Laser annealing of copper and silicon thin films

Studies of transient and permanent surface structures formed on copper and silicon thin films (about 1000 Å thick) as a result of low‐intensity Ar⁺ laser pulses are presented. Using Nomarski interferometric microscopy and backscattered light photography it was found that following the film melting a transient bubble is formed on the surface. The bubble size is comparable with the beam diameter and its height may exceed several microns. On solidification this bubble shrinks to a considerably lower permanent structure. A monochromatic light beam focused on these surface structures produces a characteristic backscattered pattern of dark rings superimposed on a bright circular patch. The dark rings are the result of interference between the beams reflected from the bubble external surface and the layer underneath. Transient bubbles can thus be observed using the interacting beam itself as a light source. Some examples of permanent and transient structures obtained under various beam parameters are presented.