High performance porous LaFeO₃ gas sensor with embedded p-n junctions enabling ppb-level formaldehyde detection

Metal oxides based semiconductors promise high performance gas sensing owing to their robustness and low cost, but are limited by their unsatisfied adsorption ability and intrinsic low carriers' mobility. We herein demonstrate an efficient strategy of reducing the adsorption energy and improving the carrier mobility via bulk implanted TiO₂ nanocrystals (NCs) in LaFeO₃ porous structure. By implanting laser generated sub-3 nm TiO₂ NCs in LaFeO₃ samples, the response value (221.8 for 100 ppm formaldehyde) increases about 4 times comparing with that of pristine. Additionally, the sample exhibits high sensitivity and fast response/recovery speed toward formaldehyde steam. The detailed analyses and theoretical calculation proves that the TiO₂ NCs could cause the increase of adsorbed oxygen levels as well as the carrier mobility through forming the heterojunction with LaFeO₃. This work verifies that TiO₂ NCs implanted LaFeO₃ is a promising formaldehyde sensing material, which provides a new approach to improve sensing ability of metal oxide semiconductor (MOS) based gas sensors.