Study of Single Silicon Quantum Dots’ Band Gap and Single-Electron Charging Energies by Room Temperature Scanning Tunneling Microscopy

Individual molecules at the edges of self-assembled islands grown on Ag(111) can be deliberately switched in their charge state with the electric field from a scanning-probe tip. Close to the threshold voltage for a charge state transition, periodic switching of the charge is directly driven by the cantilever motion in frequency-modulated atomic force microscopy (AFM), as can be deduced from the signature in the measured frequency shift. In this regime, the integrated frequency shift yields the tip-sample force that is due to a single additional electron. Further, the signature of the dynamic charging response provides information on the electronic coupling of the molecule to the substrate. In analogy to previous experiments on quantum dots, this may also be used in the future to access excited state properties of single molecules from AFM experiments.

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“…of the charge state in atoms, 7-9 molecules, [10][11][12][13] and quantum dots 14,15 has been demonstrated.…”

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confidence: 95%

Periodic Charging of Individual Molecules Coupled to the Motion of an Atomic Force Microscopy Tip

et al. 2015

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“…There is a measurement with scanning tunneling spectroscopy for the band gap of Si QDs [13]. From the experiment, a curve of QD-size dependence of the band gap was obtained, and the fitting formula was given as 1.136 + 9.75/D 2 (eV), where D was the diameter of a QD in nanometers [13].…”

Section: Resultsmentioning

confidence: 99%

“…From the experiment, a curve of QD-size dependence of the band gap was obtained, and the fitting formula was given as 1.136 + 9.75/D 2 (eV), where D was the diameter of a QD in nanometers [13]. The experimental curve is also shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Large-Scale First-Principles Electronic Structure Calculations for Nano-Meter Size Si Quantum Dots

Iwata

Oshiyama

Shiraishi

2010

e-J. Surf. Sci. Nanotechnol.

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We have studied the system size dependence of the density of states, band gap, and the charging energy of the large size Si quantum dots of 2.2 to 7.6 nm diameters by first-principles electronic structure calculations. The largest model examined in this study consists of over 10,000 Si atoms, and we performed such large calculations by using recently developed real-space density-functional theory code suitable for massively parallel computers. The density of states of 6 nm-diameter Si quantum dot is almost the same as that of the bulk Si. The band gaps of the Si quantum dots have been calculated by the ∆SCF method with local-density approximation, and we have found that the difference between the ∆SCF band gap and the Kohn-Sham eigenvalue gap is equal to the inverse of the dot radius. Consequently the ∆SCF band gap converges to the Kohn-Sham eigenvalue gap in the infinitely large size limit with the local-density approximation.

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“…66 Similarly to the crystalline case, HOMO and LUMO states of amorphous systems are localized at the surface of the QD and inside it, respectively.…”

Section: Sio 2 Matrices and Siqdsmentioning

confidence: 99%

“…The dI/dV curve is usually employed experimentally to extract the single-particle energy spectrum of the QD, 5,66,82 since a peak in dI/dV appears whenever an energy level of the QD is aligned with the electrochemical potential of one of the electrodes. Therefore, the possibility of theoretically predicting the dI/dV curve from our calculations opens the possibility of accurately describing the transport in these kinds of complex systems 83 and of reducing its related instabilities, such as the current temporal self-oscillation in superlattices.…”

Section: B Description Of I-v Characteristicsmentioning

confidence: 99%

Silicon quantum dots embedded in a SiO2matrix: From structural study to carrier transport properties

et al. 2013

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We study the details of electronic transport related to the atomistic structure of silicon quantum dots embedded in a silicon dioxide matrix using ab initio calculations of the density of states. Several structural and composition features of quantum dots (QDs), such as diameter and amorphization level, are studied and correlated with transport under transfer Hamiltonian formalism. The current is strongly dependent on the QD density of states and on the conduction gap, both dependent on the dot diameter. In particular, as size increases, the available states inside the QD increase, while the QD band gap decreases due to relaxation of quantum confinement. Both effects contribute to increasing the current with the dot size. Besides, valence band offset between the band edges of the QD and the silica, and conduction band offset in a minor grade, increases with the QD diameter up to the theoretical value corresponding to planar heterostructures, thus decreasing the tunneling transmission probability and hence the total current. We discuss the influence of these parameters on electron and hole transport, evidencing a correlation between the electron (hole) barrier value and the electron (hole) current, and obtaining a general enhancement of the electron (hole) transport for larger (smaller) QD. Finally, we show that crystalline and amorphous structures exhibit enhanced probability of hole and electron current, respectively.

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Study of Single Silicon Quantum Dots’ Band Gap and Single-Electron Charging Energies by Room Temperature Scanning Tunneling Microscopy

Cited by 43 publications

References 28 publications

Periodic Charging of Individual Molecules Coupled to the Motion of an Atomic Force Microscopy Tip

Periodic Charging of Individual Molecules Coupled to the Motion of an Atomic Force Microscopy Tip

Large-Scale First-Principles Electronic Structure Calculations for Nano-Meter Size Si Quantum Dots

Silicon quantum dots embedded in a SiO2matrix: From structural study to carrier transport properties

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