Grazing-incidence X-ray Diffraction of Tetracene Thin Films on Hydrogenated Si(001) Substrate

Ex situ grazing-incidence X-ray diffraction (GIXD) and wide angle Bragg diffraction have been performed on UHV epitaxially grown tetracene thin films on H/Si(001)-2x1 substrates. The in-plane lattices of the crystalline films were characterized by 2D reciprocal space imaging of the in-plane (11), (12) and (20) GIXD diffraction spots and the out-place lattices were characterized by the wide angle Bragg diffraction. The thickness of the tetracene films ranged from 1.2 monolayer (ML) to 15 ML. H/Si(001)-2x1 substrates with different surface roughness were used. The results indicate that the film structure characteristics are strongly influenced by the substrate conditions and under favorable conditions the homogeneous thin-film phase could dominate the growth up to about 8 ML. The implications of the results to the growth mechanisms and to thin film electronics applications will be discussed.