Reciprocal-space mapping of lateral single-crystal domains with grazing-incidence x-ray diffraction for tetracene on H/Si(001)

Abstract

We have measured in-plane single-crystal domain changes in size and shape for a tetracene film on H/Si(001)-2\ifmmode\times\else\texttimes\fi{}1 as a function of film thickness and substrate step density using grazing-incidence x-ray diffraction (GIXD). The x-ray results reveal that the film is commensurate with the substrate along the a axis of the tetracene lattice (i.e., the longer base vector of the a-b plane unit cell). The preferred crystalline domain growth direction is found to be along the b axis (the shorter base vector of the unit cell). The single-crystal domain size is layer dependent and orders of magnitude smaller than a typical surface island observed using atomic-force microscopy (AFM). The domain size and shape are sensitive to the substrate step density and step anisotropy. The mechanism of substrate step influence on the domain properties has been discussed.