Se，Te纳米线系统的结构稳定性研究

采用第一性原理计算及经验方法研究了Se，Te纳米线的结构稳定性. Se与Te的晶体是由三角Se，Te原子链构成并且链间相互作用相对较弱. 小直径的纳米线(<30?)进行了第一性原理计算； 同时对于大直径的纳米线，采用了一种只考虑了链间相互作用的经验方法. 六边形截面的构型比其他各种结构都要稳定，虽然在原子链数目的限制下无法保证其为正六边形. 该结论与被广泛接受的Se，Te纳米线的六边形稳定结构相一致. 关键词： 第一性原理 纳米线 硒 碲     

Pt-Ag合金纳米线热力学性质的分子动力学模拟研究

基于EAM原子嵌入势,采用分子动力学方法,对临界尺寸下的Pt0.95Ag0.05合金纳米线多边形结构的熔化行为进行了计算模拟.结果表明:径向尺寸对Pt0.95Ag0.05合金纳米线的熔点影响较为显著,而长度对其影响较小;引入林德曼因子得到的熔点和用势能-温度变化曲线找到的熔点基本一致;合金纳米线的染色原子由外向内运动;综合分析发现Pt0.95Ag0.05合金纳米线以先外后内的模式进行熔化.     

Pt-Ag合金纳米线热力学性质的分子动力学模拟研究

基于原子嵌入势(EAM),采用分子动力学方法,对临界尺寸下的Pt_(0.95)Ag_(0.05)合金纳米线多边形结构的熔化行为进行了计算模拟.结果表明:径向尺寸对Pt_(0.95)Ag_(0.05)合金纳米线的熔点影响较为显著,而长度对其影响较小;引入林德曼因子得到的熔点和用势能-温度变化曲线找到的熔点基本一致;合金纳米线的染色原子由外向内运动;综合分析发现Pt_(0.95)Ag_(0.05)合金纳米线以先外后内的模式进行熔化.     

火焰原子吸收法测定高含量硒中碲

硒化合物在电子、玻璃等工业部门用途广泛，对高含量硒中碲的测定通常是用分光光度比色法或极谱法。本文详细研究了火焰原子吸收光谱法在这领域中的应用。使用本方法不必从硒化物试样中分离碲。在０．６—１．２ｍｏｌ／ＬＨＣｌ介质中测定碲时，检出限０．０８μｇ／ｍＬ，特证浓度０．１５μｇ／ｍＬ１％，线性范围１—２０μｇ／ｍＬ。相关系数０．９９９８。     

掺碲硒化镓晶体的光学性能

采用水平区熔法生长了碲（Te）掺杂浓度（质量百分比）分别为0.05%,0.1%,0.5%,1%,2%的硒化镓（GaSe）晶体,并分别对掺杂浓度为0.01%,0.07%,0.38%,0.67%,2.07%的GaSe∶Te晶体的光学性能进行了表征。首次研究了GaSe∶Te晶体中刚性层声子模式的转换。吸收光谱测试结果表明：当Te掺杂浓度小于0.38%时,振动中心位于0.59 THz附近的E＇（2）刚性模式吸收峰强度可达最大值,这一过程与GaSe∶Te晶体光学性能的提高密切相关。但Te掺杂浓度的进一步提高会导致E＇（2）刚性模式吸收峰强度逐渐减弱,当Te掺杂浓度为1%时,E＇（2）刚性模式吸收峰基本消失。这两个过程与GaSe∶Te晶体光学质量的下降密切相关。因此,E＇（2）刚性模式吸收强度达到最高时对应的掺杂浓度即是GaSe∶Te晶体中Te的最佳掺杂浓度,光整流产生太赫兹过程证实了此结论的正确性。     

FeCo二元合金纳米线阵列的磁化反转

利用交流电化学沉积方法在氧化铝模板中制备了一维结构的Fe_xCo_1-x(0 ≤ x ≤ 0.51)二元合金纳米线阵列.X射线衍射结果显示,单质Co纳米线为(100)择优取向的hcp结构,FeCo合金纳米线则呈现(110)择优取向的bcc结构,而且衍射峰随纳米线中Fe含量的增加向低角度偏移.室温磁性测量结果显示, FeCo合金纳米线具有较好的磁特性.与Co纳米线相比,Fe的引入改善了Co纳米线的磁性能,使其呈现出较大的矫顽力和较高的矩形比.采用一致转动模型和对称扇形机理的球链模型分别计算了FeCo合金纳米线的矫顽力, 发现其磁化反转机理与对称扇形机理的球链模型相符合.     

