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Thermoresistance of <i>p</i> -Type 4H-SiC Integrated MEMS Devices for High-Temperature Sensing
摘要： There is an increasing demand for the development and integration of multifunctional sensing modules into power electronic devices that can operate in high temperature environments. Here, the authors demonstrate the tunable thermoresistance of p-type 4H–SiC for a wide temperature range from the room temperature to above 800 K with integrated flow sensing functionality into a single power electronic chip. The electrical resistance of p-type 4H–SiC is found to exponentially decrease with increasing temperature to a threshold temperature of 536 K. The temperature coefficient of resistance (TCR) shows a large and negative value from (cid:1)2100 to (cid:1)7600 ppm K corresponding to a thermal index of 625 K. From the threshold temperature of 536–846 K, the electrical resistance shows excellent linearity with a positive TCR value of 900 ppm K. The authors successfully demonstrate the integration of p–4H–SiC flow sensing functionality with a high sensitivity of 1.035 μA(m s)^(-0.5) mW^(-1). These insights in the electrical transport of p–4H–SiC aid to improve the performance of p–4H–SiC integrated temperature and flow sensing systems, as well as the design consideration and integration of thermal sensors into 4H–SiC power electronic systems operating at high temperatures of up to 846 K.
关键词： thermoresistance,MEMS sensors,silicon carbide,high temperatures
更新于2025-09-19 17:15:36
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Lithography and Etchinga??Free Microfabrication of Silicon Carbide on Insulator using Direct UV Laser Ablationa??
摘要： This work presents a lithography and etching-free micro fabrication of SiC on insulator-based MEMS devices, employing a direct laser ablation. SiC micro-scale structures can be formed in one-step patterning with a remarkably fast speed, enabling rapid prototyping of a multifunctional SiC platform of temperature sensors, strain sensors, and micro heaters.
关键词： silicon carbide,force sensor,micro-heater,temperature sensor,laser ablation
更新于2025-09-19 17:13:59
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Fabrication of silicon carbide nanoparticles using picosecond pulsed laser ablation in acetone with characterizations from TEM and XRD
摘要： We fabricated SiC nanoparticles (NPs) using a laser ablation method in acetone with a picosecond pulsed laser and characterized the resulting sizes, shapes, and crystal structures using transmission electron microscopy (TEM) and X-ray diffraction (XRD). We revealed two formation processes for the SiC NPs. The main process was the formation of spherical NPs with diameters primarily less than 10 nm. The crystal structure was 3C-SiC, which did not depend on a target polytype. Therefore, it is concluded that these NPs are grown from atomic molecules that disassociate from targets in the ablation process. As a result of a Rietbelt analysis of the XRD patterns, we clearly found that almost all NPs were single crystals. In addition, a stacking fault in the crystal was observed in the TEM image, which affects the XRD pattern. The other process was the formation of NPs with diameters from 30 to 80 nm with crystal structures that were the same as the targets. This indicates that these NPs were generated as fragments of the target. Our findings are useful for applications of SiC NPs to selectively control their size, shape, and crystal structure using laser ablation.
关键词： silicon carbide nanoparticles,3C-SiC,picosecond pulsed laser ablation,TEM,XRD
更新于2025-09-19 17:13:59
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Synthesis of silicon carbide nanocrystals and multilayer graphitic carbon by femtosecond laser irradiation of polydimethylsiloxane
摘要： Laser-based modification of polymer materials has been emerging as a versatile and efficient technique to simultaneously form and pattern electrically conductive materials. Recently, it has been revealed that native polydimethylsiloxane (PDMS) can be modified into electrically conductive structures using femtosecond laser irradiation; however, the details regarding the structures formed by this method have yet to be revealed. In this work, structures were fabricated by focusing and scanning femtosecond laser pulses onto the surface of PDMS. Raman Spectroscopy and Transmission Electron Microscopy (TEM) analyses revealed the formation of silicon carbide (SiC) nanocrystals, as well as multilayer graphitic carbon, in the modified regions of PDMS. The state of the formed material differed depending on the distance from the focal spot, suggesting that photo-thermal effects contributed to the degradation of PDMS into conductive material. Electrical conductivity measurements, in addition to Raman results, indicated that the amount of disorder in the formed graphitic carbon contributes to the electrical conductivity of the fabricated structures.
