Indirect molecular epitaxy: deposition of n-alkane thin films on Au coated NaCl(001) and HOPG(0001) surfaces

The epitaxial growth of organic molecules can lead to the formation of complex orientated morphologies. In previous work, we studied the kinetic and thermodynamic factors that drive the epitaxial growth of n-alkane thin films on HOPG(0001) and NaCl(001) by physical vapor deposition. A wide variety of morphologies are observed as a function of deposition conditions (substrate temperature, n-alkane chain length, etc.). In the current study we examine how a modified substrate (Au deposited on a HOPG(0001) or NaCl(001) substrate) affects the epitaxial growth of n-C36H74 (50 nm thick) relative to the uncoated substrates. This "indirect epitaxy", in which the patterned attractive forces of the substrate are transferred through a thin metal film, can tailor the conditions for epitaxial growth. The observation of fourfold symmetry for n-alkane growth on Au/NaCl(001) and sixfold symmetry for n-alkane growth on Au/HOPG(0001) demonstrates indirect epitaxy over a wide range of substrate temperatures during deposition.