Due to the fundamental nature of this study, these findings are important for the development of next generation gas sensing devices. On the other hand, the CNT-pMOS-nMOS and CNT-nMOS-pMOS CSHS show sensing responses, which in certain cases are governed by the heterojunctions between nMOS and pMOS and strongly depends on the thickness of the MOS layers. The CNT-n,pMOS CSHS exhibit response related to the n,pMOS-shell layer. NiO and SnO2 are selected as representative p- and n-type MOS, respectively, and the response of a set of samples is studied toward hydrogen considered as model analyte. The carbon nanotubes are here used as highly conductive substrates permitting operation of the devices at relatively low temperature and are not involved in the sensing response. Here, we introduce a series of prototypes CNT-nMOS, CNT-pMOS, CNT-pMOS-nMOS, and CNT-nMOS-pMOS hierarchical core-shell heterostructures (CSHS) permitting us to directly relate the sensing response to the MOS shell or to the p-n heterojunction. A better understanding of the sensing response of heterostructured nanomaterials requires the engineering of heterojunctions with well-defined core and shell layers. Since their importance in real applications, a thorough understanding of the transduction mechanism is vital, whether it is related to a heterojunction or simply to the shell and core materials. Heterostructures made from metal oxide semiconductors (MOS) are fundamental for the development of high-performance gas sensors. The selectivity and response of SnO2 sensors are greatly enhanced by a conformal and homogeneous SiO2 coating of a calibrated thickness. The gas‐sensing properties and the underlying transduction mechanism of well‐defined SnO2‐SiO2 core‐shell nanowires heterostructures with varying thickness of the amorphous SiO2‐shell layer (1.8–10.5 nm in thickness) are presented. 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. 7‐fold higher response toward hydrogen compared to bare‐SnO2 NWs. The SnO2‐SiO2 CSNWs sensor with a 4.8‐nm SiO2 shell thickness exhibits the best selectivity and sensitivity, having ca. Moreover, the sensing‐response is strongly correlated to the thickness of the SiO2‐shell and the working temperature. SiO2‐coated SnO2 CSNWs show a dramatic improvement of the selectivity towards hydrogen. 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). Herein, the authors introduce 1D SnO2‐SiO2 core‐shell nanowires (CSNWs). 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.
0 kommentar(er)
