利用高分辨X射线衍射仪表征GaN薄膜的结构特性

使用高分辨X射线衍射法（HRXRD）对金属有机物化学气相沉积（MOCVD）外延生长GaN薄膜进行微结构表征．首先采用绝对测量法精确测试了GaN薄膜的晶格常数,由此获得该GaN薄膜的应变与弛豫的信息．采用面内掠入射（IP—GID）法测定了GaN薄膜的位错密度以及位错扭转角．     

Growth Defects in Cubic KTa1-xNbxO3 Crystal

Potassium tantalate niobate （KTa1-xNbxO3, KTN） crystals with different dimensions and quality situations were grown by Czochralski method. Crystal growth process and morphology properties of KTN are presented in this paper. It was found that some defects, such as bubble, inclusion, crack, dislocation etc., can all appear if the crystal is grown in an improper condition. The character and formation mechanism of such defects in macro growth are discussed. We consider that the CO2, which was not released absolutely during the sintering process and dissolved in the melt, led to bubbles. The composition of the inclusion caused by high pulling and rotation rates is KTN polycrystalline. The crack and dislocation in KTN crystal mainly come from improper temperature field. Etching and high-resolution X-ray diffraction （HRXRD） experiment results indicate that the central area is the defects concentrated.     

高度c轴取向的ZnO膜的低温水热法制备

在预先镀有ZnO纳米层的(0001)蓝宝石衬底上利用低温水热法制备出ZnO薄膜。SEM和XRD显示此ZnO膜是由六棱柱状阵列构成的，基于蓝宝石衬底生长，具有高度的c轴择优取向，且(0004)摇摆曲线的FWHM达到1.8°。并发现了在水热溶液中加入一定量六次甲基四胺可以调节六棱柱状ZnO尺寸比例。     

Study of Defect and Large Thermal Strain Nature in Organic Crystal of Rubidium Hydrogen Phthalate

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KDP晶体台阶生长动力学的激光干涉实验研究

采用迈克尔逊干涉技术,通过测量KDP晶体生长的法向速率和台阶斜率来研究其台阶生长的动力学系数、台阶自由能、溶质在边界层内的扩散特征以及激发晶体生长台阶的位错活性.实验表明, KDP中不同活性位错的台阶动力学系数差异较大,例如高活性和低活性台阶动力学系数分别为10.3×10-2和5.21×10-2 cm/s,位错源在晶体表面的形状、面积的变化,以及Burgers矢量的变化是造成晶体生长动力学测量数据重复性差的主要原因.     

Studies on the Properties of ZnO Crystal Plane Grown by the Innovated Hydrothermal Method

ZnO single crystals were grown by the innovated hydrothermal method. The crystal surfaces were polished, and then studied by atom force microscope （AFM） and wet-chemical etching （WCE）. It was found that the Zn polar plane was smoother than O polar plane under the same polishing conditions. The etch pit density of Zn polar plane is 4.3×10^3 cm^-2, which is consistent with the previous report, while the density of etch pit of O polar plane is more than 103cm^-2. After annealing treatment, the density of etch pit of Zn plane reduces to 5.8×102 cm^2 and is superior to the current report. This investigation reveals that the high quality ZnO single crystals with fine Zn polar plane can be obtained by the innovated hydrothermal method.     

Selective Growth of GaN on Slope Cone-shaped Patterned Sapphire Substrate

Cone-shaped patterned sapphire substrate was prepared by inductively coupled plasma etching and GaN nucleation layer was grown on it by metal-organic chemical vapor deposition.A selective growth of GaN nucleation layer was found on the slope of the cone-shaped patterned sapphire substrat,and the distribution morphology of GaN had significantly changed after it was recrystallized.GaN selective growth and redistribution were analyzed by investigating the distribution of crystallographic planes on the cone surface and the atom array of specific planes at atom level.     

Rapid Growth of Pentaerythritol Crystal

Pentaerythritol(PET) crystal has been grown rapidly from the solution with sulfuric acid as the additive. The growth rate of PET crystal in prismatic shape exceeds 1.5 mm/day and crystallization size is 55×55×50 mm3. X-ray diffraction analysis was used to confirm the structure integrity. The diffraction efficiency of rapid-grown crystal was characterized as effective as that of normal growth.     

