氧化锌纳米线的稳定性和电子性质

运用第一性原理方法研究了四种尺寸的ZnO纳米线的结构稳定性和电子性质.结果表明,纳米线的稳定性随着尺寸的增大而增大.所有ZnS纳米线显示了直接带隙半导体特性.由于量子尺寸效应,纳米线的带隙比纤锌矿体材料的带隙大,并且随着纳米线直径的增大而减小.     

Cu掺杂ZnS纳米线结构和磁性质

本文采用第一性原理密度泛函理论系统地研究了Cu原子掺杂ZnS纳米线的结构、电子性质和磁性质.所有掺杂纳米线的形成能比纯纳米线的形成能低,说明掺杂过程是放热的.并且Cu原子趋于替代纳米线的表面的Zn原子.电子结构显示Cu掺杂纳米线是半金属铁磁半导体材料,在自旋电子学方面有重要应用.     

Reducing Zn diffusion in single axial junction InP nanowire solar cells for improved performance

In this work axial n-i-p junction InP nanowires were grown by selective-area metal organic vapor phase epitaxy (SA-MOVPE) technique with the growth sequence starting from n-segment. The optical properties and carrier lifetimes of the n-, i- and p-type segments were studied and compared using time-resolved photoluminescence (PL) and cathodoluminescence (CL) measurements. We demonstrate for the first time that CL is capable of resolving the electrical profile of the nanowires, namely the varied lengths of the n-, i- and p-segments, providing a simple and effective approach for nanowire growth calibration and optimization. The CL result was further confirmed by electron beam induced current (EBIC) and photocurrent mapping measurements performed from the fabricated single nanowire solar cell devices. It is revealed that despite a non-optimized device structure (very long n-region and short i-region), the n-i-p nanowire solar cells show improved power conversion efficiency (PCE) than the previously reported p-i-n (growth starts with p-segment) single nanowire solar cells due to reduced p-type dopant (Zn) diffusion during the growth of n-i-p solar cell structure.     

C掺杂ZnS纳米线电子性质和磁性质

运用第一性原理方法研究了C掺杂ZnS纳米线的电子性质和磁性质.研究发现C原子趋于替代纳米线表面的S原子.所有掺杂纳米线显示了半导体特性.纳米线的总磁矩主要来源于C原子2p轨道的贡献.由于杂化,相邻的Zn原子和S原子也产生了少量自旋.在超原胞内,C、Zn和S原子磁矩平行排列,表明它们之间是铁磁耦合.铁磁态和反铁磁态的能量差达到了121meV,表明C掺杂ZnS纳米线可能存在室温铁磁性,这在自旋电子学领域有很大应用前景.     

Controlling charges distribution at the surface of a single GaN nanowire by in-situ strain

Effect of the strain on the charge distribution at the surface of a GaN semiconductor nanowire (NW) has been investigated inside transmission electron microscope (TEM) by in-situ off-axis electron holography. The outer and inner surfaces of the NW bent axially under compression of two Au electrodes were differently strained, resulting in difference of their Fermi levels. Consequently, the free electrons flow from the high Fermi level to the low level until the two Fermi levels aligned in a line. The potential distributions induced by charge redistribution in the two vacuum sides of the bent NW were examined respectively, and the opposite nature of the bounded charges on the outer and inner surfaces of the bent NW was identified. The results provide experimental evidence that the charge distribution at the surfaces of a single GaN NW can be controlled by different strains created along the NW.     

过渡金属掺杂ZnO纳米线结构、电子性质和磁性质

本文采用密度泛函理论系统地研究了过渡金属原子Co和Ni单掺杂和双掺杂ZnO纳米线的结构、电子性质和磁性质.所有掺杂纳米线的束缚能都为负值,表明掺杂过程是放热的. Co原子趋于占据纳米线中间位置,而Ni原子趋于占据纳米线表面位置.所有掺杂纳米线能隙都小于纯纳米线能隙,并显示出直接带隙半导体特性.纳米线的总磁矩主要来源于磁性原子的贡献. Co掺杂纳米线出现了铁磁和反铁磁两种耦合状态;而Ni掺杂纳米线出现了铁磁、反铁磁和顺磁三种耦合状态.     

Fe掺杂ZnO纳米线电子性质和磁性质

本文采用第一性原理密度泛函理论系统地研究了Fe原子单掺杂和双掺杂ZnO纳米线的电子性质和磁性质.所有掺杂纳米线的形成能都比纯纳米线的形成能低,说明掺杂过程是放热的.计算结果显示Fe原子趋于占据纳米线表面位置.纳米线的总磁矩主要来源于Fe原子3d轨道的贡献.由于杂化,相邻的O原子也产生了少量自旋.在超原胞内,Fe、O原子磁矩平行排列,表明它们之间是铁磁耦合.表面掺杂纳米线显示出半导体特性,而中间掺杂纳米线显示出半金属性,在自旋电子学领域有广泛应用.     

Fabrication of flexible α-MnO_2 nanowire membranes with superior mechanical strength

The Assembly of one-dimensional （1D） nano- structures such as nanowires/nanorods/nanotubes into two- dimensional （2D） macrostructured films is attracting considerable research interest because of their unique properties and wide applications. In this study, flexible membranes were successfully fabricated using α-MnO2 nanowires synthesized through a hydrothermal method. The effects of thickness and post-annealing temperature on the mechanical properties of the membranes were investigated in detail. Nano-indentation measurements showed that the modulus of the as-prepared 11.75 μm-thick membrane reached 5.765 GPa, and the modulus increased with the increasing post-annealing temperature. Thus, the fabricated membranes with superior mechanical strength can have potential applications such as in photocatalysis, filtering, and supporting substrates.     

Facile synthesis of polypyrrole nanowires for high-performance supercapacitor electrode materials

Polypyrrole nanowires are facile synthesized under a mild condition with FeCl_3 as an oxidant. Polypyrrole nanowires with the width of 120 nm form many nanogaps or pores due to the intertwined nanostructures. More importantly, PPy nanowires were further applied for supercapacitor electrode materials.After electrochemical testing, it was observed that the PPy nanowire based electrode showed a large specific capacitance(420 Fg~(-1), 1.5 Ag~(-1)) and good rate capability(272 Fg~(-1), 18.0 Ag~(-1)), which is larger than that of most of published results. The as-prepared electrode can work well even after 8000 cycles at 1.5 Ag~(-1).