title: Revealing energy level structure of individual quantum dots by tunneling rate measured by single-electron sensitive electrostatic force spectroscopy.
abstract: We present theoretical and experimental studies of the effect of the density of states of a quantum dot (QD) on the rate of single-electron tunneling that can be directly measured by electrostatic force microscopy (e-EFM) experiments. In e-EFM, the motion of a biased atomic force microscope cantilever tip modulates the charge state of a QD in the Coulomb blockade regime. The charge dynamics of the dot, which is detected through its back-action on the capacitavely coupled cantilever, depends on the tunneling rate of the QD to a back-electrode. The density of states of the QD can therefore be measured through its effect on the energy dependence of tunneling rate. We present experimental data on individual 5 nm colloidal gold nanoparticles that exhibit a near continuous density of state at 77 K. In contrast, our analysis of already published data on self-assembled InAs QDs at 4 K clearly reveals discrete degenerate energy levels.
authors.affiliation: Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A2T8, Canada.
authors.forename: Antoine
authors.initials: A
authors.lastname: Roy-Gobeil
authors.affiliation: Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A2T8, Canada.
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Miyahara
authors.affiliation: Department of Physics, McGill University, 3600 rue University, Montreal, Quebec H3A2T8, Canada.
authors.forename: Peter
authors.initials: P
authors.lastname: Grutter
mesh_terms: D004553:Electric Conductivity; D004579:Electron Transport; D004583:Electrons; D004735:Energy Transfer; D006046:Gold / Q000737:chemistry; D008422:Materials Testing / Q000379:methods*; D053768:Metal Nanoparticles / Q000737:chemistry* / Q000648:ultrastructure; D018625:Microscopy, Atomic Force / Q000379:methods*; D045663:Quantum Dots; D055672:Static Electricity
chemical_list: D006046:Gold
keywords: Coulomb blockade; Quantum dot; atomic force microscopy; nanoparticle; singe-electron tunneling; tunneling spectroscopy