Near-field scanning optical microscopy of temperature- and thickness-dependent morphology and fluorescence in Alq(3) films

We use near-field scanning optical microscopy (NSOM) to probe the local opt ical and morphological properties in annealed, vacuum-deposited Alq(3) film s (10-480-nm thick) with 18-100-nm resolution. We use concurrent shear forc e microscopy lan analogue to atomic farce microscopy, AFM) to correlate the morphology of different regions to intensity variations in our fluorescenc e images as well as variations in the localized fluorescence spectra. We ha ve observed nanoscale effects of annealing temperature on film morphology a nd 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). Film s annealed above T-g (T = 200 <degrees>C for the same amount of time exhibi t increased surface morphology and decreased fluorescence. In sufficiently thick films (approximate to 500 nm) annealed at 200 degreesC, We observe th e formation of microcrystalline domains.