Low temperature growth of epitaxial pentacene films on the Si(1 1 1)-(√3 × √3)R30°-Ag surface

Pentacene thin films were grown on the Si(1 1 1)-(√3 × √3)R30°-Ag surface at low substrate temperature (120 K). The growth process was investigated by scanning tunneling microscopy and low energy electron diffraction. In contrast to the growth at room temperature when 3D pentacene agglomerates form on an initial self-assembled pentacene monolayer surface, we observed an epitaxial pentacene film growth at low temperature. The pentacene molecules adopt a planar, π-stacked geometry, aligned head-to-head to form one-dimensional structures within each layer. The structural evolution as a function of film thickness was analyzed in detail and the mechanism of low temperature growth was discussed.