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Gas sensing properties of metal oxide semiconductors draw high attention due to their simple fabricating methods, and low cost, chemical, and physical properties. In general, a high bandgap (>2 eV) can cause them to react in the UV region through the electromagnetic spectrum. Controlling the UV-photodetection and gas sensing ability of MoO2-MoO3 thin film through tungsten (W) doping of different ratios have been reported here. The preparation of these films was grown using a reactive magnetron sputtering system with different power sputtering of W-content. The bandgap calculations showed that the samples have a wide bandgap value. A small particle size of 8nm was observed through high W doping concentration which enhanced these materials toward high efficient gas sensing and UV photodetector applications. The UV optical sensor exhibits a high responsivity value of 2500A/W and an external quantum efficiency (EQE) value of 5x109 at 365nm. Also, an increase in the photocurrent gain value with increasing the W amount with a maximum value of 0.13, while a photocurrent of 1mA was observed. On the other hand, a fast-response/recovery time-based CO2 gas sensor of less than 10 sec was observed. The thin-film sensors showed well-defined adsorption and desorption kinetics in a CO2 environment with a p-type chemisorption behavior., Metal oksit yarı iletkenlerin gaz algılama özellikleri, basit üretim yöntemleri ve düşük maliyeti, kimyasal ve fiziksel özellikleri nedeniyle büyük ilgi görmektedir. Genel olarak, yüksek bir bant aralığı (>2 eV), elektromanyetik spektrum yoluyla UV bölgesinde reaksiyona girmelerine neden olabilir. Farklı oranlarda tungsten (W) dopingi yoluyla MoO2-MoO3 ince filmin UV foto algılama ve gaz algılama yeteneğinin kontrol edilmesi burada rapor edilmiştir. Bu filmlerin hazırlanması, W içeriğinin farklı güç püskürtmeli reaktif magnetron püskürtme sistemi kullanılarak büyütüldü. Bant aralığı hesaplamaları, örneklerin geniş bir bant aralığı değerine sahip olduğunu göstermiştir. Bu malzemeleri yüksek verimli gaz algılama ve UV fotodetektör uygulamalarına doğru geliştiren yüksek W katkı konsantrasyonu yoluyla 8 nm'lik küçük bir parçacık boyutu gözlemlendi. UV optik sensör, 365nm'de 2500A/W'lik yüksek bir duyarlılık değeri ve 5x109'luk bir harici kuantum verimliliği (EQE) değeri sergiler. Ayrıca, 1mA'lık bir fotoakım olurken, maksimum 0.13 değerinde W miktarı arttıkça fotoakım kazanç değerinde bir artış gözlemlendi. Öte yandan, 10 saniyeden kısa bir hızlı yanıt/kurtarma süresine dayalı CO2 gaz sensörü gözlendi. İnce film sensörleri, p-tipi kimyasal adsorpsiyon davranışına sahip bir CO2 ortamında iyi tanımlanmış adsorpsiyon ve desorpsiyon kinetiği gösterdi.

This study was on the optoelectronic properties of multilayered two-dimensional MoS

Molybdenum - tungsten oxide (Mo1-xWxO3, x = 1, 0.8, and 0.6) nanostructured thin films-based room temperture (RT) gas sensors are prepared by means of reactive RF magnetron co-sputtering at 400 °C. The structural, morphology, topography, optical, and electrical characterizations of the prepared sensors are carried out by XRD Rietveld structure refinement analyses, SEM, AFM, UV-VIS spectrophotometer, and source meter. By controlling the deposition temperture of 400 °C, a co-existing phase of MoO3 and MoO2 in WO3 matrix is presented with high oxygen vacancies concentration as calculated from the XRD Rietveld Refinement analyses. By increasing the Mo content, the calculated oxygen vacancies concentration increases by factor of 1.36. The optical characterization of Mo0.2W0.8O3 thin film shows a high transparent of 99.6% at 500 nm. The prepared thin films have successfully tested to detect carbon dioxide (CO2) at RT (20 °C) with high selectivity and repeatability. The Mo0.4W0.6O3 sensor film shows an electrical Schottky contact with fast response and recovery times towards CO2 under UV light activation. Mo0.4W0.6O3 thin film under dark and UV conditions were able to detect low CO2 concentration of 2 and 0.5 sccm CO2 at RT, respectively. Under UV illumination, Mo0.4W0.6O3 film shows a fast response and recovery time of 6.53 and 8.05 s at 0.5 sccm with sensitivity of 29.19%. Under UV photonic activation, higher electron concentration is presented in the oxide surface, which leads to high probability for reaction with CO2 molecules, and consequently enhanced the chemisorption of CO2. The enhanced CO2 gas sensitivity and fast response may refer to the high oxygen vacancies concentration and the active role of the grain boundaries in MoO2, MoO3 and WO3 mixed-valence nanostructured under UV activation.

The application of the photonic superlattice in advanced photonics has become a demanding field, especially for two-dimensional and strongly correlated oxides. Because it experiences an abrupt metal-insulator transition near ambient temperature, where the electrical resistivity varies by orders of magnitude, vanadium oxide (VO

Ultrathin MoO3 semiconductor nanostructures have garnered significant interest as a promising nanomaterial for transparent nano- and optoelectronics, owing to their exceptional reactivity. Due to the shortage of knowledge about the electronic and optoelectronic properties of MoO3/n-Si via an ALD system of few nanometers, we utilized the preparation of an ultrathin MoO3 film at temperatures of 100, 150, 200, and 250 °C. The effect of the depositing temperatures on using bis(tbutylimido)bis(dimethylamino)molybdenum (VI) as a molybdenum source for highly stable UV photodetectors were reported. The ON–OFF and the photodetector dynamic behaviors of these samples under different applied voltages of 0, 0.5, 1, 2, 3, 4, and 5 V were collected. This study shows that the ultrasmooth and homogenous films of less than a 0.30 nm roughness deposited at 200 °C were used efficiently for high-performance UV photodetector behaviors with a high sheet carrier concentration of 7.6 × 1010 cm−2 and external quantum efficiency of 1.72 × 1011. The electronic parameters were analyzed based on thermionic emission theory, where Cheung and Nord’s methods were utilized to determine the photodetector electronic parameters, such as the ideality factor (n), barrier height (Φ0), and series resistance (Rs). The n-factor values were higher in the low voltage region of the I–V diagram, potentially due to series resistance causing a voltage drop across the interfacial thin film and charge accumulation at the interface states between the MoO3 and Si surfaces.

