SnO2-SiO2 1D Core-Shell Nanowires Heterostructures for Selective Hydrogen Sensing

SnO2 is one of the most employed n-type semiconducting metal oxide in chemo-resistive gas-sensing although it presents serious limitations due to a low selectivity. Herein, the authors introduce 1D SnO2-SiO2 core-shell nanowires (CSNWs). The amorphous SiO2-shell layer with varying thicknesses (1.8–10.5 nm) is grown onto the SnO2 nanowires (NWs) by atomic layer deposition (ALD). SiO2-coated SnO2 CSNWs show a dramatic improvement of the selectivity towards hydrogen. Moreover, the sensing-response is strongly correlated to the thickness of the SiO2-shell and the working temperature. The SnO2-SiO2 CSNWs sensor with a 4.8-nm SiO2 shell thickness exhibits the best selectivity and sensitivity, having ca. 7-fold higher response toward hydrogen compared to bare-SnO2 NWs. The selectivity and enhanced sensing-response are related to the masking effect of the SiO2 shell and an increase in the width of the electron-depletion-layer due to a strong electronic coupling between the SnO2 core and SiO2 coating, respectively.