Scanning tunneling microscopy and spectroscopy of Langmuir-Blodgett films of ion-exchange polymers: 2D conductivity, resonant tunneling, and charge superstructure
Maslova N. S. , Moiseev Yu. N. , Savinov S. V. , Yusupov R. G.
Scanning tunneling microscopy and scanning tunneling spectroscopy (STM-STS) have been used to study monomolecular layers of an ion-exchange polymer. In a study of films containing an odd number of layers, an anomaly was found on the plot of dI/dV{ V): a conductance peak on the order of 150-200 mV wide near zero bias voltage. In addition, the results reveal a 3 X 2 surface reconstruction corresponding to a charge density wave and an oscillatory current-voltage characteristic. Generation of the feedback system of the microscope can arise in negative-slope regions on the current-voltage characteristic. The observed effects can be explained by noting that the density of states is determined by a superposition of effects stemming from the 2D nature of the conductance and a charge density wave.