CdTe(110)表面原子与电子结构的第一性原理研究

采用基于密度泛函理论的第一性原理计算了CdTe(110)表面的原子和电子性质.结果表明,CdTe(110)理想表面在禁带中出现两个明显的表面态,弛豫后表层Cd原子和Te原子p态电子发生转移,Cd原子趋向于sp2平面杂化构型,Te原子趋向p3杂化的锥形构型.经过表面弛豫大大降低了表面能,增大了表面功函数,表面占据态和表面空态分别被推进价带顶之下和导带底之上,导致弛豫表面没有明显的表面态.     

退火处理对CdZnTe晶体光电性能的影响

研究了生长态CdZnTe晶体在经历了不同温度和时间的Cd/Zn和Te气氛退火后,其光电性能的变化规律.研究表明,在Cd/Zn气氛下退火180 h后,CdZnTe晶体中直径在5μm以上的Te夹杂的密度减小了1个数量级,晶体的体电阻率由1010 Ω·cm减小至～107 Ω· cm.同时发现,Cd/Zn源区的温度决定了退火后晶体在500～4000cm-1范围内红外透过率曲线的平直状态,这可能与晶体中的Cd间隙缺陷浓度相关,而与晶体中的载流子浓度和夹杂/沉淀相状态无关.在Te气氛下退火时,发现晶体的红外透过率的平直状态与晶体电阻率的对数lg(ρ)呈近似线性关系,同样可归因于退火过程中Cd间隙缺陷的浓度变化.     

Cd1-xZnx合金组元分压控制下高阻CdZnTe晶体的熔体生长

本文运用热力学关系估算了CdZnTe熔体平衡分压.尝试以Cd1-xZnx合金源替代Cd源控制Cd分压和Zn分压进行了Cd 0.8Zn 0.2Te晶体熔体生长,探讨了熔体分压与晶体电阻率的关系.获得的Cd 0.8Zn 0.2Te晶体的电阻率接近1010Ω·cm,高于同类方法文献报道1～2个数量级.晶体的结构完整性较好,平均腐蚀坑密度(EPD)为2×105cm-2,纵向组成分布偏离度在4;左右,红外透过率大于60;,晶体中第二相和沉淀物明显减少,优于仅采用Cd分压控制的Cd0.8Zn0.2Te晶体.     

Fe对InP材料电子结构及光学性质的调控机理研究

采用基于密度泛函理论的线性缀加平面波(FLAPW)方法,研究了3d族过渡金属元素Fe对Ⅲ-Ⅴ族半导体InP的电子结构和光学性质的调控机理,并对其能带结构和电荷密度分布进行了分析.结果表明,InP为直接带隙半导体,其价带主要由P-3s和3p态构成,而导带则由In-5s电子态构成.当Fe元素替代In原子后,由于Fe和P原子的轨道杂化作用,InP带隙中出现杂质态,Fe-3d态产生自旋极化效应.随着Fe的掺杂浓度增大,Fe-P原子之间轨道杂化作用明显增加,费米能级逐渐进入价带,这导致了材料的电子跃迁几率提高,光学吸收边明显增强,跃迁峰发生红移.     

基于第一性原理的Au、Cu、Sb掺杂CdTe的结构模拟和光学性能预测

基于密度泛函理论研究了Au、Cu、Sb掺杂CdTe体系的电子结构和光学性能。Au、Cu、Sb掺杂CdTe体系均能稳定存在，过渡金属原子与Cd原子轨道的杂化减小了CdTe的带隙，提高了CdTe对可见光的利用，同时降低了光生电子从价带跃迁到导带所需的能量，从而促进了更多的光生电子发生迁移，大大提高了其光学性能。三种掺杂体系中Sb/CdTe体系在可见光范围内光吸收系数提升最显著，其光生电子和光生空穴迁移率相对于CdTe体系分别增加5.97倍和15.54倍。通过计算掺杂体系的能带、态密度、电子布居、光吸收函数、载流子迁移率，从理论上揭示了Au、Cu、Sb提高CdTe光学性能的机理。     

CdZnTe晶体位错处的Raman光谱及PL谱研究

利用显微Raman光谱技术,对比研究了CdZnTe晶体无位错区和位锘密集区的Raman光谱.研究发现,CdZnTe晶体无位错区的Raman光谱出现了与Te有关的A1模(119 cm-1)、类CdTe的TO1模(138 cm-1)和类ZnTe 的TO2模(179 cm-1);CdZnTe晶体位错密集区的Raman光谱中仅出现了与Te有关的A1模和类CdTe的TO1模,CdZnTe晶体类ZnTe的TO2模消失.对CdZnTe试样位错密集区进行变温光致发光谱测试,结果表明,束缚在中性施主上的激子的离解为电子空穴对,电子空穴的非辐射复合过程吸收了类ZnTe的TO2模声子能量,造成Raman 光谱中类ZnTe的TO2模缺失.     

