共查询到20条相似文献,搜索用时 0 毫秒
1.
Gerben L. Tuin Magnus T. Borgström Johanna Trägårdh Martin Ek L. Reine Wallenberg Lars Samuelson Mats-Erik Pistol 《Nano Research》2011,4(2):159-163
We have investigated individual bulk-like wires of wurtzite InP using photoluminescence, photoluminescence excitation spectroscopy
and transmission electron microscopy. Using two different methods we find that the top of the valence band is split, as expected
theoretically. This splitting of the valence band is peculiar to wurtzite InP and does not occur in zinc blende InP. We find
the energy difference between the two bands to be 40 meV. 相似文献
2.
3.
The electronic properties of zinc-blende, wurtzite, and rotationally twinned InP nanowires were studied using first-principles calculations. The results show that all the simulated nanowires exhibit a semiconducting character, and the band gap decreases with increasing the nanowire size. The band gap difference between the zinc-blende, wurtzite, and twinned InP nanowires and bulk InP can be described by ΔE(g)(wire) = 0.88/D(1.23), ΔE(g)(wire) = 0.79/D(1.22) and ΔE(g)(twin) = 1.3/D(1.19), respectively, where D is the diameter of the nanowires. The valence band maximum (VBM) and conduction band minimum (CBM) originate mainly from the p-orbitals of the P atoms and s-orbitals of the In atoms at the core regions of the nanowires, respectively. The hexagonal (2H) stacking inside the cubic (3C) stacking has no effect on the electronic properties of thin InP nanowires. 相似文献
4.
考虑量子结构的各向异性,基于双参数变分方法理论分析了准一维GaN-基纳米线结构的类氢杂质态光学特性.数值结果表明,GaN纳米线体系的杂质结合能达到190 meV,是相同尺寸GaAs-基量子线中相应值的2.5倍.这一结果与最近GaN纳米线杂质态的实验测量相当符合.计算发现,采用双参数变分波函数描述准一维GaN纳米线体系各... 相似文献
5.
Kilian Mergenthaler Azhar Iqbal Jesper Wallentin Sebastian Lehmann Magnus T. Borgström Lars Samuelson Arkady Yartsev Mats-Erik Pistol 《Nano Research》2013,6(10):752-757
Realizing photon upconversion in nanostructures is important for many next- generation applications such as biological labelling, infrared detectors and solar cells. In particular nanowires are attractive for optoelectronics because they can easily be electrically contacted. Here we demonstrate photon upconversion with a large energy shift in highly n-doped InP nanowires. Crucially, the mechanism responsible for the upconversion in our system does not rely on multi-photon absorption via intermediate states, thus eliminating the need for high photon fluxes to achieve upconversion. The demonstrated upconversion paves the way for utilizing nanowires--with their inherent flexibility such as electrical contactability and the ability to position individual nanowires--for photon upconversion devices also at low photon fluxes, possibly down to the single photon level in optimised structures. 相似文献
6.
We report a density functional study of the electronic properties and hyperfine structure of substitutional selenium in silicon nanowires using plane-wave pseudopotential techniques. We simulated hydrogen passivated [001] oriented nanowires with a diameter up to 2 nm, analyzing the effect of quantum confinement on the defect formation energy and on the hyperfine parameters as a function of the diameter and of the defect position. We show that substitutional Se in silicon has favorable configurations for positions near the surface with possible formation of chalcogen-hydrogen complexes. We also show that hyperfine interactions increase at small diameters, as long as the nanowire is large enough to prevent surface distortion which modifies the symmetry of the donor wave function. Moreover, surface effects lead to strong differences in the hyperfine parameters depending on the Se location inside the nanowire, allowing the identification of an impurity site on the basis of electron paramagnetic resonance spectra. 相似文献
7.
Valence and conduction band edge charge densities for direct band gap InP and indirect band gap semiconductors GaP are calculated for different values of the lattice constant. These variations affect the bonding properties of these semiconductors and the effect of interstitial impurities. 相似文献
8.
