Time-resolved study of laser-induced disorder of Si surfaces

Optical second-harmonic studies show that the electronic structure in the top 75--130 A{} of a crystalline Si surface loses cubic order only 150 fsec after the Si is excited by an intense 100-fsec optical pulse. This suggests that atomic disorder can be induced directly by electronic excitation, before the material becomes vibrationally excited. In contrast, the electronic properties of the equilibrium molten phase are not obtained for several hundreds of femtoseconds.