DISLOCATION HOLLOW CORES OBSERVED ON SURFACES OF MOLECULAR ORGANIC THIN-FILMS - P-NITROPHENYL NITROXYL NITROXIDE RADICAL

We have studied by means of tapping mode atomic force microscopy ex si tu grown surfaces of highly-oriented cc-phase thin films of the molecu lar organic radical p-nitrophenyl nitroxyl nitroxide. The films are,gr own by thermal evaporation of the precursor radical in high vacuum on glass and NaCl(001) substrates. The surfaces reveal a complex nanomete r-scale morphology formed by a random distribution of dislocations ide ntified as spirals (screw dislocations) of opposite sign interacting i n pairs. Each spiral emerges from a hollow core with a diameter of ca 15-20 nm. The dislocation density is rather high due to the way in whi ch the films grow under the given experimental conditions. The out-of- plane growth of the films is governed by the Frank-Read source mechani sm. (C) 1998 Elsevier Science B.V. All rights reserved.