The 2-D graphene holds enormous potential as a future candidate for gas sensors, not only coming from its vast surface area but also contributed by the highly active edges, which have promptly become a research hotspot. In this work, we developed a novel transferfree approach to prepare chemical vapor deposited edgeexposed multilayer graphene micromeshes by prepatterning the molybdenum (Mo) catalyst through photolithography. Our facile and efficient approach provides fewer steps, higher accuracy, and virtually unrestricted patternable features. It is also semiconductor manufacturing compatible with precise alignment and positioning for wafer-scale mass production. Graphene micromeshes with different thicknesses were prepared and studied for NO2 (∼1 ppm) gas sensing. Despite the reduction in the surface area, the micromeshes still delivered an enhancement of the overall response [for 20-min chemical vapor deposition (CVD) graphene, from 0.692% to 0.744%]. Based on our proposed calculation model, which hypothetically separates the response from the surface and edges, thinner multilayer graphene edges exhibited exceptionally high sensitivity compared with the surface due to higher reactivity and edge-facilitated gas adsorption. Our prepatterning method and study of graphene micromesh-based prototype gas sensors provide insights into the role of the edges of multilayer graphene, which could potentially be a vital part for future high-performance gas sensors.

Studying the polarization and spectral distortion of the cosmic microwave background (CMB) in tandem with intensity fluctuations of the cosmic infrared background allows us to verify our assumptions on cosmic inflation and investigate the dynamics and evolution of galaxy clusters in the past 10 billion years. Because of its broadband emission and being an all-sky extended source, observing the entire CMB in detail is a very time-consuming and expensive exercise. Fortunately, in the past few years, the on-chip superconducting spectrometer technology has moved out of the lab and into the telescope. With its compact size and background-limited sensitivity, this family of instruments is particularly well-suited for fast and large area observations in a relatively unexplored range of the electromagnetic spectrum. However, recent examples of this technology do not yet reach the requirements needed for large spectroscopic and polarimetric surveys of the CMB. We formulate several of these requirements and introduce novel on-chip components and fabrication techniques. We introduce a crossover to enable distinguishing signal polarization, minimize signal loss by locally optimized lithography of a coplanar waveguide, lower the spectral resolution of microstrip filters by deposition of a dielectric layer, and increase the yield of the spectrometer array by removing individual line shorts. These together have culminated in the successful fabrication of a 14-spaxel integral field unit.

The development of gas sensors with high sensitivity and reliable response characteristics is essential for detecting volatile organic compounds (VOCs) such as ethanol in industrial, medical, and environmental applications. Carbon nanotubes (CNTs) are promising materials for gas sensing due to their outstanding electrical, mechanical, and chemical properties; however, their practical performance is often limited by low response levels toward specific gases. In this study, CNTs were hybridized with titanium dioxide (TiO₂) to enhance their sensing performance toward ethanol. In addition, the influence of different metal electrodes on the sensing behavior of CNT-TiO₂ hybrid sensors was systematically investigated. The results show that TiO₂ hybridization significantly enhances the sensitivity of CNT-based sensors to ethanol, while the choice of electrode material strongly affects the electrical behavior and gas response characteristics. Although most electrodes primarily influence the response magnitude, certain electrodes, such as aluminum, exhibit distinctive response features. Furthermore, analysis of response and recovery times reveals notable electrode-dependent variations with no direct correlation to sensitivity, indicating that dynamic parameters provide complementary information. These findings highlight the potential of electrode engineering and multi-parameter response analysis to enhance response differentiation and support future gas discrimination strategies in CNT-TiO₂-based sensing platforms.

In this work, we demonstrate the use of a micro-hotplate (MHP) with graphene integrated without transfer step for NO₂ sensing. The MHP can rapidly recover the device to its initial conditions by applying a brief heat pulse. Moreover, by employing a process without graphene transfer, we prevent random polymer contamination from the transfer process. The (up to 8) graphene sensors on a single MHP show a very similar response. Finally, we demonstrate that we can extract the relative humidity from the device's response immediately after the MHP is turned off in a humid environment.

