Occurrence of non-equilibrium orthorhombic SnO2 phase and its effect in preferentially grown SnO2 nanowires for CO detection

Abstract

Tin oxide nanowires (NWs) have been successfully deposited on silicon substrates by thermal evaporation of tin powder and used for gas sensing applications. This method has good potential for large-scale fabrication of one dimensional (1D) metal oxide materials. Deposited NWs have been characterized by XRD and FESEM. XRD analysis revealed that SnO₂ NWs exhibit a mixture of orthorhombic and tetragonal phases or single phase tetragonal structure depending on source to substrate distance, and it also plays a vital role on the size and morphology of NWs. The effect of multiphase SnO₂ NWs on CO sensing is studied using an indigenously built sensing setup. The FESEM micrographs reveal that tin oxide NWs of about 50 to 350 nm in diameter can be grown using suitable process parameters like partial O₂ pressure, distance between the substrate and source. CO sensitivity measurements exhibit enhancement in the case of mixed phase SnO₂ NWs as compared to single phase NWs. Texture coefficient is found to have a profound effect on the sensing properties of SnO₂-NWs.