Development of Carbon Nanotube based Josephson Junctions using Superconducting Electrodes

We propose to develop manifold carbon nanotube Josephson junction using superconducting electrodes made of Niobium-Nb. Advances in nanofabrication techniques have made it possible to make devices in which superconducting electrodes are connected to non-superconducting nanostructures such as quantum dots. The properties of these hybrid devices result from a combination of a macroscopic quantum phenomenon involving large numbers of electrons (superconductivity) and the ability to control single electrons, offered by quantum dots. Here in this project we will develop CNTs-based Josephson junction using CNT's self-assembly process. First by controlling the wettability of the Si/SiO2 substrate bundle of CNTs will be assembled on Si/SiO2 substrate at required locations (of micron scale) in specific geometries. After successful assembly of CNTs superconducting Nb contacts will be deposited across the assembled CNTs using conventional microfabrication process. In these Josephson junctions we will study how the separation between superconducting Nb junction and density of CNTs effect the performance of the junction, like critical current. Furthermore, at the end of the project we will try to reduce the dimension of CNTs region to nano scale. In this last step, to assemble CNTs we will create wettable and non-wettable regions using e-beam lithography and will try to assembled CNTs in 10's of nm dimension. This work is a first step towards realizing the fabrication and characterization of Josephson junction locally within the kingdom. The outcome of this research promises to impact different well known applications of these junctions such as superconducting transistors, superconducting quantum interference devices (SQUIDs), being promising candidates for the detection of individual magnetic molecules. In addition, multiple junction fabrication in parallel using conventional micro/nano fabrication processes may help to fabricate such devices at commercial scale in future. Our proposal involves fabricating a CNT based Josephson junction using the self-aligned technique pioneered by Dr. Rao. The device will be fabricated in CENT in collaboration with KAUST. All the fabricated devices will be tested by Dr. Harrabi, in his existing low temperature facility in department of Physics, KFUPM. In future, successful tested Josephson junction can be further investigated in state of the art labs of our collaborators at Quantum Nanoelectronics Lab - QNL at University of California, Berkeley, USA.