Search Results (43)

This study employed first-principles density functional theory (DFT) to systematically investigate the influence of oxygen (–O) functional groups on the structural, magnetic, and electronic properties of Janus MXene CrScC. Nine distinct CrScCO₂ configurations with varying oxygen adsorption sites were examined. All configurations exhibited robust ferromagnetic ordering, with total magnetic moments ranging from 1 to 3 μ_B, predominantly contributed by Cr atoms. Notably, the majority of the configurations exhibited half-metallic behavior, characterized by fully spin-polarized conduction channels and half-metallic gaps spanning 0.23–1.54 eV, with one configuration approaching a spin-gapless semiconductor characterized by a minimal bandgap (<0.1 eV). The ground-state configuration demonstrated strong performance, featuring a 100% spin polarization ratio and a wide half-metallic gap of 0.44 eV, indicating significant potential for spintronic applications. Phonon spectrum calculations confirmed the dynamic stability of the half-metallic ground-state structure, while binding energy analysis highlighted the enhanced stability of the oxygen-functionalized system compared to pristine CrScC. These results demonstrate that –O functional groups play a key role in modulating the magnetism and electronic properties of CrScC, offering versatility for various spintronic device applications. Full article

Graphene films are widely used in thermal management of electronic devices due to their excellent properties such as high flexibility, high thermal conductivity and light weight. However, in the traditional preparation process, some structural defects are introduced, which will lead to an increase in phonon scattering, thereby reducing the thermal conductivity of graphene. Therefore, a new method for preparing graphene thin films is proposed by using the evaporation method; the graphene oxide composite film is prepared by adding carbon-rich molecules (CRMs) to the graphene oxide dispersion liquid. The experimental results show that the addition of a mass fraction of 0.15% CRMs helps to form continuous strips and channels, which are beneficial to the construction of the internal aromatic structure of graphene and improve the crystallinity of graphene film. The in-plane thermal conductivity of the composite film increased from 598.74 W/(m·K) to 704.27 W/(m·K) after adding carbon-rich molecules. However, excess CRMs can lead to the formation of disordered structures during graphitization, which will reduce the thermal conductivity of the film to a certain extent. The radiation properties of graphene films are also proposed to verify the validity of the above conclusions, and the results show that the graphene film with a mass fraction of 0.24% CRMs has better heat dissipation performance, which can be reduced by 5 °C compared with that of pure graphene film. Through the application of graphene in new energy car seats, it is proved that compared with the resistance wire seats, graphene seats have better performance in terms of a fast heating speed and uniform heating. Full article

Cubic-phase SnSe possesses exceptional crystal structure symmetry while maintaining non-harmonic bond characteristics and ultra-low lattice thermal conductivity, exhibiting superior thermoelectric (TE) application potential compared to its orthorhombic counterpart. Despite recent advancements, systematic investigations on the combined effects of composite engineering strategies in optimizing TE properties of cubic-phase SnSe-based materials remain scarce. In this study, multi-walled carbon nanotubes (MWCNTs) are incorporated into the cubic-phase Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 to regulate its TE performance through a combination of ultrasonic dispersion and rapid hot-pressing sintering. The introduced MWCNTs promote the formation of “high-speed channel” for carrier transport and serve as additional phonon-scattering centers, resulting in a synergistic optimization of electrical and thermal transport properties. A maximum ZT value of 0.85 is achieved in the prepared 1.50 wt.% MWCNTs/Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 sample at 750 K, representing a 21% improvement compared to the pristine Sn_0.50Ag_0.25Bi_0.25Se_0.50Te_0.50 sample. This finding establishes a scalable nano-composite engineering paradigm for enhancing TE performance of cubic-phase SnSe-based materials. Full article

We report super broad non-Hermitian line shape from out-of-phase and in-phase photon-phonon dressing (quantization) in Eu³⁺: NaYF₄ and Eu³⁺: BiPO₄ nanocrystals. The line shape is controlled by changing time gate position, time gate width, power, temperature, sample, photomultiplier tubes, and laser. We observed that the fluorescence (FL) line-shape contrasts are 69.23% for Eu³⁺: BiPO₄ and 43.75% for Eu³⁺: NaYF₄, owing to the stronger out-of-phase photon-phonon dressing (destructive quantization). Moreover, we observed that the spontaneous four-wave mixing (SFWM) line shape was approximately three times wider at 300 K than at 77 K for the [(12:1)-phase] Eu³⁺: NaYF₄ due to more high-frequency in-phase phonon dressing (strong constructive quantization). Furthermore, we showed that the noise line-shape width remains unchanged for Eu³⁺: BiPO₄ (16 nm) and Eu³⁺: NaYF₄ (12 nm) due to out-of-phase and in-phase photon-phonon dressing balance. Such results have potential applications in multi-channel band stop filter. Full article

