Date of Graduation
Eberly College of Arts and Sciences
Physics and Astronomy
M. E. Bachlechner.
Thin films of silicon nitride on silicon are well suited materials for many applications including photovoltaics. Large-scale molecular-dynamics simulations of silicon/silicon nitride interfaces under externally applied tensile strain are performed in an attempt to improve understanding of this interface. The simulations reveal stress release in form of fracture, slip, pit formation, and interface phase transition under high stress condition. The silicon/silicon nitride interface is described as an eight-component system thereby offering valuable information in some of the thirty-six different pair distribution functions. We find that fracture in silicon nitride, with a centerpiece breaking off the sides, is reflected in a return to the original height of the first peak of the Si-N pair distribution function indicating that this centerpiece is essentially unstretched. Slip and pit formation in silicon as well as formation of domains of two different interface phases are identified by additional peaks in the pair distribution functions at and across the interface. Understanding selective pair distribution functions calculated at various stages of a particular simulation offer the opportunity to analyze structural and mechanical failure of large systems without knowing the detailed properties of individual atoms in the system. In particular, the occurrence of peaks reflecting new interatomic distances allows early predictions of failure.
Cao, Deng, "Pair distribution functions in molecular dynamics simulations of interfaces" (2006). Graduate Theses, Dissertations, and Problem Reports. 2352.