300 K, mainly because of the appearance of the Si-XIII phase atoms during nanoindentation, suggesting that the appearance of Si-XIII atoms facilitates the phase transformation process of monocrystalline silicon during nanoindentation. During unloading, the number of six-coordinated silicon atoms rapidly decreases, and only a few transformed atoms are distributed in the residual deformed region after the indentation.

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