Title: Versatile Large-Area Custom-Feature van der Waals Epitaxy of Topological Insulators,
Abstract: As the focus of applied research in topological insulators (TI) evolves, the
need to synthesize large-area TI films for practical device applications takes
center stage. However, constructing scalable and adaptable processes for
high-quality TI compounds remains a challenge. To this end, a versatile van der
Waals epitaxy (vdWE) process for custom-feature Bismuth Telluro-Sulfide TI
growth and fabrication is presented, achieved through selective-area
fluorination and modification of surface free-energy on mica. The TI features
grow epitaxially in large single-crystal trigonal domains, exhibiting armchair
or zigzag crystalline edges highly oriented with the underlying mica lattice
and only two preferred domain orientations mirrored at $180^\circ$. As-grown
feature thickness dependence on lateral dimensions and denuded zones at
boundaries are observed, as explained by a semi-empirical two-species surface
migration model with robust estimates of growth parameters and elucidating the
role of selective-area surface modification. Topological surface states
contribute up to 60% of device conductance at room-temperature, indicating
excellent electronic quality. High-yield microfabrication and the adaptable
vdWE growth mechanism with readily alterable precursor and substrate
combinations, lend the process versatility to realize crystalline TI synthesis
in arbitrary shapes and arrays suitable for facile integration with processes
ranging from rapid prototyping to scalable manufacturing.