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<jats:p>The first-principles calculations based on density functional theory are performed to study F-, Cl-, and N-related defects of amorphous SiO<jats:sub>2</jats:sub> (a-SiO<jats:sub>2</jats:sub>) and their impacts on carrier trapping and proton release. The possible geometric configurations of the impurity-related defects, the formation energies, the hole or electron trapping of the neutral defects, and the mechanisms to suppress proton diffusion by doping N are investigated. It is demonstrated by the calculations that the impurity atoms can interact with the oxygen vacancies and result in impurity-related defects. The reactions can be utilized to saturate oxygen vacancies that will cause ionization damage to the semiconducting devices. Moreover, the calculated formation energy indicates that the F- or Cl-related oxygen vacancy defect is a deep hole trap, which can trap holes and prevent them from diffusing to the a-SiO<jats:sub>2</jats:sub>/Si interface. However, three N-related defects, namely N(2)o–H, N(2)o=O, and N(3)o–<jats:italic>V</jats:italic> <jats:sub>o</jats:sub>, tend to act as shallow hole traps to facilitate hole transportation during device operation. The N(2)o and N(3)o configurations can be negatively charged as deep electron traps during the oxide charge buildup after ionization radiation. In addition, the nudged elastic band (NEB) calculations show that four N-related defects, namely N(2)o, N(2)o–H, N(2)o=O, and N(3)o are capable of capturing protons and preventing them from diffusing to and de-passivating the interface. This research reveals the fundamental properties of the F-, Cl-, and N-related defects in amorphous silica and the details of the reactions of the carrier trapping and proton release. The findings help to understand the microscopic mechanisms that alleviate ionization damage of semiconducting devices by doping a-SiO<jats:sub>2</jats:sub>.</jats:p>

<jats:p>Monolayer CrN has been predicted to be half-metallic ferromagnet with high Curie temperature. Due to bulk CrN’s biocompatibility, the monolayer is a promising candidate for bio-related devices. Here, using first-principles calculations based on density functional theory, we find that the formation energy of the bulk CrN stacking from layers with square lattice is only 68 meV/atom above the convex hull, suggesting a great potential to fabricate the monolayer CrN in a square lattice by using molecular beam epitaxy method. The monolayer CrN is then proved to be a soft material with an ultra-low Young’s modulus and can sustain very large strains. Moreover, the analysis of the projected density of states demonstrates that the ferromagnetic half-metallicity originates from the splitting of Cr-d orbitals in the CrN square crystal field, the bonding interaction between Cr–N, and that between Cr–Cr atoms. It is worth noting that the super-exchange interaction is much larger than the direct-exchange interaction and contributes to the ultra-high Curie temperature, which is obtained from Monte Carlo simulations based on Heisenberg model. Our findings suggest that the monolayer CrN can be an indispensable candidate for nanoscale flexible spintronic applications with good biocompatibility and is considerable appealing to be realized in experiment.</jats:p>

<jats:p>We investigate a modified Anderson model at the large-<jats:italic>N</jats:italic> limit, where the Coulomb interaction is replaced by the Sachdev–Ye–Kitaev random interaction. The resistivity of conduction electron <jats:italic>ρ</jats:italic> <jats:sub>c</jats:sub> has a minimum value around temperature <jats:italic>T</jats:italic>*, which is similar to the Kondo system, but the impurity electron’s density of state <jats:italic>A</jats:italic> <jats:sub>d</jats:sub>(<jats:italic>ω</jats:italic>) demonstrates no sharp-peak like the Kondo resonance around the Fermi surface. This provides a counterintuitive example where resistivity minimum exists without Kondo resonance. The impurity electron’s entropy <jats:italic>S</jats:italic> <jats:sub>d</jats:sub> and specific heat capacity <jats:italic>C</jats:italic> <jats:sub>v</jats:sub> show a crossover from Fermi liquid to a non-Fermi liquid behavior dependent on temperature. The system is a Fermi liquid at <jats:italic>T</jats:italic> &lt; <jats:italic>T</jats:italic>*, and becomes a non-Fermi liquid at <jats:italic>T</jats:italic> &gt; <jats:italic>T</jats:italic>*, and then becomes a Fermi gas at sufficiently high temperatures <jats:italic>T</jats:italic> ≫ <jats:italic>T</jats:italic>*. The non-Fermi liquid at the intermediate-<jats:italic>T</jats:italic> regime does not occur in the standard Anderson model. We also make a renormalization group analysis, which confirms the crossover from Fermi liquid to the non-Fermi behavior. It is emphasized that the resistivity minimum emerges in our model when the system behaves as a non-Fermi liquid rather than Fermi liquid, which provides an alternative example showing resistivity minimum in condensed matter physics.</jats:p>

