Methods for forming a single crystal semiconductor thin film layer from a non-single crystal layer includes directing a light source having a homogenized intensity distribution and a modulated amplitude towards the non-single crystal layer, and relatively moving the light with respect to the layer wherein the amplitude of the conditioned light is preferably increased in the direction of relative motion of the light to the layer. Preferred methods also include multiple light exposures in overlapping series to form ribbon-shaped single crystal regions, and providing a low temperature point in the semiconductor layer to generate a starting location for single crystalization.