Papers by Keyword: N₂O

Abstract: We present the improvement of SiO₂/4H-SiC interface quality and high field-effect (FE) mobility (µ_FE) in 4H-SiC MOSFETs. This is achieved by introducing a nitrous oxide (N₂O) plasma in-situ pre-treatment before gate stack formation using plasma enhanced chemical vapour deposition (PECVD) oxide followed by a post deposition anneal (PDA) in diluted N₂O for times ranging from 30 to 120 minutes thereby creating an ultra-thin thermally grown SiO₂ layer at the SiO₂/4H-SiC interface. MOS capacitors with SiO₂ deposited on in-situ pre-treated SiC surfaces had a lower density of interface traps (D_IT) for all PDA durations, compared with devices having untreated PECVD oxides or control devices with 30 nm thermally grown oxide. After PDA for 90 minutes, a minimum D_IT value of 1.2×10¹¹ cm^-2·eV^-1 was measured. A peak µ_FE value reaching 94 cm²/(V·s) was measured in n-channel planar MOSFETs fabricated with PECVD oxide on in-situ pre-treated devices, which significantly exceeds a maximum µ_FE of 6 cm²/(V·s) in control devices.

Abstract: A systematic capacitance-voltage (C-V) and time-dependent dielectric breakdown (TDDB) study on silicon carbide (SiC) metal-oxide-semiconductor capacitors (MOSCAPs) that use silicon dioxide (SiO₂) is shown in this paper. Oxides were formed using atomic layer deposition (ALD), low-pressure chemical vapour deposition (LPCVD) or direct thermal growth in nitrous oxide (N₂O) ambient, where both deposited oxides were post-deposition annealed in N₂O ambient, too. The electrical characterisation results reveal that the ALD-deposited and N₂O-annealed oxides show the best capacitance-voltage (C-V) characteristics, with flatband and hysteresis voltages (V_FB) averaging 1.44 V and 0.41 V, respectively. When measuring the leakage current levels at 175°C, the ALD-deposited MOSCAPs’ breakdown electric fields are averaging similar to their counterparts at 9.71 MV/cm. MOSCAPs which utilized ALD-deposited SiO₂ also showed 29% and 345% increased average injected charge-to 63% failure (Q_BD,63%) at 9 MV/cm and 9.6 MV/cm, respectively, when comparing these devices to their direct thermally grown SiO2 counterparts.

Abstract: N₂O is an important greenhouse gas. The emission of N₂O in wetlands is an important part of global N₂O flux. At present, the two leading factors mainly focus on the emission regularity of N₂O and the emission mechanism of it in the estuary wetland ecosystem at home and abroad. The main sources of wetland N₂O are the soil nitrification and denitrification. Research shows that, the N₂O emission is directly related to the availability of the soil nitrogen and the salinity reduces the production of N₂O by restraining the soil nitrification and denitrification process. Therefore, it is necessary to strengthen the study on the emission characteristics and influence factors of N₂O in the coastal wetland.

Abstract: Nitrous oxide (N₂O) is a kind of important greenhouse gas,which has the potential damage on the ozone layer and people’s physical health. A series of RPSA loading metals catalysts were prepared by impregnation. The catalysts were characterized by XRD, TG-MS, NH₃-TPD, SEM method. The catalytic performance for N₂O decomposition was evaluated. Cu-based catalyst is the best activity for N₂O decomposition, T₉₅ is 540°C.

Abstract: Because of high moisture content and compact structure, composting kitchen waste would discharge by-products such as leachate, ammonia (NH₃), and greenhouse gases, and these can cause secondary environmental pollution. In this study, continuous measurements of gas emissions were carried out and detailed gas emission patterns were obtained using forced aeration system at aerations of 2·10^-4 (T1), 4·10^-4 (A2) and 6·10^-4 ( (A3) m³·kgDM^-1·min^-1. During the experiment, temperature and oxygen content were determined, and continuous measurements of NH₃ and gaseous emissions (CH₄, N₂O, and NH₃) were taken. The results indicated that the aeration had a significant effect on NH₃, CH₄ and N₂O emission (p<0.05). The highest concentration of NH₃, CH₄ and N₂O were all observed in the treatment of T2. The productions of NH₃ were reduced by 59.6% and 33.7%, and greenhouse gases (GHG) were reduced by 50.8% and 40.5% for T1 and T2 that compared to T3, respectively. Obviously, the aeration has great influence on NH₃ and GHG emissions. In this study, the aeration was 2·10^-4 m³·kgDM^-1·min^-1 in favor of NH₃ and GHG reduction.

