共查询到20条相似文献,搜索用时 93 毫秒
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采用基于密度泛函理论(DFT)的第一性原理平面波超软赝势法计算了铅锌矿ZnO{0001}表面的电子结构.分析表面能发现,ZnO-Zn表面的表面能比ZnO-O略大,两者相比,ZnO-Zn表面活性强、不稳定.表面弛豫后,ZnO-Zn和ZnO-O发生表面收缩,ZnO-Zn表面收缩较小.研究发现,由于表层Zn和O原子的强轨道杂化作用导致ZnO-Zn表面显示n型特性;而ZnO-O表面的O-2p悬挂键能级占据价带顶导致ZnO-O表面显示p型特性.计算结果和实验事实基本一致. 相似文献
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利用平面渡赝势密度泛函的方法,结合广义梯度近似,对纤锌矿GaN的光电性质进行了研究.对纤锌矿GaN的能带结构、态密度分布、复介电函数和吸收光谱进行了计算.文中分析了纤锌矿结构GaN晶体可能的跃迁及其对应的吸收光谱.结果显示GaN晶体的光学性质与晶体的电子结构直接相关.计算结果为进一步理解和改进纤锌矿GaN的光电性质提供理论基础. 相似文献
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GaAs第一性原理研究 总被引:2,自引:0,他引:2
为了深入认识GaAs的电子结构和光学性质,计算和分析了GaAs晶体的能带结构、电子态密度、分渡态密度、光学常数,所有计算都是基于密度泛函理论(DFT)框架下的第一性原理平面渡赝势方法.研究证明,其具有广泛的应用领域. 相似文献
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利用基于密度泛函理论的第一性原理,研究了硫(S)掺杂纤锌矿氧化锌(ZnO)的能带结构、态密度和光学性质。结果表明:掺杂后晶格畸变,晶格常数随着掺杂量的增加而增大;S原子掺杂减小了能带间隙,提高了电子跃迁的概率;进一步的光学性质计算发现,S掺杂后吸收谱出现红移,且吸收谱峰值随掺杂量的增加而增大,提高了可见光和紫外光区域的光吸收。 相似文献
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《固体电子学研究与进展》2016,(1)
研究了各向极化对CdS电子结构及光电特性的影响。采用基于密度泛函理论(DFT)的第一性原理超软赝势方法对CdS基态的电子结构和光电特性进行系统地计算,计算得到CdS是带隙宽带为1.943eV的直接带隙半导体材料。价带主要由S 3p态电子贡献,Cd 4p和Cd 4d态电子贡献较少;导带主要由Cd 4d5s和S 3p态电子决定,S 3s态电子贡献较少。在a、b、c三个方向的极化下研究CdS光学特性的各向异性,沿a方向和b方向极化的各个光学参量都完全相同,静态介电常数为7.234,但沿c方向的静态介电常数为6.273。其它光学参量的各向异性变化与介电函数相同,表明CdS晶体光学性质存在各向异性。计算结果为CdS光电特性的研究提供理论依据。 相似文献
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基于密度泛函理论的第一性原理方法,在广义梯度近似下,研究了(5,0)和(5,5)硅纳米管结构和电子性质。计算结果表明:(5,0)管硅原子相邻键长波动范围为0.068 nm,大于(5,5)管的0.006 nm;通过对(5,0)管的分波态密度进行分析发现,其3s电子和2p电子能量分布在-13~3 eV,但2p电子集中分布在能量较高的-6~3 eV,出现了明显的sp3轨道杂化。同时对(5,0)和(5,5)硅纳米管最高占据轨道和最低未占据轨道的能隙进行了分析,发现两种管导电性能与结构的手性相关,锯齿型(5,0)管能带交叠具有明显的金属性,而扶手型(5,5)管能隙为0.151 eV是半导体纳米管。 相似文献
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在密度泛函理论的基础上,采用平面波赝势方法计算了立方GaN(110)表面的原子和电子结构。结构优化表明最表层原子都向体内弛豫,且金属Ga原子弛豫幅度比非金属N原子大,同时各层层间距呈交错分布。表面弛豫后,最表层原子发生键长收缩的弛豫特性,表面Ga原子趋于形成sp2杂化得到的平面型构形,而表面N原子趋于形成p3型锥形结构。另外,理想立方GaN(110)表面在带隙中有两个明显的表面态,经过弛豫后,分别向价带和导带方向移动,并解释了导带底附近的表面态移动的幅度比价带顶附近的表面态大的原因主要由于表面Ga、N原子弛豫幅度不同引起的。此外,弛豫后,表面电荷重新分布,Ga原子周围的部分电子转移到N原子上。 相似文献
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采用Lee-Low-Pines (LLP)变分法研究了纤锌矿GaN/Al0.3Ga0.7N量子阱中自由极化子能量和电子-声子相互作用对自由极化子能量的影响.理论计算中考虑了量子阱中定域声子模(Confined phonon modes)和半空间声子模(Half-space phonon modes)的影响以及电子有效质... 相似文献
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In this article, density functional theory (DFT) based on generalized gradient approximation (GGA) and GGA+U, U is Hubbard term, is used to study the electronic properties of CdS doped with different dopants (Cr, Mn). The calculations are carried out for Mn-doped CdS, Cr-doped CdS, and co-doping of Mn/Cr in CdS simultaneously. It is found that hopping of electrons is possible with Cr:CdS and Mn:Cr:CdS while Mn:CdS does not allow the hopping of electrons. Moreover, double exchange interactions are observed in Cr:CdS and d-d super-exchange interactions are observed in Mn:CdS. Now the problem becomes interesting when one magnetic ion (Cr) supporting double exchange interactions and another ion (Mn) supporting d-d super-exchange interactions are doped simultaneously in the same system (CdS). The co-doped CdS is more stable even at high Curie temperature due to p-d double exchange interactions and d-d super exchange interactions. Furthermore, the Cr-3d and Mn-3d states present in-between the band gap are responsible for inner shell transitions and hence for optical properties. Therefore, the co-doped system is taken into account to enhance its applications in the field of spintronic and magneto-optical devices. 相似文献
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利用第一性原理计算方法密度泛函理论的局域密度近似计算了纤锌矿氮化铝(AlN)、氮化镓(GaN)、氮化铟(InN)及其合金在双轴应变下的电子有效质量。对于GaN和AlN,张应变使电子有效质量增大而压应变使电子有效质量减少,但却使InN电子有效质量在张应变和压应变下都增大。由于三元合金(AlxGa1-xN,InxGa1-xN和AlxIn1-xN)与GaN异质结的新颖特性,同时计算了三元合金在松弛和应变下电子有效质量的变化趋势。受制于GaN基板的平面应力,外延AlxGa1-xN和AlxIn1-xN电子有效质量将减少,而InxGa1-xN电子有效质量增大,且随着In含量变大而更显著。对铟氮化合物应变下电子有效质量异常的机制也做了讨论。 相似文献
