La掺杂AgSnO_2触头材料的电性能（英文）

由于Cd有毒性,AgSnO_2触头材料逐渐取代了AgCdO成为新型触头材料,但由于AgSnO_2触头材料中的SnO_2近乎绝缘,使得触头材料的接触电阻增大,故改善SnO_2的导电性是急需解决的重大难题。本文提出了一种简单的、低成本的La掺杂AgSnO_2触头材料的设计方法。采用模拟计算的方法,利用第一性原理的密度泛函理论平面波超软赝势法,建立了SnO_2以及不同比例La掺杂的SnO_2超晶胞模型,在对其进行几何优化之后分别研究了La掺杂比为50%、25%、16.67%、12.5%、8.34%的SnO_2材料的电子结构,并研究了其晶格参数、能带结构和态密度等。结果表明,掺杂后材料晶胞体积变大。La的5d轨道进入导带,使得导带底向低能端移动,禁带宽度变小。最终得出La掺杂比为16.67%时导电性最佳。最后进行了不同掺杂比下触头材料的电接触性能试验,得到了接触电阻和燃弧能量等电接触性能参数并验证了模拟结果。因此,本文的研究为触头材料的发展和应用提供了理论依据。     

双钙钛矿Sr_2Fe_(1-x)Cr_xMoO_6电子结构与磁学性质的第一性原理研究

利用第一性原理系统计算了Sr2Fe1-x CrxMoO6体系中不同Cr含量(x=0,1/3,0.5和1)所对应Sr2Fe1-xCrxMoO6晶胞结构的电子结构和磁学性质。计算结果表明,体系的晶格常数、总磁矩及Fe离子磁矩由于Cr掺杂而降低,晶格发生畸变,并发现当Cr掺杂含量增加至0.5时自旋向上费米面附近态密度明显增加,超胞呈金属性,但Sr2Fe1-xCrxMoO6(x=0,1/3,0.5和1)仍保持半金属性。得出的计算结果与现有的实验和理论值吻合较好,该结果为其材料的进一步实际应用提供了理论依据。     

La掺杂AgSnO2触头材料的电性能

由于Cd有毒性,AgSnO2触头材料逐渐取代了 AgCdO 成为新型触头材料,但由于AgSnO2触头材料中的SnO2近乎绝缘,使得触头材料的接触电阻增大,故改善SnO2的导电性是急需解决的重大难题.本文提出了一种简单的、低成本的La掺杂AgSnO2触头材料的设计方法.采用模拟计算的方法,利用第一性原理的密度泛函理论平面波超软赝势法,建立了SnO2以及不同比例La掺杂的SnO2超晶胞模型,在对其进行几何优化之后分别研究了 La掺杂比为50%、25%、16. 67%、12. 5%、8.34% 的SnO2材料的电子结构,并研究了其晶格参数、能带结构和态密度等.结果表明,掺杂后材料晶胞体积变大. La的5d轨道进入导带,使得导带底向低能端移动,禁带宽度变小.最终得出La掺杂比为16.67% 时导电性最佳.最后进行了不同掺杂比下触头材料的电接触性能试验,得到了接触电阻和燃弧能量等电接触性能参数并验证了模拟结果.因此,本文的研究为触头材料的发展和应用提供了理论依据.     

Na掺杂对闪锌矿ZnS电子结构和光学性质的第一性原理浅析

采用基于密度泛函理论(DFT)的第一性原理方法,在广义梯度近似(GGA)框架下,研究了纯净闪锌矿ZnS-B3和Na掺杂ZnS后的晶体结构、电子结构和光学性质。详细分析了不同Na掺杂浓度对ZnS的晶格常数、电子态密度和能带结构的影响,讨论了费米能级附近的电子组态对ZnS光学性质的影响。结果表明,掺杂Na对ZnS光学性能有极大的影响,当Na离子掺杂浓度为6.25%(原子分数)时,表现出较好的综合光学性质;当掺杂浓度为12.5%(原子分数)时,体系有效负电荷离子浓度增加,S3p态穿过费米能面,引起S3p态电子产生跃迁,在低能量红外区域产生新介电峰,引起光吸收,降低了ZnS材料的透红外性能。理论预测结果与文献报道的实验结果相吻合。     

La、Sb共掺杂SnO 2电性能的第一性原理研究

基于密度泛函理论的第一性原理方法,使用软件构建了Sb、La单掺杂与共掺杂SnO_2的超晶胞模型,几何优化并计算分析其晶体结构、能带结构、态密度及布居。结果显示:与单掺杂比,La-Sb共掺后的热稳定性最高,仍是直接带隙材料。Sb的5s、5p态和La的5p态在导带底引入杂质能级,使得导带下移,带隙变小,载流子跃迁所需的能量减少;共掺杂时电子共有化程度最高,电子转移加剧。共掺杂后SnO_2材料的导电性能改善最好,分析结果可作为后续材料发展的理论依据。     