We demonstrate a Sn-doped monoclinic gallium oxide (β-Ga₂O₃)-based deep ultraviolet (DUV) phototransistor with high area coverage and manufacturing efficiency. The threshold voltage (V_T) switches between negative and positive depending on the β-Ga₂O₃ channel thickness and doping concentration. Channel depletion and Ga diffusion during manufacturing significantly influence device characteristics, as validated through computer-aided design (TCAD) simulations, which agree with the experimental results. We achieved enhancement-mode (e-mode) operation in <10 nm-thick channels, enabling a zero V_G to achieve a low dark current (1.84 pA) in a fully depleted equilibrium. Quantum confinement in thin β-Ga₂O₃ layers enhances UV detection (down to 210 nm) by widening the band gap. Compared with bulk materials, dimensionally constrained optical absorption reduces electron–phonon interactions and phonon scattering, leading to faster optical responses. Decreasing β-Ga₂O₃ channel thickness reduces V_T and V_G, enhancing power efficiency, dark current, and the photo-to-dark current ratio under dark and illuminated conditions. These results can guide the fabrication of tailored Ga₂O₃-based DUV phototransistors. Full article

Field-effect transistors (FETs) based on two-dimensional molybdenum disulfide (2D-MoS₂) have great potential in electronic and optoelectronic applications, but the performances of these devices still face challenges such as scattering at the contact interface, which results in reduced mobility. In this work, we fabricated high-performance MoS₂-FETs by inserting self-assembling monolayers (SAMs) between MoS₂ and a SiO₂ dielectric layer. The interface properties of MoS₂/SiO₂ were studied after the inductions of three different SAM structures including (perfluorophenyl)methyl phosphonic acid (PFPA), (4-aminobutyl) phosphonic acid (ABPA), and octadecylphosphonic acid (ODPA). The SiO₂/ABPA/MoS₂-FET exhibited significantly improved performances with the highest mobility of 528.7 cm² V⁻¹ s⁻¹, which is 7.5 times that of SiO₂/MoS₂-FET, and an on/off ratio of ~10⁶. Additionally, we investigated the effects of SAM molecular dipole vectors on device performances using density functional theory (DFT). Moreover, the first-principle calculations showed that ABPA SAMs reduced the frequencies of acoustic and optical phonons in the SiO₂ dielectric layer, thereby suppressing the phonon scattering to the MoS₂ channel and further improving the device’s performance. This work provided a strategy for high-performance MoS₂-FET fabrication by improving interface properties. Full article

In this paper, we explore the asymmetry observed between the effects of photon–phonon coupling (nested-dressing) and a crystal field (CF) on the fine structure of fluorescence (FL) and spontaneous four-wave mixing (SFWM) in Eu³⁺: BiPO₄ and Eu³⁺: NaYF₄. The competition between the CF and the strong photon–phonon dressing leads to dynamic splitting in two directions. The CF leads to static splitting in one direction under weak phonon dressing. The evolution from strong dressing to weak dressing results in spectral asymmetry. This spectral asymmetry includes out-of-phase FL and in-phase SFWM. Further, the large ratio between the dressing Rabi frequency and the de-phase rate leads to strong FL and SFWM asymmetry due to photon–phonon constructive dressing. Moreover, the experimental results suggest the analogy of a spectra asymmetry router with a channel equalization ratio of 96.6%. Full article

The concept of “rainbow trapping” has generated considerable interest in wave propagation and energy harvesting, offering new possibilities for diverse and efficient acoustic wave operations. In this work, we investigate a dual-channel topological rainbow trapping device implemented within an underwater two-dimensional phononic crystal based on synthetic dimension. The topological edge states with different frequencies are separated and trapped at different spatial locations. Acoustic waves propagate simultaneously along two boundaries due to the degeneracy of the edge states. In particular, the propagation of a dual-channel topological rainbow is also realized by using a bend design. This work contributes to the advancement of multi-channel devices in synthetic space and provides a reference for the design of highly efficient underwater acoustic devices. Full article

