Papers by Keyword: Annealing

Abstract: In this work, a comparison of standard bulk 4H-SiC epi wafers and Soitec's SmartSiC™ wafers as well as the influence of RTA processing was conducted. For this, MOS capacitors were processed using thermal gate oxide paired with a polycrystalline gate electrode. Subsequent High temperature steps were avoided until an RTA process was performed on some of these wafers. To investigate the oxide quality on all wafer and process splits, CV-, time-zero dielectric breakdown and constant-current stress time-dependent dielectric breakdown measurements were carried out. For the examination of bulk wafers and SmartSiC™, no relevant differences in terms of yield, oxide quality, interface state density and reliability were found. In contrast, RTA processes seem to create a shift in flat band voltage and also lead to a reduction in oxide lifetime. The V_FB shift could partially, but not completely, be explained by addition activation of dopants in the polysilicon electrode. The influence on the oxide reliability, however, is still unclear.

Abstract: We have developed a novel, material-lossless silicon carbide (SiC) wafer manufacturing process that eliminates the need for conventional grinding and polishing. Utilizing a thermal sublimation growth and etching technique called Dynamic AGE-ing^® (DA), we simultaneously performed thermal sublimation etching and growth on both the Si-face and C-face of single-crystal SiC wafers. This study investigated the impact of surface undulations—arising during DA planarization of as-sliced wafers with varying slicing qualities—on the densities of basal plane dislocations (BPDs) and in-grown stacking faults (IGSFs) in the epitaxial layers. Our findings demonstrate that larger pre-growth surface undulations correlate with higher BPD and IGSF densities in the DA-grown layers. By optimizing the initial wafer quality and DA process conditions, we achieved epitaxial layers with low defect densities (BPD density of 0.09 cm⁻² and IGSF density of 1.37 cm⁻²) without any material loss. This advancement offers a significant breakthrough in SiC device manufacturing, potentially reducing material costs and enhancing device performance by suppressing killer defects in the epitaxial layers.

Abstract: In this work, Fe₃₅Cr₃₅Ti₁₀Ni₁₀Zr₁₀ (at%) is a new light-weight medium entropy alloy subjected to different annealing conditions (at 700 - 1000°C for different durations) to examine its thermal stability, microstructural evolution, and microhardness change. The developed alloy was characterized by Optical light microscopy, X-ray diffraction (XRD), and Vickers microhardness. It was observed that the alloy demonstrated high microhardness value of ~707and high thermal stability with minor changes in its microstructures after different annealing treatments. These excellent properties displayed by the alloy highlight its promise for high-temperature applications.

Abstract: The Ti-13Nb-1.5Mo-3Ta alloy is a recently developed biocompatible metastable β-Ti alloy designed for biomedical application. In this present work, the influence of cold rolling and subsequent annealing heat treatment on grain refinement of Ti-13Nb-1.5Mo-3Ta alloy was investigated. The alloy was cold rolled (CR) to 60% and 90% thickness reductions at room temperature followed by recrystallization annealing at different temperature (800°C-900°C) and time (1.5mins-10mins) before ice-water quenching. X-ray diffraction (XRD) and optical microscopy (OM) were used to characterize the alloy, and microhardness tests were carried out using the Vickers microhardness tester. The results revealed that the annealed alloys exhibited a fully β-phase, while those subjected to cold rolling displayed introduction of stress induced martensite (SIM) α′′-phase along with β-phase. The microhardness of the 60% and 90%CR samples increased significantly to 253 and 283 Vickers hardness (HV), respectively, from an initial value of 198 HV. Annealed samples exhibited a recrystallized microstructure containing fine equiaxed grains with average size of 10-50μm for 60%CR and 8-34μm for 90%CR. The grain refinement mechanisms are probably attributed to the reversal of the SIM α′′-phase back to the more stable β-phase and the recrystallization of the deformed β-phase.

Abstract: Magnetite nanoparticles are synthesized in an environmentally friendly way by utilizing natural ingredients found in citrus limon juice. The acid in citrus limon juice serves as a fuel for the sol-gel process, producing magnetite nanoparticles. Annealing treatment (400°C, 500°C, and 600°C) is used to change the structural and magnetic properties of the magnetite nanoparticles. All samples magnetite phase was verified by X-Ray Diffraction (XRD) examination. Increasing the annealing temperature causes an increase in crystallite size from 10.81 to 27.30 nm. Furthermore, the results of infrared spectroscopy revealed the presence of oxide bonds (M-O) in the range 558–567 cm^-1 and 408–437 cm^-1, which are Fe-O bonds. Magnetic properties also change as a result of the annealing treatment, which is characterized by increased saturation magnetization and changes in other magnetic parameters. Furthermore, green synthesis of magnetite nanoparticles is effective against gram-negative bacteria (E. Coli) with enhanced antibacterial performance.

