Detection of Single-Electron Charging in an Individual InAs Quantum Dot by Noncontact Atomic-Force Microscopy

Abstract

Single-electron charging in an individual InAs quantum dot was observed by electrostatic force measurements with an atomic-force microscope (AFM). The resonant frequency shift and the dissipated energy of an oscillating AFM cantilever were measured as a function of the tip-back electrode voltage, and the resulting spectra show distinct jumps when the tip was positioned above the dot. The observed jumps in the frequency shift, with corresponding peaks in dissipation, are attributed to a single-electron tunneling between the dot and the back electrode governed by the Coulomb blockade effect, and are consistent with a model based on the free energy of the system. The observed phenomenon may be regarded as the "force version" of the Coulomb blockade effect.

Probing Charges on the Atomic Scale by Means of Atomic Force Microscopy

“…AFM-based Kelvin probe force spectroscopy (KPFS) [11] provides the local contact potential difference (LCPD) between tip and sample [12][13][14]. As surface charges and dipoles affect the local work function, LCPD is intimately linked to the charge distribution at surfaces [15,16] such that KPFS can be used to determine the charge state of individual atoms [17] and molecules [18], for example. Hence, the use of tip functionalization in KPFS promises the mapping of charge distributions at ultimate resolution and inside molecules, which is key to the understanding of basic processes in many fields, e.g., organic photovoltaics.…”

Charge-state dynamics in electrostatic force spectroscopy

“…Similarly, correlation between the temporal charging and probe dynamics is also manifested by appearance of enhanced signal in the energy dissipation channel [30,31] E diss . It means that energy has to be supplied to the cantilever (or sometimes retrieved from it, if the dissipation is negative) in order to maintain constant amplitude A of the oscillation.…”

“…[30][31][32]), molecules or even single atoms (like Au atoms on NaCl in [33,34]) Such QDs are of considerable interest because of their potential applications in nanoelectronics [35]. Above referenced examples have been indeed successfully probed using KPFM in two seminal papers [30,34], which paved a route towards a new concept of controlling charge on atomic scale. However, the characteristic time scales of this quantum-dot charge-state dynamics can span many orders of magnitude depending on the details of the studied system as well as on the immediate position of the KPFM scanning probe.…”

“…While gating effect of the biased AFM tip was crucial for the explanation of charging in the above quoted experiments on Au atoms or InAs nanostructures [30,33,34,36], our focus in this paper will be on cases where an electron tunneling from the tip has the decisive effect. We should note that the model could be easily adapted to the charge gating processes too, but this is beyond the scope of the paper.…”

Quantum fluctuation of tunneling current in individual Ge quantum dots induced by a single-electron transfer

“…͓DOI: 10.1063/1.2720756͔ Self-assembled quantum dots ͑QDs͒ of group IV semiconductors have drawn much attention on account of their interesting properties such as single-electron charging effects and quantum effects. [1][2][3][4][5][6][7][8][9] Single-electron transfer between QDs, QD-substrates, and QD-nanowires is also an interesting topic not only for its significance in scientific subjects such as quantum transport but also for its application to quantum devices because it strongly links to the origin of quantum noise, [10][11][12][13] which degrades device performance. Statistical researches about the shot noise for QDs have intensively been done.…”