关键词： PDMS,femtosecond laser,graphitic carbon,electrical conductivity,silicon carbide
更新于2025-09-19 17:13:59
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Atomically thin half-van der Waals metals enabled by confinement heteroepitaxy
摘要： Atomically thin two-dimensional (2D) metals may be key ingredients in next-generation quantum and optoelectronic devices. However, 2D metals must be stabilized against environmental degradation and integrated into heterostructure devices at the wafer scale. The high-energy interface between silicon carbide and epitaxial graphene provides an intriguing framework for stabilizing a diverse range of 2D metals. Here we demonstrate large-area, environmentally stable, single-crystal 2D gallium, indium and tin that are stabilized at the interface of epitaxial graphene and silicon carbide. The 2D metals are covalently bonded to SiC below but present a non-bonded interface to the graphene overlayer; that is, they are ‘half van der Waals’ metals with strong internal gradients in bonding character. These non-centrosymmetric 2D metals offer compelling opportunities for superconducting devices, topological phenomena and advanced optoelectronic properties. For example, the reported 2D Ga is a superconductor that combines six strongly coupled Ga-derived electron pockets with a large nearly free-electron Fermi surface that closely approaches the Dirac points of the graphene overlayer.
关键词： 2D metals,superconductivity,epitaxial graphene,quantum devices,silicon carbide
更新于2025-09-19 17:13:59
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Surface Polariton‐Like s‐Polarized Waveguide Modes in Switchable Dielectric Thin Films on Polar Crystals
摘要： Surface phonon polaritons (SPhPs) and surface plasmon polaritons (SPPs), evanescent modes supported by media with negative permittivity, are a fundamental building block of nanophotonics. These modes are unmatched in terms of field enhancement and spatial confinement, and dynamical all-optical control can be achieved, e.g., by employing phase-change materials. However, the excitation of surface polaritons in planar structures is intrinsically limited to p-polarization. On the contrary, waveguide modes in high-permittivity films can couple to both p- and s-polarized light, and in thin films, their confinement can become comparable to surface polaritons. Here, it is demonstrated that the s-polarized waveguide mode in a thin Ge3Sb2Te6 (GST) film features a similar dispersion, confinement, and electric field enhancement as the SPhP mode of the silicon carbide (SiC) substrate, while even expanding the allowed frequency range. Moreover, it is experimentally shown that switching the GST film grants nonvolatile control over the SPhP and the waveguide mode dispersions. An analytical model is provided for the description of the GST/SiC waveguide mode and it is shown that the concept is applicable to the broad variety of polar crystals throughout the infrared spectral range. As such, complementarily to the polarization-limited surface polaritons, the s-polarized waveguide mode constitutes a promising additional building block for nanophotonic applications.
关键词： waveguide modes,infrared spectral range,phase-change materials,surface plasmon polaritons,silicon carbide,nanophotonics,Ge3Sb2Te6,surface phonon polaritons,s-polarized light
更新于2025-09-19 17:13:59
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Design of Multifunctional Titania-Based Photocatalysts by Controlled Redox Reactions
摘要： This work aims at the preparation of multifunctional titania-based photocatalysts with inherent capabilities for thermal co-activation and stabilisation of anatase polymorph, by designing the phase composition and microstructure of rutile-silicon carbide mixture. The processing involved a conventional solid state route, including partial pre-reduction of rutile by SiC in inert Ar atmosphere, followed by post-oxidation in air. The impacts of processing conditions on the phase composition and photocatalytic activity were evaluated using Taguchi planning. The XRD studies confirmed the presence of rutile/anatase mixtures in the post-oxidised samples. The results emphasise that pre-reduction and post-oxidation temperatures are critical in defining the phase composition, while post-oxidation time is relevant for the photocatalytic performance. Microstructural studies revealed the formation of core-shell particles, which can suppress the photocatalytic activity. The highest apparent reaction rate of the photodegradation of methylene blue was observed for the sample pre-reduced in Ar at 1300°C for 5 h and then calcined in air at 400°C for 25 h. Though its performance was ~1.6-times lower than that for the same amount of nanostructured industrial P25 photocatalyst, it was achieved in the material possessing 2–3 times lower surface area and containing ~50 mol% of SiO2 and SiC, thus demonstrating excellent prospects for further improvements.
