Dislocation nucleation and propagation during thin film deposition under compression

In this paper, we study the nucleation of dislocations and their subsequent propagation, during thin film deposition, using the three-dimensional (3D) molecular dynamics (MD) method. Aiming to reveal the generic mechanisms. the case of tungsten on a substrate of the same material is investigated. The substrate is under uniaxial compression along the [111] direction, with the thermodynamically favored (011) surface being horizontal. The Simulation results indicate that the nucleation Starts with it surface step adhere in atom is squeezed to the layer above, generating a half-dislocation loop at the surface. It may then either propagate into the film or become the bottom of a sessile dislocation loop. In the first case. the dislocation loop. having it Burgers vector 1/2 [1 (1) over bar(1) over bar] on a (101) glide plane. propagates along the [1 (1) over bar(1) over bar] direction on the surface, and extends to about two atomic layers along the [111] direction. In the second case, the missing layer propagates along the [100] direction on the surface, extending to about four atomic layers along the [111] direction. In this case, the sessile dislocation has it Burgers vector 1/2[(1) over bar(1) over bar(1) over bar] on the plane (011). (C) 2002 Elsevier Science B.V. All rights reserved.