Internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles

Abstract

Public Reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. We present a study of internal pressure and surface tension of bare and hydrogen coated silicon nanoparticles of 2-10 nm diameter as a function of temperature, using molecular dynamics simulations employing a reparametrized Kohen-Tully-Stillinger interatomic potential. The internal pressure was found to increase with decreasing particle size but the density was found to be independent of the particle size. We showed that for covalent bond structures, changes in surface curvature and the associated surface forces were not sufficient to significantly change bond lengths and angles. Thus, the surface tension was also found to be independent of the particle size. Surface tension was found to decrease with increasing particle temperature while the internal pressure did not vary with temperature. The presence of hydrogen on the surface of a particle significantly reduces surface tension ͑e.g., drops from 0.83 J/m 2 to 0.42 J/m 2 at 1500 K͒. The computed pressure of bare and coated particles was found to follow the classical Laplace-Young equation.

Probing the phonon confinement in ultrasmall silicon nanocrystals reveals a size-dependent surface energy

“…The values we calculated for c increase from $0.6 to $1 Nm À1 when the expected particle size, L increases from $0.7 to $2.7 nm. Despite the apparent mixed phase nature of the silicon nanoclusters in our samples and the fact that the reported values for the surface energy of amorphous silicon are typically lower than those for crystalline silicon, the wide range of values reported for the bulk surface energy, [42][43][44][45] in our view, justifies the single fit to the data in Fig. 7 assuming a straightforward capillary approach in accordance with the approximate but adequately precise Tolman relation, 46 Eq.…”

“…Of course, the presence of such an interface region might explain why the size effect of the surface tension appears to dominate any obvious phase dependency, although one cannot rule out other factors that are known to affect the surface energy, such as surface oxidation 47,48 or hydrogenation. 44 …”

Theoretical Study of a Thermophysical Property of Molten Semiconductors

“…Also, Rhim and Ishikawa fitted their surface tension data for molten Ge [11] as: γ = 583 − 0.08 (T − T m ) (mJ m −2 ), and for molten Si [10,24] Figures 2 and 3 reveal that there is about 6% and 4% difference beween the calculated and the experimental results for Si and Ge, respectively. This may be attributed to the fact that the surface tension of molten silicon and germanium is difficult to measure accurately, and consequently, the available experimental data for the surface tension of molten silicon [1][2][3][4][5] and molten germanium [5][6][7] is currently widely scattered, not only their absolute values but also their temperature dependence, and agreement between the existing experimental data is quite poor (for Si, γ ranges from 720 to 875 mJ/m 2 , whereas the range is 560-632 mJ/m 2 for Ge). The data reported in the literature suffer from experimental problems and the presence of impurities.…”

“…The surface tension is sensitive to even minute surface contamination. However, it has been measured for molten silicon and germanium at the melting points [1][2][3][4][5][6][7] and at different temperatures [8][9][10][11][12]. The surface tension of high-temperature melts is the most needed and the most poorly established property.…”

The Thermodynamic Characterization of Wetting by Submitting a Sessile Drop to Microgravity

“…At the same time, the surface energy interpretation has led to many misunderstandings of the wetting phenomenon on patterned surfaces [12,13]. The validity of Young's equation was questioned [6] at the nanoscale [14][15][16][17] and on flexible surfaces [17][18] as well. According to Leger and Joanny, [19] the effect of body forces such as gravity on the contact line is small for small drop volumes.…”