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Electron transfer during binding processes between thiolate molecules and Au nano-islands
摘要： We investigated electron transfer during the time-dependent binding processes between thiolate molecules and Au nano-islands by observing tunneling current with an interdigitated microelectrode supporting the sputtered Au nano-islands (IME@AuNI). The time-dependent optical and electrical signal variation during the binding process was examined for five kinds of thiolates. As the immersion time was prolonged, the optical absorbance increased, whereas the current passing through the IME@AuNI decreased. Importantly, the spectral and current characteristics depended on the thiolate structure, because of the formation of capping layer in accordance with thiolate structure. These results are mainly attributed to synergistic effects of electron transfer from Au nano-islands to thiolate molecules and bridging effects of thiolate molecules among Au nano-islands.
关键词： Au nano-islands,Thiolate molecules,Electron transfer,Localized surface plasmon resonance,Tunneling current
更新于2025-09-23 15:22:29
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Controlled switching of a single CuPc molecule on Cu(111) at low temperature
摘要： Low temperature measurements of the tunneling current as a function of the applied bias voltage have been performed on a dense constant-height grid above individual copper phthalocyanine molecules adsorbed on a Cu(111) surface. By appropriate tuning of the applied bias, the molecule can be reversibly switched between two configurations in which pairs of opposite maxima appear rotated by 90? in the tunneling current map. The underlying conformations are revealed by density functional calculations including van der Waals interactions: a C2v symmetric ground state and two energetically equivalent states, in which the molecule is twisted and rotated around its center by ±7?. For tip biases above 200 mV position-dependent current switching is observed, as in previous measurements of telegraph noise [Schaffert et al., Nat. Mater. 12, 223 (2013)]. In a small voltage interval around zero the measured current becomes bistable. Switching to a particular state can be initiated by sweeping the voltage past well-defined positive and negative thresholds at certain positions above the molecule or by scanning at constant current and a reduced reverse bias.
关键词： density functional calculations,van der Waals interactions,tunneling current,copper phthalocyanine,Cu(111) surface,bistable current
更新于2025-09-23 15:19:57
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Embedded quantum dots in semiconductor nanostructures
摘要： In this work, we report the behavior of the tunneling current in a semiconductor nanostructure of (Ga, Al)As/GaAs which takes into account the behavior of the electrons and the Rashba’s spin orbit interaction in the presence of embedded quantum dots of di?erent geometries (lens, pyramid and ring) in voltage function, magnetic ?eld, and the di?erent values of the interaction spin orbit (π/2, π/4 and 3π/4). The results that were obtained show, that the intensity of the current presents appreciable changes when is changed the con?guration of the quantum dot as the intensities of external ?elds and spin polarization as well. All these internal and external e?ects that are studied in our model, signi?cantly modify the transport of information of the semiconductor nanostructure, our results show that the spin e?ects and the quantum dot con?guration contribute to the quantum memories e?ciency and the spin ?lter devices of actual use on nanoscience and nanotechnology.
关键词： quantum dots,Rashba’s spin orbit interaction,tunneling current,semiconductor nanostructures
更新于2025-09-11 14:15:04
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Conduction mechanisms of the reverse leakage current of 4H-SiC Schottky barrier diode
摘要： A new numerical method for determining the reverse transition voltage between thermionic and tunneling mechanisms has been performed for 4H-SiC Schottky barrier diode. The idea of this method is based on equality between thermionic emission and tunneling process and both of them are combined with barrier lowering model. Application of this method shows a strong discrepancy between our results and that deduced from Padovani-Stratton condition. The reverse transition voltage was found increase linearly with increasing the barrier height, the effective mass and the inverse of doping concentration. In order to predict the reverse transition voltage as a function of temperature, doping concentration and barrier height for 4H-SiC Schottky barrier diode an analytical model has been proposed.
关键词： image force barrier lowering,reverse transition voltage,SiC Schottky diode,thermionic emission,tunneling current
更新于2025-09-04 15:30:14
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To the Problem of Optimization of Parameters of a Double Heterostructure Based on Direct-Gap Semiconductors for Avalanche Photodiodes
摘要： A double heterostructure based on direct-gap semiconductors with a photoabsorption middle layer at the avalanche breakdown voltage is considered. Such structures are used in the development of avalanche photodiodes with separate absorption and multiplication regions (APD with SAMR). It is shown that impact generation of electron–hole pairs should be considered in calculating the maximum possible characteristics of APDs with SAMR even in the absorption layer; therewith, this can be performed analytically.
关键词： avalanche photodiode,avalanche breakdown,multiplication,tunneling current,double heterostructure,doping,absorption
更新于2025-09-04 15:30:14
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Force-noise spectroscopy by tunneling current deflection sensing
摘要： An electro-mechanical setup for the measurement of force-noise properties in a low-temperature tunneling microscope has been utilized to enable extremely high resolution and acquire force-noise spectra as function of the applied voltage bias. The direct crosstalk of vibrations onto the tunneling current is used to measure the de?ection of a force-sensing cantilever. We demonstrate its capability to measure the mechanical energy of the cantilever, caused by the noise of the force from vacuum tunneling between polycrystalline Iridium electrodes. We observe peak levels of the induced cantilever energy at polarity-symmetric voltages corresponding to dominant peaks of the phonon density of states, which suggests that inelastic transport processes contribute to force ?uctuations.
关键词： inelastic transport processes,force-noise spectroscopy,cantilever deflection,tunneling current,phonon density of states
更新于2025-09-04 15:30:14