We introduce Microgel-based Etalon Membranes (MEMs), based on the combination of stimuli-responsive microgels with an etalon, which is an optical device consisting of two reflecting plates and is used to filter specific wavelengths of light. The microgels are sandwiched between two reflective layers and, in response to a stimulus (e.g., temperature, pH, or biomarker concentration), swell or de-swell, thereby changing the distance between the two reflective layers and generating multiple peaks in the reflectance spectra. This property gives a MEM the unique capability of simultaneous separation and tunable responses to environmental changes and/or biomarker concentrations. We propose a design based on gold layers on a silicon nitride wafer membrane. Our comprehensive characterization, employing permeability experiments, in situ optical reflectance spectroscopy, in-liquid atomic force microscopy (AFM) analysis, and captive bubble contact angle measurements, elucidates the dynamic response of MEM to pH, temperature, and glucose stimuli and the corresponding effect of microgel swelling/de-swelling on the membrane properties, e.g., permeability. The AFM results confirm the dynamic changes of the microgel layer’s thickness on the membrane surface in response to the stimuli. Although the microgel’s swelling/de-swelling influences the effective pore radius, the decrease in the membrane’s permeance is limited to less than 10%. In the swollen state of the microgels, the etalon membranes show a prominent hydrophilic behavior, while they become less hydrophilic in the microgels’ de-swollen state. This work introduces MEM and provides novel insights into their behavior. The fundamental understanding that we reveal opens the way to applications ranging from point-of-care testing to continuous environmental monitoring.

Photo-conductive antennas (PCAs) are the workhorse of time-domain THz sensing and imaging. In this work, we employ a rigorous Norton equivalent circuit model to identify and estimate the substrate-related parasitic effects, that might limit the THz emission, to better design future PCAs.

For decades, mechanical resonators with high sensitivity have been realized using thin-film materials under high tensile loads. Although there are remarkable strides in achieving low-dissipation mechanical sensors by utilizing high tensile stress, the performance of even the best strategy is limited by the tensile fracture strength of the resonator materials. In this study, a wafer-scale amorphous thin film is uncovered, which has the highest ultimate tensile strength ever measured for a nanostructured amorphous material. This silicon carbide (SiC) material exhibits an ultimate tensile strength of over 10 GPa, reaching the regime reserved for strong crystalline materials and approaching levels experimentally shown in graphene nanoribbons. Amorphous SiC strings with high aspect ratios are fabricated, with mechanical modes exceeding quality factors 10⁸ at room temperature, the highest value achieves among SiC resonators. These performances are demonstrated faithfully after characterizing the mechanical properties of the thin film using the resonance behaviors of free-standing resonators. This robust thin-film material has significant potential for applications in nanomechanical sensors, solar cells, biological applications, space exploration, and other areas requiring strength and stability in dynamic environments. The findings of this study open up new possibilities for the use of amorphous thin-film materials in high-performance applications.

State-of-the-art THz pulsed commercial systems operating over large bandwidth suffer from high dispersion or low radiation efficiency due to the poor coupling between the transmitter and receiver photoconductive antennas (PCAs). In this work, we present the fabrication and characterization of a leaky-lens PCA that has the potential to solve this problem. The presented PCA is based on a low-temperature grown gallium arsenide (LT-GaAs) membrane with a 1:15 bandwidth coverage (0.1-1.5 THz), where the frequency response is constant. In order to fabricate the PCA on an LT-GaAs membrane, a novel fabrication process is developed. This process is dramatically faster than previously used processes (∼1.5 h instead of ∼20 h). Furthermore, an experimental validation of the radiated power together with the comparison to a standard bow-tie-based PCA fabricated on the same LT-GaAs wafer is shown in this article. We show that the PCA source on the LT-GaAs membrane is more efficient due to the enhanced leaky wave radiation. The leaky-lens PCA stands out as a great candidate to improve the coupling efficiency in THz pulsed commercial systems, where the maximum laser power that can be used is limited by the dispersion in the optic fiber.

Drude's description of the response of low-temperature gallium arsenide to optical pulse excitation is used to evaluate the components of a time-domain Norton equivalent circuit of a photoconductive antenna (PCA) source. The saturation of the terahertz (THz) radiated power occurring at large optical excitation levels was previously associated by the scientific community to radiation and charge screening of the bias. With the present circuit, we are able to model accurately the measured saturation as only due to the EM feedback from the antenna to the bias. The predicted THz radiated power is shown to match very accurately the measurements when the circuit is combined with an accurate description of the experimental conditions and the modeling of the THz quasi-optical (QO) channel.

