共查询到6条相似文献,搜索用时 4 毫秒
1.
R. Nipoti A. Nath S.B. Qadri Y-L. Tian C. Albonetti A. Carnera Mulpuri V. Rao 《Journal of Electronic Materials》2012,41(3):457-465
Semi-insulating 4H-SiC ⟨0001⟩ wafers have been phosphorus ion implanted at 500°C to obtain phosphorus box depth profiles with
dopant concentration from 5 × 1019 cm−3 to 8 × 1020 cm−3. These samples have been annealed by microwave and conventional inductively heated systems in the temperature range 1700°C
to 2050°C. Resistivity, Hall electron density, and Hall mobility of the phosphorus-implanted and annealed 4H-SiC layers have
been measured in the temperature range from room temperature to 450°C. The high-resolution x-ray diffraction and rocking curve
of both virgin and processed 4H-SiC samples have been analyzed to obtain the sample crystal quality up to about 3 μm depth from the wafer surface. For both increasing implanted phosphorus concentration and increasing post-implantation annealing
temperature the implanted material resistivity decreases to an asymptotic value of about 1.5 × 10−3 Ω cm. Increasing the implanted phosphorus concentration and post-implantation annealing temperature beyond 4 × 1020 cm−3 and 2000°C, respectively, does not bring any apparent benefit with respect to the minimum obtainable resistivity. Sheet resistance
and sheet electron density increase with increasing measurement temperature. Electron density saturates at 1.5 × 1020 cm−3 for implanted phosphorus plateau values ≥4 × 1020 cm−3, irrespective of the post-implantation annealing method. Implantation produces an increase of the lattice parameter in the
bulk 4H-SiC underneath the phosphorus-implanted layer. Microwave and conventional annealing produce a further increase of
the lattice parameter in such a depth region and an equivalent recovered lattice in the phosphorus-implanted layers. 相似文献
2.
Charlotte Jonas Craig Capell Al Burk Qingchun Zhang Robert Callanan Anant Agarwal Bruce Geil Charles Scozzie 《Journal of Electronic Materials》2008,37(5):662-665
A common current gain of 70 has been achieved in 4H-SiC bipolar junction transistors (BJTs) at room temperature, which is
the highest among those reported. BJTs having an active area of 4 mm × 4 mm exhibit a specific on-resistance of 6.3 mΩ cm2 at 25°C, which increases to 17.4 mΩ cm2 at 250°C. BVCEO (the breakdown voltage from collector to emitter with open base) and BVCBO (the breakdown voltage from collector to base with open emitter) of 1200 V were observed at <5 μA leakage currents at all temperatures up to 250°C. Dynamic characteristics were measured using the IXYS RF/Directed Energy
IXDD415 gate driver evaluation board to drive the BJT. A collector current (I
C) rise time at turn-on of 32 ns was measured with a 1.6 A gate current provided to support the collector current of 63 A.
An I
C fall time at turn-off of 16 ns was achieved. 相似文献
3.
Sheng Lei Ziqi Zeng Hui Yan Mingsheng Qin Mengchuang Liu Yuanke Wu Han Zhang Shijie Cheng Jia Xie 《Advanced functional materials》2023,33(34):2301028
The operation of lithium-ion batteries (LIBs) at low temperatures (<−20 °C) is hindered by the low conductivity and high viscosity of conventional carbonate electrolytes. Methyl acetate (MA) has proven to be a competitive low-temperature electrolyte solvent with low viscosity and low freezing point, but its interfacial stability is poor and remains elusive until now. Here, it is revealed thaat the reductive stability of MA-based electrolytes is fundamentally governed by the anion-prevailed solvation structure. Based on this framework, fluorobenzene is employed in the electrolyte to promote the entry of anions into the solvation shell via dipole-dipole interactions and the generation of free MA, thus enhancing the lowest unoccupied molecular orbital energy of MA. The designed electrolyte enables LiCoO2 (LCO)/graphite cells to exhibit excellent cycling performance at −20 °C (90% retention after 1000 cycles at 1 C) and to remain 91% of their room-temperature capacity at a super-low temperature of −60 °C at 0.05 C. Thanks to the plentiful free MA, this electrolyte has a high conductivity (2.61 mS cm−1) at −60 °C and allows LCO/graphite cell to charge at −60 °C. This study offers the possibility of practical applications for those solvents with poor reductive stability and provides new approaches to designing advanced electrolytes for low-temperature applications. 相似文献
4.
Jinshu Tong Anyu Su Teng Ma Junjie Ba Luyao Wang Zeyu Zhang Jingyi Qiu Xibang Chen Yizhan Wang Yingjin Wei 《Advanced functional materials》2024,34(10):2310934
Severe capacity degradation at low temperatures (<−20°С) hampers wide applications of lithium-ion batteries (LIBs) in consumer electronics and electric vehicles. Existing works are dedicated to electrolyte modification because that electrolyte controls both Li+ transportation and interfacial reaction. However, the efforts on electrolytes are always hard to balance rate performance and low-temperature capacity due to their high viscosity. Herein, a binary coating layer for Li3V2(PO4)3 cathode material without changing electrolyte formulation is proposed, which significantly improves the high-rate capability and low-temperature performance of batteries. YPO4 nanoparticles are in situ formed in the amorphous surface carbon layer under the reaction between Li3V2(PO4)3 and Y(NO3)3 during post-thermal treatment. The C+YPO4 binary coating reduces the side reactions of Li3V2(PO4)3 at high voltage. In addition, the binary surface coating also improves the interfacial kinetics of the electrode at low temperatures. Benefiting from these advantages, the Li3V2(PO4)3 cathode material can cycle stably at ultra-high rates up to 50 C. In addition, the capacity retention at −20 and −40 °С are improved to 89.1% and 75.7%, respectively. This binary surface-coated Li3V2(PO4)3 cathode material shows promising application potential in low-temperature LIBs. 相似文献
5.
N. A. Hegab M. Fadel I. S. Yahia A. M. Salem A. S. Farid 《Journal of Electronic Materials》2013,42(12):3397-3407
The alternating-current (ac) conductivity and dielectric properties of Se85Te15?x Sb x (x = 0 at.%, 2 at.%, 4 at.%, and 6 at.%) films are reported in this work. Thin films were deposited by thermal evaporation under base pressure of 10?5 Torr. The films were well characterized by x-ray diffraction, differential scanning calorimetry, and energy-dispersive x-ray spectroscopy. The ac conductivity and dielectric properties have been investigated for the studied films in the temperature range from 297 K to 333 K and over the frequency range from 102 Hz to 105 Hz. The experimental results indicate that the ac conductivity $ \sigma_{\rm{ac}} (\omega ) $ and the dielectric constant depend on temperature, frequency, and Sb content. The frequency dependence of $ \sigma_{\rm{ac}} (\omega ) $ was found to be linear with a slope lying very close to unity and is independent of temperature. This behavior can be explained in terms of correlated barrier hopping between centers forming intimate valence-alternation pairs. The density of localized states N(E F) at the Fermi level is estimated. The activation energy $ \Updelta E(\omega ) $ was found to decrease with increasing frequency. The dielectric constant ε 1 and dielectric loss ε 2 were found to decrease with increasing frequency and increased with increasing temperature over the ranges studied. The maximum barrier height W m for the studied films was calculated from an analysis of the dielectric loss ε 2 according to the Guintini equation. The values agree with that proposed by the theory of hopping of charge carriers over a potential barrier as suggested by Elliott for chalcogenide glasses. The variation of the studied properties with Sb content was also investigated. 相似文献