Visualization of surface-initiated amorphization in silicon upon excitation with fs laser pulses using real-time reflectivity measurements

We have investigated the melting and solidification dynamics in crystalline silicon employing real-time reflectivity measurements with ns resolution upon fs-laser irradiation at different wavelengths (258 nm, 1030 nm and 3000 nm). For all wavelengths, the amorphous phase can be obtained, strongly influenced by the crystal orientation. In particular, for Si(111) a competing counterpropagating solidification front is initiated at the surface. Combined with a optical modelling, the velocities of the two propagating interfaces can be determined. The results contribute to a better understanding of the solidification dynamics and form the basis of an improved control of the final material state achieved.