Low-loss deposited dielectrics are beneficial for the advancement of superconducting integrated circuits for astronomy. In the microwave band (approximately 1-10 GHz) the dielectric loss at cryogenic temperatures and low electric field strengths is dominated by two-level systems. However, the origin of the loss in the millimeter-submillimeter band (approximately 0.1-1 THz) is not understood. We measured the loss of hydrogenated-amorphous-SiC films in the 0.27-100-THz range using superconducting-microstrip resonators and Fourier-transform spectroscopy. The agreement between the loss data and a Maxwell-Helmholtz-Drude dispersion model suggests that vibrational modes above 10 THz dominate the loss in hydrogenated amorphous SiC above 200 GHz.

Depending on the applications based on graphene, single-layer or few-layer graphene would be more beneficial. Ideally, graphene could be nucleated directly with the required thickness. However, some aspects related to graphene thickness and uniformity control still need to be solved. This work aims to better understand graphene formation using Mo thin films as a catalyst. The grown graphene films were characterized using SEM, TEM, XPS, AFM, standard Raman spectroscopy and 3D Raman surface imaging. A correlation between the catalyst thickness and the number of layers is established. All the characterization techniques show that the number of graphene layers inversely scales with the Mo catalyst thickness used for the graphene synthesis. Then, by simply adjusting the catalyst thickness, the number of graphene layers can be engineered from few-layer graphene (FLG) up to multi-layer graphene (MLG). A pinhole distribution of 1 % was detected on the films synthesized on 50 nm and 100 nm Mo thicknesses after the catalyst was etched. On the synthesized FLG (500 nm Mo), no holes were observed on the surface film after the etching process and even after a transfer onto another substrate. These results can enable the formation of FLG with a controlled thickness and good uniformity.

The term graphene-based gas sensors may be too broad, as there are many physicochemical differences within the graphene-based materials (GBM) used for chemiresistive gas sensors. These differences condition the sensitivity, selectivity, recovery, and ultimately the sensing performance of these devices towards air pollutants. Continuous ultraviolet irradiation aids in the desorption of gas molecules and enhances sensor performance. Under these conditions, the devices from this work can reliably monitor NO₂ and CO at room temperature, below the human-recommended exposure limits, presenting NO₂ LoD down to ∼20 ppb. By selecting GBMs with different levels of defectivity, which influence gas adsorption dynamics, and through comprehensive characterization, including D, D′, D″, 2D, and G Raman bands, graphene-based gas sensors can be tailored to meet specific sensing requirements. This study examines five different non-oxidized GBM to develop tools and gain a deeper understanding of the relationships between GBM properties and their sensing performance. This research introduces a new standard for defect assessment, moving beyond graphene's D and G Raman band intensity ratio, to facilitate the successful integration of graphene-based gas sensors into everyday applications, such as environmental monitoring and industrial safety, and potentially impacting other 2D materials, thereby reducing health risks associated with air pollution.

This work reports, for the first time, the use of spark ablation with impaction printing to selectively deposit silver (Ag) and gold (Au) nanoparticle (NP) functionalization on single-layer graphene (SLG) based gas sensors. This method avoids lithography and chemical processes, maintaining the device's quality while potentially lowering the fabrication costs. Ag-decorated sensors reveal a three-fold improvement in nitrogen dioxide (NO₂) gas response over pristine-SLG sensors. We demonstrate detection capabilities down to 50 ppb at room temperature, negating the requirement for external thermal or photoactivation. In contrast to pristine or Au-decorated SLG sensors, Ag-decorated devices exhibit 96% recovery at room temperature (RT). These results highlight the potential of using spark ablation with impaction printing for functionalizing graphene-based sensors.

Integrated circuits based on wide bandgap semiconductors are considered an attractive option for meeting the demand for high-temperature electronics. Here, we report an analog-to-digital converter fabricated in a silicon carbide complementary metal-oxide-semiconductor technology now available through Europractice. The MOSFET component in this technology was measured up to 500 °C, and the key parameters, such as threshold voltage, field-effect mobility, and channel-length modulation parameters, were extracted. A 4-bit flash data converter, consisting of 266 transistors, is implemented with this technology and demonstrates correct operation up to 400 °C. Finally, the gate oxide quality is investigated by time-dependent dielectric breakdown measurements at 500 °C. A field-acceleration factor of 4.4 dec/(MV/cm) is obtained by applying the E model.