Superconducting circuit elements used in millimeter-submillimeter (mm-submm) astronomy would greatly benefit from deposited dielectrics with small dielectric loss and noise. This will enable the use of multilayer circuit elements and thereby increase the efficiency of mm-submm filters and allow for a miniaturization of microwave kinetic inductance detectors (MKIDs). Amorphous dielectrics introduce excess loss and noise compared with their crystalline counterparts, due to two-level system defects of unknown microscopic origin. We deposited hydrogenated amorphous silicon films using plasma-enhanced chemical vapor deposition, at substrate temperatures of 100°C, 250°C, and 350°C. The measured void volume fraction, hydrogen content, microstructure parameter, and bond-Angle disorder are negatively correlated with the substrate temperature. All three films have a loss tangent below 10-5 for a resonator energy of 105 photons, at 120 mK and 4 to 7 GHz. This makes these films promising for MKIDs and on-chip mm-submm filters.

Metal-Semiconductor (M/S) heterojunctions, better known as Schottky junctions play a crucial role in modern electronics. At present, the mechanisms behind the M/S junctions are still a subject of discussion. In this work, we investigate the interfaces between semiconducting crystalline Si and amorphous metallic indium, Si{0 0 1}/a-In and Si{1 1 1}/a-In using both ab initio molecular dynamics simulations and a Schottky-Mott approach. The simulations reveal the formation of a distinct border between the Si substrates and amorphous In at the interfaces. The In atoms adjacent to the interfaces exhibit atomic ordering. Charge transfer occurs from In to Si, forming c-Si^−q/a-In^+q charge barriers at the interfaces. This indicates that a crystalline p-Si/a-In heterojunction will have rectifying properties, which agrees with an analysis using the Schottky-Mott model which predicts a Schottky barrier height of 1.3 eV for crystalline p-Si/a-In using the calculated work function for a-In (3.82 eV). We further discuss the interfacial charge transfer, related hole-depletion regions in Si adjacent to the interfaces and the Schottky-Mott approximations.

The recently found crystalline silicon-amorphous boron (c-Si/a-B) heterojunction has been successfully applied in the detection of short-wave UV photons. These detectors play a decisive role in the progress of nanoelectronics fabrication. The c-Si/a-B heterojunction could not be explained using the existing 'instrumentarium' in semiconductor physics. We investigated the c-Si/a-B interfaces using ab initio molecular dynamics simulations. The simulations reveal atomic ordering of the a-B atoms adjacent to both the Si{0 0 1} and Si{1 1 1} substrates. Charge transfer occurs from the interfacial Si to B, thereby forming Si+/B- charge barriers, which induce an electric field in the nearby regions. The obtained information here is helpful in furthering our understanding of the physics behind the c-Si/a-B junctions, as well as driving the development of a new 'instrumentatrium' in solid state physics.

The time evolution of voltages and currents in a pulsed photo conductive antenna (PCA) source is evaluated resorting to a rigorous procedure that stems from semiconductor physics first, to define the phenomena involved in the generation of the photocurrent, and then relies on an equivalent circuit in time domain, providing a direct estimation of the power generated by the PCA as well as its spectral distribution. The circuit model is validated via a campaign of measurements of standard PC antenna sources. The saturation phenomena in the THz radiated power occurring at large optical excitation levels, previously observed by the scientific community and associated to different phenomena, are accurately predicted by the present method, which ascribe their main cause to the feedback from the antenna: indeed, the electromagnetic field generated by the device tend to reduce the strength of the forcing field used to accelerate the photo-carriers.

Volumetric absorptive microsampling (VAMS) and dried urine spot (DUS) strategies were applied for the collection of dried microsamples for anti-doping testing of low-stability peptide hormones and growth factors prohibited by the World Anti-Doping Agency (WADA). Drying, storage and transport conditions, as well as pretreatment steps, were optimised before liquid chromatography - tandem mass spectrometry (LC–MS/MS) analysis. The analytical method has been fully validated in terms of sensitivity (limits of quantitation 0.3−10 ng/mL), precision (RSD% < 6.6 %) and extraction yields (78–91 %). Dried microsample stability studies (90 days) have been performed and compared to fluid urine stability. Significantly higher losses have been observed in fluid urine stored at −20 °C (up to 55 %) and −80 °C (up to 29 %) than in dried urine microsamples stored at room temperature (< 19 %). The final microsampling and analysis protocols allow the collection of urine microvolumes, unlikely to be tampered, stably storable and shippable with no particular precautions for possible anti-doping testing of prohibited peptides and hormones.