Zr掺杂CeO_2电子结构的密度泛函计算

根据密度泛函理论,采用"总体能量平面波"超软赝势方法,对不同的Zr掺杂浓度的CeO2晶体几何结构进行了优化,从理论上给出了Zr掺杂CeO2晶体结构参数及性质;计算了Zr掺杂情况下CeO2晶体的总体能量、能带结构、总波态密度和分波态密度。研究表明,Zr3+取代Ce4+及Ce3+后晶体的稳定性增强,同时掺杂Zr使得晶格中自由载流子电子和O2p的波态密度的增加,使得晶格中Ce3+和Ce4+之间的变价可能性增大。     

掺杂纳米SnO_2-Al_2O_3/Cu新型电触头复合材料的制备及耐磨性能

为满足低压电器对于高品质电触头材料的迫切需求,同时保护稀缺资源、降低电触头成本,采用粉末冶金工艺制备了掺杂纳米SnO_2-Al_2O_3/Cu新型电触头复合材料,并对其电导率、硬度及耐磨性能进行了研究。结果表明:复烧与冷变形工艺均可显著提高复合材料的烧结质量、密度、电导率与硬度。随着纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量增加,掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的硬度与耐磨性能表现出了相同的变化规律,即先升高后降低。当纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量为0.80wt%时,复合材料的硬度与耐磨性能均达到最优;而当纳米Al_2O_3及掺杂纳米SnO_2颗粒的总含量保持0.80wt%不变时,随纳米Al_2O_3颗粒的含量增加,掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的硬度与耐磨性能改善;当掺杂纳米SnO_2颗粒的含量为0时,复合材料的耐磨性能达到了最优。因此较之掺杂纳米SnO_2颗粒,纳米Al_2O_3颗粒对掺杂纳米SnO_2-Al_2O_3/Cu电触头复合材料的耐磨性能有更显著的提高作用。     

Sb掺杂闪锌矿GaAs电子结构和光学性质第一性原理研究

采用基于密度泛函理论(DFT)框架下广义梯度近似平面波超软赝势法,计算了不同浓度Sb掺杂闪锌矿GaAs体系GaAs1-xSbx(x=0,0.25,0.5,0.75,1)的电子结构和光学性质,包括能带、态密度、复介电函数和吸收系数。计算结果表明,Sb掺杂导致体系晶格常数线性增大,并使得体系导带和价带组成发生改变,禁带宽度呈二次多项式变化。随着掺杂浓度的增加,体系静态介电常数线性增大,吸收带边出现了明显的红移现象。分析了掺杂Sb诱发GaAs1-xSbx体系的电子和光学性质改变,为Sb掺杂闪锌矿GaAs在光电子学和微电子学方面的实际应用提供了一定的理论依据。     

Cr、La共掺杂SnO2电子结构和力学性能的第一性原理研究

电触头材料AgSnO_2的第二相SnO_2是一种硬度高较脆,难以加工的宽禁带半导体材料。基于密度泛函理论的第一性原理和平面波超软赝势法,应用Materials studio软件下CASTEP模块建立Cr、La单掺、共掺SnO_2晶胞模型,掺杂比例为16.67%,几何优化后分别计算焓变值、电荷布局、能带结构、态密度、弹性模量,分析研究掺杂后SnO_2电学性能和力学性能的变化。结果表明,各SnO_2体系在热力学和动力学上都是稳定的,掺杂后Sn-O键布局数减小,Sn、O间电荷重叠减弱,O原子向杂质原子Cr移动,Cr-O成键能力强,共价性高,电子转移剧烈。掺杂后带隙值减小,导电性提高,其中Cr-La共掺SnO_2体系由于Cr 3d和La 5d轨道的杂化作用,在费米能级处形成杂质能级,电子跃迁所需能量大幅减小,导电性最好。力学性能方面,各SnO_2体系的剪切模量和杨氏模量变化趋势是相似的。单掺Cr可提高SnO_2抵抗剪切形变和弹性形变能力,硬度、刚度增强,韧性、延展性较差.单掺La和共掺Cr-La可提高SnO_2韧性,减小硬度,改善加工性能。     

Mn掺杂浓度对Mn:MgAl_2O_4电子结构和光学性质的影响

采用密度泛函理论(DFT)的平面波超软赝势(PW-USP)和广义梯度近似(GGA)对不同锰离子掺杂浓度的掺杂镁铝尖晶石晶体Mg1-xMnxAl2O4(x=0、0.125、0.5)的晶体结构、电子结构和光学性质进行了计算.解释了锰离子掺杂浓度使晶格常数变化的微观机制;分析了锰离子掺杂浓度对电子结构和光学系数的影响.结果表明,锰离子掺杂浓度的增加使掺杂晶体的带隙降低.价带变窄,杂质能级展宽.掺杂晶体的导带对掺杂浓度的变化较为敏感.锰掺杂使可见光区吸收增大,且掺杂浓度越高可见光区光学吸收越强,起吸收边越向长波方向移动,即发生红移,与实验结果一致.     

