Quantum dots on bilayer graphene made on a substrate of boron nitride using split gates

Abstract

In this project a method has been developed to fabricate the device structure for a quantum dot on bilayer graphene made on a boron nitride substrate. Quantum dots in bilayer graphene give us the ability to study the special properties of electrons inside this material; including a gapless electron-hole crossover and a fourfold degeneracy of electrons. The usage of boron nitride as a substrate instead of the usual SiO2 should help us improve the quality of our devices. In the future we hope to create a qubit for quantum information processing with lower decoherence times as compared to conventional dots (e.g. GaAs). Measurements have been performed on an intermediate device in which the graphene. flake was not yet fully surrounded by boron nitride as dielectric. This device used boron nitride as backgate dielectric and silicon oxide for the top gates. These measurements show that it is possible to influence the doping of the graphene with the gates, but we have not yet been able to demonstrate the full functionality of bilayer graphene; such as the opening of a bandgap. This report will describe the method to make the devices (fully using boron nitride as a dielectric), recommendations are given on how to improve the quality and future experiments are discussed.