Aharonov—Bohm oscillations and distributions of equilibrium current in open quantum dot and ring interferometer

Magnetotransport in submicron devices formed on the basis of GaAs/AlGaAs structures is simulated by the method of nonequilibrium Green functions. In the one-particle approximation, the influence of a perpendicular magnetic field on electron transmission through a quasi-one-dimensional quantum dot and the Aharonov—Bohm interferometer is considered. Two-terminal conductance and magnetic moment of the devices are calculated. Two-dimensional patterns of equilibrium (persistent) currents are obtained. The correlations between energy dependences of magnetic moment and conductance are considered. For the quasi-one-dimensional quantum dot, regular conductance oscillations similar to the ABOs were found at low magnetic fields (0.05—0.4 T). In the case of a ring interferometer, the contribution to the total equilibrium current and magnetic moment at a given energy can change sharply both in magnitude and in sign when the magnetic field changes within the same Aharonov—Bohm oscillation. The conductance through the interferometer is determined not by the number of propagating modes, but rather by the influence of triangular quantum dots at the entrances to the ring, causing back scattering. Period of calculated ABOs corresponds to that measured for these devices.

Исследование взаимодействия атомов Cs с поверхностью сапфира с использованием сверхтонкой ячейки и метода вычисления второй производной спектра поглощения паров

The influence of the interaction of Cs atoms with a dielectric surface on the position and shape of the hyperfine components of the D2 line at nanometer-order distances between atoms and the surface is studied. The use of a nanocell with a wedge-shaped gap made it possible to study the dependence of the shifts of all the hyperfine components of the D2 line corresponding to the transitions Fg = 3- Fe = 2, 3, 4 and Fg = 4- Fe = 3, 4, 5, on the distance L between the atoms and the sapphire surface windows in the range of 50–400 nm. At L less than 100 nm, due to the van der Waals interaction, there is a strong broadening of atomic transitions and a shift of their frequencies to the low-frequency region of the spectrum (red shift). The calculation of the second derivative (SD) of the vapor absorption spectra in the nanocell allows one to spectrally resolve the hyperfine components of the atomic transition down to L about 50 nm and measure the coefficient of the van der Waals interaction C3. It is shown that, at L <100 nm, an additional red shift occurs with increasing atomic density, while at relatively large distances between atoms and the surface L about 400 nm, an increase in atomic density causes a blue shift of the atomic transition frequencies. The above results are important in the development of miniature submicron devices containing atomic vapor of alkali metal.

TheI-VCharacteristic Prediction of BCD LV pMOSFET Devices Based on an ANFIS-Based Methodology

Comprehensive and predictive modeling of submicron devices using the traditional TCAD EDA tools of device simulation has become increasingly perplexing due to a lack of reliable models and difficulties in calibrating available device models. This paper proposes a new technique to model BCD submicron pMOSFET devices and to predict device behaviors under different bias conditions and different geometry dimensions by using the adaptive neurofuzzy inference system (ANFIS), which combines fuzzy theory and adaptive neuronetworking. Here, the power of using ANFIS to realize theI-Vbehaviors is demonstrated in these p-channel MOS transistors. After a systematic evaluation, it can be found that the predicting results ofI-Vbehaviors of complicated submicron pMOSFETs by ANFIS are compared with the actual diagnostic experiment data, and a good agreement has been obtained. Furthermore, the error percentage was no greater than 2.5%. As such, the demonstrated benefits of this new proposed technique include precise prediction and easier implementation.