Ag、P掺杂ZnS的电子结构和光学性质的研究

利用密度泛函理论中的第一性原理计算掺杂Ag、P的ZnS材料,对掺杂Ag、P前后ZnS超晶胞的电子结构以及光学性质进行了分析研究。计算结果表明,掺入杂质后,价带顶出现杂质能级,费米能级进入价带,导致电导率增加,P 3p态电子形成的杂质态具有一定的局域化特性,故P在ZnS中的溶解度比较低,ZnS的光学性质在可见光区有比较明显的变化,而在高能区则比较相似。掺杂后,各谱线在低能区均产生了一个新的峰。     

掺杂 β-FeSi2光电特性研究

采用基于密度泛函理论的第一性原理赝势平面波方法,对B,N,Al,P掺杂的β-FeSi2的几何结构,电子结构和光学性质进行了计算和分析。结果表明,几何结构不仅受掺杂原子种类的影响,还和掺杂的位置有关;Al和P倾向于置换SiI位的Si原子,而B和N则倾向于置换SiII的Si原子;B和Al的掺入使β-FeSi2成为p型半导体,而N和P的掺入使它成为n型半导体;光学性质计算表明：N掺杂对β-FeSi2的复介电函数影响很小,B,N,Al和P的掺入能够在低能区增强电子跃迁,提高折射率和反射作用,并在反射率的最大值处削弱反射作用。这些结果为光电子材料β-FeSi2的设计和应用提供了理论指导。     

氧化锌p型共掺杂精细结构的第一性原理研究

计算了ZnO材料p型掺杂精细结构,分析了p型掺杂ZnO晶体的电子结构、电荷布局、电子态密度、差分电荷。所有计算都是基于密度泛函理论(DFT)框架下的第一原理平面波超软赝势方法。计算结果表明:掺杂Ⅴ族元素(N、P、As、In)的氧化锌材料在能隙中引入了深受主能级,载流子(空穴)局域于价带顶附近。而利用加入激活施主的共掺杂技术的计算结果却表明,受主能级向低能方向移动,形成了浅受主能级。同时,受主能级带变宽,非局域化特征明显。     

Cr掺杂纤锌矿GaN的磁性和光学性质

采用自旋极化密度泛函理论方法,对Cr掺杂纤锌矿GaN的能带结构和态密度进行计算,通过计算的能带结构和光学线性响应函数,系统讨论了Cr掺杂对纤锌矿GaN电子结构、磁学和光学属性的影响。计算结果显示:Cr掺杂纤锌矿GaN的反铁磁态具有半金属特征,铁磁态具有金属特性和磁性,磁矩主要源于费米能级附近的Cr 3d和N 2p能带发生劈裂导致自旋向上和自旋向下的电子的态密度不同所致。光学性质计算结果显示,Cr掺杂纤锌矿GaN的费米能级附近出现极大的介电峰,具有优异的发光性能,峰值对应于紫外波段,在高能区吸收峰发生了红移现象,在低能区红外波吸收增强。理论计算表明,Cr掺杂纤锌矿GaN可能是一种性能优异的磁光材料。     

氮掺杂对4H—SiC电子结构的影响

采用广义梯度近似的密度泛函理论方法计算了4H—SiC的本征态的电子结构以及4H—SiC材料N掺杂后的电子结构,计算结果表明：与本征态相比,N掺杂后的4H—SiC的导带与价带均向低能端移动,导带移动幅度大于价带,使得掺杂后的禁带宽度小于本征态的禁带宽度：导带底进入N的2s态和2p态,但它们所占比重小,掺杂浓度变化对导带底...     

As、Ga掺杂对Mn4Si7电子结构和光学特性的影响

采用基于密度泛函理论的平面波超软赝势方法研究了四方本征Mn4 Si7、As掺杂及Ga掺杂(同一周期不同主族进行n、p型掺杂)Mn4 Si7模型的电子结构以及光学性质.通过对其能带、态密度及光学性质的分析可以发现,As、Ga掺入后引入了杂质能带,能带曲线向低能级方向移动,导致禁带宽度减小,杂质的引入使得其介电常数、吸收率...     

