Patent ID: 8221544

Claim:
A method of preparing a polycrystalline film, the method comprising: (a) providing a substrate having a thin film disposed thereon, said film capable of laser-induced melting; (b) generating a sequence of laser pulses having a fluence that is sufficient to melt the film throughout its thickness in an irradiated region, each pulse forming a line beam having a length, width and a length to width aspect ratio greater than 50, said width sufficient to substantially prevent nucleation of solids in a portion of the thin film that is irradiated by the laser pulse; (c) irradiating a first region of the film with a first laser pulse to form a first molten zone, said first molten zone demonstrating a variation in width along its length to thereby define a maximum width (W max ) and a minimum width (W min ), wherein W max is less than about 2×W min , and wherein the first molten zone crystallizes upon cooling to form one or more laterally grown crystals, wherein the crystals grow substantially perpendicular to the length of the line beam; (d) laterally displacing the film relative to the line beam in the direction of lateral crystal growth a distance that is greater than about one-half W max and less than W min ; and (e) irradiating a second region of the film with a second laser pulse to form a second molten zone having a shape that is substantially the same as the shape of the first molten zone, wherein the second molten zone crystallizes upon cooling to form one or more laterally grown crystals that are elongations of the one or more crystals in the first region.