Relaxation of interface defects: elastic boundary conditions and bond order potentials in empirical molecular dynamics

1. Atomic region I Continuum region II I II Relaxation of interface defects: elastic boundary conditions and bond order potentials in empirical molecular dynamics simulations Kurt Scheerschmidt, Volker Kuhlmann, and Alexandre Yu. BeloV Max Planck Institute of Microstructure Physics, Weinberg 2, 06120 Halle, Germany, schee@mpi-halle.de Technical University of Dresden, Institute of Materials Science, Hallwachsstr. 3, 01062 Dresden, Germany Motivation: Wafer Bonding Processes Method: Classical Molecular Dynamics With empirical potentials and elastic BC • - atomic level processes • - defects and adsorbates • - misalignment • - miscut and steps • - interface structure • bondability • mechanics / electrics Dynamic coupling of atomic structures to an elastic continuum Homogeneous displacement fields from the linear anisotropic elasticity theory In 2D anisotropic elasticity problems The potential of a crystal with a defect is approximated as Complex parameters of 2D anisotropic elasticity theory generalized coordinates: ri– positions of atoms in region I ak – parameters of the elastic field Extended Langrangian of an atomic system coupled to an elastic continuum Generalized forces Elastic multipole expansions for flexible boundary conditions Equations of motion Bonding across surface steps Electronic interface structure of 90 degree twist Comparison of structure and energy: Dislocation dipole, relaxation at 0K TS, elasticBC - both the metastable semimetal interface and the dreidl structure are confirmed by DFT calculations - possibility of band gap tailoring ? • - bonding over monatomic steps yields 90 degree twist boundaries • bonding at double steps needs slow heat conduction and results • in 60-degree dislocations with eventually attached rows of • vacancies separated by a perfect interface TS, free+yPBC Bonding with small twist rotations: Screw dislocations a 4.6o, 37nm BOP4, free+yPBC b 6.7o+90o, 45nm 50nm c 400kV-plan view TEM of 2.4o- (100)-twist bonded interfaces (courtesy: R.Scholz, MPI-Halle) and simulated contrast varying twist and sample thickness 6.7o, 45nm HREM experimental (a) and simulated (b) images from the 4.6 degree twist bonded model (c) and filtered selections showing fringe termination 60 degree Dislocation, 900K annealing DISLOcation dipole, 600K annealing Potential and Total Energy , generalized Coordinates (A1,2,6) and Forces (Bi,2,6), Selected snapshots At start, applying Static displacements, And 100->300->900->0K Dipole of 60 degree dislocations at start and after annealing Temperature control and movement of both the dislocations 300K start 900K 0K 0K 100K