用 Cu、In、Se三元扇形复合靶 ,采用射频磁控反应溅射技术 ,在低温 Indium Tin Oxide( ITO)透明导电基片上制备大面积均匀圆柱形 Cu In Se2 ( CIS)量子点。制备材料的化学计量比可通过三种单质的面积比率来调节。该制备方法具有成本低...用 Cu、In、Se三元扇形复合靶 ,采用射频磁控反应溅射技术 ,在低温 Indium Tin Oxide( ITO)透明导电基片上制备大面积均匀圆柱形 Cu In Se2 ( CIS)量子点。制备材料的化学计量比可通过三种单质的面积比率来调节。该制备方法具有成本低、操作简单、易于大型化等优点。平均量子点的大小可控制在 40到 80 nm之间 ,可通过改变溅射参数、ITO膜的晶相结构与表面形貌等因素来调节。展开更多
We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the ...We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage （I - V） curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I - V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.展开更多
Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, ...Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, power factor S2σ and dimensionless figure of merit, zT, for K3IO. It is found that K3IO exhibits relatively low lattice thermal conductivity of 0.93 W·m-1·K-1 at 300 K, which is lower than the value 1.26 W·m-1·K-1 of the classical TE material PbTe. This is due to the smaller phonon group velocity νg and smaller relaxation time τλ. The low lattice thermal conductivity can lead to excellent thermoelectric properties. Thus maximum zT of 2.87 is obtained at 700 K, and the zT = 0.41 at 300 K indicate that K3IO is a potential excellent room temperature TE material. Our research on K3IO shows that it has excellent thermoelectric properties, and it is a promising candidate for applications in fields in terms of thermoelectricity.展开更多
We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe ...We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe the strong correlation between 5 f electrons of a uranium atom, we employ the on-site Hubbard U correction term and optimize the correlation parameter of the bulk uranium dioxide. Then we give the structural and electronic properties of the ground state of uranium dioxide. Based on the accurate electronic structure, we calculate the complex dielectric function of UO2 and the related optieM properties, such as reflectivity, refractive index, extinction index, energy loss spectra, and absorption coefficient.展开更多
Based on first-principles plane-wave calculations,we firstly reconfirm that the Li+graphene complex can be taken as a hydrogen storage medium with capacity of 12.8wt%.Then metal adsorption properties of this Li+graphe...Based on first-principles plane-wave calculations,we firstly reconfirm that the Li+graphene complex can be taken as a hydrogen storage medium with capacity of 12.8wt%.Then metal adsorption properties of this Li+graphene system with different charge states are investigated.Finally,the hydrogen storage ability of the charging system is calculated.Our calculations show that adding positive charge on a Li+graphene composite results in a conspicuous reduction of Li2𝑡and Li2𝑞orbital occupation with respect to the C2𝑞state.As a result,a stronger bonding between Li and graphene is formed,and a special double-layer hydrogen adsorption structure has been found.Compared to the neutral system,utilizing the positive charged Li+graphene to store hydrogen molecules can solve the issue of clustering of metal atoms after releasing hydrogen,and can improve hydrogen storage capacity up to a gravimetric density of 20.4wt%,correspondingly one adsorbed Li atom can effectively absorb up to seven H 2 molecules.展开更多
Previous calculations show that the two-dimensional (2D) silicon carbide (SiC) honeycomb structure is a structurally stable monolayer. Following this, we investigate the electronic properties of the hydrogen and fluor...Previous calculations show that the two-dimensional (2D) silicon carbide (SiC) honeycomb structure is a structurally stable monolayer. Following this, we investigate the electronic properties of the hydrogen and fluorine functionalized SiC monolayer by first-principles calculations. Our results show that the functionalized monolayer becomes metallic after semi-hydrogenation or semi-fluorination, while the semiconducting properties are obtained by the full functionalization. Compared with the bare SiC monolayer, the band gap of the fully hydrogenated system is increased, in comparison with the decrease of the gap in the fully fluorinated case. As a result, the band gap can be tuned from 0.73 to 4.14 eV by the functionalization. In addition to the metal-semiconductor transition, hydrogenation and functionalization also realize a direct-indirect semiconducting transition in the 2D SiC monolayer. These results provide theoretical guidance for design of photoelectric devices based on the SiC monolayer.展开更多
基金Supported by the National Natural Science Foundation of China under Grant No 10404022, and the National Basic Research Programme of China under Grant No G2000067107.
