SCANNING-TUNNELING-MICROSCOPY OF ALKANE ADSORBATES AT THE LIQUID GRAPHITE INTERFACE

Scanning tunneling microscopy (STM) revealed a complex multilayered st ructure of the adsorbate, formed at the liquid/graphite interface from a saturated dodecane solution of the cyclic alkane, (CH2)48. Surface etching of the adsorbate was observed when the scanning area was dimin ished from large areas of several micrometers to submicrometer range. Two layers of adsorbate, each of ca. 0.6 nm in thickness, were removed by the scanning tip before well-ordered lamellar sheets were reached. STM images of such lamellar layers exhibit features related to the mo lecular structure of individual alkane molecules. After addition of (C H2)48 to C36H74 solution, a stable ordered bilayer of cyclic and norma l alkanes was observed. The observation of a sheet of cyclic alkanes l ying beneath a layer of normal alkanes was explained by stronger adhes ion of (CH2)48 molecules to the graphite surface.