化学气相沉积制备铜锌合金微米杆

采用化学气相沉积的方法,以锌粉、硝酸铜为原料,在硅衬底上制备了铜锌合金微米杆.用X射线衍射(XRD)、扫描电子显微镜(SEM)和X射线能谱(EDS)对沉积产物的结构、形貌和成分进行了测试与表征.结果表明,生长的铜锌合金微米杆为金属间化合物Cu3Zn合金,为立方相结构,直径在0.1 ～5 μm之间,长度可达3～30μm.锌在铜锌合金微米杆的生长中起着至关重要的作用.铜锌合金微米杆的生长属于气固反应诱导下的气液固(VLS)生长机制,与经典的气液固(VLS)生长机制具有明显不同的特点.     

单质直接气相生长ZnSe单晶

本文直接以高纯Zn、Se单质为原料,加入少量碘单质作为反应输运剂,用化学气相输运(CVT)的方法一步成功的生长出了ZnSe单晶.采用XRD、EDS、紫外可见分光光度计和光致发光(PL)技术研究了生长的ZnSe晶体的结构、成份以及光学特性.结果表明,生长的ZnSe单晶具有较好结晶性能,成份接近理想的化学计量比,在500～2000nm范围内透过率达到65;～70;,在1.9～2.5 eV范围内存在与Zn空位和杂质能级相关的发光带.由Zn和Se单质在输运剂I2的辅助下一步直接生长ZnSe单晶是可行的.     

ZnSe薄膜的化学反应辅助热壁外延法生长及特性研究

本文通过将新型化学气相反应促进剂Zn(NH4)3Cl5引入到热壁外延系统中,以二元素单质Zn和Se为原料,直接在Si(111)衬底上生长了高质量的ZnSe晶体薄膜,薄膜成分接近理想化学计量比。研究了主要工艺参数对薄膜生长形貌和性能的影响。采用SEM、AFM、EDS和PL谱技术研究了生长的ZnSe薄膜的形貌、成分和发光特性。研究结果表明,热壁温度和生长时间是影响ZnSe薄膜形貌的主要因素;气相反应促进剂在薄膜生长和调节成分方面扮演了关键角色,Zn(NH4)3Cl5的存在使得Zn(g)和Se2(g)合成ZnSe晶体的反应转变为气固非一致反应,从而更容易获得近乎理想化学计量比的ZnSe薄膜。ZnSe薄膜在氦镉激光激发下,室温下PL谱由近带边发射和(VZn-ClSe)组合的SA发光组成,而在飞秒激光激发下,仅在481nm处显示出强烈的双光子发射峰。     

Zn-Mg-Se-I2系统生长ZnMgSe单晶及其特征

以高纯的Zn、Mg以及Se2单质为生长原料,加入高纯的碘单质作为反应输运剂,采用化学气相输运(CVT)方法成功制备了ZnMgSe单晶,并且分别采用X射线衍射、双晶衍射、紫外可见分光光度计、红外光谱仪以及光致发光(PL)技术研究了晶体的结构、结晶质量以及光学性质.结果表明,制备的单晶结晶性能良好,在500 ～ 1500 nm波长范围内的透过率接近50;,在400 ～ 4000 cm-1波长范围内的透过率达到42;,在2.0～2.6 eV范围内有三个明显的空位与杂质发光带.以Zn、Mg及Se2单质为生长原料,在输运剂I2的帮助下可以实现ZnMgSe单晶的生长.     

CVT一步生长的ZnSe单晶的光电特性研究

本文采用化学气相输运(CVT)法,由Zn(5N)和Se(5N)一步直接生长了片状ZnSe单晶,并对其结构特性和光电性能进行分析。研究表明,生长出的ZnSe单晶仅显露(111)面,红外透过率约为40%～42%,具有较高的结晶质量。该ZnSe单晶可与In电极形成良好的欧姆接触,其体电阻率约为7.3×109Ω.cm。     

