La1-x／2Pr1-x／2SrxCuO4的电输运性质和超导电性

La1-x/2Pr1-x/2SrxCuOy(LPSCO)多晶样品采用传统的固相反应法制备.X射线衍射表明:LPSCO具有典型的空穴搀杂的T-214相的结构.磁化率测量显示:Sr搀杂在0.05≤x≤0.30范围内具有超导转变;Tc随x的增大呈抛物线形式变化,且在x=0.18时达到最大值28K.电阻的测量显示:随搀杂量的增大,系统呈现从绝缘到半导体,最后到金属的导电行为的变化;在欠掺杂区,正常态电阻温度关系符合ρ(T)=ρ0 αT-ClnT;而在过掺杂区,对数项消失.本文从替代所引起的晶体结构和载流子特性变化解释了Sr掺杂样品的电输运行为和超导特性.     

Ruderman-Kittel-Kasuya-Yosida-like ferromagnetism in MnxGe1-x

The nature and origin of ferromagnetism in magnetic semiconductors is investigated by means of highly precise electronic and magnetic property calculations on MnxGe1-x as a function of the location of Mn sites in a large supercell. Surprisingly, the coupling is not always ferromagnetic (FM), even for large Mn-Mn distances. The exchange interaction between Mn ions oscillates as a function of the distance between them and obeys the Ruderman-Kittel-Kasuya-Yosida analytic formula. The estimated Curie temperature is in good agreement with recent experiments, and the estimated effective magnetic moment is about 1.7mu(B)/Mn, in excellent agreement with the experimental values, (1.4-1.9)mu(B)/Mn.     

钛酸铅镧Pb_(1-x)La_xTi_(1-x/4)O_3纳米晶的拉曼光谱研究

本文在２８８Ｋ和３７８Ｋ测定了不同Ｌａ含量Ｐｂ１－ｘＬａｘＴｉ１－ｘ／４Ｏ３纳米晶的拉曼光谱,同时在室温条件下测定了不同晶粒尺寸的Ｐｂ０．９Ｌａ０．１Ｔｉ０．９７５Ｏ３纳米晶的拉曼光谱,研究了Ｌａ含量和晶粒尺寸对各声子模频率的影响规律,讨论了影响峰形、峰位和峰宽的因素。     

高组份Al值的AlxGa1-x As和AlxGa1-x As/GaAs/AlxGa1-xAs/GaAs多层结构的MOCVD生长

用自制常压MOCVD系统,在半绝缘GaAs衬底上生长高Al组份Al_xGa_1-xAs（其x值达0.83）,和Al_xGa_1-xAs/GaAs/Al_xGa_1-xAs/GaAs多层结构,表面镜面光亮。生长层厚度从几十到十几μm可控,测试表明外延层晶格结构完整,x值调节范围宽,非有意掺杂低,高纯GaAs外延层载流子浓度n_300K=1.7×10¹⁵cm^-3,n_77K=1.4×10¹⁵cm^-3,迁移率μ_300K=5900cmcm²/V.S,μ_77K=55500cm²/V.S。用电子探针,俄歇能谱仪测不出非有意掺杂的杂质,各层间界面清晰平直。 对GaAs,AlGaAs生长层表面缺陷,衬底偏角生长温度及其它生长条件也进行了初步探讨。     

Domain wall formation in NixFe1-x

In terms of a multiscale approach based on the Landau-Ginzburg expansion and on ab initio parameters evaluated by means of the fully relativistic screened Korringa-Kohn-Rostoker method, the width of domain walls is evaluated for the whole range of concentration in NixFe1-x. It is found that domain-wall formation occurs only for x<20% and x>55%; i.e., in the neighborhood of the structural phase transition from bcc to fcc, NixFe1-x first tends to form single domains before the actual range of concentrations of this phase transition is reached. The calculated domain-wall widths are found to be in reasonably good agreement with available experimental data.     

Zn1-xMgxO和Zn1-xMnxO薄膜的制备及其发光性能

采用溶胶-凝胶技术,在Si(110)衬底上制备了Mg、Mn掺杂外延生长的Zn_1-xMg_xO和Zn_1-xMn_xO薄膜,通过XRD、AFM、PL等考察不同杂质浓度对薄膜结晶质量和发光性能的影响。结果表明:Zn_1-xMg_xO和Zn_1-xMn_xO薄膜均具有较高的T_c(002)结构系数和较为光滑、平整的表面形貌。掺杂使得薄膜的紫外发光峰向短波方向移动至365 nm左右,同时Zn_1-xMn_xO薄膜的室温可见光发射得以有效地钝化,使其近带边紫外光发射与深能级可见光发射比例高达56,极大地提高了薄膜紫外发光性能。并对掺杂薄膜紫外发光蓝移和Zn_1-xMn_xO薄膜室温可见光发射的猝灭机理进行了深入探讨,得出掺杂组分为Zn_0.85Mg_0.15O、Zn_0.97Mn_0.03O时,薄膜具有最强的紫外光发射性能。     

Optical properties of TiN1-x single crystals

The reflectance spectra of TiN_1–x single crystals were measured at room temperature. The chemical composition of the crystals was varied between TiN_1–0.00 and TiN_1–0.43. The experimental data are analyzed on the basis of a Lorentz-Drude model in order to determine the influence of nitrogen vacancies on the electrical conductivity, on the carrier concentration, and on the collision time.     