<jats:p>As an alternative device for neuromorphic computing to conquer von Neumann bottleneck, the memristor serving as an artificial synapse has attracted much attention. The TaO<jats:sub> <jats:italic>x</jats:italic> </jats:sub> memristors embedded with silver nanoparticles (Ag NPs) have been fabricated to implement synaptic plasticity and to investigate the effects of Ag NPs. The TaO<jats:sub> <jats:italic>x</jats:italic> </jats:sub> memristors with and without Ag NPs are capable of simulating synaptic plasticity (PTP, STDP, and STP to LTP), learning, and memory behaviors. The conduction of the high resistance state (HRS) is driven by Schottky-emission mechanism. The embedment of Ag NPs causes the low resistance state (LRS) conduction governed by a Poole–Frenkel emission mechanism instead of a space-charge-limited conduction (SCLC) in a pure TaO<jats:sub> <jats:italic>x</jats:italic> </jats:sub> system, which is ascribed to the Ag NPs enhancing electric field to produce additional traps and to reduce Coulomb potential energy of bound electrons to assist electron transport. Consequently, the enhanced electric fields induced by Ag NPs increase the learning strength and learning speed of the synapses. Additionally, they also improve synaptic sensitivity to stimuli. The linearity of conductance modulation and the reproducibility of conductance are improved as well.</jats:p>

<jats:p>Transient electronics has attracted interest as an emerging technology to solve electronic-waste problem, due to its physically vanishing ability in solution. Here in this work, we demonstrate a flexible and degradable transient resistive switching (RS) memory device with simple structure of Cu/sodium alginate (SA)/ITO. The device presents excellent RS characteristics as well as high flexibility, including low operating voltage (&lt; 1.5 V) and multilevel RS behavior. No performance degradation occurs after bending the device 50 times. Moreover, our device can be absolutely dissolved in deionized water. The proposed SA-based transient memory device has great potential for the development of green and security memory devices.</jats:p>

<jats:p>The circular dichroism (CD) signal of a molecule is usually weak, however, a strong CD signal in optical spectrum is desirable because of its wide range of applications in biosensing, chiral photo detection, and chiral catalysis. In this work, we show that a strong chiral response can be obtained in a hybridized system consisting of an artificial chiral molecule and a nanorod in the strong coupling regime. The artificial chiral molecule is composed of six quantum dots in a helix assembly, and its CD signal arises from internal Coulomb interactions between quantum dots. The CD signal of the hybridized system is highly dependent on the Coulomb interactions and the strong coupling progress through the electromagnetic interactions. We use the coupled oscillator model to analyze strong coupling phenomenon and address that the strong coupling progress can amplify the CD signal. This work provides a scenario for designing new plasmonic nanostructures with a strong chiral optical response.</jats:p>

<jats:p>By using angle-resolved photoemission spectroscopy (ARPES) combined with the first-principles electronic structure calculations, we report the quantized states at the surface of a single crystal 2H-TaSe<jats:sub>2</jats:sub>. We have observed sub-bands of quantized states at the three-dimensional Brillouin zone center due to a highly dispersive band with light effective mass along <jats:italic>k<jats:sub>z</jats:sub> </jats:italic> direction. The quantized sub-bands shift upward towards <jats:italic>E</jats:italic> <jats:sub>F</jats:sub> while the bulk band at <jats:italic>Γ</jats:italic> shifts downward with the decrease of temperature across charge density wave (CDW) formation. The band shifts could be intimately related to the CDW. While neither the two-dimensional Fermi-surface nesting nor purely strong electron–phonon coupling can explain the mechanism of CDW in 2H-TaSe<jats:sub>2</jats:sub>, our experiment may ignite the interest in understanding the CDW mechanism in this family.</jats:p>

