Photoelectrochemical properties of hierarchical nanocomposite structure: Carbon nanofibers/TiO2/ZnO thin films

The basic objective of this work is related to the research on the design of hierarchic multilayer systems with the assumed final functionality utilized for microelectronics and photovoltaics. We report on photoelectrochemical functionality of the multilayer system consisting of carbon nanofibers (CNFs)/photoactive anatase TiO2/conductive ZnO thin films. The CNFs’ layers were obtained by annealing the polyacrylonitrile (PAN) web deposited by the electrospinning method. Titanium dioxide and zinc oxide layers were deposited by means of a hollow cathode cold plasma deposition system. Raman spectra confirmed carbon nanofibers, crystalline TiO2 and ZnO forming individual layers as well as the final multilayer assembly. A mixture of various ZnxTiyOz phases was also observed. These structures were produced due to the reactions between the highly energetic zinc ions generated in the plasma environment and the TiO2 layer. The same phenomenon is probably responsible for the doping of TiO2 by carbon atoms originating from CNFs and leading to a significant decrease of the photocatalytic activity.