Patterning of phase change films with microlens arrays

Nanometer-sized features were fabricated on Ge1Sb2Te4 phase change films uniformly by irradiation with the fundamental and second harmonic components of a Nd:YAG laser through a microlens array. The effect of laser fluence and laser wavelength on the feature size was investigated. The change in the morphology and optical property of the phase change film was characterized. The smallest feature size of 355 nm was produced by using a low laser fluence and the 532 nm second harmonic of the laser. This was much smaller than the focus beam size of the microlens. The laser irradiation caused the formation of crystalline features on the amorphous phase change film. The amorphous region of the film could be removed by dipping in a NaOH solution, leaving the crystalline regions unaffected.