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Temperature dependence simulation and characterization for InP/InGaAs avalanche photodiodes
摘要： Based on the newly proposed temperature dependent dead space model, the breakdown voltage and bandwidth of InP/InGaAs avalanche photodiode (APD) have been investigated in the temperature range from -50°C to 100°C. It was demonstrated that our proposed model is consistent with the experimental results. Our work may provide a guidance to the design of APDs with controllably low temperature coefficient.
关键词： separate absorption, grading, charge, and multiplication avalanche photodiode (SAGCM APD),optical communication,temperature coefficient,dead space effect
更新于2025-09-23 15:23:52
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InSight Auxiliary Payload Sensor Suite (APSS)
摘要： NASA’s InSight mission to Mars will measure seismic signals to determine the planet’s interior structure. These highly sensitive seismometers are susceptible to corruption of their measurements by environmental changes. Magnetic fields, atmosphere pressure changes, and local winds can all induce apparent changes in the seismic records that are not due to propagating ground motions. Thus, InSight carries a set of sensors called the Auxiliary Payload Sensor Suite (APSS) which includes a magnetometer, an atmospheric pressure sensor, and a pair of wind and air temperature sensors. In the case of the magnetometer, knowledge of the amplitude of the fluctuating magnetic field at the InSight lander will allow the separation of seismic signals from potentially interfering magnetic signals of either natural or spacecraft origin. To acquire such data, a triaxial fluxgate magnetometer was installed on the deck of the lander to obtain magnetic records at the same cadence as the seismometer. Similarly, a highly sensitive pressure sensor is carried by InSight to enable the removal of local ground-surface tilts due to advecting pressure perturbations. Finally, the local winds (speed and direction) and air temperature are estimated using a hot-film wind sensor with heritage from REMS on the Curiosity rover. When winds are too high, seismic signals can be ignored or discounted. Herein we describe the APSS sensor suite, the test programs for its components, and the possible additional science investigations it enables.
关键词： Wind,Magnetometer,Spacecraft,Pressure,Temperature,Instruments
更新于2025-09-23 15:23:52
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Consideration of the Impact of the Environmental Conditions when Designing Heat-Receiving Systems of the Solar Cylindrical Parabolic Modules
摘要： The aerohydrodynamic and heat exchange characteristics in the cylindrical heat receiver of a solar cylindrical parabolic concentrating module are investigated. The mathematical model is based on the Navier-Stokes equation system for a laminar flow in a channel. The model is implemented using the control volume method. The created computer algorithm allows carrying out parametric studies and revealing the most rational geometric, dynamic, and power parameters of the process. The proposed model describes the general physical outlines of the heat exchange in a cylindrical heat receiver which allows estimating the influence of the environment—wind velocity, ambient temperature, etc.—on it.
关键词： cylindrical heat receiver,rational geometric, dynamic, and power parameters,solar cylindrical parabolic module,wind velocity,Navier-Stokes equation system,ambient temperature,control volume method
更新于2025-09-23 15:23:52
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The current-voltage characteristics of the ferroelectric p-YMnO3 thin film/bulk p-Si heterojunction over a broad measurement temperature range
摘要： The reverse and forward bias I-V characteristics of the Al/p-YMO/p-Si/Al heterojunction were measured at room temperature (RT) and over temperature range, from 50 to 320 K, and the I-V curves showed Schottky diode-like characteristics. The ideality factor and barrier height values were calculated as 0.81 and 2.62 from the forward bias I-V curve at room temperature (300 K), respectively. The YMO powder was prepared via solid state reaction technique. YMO thin films were grown on front surface of p-Si substrate by radio frequency (rf) magnetron sputtering using a polycrystalline YMO single target. The YMO thin film thickness on Si substrate was measured as ~70 nm via Dektak XT surface profilometer. The XRD, SEM, UV-Vis and XPS measurements of the YMO thin film were also performed. The bandgap energy of YMnO3 thin films was determined as 2.10 eV by UV-vis. The temperature-dependent reverse and forward bias I-V curves were evaluated in terms of thermionic emission (TE), Schottky emission, Fowler-Nordheim (F-N) tunneling and space charge-limited current (SCLC) current theories. Furthermore, it has been seen that the forward bias conduction in the junction at each temperature obeys F-N tunneling because of the linearity in the ln (I/V2) versus V-1 curves.
