High-performance ethanol sensor based on In₂O₃ nanospheres grown on silicon nanoporous pillar array

At the interfaces between different materials, electronic systems with unusual electronic properties can be generated. Here, we report an In₂O₃/Si nanoheterostructures prepared by depositing indium grain film on silicon nanoporous pillar array (Si-NPA) by a vacuum thermal evaporation technique and a following thermal oxidation method. The composition and morphology of In₂O₃ film on Si-NPA were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), which disclosed that the In₂O₃ film is composed of a layer of In₂O₃ nanospheres with massive interfaces coating on Si-NPA. The sensor based on In₂O₃/Si-NPA showed high selectivity to ethanol, and demonstrated a high response of 3.38 at the extremely low ethanol gas concentration of 2 ppm. The response and recovery times to 100 ppm were 3 s and 39 s, respectively. The high performance was attributed to the specific nanostructure feature of In₂O₃/Si-NPA sensor, large specific surface area and massive surface active sites. Moreover, the impressive features of In₂O₃/Si-NPA heterostructures have been discussed in detail from its geometrical and band structure. These results observed here indicate that the In₂O₃/Si-NPA sensor may be a promising sensing candidate for detecting low-concentration ethanol.