Growth, Characterization, and Application of Vertically Aligned Carbon Nanotubes Using the RF-Magnetron Sputtering...

The aim of this work is to synthesize and characterize a nanostructured material with improved parameters suitable as a chemiresistive gas sensor sensitive to propylene glycol vapor (PGV). Thus, we demonstrate a simple and cost-effective technology to grow vertically aligned carbon nanotubes (CNTs) and fabricate a PGV sensor based on Fe₂O₃:ZnO/CNT material using the radio frequency magnetron sputtering method. The presence of vertically aligned carbon nanotubes on the Si(100) substrate was confirmed by scanning electron microscopy and Fourier transform infrared (FTIR), Raman, and energy-dispersive X-ray spectroscopies. The uniform distribution of elements in both CNTs and Fe₂O₃:ZnO materials was revealed by e-mapped images. The hexagonal shape of the ZnO material in the Fe₂O₃:ZnO structure and the interplanar spacing in the crystals were clearly visible by transmission electron microscopy images. The gas-sensing behavior of the Fe₂O₃:ZnO/CNT sensor toward PGV was investigated in the temperature range of 25-300 °C with and without ultraviolet (UV) irradiation. The sensor showed clear and repeatable response/recovery characteristics in the PGV range of 1.5-140 ppm, sufficient linearity of response/concentration dependence, and high selectivity both at 200 and 250 °C without UV radiation. This is a basis for concluding that the synthesized Fe₂O₃:ZnO/CNT structure is the best candidate for use in PGV sensors, which will allow its further successful application in real-life sensor systems.