共查询到20条相似文献,搜索用时 407 毫秒
1.
K. D. Osborn Mark W. Keller R. P. Mirin 《Physica E: Low-dimensional Systems and Nanostructures》2004,21(2-4):501
A single-electron transistor (SET) is used to detect tunneling of single electrons into individual InGaAs self-assembled quantum dots (QDs). By using an SET with a small island area and growing QDs with a low density we are able to distinguish and measure three QDs. The bias voltage at which resonant tunneling into the dots occurs can be shifted using a surface gate electrode. From the applied voltages at which we observe electrons tunneling, we are able to measure the electron addition energies of three QDs. 相似文献
2.
The present work shows the presence of inevitable impurities in the semi-insulating GaAs domains when one is developing a single electron transistor (SET) and alters the quantization mechanism of single electron tunneling through the island. It is also indicated that these impurities decrease the amount of energy required to change the number of electrons on the island, which leads to a drastic reduction of SET quality. A theoretical model has been presented for elucidating the I–V characteristics of GaAs nano-crystals. It is found that this proposed model fits well the experimental data. 相似文献
3.
Silly F Pivetta M Ternes M Patthey F Pelz JP Schneider WD 《Physical review letters》2004,92(1):016101
Cerium adatoms, deposited on a Ag(111) surface, are found by low-temperature scanning tunneling microscopy to self-assemble into large ordered hexagonal arrays covering macroscopically the entire surface. We show that the 32 A periodicity of the superlattice is caused by the interaction of surface-state electrons with Ce adatoms and that the large-scale formation of the superlattice is governed by a subtle balance between the sample temperature, the surface diffusion barrier, and the concentration-dependent adatom interaction potential. 相似文献
4.
Vahideh KhademHosseini Daryoosh Dideban MohammadTaghi Ahmadi Razali Ismail 《Brazilian Journal of Physics》2018,48(4):406-410
Single-electron transistors (SETs) are nano devices which can be used in low-power electronic systems. They operate based on coulomb blockade effect. This phenomenon controls single-electron tunneling and it switches the current in SET. On the other hand, co-tunneling process increases leakage current, so it reduces main current and reliability of SET. Due to co-tunneling phenomenon, main characteristics of fullerene SET with multiple islands are modelled in this research. Its performance is compared with silicon SET and consequently, research result reports that fullerene SET has lower leakage current and higher reliability than silicon counterpart. Based on the presented model, lower co-tunneling current is achieved by selection of fullerene as SET island material which leads to smaller value of the leakage current. Moreover, island length and the number of islands can affect on co-tunneling and then they tune the current flow in SET. 相似文献
5.
The diffusion of an overdamped Brownian particle in a tilted periodic potential is known to exhibit a pronounced enhancement over the free thermal diffusion within a small interval of tilt values. Here we show that weak disorder in the form of small, time-independent deviations from a strictly spatially periodic potential may further boost this diffusion peak by orders of magnitude. Our general theoretical predictions are in excellent agreement with experimental observations. 相似文献
6.
We investigated single electron tunneling (SET) behavior of dodecanethiol-coated Au nanoparticles of two different sizes (average sizes are 5 nm and 2 nm) using nanogap electrodes, which have a well-defined gap size, at various temperatures. The Coulomb staircases and the Coulomb gap near-zero bias voltage caused by the suppression of the tunneling electrons due to the Coulomb blockade effect were observed in the current-voltage (I-V) curves of both sizes of nanoparticles at a low temperature (10 K). At room temperature, the Coulomb gap was observed only in the I-V curve of the smaller nanoparticles. This result indicates that the charging energy of the smaller nanoparticles is enough to overcome the thermal energy at room temperature. This suggests that it is possible to operate the SET devices at room temperature using the smaller nanoparticles as a Coulomb island. 相似文献
7.
Resonant tunneling through two identical potential barriers renders them transparent, as particle trajectories interfere coherently. Here we realize resonant tunneling in a quantum dot (QD), and show that detection of electron trajectories renders the dot nearly insulating. Measurements were made in the integer quantum Hall regime, with the tunneling electrons in an inner edge channel coupled to detector electrons in a neighboring outer channel, which was partitioned. Quantitative analysis indicates that just a few detector electrons completely dephase the QD. 相似文献
8.
Godfrey Gumbs 《Solid State Communications》2003,128(12):443-448
A model calculation is reported for the tunneling probability of one as well as two interacting electrons from a quantum well within a narrow channel. We discuss the cases when the two electrons are spin polarized or unpolarized by transforming the system to a noninteracting one with the use of quantal density functional theory to obtain an effective single-particle confining potential. A semiclassical approach is used to obtain the tunneling probability from this effective potential. The calculation is motivated by recent measurements of the conductance of an electron gas in a narrow channel but is not meant to explain the anomalous behavior that has been reported since, for example, we deal with a simplified two-level system. Numerical results for the tunneling probability are presented. 相似文献
9.
Juhani Kurkijärvi 《Physics letters. A》1982,88(5):241-244
It is shown that interpreting the zero-point noise of a resistor as dynamical noise capable of driving a Josephson phase across a potential barrier delivers qualitatively identical results with quantum mechanical tunneling calculation in the overdamped limit. 相似文献
10.
S. I. Denisov E. S. Denisova H. Kantz 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(1):1-11
We study the biased diffusion of particles moving in one direction under the action of a constant force in the presence of
a piecewise linear random potential. Using the overdamped equation of motion, we represent the first and second moments of
the particle position as inverse Laplace
transforms. By applying to these transforms the ordinary and the modified Tauberian theorem, we determine the short- and long-time
behavior of the mean-square displacement of particles. Our results show that while at short times the biased diffusion is
always ballistic, at long times it can be either normal or anomalous. We formulate the conditions for normal and anomalous
behavior and derive the laws of biased diffusion in both these cases. 相似文献
11.
