Low-frequency electrical current oscillations in the vapor-adsorbed state of some ferrocene derivatives

Abstract

Low-frequency oscillations in electrical (dark, i.e., unilluminated) current as a function of time have been observed in a specific temperature range in samples of some ferrocene derivatives, namely ferrocenecarboxylic acid, ferrocenecarbaldehyde and acetylferrocene, with adsorbed ethanol vapor at a pressure of 40 Torr in a sandwich-type cell. The dependence of the oscillatory behavior of current on the applied bias voltage across the electrodes has also been studied at a constant sample cell temperature for each material in the ethanol-vapor-adsorbed state. With increasing bias, increases in both the time interval between two consecutive current peaks (i.e. decrease in frequency of current oscillations) and current peak hight were observed for all of the materials studied. The oscillatory behavior of the current and the temperature at which oscillations occurred depended on the nature of the ferrocene derivative. Existing theories of current oscillations in semiconductors have failed to explain the observed low-frequency current oscillations in these organometallic semiconductors. Such current oscillations are possibly associated with some kind of time-dependent phase changes in the ferrocene derivative–ethanol system at the sample surface layer.