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Substrate temperature dependent variation in the properties of cadmium telluride thin films deposited on glass
摘要： The present study relates to the variation in properties of cadmium telluride (CdTe) thin films deposited via electron beam and thermal vacuum evaporation methods at two different substrate temperatures. The influence of substrate temperature on structural, morphological, optical and electrical properties of CdTe thin films is investigated. For structural characterization, grazing incidence X-ray diffraction technique is used which revealed that thin films deposited at 200 °C temperature are more crystalline in nature as compare to the room temperature. The parameters such as average crystallite size (D), lattice strain (ε), number of crystallites per unit area (N) and texture coefficient TC (hkl) were calculated for both types of synthesized CdTe thin films. Surface morphology of thin films was recorded using scanning electron microscopy and found to be homogeneous in nature. The optical studies carried out using UV–Visible Spectrophotometer and Photoluminescence shown a decrease in band gap values for both electron beam and thermally deposited thin films samples at 200 °C substrate temperature. Electrical measurements recorded using two probes method showed the maximum value of current for CdTe thin films deposited by electron beam evaporation method at 200 °C substrate temperature.
关键词： Thermal vacuum evaporation,Optical properties,Thin films,Electron beam evaporation,Electrical properties,Structural properties,Substrate temperature,Cadmium telluride
更新于2025-09-09 09:28:46
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[IEEE 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Portland, OR, USA (2018.11.13-2018.11.14)] 2018 IEEE Avionics and Vehicle Fiber-Optics and Photonics Conference (AVFOP) - Micro-Structured Fiber as Temperature Sensor in a Loop Architecture
摘要： A temperature sensor built by a micro-structured fiber (MSF) into a Sagnac interferometer scheme is reported. The optical waveguide is provided by a two-hole fiber (THF) which are located asymmetrically from the core. A linear response to thermal effects is observed and the sensitivity 2.22 nm/°C was reached using a 2m-long of THF. The main advantage of the system proposed is a linear response, the use of a MSF with a simpler filled transverse geometry, non-use a special mechanism for the holes and a simple experimental array.
关键词： fiber optic,temperature sensor,micro-structured fiber,fiber sensors
更新于2025-09-09 09:28:46
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Rare Earth and Transition Metal Doping of Semiconductor Materials || Gadolinium-doped gallium-nitride
摘要： The race toward a dilute magnetic semiconductor (DMS) that exhibits room-temperature (RT) ferromagnetism has been in progress for about 15 years, sparked by the theoretical prediction that the two wide band-gap semiconductors GaN and ZnO would show a Curie temperature (TC) above 300 K if doped with 5% of Mn and a large hole concentration of 1 (cid:1) 1020/cm3 (Dietl et al., 2000). Despite apparent experimental evidence that RT magnetic order was already reported by many groups shortly after the theoretical prediction, the subject remained unusually controversial in the following years. Dietl (2010) summarizes that after 10 years of research the existence of ferromagnetism is well established for GaAs:Mn and related systems but it remains the major goal in the ?eld to achieve TCs at or above 300 K. Around the same time a review of a large group of theorists summarize: “The results of ab initio calculations seem to suggest that it is rather unlikely to obtain TC values as high as room temperature or above in this range” (Sato et al., 2010). Nonetheless persistent experimental claims of TCs above 300 K for a range of DMS materials can be found up to today. Thus it is worth trying to get a broader view on a given materials systems and compare a range of samples from different sources to elucidate whether these reports are characteristic of the DMS material itself (system-speci?c) or if only peculiarities of a given specimen are reported (sample-speci?c). Only in the former case can we consider those ?ndings to be useful for future potential applications in spintronic devices that have to be operational at ambient conditions.
关键词： ferromagnetism,room-temperature,GaN,Gd doping,dilute magnetic semiconductor
更新于2025-09-09 09:28:46
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An Empirical Study of In-Fiber Mach-Zehnder Interferometer’s Nonlinear Temperature Response
摘要： In this paper, we explore an empirical model capable to describe the nonlinear temperature response of in-fiber Mach–Zehnder interferometers (MZI). This model describes the nonlinear and linear response ranges with the same accuracy. It shows how the refractive index of the silica and the surroundings, including their thermo-optic coefficients, contribute to the temperature sensitivity (TS). It is also capable of predicting maxima and minima values for the TS, as well the conditions for the linear response to the temperature. Five different surroundings have been tested: air, water, ethanol, turpentine, and kerosene, in a temperature ranging from 20°C to 45°C. The resulting experimental TS values have ranged from 50 pm/°C to 1000 pm/°C. At 20°C, the calculated theoretical minimum and maximum TS were 45 pm/°C and 5377 pm/°C. We also show that this model can be applied to calculate temperature from wavelength measurements with arbitrary precision, as well as it can be used to identify substances through wavelength and temperature measurements.