类金刚石Ⅰ2-Ⅱ-Ⅳ-Ⅵ4型红外非线性光学材料的结构与性能关系研究

硫属化合物由于高的非线性光学系数和宽的红外透过范围,广泛应用于军事和民用红外领域.其中类金刚石材料具有内在的非中心对称结构,能够满足作为非线性光学材料的先决条件,而且Ⅰ2-Ⅱ-Ⅳ-Ⅵ4化学式类型(Ⅰ=Li,Ag,Cu;Ⅱ=Zn,Cd,Hg,Mg,Co,Fe;Ⅳ=Si,Ge,Sn;Ⅵ=S,Se)成为目前研究的重要体系之一.调研发现已知的78个具有非中心对称结构的Ⅰ2-Ⅱ-Ⅳ-Ⅵ4类金刚石型硫属化合物,全部结晶于以下7个不同的空间群Pmn21,Pna21,Pn,I4,I42m,Cmc21,F222.本文系统概述了不同空间群下的类金刚石材料的结构特点和非线性光学性能,为未来设计性能优异的红外非线性光学晶体提供理论指导.     

Zn3(VO4)2微米球的制备及其光吸收性能

以硝酸锌及偏钒酸铵为原料,采用沉淀法结合高温热处理获得了Zn3(YO4)2微米球结构.利用X射线衍射仪(XRD)、场发射扫描电子显微镜(FE-SEM)对样品的物相组成和微观结构进行了表征;通过热重-差热分析(TG-DTA)对前驱体分解过程和分解温度进行了研究.结果表明:硝酸锌与偏钒酸铵混合后通过沉淀反应首先获得了Zn3V2O7(OH)2-2H2O微米球,前驱体经350℃煅烧后生成了Zn3(VO4)2微米球,该微米球由厚度约为80 nm的纳米片组装而成,推测其形成机理为各向异性生长和自组装Oswald熟化过程的结合.实验发现沉淀过程的反应温度及体系pH值对Zn3(VO4)2材料的形貌具有一定的影响作用.紫外-可见漫反射测试(UV-vis DRS)表明Zn3(VO4)2微米球在紫外光区具有较强的吸收性能,通过计算得出Zn3(VO4)2微米球的光学带隙为3.09 eV.     

氧分压对化学气相沉积法合成ZnO纳米结构形貌的影响

本文利用化学气相沉积(CVD)法在镀有Au(10 nm)膜的单晶Si(100)上制备了ZnO薄膜,并研究了不同的氧分压对ZnO形貌的影响.借助扫描电镜(SEM)、X射线衍射仪(XRD)和透射电子显微镜(TEM)对样品的形貌、结晶质量和晶体生长取向进行了表征.结果表明:当O2分压较小的时候,O2只能与Zn团簇的某些界面发生反应并逐渐结晶生成层状的ZnO微米团簇.当 O2分压较大的时候,ZnO通过二次生长形成由微米柱阵列和表面无序纳米线构成的分层复合结构,并且表面纳米线的密度随着氧分压的增加而增加.高分辨透射电镜(HRTEM)和选取电子衍射(SAED)分析表明,单根纳米线是沿[001]方向生长的ZnO单晶.     

锡硫属化物[M(en)3]2[Sn2Se4S2](M=Mn,Co)的溶剂热合成,晶体结构与性质表征

在乙二胺溶剂体系中,180 ℃条件下合成了两种化合物[Mn (en)3]2[Sn2Se4S2](1)和[Co(en)3]2[Sn2Se4S2](2).通过X-射线单晶衍射、SEM、IR、TGA和UV-Vis等手段对其进行了表征.X-射线单晶衍射结果表明化合物1和2是类质同晶,均为正交晶系,并属于Pbca空间群,结构中均含有Sn和两种硫属元素S、Se组成的二聚体阴离子[Sn2Se4S2]2-.两种晶体的晶胞参数分别为:化合物1,a=1.6020(8) nm,b=1.1842(6) nm,c=1.9658(10) nm,Z=8;化合物2,a=1.549t(5) nm,b=1.1688(4) nm,c=1.18666(6) nm,Z=8.紫外-可见漫反射光谱研究结果表明,化合物1和2的禁带宽度分别为1.54 eV和1.64 eV,均有半导体性能.     