<jats:p>A novel n-type junctionless field-effect transistor (JLFET) with a step-gate-oxide (SGO) structure is proposed to suppress the gate-induced drain leakage (GIDL) effect and off-state current <jats:italic>I</jats:italic> <jats:sub>off</jats:sub>. Introducing a 6-nm-thick tunnel-gate-oxide and maintaining 3-nm-thick control-gate-oxide, lateral band-to-band tunneling (L-BTBT) width is enlarged and its tunneling probability is reduced at the channel--drain surface, leading the off-state current <jats:italic>I</jats:italic> <jats:sub>off</jats:sub> to decrease finally. Also, the thicker tunnel-gate-oxide can reduce the influence on the total gate capacitance of JLFET, which could alleviate the capacitive load of the transistor in the circuit applications. Sentaurus simulation shows that <jats:italic>I</jats:italic> <jats:sub>off</jats:sub> of the new optimized JLFET reduced significantly with little impaction on its on-state current <jats:italic>I</jats:italic> <jats:sub>on</jats:sub> and threshold voltage <jats:italic>V</jats:italic> <jats:sub>TH</jats:sub> becoming less, thus showing an improved <jats:italic>I</jats:italic> <jats:sub>on</jats:sub>/<jats:italic>I</jats:italic> <jats:sub>off</jats:sub> ratio (5 × 10<jats:sup>4</jats:sup>) and subthreshold swing (84 mV/dec), compared with the scenario of the normal JLFET. The influence of the thickness and length of SGO structure on the performance of JLFET are discussed in detail, which could provide useful instruction for the device design.</jats:p>

<jats:p>Low-frequency resistance noise spectroscopy is applied to investigate bulk single crystals of the intercalated iron-selenide K<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2 – <jats:italic>y</jats:italic> </jats:sub>Se<jats:sub>2</jats:sub> superconductors with different iron vacancy orders. Based on a generalized fluctuation model, the well-observed resistance hump above 100 K is interpreted as an insulator–metal phase transition with a characteristic transition energy of 0.1–0.6 eV, indicating a highly inhomogeneous energy distribution configuration. In the superconducting transition regime, we find that the normalized resistance noise scales with resistance <jats:italic>R</jats:italic> excellently as <jats:italic>S<jats:sub>R</jats:sub> </jats:italic>/<jats:italic>R</jats:italic> <jats:sup>2</jats:sup> ∝ <jats:italic>R</jats:italic> <jats:sup> <jats:italic>l</jats:italic> <jats:sub>rs</jats:sub> </jats:sup> with the noise exponent <jats:italic>l</jats:italic> <jats:sub>rs</jats:sub> ≈ 1.4. With reduced iron vacancy disordering in enhanced superconductivity K<jats:sub> <jats:italic>x</jats:italic> </jats:sub>Fe<jats:sub>2 – <jats:italic>y</jats:italic> </jats:sub>Se<jats:sub>2</jats:sub> crystals, the level of resistance fluctuations is greatly suppressed, suggesting a geometrical phase transition for conduction channel, which is directly related to the microstructure of the crystals.</jats:p>

<jats:p>Identifying the uniqueness of FeP-based superconductors may shed new lights on the mechanism of superconductivity in iron-pnictides. Here, we report nuclear magnetic resonance (NMR) studies on LiFeP and LiFeAs which have the same crystal structure but different pnictogen atoms. The NMR spectrum is sensitive to inhomogeneous magnetic fields in the vortex state and can provide the information on the superconducting pairing symmetry through the temperature dependence of London penetration depth <jats:italic>λ</jats:italic> <jats:sub>L</jats:sub>. We find that <jats:italic>λ</jats:italic> <jats:sub>L</jats:sub> saturates below <jats:italic>T</jats:italic> ∼ 0.2 <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> in LiFeAs, where <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> is the superconducting transition temperature, indicating nodeless superconducting gaps. Furthermore, by using a two-gaps model, we simulate the temperature dependence of <jats:italic>λ</jats:italic> <jats:sub>L</jats:sub> and obtain the superconducting gaps of LiFeAs, as <jats:italic>Δ</jats:italic> <jats:sub>1</jats:sub> = 1.2 <jats:italic>k</jats:italic> <jats:sub>B</jats:sub> <jats:italic>T</jats:italic> <jats:sub>c</jats:sub> and Δ<jats:sub>2</jats:sub> = 2.8 <jats:italic>k</jats:italic> <jats:sub>B</jats:sub> <jats:italic>T</jats:italic> <jats:sub>c</jats:sub>, in agreement with previous result from spin-lattice relaxation. For LiFeP, in contrast, <jats:italic>λ</jats:italic> <jats:sub>L</jats:sub> does not show any saturation down to <jats:italic>T</jats:italic> ∼ 0.03 <jats:italic>T</jats:italic> <jats:sub>c</jats:sub>, indicating nodes in the superconducting gap function. Finally, we demonstrate that strong spin fluctuations with diffusive characteristics exist in LiFeP, as in some cuprate high temperature superconductors.</jats:p>