Faculty Publications
Measuring Charge Trap Occupation and Energy Level in CdSe/ZnS Quantum Dots Using a Scanning Tunneling Microscope
Document Type
Article
Journal/Book/Conference Title
Physical Review B - Condensed Matter and Materials Physics
Volume
81
Issue
11
Abstract
We 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 ∼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. © 2010 The American Physical Society.
Department
Department of Physics
Original Publication Date
3-22-2010
DOI of published version
10.1103/PhysRevB.81.115439
Recommended Citation
Stollenwerk, Andrew; Hummon, M. R.; Narayanamurti, V.; Anikeeva, P. O.; Panzer, M. J.; Wood, V.; and Bulović, V., "Measuring Charge Trap Occupation and Energy Level in CdSe/ZnS Quantum Dots Using a Scanning Tunneling Microscope" (2010). Faculty Publications. 6054.
https://scholarworks.uni.edu/facpub/6054