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The growth by molecular beam epitaxy of high quality GaAs epilayers on nonmisoriented GaAs(111)B substrates is reported. Growth control of the GaAs epilayers is achieved via in situ, real time measurement of the specular beam intensity of reflection high-energy electron diffraction (RHEED). Static surface phase maps of GaAs(111)B have been generated for a variety of incident As flux and substrate temperature conditions. The dependence of GaAs(111)B to be the optimum starting surface for the latter growth of mirror-smooth epilayers. Regimes of growth conditions are optimized in terms of the static surface phase diagram and the temporal RHEED intensity oscillations. 相似文献
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研究了砷化镓基毫米波MEMS开关的表面工艺方法,包括MEMS开关的工艺流程中的牺牲层技术、结构层技术、触点技术、薄膜电阻技术。重点阐述了以光敏聚酰亚胺作牺牲层和以电镀金作结构层的工艺制作方法。形成了砷化镓RF MEMS开关表面工艺流程,制作出了RF MEMS开关样品。开关驱动电压为60 V,35 GHz时的插入损耗<0.2 dB,隔离度>18 dB。 相似文献
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Anatase (101) Reconstructed Surface with Novel Functionalities: Desired Bandgap for Visible Light Absorption and High Chemical Reactivity 下载免费PDF全文
Rulong Zhou Bingyan Qu Dongdong Li Xiaorui Sun Xiao Cheng Zeng 《Advanced functional materials》2018,28(8)
Unreconstructed surfaces of anatase TiO2 are known to have two main limitations for their application as photocatalysts, namely, low efficiency for sun‐light absorption due to the wide bandgap, and low chemical reactivity. Strategies to overcoming the two limitations and to enhancing TiO2's photocatalytic efficiency have been highly sought. To this end, a global search of anatase reconstructed surfaces is performed based on the evolutionary method. It is found that the newly predicted anatase (101) reconstructed surface possesses a desired bandgap whose value is within the energy domain of visible light as well as notably high chemical reactivity compared to the unreconstructed anatase (101) surface. In particular, it is predicted that under Ti‐richness condition, the anatase (101) reconstructed surface is energetically very stable. The anatase (101) reconstructed surface exhibits similar topmost surface structure as the unreconstructed anatase (101) surface but different subsurface structure. Not only the fivefold coordinated Ti atoms (Ti5c) in the topmost surface layer but also the sixfold coordinated Ti atoms in the subsurface layer contribute to the desirable gap states. The high chemical reactivity of anatase (101) reconstructed surface can be attributed to the extra electrons drawn by the surface Ti5c atoms and subsurface Ti6c atoms. 相似文献
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Shadi A. Dayeh Darija Susac Karen L. Kavanagh Edward T. Yu Deli Wang 《Advanced functional materials》2009,19(13):2102-2108
Here, direct correlation between the microstructure of InAs nanowires (NWs) and their electronic transport behavior at room temperature is reported. Pure zinc blende (ZB) InAs NWs grown on SiO2/Si substrates are characterized by a rotational twin along their growth‐direction axis while wurtzite (WZ) InAs NWs grown on InAs (111)B substrates have numerous stacking faults perpendicular to their growth‐direction axis with small ZB segments. In transport measurements on back‐gate field‐effect transistors (FETs) fabricated from both types of NWs, significantly distinct subthreshold characteristics are observed (Ion/Ioff ~ 2 for ZB NWs and ~104 for WZ NWs) despite only a slight difference in their transport coefficients. This difference is attributed to spontaneous polarization charges at the WZ/ZB interfaces, which suppress carrier accumulation at the NW surface, thus enabling full depletion of the WZ NW FET channel. 2D Silvaco‐Atlas simulations are used for ZB and WZ channels to analyze subthreshold current flow, and it is found that a polarization charge density of ≥1013 cm?2 leads to good agreement with experimentally observed subthreshold characteristics for a WZ InAs NW given surface‐state densities in the 5 × 1011–5 × 1012 cm?2 range. 相似文献