PHOTOISOMERIZATION OBSERVED BY MEANS OF SCANNING-TUNNELING-MICROSCOPY

We have studied the interfacial structure of a photochromic molecule, 4,4'-dioctyloxyazobenzene (8AB8), on molybdenum disulphide by means of scanning tunneling microscopy (STM) with molecular resolution. We fou nd at least two interfacial structures. The STM image of one of the st ructures was easily distorted upon irradiation with UV light, while th at of the other structure was quite stable under UV light irradiation. In a wide area of several hundred nanometers, we observed that some s teps with equal height changes of 1.1 nm moved during the irradiation. We interpreted that trans-cis photoisomerization causes molecular lay ers to be torn off one by one.