With its remarkable electro-thermal properties such as the highest known thermal conductivity (~22 W cm−1∙K−1 at RT of any material, high hole mobility (>2000 cm2 V−1 s−1), high critical electric ...field (>10 MV cm−1), and large band gap (5.47 eV), diamond has overwhelming advantages over silicon and other wide bandgap semiconductors (WBGs) for ultra-high-voltage and high-temperature (HT) applications (>3 kV and >450 K, respectively). However, despite their tremendous potential, fabricated devices based on this material have not yet delivered the expected high performance. The main reason behind this is the absence of shallow donor and acceptor species. The second reason is the lack of consistent physical models and design approaches specific to diamond-based devices that could significantly accelerate their development. The third reason is that the best performances of diamond devices are expected only when the highest electric field in reverse bias can be achieved, something that has not been widely obtained yet. In this context, HT operation and unique device structures based on the two-dimensional hole gas (2DHG) formation represent two alternatives that could alleviate the issue of the incomplete ionization of dopant species. Nevertheless, ultra-HT operations and device parallelization could result in severe thermal management issues and affect the overall stability and long-term reliability. In addition, problems connected to the reproducibility and long-term stability of 2DHG-based devices still need to be resolved. This review paper aims at addressing these issues by providing the power device research community with a detailed set of physical models, device designs and challenges associated with all the aspects of the diamond power device value chain, from the definition of figures of merit, the material growth and processing conditions, to packaging solutions and targeted applications. Finally, the paper will conclude with suggestions on how to design power converters with diamond devices and will provide the roadmap of diamond device development for power electronics.
While core–shell wire-based devices offer a promising path toward improved optoelectronic applications, their development is hampered by the present uncertainty about essential semiconductor ...properties along the three-dimensional (3D) buried p–n junction. Thanks to a cross-sectional approach, scanning electron beam probing techniques were employed here to obtain a nanoscale spatially resolved analysis of GaN core–shell wire p–n junctions grown by catalyst-free metal–organic vapor phase epitaxy on GaN and Si substrates. Both electron beam induced current (EBIC) and secondary electron voltage constrast (VC) were demonstrated to delineate the radial and axial junction existing in the 3D structure. The Mg dopant activation process in p-GaN shell was dynamically controlled by the ebeam exposure conditions and visualized thanks to EBIC mapping. EBIC measurements were shown to yield local minority carrier/exciton diffusion lengths on the p-side (∼57 nm) and the n-side (∼15 nm) as well as depletion width in the range 40–50 nm. Under reverse bias conditions, VC imaging provided electrostatic potential maps in the vicinity of the 3D junction from which acceptor N a and donor N d doping levels were locally determined to be N a = 3 × 1018 cm–3 and N d = 3.5 × 1018 cm–3 in both the axial and the radial junction. Results from EBIC and VC are in good agreement. This nanoscale approach provides essential guidance to the further development of core–shell wire devices.
Abstract
The Scol’air-FR project is issued from the need to establish an inventory of indoor air quality conditions in primary schools of the canton of Fribourg, Switzerland. In Fribourg, the ...official trend is to promote mechanical ventilation systems in schools to ensure a good air quality. A properly designed, built, commissioned, and operated mechanical ventilation system should be able to deliver the anticipated flow rate, regardless of who uses it - the only person involved being the person responsible for ventilation system operation. In some cases, however, the expected objectives are not achieved. This similar observation applies to natural ventilation. A good ventilation concept, properly implemented and operated, should also achieve the same objective if the outdoor air quality is good. The aim of this article is to identify differences, in terms of indoor air quality and well-being, between naturally and mechanically ventilated schools. Moreover, we expect to identify if trends are attributable to the operation of ventilation systems or to occupant behaviours. We observed lower carbonic gas levels in building equipped with mechanical ventilation systems. This finding can be extended to VOCs and relative humidity. We also identified different and recurrent issues among the different mechanical ventilation systems. Our results highlight issues measured in buildings equipped by mechanical ventilation systems are mostly related to the balance of the system, while in natural ventilation systems, IAQ related issues are mainly due to the present context and its influences on occupants’ behaviour.
Metal Oxide Semiconductor capacitors were fabricated using p-type O-terminated (001) diamond and zirconium dioxide deposited by atomic layer deposition at low temperature (100 °C). X-ray diffraction ...and transmission electron microscopy evidence monoclinic structure and polycrystalline nature of the oxide layer. I-V, CV and CF experiments have been performed in a large frequency range, i.e. from 1 Hz to 1 MHz, in order to analyse the electrical properties of the metal/dielectric/diamond stack. The presence of charges in the oxide and interface states induces a flat-band voltage shift in the CV curve and a strong Fermi level pinning effect. A leakage current mechanism considering the correlation of the microstructural characterization and the electrical response is proposed.
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•Electrical characterization of ZrO2/diamond MOS capacitors•ZrO2 microstructure and defects characterization•Band diagram model to explain the device electrical behaviour
MULTI-SOURCE POINT CLOUD SEMANTIC SEGMENTATION USING NEURAL NETWORK Montlahuc, J.; Polette, A.; Tahan, A. ...
International archives of the photogrammetry, remote sensing and spatial information sciences.,
05/2022, Letnik:
XLIII-B3-2022
Journal Article, Conference Proceeding
Recenzirano
Odprti dostop
The purpose of this study is to enhance point cloud semantic segmentation by using point clouds from multiple distinct technologies on the same capture location and to determine whether employing ...various technologies throughout the acquisition process yields better performance during classification. The different point clouds were captured in the same geographical location and have previously been aligned and classified by professionals of the field. Three locations have been scanned with airborne lidar, terrestrial lidar and photogrammetry using UAV or helicopter. The use of various sources of capture on the same location opens the door to creating new features, such as the proportion of each source involved in the semantic segmentation of point clouds. This plurality of sources also enables us to spread various features, such as RGB colors, that have been propagated to other sources via the neighborhood. The initial results lean towards capture using different technologies as the overall accuracy increase by two to four points and the mean Matthews correlation coefficient increase by four to seven points. The main drawbacks are the cost of some technologies, as well as the processing time, which is greater than with a single technology.
Abstract
Radon is a natural radioactive gas that may cumulate in indoor environments. The impacts of weather events on indoor radon concentration had been explored in different places around the ...world but only marginally in Switzerland. Using basic statistical analysis, this study investigates different meteorological parameters’ influence on indoor radon concentrations and shows that outdoor air temperature is the most influential beyond others. Finally, this paper highlights the importance of radon dynamic in buildings, a topic often overlooked by construction professionals and the broader public in Switzerland.
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