Measuring charge trap occupation and energy level in CdSe/ZnS quantum dots using a scanning tunneling microscope
Hummon, M. R.
Stollenwerk, A. J.
Anikeeva, P. O.
Panzer, M. J.
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CitationHummon, M. R., A. J. Stollenwerk, V. Narayanamurti, P. O. Anikeeva, M. J. Panzer, V. Wood, and V. Bulović. 2010. “Measuring Charge Trap Occupation and Energy Level in CdSe/ZnS Quantum Dots Using a Scanning Tunneling Microscope.” Physical Review B 81 (11). https://doi.org/10.1103/physrevb.81.115439.
AbstractWe use a scanning tunneling microscope to probe single-electron charging phenomena in individual CdSe/ZnS (core/shell) quantum dots (QDs) at room temperature. The QDs are deposited on top of a bare Au thin film and form a double-barrier tunnel junction (DBTJ) between the tip, QD, and substrate. Analysis of room-temperature hysteresis in the current-voltage (IV) tunneling spectra, is consistent with trapped charge(s) presenting an additional potential barrier to tunneling, a measure of the Coulomb blockade. The paper describes the first direct electrical measurement of the trap-state energy on individual QDs. Manipulation of the charge occupation of the QD, verified by measuring the charging energy, (61.4 +/- 2.4) meV, and analysis of the DBTJ, show trap states similar to 1.09 eV below the QD conduction-band edge. In addition, the detrapping time, a measure of the tunneling barrier thickness, is determined to have an upper time limit of 250 ms. We hypothesize that the charge is trapped in a quantum-dot surface state.
Citable link to this pagehttp://nrs.harvard.edu/urn-3:HUL.InstRepos:41412215
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