Abstract: Microforming holds great importance due to the rising demand for miniaturized parts across diverse industries. It enables the efficient mass production of small-scale components using sheet metals. By exploring microforming processes, researchers can uncover the unique challenges and opportunities associated with manufacturing at the microscale. This research work investigates the impact of temperatures during the annealing on the mechanical properties, microstructural behaviour and formability of austenitic stainless steel 316 thin sheets. The thin sheet, with a thickness of 50µm was considered for the present analysis and were annealed at temperatures ranging from 400 to 1000°C for 30 minutes. Tensile tests were performed and mechanical properties were evaluated at various annealing temperatures. It was witnessed that as the temperature of annealing increases, the ultimate tensile strength reduces and ductility enhances. Erichsen cupping tests were conducted to assess the formability, measuring the dome height of the drawn cups. The results revealed that the as-received thin sheet exhibited poor formability. However, increasing the annealing temperature resulted in enhancing the formability, as evidenced by an increase in the dome height of the drawn cups. Furthermore, the annealing process led to an increase in grain size, which in turn inversely affected the material strength. Therefore, annealing not only enhanced formability but also influenced the microstructural characteristics of the stainless steel 316 foils. Fractography studies were done and the results show that higher annealing temperatures result in ductile fracture, which is favorable for practical applications. At lower temperatures, brittle fracture occurs with the presence of river markings. The present work helps in selecting appropriate annealing conditions for improved toughness and resistance to sudden failure in micro parts.

Abstract: Stainless steels are the material that has chromium as a main component. The chromium content reacts with oxygen in air, subsequently, forms thin chromium oxide film on the surface of stainless steels. Thus, when these steels are exposed to high temperature for a long period of time in many applications, chromium carbide could precipitate along the grain boundary and reduce the corrosion resistance. This project is conducted to study annealing time effect on stainless steels when exposed to high temperature at various exposure time periods. Three different kind of stainless steels, namely, AISI 304, AISI 304D and AISI 2205 were used in this study. Stainless steels were heated at 600°C for 0, 6, 24, 48 and 96 hours, then cool down in air. Consequently, the investigations were performed by using double-loop Electrochemical Potentiokinetic Reactivation (DL-EPR) and Cyclic Potentiodynamic Polarization (CPP) to study degree of sensitization and film properties. In addition, chromic acid and oxalic acid were used as reagent of acid etching to observe microstructures. Finally, Vickers hardness test were also conducted. Percentage degree of sensitization increased from 2.93% to 62.20% in AISI 304, increased from 5.26% to 55.54% in AISI 304D and from 12.19% to 69.35% in AISI 2205. The pitting potential decreased from 0.47 mV to 0.23 mV for AISI 304 but remained relatively constant for AISI 304D and AISI 2205. The results indicated that after the specimens were exposed to high temperature for a long period of time, all specimens had more chromium depleted areas, more carbide along the grain boundaries, worse film quality and small changes in hardness value.

Abstract: Electrospun piezoelectric nanofibrous membrane developed from Polyvinylidene fluoride (PVDF) embedded with thermoplastic polyurethane (TPU) composites found to have superior stretchability and piezoactivity. The piezoresponse behavior of different in-situ bended PVDF/TPU, up to 15wt.% of TPU, is examined using various blending ratios of PVDF and TPU. It has been shown that adding TPU with PVDF at certain specific concentration increased the nanofiber's piezo-efficiency.The generated nanomembranes are annealead at different temperatures up to 100°C. An extensive analysis of the effects of annealing is conducted on these nanomats, and it is thought to be a crucial post-treatment method for improving the piezoresponse of the manufactured nanomats. Nanofibers annealed at 100°C showed best effective response compared to all other samples and this revealed the effectiveness of annealing treatment in the enhancement of piezoactivity. The best effective composition of PVDF with 15 wt% TPU after an annealing treatment of 100°C generated a maximum voltage of 3.2 V under the effect of an applied force of 3 N, where unannealed sample of the same PVDF-TPU composition generated only a voltage of 2.2 V. This annealed piezo nanogenerator (PNG), can be considered an optimum option for electromechanical energy harvesting applications that require flexibility and self-power.

Abstract: This study substantiates the epigraphene formation theory on SiC, presenting it as freestanding graphene during thermal decomposition epitaxy. It was found that cool down process is responsible for the formation of the graphene buffer layer. Additionally the capping capabilities of the buffer layer have been evaluated using Raman spectroscopy and AFM measurements.

Abstract: The effect of high-temperature electron and proton irradiation on SiC-based device characteristics is being investigated. Industrial integrated 4H-SiC Schottky diodes, each with an n-type base and a blocking voltage of either 600 V, 1200 V, or 1700 V, manufactured by Wolfspeed, are being studied. 0.9 MeV electron and 15 MeV proton irradiation were applied. It has been found that the irradiation resistance of silicon carbide Schottky diodes at high temperatures significantly exceeds their resistance at room temperature. This effect is attributed to the annealing of compensating defects induced by high-temperature irradiation. The parameters of radiation-induced defects are determined using the method of deep level transient spectroscopy (DLTS). Under high-temperature ("hot") irradiation, the spectrum of radiation-induced defects introduced into SiC appears to differ significantly from the spectrum of defects introduced at room temperature. It is suggested that approximately half of the compensation is due to radiation-induced defects formed in the bottom part of the bandgap.