Novel models （2× 1） of Si（001）-SiO2 interface structure have been established. The method of the first-principle General Gradient Approximation （GGA） is employed to structurally optimize the established the...Novel models （2× 1） of Si（001）-SiO2 interface structure have been established. The method of the first-principle General Gradient Approximation （GGA） is employed to structurally optimize the established theoretical models under the K-point space of periodic boundary condition. The structures after optimization have been analyzed, and the results show that the interfaces present in disordered state and both Si-O-Si and Si=O structures exist. Meanwhile, the bonding of surface structure is analyzed via the graphics of electron localization function（ELF）.展开更多
We investigate the effects of NO annealing and forming gas （FG） annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements. With nitrogen passivation, the density of i...We investigate the effects of NO annealing and forming gas （FG） annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements. With nitrogen passivation, the density of interface states （DIT） is significantly reduced in the entire energy range, and the shift of flatband voltage, AVFB, is effectively suppressed to less than 0.4 V. However, very fast states are observed after NO annealing and the response frequencies are higher than 1 MHz at room temperature. After additional FG annealing, the DIT and AVFB are further reduced. The values of the DIT decrease to less than 1011 cm-2 eV- 1 for the energy range of Ec - ET 〉/0.4 eV. It is suggested that the fast states in shallow energy levels originated from the N atoms accumulating at the interface by NO annealing. Though FG annealing has a limited effect on these shallow traps, hydrogen can terminate the residual Si and C dangling bonds corresponding to traps at deep energy levels and improve the interface quality further. It is indicated that NO annealing in conjunction with FG annealing will be a better post-oxidation process method for high performance SiC MOSFETs.展开更多
Ta is often used as a buffer layer in magnetic multilayers. In this study, Ta/Ni81Fe19/Ta multilayers were deposited by magnetron sputtering on sing-crystal Si with a 300-nm-thick SiO2 film. The composition and chemic...Ta is often used as a buffer layer in magnetic multilayers. In this study, Ta/Ni81Fe19/Ta multilayers were deposited by magnetron sputtering on sing-crystal Si with a 300-nm-thick SiO2 film. The composition and chemical states at the interface region of SiO2/Ta were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there is an "intermixing layer" at the SiO2/Ta interface due to a thermody-namically favorable reaction: 15 SiO2+37 Ta = 6 Ta2O5 + 5 Ta5Si3. Therefore, the Ta buffer layer thickness used to induce NiFe (111) texture increases.展开更多
The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric c...The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance-voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 ℃ for 30 min, while a large num- ber of effective dielectric charges are generated. The components at the SiO2/SiC interface are analyzed by X-ray photoelectron spectroscopy （XPS） testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process.展开更多
Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique. The fibres were pre-coated a SiO2 layer prior to fabrication. DifFerent microstructures and interactions ...Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique. The fibres were pre-coated a SiO2 layer prior to fabrication. DifFerent microstructures and interactions in the fibre-matrix interface of these composites were observed by transmission electron microscopy （TEM）. The results showed that the interracial interaction strongly depended on the content of Al in the Mg-based matrices. The microstructure of the interface could then be controlled by adjusting the Al content of the Mgbased matrix. In addition, fibres extracted from different Mg-based matrix all had some degradation owing to the interracial reaction and the fibre-matrix interdiffusion.展开更多
基金Supported by the National Grand Fundamental Research 973 Program of China (No. 51310Z07-3) and the Research Program of Application of Sichuan Department of Science and Technology (No. 02GY029-006)
文摘Novel models （2× 1） of Si（001）-SiO2 interface structure have been established. The method of the first-principle General Gradient Approximation （GGA） is employed to structurally optimize the established theoretical models under the K-point space of periodic boundary condition. The structures after optimization have been analyzed, and the results show that the interfaces present in disordered state and both Si-O-Si and Si=O structures exist. Meanwhile, the bonding of surface structure is analyzed via the graphics of electron localization function（ELF）.
基金supported by the National Natural Science Foundation of China(Nos.61106080,61275042)the National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2013ZX02305)
文摘We investigate the effects of NO annealing and forming gas （FG） annealing on the electrical properties of a SiO2/SiC interface by low-temperature conductance measurements. With nitrogen passivation, the density of interface states （DIT） is significantly reduced in the entire energy range, and the shift of flatband voltage, AVFB, is effectively suppressed to less than 0.4 V. However, very fast states are observed after NO annealing and the response frequencies are higher than 1 MHz at room temperature. After additional FG annealing, the DIT and AVFB are further reduced. The values of the DIT decrease to less than 1011 cm-2 eV- 1 for the energy range of Ec - ET 〉/0.4 eV. It is suggested that the fast states in shallow energy levels originated from the N atoms accumulating at the interface by NO annealing. Though FG annealing has a limited effect on these shallow traps, hydrogen can terminate the residual Si and C dangling bonds corresponding to traps at deep energy levels and improve the interface quality further. It is indicated that NO annealing in conjunction with FG annealing will be a better post-oxidation process method for high performance SiC MOSFETs.
基金This work was supported by the Natural Science Foundation of Beijing (Grant Nos. 2012011 and 19890310).
文摘Ta is often used as a buffer layer in magnetic multilayers. In this study, Ta/Ni81Fe19/Ta multilayers were deposited by magnetron sputtering on sing-crystal Si with a 300-nm-thick SiO2 film. The composition and chemical states at the interface region of SiO2/Ta were studied using the X-ray photoelectron spectroscopy (XPS) and peak decomposition technique. The results show that there is an "intermixing layer" at the SiO2/Ta interface due to a thermody-namically favorable reaction: 15 SiO2+37 Ta = 6 Ta2O5 + 5 Ta5Si3. Therefore, the Ta buffer layer thickness used to induce NiFe (111) texture increases.
基金Project supported by the National Natural Science Foundation of China(Nos.51272202,61234006,61274079)
文摘The effect of the different re-oxidation annealing （ROA） processes on the SiO2/SiC interface charac- teristics has been investigated. With different annealing processes, the flat band voltage, effective dielectric charge density and interface trap density are obtained from the capacitance-voltage curves. It is found that the lowest interface trap density is obtained by the wet-oxidation annealing process at 1050 ℃ for 30 min, while a large num- ber of effective dielectric charges are generated. The components at the SiO2/SiC interface are analyzed by X-ray photoelectron spectroscopy （XPS） testing. It is found that the effective dielectric charges are generated due to the existence of the C and H atoms in the wet-oxidation annealing process.
文摘Four kinds of Mg alloys reinforced with carbon fibres were fabricated by a gas pressure infiltration technique. The fibres were pre-coated a SiO2 layer prior to fabrication. DifFerent microstructures and interactions in the fibre-matrix interface of these composites were observed by transmission electron microscopy （TEM）. The results showed that the interracial interaction strongly depended on the content of Al in the Mg-based matrices. The microstructure of the interface could then be controlled by adjusting the Al content of the Mgbased matrix. In addition, fibres extracted from different Mg-based matrix all had some degradation owing to the interracial reaction and the fibre-matrix interdiffusion.
