A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.Th...A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.The extracted parameters from our model were tOX=20 nm,ND=1×1016cm 3,tSSi=13.2 nm,consistent with the experimental values.The results show that the simulation results agree with experimental data well.It is found that the plateau can be strongly affected by doping concentration,strained-Si layer thickness and mass fraction of Ge in the SiGe layer.The model has been implemented in the software for strained silicon MOSFET parameter extraction,and has great value in the design of the strained-Si/SiGe devices.展开更多
Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitanc...Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitance-voltage(C-V)characteristics.Such an algorithm treats the device as a parallel-plane junction and ignores the influence of the terminations.The epitaxy layer doping concentration tends to be overestimated and the thickness underestimated.In order to obtain the epitaxy layer parameters with higher accuracy,a new algorithm applicable for devices with field limited ring(FLR)terminations is proposed in this paper.This new algorithm is also based on the C-V characteristics and considers the extension manner of the depletion region under the FLR termination.Such an extension manner depends on the design parameters of the FLR termination and is studied in detail by simulation and modeling.The analytical expressions of the device C-V characteristics and the effective doping profile are derived.More accurate epitaxy layer parameters can be extracted by fitting the effective doping profile expression to the C-V doping profile calculated from the C-V characteristics.The relationship between the horizontal extension width and the vertical depth of the depletion region is also acquired.The credibility of the new algorithm is verified by experiments.The applicability of our new algorithm to FLR/field plate combining terminations is also discussed.Our new algorithm acts as a powerful tool for analyses and improvements of power devices.展开更多
Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is n...Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is not well centralized around 50 d B, and that some hits with large amplitudes, usually larger than 70 d B, occur in the early stages of each test, which is different from the findings from static and low-loading-rate tests. Furthermore, the dominant frequency range of the recorded acoustic emission waveforms is between 300 k Hz and 500 k Hz, and frequency components higher than 500 k Hz are not significant. The hit with the largest values of amplitude, counts, signal strength, and absolute energy in each test, displays a waveform with similar frequency characteristics and greater correlation with the waveform obtained from the elastic input bar of the split Hopkinson pressure bar system compared with the waveforms of the other hits. This indicates that the hit with the largest values of amplitude, counts, signal strength, and absolute energy is generated by elastic wave propagation instead of fracture within the rock specimen.展开更多
A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on tile epitaxial layer of a 4H-SiC （0001） 80N-/N＋ substrate, has been...A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on tile epitaxial layer of a 4H-SiC （0001） 80N-/N＋ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties （1 × 10^14 cm^-2） and low gate-leakage current （IG = 1 × 10^-3 A/cm 2@Eox = 8 MV/cm）. Analysis of the current conduction mecha- nism on the deposited Al2O3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler-Nordheim （FN） tuaneling, the Frenkel-Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV, which can meet the requirements of silicon carbide metal-insulator-semiconductor transistor devices.展开更多
A combined characteristic-based split algorithm and all adaptive meshing technique for analyzing two-dimensional viscous incompressible flow are presented. Tile method uses the three-node triangular element with equal...A combined characteristic-based split algorithm and all adaptive meshing technique for analyzing two-dimensional viscous incompressible flow are presented. Tile method uses the three-node triangular element with equal-order interpolation functions for all variables of tile velocity components and pressure. The main advantage of the combined nlethod is that it inlproves the sohltion accuracy by coupling an error estinla- tion procedure to an adaptive meshing technique that generates small elements in regions with a large change ill sohmtion gradients, mid at the same time, larger elements in the other regions. The performance of the combined procedure is evaluated by analyzing one test case of the flow past a cylinder, for their transient and steady-state flow behaviors.展开更多
In this paper, we combine a split least-squares procedure with the method of characteristics to treat convection-dominated parabolic integro-differential equations. By selecting the least-squares functional properly, ...In this paper, we combine a split least-squares procedure with the method of characteristics to treat convection-dominated parabolic integro-differential equations. By selecting the least-squares functional properly, the procedure can be split into two independent sub-procedures, one of which is for the primitive unknown and the other is for the flux. Choosing projections carefully, we get optimal order H^1 （Ω） and L^2（Ω） norm error estimates for u and sub-optimal （L^2（Ω））^d norm error estimate for σ. Numerical results are presented to substantiate the validity of the theoretical results.展开更多
Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harve...Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harvesting. In order to study the influence of this practice on the technological characteristics of cotton fiber, a study was undertaken in three production zones in Côte d’Ivoire. In the present study, seed cotton was harvested at 50%, 75% and 100% boll opening. After ginning, the fibers were analyzed on an HVI chain and their main technological characteristics were evaluated. Results: The results obtained show that regardless of the area, the crop splitting influences the parameters studied, such as the length, short fiber rate, tenacity, brightness and yellowness index of the fiber. Thus, harvesting at 50% capsule opening improves the fiber length by 1.5 mm, tenacity by 1.04 g/tex and brightness by 1.23, while reducing the short fiber rate by 0.84% and the yellowness index by 0.47. As for harvesting at 75% capsule opening, it increases the length by 0.72 mm, tenacity by 0.79 g/tex and brightness by 1.13, while decreasing the short fiber rate by 0.69% and the yellowness index by 0.45. Conclusion: Splitting the cotton harvest improves the quality of the fiber. It is therefore a practice to be recommended to producers in order to preserve the quality of the fiber, especially that carried out at 50% opening of the cotton bolls.展开更多
基金Projects(51308040203,6139801)supported by National Ministries and Commissions,ChinaProjects(72105499,72104089)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2010JQ8008)supported by the Natural Science Basic Research Plan in Shaanxi Province of China
文摘A physically based analytical model was developed to predict the performance of the plateau observed in the gate C-V characteristics of strained-Si/SiGe pMOSFET.Experimental results were used to validate this model.The extracted parameters from our model were tOX=20 nm,ND=1×1016cm 3,tSSi=13.2 nm,consistent with the experimental values.The results show that the simulation results agree with experimental data well.It is found that the plateau can be strongly affected by doping concentration,strained-Si layer thickness and mass fraction of Ge in the SiGe layer.The model has been implemented in the software for strained silicon MOSFET parameter extraction,and has great value in the design of the strained-Si/SiGe devices.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB0104701)。
文摘Doping concentration and thickness of an epitaxy layer are the most essential parameters for power devices.The conventional algorithm extracts these two parameters by calculating the doping profile from its capacitance-voltage(C-V)characteristics.Such an algorithm treats the device as a parallel-plane junction and ignores the influence of the terminations.The epitaxy layer doping concentration tends to be overestimated and the thickness underestimated.In order to obtain the epitaxy layer parameters with higher accuracy,a new algorithm applicable for devices with field limited ring(FLR)terminations is proposed in this paper.This new algorithm is also based on the C-V characteristics and considers the extension manner of the depletion region under the FLR termination.Such an extension manner depends on the design parameters of the FLR termination and is studied in detail by simulation and modeling.The analytical expressions of the device C-V characteristics and the effective doping profile are derived.More accurate epitaxy layer parameters can be extracted by fitting the effective doping profile expression to the C-V doping profile calculated from the C-V characteristics.The relationship between the horizontal extension width and the vertical depth of the depletion region is also acquired.The credibility of the new algorithm is verified by experiments.The applicability of our new algorithm to FLR/field plate combining terminations is also discussed.Our new algorithm acts as a powerful tool for analyses and improvements of power devices.
基金Projects(51204206,41272304,41372278) supported by the National Natural Science Foundation of ChinaProject(20110162120057) supported by Ph D Program Foundation of Ministry of Education ChinaProject(201012200232) supported by the Freedom Explore Program of Central South University,China
文摘Acoustic emission tests were performed using a split Hopkinson pressure bar system(SHPB) on 50-mm-diameter bars of granite, limestone, sandstone and skarn. The results show that the amplitude distribution of hits is not well centralized around 50 d B, and that some hits with large amplitudes, usually larger than 70 d B, occur in the early stages of each test, which is different from the findings from static and low-loading-rate tests. Furthermore, the dominant frequency range of the recorded acoustic emission waveforms is between 300 k Hz and 500 k Hz, and frequency components higher than 500 k Hz are not significant. The hit with the largest values of amplitude, counts, signal strength, and absolute energy in each test, displays a waveform with similar frequency characteristics and greater correlation with the waveform obtained from the elastic input bar of the split Hopkinson pressure bar system compared with the waveforms of the other hits. This indicates that the hit with the largest values of amplitude, counts, signal strength, and absolute energy is generated by elastic wave propagation instead of fracture within the rock specimen.