Electronic structure of Ag x Au1-x

The fully relativistic version of the Korringa-Kohn-Rostoker-Coherent Potential Approximation (KKR-CPA) method has been used to study the electronic structure of the alloy system Ag _x Au_1-x forx=0.20, 0.40, 0.60 and 0.80. The results of these calculations are discussed in terms of densities of states and Bloch spectral functions and are compared with experimental data.     

ZnSxSe1-x单晶的霍尔迁移率

用Vah der Pauw法在77～300K温度范围内测试了n-ZnSxSe1-x(x=0.15)单晶的霍尔迁移率,共最大值为2150cm2/V·s迁移率随温度变化的实验结果与载流子散射的几种理论模型曲线相比较,得出在120K附近为界,在高温区中极化的光学声子散射限定迁移率;在低温区中光学声子散射和离化本征受主散射的混合模型或离化本征受主散射限定迁移率。认为离化本征受主是一次电离的Zn空位。     

准零维CdSxSe1-x微晶材料的光学性质

通过玻璃基体中CdSxSc1-x微晶的光谱测量,看到了CdSxSe1-x微晶的带隙随尺寸变小而变宽,表现出明显的量子尺寸效应。同时,详细观测了玻璃基体对微晶的压力影响,结果表明这种材料中的压力是不可忽略的。     

SmCo_(1-x)Ir_xAsO体系的磁性和输运性质

采用固相反应法,制备出一系列SmCo1-xIrxAsO(x=0.05,0.1,0.15,0.2,0.25,0.3)多晶样品。XRD测试结果表明所有样品均具有ZrCuSiAs型四方结构,随着掺杂量的增加,晶格参数a变大,c变小。在x≥0.25时发现小部分杂相峰IrAs2,说明SmCo1-xIrxAsO体系单相样品较难制得。磁性测量结果表明,SmCo1-xIrxAsO在高温区表现出顺磁性。外场为10Oe时,掺杂量为0.05的样品随着温度的降低,依次在60K和45K附近出现铁磁转变和反铁磁转变,在低温区ZFC与FC曲线分离,出现明显的不可逆性。随着外磁场的增加,不可逆性受到抑制,铁磁转变温度TC向高温方向移动。增加掺杂量,样品铁磁反铁磁转变温度几乎不变,表明Ir掺杂对样品磁性没有影响。M-H曲线表明,温度T30K时,所有掺杂样品随着磁场的增加,均出现反铁磁(AFM)-铁磁(FM)的磁性转变,且转变磁场随温度的升高而减小。T=50K时,这种变磁性转变消失,样品表现出软铁磁特性。     

Mg_xZn_(1-x)O粉体的制备及性能表征

MgxZn1-xO材料是一种新型的光电功能材料,近年来受到人们的广泛关注.文章采用Sol-Gel法制备了MgxZn1-xO粉体,研究Mg含量对MgxZn1-xO结构和发光性能的影响,结果表明在x从0到1的整个区间中MgxZn1-xO样品存在六方纤锌矿与面心立方两种结构,当x＜0.2时为六方纤锌矿结构,x＞0.8时为面心立方结构,在两者之间为其混合结构;光谱分析表明不同组分的MgxZn1-xO样品均具有紫外和可见发射特性,紫外发射峰位于370～384 nm,可见发射峰位于468 nm附近;粉体的平均粒径在100 nm左右.     

COxCu1-x复相纳米线阵列的制备及其磁性的研究

利用电化学沉积方法在同一种富Co2 溶液Co2 /Cu2 =10:1中.利用不同的沉积电位成功地制备了一系列不同成分(x=0.38-0.87)和复合相结构的CoxCu1-x纳米线阵列.发现随着纳米线中Cu含量的变化,CoxCu1-x纳米线的复相结构随之发生规律的变化,最终导致纳米线的磁性也随之规律的变化.随着纳米线中Cu含量的不断增加,一部分Cu与Co形成面心立方结构(fcc)的CoCu固溶体,减弱了磁晶各向异性与形状各向异性的竞争,从而提高样品的方形度;一部分Cu以fcc结构的Cu单质的形式存在于纳米线中,并随着Cu颗粒大小的不同分别起到破坏磁晶各向异性和钉扎畴壁的作用,从而增加纳米线的方形度和矫顽力.对比不同成分的样品,发现CoxCu1-x纳米线的方形度和矫顽力的最大值分别出现在Co75Cu25和Co60Cu40中,并且由于其特殊的复相结构致使它们的值要好于相同直径的单相结构的结果.