Synergetic effects during sputter-assisted depth profiling: Growth-dominated topography development on InP and a model of the atomic mechanism

Growth-dominated extreme topography development on ionbombarded wafers of InP is reported and is explained in terms of the micro region model presented in summary form. This model postulates the existence of an ion-bombardment-produced ensemble of crystallites and non-crystalline aggregations of atoms (composed of the substrate material, of dopant and of oxygen from the native oxide layer) where the majority of InP micro regions is so small (nanometer dimensions) that most interstitials created in collision events between bombarding ions and atoms of the micro region can reach an interfacial boundary rather than recombine with a vacancy from the same or another collision event. These atoms are then transported via interfacial boundaries and over the surface to screw dislocations where crystal stubs proceed to grow until the damage rate by ion bombardment overtakes the growth rate. Ion-bombardment-induced compressive stresses favour diffusion towards the surface. Temperature transients within micro regions assist both interfacial diffusion and damage repair. The topography is a result of competition between growth and sputtering. Different growth rates cause different topographies. The development of an extreme topography can be suppressed by oxygen flooding of the sputtered surface, by simultaneous electron beam scanning, as well as by Cs⁺ ion bombardment.     

Experimental Evaluation of Procedures for Heat Capacity Measurement by Differential Scanning Calorimetry

Experimental evaluation of the procedures adopted for heat capacity measurements employing differential scanning calorimetry (DSC) has been carried out by taking nickel and sapphire as test samples. Among the various methodologies reported in literature, the absolute dual step method was chosen for this purpose due to its simplicity and minimum number of measurements required. By proper temperature and heat flux calibration employing indium as reference, it was possible to obtain the calibration factor independent of temperature. This was ascertained by analysing other pure metals namely Sn, Zn, Cd, and Pb and determining their melting temperatures and heats of melting. Various operator- and sample-dependent parameters such as heating rate, sample mass, the structure of the sample, reproducibility and repeatability in the measurements were investigated. Heat capacities of both nickel and sapphire have been determined using the above method. Further, the heat capacity of nickel has also been determined using the widely employed three-step method taking sapphire as the heat flux calibration standard. Both methods yielded the comparable heat capacity values for nickel. Based on the parameters investigated and their influence, it could be concluded that reasonably precise and accurate heat capacity measurements are possible with DSC. One advantage of this method is the elimination of a separate calibration run using a reference material of known heat capacity. This revised version was published online in August 2006 with corrections to the Cover Date.     

仲胺配合物的合成、晶体结构及与DNA作用的研究

合成了一种新颖三齿配体(L),N-(4-甲基苯)-N’-(2-(4-甲基苯氨基)乙基)乙烷-1,2-二胺,并制备了它的四种过渡金属配合物,结合元素分析、红外、1 HNMR和摩尔电导,确定配合物的组成为[ML(NO3)2](M=CuⅡ,CoⅡ,NiⅡ,ZnⅡ).用X-ray单晶衍射解析了Zn-L和Ni-L的单晶结构.通过紫外、荧光光谱研究了这四种金属配合物与小牛胸腺DNA的相互作用,根据结果推断出配合物与DNA的作用方式可能均为静电结合.Cu-L,Co-L,Ni-L,Zn-L与DNA的结合常数分别为:3.34×104,7.65×103,2.15×104,2.40× 104.     

溶胶处理对硅灰石表面性质的影响

本工作用锡和锌两种溶胶对硅灰石进行表面处理。用酸碱测定、X-射线光电子能谱(XPS)、傅里叶变换红外光谱(FT-IR)、粒度分析、比表面测定和扫描电子显微分析(SEM)等方法研究了溶胶处理对硅灰石表面化学性质和物理性质的影响情况。结果表明经过溶胶处理,锡或锌是以氧化物的形式包覆在硅灰石的表面,使得硅灰石的表面组成、形貌和酸碱性都发生了变化。     

EFFECT OF STRUCTURE ON DEFECT FORMATION IN CRYSTAL OF LITHIUM BORIC OXIDE (LBO)

<正> The effect of structure on the defective formation in non-linear optical crystal of lithium boric oxide(LBO)was studied by X-ray topography.Only a few dislocations with the density less than 50/cm2 occur in the specimen cut far from the seed.Most inclusive formed in the late growth stage show a regular orthorhombic shape with a definite orientation,which are due to the negative crystal growth happened further in the inclusioned melt.The grown-in dislocation takes nearly the screw character with the Burgers vector b almost all in the low index directions,however,the inclusion-induced dislocation is distributed much closely in a network parallel only to the plane of(010)and also takes the screw type with b all in the lowest diretions of this plane.The high movability of lithium ions in open structure and the loosely atmic packings on certain planes were taken into account for the defect formation in addition to for some other crystal properties.     