Clenbuterol is a chiral, selective β₂-adrenergic agonist. It is administered as a racemic mixture for therapeutic purposes (as a bronchodilator or prospective neuroprotective agent), but also for non-therapeutic uses (athletic performance enhancement, cattle growth promotion). Aim of the present study is to develop an original, enantioselective workflow for the analysis of clenbuterol enantiomers in urine microsamples. An innovative miniaturised sampling procedure by volumetric absorptive microsampling (VAMS) and a microsample pretreatment strategy based on stop-and-go extraction (StAGE) tips were developed and coupled to an original, chiral analytical method, exploiting liquid chromatography with triple quadrupole detection (LC-MS/MS). The method was validated, with satisfactory results: good linearity (r² ≥ 0.9995) and LOQ values (0.3 ng/mL) were found over suitable concentration ranges. Extraction yield (>87 %), precision (RSD < 4.3 %) and matrix effect (85–90 %) were all within acceptable levels of confidence. After validation, the method was applied to the determination of clenbuterol in dried urine sampled by VAMS from patients taking the drug for therapeutic reasons. Analyte content ranged from 0.8 to 2.5 ng/mL per single enantiomer, with substantial retention of the original drug racemic composition. The VAMS-StAGE-LC-MS/MS workflow seems to be suitable for future application to anti-doping testing of clenbuterol in urine.

The discovery of the extremely shallow amorphous boron-crystalline silicon heterojunction occurred during the development of highly sensitive, hard and robust detectors for low-penetration-depth ionizing radiation, such as ultraviolet photons and low-energy electrons (below 1 keV). For many years it was believed that the junction created by the chemical vapor deposition of amorphous boron on n-type crystalline silicon was a shallow p-n junction, although experimental results could not provide evidence for such a conclusion. Only recently, quantum-mechanics based modelling revealed the unique nature and the formation mechanism of this new junction. Here, we review the initiation and the history of understanding the a-B/c-Si interface (henceforth called the “boron-silicon junction”), as well as its importance for the microelectronics industry, followed by the scientific perception of the new junctions. Future developments and possible research directions are also discussed.

Recently, we have experimentally demonstrated the generation of mW average power, in the 100-600GHz bandwidth, by photoconductive sources using a connected array of dipoles coherently fed via a free-standing micro-lens array. In this contribution, we extend these sources to a much wider bandwidth reaching 5THz, without compromising the radiated power, by resorting to a tight array periodicity of 15Ϝm between the array elements and the use of an integrated 3D-printed micro-lens array to focus the laser power.

Silicon carbide (SiC) ceramic membranes are of particular significance for wastewater treatment due to their mechanical strength, chemical stability, and antifouling ability. Currently, the membranes are prepared by SiC-particle sintering at a high temperature. The production suffers from long production time and high costs. In this paper, we demonstrated a more economical way to produce SiC ultrafiltration membranes based on low-pressure chemical vapor deposition (LPCVD). SiC was deposited in the pores of alumina microfiltration supports using two precursors (SiH₂Cl₂ and C₂H₂/H₂) at a relatively low temperature of 750 °C. Different deposition times varying from 0 to 150 min were used to tune membrane pore size. The pure water permeance of the membranes only decreased from 350 Lm⁻²h⁻¹bar⁻¹ to 157 Lm⁻²h⁻¹bar⁻¹ when the deposition time was increased from 0 to 120 min due to the narrowing of membrane pore size from 71 to 47 nm. Increasing the deposition time from 120 to 150 min mainly resulted in the formation of a thin, dense layer on top of the support instead of in the pores. Oil-in-water emulsion filtration experiments illustrated that both the reversible and irreversible fouling of the SiC-deposited UF membrane was considerably lower as compared to the pristine alumina support. The unique feature that pore sizes decrease linearly as a function of SiC deposition time creates opportunities to produce low-fouling SiC membranes with tuned pore sizes on relatively cheap support.

Recently, powerful, reliable and cost-effective THz radiation photoconductive-emitters have been developed, providing up to 1mW of pulsed power in the range of frequencies between 0.1 and 0.7THz. In this paper we study the potential use of such sources for future pulsed radar systems aiming at stand-off imaging applications. Specifically, we investigate the image frame rate and Signal to Noise Ratio budget that can be obtained using these photoconductive sources. It emerges that adopting a receiving array of 14 times 14 simeq 200 elements, a 3D image with a Field of View (FoV) of 6cm times 6cm times 100cm and resolution of 4mm times 4mm times 1mm can be generated in 80Hz with a SNR { min}= 30dB, including realistic quasi-optical channel efficiencies.