The aim of this research is to analyze the influence of various factors on the photo-ionization cross-section in (Al, Ga)N/AlN double triangular quantum wells. Using the finite difference method, the effects of the electric field, hydrostatic pressure, temperature, and Ga concentration were investigated within the effective mass and parabolic approximations. Our findings show that the photo-ionization cross-section (PICS) is highly dependent on all the variables under consideration. The optical spectra were blue-shifted with increasing electric field and pressure and red-shifted with increasing temperature and impurity displacement far from the center of the structure. Furthermore, it was found that changes in gallium content and impurity position can increase the PICS amplitude. A comparison of the obtained results with the existing literature as a limiting case of the reported problem is also provided, and excellent agreement is found.

The greenhouse effect is involving global heating and climate change within the world. Carbon dioxide (CO2) is one of the major gas at the origin of this effect, but also the byproduct of human activity. Therefore, monitoring the indoor/outdoor CO2 emission by gas sensors is one of the priorities for environmental preservation. In this paper, the sensing performance of CO2 towards two different O-rich films have been studied; graphene oxide (GO) and vanadium dioxide (VO2). The preparation of GO film has been carried out by spray pyrolysis on fluorine tin oxide (FTO) prepared by the modified Hummers method. While the VO2 film has been sol-gel spin-coated on a glass substrate. Both films have been characterized using XRD, SEM and electrical properties. The CO2 gas sensing mechanism and the role of oxygen vacancies in VO2 are addressing. The oxygen functional groups in GO play a main role in the CO2 gas the sensitivity level and response time. Their gas sensing performances have been investigated based on measuring the response vs recovery time, dynamic response curve analysis and sensitivity. In order to better understand the sensing mechanism, characterization has been done with different gas concentrations. Both GO and VO2 based CO2-sensors are acted as an n-type sensor. Sensing behavior of GO at RT has explained to be mainly mediated by the oxygen functional groups and a wide range of active sites. In the other hand, VO2 contains oxygen vacancies and more defect sites which play a main role in the RT sensing activity and low recovery time.

The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/A-exciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s)MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 × 108 Jones detectivity, and ~ 1.0 × 1010 quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at ~ 40 °C.

Effect of in-/ex-situ annealing on the structure, optical, photoluminescence, electrical characterization and gas sensing dynamics on CdS thin films are presented. Raman characterizations showed an increase in the peak intensity with increasing the annealing temperature under ex-situ, while a lower peak intensity observed through the in-situ annealing condition. No shift was observed in the Photoluminescence peaks through the yellow band peaks of in-situ annealed samples, however, a slightly blue shift was observed through the ex-situ annealed samples. High conductivity was observed for all samples, while in the case of in-situ RT, in-situ 100 degrees C, ex-situ 200 degrees C and ex-situ 300 degrees C, a CO2 and O-2 gas sensing activity have been tested. The ex-situ 300 degrees C sample shows a higher response towards CO2 compared with the ex-situ 200 degrees C film. While, both in-situ RT and 100 degrees C sensors show the same response towards CO2 with a high gas response. However, the in-situ 100 degrees C sensor has the highest response compared to in-situ RT film with a high response of 25% at 50 sccm towards O-2.

In this paper, a novel design of a one-dimensional defected phononic crystal (1D-DPC) sensor as a demultiplexer for sensing and distinguishing different harmful liquids is presented. The liquids of interest are acetone, ethanol, methanol, chloroform, phenol, 1-propanol, and mercury. Firstly, the liquids have been added in a single cavity inside the 1D-DPC design. Different resonance peaks related to each liquid appeared in the center of the phononic bandgap, each resonance frequency changes as the liquid type alters. Secondly, we examined the ability of the 1D-DPC liquid sensor to detect different concentrations of ethanol. Thirdly, the acetone, ethanol, methanol, chloroform, and mercury liquids at the same time via the 1D-DPC demultiplexer design. The performance parameters such as sensitivity, quality factor, and figure-of-merit on the 1D-DPC demultiplexer were calculated as well. The numerical investigations of the PC are studied based on the transfer matrix method. In the case of the 1D-DPC demultiplexer, liquid gives the highest sensitivity and FOM of 2.07 MHz/(kg/m3) and 2780 m3/Kg, respectively for ethanol. Meanwhile, the 1D-DPC liquid sensitive sensor the highest sensitivity and FOM were obtained for methanol of 0.245 MHz/(kg/m3) and 252 m3/Kg, respectively. The proposed 1D-DPC demultiplexer liquid sensor showed higher sensitivity compared with previous 1D-DPC liquid sensors. Moreover, we studied the damping rate effect on the resonant peaks of the 1D-DPC demultiplexer liquid sensor. Finally, our obtained results succeeded for the first time to couple both the 1D-DPC liquid sensor and the 1D-DPC demultiplexer in the same design with high performance. The proposed 1D demultiplexer idea can open the door to an entirely new type of liquid sensing modality in the simple 1D PC designs for many industrial and technological applications.