Stray Charge in Quantum-dot Cellular Automata: A Validation of the Intercellular Hartree Approximation

The authors analyze the effect of stray charges near a line of quantum-dot cellular automata (QCA) cells. Considering both the ground-state polarization and the excitation energy of the system, it is determined that there is a 129-nm-wide region surrounding a QCA wire where a stray charge will cause the wire to fail. This calculation is the result of a full-basis-set simulation of a four-cell line. A comparison is made between cells with parallel-spin electrons and those with antiparallel spin electrons, showing that they yield essentially identical results. Therefore, the added complexity of accounting for antiparallel spins does not yield superior simulation results. Finally, a comparison is made between the full-basis calculations and the results of the same calculation using the intercellular Hartree approximation (ICHA). The similarity of these two results demonstrates that the ICHA method is a valid tool for studying the effect of stray charges in larger systems.