Reactive gas assisted depletion layer modification in Fe2O3/LaFeO3 nanostructured heterojunction: An efficient way for room-temperature self-sufficient gas sensing

Integrating materials at the nanostructures to achieve additional functionalities is a key approach for designing modern devices. Here, we have added a thin layer of LaFeO3 (LFO) on vertically aligned Fe2O3 nanorods to form a Fe2O3/LFO heterojunction. This nanorod-structured heterojunction can sense formaldehyde gas (HCHO) at room temperature without any external bias, which is otherwise impossible with Fe2O3- or LFO-based single-layer devices. A change in carrier concentration of the thin layer of LFO in the presence of reactive gases affects the depletion layer of the Fe2O3/LFO heterointerface, leading to a change in current value at zero bias even at room temperature, presenting an alternative approach for self-sufficient gas sensing. The Fe2O3/LFO heterojunction device can effectively sense HCHO without external energy sources, with a response value of 3.5 and a faster recovery time of 2.2 s. Furthermore, an improved selectivity of the HCHO in self-bias mode confirms an energy-efficient approach for rapid gas sensing.