Silicon carbide (SiC) is recognized as an excellent material for microelectromechanical systems (MEMS), especially those operating in challenging environments, such as high temperature, high radiation, and corrosive environments. However, SiC bulk micromachining is still a challenge, which hinders the development of complex SiC MEMS. To address this problem, we present the use of a carbon nanotube (CNT) array coated with amorphous SiC (a-SiC) as an alternative composite material to enable high aspect ratio (HAR) surface micromachining. By using a prepatterned catalyst layer, a HAR CNT array can be grown as a structural template and then densified by uniformly filling the CNT bundle with LPCVD a-SiC. The electrical properties of the resulting SiC-CNT composite were characterized, and the results indicated that the electrical resistivity was dominated by the CNTs. To demonstrate the use of this composite in MEMS applications, a capacitive accelerometer was designed, fabricated, and measured. The fabrication results showed that the composite is fully compatible with the manufacturing of surface micromachining devices. The Young’s modulus of the composite was extracted from the measured spring constant, and the results show a great improvement in the mechanical properties of the CNTs after coating with a-SiC. The accelerometer was electrically characterized, and its functionality was confirmed using a mechanical shaker. (Figure presented.)

The authors regret that in the above article the Fig. 3 contains an error of cross-section image of group C at 48 h on Page 4. Fig. 3 should read: This correction does not influence the method, results and conclusions of the original article. The authors would like to apologise for any inconvenience caused.

Synchronized rectifiers offer promising solutions for piezoelectric energy harvesting; however, achieving the promised energy extraction performance necessitates using either a bulky inductor or multiple large capacitors, which cannot be on-chip integrated and increase the system form factor. This article introduces a fully integrated sequenced synchronized switch harvesting on capacitors (3SHC) rectifier. The input piezoelectric transducer (PT) uses microelectromechanical system technology. The cantilever is equally split into multiple strongly coupled subcantilevers, with each cantilever treated as an individual PT connected to the proposed rectifier. The 3SHC rectifier cyclically operates multiple times to synchronously flip the voltage of each cantilever sequentially. With the proposed design, all the flying capacitors only need to match the capacitance of each subcantilever; hence, they can be fully integrated on-chip. The design is fabricated using standard 0.18 μ m CMOS technology. Measurement results show that the proposed 3SHC rectifier attains an 80% voltage flip efficiency and achieves a 730% power enhancement compared to a full-bridge rectifier.

Suspended drums made of 2D materials hold potential for sensing applications. However, the industrialization of these applications is hindered by significant device-to-device variations presumably caused by non-uniform stress distributions induced by the fabrication process. Here, we introduce a methodology to determine the stress distribution from their mechanical resonance frequencies and corresponding mode shapes as measured by a laser Doppler vibrometer (LDV). To avoid limitations posed by the optical resolution of the LDV, we leverage a manufacturing process to create ultra-large graphene drums with diameters of up to 1000 μm. We solve the inverse problem of a Föppl–von Kármán plate model by an iterative procedure to obtain the stress distribution within the drums from the experimental data. Our results show that the generally used uniform pre-tension assumption overestimates the pre-stress value, exceeding the averaged stress obtained by more than 47%. Moreover, it is found that the reconstructed stress distributions are bi-axial, which likely originates from the transfer process. The introduced methodology allows one to estimate the tension distribution in drum resonators from their mechanical response and thereby paves the way for linking the used fabrication processes to the resulting device performance.

This study explores the application of a novel transfer-free method for the synthesis of multilayer Chemical Vapour Deposition (CVD) graphene directly on transparent sub-strates, specifically to create transparent Microelectrode Arrays (MEAs) for optogenetic studies. Traditional methods typically involve a graphene transfer step that can compromise the material's integrity and electrical properties. By eliminating this step, our approach simplifies the fabrication process. The developed MEAs were characterised by Raman spectroscopy, op-tical transmittance, and electrochemical impedance spectroscopy. We also assessed the stability and recording capabilities of the fabricated MEAs, alongside a comparative assessment with a commercial MEA. Turbostratic graphene grown directly on quartz and sapphire was successfully achieved. Our transfer-free MEAs exhibit promising signal detection capabilities, despite a relatively high baseline noise of ∼ 23μ V. and a significantly large impedance at 1 kHz (3.2 to 9.89 M Ω) surpassing values in other studies. The devices exhibited low stability after exposure to liquid media during the soaking and ageing tests, causing large variations in the electrochemical measurements post-exposure. This was due to the permeability of the encapsulation layer and the biodegradability of the molybdenum structures, which led to significant structural and chemical changes in the devices. While further work is required to prevent the failure mechanisms of the device, this study demonstrates the feasibility of transparent MEA fabrication by means of a transfer-free approach directly on quartz substrates.