We present atomic-scale simulations which compare the characteristics of transistors made of Carbon Nano Tubes (CNT) and Graphene Nano Ribbons (GNR). We studied the properties of a semi-conducting CNT attached to metallic electrodes and controlled by a triple back gate. We find that the performance of the device is weakened by quantum tunneling and show that it is related to inefficient control by the back gate. For the GNR transistor we use a structure comprising of two metallic GNRs separated by a semi-conducting GNR. We find only weak quantum tunneling and show that the GNR has much better transistor characteristics compared to the CNT.  The calculations were performed with the Atomistix ToolKit (ATK) from QuantumWise. ATK is a software package comprising a number of simulation methods for atomic-scale modeling of nano-structures. The ToolKit includes both first principles and semi-empirical methods and use Non Equilibrium Greens Functions (NEGF) to model the nano-structure under an applied bias.

Dr. Kurt Stokbro, born 1965, is an internationally recognized researcher and serial entrepreneur. He is a cofounder and CEO of QuantumWise A/S, and has previously held a professorship at Copenhagen University and positions at Technical University of Denmark. Dr. Stokbro has published more than 60 papers and review articles in international journals, held a large number of lectures as invited speaker and has organised 3 international conferences in nanoscience. The scheme for ab initio calculations of quantum transport, developed by Dr. Stokbro and co-workers, has become the de facto standard for electron transport calculations and has laid the foundation for QuantumWise A/S and Atomistix A/S.