Electrical conductivity is reported for the 10 – 500 K range in microcrystalline La-doped SrTiO3 samples. These had been reduced by equilibration at 1325 K in a low oxygen partial pressure (PO2 from 10?16 to 10?20 atm), and quenched. The data support a Sr vacancy defect model, whereby excess oxygen compensates La donors when equilibration is for PO2 > 10?18 atm prior to quenching. Stronger reduction prior to quenching leads to Ti site controlled valency conduction. The fall-off of conductivity upon cooling below 300 K does not fit an Arrhenius form for any of the quenched samples, indicating a combination of carrier density and carrier mobility considerations. The conductivity for 300 K, and also for much lower temperatures, shows a strong maximum near atomic, or some 3 × 1019 cm?3. It is expected that low-mobility behavior for stronger doping results from merging of conduction and impurity bands. Thermpower data also suggests impurity banding. 相似文献
9.
This study reports that the visible-blind ultraviolet (UV) photodetecting properties of ZnO nanowire based photodetectors were remarkably improved by introducing ultrathin insulating MgO layers between the ZnO nanowires and Si substrates. All layers were grown without pause by metal organic chemical vapor deposition and the density and vertical arrangement of the ZnO nanowires were strongly dependent on the thickness of the MgO layers. The sample in which an MgO layer with a thickness of 8 nm was inserted had high density nanowires with a vertical alignment and showed dramatically improved UV photosensing performance (photo-to-dark current ratio = 1344.5 and recovery time = 350 ms). The photoresponse spectrum revealed good visible-blind UV detectivity with a sharp cut off at 378 nm and a high UV/visible rejection ratio. A detailed discussion regarding the developed UV photosensing mechanism from the introduction of the i-MgO layers and highly dense nanowires in the n-ZnO nanowires/i-MgO/n-Si substrates structure is presented in this work. 相似文献
10.
Storm K Nylund G Borgström M Wallentin J Fasth C Thelander C Samuelson L 《Nano letters》2011,11(3):1127-1130
As downscaling of semiconductor devices continues, one or a few randomly placed dopants may dominate the characteristics. Furthermore, due to the large surface-to-volume ratio of one-dimensional devices, the position of the Fermi level is often determined primarily by surface pinning, regardless of doping level. In this work, we investigate the possibility of tuning the Fermi level dynamically with wrap-around gates, instead of statically setting it using the impurity concentration. This is done using Ω-gated metal-oxide-semiconductor field-effect transistors with HfO(2)-capped InP nanowires as channel material. It is found that induced n-type devices exhibit an optimal inverse subthreshold slope of 68 mV/decade. By adjusting the growth and process parameters, it is possible to produce ambipolar devices, in which the Fermi level can be tuned across the entire band gap, making it possible to induce both n-type and p-type conduction. 相似文献
11.
Wu Shiyao Peng Kai Battiato Sergio Zannier Valentina Bertoni Andrea Goldoni Guido Xie Xin Yang Jingnan Xiao Shan Qian Chenjiang Song Feilong Sun Sibai Dang Jianchen Yu Yang Beltram Fabio Sorba Lucia Li Ang Li Bei-bei Rossella Francesco Xu Xiulai 《Nano Research》2019,12(11):2842-2848
Nano Research - Crystal-phase low-dimensional structures offer great potential for the implementation of photonic devices of interest for quantum information processing. In this context, unveiling... 相似文献
12.
Skinner RJ Lee JS Hu YF Jiang DT Aich P Wettig S Maley J Sammynaiken R 《Journal of nanoscience and nanotechnology》2005,5(9):1557-1560
M-DNA is an engineered duplex DNA that is synthesized from high doping of transition metal ions (Ni2+, Co2+ and Zn2+) into B-DNA at high pH. X-ray Absorption Near Edge Structure (XANES) of the Nitrogen K-edge shows remarkable differences between the doped and undoped DNA. A metal ion induced conduction band in the M-DNA is used to explain the XANES results. 相似文献
13.
It is hypothesized that a highly ordered, relatively defect-free dilute magnetic semiconductor system should act as a weak ferromagnet. Transition-metal-doped ZnO nanowires, being single crystalline, single domain, and single phase, are used here as a model system for probing the local dopant coordination environments using X-ray absorption spectroscopy and diffraction. Our X-ray spectroscopic data clearly show that the dopant resides in a uniform environment, and that the doping does not induce a large degree of disorder in the nanowires. This homogeneous nature of the doping inside the oxide matrix correlates well with observed weakly ferromagnetic behavior of the nanowires. 相似文献
14.
