Ultra-Flexible Vacuum Ultraviolet Photodetector Based on Hexagonal Boron Nitride Films Grown by LPCVD

Abstract

An ultra-flexible vacuum ultraviolet (VUV) photodetector based on high-crystalline hexagonal boron nitride (hBN) films via low-pressure chemical vapor deposition (LPCVD) is demonstrated. The 1 cm × 1 cm continuous hBN films were synthesized on a sapphire substrate at 1400 °C, exhibiting a wide optical bandgap of 5.97 eV and excellent surface flatness. Flexible photodetectors fabricated on the transferred films exhibited a low dark current of 2.5 pA and a photocurrent of 164 pA at 185 nm, and the rise time and the decay time are 0.47 and 0.50 s, respectively. The bending stability of the device was assessed by measuring its photoelectric response across bending angles from 0° (flat) to 180° (fully folded). This is the first report of a flexible photodetector that sustains 180° folding under extreme ultraviolet (185 nm) without failure. The device maintained consistent photoresponse even in the fully folded state, demonstrating outstanding mechanical flexibility and structural durability. Finite-element analysis using the COMSOL solid mechanics module further revealed the stress-release mechanism within the layered film, providing a mechanistic understanding of the observed bendability. These results highlight that the combination of LPCVD growth hBN and self-peeling transfer technology offers great potential for fabricating ultra-flexible VUV photodetectors, offering great potential for wearable sensing, flexible imaging, and next-generation bendable optoelectronic systems.