Atomic transistors

Single-atom and single-molecule transistors control the current flowing between two electrodes separated by a nanogap. This enables the tuning of electronic transport at quantum scale. Accordingly, these transistors are based on quantum point contacts, where the quantum effects on the electronic transport are observed. This work will first review the current state of the art in this domain. The experimental methods commonly used to create single-atom and single-molecule transistors are the mechanical break junction, the electromigration technique and the electrochemical method. We review the theory underlying these devices and the applications of the single-molecule transistors in quantum computing. With a molecule linked to two electrodes, the spin qubit of an atomic nucleus can be controlled to perform quantum computing operations. Then, we studied a spectrometry method that could be useful to characterize such systems: microwave impedance microscopy. This non-invasive, scanning-probe method uses the reflection of a microwave signal by a sample to measure its electronic local properties. We performed finite-element simulations to demonstrate the efficiency of this method with nano-sized samples. We demonstrate the ability to detect gap sizes of the order of the nanometer.