Observation of nano-dewetting structures

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Abstract
We have studied the dewetting of thin polymer films (polystyrene) on top of different silicon substrates. With diffuse X-ray scattering and scanning-force microscopy a high in-plane resolution was achieved. Besides the well-known mesoscopic dewetting structures of drops with diameters in the range of several micrometers we detect a further morphological feature. Depending on the thickness of the native silicon oxide layer, inside the dewetted areas small dimples are formed. This nano-dewetting structure can be understood as the result of the dewetting of a remaining ultra-thin film and is compared with theoretical predictions of spinodal decomposition. This observation of another length scale provides some new aspects on the molecular mechanism of polymer dewetting.