关键词： Polycrystalline,Heterojunction,Ferroelectric,Al/p-YMO/p-Si/Al,Schottky barrier,YMnO3,Temperature dependent current characteristics
更新于2025-09-23 15:23:52
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Temperature fiber sensing of Li-ion batteries under different environmental and operating conditions
摘要： In this work, a network of fiber sensors has been developed for real time, in situ, and in operando multipoint monitoring the surface temperature distribution on a smartphone Li-ion battery (LiB). Different temperature and relative humidity conditions are considered, in order to mimic the LiB response in the dry, temperate, and cold climates. In total, the temperature variations that occur in five different locations of the LiB are monitored, during constant current charge and different discharge rates, under normal and abusive operating conditions, performing a thermal spatial mapping of the battery surface. In general, the sensors detect temperature variations according to the voltage signal change and faster variations of voltage usually translate in higher temperature rise at the LiB surface. For instance, under abusive discharge, where the voltage drop is fast, the temperature increases at least twice when compared to the normal operating conditions. Absolute temperature values as high as (65.0 ± 0.1) °C are detected by the optical sensor located near the electrodes, under the higher discharge rate (5.77 C) and dry climate. A thermal gradient is identified from the top to the bottom on the LiB surface during the experimental tests. A lower battery performance is observed when it operates under the cold climate, with maximum temperature variations of (30.0 ± 0.1) °C for the higher discharge rate. These results can be helpful to design of next generation of LiBs, improving a faster cooling in critical areas, in order to reduce accumulated heat and preventing consequences such as thermal runaway and failure.
关键词： Fiber Bragg grating sensors,Temperature monitoring,Abnormal operating conditions,Environment,Safety,Li-ion batteries
更新于2025-09-23 15:23:52
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A simple, low cost ink system for Drop-On-Demand printing high performance metal oxide dielectric film at low temperature
摘要： We have successfully developed an ink system containing cheap raw materials through a simple process and have printed ZrOx dielectric film at a relatively low annealing temperature of 250 °C. The ZrOx dielectric film afforded a leakage current density of 5.4×10-6 A/cm2 at 1 MV/cm and a dielectric constant of 10, which shows promising future for flexible electronics. The ink system shows a temperature-induced gelation behavior and gel network is formed when temperature rises. A high concentration of oxide precursors is obtained near the network area through the absorption function of polymer groups, and thus oxide structure can be formed at a relatively low temperature due to the shorter diffusion path of precursor polymerization. The microstructure of printed ZrOx film was investigated by High Resolution Transmission Electron Microscope (HRTEM), Fourier-transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the effect of annealing temperature on film structure was studied.
关键词： dielectric film,low temperature,Low cost,ink system,Drop-On-Demand printing
更新于2025-09-23 15:23:52
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Chemical vapor deposition of graphene on refractory metals: The attempt of growth at much higher temperature
摘要： Large area graphene is usually grown by chemical vapor deposition on Cu or Ni catalysts at ～1000 °C. For most materials, high temperature leads to high quality. However, graphene growth at even higher temperatures is rarely reported. Therefore, here we systematically investigate the graphene deposition on refractory metals i.e. metals with extremely high melting points. The growth parameters and material characterizations are given in detail. On Ta which readily forms carbides during the carbon deposition, the growth mode is monolayer due to the chemical absorption of excess carbon in the bulk metal. On Re, there is no carbide formed (except in extreme conditions), which greatly simpli?es the scenario. Because of the relatively high carbon solubility in Re, the growth temperature has to be limited in order not to drift into the dominantly multilayer graphene regime caused by the carbon segregation. Graphene with reasonable quality has been achieved, although not as good as expected. For example, on Ta, the residual bonds between the graphene and substrate deteriorate the graphene crystalline quality. Despite the di?culties in refractory metal etching, the transfer technique of the graphene is also explored. This research contributes to the fundamental understanding of the graphene growth theory and technology on refractory metals.