In the present work, the influence of alkali ions (Li, Na, K) on the structural and spectroscopic properties of silica glasses doped with Sm³⁺ was investigated. Infrared and Raman spectroscopy techniques were used to investigate the structural properties of the alkali silicate glasses. The optical absorption showed bands characteristic of Sm³⁺ ions in alkali silicate glasses, and this was investigated. The Judd–Ofelt theory was applied to evaluate the phenomenological intensity parameters (Ω₂, Ω₄, and Ω₆) of the optical absorption measurements. The multi-channel visible and near infrared emission transitions originating from the ⁴G_5/2-emitting state of the Sm³⁺ in alkali silicate glasses with a maximum phonon energy of ~1050 cm⁻¹ were investigated. From the evaluated Judd–Ofelt parameters, radiative parameters such as spontaneous emission probabilities, radiative lifetimes, branching ratios, and stimulated emission cross-sections were calculated. The recorded luminescence spectra regions revealed intense green, orange, red, and near-infrared emission bands, providing new traces for developing tunable laser and optoelectronic devices. Full article

The temperature dependence of the two superconducting gaps in pressurised $H_{3}S$ at 155 GPa with a critical temperature of 203 K has been determined using a data analysis of the experimental curve of the upper critical magnetic field as a function of temperature in the framework of the two-band s-wave Eliashberg theory. Two different phonon-mediated intra-band Cooper pairing channels in a regime of moderate strong couplings have the key role of the pair-exchange interaction between the two gaps, giving the two non-diagonal terms of the coupling tensor, which are missing in the single-band s-wave Eliashberg theory. The results provide a prediction of the different temperature dependence of the small and large gaps as a function of temperature, which provides evidence of multigap superconductivity in $H_{3}S$. Full article

Many theoretical models of iron-based superconductors (IBSC) have been proposed, but the superconducting transition temperature (T_c) calculations based on these models are usually missing. We have chosen two models of iron-based superconductors from the literature and computed the T_c values accordingly; recently two models have been announced which suggest that the superconducting electron concentration involved in the pairing mechanism of iron-based superconductors may have been underestimated and that the antiferromagnetism and the induced xy potential may even have a dramatic amplification effect on electron–phonon coupling. We use bulk FeSe, LiFeAs and NaFeAs data to calculate the T_c based on these models and test if the combined model can predict the superconducting transition temperature (T_c) of the nanostructured FeSe monolayer well. To substantiate the recently announced xy potential in the literature, we create a two-channel model to separately superimpose the dynamics of the electron in the upper and lower tetrahedral plane. The results of our two-channel model support the literature data. While scientists are still searching for a universal DFT functional that can describe the pairing mechanism of all iron-based superconductors, we base our model on the ARPES data to propose an empirical combination of a DFT functional for revising the electron–phonon scattering matrix in the superconducting state, which ensures that all electrons involved in iron-based superconductivity are included in the computation. Our computational model takes into account this amplifying effect of antiferromagnetism and the correction of the electron–phonon scattering matrix, together with the abnormal soft out-of-plane lattice vibration of the layered structure. This allows us to calculate theoretical T_c values of LiFeAs, NaFeAs and FeSe as a function of pressure that correspond reasonably well to the experimental values. More importantly, by taking into account the interfacial effect between an FeSe monolayer and its SrTiO₃ substrate as an additional gain factor, our calculated T_c value is up to 91 K and provides evidence that the strong T_c enhancement recently observed in such monolayers with T_c reaching 100 K may be contributed from the electrons within the ARPES range. Full article

