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Selective growth of 2D MoS2 layers on patterned substrates is highly desired for easy fabrication of devices. Selectively grown 2D MoS2 on Mo patterned substrates for the formation of intimate metallic contact was obtained by a Mo-CVD method in which MoO2 from an oxidized Mo pattern and S powder are the growth precursors. Mo films were deposited by magnetron sputtering on SiO2(300 nm)/c-Si substrates and patterned by photolithography techniques for obtaining Mo strips and finger contact structures, with the gap between the strips and finger varied from 5 to 20 μm. The filling of the gap by selectively grown atomically thin MoS2 plates of 1–2 monolayers (MLs) was demonstrated by scanning electron microscopy and atomic force microscopy imaging. Field effect devices for the characterization of the photosensitivity of selectively grown MoS2 have been fabricated from finger contact structures. The dark current is drastically reduced from 10–9 to 10–13–10–14 A by varying the gate voltage from +7 to −7 V, showing the n-type semiconductor behavior of the selectively grown 2D MoS2. High photosensitivity of 105 (%) was obtained for 4.5 × 10–4 mW/cm2 at 650 nm wavelength illumination. The spectral responsivity reaches values of 15–25 A/W at 600 nm wavelength and shows an energy onset of 1.72–1.77 eV corresponding to about 2 ML MoS2. The carrier-trapping effect responsible for the slow part of the device response can be caused by structural defects and also by adsorbed molecules like in gas sensors. [ABSTRACT FROM AUTHOR]

SiGeSn nanocrystals (NCs) in oxides are of considerable interest for photo-effect applications due to the fine-tuning of the optical bandgap by quantum confinement in NCs. We present a detailed study regarding the silicon germanium tin (SiGeSn) NCs embedded in a nanocrystalline hafnium oxide (HfO2) matrix fabricated by using magnetron co-sputtering deposition at room temperature and rapid thermal annealing (RTA). The NCs were formed at temperatures in the range of 500–800 °C. RTA was performed to obtain SiGeSn NCs with surfaces passivated by the embedding HfO2 matrix. The formation of NCs and β-Sn segregation were discussed in relation to the deposition and processing conditions by employing HRTEM, XRD and Raman spectroscopy studies. The spectral photosensitivity exhibited up to 2000 nm in short-wavelength infrared (SWIR) depending on the Sn composition was obtained. Comparing to similar results on GeSn NCs in SiO2 matrix, the addition of Si offers a better thermal stability of SiGeSn NCs, while the use of HfO2 matrix results in better passivation of NCs increasing the SWIR photosensitivity at room temperature. These results suggest that SiGeSn NCs embedded in an HfO2 matrix are a promising material for SWIR optoelectronic devices. [ABSTRACT FROM AUTHOR]

Drinking water produced in water treatment plants almost invariably fulfils the water quality requirements set, for example by the European Union Drinking Water Directive 98/83/EC (EU DWD) and national legislation. However, EU DWD requires that water quality should also meet the requirements at the consumers' tap. The quality of drinking water changes due to the transportation through the distribution networks and the time spent in the reservoirs until the last point of consumption. Water companies face major problems related to the quality of the drinking water at consumers' tap, even if they invest important financial resources for catchments, treatment and disinfection. Aesthetic and organoleptic problems are the main reasons for customers to complain about the water quality supplied. Turbidity is one of the quality indicators causing most of the water quality problems. Nowadays, modern water management must tackle in an integrated way the law requirements and the new technologies and instruments which help water companies identify the cause of any events occurring in the supply networks, in terms of real-time monitoring. These problems are also valid for Iasi County, situated in the North-Eastern part of Romania, where water supply and wastewater treatment are managed by SC Apavital SA, a county-wide public-owned company which has the task of providing high-quality water and related services for customers, while complying with strict regulations. This study presents the application of an on-line monitoring system for real-time, continuous monitoring of turbidity in the Iasi city distribution network, as well as the efficiency of on-line turbidimeters for water quality monitoring in the effluent of the treatment plant and for water quality changes in the distribution system. By evaluating the data gathered during the on-line monitoring of turbidity for this case study, it is possible to detect abrupt changes in water quality and thus to react to any disturbances in the system by adequate corrections in the treatment stages. [ABSTRACT FROM AUTHOR]

The development of short-wave infrared (SWIR) photonics based on GeSn alloys is of high technological interest for many application fields, such as the Internet of things or pollution monitoring. The manufacture of crystalline GeSn is a major challenge, mainly because of the low miscibility of Ge and Sn. The use of embedded GeSn nanocrystals (NCs) by magnetron sputtering is a cost-effective and efficient method to relax the growth conditions. We report on the use of GeSn/SiO 2 multilayer deposition as a way to control the NC size and their insulation. The in situ prenucleation of NCs during deposition was followed by ex situ rapid thermal annealing. The nanocrystallization of 20×(11nm_Ge 0.865 Sn 0.135 /1.5nm_SiO 2 ) multilayers leads to formation of GeSn NCs with ∼16% Sn concentration and ∼9 nm size. Formation of GeSn domes that are vertically correlated contributes to the nanocrystallization process. The absorption limit of ∼0.4 eV in SWIR found by ellipsometry is in agreement with the spectral photosensitivity. The ITO/20×(GeSn NC/SiO 2 )/p-Si/Al diodes show a maximum value of the SWIR photosensitivity at a reverse voltage of 0.5 V, with extended sensitivity to wavelengths longer than 2200 nm. The multilayer diodes have higher photocurrent efficiency compared to diodes based on a thick monolayer of GeSn NCs.