Order-Disorder Transitions in the Melt Morphology of Laser-Irradiated Silicon

The melting of thin silicon films with continuous laser radiation is characterized by the formation of several distinct and reproducible microscopic patterns of solid and molten regions with various degrees of long-range order. The pattern formation reflects the competition between the coherent energy deposition from the laser beam and the incoherent heat loss via diffusion. A phase, or stability, diagram of the structures has been constructed and order-disorder nonequilibrium "phase" transitions between these melt morphologies have been demonstrated by changes of the laser intensity and/or spot size.