Charge Manipulation in Silicon Atomic Quantum Dots for Nano-Electronic Computing Architectures

J.L. Pitters, L. Livadaru, M.B. Haider, M. Taucer, R.A. Wolkow
National Research Council of Canada, CA

Keywords: silicon, atomic, quantum dot, scanning tunneling microscopy, QCA

Summary:

Coupled quantum dots form an attractive basis both for fundamental studies of single electron control and as potential building blocks for future nano-electronic devices. One computing scheme, Quantum-dot Cellular Automata (QCA), is based upon “cells” of tunnel coupled quantum dots and electrostatic interactions between adjacent cells to transmit binary information and perform calculations with minuscule power consumption. We have demonstrated a new approach using the scanning tunneling microscope (STM) at room temperature. We show that the silicon atom dangling bond (DB) state, on an otherwise hydrogen terminated surface, serves as a quantum dot. These atomic quantum dots can be assembled into multi-DB ensembles through precise hydrogen atom removal using the STM tip. Assembly at critical distances (1-2 nm) leads to electron tunnel coupling between quantum dots. Control over the net electron occupation of quantum dot structures is also demonstrated. Additionally, it is shown that pairs of tunnel-coupled DBs can be switched, using electrostatic control, from a symmetric bi-stable state to one exhibiting an asymmetric electron occupation. Similarly, the setting of an antipodal state in a square assembly of four DBs is achieved, demonstrating at room temperature, the essential building block of a QCA device.