N-Cu共掺杂金红石相TiO_2光催化剂的第一性原理研究

TiO2是一种广泛应用的无机金属氧化物半导体材料,利用掺入杂质来改善TiO2的光催化和光电转换性能已成为近年来研究的热点。采用密度泛函理论体系下第一性原理的平面波超软赝势方法研究了单N掺杂、单Cu掺杂和N-Cu共掺杂金红石相TiO2的电子结构和光学性质。结果表明:N与Cu共掺杂后,由于N2p电子与Cu3d电子协同作用,在TiO2禁带中产生了新的杂质能级。其中一条处于稳态,另一条处于亚稳态,电子跃迁能有效减小,更有利于光生电子-空穴对有效分离,大大改善了TiO2的光催化性能。N与Cu共掺杂使TiO2的光吸收系数曲线在可见光区发生了比单N掺杂和单Cu掺杂更大的红移,反射率也增大。     

Tc-P共掺杂单层MoS2光电特性的第一性原理计算

采用第一性原理的赝势平面波方法,对比研究了未掺杂和掺杂过渡金属Tc、非金属P及Tc-P共掺杂的单层MoS2的电子结构和光学性质.计算结果表明:掺杂改变了费米面附近的电子结构,使得导带向低能方向偏移,并且带隙由K点转化为Γ点,形成Γ点的直接带隙半导体.掺杂P使带隙值变小,形成p型半导体;掺杂Tc使带隙变宽,形成n型半导体;Tc-P共掺杂,由于p型和n型半导体相互调制,使得单层MoS2转变为性能更优的本征半导体;掺杂使光跃迁强度减小,且向低能方向偏移.     

Se和Cd掺杂GaN电子结构与光学性质的第一性原理研究

基于密度泛函理论的第一性原理,使用GGA+U方法分别计算Se和Cd单掺与共掺杂GaN体系的晶格常数、电子结构及光学性质.结果表明:与本征GaN相比,掺杂后体系的晶格常数发生了改变,禁带宽度减小,吸收光谱均发生红移,表明掺杂使体系的光谱响应范围得到更大拓展.其中,Cd单掺GaN体系的禁带宽度最小,并在费米能级附近有杂质能...     

N掺杂和氧空位对PbTiO3电子结构和导电性的影响研究

用第一性原理计算了P型N掺杂PbTiO3的电子密度差分、能带结构和态密度,讨论了氧空位对N掺杂PbTiO3性能的影响。在PbTiO3中掺杂N杂质后,PbTiO3的价带向高能级发生移动,费米能级进入价带顶部,带隙变窄,N掺杂PbTiO3表现出典型的P型半导体性能。当N掺杂PbTiO3中含有氧空位时,导带发生下移,受主被完全补偿。计算结果与实验数据相吻合。     

A new approach to regulate the photoelectric properties of two-dimensional SiC materials:first-principles calculation on B-N co-doping

This paper describes a new approach to regulate the photoelectric properties of two-dimensional SiC materials. The first-principles pseudo-potential plane wave method is used to calculate the geometric structure, electronic structure and optical properties of two-dimensional (2D) SiC co-doped by the adjacent elements of C-Si (such as B and N). The results show that:after B-N co-doping, the supercell lattices of 2D SiC are observed obviously deformation near the doped atoms. Meanwhile, the band structures of 2D SiC co-doped by B-N become rich. As the impurity level enters the forbidden band, the band gap decreases, and the distribution of density of states near the Fermi level changes accordingly. The calculation of optical properties shows that the ability to absorb electromagnetic waves of 2D SiC has been enhanced obviously in the low energy range after B-N co-doping. The reason is originated from the transition of the 2p state of B and N. At the same time, the static dielectric constant increases and the peak of reflectivity decreases. The above results indicate that the optoelectronic properties of 2D SiC can be modulated by co-doping B-N.     

Influence of tension-twisting deformations and defects on optical and electrical properties of B, N doped carbon nanotube superlattices

As the era of nanoelectronics is dawning, CNT (carbon nanotube), a one-dimensional nano material with outstanding properties and performances, has aroused wide attention. In order to study its optical and electrical properties, this paper has researched the influence of tension-twisting deformation, defects, and mixed type on the electronic structure and optical properties of the armchair carbon nanotube superlattices doped cyclic alternately with B and N by using the first-principle method. Our findings show that if tension-twisting deformation is conducted, then the geometric structure, bond length, binding energy, band gap and optical properties of B, N doped carbon nanotube superlattices with defects and mixed type will be influenced. As the degree of exerted tension-twisting deformation increases, B, N doped carbon nanotube superlattices become less stable, and B, N doped carbon nanotube superlattices with defects are more stable than that with exerted tension-twisting deformations. Proper tension-twisting deformation can adjust the energy gap of the system; defects can only reduce the energy gap, enhancing the system metallicity; while the mixed type of 5% tension, twisting angle of 15° and atomic defects will significantly increase the energy gap of the system. From the perspective of optical properties, doped carbon nanotubes may transform the system from metallicity into semi-conductivity.     

