The 1st EuNetAir Air Quality Joint Intercomparison Exercise organized in Aveiro (Portugal) from 13th–27th October 2014, focused on the evaluation and assessment of environmental gas, particulate matter (PM) and meteorological microsensors, versus standard air quality reference methods through an experimental urban air quality monitoring campaign. The IDAD-Institute of Environment and Development Air Quality Mobile Laboratory was placed at an urban traffic location in the city centre of Aveiro to conduct continuous measurements with standard equipment and reference analysers for CO, NOx, O3, SO2, PM10, PM2.5, temperature, humidity, wind speed and direction, solar radiation and precipitation.The comparison of the sensor data generated by different microsensor-systems installed side-by-side with reference analysers, contributes to the assessment of the performance and the accuracy of microsensor-systems in a real-world context, and supports their calibration and further development.The overall performance of the sensors in terms of their statistical metrics and measurement profile indicates significant differences in the results depending on the platform and on the sensors considered. In terms of pollutants, some promising results were observed for O3 (r2: 0.12–0.77), CO (r2: 0.53–0.87), and NO2 (r2: 0.02–0.89). For PM (r2: 0.07–0.36) and SO2 (r2: 0.09–0.20) the results show a poor performance with low correlation coefficients between the reference and microsensor measurements. These field observations under specific environmental conditions suggest that the relevant microsensor platforms, if supported by the proper post processing and data modelling tools, have enormous potential for new strategies in air quality control

We report a new hybrid sensor in which an ultrathin polypyrrole (PPy) layer is deposited on the CVD-grown graphene (G) by electropolymerization. The sensor exhibits an excellent performance in the selective sensing of ammonia (NH ₃ ) at room temperature, having a high, fast, and reversible response. It also shows rather good stability, reproducibility, and immunity to humidity. These performances are attributed to the synergistic effect between the PPy layer and G. Specifically, the NH ₃ molecules are adsorbed on the PPy layer, electrons transfer from NH ₃ to the PPy layer, changing the PPy layer resistance. Electrons can also be transferred to the G through the ultrathin PPy layer, in certain way changing the G resistance. These promote the sensor sensitivity. Moreover, the ultrathin PPy layer with porous nature plays an important role in the sensor response, selectivity, and immunity to humidity. Graphene is not only a support material for PPy electropolymerization but also provides an efficient pathway for electron transfer, thereby, accelerating the sensor response and recovery. Our research indicates that the combination of PPy and G is a very promising as a chemical sensor material. We implement a smart prototype with the present sensor in an electronic board for real-time monitoring the NH ₃ concentrations. The smart prototype can be connected to a computer by a USB port for demonstrating NH ₃ concentrations, transmitting the data and analyzing the sensor response curves. Our results are beneficial forward the commercial design and fabrication of sensors fulfilling the specifications of practical applications.

In this work, hydrogen (H) plasma treatment is implemented to dope indium gallium zinc oxide (InGaZnO), zinc oxide (ZnO), and indium oxide (In₂O₃) thin-film transistors (TFTs). We systematically analyze the active defect states inside these n-type metal oxides and reveal how they are impacted by H dopant incorporation, combining the device transfer characteristics (including the threshold voltage, subthreshold slope, and carrier mobility), the X-ray photoelectron spectra, and numerical and theoretical investigations. An increase of the field-effect mobility of these TFTs is mainly attributed to the decreased interface and bulk tail-distributed traps, after an appropriate amount of H dopants is incorporated. In ZnO, hydrogen exclusively acts as a shallow donor during the plasma treatment, while the zinc vacancies Zn(Vac) cannot be passivated by the H dopants as no improvement of the subthreshold slope (SS) is observed in the hydrogenated ZnO TFT. The H interstitials (H_i) incorporated into In₂O₃ are stable in the + charge state at equilibrium, then change into the − charge state as the Fermi level energy E_F gets closer to the bottom of the conduction band. Due to the H insertion into an oxygen vacancy V_O, the V_OH complex (acting as an acceptor) is formed in InGaZnO with increased H plasma treatment duration, leading to the degraded SS. This paper clarifies the H dopants’ role and the different dominant defects inside the three types of TFTs, which may benefit systematic understanding and exploration of H dopant incorporation into InGaZnO, ZnO and In₂O₃ films for TFT improvement and optimization.

We present an ultra-thin lateral SOI PIN photodiode with transferred monolayer graphene as the transparent gate, to provide enhanced ultraviolet (UV) performance and mechanical flexibility beyond standard Si-based devices. The device dark current shows intact characteristics after the post-CMOS thinning and graphene transfer processing steps. The device responsivity presents high potential in UV and visible wavelength detections (i.e. within the 200–900 nm range) under monochromatic light illumination. A maximum responsivity of 0.18 A W ⁻¹ has been experimentally achieved at 390 nm wavelength and validated by simulation, for a diode with intrinsic length L _i of 20 μ m. Additionally, the ~5 μ m-thick device chip with direct board assembly paves the way towards the development of hybrid flexible electronics.

We present a novel ultrathin avalanche photodiode (APD) with a silicon (Si) body thickness of 640 nm and optimized doping profiles to significantly improve the detection efficiency in ultraviolet (UV) spectral range from near UV (NUV) to UV-C (here studied down to 275 nm). The square photodiode is fabricated on silicon-on-insulator (SOI) substrate with an active area of 420 μm² (37 μm x 37 μm) consisting of n⁺⁺/p-well and an n-well guard ring (GR). The dark current-voltage (I-V) characteristic exhibits low leakage current (≈pA) and breakdown voltage of 8.6 V. A peak quantum efficiency (QE) of 93.88% is obtained on a wavelength of 400 nm at 4 V. An outstanding expansion of the sensitivity in UV-C is presented with a QE of 82.75% under a wavelength of 275 nm at 4 V. With a gain value of 4.9, a responsivity of 14.46 A/W at a wavelength of 400 nm on a low-level light intensity of 3.28 μW/cm² is achieved at 7.8 V. A sufficient detection performance in visible spectral range has also been achieved due to the formation of the sandwiched thin silicon body between nearly 200-nm SiO₂ on top and 1-μm buried SiO₂ (BOX). This proposed ultrathin photodiode indicates a potential high avalanche gain (>10⁵) in Geiger mode.