Study Of The Dissociation Mechanism Of Semiconductor Graphene Nanoribbons And The Electrical Properties Of Field Effect Transistors

Integrated circuit chips are the cornerstone of modem information technology development,and about 90%of the devices that make up integrated circuit chips are siliconbased CMOS devices.As Moore’s Law progresses to the 5 nm technology node,silicon-based CMOS devices are approaching their performance limits due to short-channel effect leakage and heat dissipation issues due to size limitations.Scientists have continued to develop devices such as FinFETs in an attempt to minimise the problems caused by the short-channel effect,but with the general trend towards smaller chips with higher performance,the physical limits of silicon-based materials are bound to exist,so we have to replace them with other materials.Several possible alternative materials such as silicon carbide,gallium nitride,gallium oxide and carbon-based materials have played an increasingly important role in the electronics field in recent years,with carbon-based nanomaterials,particularly graphene,considered to be one of the most likely alternatives to silicon due to their excellent optoelectronic properties.One of the most prominent problems with graphene is the zero band gap.Graphene nanoribbons(GNRs)are a very unique carbon-based nanomaterial because they not only retain some of the special properties of graphene,such as high carrier mobility,good thermal conductivity and small size,but also exhibit a limited and tunable band gap when their width is less than 10 nm.Although GNRs have many excellent properties and show great potential for applications in many fields such as displays,batteries,wearable devices,etc.,the preparation of high quality GNRs is still challenging.To address these issues,this thesis proposes a simple method to prepare highperformance graphene nanoribbons with ultra-smooth edges.Firstly we present an easy-tooperate experimental method,which consists of a two-step process:low-intensity oxidation reaction to insert defects and physical-mechanical sonication to shear the sidewalls of singlewalled carbon nanotubes(SWCNTs).The resulting GNRs exhibit excellent semiconductor properties,as they emit sharp and intense photoluminescence at～685 nm,corresponding to a band gap of up to 1.8 eV.Secondly,the principle of shearing the sidewalls of SWCNTs to form GNRs is explained in this paper using molecular dynamics(MD)simulations,and the experimental process is tested by fully atomised reaction kinetic simulations using ReaxFF,the reaction force field of LAMMPS software.The results show that the ultrasonic cavitation effect plays a crucial role in unscrambling the sidewalls of SWCNTs,which successfully unscramble to form GNRs under ultrasonication.Furthermore,GNRs-based field effect transistors(LETs)exhibit high current on/off ratios in excess of 105,and we have built on this to effectively modulate the threshold voltage of GNR FETs with a view to achieving n-type GNR FETs.This simple preparation method is expected to facilitate basic research and practical applications of GNRs.