Direct STM observation of electron structure modification of naphthacenequinone molecules caused by photoisomerisation
Oreshkin A.I., Panov V.I., Vasil'ev S.I., Koroteev N.I., Magnitskii S.A.
PACS: 61.16.Ch, 68.18.+p, 68.55.Jk, 82.30.Qt
Light induced conformational transformations of the naphthacenequinone (NQ) molecules are observed by scanning tunneling microscopy (STM). NQ molecules packed in Langmuir Blodgett (LB) film are shown to form stable ordered structures on a surface of highly oriented pyrolitic graphite (HOPG). The distinct peak in local density of electronic states is detected which is characteristic for the 2-dimential character of conductivity. Additional sub-band of empty electronic states has been found for NQ molecules in form A and not found in form B. The constant height STM images of individual molecules in form A demonstrate an additional structure that indicates the conformational transition of NQ molecules. This transition is connected with the transfer of the phenoxy group from one oxygen to another.