Abstract
In this work, we fabricated three carbon nanoplume structured samples under different temperatures using a simple hot filament physical vapor deposition (HFPVD) process, and investigated the role of surface morphology, defects, and graphitic content on relative humidity (RH) sensing performances. The Van der Drift growth model and oblique angle deposition (OAD) technique of growing a large area of uniformly aligned and inclined oblique arrays of carbon nanoplumes (CNPs) on a catalyst-free silicon substrate was demonstrated. The optimal growing temperature of 800 °C was suitable for the formation of nanoplumes with larger surface area, more defect sites, and less graphitic content, compared to the other samples that were prepared. As expected, a low detection limit, high response, capability of reversible behavior, and rapid response/recovery speed with respect to RH variation, was achieved without additional surface modification or chemical functionalization. The holes’ depletion has been described as a RH sensing mechanism that leads to the increase of the conduction of the CNPs with increasing RH levels.
Highlights
The detection and control of humidity are important considerations for different applications including food quality monitoring, meteorology and medical equipment functioning
The oblique angle deposition (OAD) technique is regarded as an effective method to generate porous one-dimensional nanostructures, a result of the self-shadowing nature of the deposition process [9], which possesses an extremely high surface area and is an important factor for gas sensing applications
The originality of this work involves providing a comparison of the sensor response of carbon nanostructures synthesized at different temperatures with a simple OAD technique by hot filament physical vapor deposition (HFPVD)
Summary
The detection and control of humidity are important considerations for different applications including food quality monitoring, meteorology and medical equipment functioning. The morphological features and structure include: surface area, graphitic contents [5], number of conducting electrons [6], defects within nanostructures [7], and surface functionalities [8] which all play important roles in the carbon-based sensor response. It was reported that water vapor is chemisorbed on the surface of the semiconductor sensing materials, and leads to the formation of the hydroxyl group on the surface [11] and proton transfer occurs following Grotthuss’s chain reaction [10]. The originality of this work involves providing a comparison of the sensor response of carbon nanostructures synthesized at different temperatures with a simple OAD technique by hot filament physical vapor deposition (HFPVD). The results indicate that the carbon nanostructures demonstrate excellent performance as RH sensors under different RH ranges
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