基金supported by the 2010 School Fundamental Scientific Research Fund of Xidian University (Grant No. K50510250008)
文摘A 4H-silicon carbide metal-insulator-semiconductor structure with ultra-thin Al2O3 as the gate dielectric, deposited by atomic layer deposition on tile epitaxial layer of a 4H-SiC （0001） 80N-/N＋ substrate, has been fabricated. The experimental results indicate that the prepared ultra-thin Al2O3 gate dielectric exhibits good physical and electrical characteristics, including a high breakdown electrical field of 25 MV/cm, excellent interface properties （1 × 10^14 cm^-2） and low gate-leakage current （IG = 1 × 10^-3 A/cm 2@Eox = 8 MV/cm）. Analysis of the current conduction mecha- nism on the deposited Al2O3 gate dielectric was also systematically performed. The confirmed conduction mechanisms consisted of Fowler-Nordheim （FN） tuaneling, the Frenkel-Poole mechanism, direct tunneling and Schottky emission, and the dominant current conduction mechanism depends on the applied electrical field. When the gate leakage current mechanism is dominated by FN tunneling, the barrier height of SiC/Al2O3 is 1.4 eV, which can meet the requirements of silicon carbide metal-insulator-semiconductor transistor devices.
文摘A combined characteristic-based split algorithm and all adaptive meshing technique for analyzing two-dimensional viscous incompressible flow are presented. Tile method uses the three-node triangular element with equal-order interpolation functions for all variables of tile velocity components and pressure. The main advantage of the combined nlethod is that it inlproves the sohltion accuracy by coupling an error estinla- tion procedure to an adaptive meshing technique that generates small elements in regions with a large change ill sohmtion gradients, mid at the same time, larger elements in the other regions. The performance of the combined procedure is evaluated by analyzing one test case of the flow past a cylinder, for their transient and steady-state flow behaviors.
基金The NSF(11101431 and 11201485)of Chinathe NSF(ZR2010AL020)of Shandong Province
文摘In this paper, we combine a split least-squares procedure with the method of characteristics to treat convection-dominated parabolic integro-differential equations. By selecting the least-squares functional properly, the procedure can be split into two independent sub-procedures, one of which is for the primitive unknown and the other is for the flux. Choosing projections carefully, we get optimal order H^1 （Ω） and L^2（Ω） norm error estimates for u and sub-optimal （L^2（Ω））^d norm error estimate for σ. Numerical results are presented to substantiate the validity of the theoretical results.
文摘Context: The major challenges of cotton cultivation in Côte d’Ivoire are the improvement of field yields and fiber quality. One of the methods proposed to ensure the quality of cotton fiber is split cotton harvesting. In order to study the influence of this practice on the technological characteristics of cotton fiber, a study was undertaken in three production zones in Côte d’Ivoire. In the present study, seed cotton was harvested at 50%, 75% and 100% boll opening. After ginning, the fibers were analyzed on an HVI chain and their main technological characteristics were evaluated. Results: The results obtained show that regardless of the area, the crop splitting influences the parameters studied, such as the length, short fiber rate, tenacity, brightness and yellowness index of the fiber. Thus, harvesting at 50% capsule opening improves the fiber length by 1.5 mm, tenacity by 1.04 g/tex and brightness by 1.23, while reducing the short fiber rate by 0.84% and the yellowness index by 0.47. As for harvesting at 75% capsule opening, it increases the length by 0.72 mm, tenacity by 0.79 g/tex and brightness by 1.13, while decreasing the short fiber rate by 0.69% and the yellowness index by 0.45. Conclusion: Splitting the cotton harvest improves the quality of the fiber. It is therefore a practice to be recommended to producers in order to preserve the quality of the fiber, especially that carried out at 50% opening of the cotton bolls.
