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)-2×1 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.

Visualization of molecular packing and tilting domains and interface effects in tetracene thin films on H/Si(001)

“…a). These islands appear to have an elongated shape along substrate lattice orientations, consistent with our previous work: the film is commensurate with the substrate lattice along the a ‐axis (the longer base vector of the ab ‐plane unit cell of the film) . AFM imaging of a smaller area on the same film is shown in Fig.…”

“…a). In other words, if the surface islands preferentially grow along the a ‐axis due to kinetics in growth, then the subdomains would tend to elongate along the b ‐axis (which is perpendicular to the a ‐axis in the film ). On the other hand, substrates were chosen to have step anisotropy in this study (i.e., with a specific miscut angle).…”

“…We observe that there is a coverage‐dependent structure phase transition for the film (i.e., the initial film is rather disordered in molecule‐tilting and significant bulk‐like crystallization happens from ∼3 ML) ; and that the lowest measurable mobility in tetracene film FETs occurs at ∼3 ML coverage . Our grazing‐incidence X‐ray diffraction (GIXD) data show that the film lattice is commensurate with the substrate lattice along the longer base vector of the ab ‐plane unit cell (i.e., the a ‐direction), and incommensurate along the b ‐direction (which is perpendicular to the a ‐direction here). The tetracene films are thus considered partially commensurate with the substrate lattice , different from the common epitaxy categories defined in Ref.…”

“…Our grazing‐incidence X‐ray diffraction (GIXD) data show that the film lattice is commensurate with the substrate lattice along the longer base vector of the ab ‐plane unit cell (i.e., the a ‐direction), and incommensurate along the b ‐direction (which is perpendicular to the a ‐direction here). The tetracene films are thus considered partially commensurate with the substrate lattice , different from the common epitaxy categories defined in Ref. .…”

Investigating crystal microstructure of niobium materials by an x-ray diffraction reciprocal space mapping technique

“…Outside the SRF community, in scientific research of semiconductors [12][13][14][15][16], macromolecular crystal proteins [2], and optic electronics [17], the x-ray diffraction reciprocal space mapping technique (XRD RSM) has been widely utilized, for example, to measure the structural properties of epitaxial films, or to reveal film composition, layer tilting, lattice relaxation, and crystal quality. Such RSM plots could demonstrate the strain, relaxation, and misorientation of a thin film on a substrate.…”