Highly improved responsivity of self-powered UV–Visible photodetector based on TiO2/Ag/TiO2 multilayer deposited by GLAD technique: Effects of oriented columns and nano-sculptured surface

International audienceThe outstanding progress made in optoelectronic technologies calls for a renewed performance assessment of photodetectors (PDs) for next-generation sensing applications. Here, TiO2/Ag/TiO2 tri-layered films were sputtered using the GLancing Angle Deposition (GLAD) technique in which the deposition angle was varied from 0 to 80°. Before the elaboration, a strategic combination of Genetic Algorithm (GA) and numerical analysis was used to find out the best multilayer geometry offering superior optical performance. The influence of the inclinedarchitecture on the performance of the prepared TiO2/Ag/TiO2 multilayer was analyzed. Optical characterization reveals that near-perfect UV photodetection and over than 60% of visible-absorbance were achieved by taking a deposition angle of 80°. These enhancements are correlated to the surface nano-sculptured structures, which gives rise to an enhanced light-trapping capability. The measured I-V curves of the obliquely-deposited structures showed a clear photovoltaic mode and an extremely low dark current of a few picoamperes. Besides, the devices demonstrate an enhanced self-powered UV–Vis photoresponse, yielding superb UV and visible responsivity of 0.2A/W and 47 mA/W, respectively. The UV, blue, and green current ratios were respectively 137, 113, and 107 dB. Therefore, promoting efficient light management, this innovative concept of inclined tri-layer films provides a sound pathway for designing potential alternative self-powered UV–Vis PDs appropriate for the future development of the optoelectronic technology

Tunable band-selective photodetector based on sputter-deposited SnOx thin-films: Effect of reactive gas pulsing process

International audienceIn this work, high-performance SnOx band-selective photodetectors(PDs) were realized by DC magnetron sputtering technique. Thereactive gas pulsing process (RGPP) was implemented with pulsingperiod fixed at P = 20 s to adjust tin and oxygen concentrations inthe film. The impact of pulsed oxygen time on the structural,morphological and photosensing properties of SnOx-based PDs wasinvestigated. The fabricated SnOx-based PD at a high duty cycle of80% of P demonstrated high UV photodetection capabilities andsolar-blind characteristic with a high responsivity of 21.8 mA/W, ahigh signal to noise ratio of 6×104 and a specific detectivity ofabout 5×1011 Jones. It was also revealed that the use of a shortoxygen pulsing time 8 s paves the way for the realization ofmultispectral SnOx PD, demonstrating a high responsivity values of36.45 mA/W, 36.4 mA/W and 34 mA/W over UV, Visible and NIR bands,respectively. This is attributed to the role of using RGPP inmodulating the film optoelectronic properties from metallic toinsulator when the duty cycle and thus oxygen concentration in thefilms changed from pure tin to overstoichiometric SnO2 compound.The prepared SnOx PDs demonstrated many advantageous features likelow-noise, cost effective and high sensitivity. The obtainedresults proved that SnOx can be used as an alternative material fordeveloping high-performance band-selective sensing devices

Highly sensitive, ultra-low dark current, self-powered solar-blind ultraviolet photodetector based on ZnO thin-film with an engineered rear metallic layer

International audienceIn this paper, novel self-powered, solar-blind UV photodetector (PD) designs based on a ZnO thin-film with engineered back metal layer (BML) were fabricated by RF magnetron sputtering and e-beam evaporation techniques. An exhaustive study concerning the impact of dissimilar BML (Au and Ni) on the device structural, optical and electrical properties was carried out. The measured I–V curves illustrated an asymmetrical behavior, enabling a clear and distinctive photovoltaic mode. Superb sensitivity of 107, high ION/IOFF ratio of 149dB, ultralow dark-noise current less than 11pA and responsivity exceeding 0.27A/W were reached for the prepared ZnO-based UV-PDs in self-powered mode. The role of the engineered BML in promoting effective separation and transfer of the photo-induced carriers was discussed using the band-diagram theory. The influence of the annealing process on the UV-sensor performance was also investigated. The annealed device at 500°C demonstrated a lower dark current of a few picoamperes and a high rejection ratio of 2.2:103, emphasizing its exciting visible blindness characteristics. Therefore, the use of an engineered BML with optimized annealing conditions open up new perspectives to realizing high-performance, self-powered solar-blind UV-PDs based on simple thin film-ZnO structure strongly desirable for various optoelectronic applications

Mechanical response of

The mechanical behavior of few-layered borophene (η-LB), at different temperatures ranging from 10 to 800 K in conjunction with a variant strain-rate, is studied by employing molecular dynamics simulations based on the Stillinger-Weber potential. The uniaxial tensile deformations along the zigzag- and armchair-direction of the hexagonal lattice are considered for η-LB, with η = 1, 2, 3, 4. We find an extremely anisotropic mechanical response. Parameters such as Young’s modulus and fracture strength are higher along the armchair-traction than the zigzag one due to the corrugated structure along the zigzag-axis. The fracture resistances of η-LB are strongly sensitive to temperature, while their dependence on the strain-rate is relatively low. The influence of nitrogen intercalation as well as vacancy defects on elastic behavior is also determined and discussed. The results are significantly affected by the defect’s type, concentration, and location. Our findings provide useful insights for the design of LB for many applications requiring a practical large magnitude strain engineering

Low incidence of SARS-CoV-2, risk factors of mortality and the course of illness in the French national cohort of dialysis patients

International audienceThe aim of this study was to estimate the incidence of COVID-19 disease in the French national population of dialysis patients, their course of illness and to identify the risk factors associated with mortality. Our study included all patients on dialysis recorded in the French REIN Registry in April 2020. Clinical characteristics at last follow-up and the evolution of COVID-19 illness severity over time were recorded for diagnosed cases (either suspicious clinical symptoms, characteristic signs on the chest scan or a positive reverse transcription polymerase chain reaction) for SARS-CoV-2. A total of 1,621 infected patients were reported on the REIN registry from March 16th, 2020 to May 4th, 2020. Of these, 344 died. The prevalence of COVID-19 patients varied from less than 1% to 10% between regions. The probability of being a case was higher in males, patients with diabetes, those in need of assistance for transfer or treated at a self-care unit. Dialysis at home was associated with a lower probability of being infected as was being a smoker, a former smoker, having an active malignancy, or peripheral vascular disease. Mortality in diagnosed cases (21%) was associated with the same causes as in the general population. Higher age, hypoalbuminemia and the presence of an ischemic heart disease were statistically independently associated with a higher risk of death. Being treated at a selfcare unit was associated with a lower risk. Thus, our study showed a relatively low frequency of COVID-19 among dialysis patients contrary to what might have been assumed