Recent progress in p-type doping and optical properties of SnO2 nanostructures for optoelectronic device applications

SnO(2) semiconductor is a host material for ultraviolet optoelectronic devices applications because of its wide band gap (3.6 eV), large exciton binding energy (130 meV) and exotic electrical properties and has attracted great interests. The renewed interest is fueled by the availability of exciton emission in nanostructures, high quality epitaxial films, p-type conductivity, and heterojunction light emitting devices. This review begins with a survey of the patents and reports on the recent developments on SnO2 films. We focus on the epitaxial growth, p-type doping and photoluminescence properties of SnO(2) films and nanostructures, including the achievements in our group. Finally, the applications of SnO(2) nanostructures to optoelectronic devices including heterojunction light emitting devices, photodetectors and photovoltaic cells will be discussed.     

Density functional calculations on the mechanical properties of nitrogen or oxygen doped crystalline Ge2Sb2Te5

The mechanical properties of pure and doped crystalline Ge2Sb2Te5 were investigated by using density functional calculations. Nitrogen or oxygen was added at either the interstitial or substitutional sites of cubic Ge2Sb2Te5. The lattice parameter, elastic stiffness and related moduli were investigated from the viewpoint of the doping concentration, dopant species, dopant states and film direction. The effect of the doping concentration was more dominant than those of the dopant species and their states on the non-directionality properties, such as the bulk modulus and lattice parameter. It turned out that Ge2Sb2Te5 became slightly more rigid as the doping concentration of nitrogen or oxygen increased. On the other hand, the effect of the film direction on the directional properties, such as the biaxial modulus of the Ge2Sb2Te5 film, was found to be more predominant than that of doping. The biaxial modulus of the (001) oriented film was calculated to be much higher than those of the other films, indicating that the (001) film is the most vulnerable to thermal stress.     

稀土La掺杂Mg2Si的几何结构、弹性性能和电子结构的第一性原理研究EI北大核心CSCD

采用密度泛函理论(DFT)的第一性原理平面波赝势方法对稀土元素镧(La)掺杂Mg2Si的几何结构、弹性性能和电子结构进行计算与分析。首先,结合形成焓、Born力学稳定性以及差分电荷密度的结果可知,掺杂稀土元素La之后,形成的Mg8Si4La和Mg8Si3La均不能稳定存在,La掺杂的Mg2Si优先占据体系Mg原子的位置;其次,晶体的体模量(B),剪切模量(G),杨氏模量(E),泊松比(ν),以及各向异性系数(A)的计算结果表明本征Mg2Si为脆性相,而Mg7Si4La为韧性相,掺杂La可以提高Mg2Si的延展性;最后,态密度、Mulliken布居数和电荷差分密度的计算结果表明掺杂稀土镧后费米面向高能级区域偏离,进入导带,提高了Mg2Si的导电性。     

Sb掺杂对N型half-Heusler材料热电性能的影响

研究了Sb掺杂对N型half-Heusler化合物Zr_0.25Hf_0.25Ti_0.5NiSn_1-xSb_x (x=0、0.002、0.005、0.01、0.02、0.03)热电传输特性的影响。结果显示, 随着Sb掺杂量增加, 材料的载流子浓度提高, 电阻率降低, 尤其是低温(<300 K)电阻率下降显著, 赛贝克系数降低, 且取得最大赛贝克系数的温度向高温端移动, 最大功率因子增加~20%, 材料的热导率增大, 主要是电子热导率提高的贡献, 晶格热导率影响不大; 当Sb掺杂量较低时(x<0.01), 材料的最大热电性能优值ZT值在0.77左右, 掺杂量x=0.005的样品ZT值在整个温度区间内最优。     

Structural,elastic, and lattice dynamical properties of Germanium diiodide (GeI2)

To investigate the structural, elastic, and lattice dynamical properties of the germanium diiodide, we have performed the first-principles calculations by using the local density approximation method based on density-functional theory. Some basic physical parameters such as lattice constant, bulk modulus and its first derivatives, elastic constants, shear modulus, Young’s modulus, and Poisson’s ratio are calculated. The phonon dispersion curves, electronic band-structures, and total and partial density of states have also been calculated for ground state C6 phase of GeI₂. Our results show that this structure has got 1.72 eV direct band gap. Our secondary results on the temperature-dependent behavior of thermodynamical properties such as entropy, heat capacity, internal energy, and free energy are also presented for the same compounds. The obtained results are in good agreement with the available experimental and other theoretical data.     

