Highly Sensitive Ammonia Gas Detection at Room Temperature by Integratable Silicon Nanowire Field-Effect Sensors

Toxic gas monitoring at room temperature (RT) is of great concern to public health and safety, where ultrathin silicon nanowires (SiNWs), with diameter <80 nm, are ideal one-dimensional candidates to achieve high-performance field-effect sensing. However, a precise integration of the tiny SiNWs as active gas sensor channels has not been possible except for the use of expensive and inefficient electron beam lithography and etching. In this work, we demonstrate an integratable fabrication of field-effect sensors based on orderly SiNW arrays, produced via step-guided in-plane solid-liquid-solid growth. The back-gated SiNW sensors can be tuned into suitable subthreshold detection regime to achieve an outstanding field-effect sensitivity (75.8% @ 100 ppm NH₃), low detection limit (100 ppb), and excellent selectivity to NH₃ gas at RT, with fast response/recovery time scales (T_res/T_rec) of 20 s (at 100 ppb NH₃) and excellent repeatability and high stability over 180 days. These outstanding sensing performances can be attributed to the fast charge transfer between adsorbed NH₃ molecules and the exposed SiNW channels, indicating a convenient strategy to fabricate and deploy high-performance gas detectors that are widely needed in the booming marketplace of wearable or portable electronics.