文摘We investigate the non-equilibrium electron transport properties of double-barrier AlGaAs/GaAs/AlGaAs resonant- tunnelling devices in nonlinear bias using the time-dependent simulation technique. It is found that the bias step of the external bias voltage applied on the device has an important effect on the final current-voltage （I - V） curves. The results show that different bias step applied on the device can change the bistability, hysteresis and current plateau structure of the I - V curve. The current plateau occurs only in the case of small bias step. As the bias step increases, this plateau structure disappears.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11974302,11774396,and 11704322)the Shandong Natural Science Funds for Doctoral Program,China(Grant No.ZR2017BA017).
文摘Based on first-principles calculations, Boltzmann transport equation and semiclassical analysis, we conduct a detailed study on the lattice thermal conductivity κL, Seebeck coefficient S, electrical conductivity σ, power factor S2σ and dimensionless figure of merit, zT, for K3IO. It is found that K3IO exhibits relatively low lattice thermal conductivity of 0.93 W·m-1·K-1 at 300 K, which is lower than the value 1.26 W·m-1·K-1 of the classical TE material PbTe. This is due to the smaller phonon group velocity νg and smaller relaxation time τλ. The low lattice thermal conductivity can lead to excellent thermoelectric properties. Thus maximum zT of 2.87 is obtained at 700 K, and the zT = 0.41 at 300 K indicate that K3IO is a potential excellent room temperature TE material. Our research on K3IO shows that it has excellent thermoelectric properties, and it is a promising candidate for applications in fields in terms of thermoelectricity.
基金Supported by the New Century Excellent Talents in University in Ministry of Education of China under Grant No NCET-09-0867
文摘We report a study of the electronic structure and optical properties of uranium dioxide （U02） based on the ab-initio density-functional theory and using the generalized gradient approximation. To correctly describe the strong correlation between 5 f electrons of a uranium atom, we employ the on-site Hubbard U correction term and optimize the correlation parameter of the bulk uranium dioxide. Then we give the structural and electronic properties of the ground state of uranium dioxide. Based on the accurate electronic structure, we calculate the complex dielectric function of UO2 and the related optieM properties, such as reflectivity, refractive index, extinction index, energy loss spectra, and absorption coefficient.
基金Supported by the New Century Excellent Talents in University in Ministry of Education of China(NCET-09-0867)the Shandong Natural Science Foundation for Distinguished Young Scientists(No 2008JQ2).
文摘Based on first-principles plane-wave calculations,we firstly reconfirm that the Li+graphene complex can be taken as a hydrogen storage medium with capacity of 12.8wt%.Then metal adsorption properties of this Li+graphene system with different charge states are investigated.Finally,the hydrogen storage ability of the charging system is calculated.Our calculations show that adding positive charge on a Li+graphene composite results in a conspicuous reduction of Li2𝑡and Li2𝑞orbital occupation with respect to the C2𝑞state.As a result,a stronger bonding between Li and graphene is formed,and a special double-layer hydrogen adsorption structure has been found.Compared to the neutral system,utilizing the positive charged Li+graphene to store hydrogen molecules can solve the issue of clustering of metal atoms after releasing hydrogen,and can improve hydrogen storage capacity up to a gravimetric density of 20.4wt%,correspondingly one adsorbed Li atom can effectively absorb up to seven H 2 molecules.
基金Supported by the Program for New Century Excellent Talents in Universities of China under Grant No NCET-09-0867
文摘Previous calculations show that the two-dimensional (2D) silicon carbide (SiC) honeycomb structure is a structurally stable monolayer. Following this, we investigate the electronic properties of the hydrogen and fluorine functionalized SiC monolayer by first-principles calculations. Our results show that the functionalized monolayer becomes metallic after semi-hydrogenation or semi-fluorination, while the semiconducting properties are obtained by the full functionalization. Compared with the bare SiC monolayer, the band gap of the fully hydrogenated system is increased, in comparison with the decrease of the gap in the fully fluorinated case. As a result, the band gap can be tuned from 0.73 to 4.14 eV by the functionalization. In addition to the metal-semiconductor transition, hydrogenation and functionalization also realize a direct-indirect semiconducting transition in the 2D SiC monolayer. These results provide theoretical guidance for design of photoelectric devices based on the SiC monolayer.
