Effect of crystal anisotropy and adhesive forces on laser induced deformation patterns in covalently bonded thin films

Abstract

The effect of crystal structure on laser induced deformation patterns in thin films and surfaces is analyzed within the framework of a dynamical model for the coupled evolution of defect densities and deformation fields. In crystals with covalent bonding, such as Si and SiC, preferential bond breaking may occur, as a result of the relative orientation of the laser electric field and crystallographic axes. We extend here our theoretical framework to incorporate the effects of anisotropic defect diffusion, and the influence of film-substrate adhesion on deformation pattern selection and stability of thin films subjected to laser beams. We also compare theoretical predictions to experimental observations on single crystal silicon wafer surfaces. Furthermore, it is predicted that the laser induced damage threshold for SiC single crystals can be in excess of 200 J/cm 2 .

Statistical physical approach to describe the collective properties of dislocations

“…The reader can find the details e.g. in [35,36,37,38,39,40,42,43,44,45]. Although DDD simulations are extremely important for the better understanding of the collective properties of dislocations, due to their high computational demand their applicability in engineering practice is limited.…”

“…In DDD simulations the equations of motion of the dislocations (dislocation segments) are integrated numerically. During the past 15 years a vast amount of DDD simulations were performed both in 2D [46,47,48,49,50,51,52,53,54,55,56] and 3D [35,36,37,38,39,40,42,43,44,45]. The detailed descriptions of the numerical methods applied and the results obtained are out of the scope of the paper, but to demonstrate the potentials and the limitations of the numerical simulations we will shortly review simulation results obtained by the author [50,51] on the same system that is studied below in the statistical physics considerations.…”

“…For an individual dislocation one can find that 40) where v is the velocity of the dislocation line at a given point. It is important to note that if we added the gradient of an arbitrary vector field toĵ given above, this would also satisfy the conservation law (2.37).…”

Modeling Laser Effects on the Final Optics in Simulated IFE Environments

“…Development of a model for investigations of the influence of surface adhesion forces and coating crystal anisotropy on surface deformation of reflective coatings (Walgraef and Ghoniem, 2002).…”