移动加热器法生长CdMnTe和CdZnTe晶体的性能研究

采用移动加热器法生长铟惨杂浓度为5×1017 atoms/cm3的Cd0.9Mn0.1Te (CMT)和Cd0.9Zn0.1Te (CZT)单晶.生长得到的CMT晶体和CZT晶体电阻率范围为4.5×109 ～ 6.2×1010 Ω·cm.CMT晶体的成分均匀性要优于CZT晶体,拟合得到CMT和CZT晶体中Mn和Zn的分凝系数分别为0.95和1.23.富Te区在两种晶体生长过程中都具有显著的提纯作用,In惨杂的浓度范围均在6.4 ～ 14.4 ppm范围内.红外透射显微镜观察到三角形和六边形为主的Te夹杂的尺寸5 ～24 μm,浓度为105 cm-3.除最后结晶区之外,沿晶体生长方向Te夹杂的尺寸逐渐减小而浓度逐渐增大.制备的CMT和CZT探测器对59.5 keV241Am放射源均有能谱响应,能量分辨率分别为23.2;和24.6;.     

富Te条件下CdTe晶体中的点缺陷研究

基于缺陷化学理论,考虑到富Te的CdTe晶体中可能存在的点缺陷,建立了在Te气氛下退火时,热力学平衡态晶体中的点缺陷模型,其中包括Cd间隙(Cdi)、Cd空位(VCd)、Te间隙(Tei)和Te反位(TeCd).利用质量作用定律和伪化学平衡方程计算了富Te情况下本征CdTe晶体中的点缺陷浓度和费米能级.计算结果系统的揭示了点缺陷浓度、费米能级、Te压以及退火温度之间的关系,发现只有TeCd浓度足够大时才能对费米能级产生钉扎作用.     

Zn掺杂纤锌矿CdSe电子结构和光学性质的第一性原理研究

采用密度泛函理论中的广义梯度近似平面波超软赝势方法,计算研究了不同浓度Zn原子掺杂纤锌矿结构CdSe的电子与光学性质.结果显示:随着Zn掺杂浓度的升高,纤锌矿Cd1-xZnxSe的体积在减小,形成能降低,掺杂越容易,稳定性变高;Zn掺杂引起导带底向高能方向移动,禁带宽度逐渐增加;掺杂后形成的Zn-Se键具有更大的密立根重叠布居数,表现出更强的共价性;体系的直接带隙宽度增加,导致光电子跃迁峰向高能方向发生蓝移;在紫外光区9.75eV左右,掺杂体系的吸收强度达到最大,能量损失最小.     

p型CdZnTe晶体(111)B面的Au/Zn复合电极的制备和研究

通过对p型CdZnTe(111)面的结构分析,用真空蒸发法在p型CdZnTe晶体(111)面制备出Au/Zn复合电极,运用金相显微镜、AFM测试、SEM剖面观察、EDS成分分析、Ⅰ-Ⅴ特性测试及势垒高度计算等多种手段研究了Au/Zn复合电极对金属和半导体接触性能的影响.结果表明,在P型CdZnTe(111)A面蒸镀Au电极,在B面蒸镀Au/Zn复合电极时获得的势垒高度最低,有效减小了富Te面对金半接触的影响.Au/Zn复合电极能获得比Au电极更理想的接触性能.     

The crystal and molecular structure of N-(methylsulfonyl)-N-(2,6)-(dimethylphenyl)methanesulfonamide

The title compound, crystallizes in the triclinic space group witha=8.232(4),b=9.159(2),c=10.230(3)Å. =74.07(3)°, =72.50(4)°, =63.65(3)° andZ=2. The structure was solved by direct methods and refined by full matrix least squares methods toR=0.054 for 1817 observed reflections. The plane containing the nitrogen and sulfur atoms is perpendicular to the aromatic plane. One of the S–O bonds in each methanesulfonyl group is in nearly eclipsed conformation with the N–C bond.     

