No abstract

No abstract

The performance, energy storage capacity, safety, and lifetime of lithium-ion battery cells of different chemistries are very sensitive to operating and environmental temperatures. The cells generate heat by current passing through their internal resistances, and chemical reactions can generate additional, sometimes uncontrollable, heat if the temperature within the cells reaches the trigger temperature. Therefore, a high-performance battery cooling system that maintains cells as close to the ideal temperature as possible is needed to enable the highest possible discharge current rates while still providing a sufficient safety margin. This paper presents a novel design, preliminary development, and results for an inexpensive reusable, liquid-cooled, modular, hexagonal battery module that may be suitable for some mobile and stationary applications that have high charge and or discharge rate requirements. The battery temperature rise was measured experimentally for a six parallel 18650 cylindrical cell demonstrator module over complete discharge cycles at discharge rates of 1C, 2C and 3C. The measured temperature rises at the hottest point in the cells, at the anode terminal, were found to be 6, 17 and 22 °C, respectively. The thermal resistance of the system was estimated to be below 0.2 K/W at a coolant flow rate of 0.001 Kg/s. The proposed liquid cooled module appeared to be an effective solution for maintaining cylindrical Li-ion cells close to their optimum working temperature.

No abstract

In a novel approach, high temperatures (1200-1400°C) were used to oxidize cubic silicon carbide (3C-SiC) grown on silicon substrate. High-temperature oxidation does not significantly affect 3C-SiC doping concentration, 3C-SiC structural composition, or the final morphology of the SiO 2 layer, which remains unaffected even at 1400°C (the melting point of silicon is 1414°C). Metal-oxide-semiconductor capacitors (MOS-C) and lateral channel metaloxide-semiconductor field-effect-transistors (MOSFET) were fabricated by use of the high-temperature oxidation process to study 3C-SiC/SiO 2 interfaces. Unlike 4H-SiC MOSFET, there is no extra benefit of increasing the oxidation temperature from 1200°C to 1400°C. All the MOSFET resulted in a maximum field-effect mobility of approximately 70 cm 2 /V s.

No abstract

This paper presents a detailed physical and electrical analysis of 4H-SiC ohmic contacts to p-type material, the main aim being to examine their ruggedness under high temperature conditions. XRD, FIB-TEM and SEM are techniques that have been utilized to examine the microstructure and interface properties respectively. A detailed physical study revealed the presence of a crystalline hexagonal Ti layer orientated in the same direction as the 4H-SiC epitaxial layer. This factor seems to be important in terms of electrical performance, having the lowest measured specific contact resistivity of 1x10-6Ωcm2. We attribute this to the optimized formation of Ti3SiC2at the metal/SiC interface. An initial high temperature study shows thermionic emission occurring across the metal/semiconductor junction.

Despite the recent advances in 3C-SiC technology, there is a lack of statistical analysis on the reliability of SiO2 layers on 3C-SiC, which is crucial in power MOS device developments. This paper presents a comprehensive study of the medium and long-term time-dependent dielectric breakdown (TDDB) of 65 nm thick SiO2 layers thermally grown on a state-of-the-art 3C-SiC/Si wafer. Fowler-Nordheim (F-N) tunnelling is observed above 7 MV/cm and an effective barrier height of 3.7 eV is obtained, which is highest known for native SiO2 layers grown on the semiconductor substrate. The observed dependence of the oxide reliability on the gate active area suggests the oxide quality has not reached the intrinsic level. Three failure mechanisms were identified, confirmed by both medium and long-term results. Whereas two of them are likely due to extrinsic defects from material quality and fabrication steps, the one dominating the high field (>8.5 MV/cm) should be attributed to the electron impact ionization within SiO2. At room temperature, the field acceleration factor is found to be ≈0.906 dec/ (MV/cm) for high fields, and the projected lifetime exceeds 10 years at 4.5 MV/cm.