Clean thin samples of silicon (111) have been irradiated by 350–400 ns dye‐laser pulses of 590 nm radiation under ultrahigh vacuum (UHV) conditions. Results obtained using a UHV transmission electron microscope on the thermal shock cleavage of these samples are reported. Classic cleavage along {111} planes was observed at relatively low fluences (less than 0.04 J/cm2). The observations on the sample morphology before and after laser irradiation demonstrate that under the conditions that yield to cleavage, there is no long range diffusion of point defects and there is no tendency for the cleavage to occur at pre‐existing defects. Although in some cases, cleavages occur at locations that are logically weak, in general, there appears to be no correlation between the cleavage sites and the three‐dimensional crystal structure.