Phase Diagram of Laser Induced Melt Morphologies on Silicon

During cw laser induced melting, over a large range of intensities, silicon films phase separate into patterns of coexisting solid and molten regions. We have identified several distinct and reproduceable morphologies of this inhomogeneous coexistence region ranging from random lamellae (“amorphous”) structures to periodically ordered (“crystalline”) strips. The type of morphology formed is a function of laser intensity and spot size and these parameters can be viewed as constituting the two axes for a steady state “phase diagram” of the structures. “Phase transitions” between these structures occur for small changes of the experimental parameters with the fraction of liquid being an order parameter.