Effects of Solvent and Ambient Humidity on Nanodot Structures for Near-Field Optical Data Storage Using Self-Assembled Diblock Copolymer

We present the formation of nanodot structures on a glass substrate by the self-assembly of a diblock copolymer. The structures can be used as nanopatterned media for near-field optical data storage with high data density. Improvements in the carrier-to-noise ratio (CNR) and in the uniformity of the recorded bit marks are expected with these structures. It is found that the structure of nanodots depends strongly on the ambient humidity during dripping and subsequent spin-casting and also on the solvent used. Nanodots of uniform size can be formed on a glass substrate with benzene, toluene, or toluene blended with acetone as a solvent when the ambient humidity is in the range of 60% to 70%. The size of the individual nanodots as well as the distance between two consecutive nanodots can be controlled, and the nanodots may be aligned like regular hexagonal close-packed structures by adjusting the volume ratio of acetone to toluene.