真空蒸发法制备ZnSe薄膜的X射线光电子能谱研究

本文用真空蒸发法制备了CIS太阳能电池中做缓冲材料的ZnSe薄膜,利用X射线光电子能谱(XPS)对制备薄膜的表面化学状态及沉积质量进行了研究,并用氩离子溅射进行剥蚀,逐层分析薄膜的化合态随深度的变化关系.XPS分析表明,ZnSe薄膜含有Zn、Se、O、C等元素,其中O、C为样品置于空气中所致,含量随剥蚀深度的加大而逐渐降低.Zn的光电子峰为Zn2p1/2和Zn2p3/2,Zn2p3/2的电子结合能为1021.90eV,对应着Zn2+的化合态,表明薄膜中zn以形式电荷为Zn2+的化合态形式存在;Se的光电子峰为Se3d,其电子结合能为54.30eV,对应着Se2-的化合态,表明薄膜中Se以形式电荷Se2-的化合态形式存在.分别经过1min、3min、7min、11min的剥蚀后,Zn和Se的光电子峰几乎没有改变,表明沉积的ZnSe薄膜表面和内部化学状态稳定一致.     

Local and medium range order in germanium chalcogenide glasses

The results of EXAFS measurements on GeX_x X = S, Se and 1.5 x 15) binary are reviewed. This structural study is completed by anomalous wide angle X-ray scattering experiments for vitreous GeSe₃ and GeSe₅. Thus, the local and the medium range order of these glasses have been charaterized.     

Crystal and Molecular Structures of Di-1-Adamantylthiophosphinic Chloride, <Emphasis Type="Italic">P</Emphasis>,<Emphasis Type="Italic">P</Emphasis>-Diphenyl-<Emphasis Type="Italic">N</Emphasis>-Benzyl Phosphinothioic- and Selenoic- Amides

Abstract  Synthesis and X-ray structural determination of three phosphorus compounds are reported. (3b) is monoclinic P2(1)/c with a = 11.852(1), b = 12.825(1), c = 12.445(1) ?, β = 103.693(1)o; (4a) and (4b) are monoclinic P2(1)/n with a = 12.1422(16), b = 9.0860(12), c = 14.845(2) ?, β = 96.498(3)o for (4a), and a = 12.2714(16), b = 9.2812(12), c = 14.800(2) ?, β = 97.176(2)o for (4b). They all exhibit distorted tetrahedral geometry about the P atom. Ph₂P(X)NHC₇H₇ (X=S (4a) and X=Se (4b)) show typical P–S and P–Se double bond distances and P–N single bonds, while P–S bond in 1-Ad₂P(S)Cl (3b) is comparable to P–S single bonded probably due to the largeness of 1-adamantyl groups. Graphical Abstract  Synthesis and X-ray structural determination of 1-Ad₂P(S)Cl (3b), Ph₂P(S)NHC₇H₇ (4a) and Ph₂P(Se)NHC₇H₇ (4b) are reported.      

Janus型二维磁电材料CrXX’(X/X’=S,Se,Te)第一性原理研究

自石墨烯被发现以来,各种具有新奇特性的二维材料受到了越来越多的关注。Janus型二维材料具有不对称的表面特性,这种特殊的结构往往具有独特的电学、磁学与光学性质,使其成为近年来材料科学领域研究的热点。本文搭建了Janus型结构CrXX’(X/X’=S,Se,Te)(CrSSe, CrSTe, CrSeTe),研究了体系的电学、磁学、光学性质,并探究了双轴应变对其电学、磁学、光学性质的影响。结果表明,CrSSe、CrSTe与CrSeTe均呈现金属性,都是电子的优良导体,三种体系的电子结构对外加应变具有很好的鲁棒性。CrXX’(X/X’=S,Se,Te)具有本征铁磁性,并且通过施加双轴应变可对其磁矩进行调控。此外,三种体系均具有较高的居里温度,特别是CrSTe的居里温度可达310 K。CrXX’(X/X’=S,Se,Te)还具有优异的可见光与紫外光吸收性能,应变可对其光吸收系数进行调控,并且压应变与拉应变可分别使其吸收谱线向短波与长波方向移动。本文的工作为进一步研究二维Janus单层CrXX’(X/X’=S,Se,Te)在新型室温自旋电子器件领域的应用提供了理论支持。     

