Internal atomic structure of terbium silicide nanowires on Si(001) capped by silicon

•Atomic structure of terbium silicide nanowires grown on Si(001) capped by silicon.•Scanning tunneling microscopy plus high-resolution transmission electron microscopy.•Room temperature capping by amorphous silicon preserves the nanowire structure.•Capping at elevated temperatures results in strong shape transitions.•Nanowires can consist of hexagonal or tetragonal TbSi2. [Display omitted] In a combined scanning tunneling microscopy and high-resolution transmission electron microscopy study, the internal atomic structure of terbium silicide nanowires on Si(001) capped with silicon is determined. Room temperature capping by amorphous silicon preserves the original nanowire structure, and the nanowires with a usual height of two silicide layers are found to consist of hexagonal TbSi2 with the c-axis in nanowire direction, in contrast to previous assumptions. At larger heights, the nanowires are formed from tetragonal TbSi2. Capping at elevated temperatures results in a shape transition towards higher and more compact nanowires consisting of hexagonal or tetragonal TbSi2 and a crystalline silicon overlayer that shows stacking faults and twin boundaries starting at the nanowires.