共查询到19条相似文献,搜索用时 193 毫秒
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在计入应力的紧束缚框架之下计算了单原子层应变超晶格(Si)_1/(Si_1-xGo_x)_1的电子结构.对应于不同应变条件,得出能隙随组分的变化,并结合能带边不连续的变动加以考察.超晶格取Si(或Ge)晶格常数后能隙随组分的非单调变化源自合金受相同应力后能隙的类似特点.超晶格能带及态密度均呈现类Si的闪锌矿结构对称性.在虚晶近似得出的能隙和电子状态密度的基础上,利用相干势近似作了进一步的修正. 相似文献
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徐至中 《固体电子学研究与进展》1993,13(4):287-291
采用紧束缚的重整化方法计算了超晶格(Al_xGa_1 xAs)_m/(GaAs)_m(110)的电子能带结构(1≤m≤10)。讨论了电子能带结构随超晶格层厚m及合金组分x的变化情况。计算结果表明,对于不同的合金组分x,超晶格可以处在三个不同区域:A区,直接能隙结构,Ⅰ-型超晶格;B区,间接能隙结构,Ⅰ-型超晶格;C区,间接能隙结构,Ⅱ—型超晶格。 相似文献
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本文研究了GaInPAs/InP晶格匹配超晶格材料<110>方向的电子结构,对薄层超晶格和与之具有相同化学组份的混晶的色散关系作了比较。研究了带边状态密度在超晶格每一层的分布情况,计算了GaInPAs/InP晶格匹配超晶格的能隙随厚度、组份的变化趋势。研究结果表明:薄层超晶格与具有相同化学组份的混晶的电子结构基本相同,能隙边状态密度偏重于分布在超晶格的GaInPAs原子层内。 相似文献
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为了研究单壁碳纳米管的电子能带特性及其态密度,本文采用紧束缚法和态密度函数,对无限长碳纳米管进行了理论计算和模拟。结果表明:碳纳米管的电子能带结构与其几何结构密切相关,一般认为扶手型管呈现出金属性;而锯齿管则不同,当n=3k(k为整数)时,其能级存在一个较小的禁带宽度,具有半金属性质;而其它锯齿型管均存在较大的禁带宽度,且禁带宽度随管径的增大而减小,具有半导体性质,这为碳纳米管的电子结构的研究提供了必要且有价值的理论依据。 相似文献
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徐至中 《固体电子学研究与进展》1992,(1)
采用紧束缚的重整化方法研究了(Al_xGa_(1-x)As)_m/(GaAs)_m(001)超晶格的电子能带结构与合金组分x及层厚间的变化关系。给出了临界组分x_o与层厚m间的变化关系图。并以二次函数形式给出了直接能隙和间接能隙与合金组分x间的变化关系。最后,也用Kronig—Penney模型对超晶格的电子能带结构进行了计算,并与紧束缚的计算结果进行了比较。 相似文献
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本文使用紧束缚法研究了GaAs-GaP超晶格的能带结构和电子的有关性质.久期方程的矩阵元中包括了一直到次近邻的原子轨道间的相互作用积分.本文计算了超晶格(GaAs)1-(GaP)_1布里渊区中三条主要对称线上的能带;计算了超晶格(GaAs)m-(GaP)n在Γ点、X点和M点的能带值,这里m+n≤10;讨论了m=n时禁带宽度随周期长度的变化、周期长度不变时组分变化对禁带宽度的影响以及在几个典型的单电子状态中电子处于各个原子上的几率. 相似文献
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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. 相似文献
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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. 相似文献
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Onnik Yaglioglu Anyuan Cao A. John Hart Rod Martens A. H. Slocum 《Advanced functional materials》2012,22(23):5028-5037
Vertically aligned carbon nanotube (CNT) forests may be used as miniature springs, compliant thermal interfaces, and shock absorbers, and for these and other applications it is vital to understand how to engineer their mechanical properties. Herein is investigated how the diameter and packing density within CNT forests govern their deformation behavior, structural stiffness, and elastic energy absorption properties. The mechanical behavior of low‐density CNT forests grown by fixed catalyst CVD methods and high‐density CNT forests grown by a floating catalyst CVD method are studied by in situ SEM compression testing and tribometer measurements of force‐displacement relationships. Low‐density and small‐diameter CNT columns (fixed catalyst) exhibit large plastic deformation and can be pre‐deformed to act as springs within a specified elastic range, whereas high‐density and large‐diameter CNT columns (floating catalyst) exhibit significant elastic recovery after deformation. In this work the energy absorption capacity of CNT forests is tuned over three orders of magnitude and it is shown that CNT forest density can be tuned over a range of conventional foam materials, but corresponding stiffness is ~10× higher. It is proposed that the elastic behavior of CNT forests is analogous to open‐cell foams and a simple model is presented. It is also shown that this model can be useful as a first‐order design tool to establish design guidelines for the mechanical properties of CNT forests and selection of the appropriate synthesis method. 相似文献
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Using the first-principles method based on the density functional theory, the formation energy, electronic structures of S-Na co-doping in ZnO were calculated. The calculated results show that NaZn-SO have smaller formation energy than Nain-SO in energy ranges from -3.10 to 0 eV of μO, indicating that it opens up a new opportunity for growth the p-type ZnO. The band structure shows that the NaZn system is a p-type direct-band-gap semiconductor material and the calculated band gap (0.84 eV) is larger than pure ZnO (0.74 eV). The NaZn-SO system is also a p-type semiconductor material with a direct band gap (0.80 eV). The influence of S-Na co-doping in ZnO on p-type conductivity is also discussed. The effective masses of NaZn-SO are larger than effective masses of NaZn and the NaZn-SO have more hole carriers than NaZn, meaning the hole in the NaZn-SO system may have a better carrier transfer character. So we inferred that NaZn-SO should be a candidate of p-type conduction. 相似文献
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Ke Wang Shu Luo Yang Wu Xingfeng He Fei Zhao Jiaping Wang Kaili Jiang Shoushan Fan 《Advanced functional materials》2013,23(7):846-853
