Advanced Nanoelectronic Devices Based on Carbon Nanotubes for Future Electronics.

Over the last few decades, complementary metal-oxide-semiconductor (CMOS) devices have been the driving force behind most of the technological advancements, particularly in IT and computing, which has driven the knowledge economy. Computers are not only becoming smaller, faster and cheaper, but have also become more ubiquitous in the form of embedded systems. As these systems become increasingly complex and smaller, its building blocks, which are transistors, are shrinking to increase operational speeds and density of devices. Aggressive scaling has pushed CMOS technology to its limit and therefore new material systems are needed to ensure the continuity of Moore’s Law. A material system enables the extension of Moore’s Law is single walled carbon nanotubes (SWCNTs) that are not only smaller, but also display superior intrinsic electronic properties. SWCNTs are synthesised heterogeneously, consisting of metallic and semiconducting tubes with varying band gaps. Whilst it may provide a useful material for tuneable devices, SWCNTs’ heterogeneity is a major problem with regards to fabrication and compatibility with current CMOS technology. Furthermore, the transport properties of SWCNT based devices are yet to be fully understood. This work assesses the application of SWCNTs as an active channel in carbon nanotube field effect transistors (CNTFETs). SWCNTs from different sources were characterised and separated based on electronic type. Optimisation of the separation process has demonstrated improved separation purity levels close to 100%. Devices fabricated from separated SWCNTs showed superior switching performance in terms of low off state currents (~10-13A) and high on-off ratio (~106). The device parameters were also shown to be dependent on the SWCNT source, hence the synthesis technique of the respective SWCNT sources. Finally, the current transport mechanism of the CNTFETs was studied based on varying atmospheric conditions and SWCNT properties. Measurements at low temperature reveal two fundemental current transport features i.e. multimode transport and conductance spikes, shown to be the inherent properties of the SWCNTs