For the frequency range of I kHz-lOMHz, the interface state density of Ni contacts on p-GaN is studied using capacitance-voltage (C-V) and conductance-frequency-voltage (G-f-V) measurements at room temperature. To...For the frequency range of I kHz-lOMHz, the interface state density of Ni contacts on p-GaN is studied using capacitance-voltage (C-V) and conductance-frequency-voltage (G-f-V) measurements at room temperature. To obtain the real capacitance and interface state density of the Ni/p-GaN structures, the effects of the series resistance (Rs) on high-frequency (SMHz) capacitance values measured at a reverse and a forward bias are investigated. The mean interface state densities obtained from the CHF-CLF capacitance and the conductance method are 2 ×1012 e V-1 cm-2 and 0.94 × 1012 eV-1 cm-2, respectively. Furthermore, the interface state density derived from the conductance method is higher than that reported from the Ni/n-GaN in the literature, which is ascribed to a poor crystal quality and to a large defect density of the Mg-doped p-GaN.展开更多
An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents ...An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that TiCp/Al composite with 40~70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy (TEM). The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as (220)Al//(022)TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength (σ) and modulus (E) are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.展开更多
基金Supported by the Natural Science Foundation of Jiangxi Province under Grant No 20133ACB20005the Key Program of National Natural Science Foundation of China under Grant No 41330318+3 种基金the Key Program of Science and Technology Research of Ministry of Education under Grant No NRE1515the Foundation of Training Academic and Technical Leaders for Main Majors of Jiangxi Province under Grant No 20142BCB22006the Research Foundation of Education Bureau of Jiangxi Province under Grant No GJJ14501the Engineering Research Center of Nuclear Technology Application(East China Institute of Technology)Ministry of Education under Grant NoHJSJYB2016-1
文摘For the frequency range of I kHz-lOMHz, the interface state density of Ni contacts on p-GaN is studied using capacitance-voltage (C-V) and conductance-frequency-voltage (G-f-V) measurements at room temperature. To obtain the real capacitance and interface state density of the Ni/p-GaN structures, the effects of the series resistance (Rs) on high-frequency (SMHz) capacitance values measured at a reverse and a forward bias are investigated. The mean interface state densities obtained from the CHF-CLF capacitance and the conductance method are 2 ×1012 e V-1 cm-2 and 0.94 × 1012 eV-1 cm-2, respectively. Furthermore, the interface state density derived from the conductance method is higher than that reported from the Ni/n-GaN in the literature, which is ascribed to a poor crystal quality and to a large defect density of the Mg-doped p-GaN.
文摘An in-situ TiCp/Al composite was prepared by a thermal explosion/quick pressure method (TE/QP). The effect of Al content on the reaction temperature as well as the reaction rate has been studied. Phase constituents and the microstructure of the composites and the particle size of the reinforcement were analysed using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results have shown that TiCp/Al composite with 40~70 vol. pct TiC particle reinforcement and high relative density can be directly obtained by TE/QP. TiC is the only reaction product when Al content in Al-Ti-C system is no more than 60 vol. pct, but Al3Ti phase will also form when Al content is more than 60 vol. pct. Increasing Al content prolongs the initial reaction time, reduces the highest reaction temperature and the reaction rate, and decreases the size of TiC particles. In addition, the microstructure of TiCp/Al composite and the structure of interface between TiCp and Al are studied using SEM and transmission electron microscopy (TEM). The results show that the in-situ synthesized TiC particle has fcc cubic structure. The orientation between TiC particles and Al matrix can be described as (220)Al//(022)TiC and [112]Al//[011]TiC. Results of the mechanical property tests reveal that the ultimate strength (σ) and modulus (E) are 687 MPa and 142 GPa respectively when the Al content is 40 vol. pct. On contrary, 6 elongation increases by 3.2% with increasing Al content.