抄録
Surface energy and surface stress is a key parameter for predicting of the intrinsic stress of thin film. We have evaluated the statistical properties of the surface energy and the surface stress of amorphous silicon by using molecular dynamics, and obtained values of 1.44±0.03J/m2 and -0.48±0.06N/m respectively for 67nm2 surface area. Since it has been determined that dispersion shows a normal distribution, that of an area of any size can be predicted by the central limit theory. The coefficients of variation in an area of 1nm2 are 20.1% and 108.3%, respectively. It is found that the dispersion of surface stress is significantly large. For applications in the continuum mechanics, the surface stress can be treated as the initial stress generated in a surface region with a thickness of about 0.4nm. Though the elastic constants are decreased due to the surface effect, the difference of the strain is only about 7% for a film with 3.8nm thickness. The surface stress is strongly dependent on the reconstruction of the surface atoms. The contribution of surface reconstruction of amorphous silicon is larger than that of Si (100) 1×1 surface.