Fe3+、碲对硒的氢化物化学干扰机理的实验研究

本文实验了研究的氢化物发生中Ｆｅ＾３＋与碲的协同反应对原子荧光法测硒的化学干扰。     

NiAl合金纳米线弯曲形变行为的分子动力学模拟

本文采用分子动力学模拟研究不同条件下NiAl合金纳米线的弯曲形变行为。研究结果表明：NiAl合金纳米线弯曲过程包括弹性和塑性形变两个阶段,其中,在弹性形变阶段计算得到纳米线的弯曲模量为48.9 GPa,与已有计算结果接近;而纳米线塑性形变以应力诱发B2→L1₀马氏体相变为变形载体,且形变行为不依赖于体系温度、应变速率及纳米线尺寸等因素,即使在低温和高应变速率下纳米线也表现出良好的弯曲塑性和弯曲强度。此外,NiAl合金纳米线在弯曲作用下具有近零滞后的超弹性特征,弯曲形变在卸去载荷时可完全回复。     

HG-AFS测定高纯碲中痕量硒干扰的消除

用HNO₃+HCl分解样品,采用Fe3+-柠檬酸混合溶液作抑制剂,研究了下氢化物发生-原子荧光光谱法测定痕量硒时的干扰及其机理,探讨了NO-₃和NO-₂残留的影响,并用正交试验设计结合单因素试验研究了不同浓度Fe3+盐、盐酸、柠檬酸、硼氢化钾等条件下Se的回收率。该方法的检出限为0.15 μg·L-1,样品中Se含量为27.01 μg·L-1的相对标准偏差在3.1%～4.2%之间(n=11),加标回收率为96.1%～102.3%。用于实际样品的测定,结果满意。     

氢化物-无色散原子荧光法同时测定钢铁中痕量硒和碲

本文研究了氢化物－无色散原子荧光法同时测定钢铁中痕量硒和碲。采用离子交换法消除了阳离子干扰。在４０％（Ｖ／Ｖ）盐酸介质测定硒和碲，方法检出限分别为０．２７和０．３３ｎｇ／ｍＬ，相对标准偏差分别为６．９９和６．１１％，回收率在９６．７￣１０２．０％之间。     

Topological surface states of Bi2Te2Se are robust against surface chemical modification

The robustness of the Dirac‐like electronic states on the surfaces of topological insulators (TIs) during materials process‐ing is a prerequisite for their eventual device application. Here, the (001) cleavage surfaces of crystals of the topological insulator Bi₂Te₂Se (BTS) were subjected to several surface chemical modification procedures that are common for electronic materials. Through measurement of Shubnikov–de Hass (SdH) oscillations, which are the most sensitive measure of their quality, the surface states of the treated surfaces were compared to those of pristine BTS that had been exposed to ambient conditions. In each case – surface oxidation, deposition of thin layers of Ti or Zr oxides, or chemical modification of the surface oxides – the robustness of the topological surface electronic states was demonstrated by noting only very small changes in the frequency and amplitude of the SdH oscillations. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

AlM(M=O,S,Se,Te,Po)势能函数和光谱研究

本文用B3LYP方法,相对论有效实势,其中铝原子用6-311 G(d,p)基组,其它用sddall基组分别对AlM(M=O,S,Se,Te,Po)分子进行了优化计算,得出了它们的平衡结构和双原子分子光谱常数.计算结果表明:它们的基态结构分别为AlO(2Σ),AlS(2Σ),AlSe(2Σ),AlPo(2Σ),其中AlO和AlS的计算数据与实验结果是一致的.氧簇元素原子与铝结合的中性双原子分子的平衡距离,随原子序数的增加而增长,离解能随原子序数的增加而减小,但它们都能形成稳定的双原子中性分子.它们的谐振频率随原子序数的增加而减小,它们的最低空轨道和最高占据轨道能量随原子序数的增加而略有增加,但变化不大.其能隙随原子序数的增加而略有增加.本文从理论上系统地研究了氧簇元素的原子(包括放射性较强,不太稳定的Po)与铝原子形成的中性双原子分子的光谱和分析势能函数.     

