Phase change nanodot arrays fabricated using a self-assembly diblock copolymer approach

Self-assembling diblock copolymer, polystyrene-b-poly-4-vinylpyridine (PS-b-P4VP), was used as the template for fabricating phase change nanostructures. The high density GeSb nanodots were formed by etching into an amorphous GeSb thin film using silica hard mask which was patterned on top of polymer. The nanodot arrays are 15 nm in diameter with 30 nm spacing. This is smaller than most structures obtained by e-beam lithography. Time-resolved x-ray diffraction studies showed that the phase transition occurred at 235 degrees C, which is 5 degrees C lower than blanket GeSb film but higher than that of Ge2Sb2Te5 (150 degrees C). GeSb showed good temperature stability for fabrication of small memory devices. (C) 2007 American Institute of Physics.