Abstract: The SCR catalysts were produced with V₂O₅, WO₃, MoO₃ and anatase type TiO₂. The catalyst samples were ground and sieved for 0.3~0.6mm.The NO catalytic efficiency, selectivity against N₂O of the catalysts were investigated on a fixed bed reactor under simulated exhaust gas with a typical gas composition. The addition of W enhanced the catalytic efficiency of V(1)-W(x)-Mo (4.5)/TiO₂ catalysts at high temperature region, while lessened that at low temperature. Increasing the loading of W from 1.5% w/w to 4.5% w/w advanced the maximum catalytic efficiency from 88% to 99% and enlarged the temperature window of the catalyst. The presence of W promoted the N₂O generation. The V(1)-W(4.5)-Mo (4.5)/TiO₂ catalyst showed higher catalytic selectivity for NO compared to the catalysts loading W.

Abstract: This work reports on the morphological, structural and electrical effects of a nitrous oxide (N₂O) ambient post-oxidation annealing (POA) of the SiO₂/4H-SiC interface. In particular, a conventional electrical characterization of MOS capacitors showed that nitrous oxide POA reduces the presence of both fixed oxide charge and the density of interface states. A local atomically flat interface was observed by transmission electron microscopy with only a moderate step bunching observed at a macroscopic scale. A novel nanoscale characterization approach via scanning spreading resistance microscopy resolved local electrical changes induced at the SiC surface exposed to N₂O POA. This result subsequently revealed additional insight into the mechanism for the improved device performance subjected to N₂O POA treatment.

Abstract: This work reports on the morphological, structural and electrical effects of a nitrous oxide (N₂O) ambient post-oxidation annealing (POA) of the SiO₂/4H-SiC interface. In particular, a conventional electrical characterization of MOS capacitors showed that nitrous oxide POA reduces the presence of both fixed oxide charge and the density of interface states. A local atomically flat interface was observed by transmission electron microscopy with only a moderate step bunching observed at a macroscopic scale. A novel nanoscale characterization approach via scanning spreading resistance microscopy resolved local electrical changes induced at the SiC surface exposed to N₂O POA. This result subsequently revealed additional insight into the mechanism for the improved device performance subjected to N₂O POA treatment.

Abstract: The V(1)-W(4.5)-Mo(x)/TiO2 catalysts was prepared by the incipient dry impregnation method. The catalyst samples were ground and sieved for 0.3~0.6 mm. The NO catalytic efficiency, selectivity against N2O of the catalysts were investigated on a fixed bed reactor under simulated exhaust gas with a typical gas composition. The addition of Mo enhanced the catalytic efficiency of V(1)-W(4.5)-Mo(x)/TiO2 catalysts at low temperature region, while lessened that at high temperature, especially at the temperature above 400 °C. Increasing the loading of Mo from 1.5% w/w to 4.5% w/w advanced the maximum catalytic efficiency from 78% to 99% and enlarged the temperature window of the catalyst. The acceptable NO conversion (>60%) was attained at temperature as low as 240 °C for V(1)-W(4.5)-Mo(7.5)/TiO2 catalyst. The presence of Mo promoted the N2O generation. The V(1)-W(4.5)-Mo(0)/TiO2 catalyst showed higher catalytic selectivity for NO compared to the catalysts loading Mo.

Abstract: A series of Beta, ZSM-5 and MCM-22 zeolites modified with metal ions (such as Fe ³⁺ , Co ²⁺ , Ce ³⁺ , Ni ²⁺ and Cu ²⁺ ) for catalytic decomposition of N₂O were prepared by using wet ion exchange method. The effects of different metal ions, the contents of metal ions and silicon aluminum ratio on catalytic decomposition activities of N₂O were investigated, respectively. The results indicated that Beta with a SiO₂/Al₂O₃=30 and 1% Fe ³⁺ have better catalytic decomposition activities to N₂O, the completed catalytic decomposition temperature to 35% N₂O in the condition of 4000 h^-1 GVSH is 350 ⁰ C.