[en] Semiconductor quantum dot structure provides a promising basis for quantum information processing, within which to reveal the quantum phase and charge transport is one of the most important issues. In this paper, by means of the numerical renormalization group technique, we study the quantum phase transition and the charge transport for a parallel triple dot device in the strongly correlated limit, focusing on the effect of inter-dot hopping t beyond the Kondo regime. We find the quantum behaviors depend closely on the initial electron number on the dots, and the present model may map to single, double, and side-coupled impurity models in different parameter spaces. An orbital spin-1/2 Kondo effect between the conduction leads and the bonding orbital, and several magnetic-frustration phases are demonstrated when t is adjusted to different regimes. To understand these phenomena, a canonical transformation of the energy levels is given, and important physical quantities with respect to increasing t and necessary theoretical discussions are shown. (paper)

[en] Using the nonequilibrium Green's function technique, electron transport through a laterally coupled vertical triple quantum dot is investigated. The conductance as a function of electron energy is numerically calculated. The evolution of the conductance strongly depends on the configuration of dot levels and interdot coupling strengths. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] Devices with copper phthalocyanine (CuPc):molybdenum trioxide (MoO_3) co-evaporated layer were fabricated and the current–voltage (I–V) and capacitance–voltage (C–V) characteristics were measured. It has been found that for a given voltage, the current of the device with a co-evaporated layer is higher than those without the co-evaporated layer and it reaches the highest value if the ratio of MoO_3 to CuPc is 1:1. Meanwhile, the C–V characteristics showed that only free holes exist in the function layer consisting of pure CuPc. However, charge transfer (CT) complexes exist in the function layer of a CuPc:MoO_3 mixture. The charge transfer complexes do not contribute to the transport of the device efficiently under low applied fields but are disassociated into free carriers rapidly at applied fields higher than 1.7 × 10"5 V/cm, which greatly increases the conductivity. (paper)

[en] In order to approach an accurate and immediate alpha spectrometry with noise subtraction, a set up with different vacuum conditions was used. Several parameters obtained from experimental alpha spectroscopy and indicating properties of spectroscopy, e.g. peak value, half-peak width and boundaries, were optimized in terms of weight and threshold by selecting and cross-operating in genetic algorithm prior to be trained in BP nerve network as input data. Experimental results show that the optimized BP nerve network is better than the non-optimized one in terms of alpha spectroscopy noise subtraction. (authors)

[en] Three-dimensional integrated circuits (3D ICs) have entered into the mainstream due to their high performance, high integration, and low power consumption. When used in atmospheric environments, 3D ICs are irradiated inevitably by neutrons. In this paper, a 3D die-stacked SRAM device is constructed based on a real planar SRAM device. Then, the single event upsets (SEUs) caused by neutrons with different energies are studied by the Monte Carlo method. The SEU cross-sections for each die and for the whole three-layer die-stacked SRAM device is obtained for neutrons with energy ranging from 1 MeV to 1000 MeV. The results indicate that the variation trend of the SEU cross-section for every single die and for the entire die-stacked device is consistent, but the specific values are different. The SEU cross-section is shown to be dependent on the threshold of linear energy transfer (LET_th) and thickness of the sensitive volume (T_sv). The secondary particle distribution and energy deposition are analyzed, and the internal mechanism that is responsible for this difference is illustrated. Besides, the ratio and patterns of multiple bit upset (MBU) caused by neutrons with different energies are also presented. This work is helpful for the aerospace IC designers to understand the SEU mechanism of 3D ICs caused by neutrons irradiation. (paper)

[en] The electronic structures, magnetic properties, half-metallicity, and mechanical properties of half-Heulser compounds CoCrZ (Z = S, Se, and Te) were investigated using first-principles calculations within generalized gradient approximation based on the density function theory. The half-Heusler compounds show half-metallic properties with a half-metallic gap of 0.15 eV for CoCrS, 0.10 eV for CoCrSe, and 0.31 eV for CoCrTe at equilibrium lattice constant, respectively. The total magnetic moments are $3.00{\mathrm{\mu <!--\; ??\; -->}}_{\mathrm{B}}$ per formula unit, which agrees well with the Slater–Pauling rule. The half-metallicity, elastic constants, bulk modulus, shear modulus, Pough’s ratio, Frantesvich ratio, Young’s modulus, Poisson’s ratio, and Debye temperature at equilibrium lattice constant and versus lattice constants are reported for the first time. The results indicate that the half-Heulser compounds CoCrZ (Z = S, Se, and Te) maintain the perfect half-metallic and mechanical stability within the lattice constants range of 5.18–5.43 Å for CoCrS, 5.09–5.61 Å for CoCrSe, and 5.17–6.42 Å for CoCrTe, respectively. (paper)

[en] Using the nonequilibrium Keldysh Green's function technique, the Fano effect of a parallel-coupled triple Rashba quantum dot system is investigated. The conductance as a function of electron energy is numerically calculated. Compared with the case of a parallel-coupled double quantum dot system, two additional Fano resonance peaks occur in the conductance spectrum. By adjusting the structural parameters, the two Fano resonance peaks may change into the resonance peaks. In addition, the influence of Rashba spin-orbit interaction on the conductance is studied. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] In this paper, high temperature direct current (DC) performance of bilayer epitaxial graphene device on SiC substrate is studied in a temperature range from 25 °C to 200 °C. At a gate voltage of −8 V (far from Dirac point), the drain-source current decreases obviously with increasing temperature, but it has little change at a gate bias of +8 V (near Dirac point). The competing interactions between scattering and thermal activation are responsible for the different reduction tendencies. Four different kinds of scatterings are taken into account to qualitatively analyze the carrier mobility under different temperatures. The devices exhibit almost unchanged DC performances after high temperature measurements at 200 °C for 5 hours in air ambience, demonstrating the high thermal stabilities of the bilayer epitaxial graphene devices. (paper)

[en] We report the circuit simulations and experiments of millimeter-wave radiation from a high temperature superconducting (HTS) bicrystal Josephson junction (BJJ) array. To study the effects of junction characteristic parameters on radiation properties, new radiation circuit models are proposed in this paper. The series resistively and capacitively shunted junction (RCSJ) models are packaged into a Josephson junction array (JJA) model in the simulation. The current-voltage characteristics (IVCs) curve and radiation peaks are simulated and analyzed by circuit models, which are also observed from the experiment at liquid nitrogen temperature. The experimental radiation linewidth and power are in good agreement with simulated results. The presented circuit models clearly demonstrate that the inconsistency of the JJA will cause a broad linewidth and a low detected power. The junction radiation properties are also investigated at the optimal situation by circuit simulation. The results further confirm that the consistent JJA characteristic parameters can successfully narrow the radiation linewidth and increase the power of junction radiation. (paper)

[en] Porous ternary Zn₂SnO₄ nanofibers with a high surface-to-volume ratio were fabricated through an electrospinning technique. UV-activated ethanol sensing responses at low temperatures were revealed using these porous Zn₂SnO₄ nanofibers as a sensing active layer. The ethanol response was up to 32.5, and the calculated detection limit was as low as 1.6 ppm at a low temperature of 130 °C. The sensor exhibited good ethanol selectivity and stability under UV irradiation. The photoinduced electrons reacted with the absorbed oxygen molecules to form active O⁻ species [O⁻(hν)], which contributed to the enhanced resistance modulation and low-temperature ethanol response of Zn₂SnO₄ nanofibers.