Single crystals of calcium and strontium phenylphosphonate grown via hydrothermal crystallization

Single crystals of Ca(HO₃PC₆H₅)₂ (1) and Sr(HO₃PC₆H₅)₂ (2) have been obtained via the crystallization of their respective amorphous powders. The amorphous compounds were synthesized by traditional solution routes and were subsequently crystallized at 160°C in a Teflon-lined autoclave containing 1–3 mL distilled water. The resultant single crystals were physically isolated and their structures determined by single crystal X-ray diffraction. The two compounds are isostructural and crystallize in space group C2/c with lattice parameters of a = 31.267(3) ?, b = 5.6185(6) ?, c = 7.7202(8) ?, β = 101.924(2)°; and a = 31.514(4) ?, b = 5.8098(8) ?, c = 7.8218(10) ?, β = 102.063(3)° for the calcium and strontium phenylphosphonate, respectively.     

The crystal and molecular structures of cyclohexanone thiosemicarbazone

Cyclohexanone thiosemicarbazone (Hchtsc) crystallizes in the triclinic crystal system with space group P (No. 2) and the following unit cell parameters: a = 6.2989(2), b = 7.9730(3), and c = 9.4118(2) Å = 79.607(3), = 85.519(2), and = 73.50(2)° V = 445.60(2) ų, Z = 2. The lengths of the bonds C(1)–S, C(1)–N(1), C(1)–N(2), and N(2)–N(3) suggest electron delocalization in all four. The S atom is trans to N(3), and this E configuration is stabilized by intramolecular hydrogen bonding between N(3) and the N(1)H₂ group. Two intermolecular hydrogen bonds involving the S atom and the N(1)–H(1b) and N(2)–H(2) groups give rise to a polymeric chain of molecule pairs.     

新型铝硅酸盐磷光体的结构及性能研究

以凝胶燃烧法在相对较低温度下合成了长石型的蓝白色长余辉材料Sr0.94Al2Si2O8:Eu2+0.02,Dy3+0.04,并用X射线粉末衍射(XRD)、荧光分光光度计(FL)以及扫描电子显微镜(SEM)等技术对样品的物相结构、光谱性质、微观形貌及粒度等进行了分析表征.结果发现:尿素用量、点火温度、还原温度及时间、冷却方式等工艺条件均直接影响样品的晶体结构,进而影响其发光性质.长余辉性能最佳时产物属于六方晶系及单斜晶系的混晶;其激发峰是位于290～400nm处的宽带峰;发射峰是位于380～520nm处的宽带峰,由两个发光中心构成,390nm处的发射峰归属于Dy3+的 4H21/2→6H15/2跃迁,440nm处的发射峰归属于Eu2+的4f65d1→4f7跃迁.结合XRD分析,我们认为两种发光中心是由于样品中包含两种晶型,且两种晶型的发射中心不同,六方晶系的发射中心以Dy3+为主,而单斜晶系的发射中心以Eu2+为主.1200℃还原1h后强制冷却所得样品的颗粒较细,一次粒径大约为0.5μm.     

Syntheses and crystal structures of two N-substituted thio-imidazoles

The syntheses and structures of two N-substituted thio-imidazoles are reported. The geometrical parameters for both compounds, including essentially planar imidazole rings, are consistent with previous structural studies of related materials. The only possible non-van der Waals’ interactions influencing the molecular packing are weak C–H⋯π bonds. Crystal data: C₁₂H₁₄N₂S (N-methyl-N′-2-phenylethyl-imidazol-2-thione), M _r = 218.31, monoclinic, P2₁/n, (No. 14), a = 6.8441(2) ?, b = 12.9960(4) ?, c = 13.4703(4) ?, β = 97.7729(16)°, V = 1187.12(6) ?³, Z = 4, R(F) = 0.039, wR(F ²) = 0.104. C₁₉H₂₀N₂S (N,N′-bis((s)-1-phenylethyl)imidazol-2-thione), M _r = 308.43, orthorhombic, P2₁2₁2₁ (No. 19), a = 10.4060(3) ?, b = 10.6712(3) ?, c = 14.8932(3) ?, V = 1653.81(7) ?³, Z = 4, R(F) = 0.038, wR(F ²) = 0.085.     