关键词： Mach-Zehnder interferometer,cascaded long period grating,tunable temperature sensitivity,nonlinear response,Optical fiber sensor
更新于2025-09-09 09:28:46
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Characterisation and photocatalytic assessment of TiO2 nano-polymorphs: Influence of crystallite size and influence of thermal treatment on paint coatings and dye fading kinetics
摘要： A study on the thermal effects on TiO2 rutile and anatase nano-powders was undertaken and displayed some unusual photoactivity and crystal structure properties. Rutile nano-particles with different crystallite sizes were characterised and the possible effect on activity were investigated. One of the rutile samples appeared to have trace amounts of anatase and was annealed at high temperatures at 1172 K and 1272 K to highlight the thermodynamic stability phenomenon of titania. Parallel to this study, anatase nano-particles were investigated before and after being annealed up to 1022 K. For all the samples used in this work, characterisation was undertaken using micro-Raman microscopy/XRD and Scanning Electron Microscopy (SEM) while photoactivity assessment was made by measuring and monitoring the photodegradation of a mixture of dye methyl-orange (MeO) and nano-powders under UV-light for 3h30 minutes in suspension. The study revealed that rutile nano-powder samples were thermodynamically stable even at very high temperatures and poorly active but with an unusual photoactive feature. Concerning the anatase samples; SEM investigation revealed a questioning size growth as the samples showed a different particle size depending on the temperature of thermal treatment. It revealed that annealing at 672 K seemed to be a key temperature as the particles change from a polyhedral structure to a two-dimensional structure showing a platelet like shape. The photocatalytic studies of the anatase nano-particles showed a very high activity especially before annealing. This highlighted the fact that the anatase phase can subsist at high temperatures such as 1022 K and exhibit a persistence in photoactivity even though it has decreased significantly after 672 K. SEM analysis was in accordance with the photoactivity investigation. Nevertheless, the most interesting feature of the results emanates from the reaction order study and rate constant analysis taken from the kinetic shape of the graph of the degradation of MeO as a function of the irradiation time for the different particle sized rutile nanoparticles. Here a zero-order reaction was determined and as a consequence raised questions about the theory of the mechanism of the activities of titania in terms of surface chemistry, surface area dependence and photoactivity. For example, for the nano-rutiles the sample with a 25 nm crystallite size was the most active and the sample with the smallest crystallite size (15nm) was the least active and yet was found to contain trace levels of nano-anatase. This effect was also substantiated by UV absorption and weathering studies on doped isocyanate-acrylic paint films. UV analysis clearly shows that the absorptivity of the nanoparticles plays a role and correlates with the photoactivity. The 15nm particles have decreased absorptivity in the near UV and hence decreased activity.
关键词： nano-particles,titanium dioxide,crystal size,temperature treatment,anatase,isocyanate-acrylic paint,methyl orange,rutile,photocatalysis
更新于2025-09-09 09:28:46
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A comparative study of spectral and temperature sensing properties of Er3+ mono-doped LnNbO4 (Ln= Lu, Y, Gd) phosphors under 980 and 1500 nm excitations
摘要： LnNbO4: Er3+ (Ln= Lu, Y, Gd) phosphors were prepared through a conventional solid-state reaction method. The phase purity of the samples was characterized by X-ray diffraction (XRD). A comparative study of spectral and temperature sensing properties of LnNbO4: Er3+ (Ln= Lu, Y, Gd) phosphors was presented. The excitation spectra of the samples show a strong band in the region of 200-350 nm coming from the NbO4 4-, thus indicating efficient energy transfer from the host to Er3+. From the dependence of upconversion (UC) luminescence spectra on laser diode working current, it was confirmed that 2- and 3-photon processes were respectively responsible for both the green and the red UC emissions under 980 and 1550 nm excitations. The temperature sensing properties for LnNbO4: Er3+ were compared under individual excitation of 980 and 1550 nm. It was found that the temperature sensing was independent from the excitation wavelength, but LuNbO4: Er3+ phosphors yielded the highest luminescence intensity and maximum temperature sensitivity.
关键词： LnNbO4: Er3+ phosphors,Temperature sensing,Optical properties
更新于2025-09-09 09:28:46
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[IEEE 2018 34th International Conference on Lightning Protection (ICLP) - Rzeszow (2018.9.2-2018.9.7)] 2018 34th International Conference on Lightning Protection (ICLP) - Finite Element Simulation of a ZnO Varistor Stressed by a 4/10μs Current Impulse
摘要： When ZnO varistors are stressed by 4/10μs current impulses, mechanical cracking occasionally occurs. Based on finite element method, an electro-thermal-mechanical simulation of a ZnO varistor exposed to a 4/10μs current impulse is shown in the present paper focusing on temperature and thermal-induced mechanical stress distribution. The goal is to obtain a better understanding of the failure phenomenon under high current impulse with short duration. Conclusions of varistor design and manufacture are drawn after simulation analysis.
