Synthesis of multi-walled carbon nanotubes for NH3 gas detection

Abstract It has been recently demonstrated that carbon nanotubes (CNTs) represent a new type of chemical sensor capable of detecting a small concentration of molecules such as CO, NO 2 , NH 3 . In this work, CNTs were synthesized by chemical vapor deposition (CVD) on the SiO 2 /Si substrate by decomposition of acetylene (C 2 H 2 ) on sputtered Ni catalyst nanoparticles. Their structural properties are studied by atomic force microscopy, high-resolution scanning electron microscopy (HRSEM) and Raman spectroscopy. The CNTs grown at 700 °C exhibit a low dispersion in size, are about 1 μm long and their average diameter varies in the range 25–60 nm as a function of the deposition time. We have shown that their diameter can be reduced either by annealing in oxygen environment or by growing at lower temperature (less than 600 °C). We developed a test device with interdigital Pt electrodes on an Al 2 O 3 substrate in order to evaluate the CNTs-based gas sensor capabilities. We performed room temperature current–voltage measurements for various gas concentrations. The CNT films are found to exhibit a fast response and a high sensitivity to NH 3 gas.