Substrate Morphology Directs (001) Sb₂Se₃ Thin Film Growth by Crystallographic Orientation Filtering

Antimony chalcogenide, Sb₂X₃ (X = S, Se), applications greatly benefit from efficient charge transport along covalently bonded (001) oriented (Sb₄X₆)_n ribbons, making thin film orientation control highly desirable - although particularly hard to achieve experimentally. Here, it is shown for the first time that substrate nanostructure plays a key role in driving the growth of (001) oriented antimony chalcogenide thin films. Vapor Transport Deposition of Sb₂Se₃ thin films is conducted on ZnO substrates whose morphology is tuned between highly nanostructured and flat. The extent of Sb₂Se₃ (001) orientation is directly correlated to the degree of substrate nanostructure. These data showcase that nanostructuring a substrate is an effective tool to control the orientation and morphology of Sb₂Se₃ films. The optimized samples demonstrate high (001) crystallographic orientation. A growth mechanism for these films is proposed, wherein the substrate physically restricts the development of undesirable crystallographic orientations. It is shown that the surface chemistry of the nanostructured substrates can be altered and still drive the growth of (001) Sb₂Se₃ thin films - not limiting this phenomenon to a particular substrate type. Insights from this work are expected to guide the rational design of Sb₂X₃ thin film devices and other low-dimensional crystal-structured materials wherein performance is intrinsically linked to morphology and orientation.