Using atomic force microscopy to reveal the nature of extended defects in organic semiconductors: the role of crystal growth mechanisms

Abstract

Optical and atomic force microscopy measurements on the {001} form of the organic semiconductor quaterthiophene revealed interlaced spiral patterns arising from growth layers mutually rotated by 180° about the normal to the (001) crystal face. This bulk-surface relationship, along with the height of the exposed step ledges of the order of 10-100 nm, evidences the complex polytypic nature of these crystals in which the basic P21/c layer gives rise to several different stacking along [001], even within the same crystallite. The consequences on solid state physical properties arising from these crystal growth phenomena are briefly discussed.