关键词： Refractory metal,Graphene,Chemical vapor deposition,High temperature growth
更新于2025-09-23 15:23:52
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Definition of design guidelines, construction, and performance of an ultra-stable scanning tunneling microscope for spectroscopic imaging
摘要： Spectroscopic-imaging scanning tunneling microscopy is a powerful technique to study quantum materials, with the ability to provide information about the local electronic structure with subatomic resolution. However, as most spectroscopic measurements are conducted without feedback to the tip, it is extremely sensitive to vibrations coming from the environment. This requires the use of laboratories with low-vibration facilities combined with a very rigid microscope construction. In this article, we report on the design and fabrication of an ultra-stable scanning tunneling microscope (STM) for spectroscopic-imaging measurements that operates in ultra-high vacuum and at low temperatures (4 K). We start from existing designs with sapphire as the main material and improve the stiffness further by performing finite element analysis calculations for the main components of the microscope to guide design choices on the geometry of the parts. With this strategy, we construct a STM head with measured lowest resonant frequencies above f0 = 13 kHz for the coarse approach mechanism, a value three times higher than what has been previously reported and in good agreement with the calculations. This allows us to achieve an average vibration level of ～6 fm/√Hz, without a dedicated low-vibration lab. We demonstrate the microscope’s performance with topographic and spectroscopic measurements on the correlated metal Sr2RhO4, showing the quasiparticle interference pattern in real and reciprocal space with high signal-to-noise ratio.
关键词： ultra-high vacuum,low temperature,spectroscopic imaging,finite element analysis,ultra-stable,scanning tunneling microscopy
更新于2025-09-23 15:23:52
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Low-power-consumption Fiber-optic Anemometer based on Long-period Grating with SWCNT Coating
摘要： We report a low-power-consumption fiber-optic 'hot wire' anemometer (HWA) based on long-period grating (LPG) with single-wall carbon nanotubes (SWCNTs) coating. A uniform SWCNT film is deposited on a bare LPG acting as both light coupling and sensing element. By carefully selecting the order of the cladding mode and operating wavelength, the LPG shows a much higher temperature sensitivity than that of a regular fiber Bragg grating (FBG). Besides, SWCNT is a single-wall cylindrical nanostructure material with excellent absorption in the infrared range and high thermal conductivity. Due to these two features, the proposed sensor has extremely low power consumption and simple operation by utilizing a broadband light source (BBS) as both heating source and probing light source. A sensitivity of 102.5 pm/(m/s) at the wind speed of 1 m/s was obtained experimentally with 1.6-μm-thick SWCNT film.
关键词： Temperature.,Fiber-optic anemometer,long-period fiber grating,Carbon nanotube
更新于2025-09-23 15:23:52
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Novel research on reliability of silica-based PLC optical splitters
摘要： Environmental, mechanical and optical reliability are basic premises for application of PLC optical splitters. According to temperature and humidity cycling experiment, it demonstrated that insertion loss of PLC optical splitter varies with temperature. Compared to performance at room temperature, the maximum insertion loss change of device is 0.472 dB at 75 °C, and 0.486 dB at ?40 °C. A three-dimensional ?nite element model of PLC chip coupled with ?ber array was established to study the e?ects of temperature on insertion loss. The simulation results match experimental results, indicating that misalignment of PLC chip and ?ber array is the main reason for insertion loss change. It is signi?cant to consider the in?uences of global temperature rather than only paying attention to performance at static temperature when we evaluate the reliability of PLC optical splitters.
关键词： PLC optical splitter,Temperature and humidity,Finite element method,Optical waveguide,Reliability
更新于2025-09-23 15:23:52