Abstract Terahertz molecular fingerprinting of thin films is limited by weak absorption and the bulky free-space paths commonly required for spectral readout. We propose a vertically integrated metasensor that combines a gap-tuned quasi-bound-state-in-the-continuum (q-BIC) metasurface with a GaN high-electron-mobility-transistor (HEMT) self-mixing detector. Radiative interference between an LC mode and a dipole mode produces a finite-linewidth q-BIC resonance, providing a frequency-selective sampling channel. The sector-antenna HEMT provides broadband electrical response. To account for electromagnetic coupling between the metasurface and antenna layers, we introduce an interlayer-corrected cascaded model that captures the effect of antenna loading on the q-BIC response. Full-wave simulations confirm that this correction preserves the designed spectral ordering and reproduces the integrated-device response with high fidelity. The resulting 36 electrical sampling channels cover 700 – 1200 GHz . Within the 750 – 1100 GHz analysis window, the device-encoded fingerprint features of L-tyrosine, L-arginine, and sucralose show spectral-shape correlations of 0.984, 0.976, and 0.970 with their reference absorption trends, respectively. Further loading analysis and mixture decoding show that the multichannel electrical features support thin-film thickness estimation and binary or ternary composition recovery. These results indicate that a coordinated architecture in which q-BIC pixels perform molecular spectral encoding and GaN HEMTs provide electrical transduction offers a feasible route toward compact terahertz molecular fingerprint sensors with transistor-based readout.
Abstract Addressing the p-type doping bottleneck in 2D Ga 2 O 3 remains a crucial challenge for advancing next-generation electronics. In this study, we employ Heyd–Scuseria–Ernzerhof hybrid density functional calculation to reveal that the p-type conductivity of 2D Cd-doped Ga 2 O 3 (Cd GaI ) originates from the strongly hybridization between Cd-4d xy and O-2p states at the valence band maximum (VBM), while retaining a direct bandgap feature. The enhanced VBM band curvature reduces the hole effective mass and yields an ultrahigh hole mobility of ∼417.68 cm 2 V −1 s −1 , accompanied by a pronounced mobility anisotropy of 34.86. Using the highly efficient neuroevolution potential-based machine learning, the calculated lattice thermal conductivity of Cd GaI is decreased by ∼30% compared with that of perfect 2D Ga 2 O 3 . This can be attributed to the increased atomic mass of Cd and enhanced scattering of low‐frequency acoustic and optical phonons, both of which shorten the phonon mean free path. Temperature-dependent lattice thermal conductivity follows a power law behavior of ∼ T −1.3 along the x direction, indicating combined three-phonon and four-phonon scattering processes, whereas ∼ T −1.1 along the y direction, where three-phonon scattering dominate. Particularly, Cd GaI structure with −2% compressive strain exhibits the robust p-type conductivity, direct bandgap, ultra-high hole mobility and anisotropy, underlining its strong potential for optoelectronic device applications.
Abstract The damping of magnetization precession in epitaxial Pd–Fe films both of uniform alloy composition and with a thickness-dependent composition gradient has been investigated. The study was carried out by ferromagnetic resonance (FMR) using two techniques: cavity-based FMR at a fixed frequency and coplanar waveguide-based FMR with frequency sweeping under a constant magnetic field. A substantial influence of iron concentration on the damping parameter is demonstrated. The damping of spin-wave resonance modes in the graded film was also examined. A good agreement has been established between the experimental data and the calculation of the mode-averaged damping.
Abstract Due to the fast development of modern high-frequency electronics, great attention has been paid to materials that can shield electromagnetic interference (EMI) and absorb the electromagnetic waves as these materials should be lightweight rather than heavy and highly reflective as the metallic shielding. In this study, a floating catalyst chemical vapor deposition (FCCVD) method was adopted to synthesize grapheneated carbon nanotubes (g-CNTs) in a simple one-step process without the use of any substrate. For assessing some of their electrodynamic properties, g-CNTs were added to an epoxy matrix with mass fractions from 5 to 20 wt% along with pristine CNT fillers. Characterization was made of the EMI shielding performance and complex permittivity through a Vector Network Analyzer in the X-band region (8-12GHz) and Ku-band region (12-18GHz). The total shielding effectiveness (SET) of the composite with 20 wt% g-CNTs was evaluated to be as high as 62.71 dB in Ku band which was much higher than its pristine CNT counterparts at the same loading. This superior attenuation is due to absorption-dominated mechanism (SEA >> SER). The improved performance has been attributed to the unique hierarchical foliates of the g-CNTs that induce a microscopic impedance gradient for reducing surface reflection and the complex 3-dimensional architecture of g-CNTs that acts as the volumetric trap to improve the interfacial polarization and the loss of conduction. Hence, the g-CNT/epoxy composites offer a very promising direction for ultra-efficient electromagnetic attenuation, positioning them as strong candidates for high-frequency telecommunication and portable-electronics applications.
Abstract A dual-chamber gas–liquid phase dielectric barrier discharge (DBD) reactor with tri-electrodes was designed for air-fed nitrogen fixation (NF). Air was activated in the gas-phase discharge chamber to produce NOx, and these NOx species continued to synthesize aqueous nitrate species in the gas–liquid discharge chamber. The effect of electrode configuration, applied voltage, air flow rate, initial solution pH, electric discharge duration on the concentration, selectivity of nitrate/nitrite/ammonia, total nitrogen concentration (TNC) and energy yield of NF was studied. The results showed that the DBD reactor with tri-electrodes efficiently produced microdischarges for N2 fixation of high nitrate selectivity at higher applied voltage. The initial pH of water in lower discharge chamber had little effect on the input power but significantly impacted on the transfer and conversion of gaseous NOx into aqueous nitrate, and a weak alkaline pH was more favorable for total nitrogen accumulation. Meanwhile, the input air flow rate in DBD reactor and the water volume in lower discharge chamber showed an optimum value, and the energy yield of total nitrogen fixation reached a maximum 0.84 g·kWh-1 at an initial solution pH 11 and a water volume of 35 mL. The optical emission spectrum in discharge regions indicated that the nitrogen fixation results at different applied voltage and air flow rate can be attributed to their influence on the production of N2*, N2+, and •OH and the experiments including electron quenching and dry air discharge indicated that NH4+ was mainly produced via the reduction of N2 by hydrated electrons.
