A study of ultrathin dielectric films by Atomic and Electrostatic Force Microscopy

Ultrathin Langmuir-Blodgett (LB) and oxide films were studied using an atomic force (AFM) and electrostatic force (EFM) microscopy. The LB films were deposited by a subsequent transfer of monolayers of either an amphiphilic ate-compound or an amphiphilic copper phthalocyanine from the water surface onto a glass substrates covered with ITO or Al electrodes. The Al2O3 layers studied were natural oxide films on Al electrodes. The topography and the local surface potential was studied by AFM and EFM, respectively. The films were also poled locally by an external electric voltage applied between a tip and the rear electrode. This way a surface charge was deposited onto the film surface. The dynamics of the electric field relief above the poled area was studied by EFM imaging with simultaneous control of the topographic relief. In order to explain an image contrast a simple model is suggested for a thin dielectric film under a conductive EFM tip.