非晶碳氧化硅纳米线的合成与光致发光

利用直流电弧放电合成非晶碳氧化硅(SiCO)纳米线,不使用催化剂和模板,独立的SiCO 纳米线沉积在石墨锅的表面．通过XRD、SEM、TEM、XPS、FTIR等对SiCO纳米线进行了表征．结果表明,纳米线长度为20～100 μm,直径为10～100 nm,Si原子同C原子和氧原子分享成键组成SiCO单元．SiCO纳米线的光致发光谱在454和540 nm呈现了强而稳定的白色发光峰． SiCO纳米线的生长机制为等离子辅助气―固生长机制．     

A b initio calculation of the growth of Te nanorods and Bi2Te3 nanoplatelets

In this paper the growth mechanism of a Te/Bi2Te3 novel structure is studied by ab-initio calculations. The results show that the growth of Te nanorods is determined by the adsorption energy of Te atoms on different crystalline Te surfaces. The adsorption energy of Te on the Te （001） surface is 3.29 eV, which is about 0.25 eV higher than that of Te on the Te （110）. This energy difference makes the preferential growth direction along the 〈 001 〉 direction. In addition, the higher surface energy of Bi2Te3 （110） and the lattice misfit between crystalline Bi2We3 and Te along 〈 001 〉 direction are considered to explain the growth of the Bi2Te3 nanoplatelets, in which Volmer-Weber model is used. The theoretical results are in agreement with experimental observation.     

应变层异质结ZnS/ZnSe、ZnS/ZnS_xSe_(1-x)和ZnSe/ZnS_xSe_(1-x)价带带阶的研究

采用基于原子球近似下线性Ｍｕｆｉｎ－Ｔｉｎ轨道（ＬＭＴＯ－ＡＳＡ）的平均键能计算方法，研究了以ＺｎＳｘＳｅ１－ｘ为衬底，沿（００１）方向外延生长的应变层异质结ＺｎＳ／ＺｎＳｅ、ＺｎＳ／ＺｎＳｘＳｅ１－ｘ和ＺｎＳｅ／ＺｎＳｘＳｅ１－ｘ的价带带阶值ΔＥｖ（ｘ）．研究表明，ΔＥｖ（ｘ）值随衬底合金组分ｘ单调变化．且两者的关系是非线性的．在此计算结果与其它理论计算和实验结果符合较好．     

Controlled Synthesis of a High-Mobility Bi3O2.5Se2 Semiconductor by Oxidation of Bi2Se3 for Fast and Highly Sensitive Photodetectors

The search of new high-mobility two-dimensional (2D) semiconductors is crucial for the development of next-generation photodetectors, since current photodetectors based on single 2D semiconductors usually cannot simultaneously own ultrafast response rate and ultrahigh sensitivity. Here, using a facial method of sequentially oxidizing Bi₂Se₃ at optimal O content, a series of bismuth oxyselenide semiconductors (Bi₃O_2.5Se₂, Bi₂O₂Se, Bi₂SeO₅) with appealing electronic applications are successfully synthesized. The crystal and band structures of a superlattice-free Bi₃O_2.5Se₂ phase are resolved by 3D electron diffraction and density functional theory calculations, showing a unique non-neutral layered structure, moderate band gap, and small effective mass. More importantly, the concept of Bi₂Se₃ + O₂ can be extended to synthesize the superlattice-free Bi₃O_2.5Se₂ ultrathin films by chemical vapor deposition, whose room-temperature mobility can be as high as ≈150 cm² V⁻¹ s⁻¹ based on Hall measurements. The ultrathin Bi₃O_2.5Se₂ photodetectors with a simple device configuration simultaneously own ultrafast response time (≈31 µs), ultrahigh responsivity (≈8 × 10⁴ A/W), and large detectivity (≈8 × 10¹³ Jones). This work not only introduces a facile way to regulate the phase in the bismuth oxyselenide family, but also provides an alternative candidate for ultrafast and ultrasensitive photodetectors.     

Molecular Structures of H2X and D2X(X=0, S,Se, Te)

There are two possible configurations for H₂O, linear(D_∞h) or bent(C_2v). For a C_2v′, the three bands ν_1′ ν₂ and ν₃ should appear in both Raman and infrared. For a D_∞h. however, the ν₁, band should appear in only Raman and the ν₂ and ν₃ bands, in only infrared, that is, a principle of mutual exclusion of Raman and infrared should hold. The present author concludes that H₂X and D₂X(X=O, S, Se, Te) have a linear D_∞h. structure, since the obtained spectra show mutual exclusion of Raman and infrared.     

Te/C coaxial nanocable as a supporting material for loading ultra-high density Pt nanoparticles at room temperature

We have developed a facile procedure to load ultra-high density Pt NPs with the size of about 3 nm on the surface of Te/C coaxial nanocable based on the -OH, -COOH hydrophilic groups on the carbon surface through directly mixing the Te/C coaxial nanocable, H₂PtCl₆, HCOOH and water at room temperature. Comparing with carbon nanotubes, the present procedure needed neither complex functionalization process nor any additional linkers. Notably, the amount of Pt NPs on the surface of coaxial nanocables could be easily controlled via changing the amount of Te/C coaxial nanocables in the mixture.