Abstract
Highly sensitive large-scale tin oxide (SnO2) nanostructures were grown on a glass substrate by thermal evaporation of a mixture of anhydrous tin (II) chloride (SnCl2) and zinc chloride (ZnCl2) powders at 550°C in air. We demonstrate a single cell vapor deposition system to precisely control nanostructural morphology of SnO2 by changing the weight ratio of SnCl2 and ZnCl2 and growth temperature. The morphology and structural property of as-grown nanostructures were characterized using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The SEM images revealed that the SnO2 nanostructures with different densities, sizes, and shapes can be achieved by adjusting the weight ratio of SnCl2 and ZnCl2. A thin film gas sensor based on SnO2 nanostructures with diameter ∼20 nm and length ∼100 nm showed ∼85% sensitivity and 53 seconds of response time, whereas the nanorods with diameter ∼100 nm and length ∼ 1μm showed ∼50% sensitivity with 198 seconds response time. The nanostructured material with small size and shape showed better sensitivity on sensing at room temperature compared to previously reported SnO2 based sensors.
Highlights
With an increase in the advancements in the modern sensing technology, as the numbers of fabrication and manufacturing techniques are innovated, there is an increase in various negative impacts such as an increase in contaminants, harmful gases, and energy consumption
We have fabricated SnO2 nanorod-based gas sensors on glass substrate which demonstrated a performance with ∼85% response with respect the ethanol gas
The preferential growth direction is determined by surface energy, whereas the morphology is determined by the growth kinetics and precursor materials
Summary
With an increase in the advancements in the modern sensing technology, as the numbers of fabrication and manufacturing techniques are innovated, there is an increase in various negative impacts such as an increase in contaminants, harmful gases, and energy consumption. The sensing mechanism in SnO2 is based on the chemisorption reaction that takes place at the surface of the metal oxide, so enhancing surface area of the sensitive materials leads to more sites for adsorption of target gases.[17,18] In most cases, gas sensors are sensitive only at high temperature (above 150◦C) but the operating temperature can be greatly reduced with sensor geometry and with elaborately designing nanostructured sensing materials.[12] The strength of the Vander Walls bond between the material and the gas is the most important factor which determines the operating temperature of the sensors.[9] some volatile organic compounds (such as ethanol and acetone) have a high vapor pressure even at room temperature.
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