The magnetic resonance line of conduction electrons in solids may exhibit bistable hysteresis if several conditions are fulfilled. Its mechanism is presented and the manifestation of bistability in the ESR of conduction electrons in single crystal and polycrystalline samples is discussed. The characteristics of the dynamics of the bistability show that bistable resonance can be assimilated to one-dimensional overdamped motion of the spin system in the nuclear field space, driven by a bistable potential. It is shown for the first time that noise acting on this bistable resonance can create order, by the phenomenon of stochastic resonance. 相似文献
12.
A one-dimensional model with time-dependent random hopping is proposed to describe charge transport in DNA. It permits the investigation of both diffusion of electrons and their tunneling between different sites in DNA. The tunneling appears to be strongly temperature-dependent. Observations of a strong (exponential) as well as a weak distance dependence of the charge transfer in DNA can be explained in the framework of our model. 相似文献
13.
We study the transport of overdamped Brownian particles in periodic potentials subject to a spatially modulated Gaussian white noise. We derive an analytical expression for the diffusion coefficient of particles. By means of velocity, diffusion coefficient, and their ratio (Péclet number) we discuss (a) symmetric potential and modulation of noise intensity and (b) a ratchet profile with strong noise modulation. It is shown that state dependent fluctuations may not only induce directed transport, but also a pronounced coherence of transport if the potential exhibits a strong asymmetry. 相似文献
14.
Sykes et al. [Proc. Natl. Acad. Sci. U.S.A. 102, 17907 (2005)] have reported how electrons injected from a scanning tunneling microscope modify the diffusion rates of H buried beneath Pd(111). A key point in that experiment is the symmetry between positive and negative voltages for H extraction, which is difficult to explain in view of the large asymmetry in Pd between the electron and hole densities of states. Combining concepts from the theory of ballistic electron microscopy and electron-phonon scattering we show that H diffusion is driven by the s-band electrons only, which explains the observed symmetry. 相似文献
15.
Canali CM 《Physical review letters》2000,84(17):3934-3937
We have numerically investigated the electron addition spectra in quantum dots containing a small number (N=10) of interacting electrons, in the presence of strong disorder. For a short-range Coulomb repulsion, we find regimes in which two successive electrons enter the dot sequentially but almost at the same value of the chemical potential. In the strongly correlated regime these close additions, or pairings, are associated with electrons tunneling into distinct electron puddles within the dot. We discuss the tunneling rates at pairing and argue that the results are related to a recently observed phenomenon known as bunching. 相似文献
16.
We study electrons tunneling through a double-magnetic-barrier structure on the surface of monolayer graphene.The transmission probability and the conductance are calculated by using the transfer matrix method.The results show that the normal incident transmission probability is blocked by the magnetic vector potential and the Klein tunneling region depends strongly on the direction of the incidence electron.The transmission probability and the conductance can be modulated by changing structural parameters of the barrier,such as width and height,offering a possibility to control electron beams on graphene. 相似文献
17.
P. E. Allain J. N. Fuchs 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,83(3):301-317
This article provides a pedagogical review on Klein tunneling in graphene, i.e. the
peculiar tunneling properties of two-dimensional massless Dirac electrons. We consider two
simple situations in detail: a massless Dirac electron incident either on a potential step
or on a potential barrier and use elementary quantum wave mechanics to obtain the
transmission probability. We emphasize the connection to related phenomena in optics, such
as the Snell-Descartes law of refraction, total internal reflection, Fabry-Pérot
resonances, negative refraction index materials (the so called meta-materials), etc. We
also stress that Klein tunneling is not a genuine quantum tunneling effect as it does not
necessarily involve passing through a classically forbidden region via evanescent waves. A
crucial role in Klein tunneling is played by the conservation of (sublattice) pseudo-spin,
which is discussed in detail. A major consequence is the absence of backscattering at
normal incidence, of which we give a new shorten proof. The current experimental status is
also thoroughly reviewed. The Appendix contains the discussion of a one-dimensional toy
model that clearly illustrates the difference in Klein tunneling between mono- and
bi-layer graphene. 相似文献
18.
19.
Bolivar AO 《Physical review letters》2005,94(2):026807
In the large damping limit we derive a Fokker-Planck equation in configuration space (the so-called Smoluchowski equation) describing a Brownian particle immersed into a thermal environment and subjected to a nonlinear external force. We quantize this stochastic system and survey the problem of escape over a double-well potential barrier. Our finding is that the quantum Kramers rate does not depend on the friction coefficient at low temperatures; i.e., we predict a superfluidity phenomenon in overdamped open systems. Moreover, at zero temperature we show that the quantum escape rate does not vanish in the strong friction regime. This result, therefore, is in contrast with the work by Ankerhold et al. [Phys. Rev. Lett. 87, 086802 (2001)]] in which no quantum tunneling is predicted at zero temperature. 相似文献
20.
The pronounced variation of the intensity of photons emitted from the tunneling gap of an STM with respect to the applied bias voltage Vt is studied experimentally using simultaneous measurements of tunneling characteristics and photon emission. We show that the structure in isochromat photon spectra are determined by the following: bias-dependent changes in tunneling characteristics, density of initial and final states, and modifications of tip-induced plasmon modes. It is demonstrated that isochromat spectra provide a conclusive test for the inelastic tunneling mechanism. Coupling between tunneling electrons and tip-induced plasmon modes which gives rise to the intense photon emission observed is discussed within this model. 相似文献