We report on the experimental evidence of thermal terahertz (THz) emission tailored by magnetic polariton (MP) excitations in entirely GaAs-based structures equipped with metasurfaces. The n-GaAs/GaAs/TiAu structure was optimized using finite-difference time-domain (FDTD) simulations for the resonant MP excitations in the frequency range below 2 THz. Molecular beam epitaxy was used to grow the GaAs layer on the n-GaAs substrate, and a metasurface, comprising periodic TiAu squares, was formed on the top surface using UV laser lithography. The structures exhibited resonant reflectivity dips at room temperature and emissivity peaks at $T=390$ °C in the range from 0.7 THz to 1.3 THz, depending on the size of the square metacells. In addition, the excitations of the third harmonic were observed. The bandwidth was measured as narrow as 0.19 THz of the resonant emission line at 0.71 THz for a 42 μm metacell side length. An equivalent $LC$ circuit model was used to describe the spectral positions of MP resonances analytically. Good agreement was achieved among the results of simulations, room temperature reflection measurements, thermal emission experiments, and equivalent $LC$ circuit model calculations. Thermal emitters are mostly produced using a metal-insulator-metal (MIM) stack, whereas our proposed employment of n-GaAs substrate instead of metal film allows us to integrate the emitter with other GaAs optoelectronic devices. The MP resonance quality factors obtained at elevated temperatures ($Q\approx 3.3\mathrm{to}5.2$) are very similar to those of MIM structures as well as to 2D plasmon resonance quality at cryogenic temperatures.

Electron paramagnetic resonance (EPR) spectroscopy is a broadly used technique to study paramagnetic centers in diverse fields ranging from biology to quantum technologies. The availability of well-established commercial instrumentation, including features such as rapid sample exchange, has been a key enabler for EPR to be applied widely across disciplines. Here, we present a three-order-of-magnitude increase in the spin number sensitivity of the commonly used X-band pulsed EPR while retaining full compatibility with conventional instrumentation and typical sample conditions. Our approach employs planar spiral-shaped microresonators with 7 nL mode volumes fabricated from yttrium barium copper oxide (YBCO) high-temperature superconductor. We achieve a wide range of microwave coupling by a single microresonator inside a conventional EPR tube, loaded into an EPR cavity. The performance of the spiral microresonators is demonstrated through a suite of pulsed EPR experiments on standard samples including dipolar and hyperfine spectroscopies. By placing a sample within a microfluidic microstructure fabricated to match the mode profile of the microresonator, we obtain a high-fidelity spin control with a spin-number sensitivity of 10^7 spins/G/Hz^1/2. Our approach significantly advances the applicability of superconducting microresonators as versatile and readily applicable tools for high sensitivity EPR.

The ability to directly deposit graphene layers on diverse substrates (including the ones with existing functioning electronic devices) is a very attractive method for integrating two-dimensional materials into electronic systems based on typical semiconductors. However, the task is highly challenging due to the high temperatures required for synthesis of the graphene structures. Plasma-enhanced chemical vapor deposition is an option that can be used to produce large-area graphene layers at sufficiently low temperatures. A lack of deep understanding of the plasma-associated processes limits the ability to directly control graphene growth. In this study, we experimentally investigated how the density of the ionized species flow influences the growth of the nanostructured graphene layers using a custom process chamber layout. The relationship between the growth of the nanostructured carbon-based films and the flow of the ionized species of the working gas mixture was quantitatively characterized for a set of specific parameters. We also analyzed the influence of deposition time and substrate temperature on the growth of the films and discuss the driving mechanisms. Three unique stages were identified in the self-arrangement of the layer. The activation energy of the process was ∼0.31 eV.

Unique electronic properties of graphene offer highly interesting ways to manipulate the functional properties of surfaces and develop novel structures which are sensitive to physical and chemical interactions. Nano-crystalline graphene is frequently preferable to crystalline monolayer in detecting devices. In this work, nano-crystalline graphene layers were synthesized directly on SiO₂/Si substrates by plasma-enhanced chemical vapour deposition (PECVD). The influence of the deposition time and temperature on the characteristics of the structures were studied. The optical properties and evaporation kinetics of pure water droplets were analysed, along with arrangement and composition of the grown layers. The nano-crystalline graphene layers grown at 500 °C were characterised by the refraction index 2.75 ± 0.35 and the normalised excess Gibbs free energy density 0.85/γ_water 10⁻⁴ m, both being similar to those of the monolayer graphene. The changes in the refraction index and the excess Gibbs free energy were related to the parameters of the Raman spectra and a correlation with the technological variables were disclosed.