Surface structure of ultrathin smectic films on silicon substrates: Pores and islands

摘要: We present an atomic force microscopy (AFM) and ellipsometry study of ultrathin smectic films on silicon substrates. By controlling the amount liquid-crystal material that is spin coated substrate, we are able to prepare consisting a defined small number (ranging from 1 4) layers. AFM measurements show possess specific surface structure with lateral feature size few microns steplike height variations 3.3 nm. The steps corresponds layer spacing used, indicating result partial formation topmost these films. pattern either isolated islands (regions in which film thickness enhanced by one layer) or consists pores (film decreased layer). A smooth only obtained if precisely tuned certain values, complete top layer. well-defined relation exists between liquid crystal concentration spin-coating solution structure, enabling controlled generation island structures, pore surfaces. two-dimensional stable time scale days. Preliminary results concerning thermal stability reported. Our highlights usefulness for