Generation and intermolecular trapping of a cage-annulated cycloalkylidenecarbene

Base-promoted reaction of 11-methylenepentacyclo[5.4.0.0^2,6.0^3,10.0^{5, 9}]undecan-8-one (5) with diethyl diazomethylphosphonate when performed in the presence of excess cyclohexene, resulted in the formation of the corresponding cycloalkylidenecarbene, 6, which subsequently was trapped in situ to afford 8-methylene-11-(7-bicyclo[4.1.0]heptylidene)pentacyclo-[5.4.0.0^{2, 6}.0^{3, 10}.0^{5, 9}]undecane (7, obtained in 44% yield as a mixture of exo, endo isomers). Subsequent reaction of 7 with dichlorocarbene (generated under phase transfer catalytic conditions) produced the corresponding mono- and di-:CCl₂ adducts [i.e., 8 (64% yield) and 9 (5% yield), respectively]. The structure of 9 was established unequivocally via application of single crystal X-ray analysis: Triclinic, P1¯, a = 6.276(2), b = 8.700(2), c = 18.550(3) Å, = 76.52(3), = 87.59(3), = 70.88(4)° Z = 2; D _calc 1.486 g cm^–3.     

Zn1-x HfxO的电子结构和光学性质的第一性原理计算

基于第一性原理密度泛函理论,计算分析了Zn1-xHfxO(x=0,0.0312,0.0417,0.0625和0.1250)体系的晶格结构、电子结构,Mulliken电荷布居和光学性质.计算结果表明,随着Hf掺杂摩尔百分比的增大,晶体体积膨胀,费米能级进入导带,其附近的导带部分主要由杂质原子Hf的5d态贡献,Hf-O离子键成分作用凸显,故Hf的掺杂引入施主能级进而形成n型ZnO材料的可能性较大.且通过比较吸收谱、反射谱和折射谱,发现适量掺入Hf原子可使ZnO体系在高能区的透过率增加,能量损失谱出现红移.这些性质均与实验中Hf掺杂有类似结果,由此可知适量掺杂Hf的ZnO体系有望在制备光电子器件等领域发挥作用.     

The Crystal and Molecular Structure of tert‐Butoxycarbonyl ‐ α‐aminoisobutyryl ‐ isoleucyl ‐methylester

The crystal structure of the synthetic peptide Boc — Aib — Ile ‐ OMe (C₁₆ H₃ 0 N₂ O₅ ) has been determined from three‐dimensional X — ray diffraction data. The peptide crystallizes in triclinic space group P1 with a = 9.570(9), b = 10.261(7), c = 10.610(2) Å , α = 101.9(0), β = 91.7(0), γ = 98.6(0)° V = 1006.1(12) ų, Z = 2, D_calc = 1.09 Mg m^‐3. The structure was solved by direct methods and refined by full‐matrix least‐squares method to an R value of 0.072 (λ = 1.5418Å). The conformation of Aib residue in molecule A is αL and in molecule B is αR. The Ile residue in molecule A adopts folded conformation, while in molecule B it is in the extended region. The peptide units are trans and show significant deviations from planarity.     

Synthesis and crystal structure of 4,5-dibromo[2.1.1]triblattene

Reaction of 4-bromopentacyclo[7.3.0.0^2,7.0^3,11.0^6,10]dodec-11-ene (1) with Br₂—CCl₄ afforded 4,4,5-tribromopentacyclo[7.3.0.0^2,7.0^3,11.0^6,10]dodecane (2) in 89–94% yield. Subsequent treatment of 2 with KOt-Bu-t-BuOH resulted in competitive elimination of the elements of HBr and of Br₂ with concomitant formation of 4,5-dibromopentacyclo[7.3.0.0^2,7.0^3,11.0^6,10]dodec-11-ene (3, 76%) and 1 (17%), respectively. The structure of 3 was established unequivocally via application of X-ray crystallographic methods. Crystal data for 3: monoclinic, C2/c, a = 9.895(1), b = 9.0963(7), c = 12.471(1) Å, = 106.875(8)°, z = 4.     

The Crystal and Molecular Structure of 11,12‐dibromo‐ 7,8—benzo‐1,5‐di(p—tolylsulphonyl)‐1,5‐diazacyclononan

The crystal structure of the title compound, C₂₅H₂₆Br₂N₂O₄S₂ was determined by single crystal X‐ray diffraction technique. The crystals are monoclinic, space group C 2/c, with a=20.7142(2) Å b=11.7910(2) Å, c= 10.6735(3) Å, β=98.549(2)°, V=2577.94(9) ų, Z=4. The structure was solved by direct methods and refined by least‐squares methods to a final R=0.046 for 1866 observed reflections with I>2sigma(I). The title compound, displays disordered geometry around the C1 atom located almost on twofold axis. The nine‐membered heterocylic ring is close to the half‐chair conformation. The dihedral angle between phenyl rings is 34.2(1)°.