关键词： temperature,high current impulse,ZnO varistor,stress
更新于2025-09-09 09:28:46
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[IEEE 2018 13th International Congress Molded Interconnect Devices (MID) - Würzburg, Germany (2018.9.25-2018.9.26)] 2018 13th International Congress Molded Interconnect Devices (MID) - Low-Temperature Sintering of Nanometal Inks on Polymer Substrates
摘要： Digital non-contact-printing technologies such as inkjet or Aerosol Jet are becoming more and more interesting for the manufacturing of electronic components due to their benefits such as easy variation of printing layouts, short process chains without masks, large variety of usable substrates and inks - frequently based on nano metals - and a certain 3D capability. In this contribution options are discussed to sinter nano metal inks such as Ag, Au, and CuNi inks at low temperature, thus enabling the use of temperature sensitive polymer substrates like PC, PS, or PMMA. This includes the addition of chemical agents as well as light-based sintering methods such as photonic curing or laser sintering. Finally some application examples are presented.
关键词： Digital printing,laser sintering,photonic curing,low-temperature sintering,nano metal inks
更新于2025-09-09 09:28:46
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Simultaneous measurement of strain, temperature and refractive index based on a fiber Bragg grating and an in-line Mach–Zehnder interferometer
摘要： A simple sensor for simultaneous measurement of strain, temperature and refractive index (RI) is proposed and demonstrated. The sensor is based on a fiber Bragg grating (FBG) combined with an in-line Mach-Zehnder interferometer (MZI). MZI is formed by introducing a section of thinned core fiber (TCF) between two segments of multimode fiber (MMF). The two MMFs act as couplers that can excite high-order modes and recouple core mode and high-order modes into lead-out SMF, the function of this structure is to form inter-modes interference. The maximum interference fringe visibility exceed 20 dB. By monitoring the wavelength shifts of FBG and interference dips, simultaneous measurement of strain, temperature and RI can be achieved. The experimental results show that the maximum sensitivity of the sensor for strain, temperature and RI are -2.14 pm/με, 35.2 pm/°C and 32.93 nm/RIU, respectively. The proposed sensor has the advantages of easy fabrication, high fringe visibility and high sensitivities. Therefore, it has potential applications in multi-parameters simultaneous measurement.
关键词： Temperature,Refractive index,Mach-Zehnder interferometer,Strain,Fiber Bragg grating
更新于2025-09-09 09:28:46
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[ASME ASME 2018 37th International Conference on Ocean, Offshore and Arctic Engineering - Madrid, Spain (Sunday 17 June 2018)] Volume 5: Pipelines, Risers, and Subsea Systems - Development and Testing of a Friction-Based Post-Installable Fiber-Optic Monitoring System for Subsea Applications
摘要： This paper continues to document the design, development, and test of a friction-based (non-adhesive) post-installable fiber-optic strain sensing system for oil and gas applications – especially those that require deployment on existing subsea structures. (Ref: OMAE2017-61494 Development and Testing of a Friction-Based Post-Installable Sensor for Subsea Fiber-Optic Monitoring Systems [1]). The prototype fiber-optic monitoring system collects a wide range of real-time data, which can be used to determine structural loading, fatigue, temperature, pressure, and flow assurance on operational platforms. The primary challenge of a post-installed instrumentation monitoring system is to ensure secure coupling between the sensors and the structure of interest for reliable measurements. Friction-based coupling devices have the potential to overcome installation challenges caused by marine growth and soil contamination on subsea structures, flowlines, or risers. This particular design solution is compatible with structures that are suspended in the water column and those that are resting on the seabed. In addition, the system can be installed by commercial divers in shallow depths or by remotely operated vehicles in deep-water applications. Operational limitations of the initial design concept were identified in the previous series of tests (2016-2017), and several innovative enhancements have been implemented which resulted in significant improvements in sensor system coupling and strain measurement correlation with traditional strain measuring devices. This paper provides a summary of the notable prototype design changes, full-scale test article buildup, and detailed performance data recorded during tension and compression loading that simulated representative offshore conditions. The test results were positive and demonstrated the effectiveness of the design enhancements. Compromises made during mounting of the sensing elements resulted in better performance in tension than compression. These effects are well understood and are fully discussed, and do not influence the viability of the design changes. This study is part of a continuing collaboration between the Houston-based NASA-Johnson Space Center and Astro Technology, Inc. within a study called Clear Gulf. The primary objective of the Clear Gulf study is to develop advanced instrumentation technologies that will improve operational safety and reduce the risk of hydrocarbon spillage. NASA provided unique insights, expansive test facilities, and technical expertise to advance these technologies that would benefit the environment, the public, and commercial industries.
关键词： structural loading,subsea,fiber-optic,flow assurance,monitoring system,temperature,pressure,friction-based,fatigue,post-installable
更新于2025-09-09 09:28:46