Carbon nanotube (CNT) current collectors with excellent flexibility, extremely low density (0.04 mg cm?2), and tunable thickness are fabricated by cross‐stacking continuous CNT films drawn from super‐aligned CNT arrays. Compared with metal current collectors, better wetting, stronger adhesion, greater mechanical durability, and lower contact resistance are demonstrated at the electrode/CNT interface. Electrodes with CNT current collectors show improvements in cycling stability, rate capability, and gravimetric energy density over those with metal current collectors. These results suggest that CNT films can function as a promising type of current collector for lightweight and flexible lithium ion batteries with high energy density. 相似文献
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碳纳米管具有独特的结构和卓越的电学、热学、力学等性能,有望在微纳电子、微纳机电系统、传感器、新能源、光学等诸多领域获得具有深远影响的应用。碳纳米管的组装是其获得广泛应用的重要前提,基于介电电泳的组装和过程控制技术近年来得到了迅速发展。这些技术包括回路中串联自限制性电阻,间隙电信号实时监测和反馈控制,三维结构的组装和包覆,引入不同形状浮动电极等。对碳纳米管介电电泳组装及各种新技术做了系统介绍,并对各种方法的优缺点进行了对比与总结,为探索稳定、高效的碳纳米管自动组装方法提供帮助。 相似文献
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Recently, a new hybrid supercapacitor, integrating both the advantages of supercapacitors and lithium‐ion batteries, was proposed and rapidly turned into state‐of‐the‐art energy‐storage devices with a high energy density, fast power capability, and a long cycle life. In this paper, a new hybrid supercapacitor is fabricated by making use of the benefits of 1D nanomaterials consisting of a carbon nanotube (CNT) cathode and a TiO2–B nanowire (TNW) anode, and the preliminary results for such an energy‐storage device operating over a wide voltage range (0–2.8 V) are presented. The CNT–TNW supercapacitor is compared to a CNT–CNT supercapacitor, and discussed with regards to available energy densities, power capabilities, voltage profiles, and cycle life. On the basis of the total weight of both active materials, the CNT–TNW supercapacitor delivers an energy density of 12.5 W h kg–1 at a rate of 10 C, double the value of the CNT–CNT supercapacitor, while maintaining desirable cycling stability. The combination of a CNT cathode and a TNW anode in a non‐aqueous electrolyte is proven to be suitable for high‐performance hybrid supercapacitor applications; this can reasonably be assigned to the interesting synergistic effects of the two nanomaterials. It is hoped that the results presented in this study might renew interest in the design of nanomaterials that are applicable not only to hybrid supercapacitors, but also to energy conversion and storage applications of the future. 相似文献
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The carbon nanotube (CNT) bundle is a promising candidate for next-generation interconnect/via applications. A realistic CNT bundle is a mixture of single-wall and multi-wall CNTs and its performance analysis needs to consider both kinds of CNTs. The inductances of the mixed CNT bundles are estimated, which are in agreement with the recent experimental results. Impacts of different parameters such as tube density, tube distribution, metallic tube ratio and bundle dimensions are discussed, providing an important guideline to design and fabricate a CNT bundle with a desirable inductance performance. 相似文献
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Efficiency Enhancement of Single‐Walled Carbon Nanotube‐Silicon Heterojunction Solar Cells Using Microwave‐Exfoliated Few‐Layer Black Phosphorus
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Munkhjargal Bat‐Erdene Munkhbayar Batmunkh Sherif Abdulkader Tawfik Marco Fronzi Michael J. Ford Cameron J. Shearer LePing Yu Mahnaz Dadkhah Jason R. Gascooke Christopher T. Gibson Joseph G. Shapter 《Advanced functional materials》2017,27(48)
Carbon nanotube‐silicon (CNT‐Si)‐based heterojunction solar cells (HJSCs) are a promising photovoltaic (PV) system. Herein, few‐layer black phosphorus (FL‐BP) sheets are produced in N‐methyl‐2‐pyrrolidone (NMP) using microwave‐assisted liquid‐phase exfoliation and introduced into the CNTs‐Si‐based HJSCs for the first time. The NMP‐based FL‐BP sheets remain stable after mixing with aqueous CNT dispersion for device fabrication. Due to their unique 2D structure and p‐type dominated conduction, the FL‐BP/NMP incorporated CNT‐Si devices show an impressive improvement in the power conversion efficiency from 7.52% (control CNT‐Si cell) to 9.37%. Our density‐functional theory calculation reveals that lowest unoccupied molecular orbital (LUMO) of FL‐BP is higher in energy than that of single‐walled CNT. Therefore, we observed a reduction in the orbitals localized on FL‐BP upon highest occupied molecular orbital to LUMO transition, which corresponds to an improved charge transport. This study opens a new avenue in utilizing 2D phosphorene nanosheets for next‐generation PVs. 相似文献