基于密度泛函理论计算的3d过渡金属掺杂CuGaS2电子结构分析

3d transition metals doped CuGaS2 are considered as possible absorbing material candidates for intermediated band thin film solar cells. The electronic structure and optical properties of 3d transition metals doped CuGaS2 are investigated by using density functional theory calculations with the GGA ＋ U method in the present work. The doping with 3d transition metals does not obviously change the crystal structure, band gap, and optical absorption edge of the CuGaS2 host. However, in the case of CuGa1-χTMχS2 （TM = Ti, V, Cr, Fe, and Ni）, there is at least one distinct isolated impurity energy level in the band gap, and the optical absorption is enhanced in the ultraviolet-light region. Therefore, these materials are band thin film solar ceils. The calculated results are very well better explain them. ideal absorber material candidates for intermediated consistent with experimental observations, and could better explain them.     

单晶6H-SiC纳米线的可控掺杂及光学特性

采用有机前驱体制备纳米材料工艺,制备出不同Al掺杂浓度的6H-SiC纳米线(Al/6H-SiC).用HRTEM、EDX、XRD等对纳米线进行了表征,发现随着起始材料中异丙醇铝含量的增加,所制备的纳米线中的Al浓度也在增加,最高可达到1.25%, HRTEM显示晶格间距为0.26 nm和0.25 nm,对应为6H-SiC的(101)和(102)面间距,Si、C原子比为1∶1.拉曼光谱得到这种6H-SiC的声子能量为100 meV,由吸收光谱带边吸收外推计算得到Al/6H-SiC纳米线光学带隙,掺杂浓度越大,吸收边红移越大.     

Insights into enhanced visible-light photocatalytic activity of CeO2 doped with nonmetal impurity from the first principles

The doped cerium dioxide (CeO₂) nanomaterials have attracted intensive attention due to its enhanced photocatalytic activity in the visible light region, but still lacking is the theoretical understanding on the mechanism of this behavior. Herein, the origin of enhanced photocatalytic performance of doped CeO₂ is systematically explored by using the first-principles calculation. The systematic study includes the effects of nonmetal C+N codoping on the electronic structure and optical proprties of CeO₂ in comparison to the effect of individual dopants. The monodoping (B, C) introduces impurity states in the middle of gap. For the N–CeO₂, the impurity levels are near the top of valence band at lower N concentration, while those are separated by more than 1.0 eV in the gap at higher N concentration. Interestingly, C+N codoping shifts up the Fermi level to the bottom of conduction band, and introduces impurity level close to the Fermi level. Moreover, the feasibility of the introduction of N into the CeO₂ crystal structure is found to be enhanced in the presence of C. The reduced band gap and strong absorption induced by impurity levels are responsible for the enhanced photocatalytic activity of doped CeO₂ in the visible region. These findings can rationalize the available experimental results and pave the way for developing CeO₂-based photocatalysts.     

稀土元素(Sm,Tm)掺杂ZnO的电学与光学性质

运用Materials Studio软件中的CASTEP子模块,借助第一性原理平面波超软赝势法,计算分析了稀土元素(Sm,Tm)掺杂ZnO前后的能带结构、态密度以及光学性质变化情况。计算结果表明,掺杂后体系的能带部分更加稠密,出现新的杂质能级,费米能级从价带顶处上移进入导带部分,出现载流子简并现象,形成简并半导体。掺杂体系显示出更强的金属性,呈现n型导电。同时定性分析了体系前后的光学吸收系数与介电函数的变化情况。     

4H-SiC中点缺陷的第一性原理研究

基于密度泛函理论和第一性原理,对4H-SiC晶格中5种点缺陷(VC,VC-C,填隙B,替位B和替位P)的晶格常数、电荷布居、能带等微观电子结构进行了计算,并从缺陷形成能、杂质电离能和载流子浓度等角度分析了这些点缺陷对材料性能的影响.计算结果表明:在这些点缺陷中,C空位的形成能最低,仅为5.929 1 eV,属于比较容易形成的一类点缺陷.同时在能带图中可以看到填隙B的禁带中央附近出现了一条新能带,这条新能带的产生促使填隙B成为5种缺陷中禁带宽度最小的缺陷,有利于SiC半导体器件中载流子的输运.在3种杂质点缺陷中,替位P的电离能最小.掺杂杂质电离能越小,电离程度越深,产生的载流子浓度也越大,这一结论在载流子浓度的计算结果中也得到了验证.     

Sb掺杂ZnO电子结构和光学性质

为了研究ZnO掺Sb后电子结构和光学性质的变化,采用基于密度泛函理论对纯净ZnO和Sb掺杂ZnO两种结构进行第一性原理的计算。计算结果表明：随着Sb的掺入,体系的晶格常数变大,键长增加,体积变大,系统总能增大。能带中价带和导带数目明显变密,费米能级进入导带,体系逐渐呈金属性,带隙明显展宽。在光学性质方面,主吸收峰的左边出现了新的吸收峰,是由导带上的Zn-4s和Sb-5p轨道杂化电子跃迁所致;同时介电函数虚部波峰发生一定程度的升高,实部静态介电常数也明显增大。