Molecular Dynamics Studies of Surface Nucleation and Crystal Growth of Si on SiO2 Substrates

2005 ◽  
Vol 899 ◽  
Author(s):  
Byoung-Min Lee ◽  
Hong Koo Baik ◽  
Takahide Kuranaga ◽  
Shinji Munetoh ◽  
Teruaki Motooka
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Crystal Growth ◽  
Surface Energy ◽  
Md Simulations ◽  
Lower Surface ◽  
Surface Nucleation ◽  
Lower Surface Energy ◽  
Potential Parameters ◽  
Si Thin Film

AbstractMolecular dynamics (MD) simulations of atomistic processes of nucleation and crystal growth of silicon (Si) on SiO2 substrate have been performed using the Tersoff potential based on a combination of Langevin and Newton equations. A new set of potential parameters was used to calculate the interatomic forces of Si and oxygen (O) atoms. It was found that the (111) plane of the Si nuclei formed at the surface was predominantly parallel to the surface of MD cell. The values surface energy for (100), (110), and (111) planes of Si at 77 K were calculated to be 2.27, 1.52, and 1.20 J/m2, respectively. This result suggests that, the nucleation leads to a preferred (111) orientation in the poly-Si thin film at the surface, driven by the lower surface energy.

Fabrication of Polycrystalline Si Thin Film for Solar Cells

1996 ◽  
Vol 452 ◽  
Author(s):  
M. Tanaka ◽  
S. Tsuge ◽  
S. Kiyama ◽  
S. Tsuda ◽  
S. Nakano
Keyword(s):  
Thin Film ◽  
Solar Cells ◽  
Crystal Growth ◽  
Conversion Efficiency ◽  
Solid Phase ◽  
Low Cost ◽  
Back Surface ◽  
Nucleation Layer ◽  
Surface Reflection ◽  
Si Thin Film

AbstractThe a-Si/poly-Si thin film tandem solar cell is a promising candidate for low-cost solar cells. We have conducted R&D on poly-Si thin film using the Solid Phase Crystallization (SPC) method from amorphous silicon (a-Si). To improve the film quality of SPC poly-Si, we have developed a new SPC method called the partial doping method. This method features two stacked starting a-Si layers, a P-doped layer and a non-doped layer. Nucleation occurs in the P-doped layer, and the non-doped layer is the crystal growth layer. For the nucleation layer, we developed a Si film with a unique structure, which features relatively large crystallites (-1000A) embedded in a matrix of amorphous tissue. By combining these technologies, a conversion efficiency of 9.2% was obtained for poly-Si thin-film solar cells. For further improvement in the conversion efficiency, based on the concept of “independent control of nucleation and crystal growth”, it is necessary to combine the best fabrication methods for each layer. A high conversion efficiency of more than 12% was found possible by using the CVD method and a new back surface reflection structure.

scholarly journals Thermodynamics of manganese oxides: Sodium, potassium, and calcium birnessite and cryptomelane

2017 ◽  
Vol 114 (7) ◽  
pp. E1046-E1053 ◽  
Author(s):  
Nancy Birkner ◽  
Alexandra Navrotsky
Keyword(s):  
Surface Energy ◽  
Surface Area ◽  
Oxidation State ◽  
Manganese Oxides ◽  
Lower Surface ◽  
Surface Energies ◽  
Surface Areas ◽  
Bulk Thermodynamics ◽  
Lower Surface Energy

Manganese oxides with layer and tunnel structures occur widely in nature and inspire technological applications. Having variable compositions, these structures often are found as small particles (nanophases). This study explores, using experimental thermochemistry, the role of composition, oxidation state, structure, and surface energy in the their thermodynamic stability. The measured surface energies of cryptomelane, sodium birnessite, potassium birnessite and calcium birnessite are all significantly lower than those of binary manganese oxides (Mn3O4, Mn2O3, and MnO2), consistent with added stabilization of the layer and tunnel structures at the nanoscale. Surface energies generally decrease with decreasing average manganese oxidation state. A stabilizing enthalpy contribution arises from increasing counter-cation content. The formation of cryptomelane from birnessite in contact with aqueous solution is favored by the removal of ions from the layered phase. At large surface area, surface-energy differences make cryptomelane formation thermodynamically less favorable than birnessite formation. In contrast, at small to moderate surface areas, bulk thermodynamics and the energetics of the aqueous phase drive cryptomelane formation from birnessite, perhaps aided by oxidation-state differences. Transformation among birnessite phases of increasing surface area favors compositions with lower surface energy. These quantitative thermodynamic findings explain and support qualitative observations of phase-transformation patterns gathered from natural and synthetic manganese oxides.

