Modification of the surface potential of azobenzene-containing Langmuir-Blodgett films in the near field of a scanning Kelvin microscope tip by irradiation

For the first time a light-induced local modification of the surface potent ial of an azobenzene-containing film in the near field of a scanning force microscope tip has been observed. The modification occurred when the tip wa s scanned a fixed distance from the surface (in noncontact mode) while simu ltaneously irradiating the sample with light of low intensity. The locally modified regions are detected as areas with more negative surface potential . The smallest size of these areas is several hundred nanometers with a dif ference in surface potential of a few hundred millivolts. No alterations in topography were observed.