Size dependence in tunneling spectra of PbSe quantum-dot arrays

Abstract

Interdot Coulomb interactions and collective Coulomb blockade were theoretically arguedto be a newly important topic, and experimentally identified in semiconductorquantum dots, formed in the gate confined two-dimensional electron gas system.Developments of cluster science and colloidal synthesis accelerated the studies of electrontransport in colloidal nanocrystal or quantum-dot solids. To study the interdotcoupling, various sizes of two-dimensional arrays of colloidal PbSe quantum dotsare self-assembled on flat gold surfaces for scanning tunneling microscopy andscanning tunneling spectroscopy measurements at both room and liquid-nitrogentemperatures. The tip-to-array, array-to-substrate, and interdot capacitances are evaluatedand the tunneling spectra of quantum-dot arrays are analyzed by the theory ofcollective Coulomb blockade. The current–voltage of PbSe quantum-dot arraysconforms properly to a scaling power law function. In this study, the dependence oftunneling spectra on the sizes (numbers of quantum dots) of arrays is reportedand the capacitive coupling between quantum dots in the arrays is explored.