Catálogo de publicaciones - revistas

<jats:p>A comprehensive study of the negative and positive bias temperature instability (NBTI/PBTI) of 3D FinFET devices with different small channel lengths is presented. It is found while with the channel lengths shrinking from 100 nm to 30 nm, both the NBTI characteristics of p-FinFET and PBTI characteristics of n-FinFET turn better. Moreover, the channel length dependence on NBTI is more serious than that on PBTI. Through the analysis of the physical mechanism of BTI and the simulation of 3-D stress in the FinFET device, a physical mechanism of the channel length dependence on NBTI/PBTI is proposed. Both extra fluorine passivation in the corner of bulk oxide and stronger channel stress in p-FinFETs with shorter channel length causes less NBTI issue, while the extra nitrogen passivation in the corner of bulk oxide induces less PBTI degradation as the channel length decreasing for n-FinFETs. The mechanism well matches the experimental result and provides one helpful guide for the improvement of reliability issues in the advanced FinFET process.</jats:p>

<jats:p>Exploring silicon-based spin modulating junction is one of the most promising areas of spintronics. Using nonequilibrium Green’s function combined with density functional theory, a set of spin filters of hydrogenated zigzag silicene nanoribbons is designed by substituting a silicon atom with a boron one and the spin-correlated transport properties are studied. The results show that the spin polarization can be realized by structural symmetry breaking induced by boron doping. Remarkably, by tuning the edge hydrogenation, it is found that the spin filter efficiency can be varied from 30% to 58%. Moreover, it is also found and explained that the asymmetric hydrogenation can give rise to an obvious negative differential resistance which usually appears at weakly coupled junction. These findings indicate that the boron-doped ZSiNR is a promising material for spintronic applications.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>Benefiting from the induced image charge on film surface, the nanoparticle aggregating on metal exhibits interesting optical properties. In this work, a linear metal nanoparticle trimer on metal film system has been investigated to explore the novel optical phenomenon. Both the electric field and surface charge distributions demonstrate the light is focused on film greatly by the nanoparticles at two sides, which could be strongly modulated by the wavelength of incident light. And the influence of nanoparticle in middle on this light focusing ability has also been studied here, which is explained by the plasmon hybridization theory. Our finding about light focusing in nanoparticle aggregating on metal film not only enlarges the novel phenomenon of surface plasmon but also has great application prospect in the field of surface-enhanced spectra, surface catalysis, solar cells, water splitting, <jats:italic>etc</jats:italic>.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>A novel enhanced mode (E-mode) Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> metal–oxide–semiconductor field-effect transistor (MOSFET) with vertical FINFET structure is proposed and the characteristics of that device are numerically investigated. It is found that the concentration of the source region and the width coupled with the height of the channel mainly effect the on-state characteristics. The metal material of the gate, the oxide material, the oxide thickness, and the epitaxial layer concentration strongly affect the threshold voltage and the output currents. Enabling an E-mode MOSFET device requires a large work function gate metal and an oxide with large dielectric constant. When the output current density of the device increases, the source concentration, the thickness of the epitaxial layer, and the total width of the device need to be expanded. The threshold voltage decreases with the increase of the width of the channel area under the same gate voltage. It is indicated that a set of optimal parameters of a practical vertical enhancement-mode Ga<jats:sub>2</jats:sub>O<jats:sub>3</jats:sub> MOSFET requires the epitaxial layer concentration, the channel height of the device, the thickness of the source region, and the oxide thickness of the device should be less than 5 × 10<jats:sup>16</jats:sup> cm<jats:sup>−3</jats:sup>, less than 1.5 μm, between 0.1 μm − − 0.3 μm and less than 0.08 μm, respectively.</jats:p>

<jats:p>Y-shaped Kekulé bond textures in a honeycomb lattice on a graphene-copper superlattice have recently been experimentally revealed. In this paper, the effects of such a bond modulation on the transport coefficients of Kekulé-patterned graphene are investigated in the presence of a perpendicular magnetic field. Analytical expressions are derived for the Hall and longitudinal conductivities using the Kubo formula. It is found that the Y-shaped Kekulé bond texture lifts the valley degeneracy of all Landau levels except that of the zero mode, leading to additional plateaus in the Hall conductivity accompanied by a split of the corresponding peaks in the longitudinal conductivity. Consequently, the Hall conductivity is quantized as ± <jats:italic>ne</jats:italic> <jats:sup>2</jats:sup>/<jats:italic>h</jats:italic> for <jats:italic>n</jats:italic> = 2, 4, 6, 8, 10, …, excluding some plateaus that disappear due to the complete overlap of the Landau levels of different cones. These results also suggest that DC Hall conductivity measurements will allow us to determine the Kekulé bond texture amplitude.</jats:p>

