Modelagem computacional da interação entre discordâncias parciais a 90 graus e a superfície (111) do silício

Abstract

Understanding the structural properties of dislocations is essential since these defects govern the processes plastic deformation of materials. Particularly in semiconductors, these studies are important given the relevance of these materials for microelectronics. In this work, our focus will be the 90o partial dislocations in silicon. For the theoretical study of atomic-scale crystal dislocations, we use simulations based on semi-empirical quantum-mechanical methods closely linked to the tight-binding treatment, since it considers in its formulation that crystalline electronic states can be described in terms of atomic orbitals: Density Matrix Method Tight-Binding Order-N (DMTB). This method has a low computational cost which allows us to work with very large systems atoms in structures representation -including thousands of sites. In short, we describe how to produce and represent the 90o partial dislocations in Si, we consider three models for its core structure: a unreconstructed where the atoms have an almost fivefold coordination; a model reconstructed with period equal to the perfect lattice; and a model with twice period comparing with the perfect lattice. Finally, we calculate the range in energy of the system with the distance between the dislocations and the free surface of Si.