Bulk and (001) Surface Properties of TiAl3 Compound

2011 ◽  
Vol 299-300 ◽  
pp. 417-421
Author(s):  
Li Wang ◽  
Jian Hong Gong ◽  
Jun Gao
Keyword(s):  
Surface Energy ◽  
Structural Relaxation ◽  
Density Functional ◽  
Dominant Role ◽  
Lower Surface ◽  
Heat Of Formation ◽  
Lattice Constants ◽  
Structural And Electronic Properties ◽  
The Stability ◽  
Lower Surface Energy

The structural and electronic properties of bulk and (001) surface of TiAl3 have been examined by the first-principles total-energy pseudopotential method based on density functional theory. The lattice constants and heat of formation of bulk TiAl3 we obtained are in good agreement with the experimental and other theoretical values. The calculated bulk properties indicates that bonding nature in TiAl3 is a combination of metallic and ionic, in which the metallic bonding become the predominate one. the strongest hybridization exist in the DO22 structure, the Al-3p and Ti-3d bonding of TiAl3 play the dominant role in hybridization. The structural relaxation and surface energy for (001) slab have been simulated to make sure the stability of slabs with different atomic layers. Compared to TiB2 (0001) slab, TiAl3 surfaces shows smaller structural relaxation and lower surface energy, furthermore, the charge redistribution of (001) slab shows almost the same characteristics as bulk TiAl3, which confirms structural stability of TiAl3 with (001) slab. This present work makes a beneficial attempt at exploring TiAl3 surface as an ab initio method for studying possible nucleation mechanism of Aluminum on it.

Hydrogen Adsorption of Carbon Nanocone Arrays: Influences of Cone Arrangements

2013 ◽  
Vol 845 ◽  
pp. 345-349
Author(s):  
I Ling Chang ◽  
Ming Liang Liao ◽  
Chi Hsiang Chuang
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Adsorption ◽  
Md Simulations ◽  
Critical Value ◽  
Lennard Jones Potential ◽  
Jones Potential ◽  
Weight Percentage ◽  
Curvature Effects ◽  
Lennard Jones ◽  
Potential Parameters

This paper used molecular dynamics (MD) simulations to investigate influences of cone arrangements (including the cone orientation, arrangement pattern and cone spacing) on hydrogen adsorption of open-tip carbon nanocone (CNC) arrays at temperatures of 100 and 300 K. To consider curvature effects for the cone structure of the CNCs, the curvature-modified Lennard-Jones potential parameters were adopted to describe the interactions between the hydrogen and carbon atoms. It was found that the cone orientation (aligned, opposite, and alternate) does not have obvious influences on hydrogen adsorption of the CNC arrays. The arrangement pattern (square and triangular), however, had significant influences on the hydrogen adsorption. The square-patterned CNC array was noticed to have higher storage weight percentage than the triangular-patterned one. Regarding to the influences of cone spacing, the storage weight percentage grew with the increase of the cone spacing and arrived at a stable value as the cone spacing reached a certain critical value. The influences cone arrangements could be ascribed to repulsive effects, which are evident as cone spacing become narrow.

scholarly journals INVESTIGATIONS OF RESISTANCE TO SEIZING OF LASER-TEXTURED ELEMENTS

1970 ◽  
pp. 3-6
Author(s):  
Bogdan Antoszewski
Keyword(s):  
Surface Energy ◽  
Lower Surface ◽  
Texture Effect ◽  
Lower Surface Energy

The paper presents results of experiments concerning the assessment of the texture effect on scuffing resistance. The results showed that texturing  causes an increase in scuffing resistance. In addition, textures showing lower surface energy and having higher volume were found  to form surfaces more resistant to scuffing.

Molecular-Dynamics Simulations of Hydrogenated Amorphous Silicon Thin-Film Growth

1995 ◽  
Vol 408 ◽  
Author(s):  
T. Ohira ◽  
O. Ukai ◽  
M. Noda ◽  
Y. Takeuchi ◽  
M. Murata ◽  
...  
Keyword(s):  
Thin Film ◽  
Molecular Dynamics ◽  
Amorphous Silicon ◽  
Film Growth ◽  
Hydrogenated Amorphous Silicon ◽  
Md Simulations ◽  
Thin Film Growth ◽  
Silicon Thin Film ◽  
Radical Migration ◽  
Hydrogenated Amorphous

AbstractWe have performed molecular-dynamics (MD) simulations of hydrogenated amorphous silicon (a-Si:H) thin-film growth using realistic many-body semiclassical potentials developed to describe Si-H interactions. In our MD model, it was assumed that SiH3, SiH2 and the H radicals are main precursors for the thin-film growth. In MD simulations of a-Si:H thin-film growth by many significant precursor SiH3 radicals, we have evaluated average radical migration distances, defect ratios, hydrogen contents, and film growth rates as a function of different incident radical energies to know the effect of the radical energization on the properties. As a result of the comparison between the numerical and experimental results, it was observed that the agreement is fairly good, and that an increase of radical migration distance due to the radical energization is effective on a- Si:H thin-film growth with a low defect.

Sign in / Sign up

Export Citation Format

Share Document