Single Dopant Lithography for the Fabrication of Atomic-scale Devices and Quantum Systems

We describe approaches for the fabrication of single atom electronic devices and of devices with spin-based qubits for quantum computing. Single ion implantation is one of the main candidates for fabricating atomic-scale devices. Here, the ability to precisely locate single dopant atoms has the potential to enable deterministic, tunable control over key electronic and magneto-optical properties of the basic devices necessary for solid-state quantum computing. Further, the electrical operation of a CMOS compatible single dopant atom device operating at room-temperature (RT) is presented. It is based on a single dopant atom quantum dot (QD) transistor using phosphorous atoms isolated within nanoscale SiO
2
tunnel barriers. In contrast to single dopant transistors in silicon, where the QD potential well is shallow and device operation limited to ~1 K temperatures, here, a deep (~1eV) potential well allows electron confinement even at RT [1]. This suggests higher temperature operation, at ~10 K or greater if needed, for quantum electronic circuits. The transistors, based on ~10 nm size scale Si/SiO2/Si point-contact tunnel junctions defined by scanning probe lithography and ‘geometric oxidation’ of the point-contact region, have enabled the control of single [1], and double tunnel coupled QDs [2], and investigations of single particle thermodynamics in a Maxwell ‘demon’ configuration [3].