EXTERNAL CHARGE-STATE DETECTION OF A DOUBLE-DOT SYSTEM

We report direct measurements of the charging diagram of a nanoscale s eries double-dot system at low temperatures. Our device consists of tw o metal dots in series, with each dot capacitively coupled to another single dot serving as an electrometer. This configuration allows us to externally detect all possible charge transitions within a double-dot system. In particular, we show that transfer of an electron between t wo dots, representing a polarization switch of the double dot, can be most prominently detected by our differential sensing scheme. We also perform theoretical calculations of the device characteristics and fin d excellent agreement with experiment. We discuss possible application s as an output stage for quantum-dot cellular automata architecture. ( C) 1997 American Institute of Physics.