This work reports the first nanocrystalline SnON (7.6% nitrogen content) nanosheet n-type Field-Effect Transistor (nFET) with the transistor’s effective mobility (µ_eff) as high as 357 and 325 cm²/V-s at electron density (Q_e) of 5 × 10¹² cm⁻² and an ultra-thin body thickness (T_body) of 7 nm and 5 nm, respectively. At the same T_body and Q_e, these µ_eff values are significantly higher than those of single-crystalline Si, InGaAs, thin-body Si-on-Insulator (SOI), two-dimensional (2D) MoS₂ and WS₂. The new discovery of a slower µ_eff decay rate at high Q_e than that of the SiO₂/bulk-Si universal curve was found, owing to a one order of magnitude lower effective field (E_eff) by more than 10 times higher dielectric constant (κ) in the channel material, which keeps the electron wave-function away from the gate-oxide/semiconductor interface and lowers the gate-oxide surface scattering. In addition, the high µ_eff is also due to the overlapped large radius s-orbitals, low 0.29 m_o effective mass (m_e*) and low polar optical phonon scattering. SnON nFETs with record-breaking µ_eff and quasi-2D thickness enable a potential monolithic three-dimensional (3D) integrated circuit (IC) and embedded memory for 3D biological brain-mimicking structures. Full article

Molybdenum disulfide (MoS₂) has distinctive electronic and mechanical properties which make it a highly prospective material for use as a channel in upcoming nanoelectronic devices. An analytical modeling framework was used to investigate the I–V characteristics of field-effect transistors based on MoS₂. The study begins by developing a ballistic current equation using a circuit model with two contacts. The transmission probability, which considers both the acoustic and optical mean free path, is then derived. Next, the effect of phonon scattering on the device was examined by including transmission probabilities into the ballistic current equation. According to the findings, the presence of phonon scattering caused a decrease of 43.7% in the ballistic current of the device at room temperature when L = 10 nm. The influence of phonon scattering became more prominent as the temperature increased. In addition, this study also considers the impact of strain on the device. It is reported that applying compressive strain could increase the phonon scattering current by 13.3% at L = 10 nm at room temperature, as evaluated in terms of the electrons’ effective masses. However, the phonon scattering current decreased by 13.3% under the same condition due to the existence of tensile strain. Moreover, incorporating a high-k dielectric to mitigate the impact of scattering resulted in an even greater improvement in device performance. Specifically, at L = 6 nm, the ballistic current was surpassed by 58.4%. Furthermore, the study achieved SS = 68.2 mV/dec using Al₂O₃ and an on–off ratio of 7.75 × 10⁴ using HfO₂. Finally, the analytical results were validated with previous works, showing comparable agreement with the existing literature. Full article

In this study, single crystals of Tr_xBi₂Se₃ (Tr = Co, Fe, and Mn) were produced via a melt-grown reaction. All crystals are c-axis oriented with an excellent single crystalline phase. The smaller ionic radius of the transition metal elements makes the QLs of Bi₂Se₃ thinner. Their abundant magnetism will provide spin–phonon coupling channels when the phonons are scattering in the system. Both Stokes and anti-Stokes Raman spectroscopy were performed for the three optical phonon modes of the Bi₂Se₃ crystals. These peaks were centered at 74.5 cm⁻¹, 133.4 cm⁻¹, and 175.2 cm⁻¹ and were attributable to the A_1g(1), E_g(2), and A_1g(2) modes, respectively. With an increase in the doping concentration, the magnetic and compressive strains induced by impurities dominate the phonon dynamics of materials. The results provide an effective scheme to regulate the thermoelectric properties of a Bi₂Se₃ system. Full article

A microwave photonic channelizer can achieve instantaneous reception of ultra-wideband signals and effectively avoid electronic bottleneck; therefore, it can be perfectly applied to a wideband radar system and electronic warfare. In channelization schemes based on an optical frequency comb (OFC), the number of comb lines usually depends on that of the sub-channels. In order to improve the utilization rate of the comb lines of OFC, we propose a scheme to shift the frequency of OFC by using an acousto-optic frequency shifter (AOFS), which can obtain three times the number of sub-channels of the comb lines of an OFC. In order to simplify the experiment, only a three-line OFC is used in the experiment. A three-line local oscillator (LO) OFC is frequency-shifted up and down by two AOFSs, and nine optical LO signals with different frequencies are obtained, thereby realizing the simultaneous reception of eighteen sub-channels. The proposed scheme enjoys a large number of sub-channels and minimal channel crosstalk. Experimental results demonstrate that a 9-GHz bandwidth RF signal covering 10–19 GHz is divided into 18 sub-channels with a sub-bandwidth of 500 MHz. The image rejection ratio of the sub-channels is about 23 dB, and the spurious-free dynamic range (SFDR) of the receiver can reach 98 dB·Hz^2/3. Full article