Boron carbide(B4C)coatings have high reflectivity and are widely used as mirrors for free-electron lasers in the x-ray range.However,B4C coatings fabricated by direct-current magnetron sputtering show a strong compres...Boron carbide(B4C)coatings have high reflectivity and are widely used as mirrors for free-electron lasers in the x-ray range.However,B4C coatings fabricated by direct-current magnetron sputtering show a strong compressive stress of about-3 GPa.By changing the argon gas pressure and nitrogen-argon gas mixing ratio,we are able to reduce the intrinsic stress to less than-1 GPa for a 50-nm-thick B4C coating.It is found that the stress in a coating deposited at 10 m Torr is-0.69 GPa,the rms roughness of the coating surface is 0.53 nm,and the coating reflectivity is 88%,which is lower than those of coatings produced at lower working pressures.When the working gas contains 8%nitrogen and 92%argon,the B4 C coating shows not only-1.19 GPa stress but also a low rms roughness of 0.16 nm,and the measured reflectivity is 93%at the wavelength of 0.154 nm.展开更多
Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green＇s function approach. The characteristic of conductance is obtained at zero temp...Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green＇s function approach. The characteristic of conductance is obtained at zero temperature. We find that competition between spin-exchange interaction on the spin site and spin-orbit interaction in the barriers dominates the resonant behavior of conductance. In a parallel configuration, conductance peaks have identical amplitude. With the angle θ increasing, the width of resonant peaks is broadened or narrowed for different spin coherent states. In an anti-parallel case, spin-flip tunneling in the barriers will essentially enhance amplitude of the conductance peak.展开更多
The magnetic properties of a mixed spin-2 and spin-1/2 ferromagnetic diamond chain are studied by effective-field theory and Monte Carlo（MC） simulation based on the Ising model.The temperature dependences of magneti...The magnetic properties of a mixed spin-2 and spin-1/2 ferromagnetic diamond chain are studied by effective-field theory and Monte Carlo（MC） simulation based on the Ising model.The temperature dependences of magnetization,magnetic susceptibility,internal energy,and specific heat are studied,respectively.The exchange interaction dependences of magnetization and the critical temperature are calculated by MC simulation.The changes of magnetization depending on the field increasing and then the field decreasing under steady-static conditions are also given.展开更多
采用以量子力学为基础的半经验计算方法—–自洽和环境依赖的原子轨道线性理论,预测了类α-石墨炔的碳锗炔结构.研究了α-碳锗炔的稳定结构、电子结构以及热力学稳定性,得到其最稳定的构型是Ge原子在六元环的六个顶角处,晶格常数为8.686...采用以量子力学为基础的半经验计算方法—–自洽和环境依赖的原子轨道线性理论,预测了类α-石墨炔的碳锗炔结构.研究了α-碳锗炔的稳定结构、电子结构以及热力学稳定性,得到其最稳定的构型是Ge原子在六元环的六个顶角处,晶格常数为8.686?的六角原胞构成的单层平面蜂窝状结构.该结构是带隙为1.078 e V的半导体.α-碳锗炔在很高的温度下都可以保持稳定,直到2280 K时其长程有序态才被破坏,当体系低于此温度时,可以通过降温使其恢复到零温时的稳定平面结构.展开更多
基金Supported by the National Key R&D Program of China under Grant No 2016YFA0401304the National Natural Science Foundation of China under Grant Nos 61621001,U1732268 and 11875203the Shanghai Municipal Science and Technology Major Project under Grant No 2017SHZDZX02
文摘Boron carbide(B4C)coatings have high reflectivity and are widely used as mirrors for free-electron lasers in the x-ray range.However,B4C coatings fabricated by direct-current magnetron sputtering show a strong compressive stress of about-3 GPa.By changing the argon gas pressure and nitrogen-argon gas mixing ratio,we are able to reduce the intrinsic stress to less than-1 GPa for a 50-nm-thick B4C coating.It is found that the stress in a coating deposited at 10 m Torr is-0.69 GPa,the rms roughness of the coating surface is 0.53 nm,and the coating reflectivity is 88%,which is lower than those of coatings produced at lower working pressures.When the working gas contains 8%nitrogen and 92%argon,the B4 C coating shows not only-1.19 GPa stress but also a low rms roughness of 0.16 nm,and the measured reflectivity is 93%at the wavelength of 0.154 nm.
基金Supported by National Natural Science Foundation of China under Grant No. 10674092Shanghai Leading Academic Disciplines Project under Grant No. S30105
文摘Spin-polarized transport through a precessing magnetic spin coupled to ferromagnetic electrodes is studied using a non-equilibrium Green＇s function approach. The characteristic of conductance is obtained at zero temperature. We find that competition between spin-exchange interaction on the spin site and spin-orbit interaction in the barriers dominates the resonant behavior of conductance. In a parallel configuration, conductance peaks have identical amplitude. With the angle θ increasing, the width of resonant peaks is broadened or narrowed for different spin coherent states. In an anti-parallel case, spin-flip tunneling in the barriers will essentially enhance amplitude of the conductance peak.
基金Project supported by the Shanghai Leading Academic Disciplines Project,China (Grant No. T0104)the National Natural Science Foundation of China(Grant No. 10674092)
文摘The magnetic properties of a mixed spin-2 and spin-1/2 ferromagnetic diamond chain are studied by effective-field theory and Monte Carlo（MC） simulation based on the Ising model.The temperature dependences of magnetization,magnetic susceptibility,internal energy,and specific heat are studied,respectively.The exchange interaction dependences of magnetization and the critical temperature are calculated by MC simulation.The changes of magnetization depending on the field increasing and then the field decreasing under steady-static conditions are also given.
文摘采用以量子力学为基础的半经验计算方法—–自洽和环境依赖的原子轨道线性理论,预测了类α-石墨炔的碳锗炔结构.研究了α-碳锗炔的稳定结构、电子结构以及热力学稳定性,得到其最稳定的构型是Ge原子在六元环的六个顶角处,晶格常数为8.686?的六角原胞构成的单层平面蜂窝状结构.该结构是带隙为1.078 e V的半导体.α-碳锗炔在很高的温度下都可以保持稳定,直到2280 K时其长程有序态才被破坏,当体系低于此温度时,可以通过降温使其恢复到零温时的稳定平面结构.