关键词： silicon carbide,Taguchi plan,photocatalysis,redox reaction,anatase,TiO2
更新于2025-09-19 17:13:59
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Effect of Temperature on the Characteristics of 4H-SiC UV Photodetectors
摘要： The influence exerted by the carrier concentration in the range (1–50) × 1014 cm–3 in n-4H-SiC chemical-vapor deposited (CVD) epitaxial layers on the spectral characteristics of UV photodetectors with Cr Schottky barriers in the range of 200–400 nm is revealed and explained in terms of the photoconductivity theory. Schottky barriers with a Cr film thickness of 20 nm and diameter of 8 mm are formed by thermal evaporation in vacuum through masks. A noticeable effect of the carrier concentration in the CVD epitaxial layers on the spectral characteristics of photodetectors upon heating to 200°C is also observed and accounted for by a difference between the generation-recombination processes. The irradiation of photodetectors with 15-MeV protons at a fluence of 4 × 1012 cm–2 and a temperature of 200°C leads to an increase in the quantum efficiency as compared to samples irradiated in similar modes at 25°C. This is indicative of an increase in the radiation hardness and service life of 4H-SiC devices at elevated temperatures.
关键词： irradiation,quantum efficiency,protons,silicon carbide,fluence
更新于2025-09-19 17:13:59
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Increasing Laser-Doping Depth of Al in 4H-SiC by Using Expanded-Pulse Excimer Laser
摘要： Al doping into 4H-SiC performed by irradiating pulse-width-expanded excimer laser to an Al film deposited on the 4H-SiC surface is investigated. An optical pulse stretcher was constructed to produce the laser pulse whose peak intensity was reduced as half as that of the original pulse and pulse width was expanded from 55 ns to 100 ns. The irradiation of the expanded pulses is found to reduce the ablation of the materials from the surface and enable irradiation of multiple shots. As a result, Al doping depth is significantly increased. The multiple shots of the expanded pulses are also found to decrease the sensitivity to spatial non-uniformity of laser intensity and increase the uniformity of doped region.
关键词： excimer laser,p-type silicon carbide,aluminum doping,silicon carbide,laser doping,optical pulse stretcher
更新于2025-09-16 10:30:52
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Management of losses (thermalization-transmission) in the Si-QDs inside 3Ca??SiC to design an ultra-high-efficiency solar cell
摘要： Thermalization loss is one of the major losses in the single junction solar cells. Here, 3C–SiC as a wide bandgap semiconductor is used to manage this loss. To prevent the transmission of low energy photons, the intermediate bands inside the forbidden band gap is used. To do this, silicon quantum dots inside silicon carbide is suggested. At first, the detailed balance calculations are carried out to determine the efficiency limits of a cell with one and two mini-bands. Optical simulation using 3D FEM solution of the Schrodinger equation is done to obtain mini-bands, wave functions, and hence the optical absorption coefficient. Dimension parameters of a QD array like radius, inter-dot spacing, and array size are optimized to obtain a maximum efficiency. Inter-band and inter-sub-band absorption coefficient are calculated. That applied to determine the optimum characteristic of a QD–based intermediate band solar cell. The photocurrent increases as the inter-dot spaces decrease. Suitable radiuses and inter-dot spaces are found to obtain a high absorption coefficient and hence higher photocurrent. Finally, the effect of non-radiative recombination on the device performances is simulated. These results provide significant information to design a three-dimensional QDs based intermediate band solar cells.
关键词： Intermediate band,Super lattice,Silicon carbide,Multi-band,3D schrodinger,Si/SiC quantum dot,High efficiency
更新于2025-09-16 10:30:52