硒代锡酸盐Cd(tren)SnSe3的溶剂热合成与晶体结构

采用溶剂热法合成了一种新的硒代锡酸盐Cd(tren)SnSe3(tren=三(2-氨乙基)胺).单晶X-射线衍射分析表明该化合物为三斜晶系,空间群为P-1,a=0.7752(3)nm,b=0.8128(2)nm,c=1.2467(4)nm,α=97.299(19)°,β=103.639(18)°,γ=107.325(17)°,V=0.7121(4)nm3,Z=2,Dc=2.865 Mg·m-3,Mr=614.21,F(000)=564.该化合物为零维簇状结构,是由[Sn2Se6]单元的反式末端Se原子连接两个[Cd(tren)]2+单元形成的.紫外-可见漫反射光谱研究结果表明,该化合物的禁带宽度为1.80 eV.     

Sb2(S1-x Sex)3(0≤x≤1)薄膜太阳能电池的研究进展

Sb2(S1-xSex)3(0≤x≤1)化合物是重要的半导体材料,主要包括Sb2Se3、Sb2Se3及Sb2(S,Se)3三种材料,元素储量丰富且环境友好、组分简单、价格低廉,同时其禁带宽度合适(1.1～1.8 eV),吸光系数大(＞105 cm-1),非常适合用作新型低成本低毒的薄膜太阳能电池的吸收层,有可能成为下一个研究热点.本文综述了近几年来Sb2Se3、Sb2Se3及Sb2(S,Se)3薄膜太阳能电池的研究进展,并对其发展趋势进行了展望.     

Recent developments in the MOVPE growth of low H content ZnSe-based compounds and heterostructures

The origin of unintentional hydrogen (H) incorporation during metalorganic vapour phase epitaxy (MOVPE) of ZnSe-based compounds is reviewed and discussed. Hydrogen enters in MOVPE-grown ZnSe as a result of alkyls surface reactions, effectively passivating intentional nitrogen (N) acceptors in p-doped ZnSe during the fabrication of blue-light emitting diodes and laser diodes. The existence of a marked trade-off between the proclivity of common Se alkyls to incorporate H and their thermal stability is pointed out. Current strategies to overcome this process limitation are then described along with results achieved and technological drawbacks. The use of a novel class of VI-group alkyl precursors of the form R₂X₂ [where X=Se, S and R is an ethyl (Et) or methyl (Me) radical] is proposed as an alternative solution. These alkyls allow a reduction of H incorporation in ZnSe-based materials, whilst retaining the low temperatures required for the growth of device quality wide band-gap II–VI compounds. Dimethyldiselenide (Me₂Se₂) and diethyldisulphide (Et₂S₂) allow the pyrolytic MOVPE growth of Zn(S)Se compounds below 400 °C. Mass spectrometry fragmentation experiments performed on the alkyl molecular ions allowed to investigate their relative bond strengths and likely decomposition paths. The reduced thermal stability of these alkyls is attributed to a weakening of the XC bonds in the R₂X₂ molecule induced by the stronger XX bond. Secondary ion mass spectrometry (SIMS) analysis showed that as-grown ZnSe have [H]≈(1–3)×10¹⁷ cm⁻³, i.e. among the lowest ever reported for MOVPE-grown layers. The functional validation of the new S and Se alkyls is completed by the structural and optical characterisation of Zn(S)Se-based heterostructures grown on (100)GaAs. High-resolution X-ray diffraction studies are presented along with cathodoluminescence (CL) measurements and compared to what reported in the literature. The epilayer structural properties compare well with that of molecular beam epitaxy and MOVPE grown Zn(S)Se heterostructures. CL spectra of ZnSe epilayers appear of good quality, with pronounced band-edge emissions and reduced deep level contributions. Specific emissions in the spectra of ZnS and ZnSe confirm the occurrence of several impurities in the layers, whose origin can be in part attributed to the yet insufficient purity of the novel alkyls.     