<jats:p>A one-dimensional non-Hermitian quasiperiodic p-wave superconductor without <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathscr{P}}{\mathscr{T}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="script">P</mml:mi> <mml:mi mathvariant="script">T</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_1_017401ieqn1.gif" xlink:type="simple" /> </jats:inline-formula>-symmetry is studied. By analyzing the spectrum, we discovered that there still exists real–complex energy transition even if the inexistence of <jats:inline-formula> <jats:tex-math> <?CDATA ${\mathscr{P}}{\mathscr{T}}$?> </jats:tex-math> <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mi mathvariant="script">P</mml:mi> <mml:mi mathvariant="script">T</mml:mi> </mml:math> <jats:inline-graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="cpb_31_1_017401ieqn2.gif" xlink:type="simple" /> </jats:inline-formula>-symmetry breaking. By the inverse participation ratio, we constructed such a correspondence that pure real energies correspond to the extended states and complex energies correspond to the localized states, and this correspondence is precise and effective to detect the mobility edges. After investigating the topological properties, we arrived at a fact that the Majorana zero modes in this system are immune to the non-Hermiticity.</jats:p>

<jats:p>Existing studies via shot noise calculation conclude that the cross correlation between the currents in the two leads connected by a pair of Majorana zero modes (MZMs) vanishes when their coupling energy <jats:italic>ϵ</jats:italic> <jats:sub>M</jats:sub> → 0. Motivated by the intrinsic nature of nonlocality of the MZMs, we revisit this important problem and propose an experimental scheme to demonstrate the nonvanishing cross correlation even at the limit <jats:italic>ϵ</jats:italic> <jats:sub>M</jats:sub> → 0. The proposed scheme employs the Andreev-process-associated branch circuit currents, which are theoretically obtained by applying a decomposition analysis for the total currents while are accessible directly in practical measurement. For different bias voltage setup, we find intriguing results of both negative and positive correlationsand carry out simple physical understanding using a quantum jump technique. Importantly, combining together with the evidence of the zero-bias-peak of conductance, the nonlocal cross correlation predicted in this work can help to confirm the existence of thenonlocalMZMs.</jats:p>

<jats:title>Abstract</jats:title> <jats:p>This article reviews the basic theoretical aspects of octagraphene, an one-atom-thick allotrope of carbon, with unusual two-dimensional (2D) Fermi nesting, hoping to contribute to the new family of quantum materials. Octagraphene has an almost strongest sp<jats:sup>2</jats:sup> hybrid bond similar to graphene, and has the similar electronic band structure as iron-based superconductors, which makes it possible to realize high-temperature superconductivity. We have compared various possible mechanisms of superconductivity, including the unconventional s<jats:sup>±</jats:sup> superconductivity driven by spin fluctuation and conventional superconductivity based on electron–phonon coupling. Theoretical studies have shown that octagraphene has relatively high structural stability. Although many 2D carbon materials with C<jats:sub>4</jats:sub> carbon ring and C<jats:sub>8</jats:sub> carbon ring structures have been reported, it is still challenging to realize the octagraphene with pure square-octagon structure experimentally. This material holds hope to realize new 2D high-temperature superconductivity.</jats:p>

<jats:p>The kagome metals <jats:italic>A</jats:italic>V<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> (<jats:italic>A</jats:italic> = K, Rb, Cs) under ambient pressure exhibit an unusual charge order, from which superconductivity emerges. In this work, by applying hydrostatic pressure using a liquid pressure medium and carrying out electrical resistance measurements for RbV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>, we find that the charge order becomes suppressed under a modest pressure <jats:italic>p</jats:italic> <jats:sub>c</jats:sub> (1.4 GPa &lt; <jats:italic>p</jats:italic> <jats:sub>c</jats:sub> &lt; 1.6 GPa), while the superconducting transition temperature <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> is maximized. <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> is then gradually weakened with further increase of pressure and reaches a minimum around 14.3 GPa, before exhibiting another maximum around 22.8 GPa, signifying the presence of a second superconducting dome. Distinct normal state resistance anomalies are found to be associated with the second superconducting dome, similar to KV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. Our findings point to qualitatively similar temperature–pressure phase diagrams in KV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> and RbV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>, and suggest a close link between the second superconducting dome and the high-pressure resistance anomalies.</jats:p>

<jats:p>Controlling the anomalous Hall effect (AHE) inspires potential applications of quantum materials in the next generation of electronics. The recently discovered quasi-2D kagome superconductor CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> exhibits large AHE accompanying with the charge-density-wave (CDW) order which provides us an ideal platform to study the interplay among nontrivial band topology, CDW, and unconventional superconductivity. Here, we systematically investigated the pressure effect of the AHE in CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. Our high-pressure transport measurements confirm the concurrence of AHE and CDW in the compressed CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub>. Remarkably, distinct from the negative AHE at ambient pressure, a positive anomalous Hall resistivity sets in below 35 K with pressure around 0.75 GPa, which can be attributed to the Fermi surface reconstruction and/or Fermi energy shift in the new CDW phase under pressure. Our work indicates that the anomalous Hall effect in CsV<jats:sub>3</jats:sub>Sb<jats:sub>5</jats:sub> is tunable and highly related to the band structure.</jats:p>