Impedance Spectroscopy Study of Charge Transfer in the Bulk and Across the Interface in Networked SnO<sub>2</sub>/Ga<sub>2</sub>O<sub>3</sub> Core–Shell Nanobelts in Ambient Air
Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The inf...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2024-09-01
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| Series: | Sensors |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1424-8220/24/19/6173 |
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| Summary: | Metal oxide core–shell fibrous nanostructures are promising gas-sensitive materials for the detection of a wide variety of both reducing and oxidizing gases. In these structures, two dissimilar materials with different work functions are brought into contact to form a coaxial heterojunction. The influence of the shell material on the transportation of the electric charge carriers along these structures is still not very well understood. This is due to homo-, hetero- and metal/semiconductor junctions, which make it difficult to investigate the electric charge transfer using direct current methods. However, in order to improve the gas-sensing properties of these complex structures, it is necessary to first establish a good understanding of the electric charge transfer in ambient air. In this article, we present an impedance spectroscopy study of networked SnO<sub>2</sub>/Ga<sub>2</sub>O<sub>3</sub> core–shell nanobelts in ambient air. Tin dioxide nanobelts were grown directly on interdigitated gold electrodes, using the thermal sublimation method, via the vapor–liquid–solid (VLS) mechanism. Two forms of a gallium oxide shell of varying thickness were prepared via halide vapor-phase epitaxy (HVPE), and the impedance spectra were measured at 189–768 °C. The bulk resistance of the core–shell nanobelts was found to be reduced due to the formation of an electron accumulation layer in the SnO<sub>2</sub> core. At temperatures above 530 °C, the thermal reduction of SnO<sub>2</sub> and the associated decrease in its work function caused electrons to flow from the accumulation layer into the Ga<sub>2</sub>O<sub>3</sub> shell, which resulted in an increase in bulk resistance. The junction resistance of said core–shell nanostructures was comparable to that of SnO<sub>2</sub> nanobelts, as both structures are likely connected through existing SnO<sub>2</sub>/SnO<sub>2</sub> homojunctions comprising thin amorphous layers. |
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| ISSN: | 1424-8220 |