Positron annihilation study of defects and microheterogeneity of chalcogenide glassy semiconductors — chemical bonding in ge—se and some AVBVI systems

Recently developed ideas on the mechanisms of positron annihilation in chalcogenide glassy semiconductors are used in studying chemical bonding of the A^VB^VI structures (A = As, B = S, Se, Te) and Ge Se.     

Crystal and molecular structure of N-(Diethylaminothiocarbonyl)-N′-phenyl-benzamidine

The crystal structure of the title compound has been determined by X-ray diffractometer data collected on a CAD-4 diffractometer. C₁₈H₂₁N₃S crystallizes monoclinic, space group P 2₁/n with a = 8.939(1) Å, b = 18.992(3) Å, c = 10.416(2) Å, β = 97.29(2) Å and Z = 4. Least-squares refinement gave a value of R = 0.107 for 2647 observed reflections. The molecule has a configuration which can be described best by Z, E′ and exists in the tautomeric enamine form. The molecules form infinite chains connected by intermolecular N—H … S interactions, with H … S distances of 2.46 Å.     

Template free-solvothermaly synthesized copper selenide (CuSe,Cu2−xSe, β-Cu2Se and Cu2Se) hexagonal nanoplates from different precursors at low temperature

Nonstoichiometric (Cu_2−xSe) and stoichiometric (CuSe, β-Cu₂Se and Cu₂Se) copper selenide hexagonal nanoplates have been synthesized using different general and convenient copper sources, e.g. copper chloride, copper sulphate, copper nitrate, copper acetate, elemental copper with elemental selenium, friendly ethylene glycol and hydrazine hydrate in a defined amount of water at 100 °C within 12 h adopting the solvothermal method. Phase analysis, purity and morphology of the product have been well studied by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray diffraction (EDAX) techniques. The structural and compositional analysis revealed that the products were of pure phase with corresponding atomic ratios. SEM, TEM and HRTEM analyses revealed that the nanoplates were in the range 200–450 nm and the as-prepared products were uniform and highly crystallized. The nanoplates consisted of {0 0 1} facets of top–bottom surfaces and {1 1 0} facets of the other six side surfaces. This new approach encompasses many advantages over the conventional solvothermal method in terms of product quality (better morphology control with high yield) and reaction conditions (lower temperatures). Copper selenide hexagonal nanoplates obtained by the described method could be potential building blocks to construct functional devices and solar cell. This work may open up a new rationale on designing the solution synthesis of nanostructures for materials possessing similar intrinsic crystal symmetry. On the basis of the carefully controlled experiments mentioned herein, a plausible formation mechanism of the hexagonal nanoplates was suggested and discussed. To the best of our knowledge, this is the first report on nonstoichiometric (Cu_2−xSe) as well as stoichiometric (CuSe, β-Cu₂Se and Cu₂Se) copper selenide hexagonal nanoplates with such full control of morphologies and phases by this method under mild conditions.     

Absolute structure of (11E, 1S, 3S, 4R, 7S, 8R, 14S)-3,7-diiodo-4,8-epoxy-euniolide

3,7-Diiodo-4,8-epoxy-euniolide (2) was synthesized from euniolide (1) by the addition reaction of iodine in the presence of triphenylphosphine in CH₂Cl₂. The absolute structure of 2 was unambiguously determined by a combination of ¹H and ¹³C NMR, HREI mass spectroscopy, and x-ray single crystal analysis as (11E, 1S, 3S, 4R, 7S, 8R, 14S)-3,7-diiodo-4,8-epoxy-cembra-11,15-dien-16,14-olide. X-ray crystallographic data for 2: Orthorhombic P2₁2₁2₁ (#19), a = 10.9688(7), b = 11.3909(8), c = 16.885(1) Å, _calcd = 1.795 g cm^–3, and for Z = 4.