Nanostructure formation in spin-cast polystyrene films

The dependence of spin-cast polystyrene film thickness on silicon substrate s is examined as a function of concentration (in toluene) and molecular wei ght. For uniform films ranging in thickness from 100 Angstrom to 1 mu m, th ickness follows a power law dependence on concentration, with the power var ying from 1.25 at low molecular weights, to greater than 2 at the highest m olecular weights examined. For very dilute concentrations, atomic force mic roscopy reveals that the films break up into a uniform distribution of void s or islands with submicron dimensions, as has been observed previously. Th e apparent film thickness (at molecular weight 690000), is determined by se condary ion mass spectrometry, and is found to vary linearly with concentra tion for film thicknesses below similar to 30 Angstrom, the thickness at wh ich the film begins to break up. At this molecular weight, X-ray reflectivi ty results indicate that the limiting thickness of the remnant polymer regi ons is similar to 30 Angstrom. Effects of annealing are also investigated. (C) 2000 Society of Chemical Industry.