Tuning the electronic structure of the transparent conducting oxide Cu2O

The electronic structure of Cu₂O is important for its application as a p-type transparent conducting oxide (TCO). To be useful as a TCO, a material needs to show enhanced transparency in the visible range (band gap > 3 eV) as well as good conduction properties. While Cu₂O has too small a band gap, alloys of Cu₂O and Al₂O₃ or Cu₂O and alkaline earth oxides are known to display enhanced transparency, with little degradation of electrical properties. It is of interest to consider how to dope Cu₂O p-type, e.g. Cu vacancies (oxidation) or cationic dopants. We present a study of the electronic structure and effective hole masses of stoichiometric and oxidised Cu₂O and study metal cation doping, using density functional theory (DFT), to analyse p-type doping scenarios. We show that formation of a Cu vacancy is relatively facile, introducing delocalised hole states, with a light hole present. Substitutional cation doping with Al and Au/Ag is found to decrease the band gap but maintains a light hole effective mass necessary for p-type conduction.     

选区激光熔化成形的316L不锈钢点阵夹层结构的力学性能和能量吸收性能研究

目的 以选区激光熔化(SLM)成形的316L不锈钢点阵夹层结构为研究对象,研究单一、混合芯层对点阵夹层结构力学性能和能量吸收性能的影响,为轻质高强耐撞点阵夹层结构提供设计依据。方法 通过SLM成形技术,以316L不锈钢粉末为原材料,制备点阵夹层结构,利用扫描电镜对SLM成形的点阵夹层结构几何结构特征进行观察,利用准静态压缩实验对点阵夹层结构的力学性能和能量吸收性能进行研究。结果 在选定的SLM成形工艺参数下,SLM成形的点阵夹层结构芯层的连接杆表面存在一定的粗糙度且斜向连接杆的表面粗糙度比竖直连接杆的表面粗糙度大。在SLM成形的点阵夹层结构中,混合点阵夹层结构BFB和FBF的弹性模量分别为2 525.7 MPa和2 493.8 MPa,屈服强度分别为36.3 MPa和38.3 MPa,能量吸收分别为16 J和17.2 J,比吸能分别为1.21 J/g和1.36 J/g,其弹性模量、屈服强度、能量吸收和比吸能均优于单一BCCZ点阵夹层结构的。在准静态压缩过程中,BFB和FBF这2种混合点阵结构芯层的变形模式不同于单一BCCZ点阵结构芯层的。结论 与单一点阵夹层结构相比,2层BCCZ布置在中心、2层FCCZ位于上下面板旁边的FBF混合点阵夹层结构的能量吸收性能有所提高。     

Structural and electronic properties of CdTe1-xSex films and their application in solar cells

The performance improvement of conventional CdTe solar cells is mainly limited by doping concentration and minority carrier life time. Alloying CdTe with an isovalent element changes its properties, for example its band gap and behaviour of dopants, which has a significant impact on its performance as a solar cell absorber. In this work, the structural, optical, and electronic properties of CdTe_1-xSe_x films are examined for different Se concentrations. The band gap of this compound changes with composition with a minimum of 1.40 eV for x = 0.3. We show that with increasing x, the lattice constant of CdTe_1-xSe_x decreases, which can influence the solubility of dopants. We find that alloying CdTe with Se changes the effect of Cu doping on the p-type conductivity in CdTe_1-xSe_x, reducing the achievable charge carrier concentration with increasing x. Using a front surface CdTe_1-xSe_x layer, compositional, structural and electronic grading is introduced to solar cells. The efficiency is increased, mostly due to an increase in the short-circuit current density caused by a combination of lower band gap and a better interface between the absorber and window layer, despite a loss in the open-circuit voltage caused by the lower band gap and reduced charge carrier concentration.     

以第一性原理研究立方相CeO2的弹性、电子结构和光学性质

运用基于密度泛函理论(DFT)框架下的超软赝势平面波(USPP)方法,计算了立方相CeO2的几何结构、弹性性质、电子结构和光学性质,并采用HSE06杂化泛函矫正了带隙.所得晶格参数及体模量与先前文献报道数据基本吻合.计算出了二阶弹性常数及德拜温度值,并给出了能带结构、态密度、差分电荷密度的分布情况.最后,为了阐明CeO2的光学跃迁机制,计算并分析了其复介电常数、折射率、吸附光谱、反射光谱等光学性质.