Alignment nature of ZnO nanowires grown on polished and nanoscale etched lithium niobate surface through self-seeding thermal evaporation method

Highlights: • ZnO nanowires were grown directly on LiNbO₃ surface for the first time by thermal evaporation. • Self-alignment of the nanowires due to step bunching of LiNbO₃ surface is observed. • Increased roughness in surface defects promoted well-aligned growth of nanowires. • Well-aligned growth was then replicated in 50 nm deep trenches on the surface. • Study opens novel pathway for patterned growth of ZnO nanowires on LiNbO₃ surface. - Abstract: High aspect ratio catalyst-free ZnO nanowires were directly synthesized on lithium niobate substrate for the first time through thermal evaporation method without the use of a buffer layer or the conventional pre-deposited ZnO seed layer. As-grown ZnO nanowires exhibited a crisscross aligned growth pattern due to step bunching of the polished lithium niobate surface during the nanowire growth process. On the contrary, scratches on the surface and edges of the substrate produced well-aligned ZnO nanowires in these defect regions due to high surface roughness. Thus, the crisscross aligned nature of high aspect ratio nanowire growth on the lithium niobate surface can be changed to well-aligned growth through controlled etching of the surface, which is further verified through reactive-ion etching of lithium niobate. The investigations and discussion in the present work will provide novel pathway for self-seeded patterned growth of well-aligned ZnO nanowires on lithium niobate based micro devices