Near-field scanning optical microscopy of temperature- and thickness-dependent morphology and fluorescence in Alq3 films

We use near-field scanning optical microscopy (NSOM) to probe the local optical and morphological properties in annealed, vacuum-deposited Alq(3) films (10-480-nm thick) with 18-100-nm resolution. We use concurrent shear force microscopy lan analogue to atomic farce microscopy, AFM) to correlate the morphology of different regions to intensity variations in our fluorescence images as well as variations in the localized fluorescence spectra. We have observed nanoscale effects of annealing temperature on film morphology and fluorescence emission. Our studies show that Alq(3) films annealed below the glass transition temperature of Alq(3) (T < T-g = 172 <degrees>C) were very similar to unannealed films, except in very thin films (<50 nm). Films annealed above T-g (T = 200 <degrees>C for the same amount of time exhibit increased surface morphology and decreased fluorescence. In sufficiently thick films (approximate to 500 nm) annealed at 200 degreesC, We observe the formation of microcrystalline domains.