Investigation of single walled carbon nanotube alignment on gas sensors

• Main Author: Lee, Zhirong.
• Other Authors: Alfred Tok Iing Yoong
• Format: Final Year Project
• Language: English
• Published: 2011
• Subjects: DRNTU::Engineering::Materials::Nanostructured materials
• Online Access: http://hdl.handle.net/10356/43932
• Institution: Nanyang Technological University

Carbon nanotubes (CNTs) gas sensors have garnered intensive interest from researchers due to the demand for a highly sensitive and stable sensor for industry, biomedicine, military, and so forth. The underlying mechanisms in sensing however remain controversial, which obstruct the full potential of these promising nanosensors. In this work, the effects of alignment between aligned and network, density and resistor/transistor platforms that CNTs can grow on will be investigated. Chemical vapour deposition (CVD) is used to grow CNTs on quartz or silicon nitrite substrates while sputtering was done to fabricate gold electrodes. Characterization is done using Field-Effect Scanning Electron Microscopy (FESEM) to observe the surface topology in order to determine the distribution and alignments of the CNTs. Furthermore, Atomic Force Microscopy (AFM) and Raman spectroscopy are used to measure the diameters of the nanotubes. Gas sensing procedures are carried out using Keithley 4200 probe station to determine the drain current (ID) – gate voltage (VD) graph and ID – time graph while they are exposed to NO and N¬2 gases. Their responses were then tabulated and the results showed that alignment of CNTs is vital in sensitivity. Furthermore higher density CNTs displayed higher sensitivity while transistor platforms showed better sensitivities than resistor platforms. At the moment, it is very hard to fabricate fully aligned CNTs transistor, therefore future works are necessary to develop a new technique to be able produce it at a consistent basis.