N. S. Mera L. Elliott D. B. Ingham D. Lesnic 《International journal for numerical methods in engineering》2002,53(10):2413-2427
In many heat conduction problems, boundaries with sharp corners or abrupt changes in the boundary conditions give rise to singularities of various types which tend to slow down the rate of convergence with decreasing mesh size of any standard numerical method used for obtaining the solution. In this paper, it is shown how this difficulty may be overcome in the case of an anisotropic medium by a modified boundary element method. The standard boundary element method is modified to take account of the form of the singularity, without appreciably increasing the amount of computation involved. Two test examples, the first with a singularity caused by an abrupt change in a boundary condition and the second with a singularity caused by a sharp re‐entrant corner, are investigated and numerical results are presented. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
15.
D. M. Trujillo H. R. Busby 《International journal for numerical methods in engineering》1982,18(1):99-109
Two highly accurate implicit Padé approximations to the transient heat conduction equation are investigated using the conjugate gradient method to solve, for the temperatures. The accuracy and stability of the approximations are discussed and numerical examples are presented showing the relative performance. Comparisons with the Crank-Nicolson method are also presented. 相似文献
16.
J. Cho C.-M. Wang H. M. Chan J. M. Rickman M. P. Harmer 《Journal of Materials Science》2002,37(1):59-64
Oversized rare-earth dopant ions such as Y3+, Nd3+, and La3+ segregate to grain boundaries and reduce the tensile creep rate of -Al2O3 by 2-3 orders of magnitude. It has been speculated that these dopant ions can modify the grain boundary structure in alumina by promoting the formation of special grain boundaries. If this were indeed the case, it would provide a possible explanation for the aforementioned creep rate retardation. In order to test this hypothesis, electron backscatter diffraction (EBSD) has been used to assess both the proportion of coincidence-site lattice boundaries, and the grain boundary misorientation distribution, in aluminas doped with various ions (Zr, Y, Nd, La, Nd/Zr). The results show that the grain boundary structure in alumina is not significantly altered by the addition of the above dopants, implying that the change in grain boundary chemistry is primarily responsible for the observed creep behavior. 相似文献
17.
An empirical potential for the calculation of the atomic structure of extended defects in wurtzite GaN 总被引:1,自引:0,他引:1
N. Aïchoune V. Potin P. Ruterana A. Hairie G. Nouet E. Paumier 《Computational Materials Science》2000,17(2-4):380-383
The Stillinger–Weber potential has been parametrized for GaN with bond-type dependent parameters to allow efficient atomic simulations of large systems containing wrong, dangling and extra bonds. The input data for the fit are the experimental elastic constants of wurtzite structure and wrong bond energies deduced from ab initio calculation. The potential in then applied to zincblende structure and to planar defects. The predicted values are compared to experimental observation and previous computations. 相似文献
18.
The optical and electrical properties of zinc selenide crystals doped with elements of group V from the vapor phase are described. The possibility is demonstrated of obtaining p-type layers with an intense blue luminescence line. 相似文献
19.
Carsten Pfüller Oliver Brandt Timur Flissikowski Caroline Chèze Lutz Geelhaar Holger T. Grahn Henning Riechert 《Nano Research》2010,3(12):881-888
Single, free-standing GaN nanowires grown by plasma-assisted molecular-beam epitaxy have been investigated with low temperature
micro-photoluminescence. The quantitative analysis of the luminescence spectra of around 100 nanowires revealed that each
nanowire exhibits its own individual spectrum. A significant fraction of nanowires exclusively emits at energies corresponding
to either surface-donor-bound or free excitons, demonstrating that optical properties of individual nanowires are determined
by a few impurity atoms alone. The number of impurities per nanowire and their location within the nanowires varies according
to Poissonian statistics. 相似文献
20.
弹性超材料可以实现减振降噪、波导、隐身等弹性波操控功能,具有广阔的工程应用前景。本文引入固液相变材料作为散射体对比研究了散射体固液两种形态下的带隙特性和隔振性能,利用数值方法计算单胞的能带结构和动态有效质量,研究了影响超材料带隙特性的因素,并通过试验验证了两种形态超材料的隔振性能。结果表明:液态散射体超材料可产生局域共振带隙实现低频段隔振,固态散射体超材料可产生 Bragg 带隙实现宽频段隔振;同时,改变外界条件对两种设计形态的带隙均起到很好的调控作用。由此,超材料散射体两种设计状态的转变实现了带隙类型的转变和隔振频段的调节,可为适应热环境下的相变散射体超材料构型设计和隔振特性调控提供参考依据。 相似文献