A near single crystalline TiO₂ nanohelix array: Enhanced gas sensing performance and its application as a monolithically integrated electronic nose

We present high performance gas sensors based on an array of near single crystalline TiO₂ nanohelices fabricated by rotating oblique angle deposition (OAD). The combination of large surface-to-volume ratio, extremely small size (<30 nm) comparable to the Debye length, a near single crystallinity of TiO₂ nanohelices, together with the unique top-and-bottom electrode configuration hugely improves the H₂-sensing performance, including ∼10 times higher response at 50 ppm, approximately a factor of 5 lower detection limit, and much faster response time than the conventional TiO₂ thin film devices. Beyond such remarkable performance enhancement, the excellent compatibility of the OAD method compared with the conventional micro-fabrication technology opens a new avenue for monolithic integration of high-performance chemoresistive sensors to fabricate a simple, low cost, reliable, yet fully functional electronic nose and multi-functional smart chips for in situ environmental monitoring.