In-plane Epitaxy of Bi₂S₃ Nanowire Arrays for Ultrasensitive NIR Photodetectors

The direct growth of semiconductor nanowire (NW) arrays horizontally aligned on a substrate is critically important for the applications of NWs in electronic or optoelectronic devices at the circuit level. The strict requirement of lattice matching between a substrate and a material in the covalent epitaxy of crystals makes the wire arrays be grown on the substrates only with similar lattice parameters. Herein, a van der Waals epitaxy route is developed to realize the in-plane growth of large-scale Bi₂S₃ NW arrays on mica with a large lattice mismatch. The orthorhombic Bi₂S₃ NWs grow epitaxially with the axial direction of (Formula presented.) along the six symmetric directions of the mica. Transmission electron microscope measurements show that the epitaxial relationships are (Formula presented.) and (Formula presented.) along the length and width directions of the wires, respectively. More importantly, photodetectors based on Bi₂S₃ NWs show a wide photoresponse spectrum range from 500 to 980 nm. A high responsivity (5233 A W⁻¹) and a specific detectivity (1.8 × 10¹² Jones) are achieved under 830 nm light irradiation with ultralow intensity (64 nW cm⁻²). In addition, the photodetectors exhibit high stability with at least 48 day storage in ambient atmosphere or with 1000 times bending.