Carbon nanowall-based gas sensors for carbon dioxide gas detection.

Carbon nanowalls (CNWs) have attracted significant attention for gas sensing applications due to their exceptional material properties such as large specific surface area, electric conductivity, nano- and/or micro-porous structure, and high charge carrier mobility. In this work, CNW films were synthesized and used to fabricate gas sensors for carbon dioxide (CO2) gas sensing. The CNW films were synthesized using an inductively-coupled plasma (ICP) plasma-enhanced chemical vapor deposition (PECVD) method and their structural and morphological properties were characterized using Raman spectroscopy and electron microscopy. The obtained CNW films were used to fabricate gas sensors employing interdigitated gold (Au) microelectrodes. The gas sensors were fabricated using both direct synthesis of CNW films on interdigitated Au microelectrodes on quartz and also transferring presynthesized CNW films onto interdigitated Au microelectrodes on glass. The CO2gas-sensing properties of fabricated devices were investigated for different concentrations of CO2gas and temperature-ranges. The sensitivities of fabricated devices were found to have a linear dependence on the concentration of CO2gas and increase with temperature. It was revealed that devices, in which CNW films have a maze-like structure, perform better compared to the ones that have a petal-like structure. A sensitivity value of 1.18% was obtained at 500 ppm CO2concentration and 100 °C device temperature. The CNW-based gas sensors have the potential for the development of easy-to-manufacture and efficient gas sensors for toxic gas monitoring.

Effect of Electron and Proton Irradiation on Structural and Electronic Properties of Carbon Nanowalls.

In this work, a complex experimental study of the effect of electron and proton ionizing radiation on the properties of carbon nanowalls (CNWs) is carried out using various state-of-the-art materials characterization techniques. CNW layers on quartz substrates were exposed to 5 MeV electron and 1.8 MeV proton irradiation with accumulated fluences of 7 × 1013 e/cm2 and 1012 p/cm2, respectively. It is found that depending on the type of irradiation (electron or proton), the morphology and structural properties of CNWs change; in particular, the wall density decreases, and the sp2 hybridization component increases. The morphological and structural changes in turn lead to changes in the electronic, optical, and electrical characteristics of the material, in particular, change in the work function, improvement in optical transmission, an increase in the surface resistance, and a decrease in the specific conductivity of the CNW films. Lastly, this study highlights the potential of CNWs as nanostructured functional materials for novel high-performance radiation-resistant electronic and optoelectronic devices.

Physical properties of carbon nanowalls synthesized by the ICP-PECVD method vs. the growth time.

Investigation of the physical properties of carbon nanowall (CNW) films is carried out in correlation with the growth time. The structural, electronic, optical and electrical properties of CNW films are investigated using electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, ultraviolet photoelectron spectroscopy, UV-Vis spectroscopy, Hall Effect measurement system, Four Point Probing system, and thermoelectric measurements. Shorter growth time results in thinner CNW films with a densely spaced labyrinth structure, while a longer growth time results in thicker CNW films with a petal structure. These changes in morphology further lead to changes in the structural, optical, and electrical properties of the CNW.