Growth and Spectroscopic Properties of Nd3＋：Sr3Gd2（BO3）4 Crystal

<正>This paper reports the growth,X-ray diffraction and spectroscopy of Nd~(3+):Sr_3Gd_2(BO_3)_4 crystal.A Nd~(3+):Sr_3Gd_2(BO_3)_4 crystal with dimensions ofφ20×45 mm~3 has been grown by the Czochralski method.Nd~(3+):Sr_3Gd_2(BO_3)_4 crystal belongs to the orthorhombic system,space group Pnma(D_(2h))with a=0.7401,b=1.604 and c=0.8755 nm.The absorption and emission spectra of Nd~(3+):Sr_3Gd_2(BO_3)_4 were investigated.The absorption cross sectionσ_a is 3.11×10~(-20)cm~2 at 808 nm. The absorption transition at 808 nm has an FWHM of 14 nm.The luminescence lifetimeτ_f is 51.7 us.The emission cross sectionσ_e at 1064 nm wavelength is 1.09×10~(-19)cm~2.     

Surface-interface investigations of an ultrathin pulsed laser deposited NiO/ZnO bilayer structure

We hereby report detailed structural and morphological studies for an ultrathin NiO/ZnO bilayer structure grown on sapphire (001) substrate using pulsed laser deposition technique. The combined X-ray reflectivity (XRR) and grazing incidence X-ray fluorescence (GIXRF) studies revealed formation of a low-density defective ZnO interfacial layer of thickness ~32 Å at the ZnO/sapphire interface prior to growth of main ZnO layer. Our results further indicate that the variation of electron density across the NiO/ZnO bilayer structure is smooth and we do not observe presence of any interface layer between them. X-ray diffraction measurements show that deposited ZnO layer is epitaxial in nature whereas NiO is highly oriented along (100) direction. The angle dependent X-ray absorption near edge fine structure (XANES) measurements at Ni–K edge has been utilized to determine depth-resolved oxidation state of Ni and the results have been correlated with the depth-resolved electron density of NiO layer. The method described here offers nondestructive determination of the microstructural parameters as well as depth-resolved mapping of oxidation state of a thin film-based heterojunction device. It extends several advantages over destructive methods which are abundantly reported in literature.     

新型石墨烯基LED器件：从生长机理到器件特性

III族氮化物因具有禁带宽度大、击穿电压高、电子饱和漂移速度大、稳定性高等优异特性而广泛应用在发光二极管(LED)、激光器以及高频器件中。目前III族氮化物薄膜通常是异质外延生长在蓝宝石衬底表面,但是由于蓝宝石与III族氮化物之间存在较大的晶格失配与热失配,使得外延生长的III族氮化物内部存在较大的应力与较高的位错密度,严重影响了器件性能;与此同时,蓝宝石衬底热导率差,限制了其在大功率器件方面的应用。近年来研究发现,石墨烯作为外延生长缓冲层,能够有效解决蓝宝石衬底与外延III族氮化物薄膜之间由于晶格失配和热失配导致的高应力与高位错密度等问题,进而获得了高品质薄膜,并提升了器件的性能。本文综述了石墨烯/蓝宝石衬底上III族氮化物生长与LED器件构筑的研究现状,着重介绍了本课题组提出的一种新型外延衬底—石墨烯/蓝宝石衬底的特点,阐明了III族氮化物在该新型衬底上的生长机理,总结了其对III族氮化物质量提升的作用,并对其发展前景进行了展望。     

Bi12SiO20晶体下降法生长及Pt包裹缺陷研究

采用改进的坩埚下降法成功生长了硅酸铋Bi12SiO20(BSO)单晶,探讨了工艺参数对晶体生长的影响.用电子探针方法研究了硅酸铋晶体中的铂金包裹体及其相关缺陷.铂金包裹物的尺寸一般在30μm～5mm之间.包裹物经常导致晶体开裂,使成品率大为降低.铂坩埚中的杂质是导致坩埚受侵蚀的主要原因,通过延长铂坩埚熔炼时间和适当降低晶体生长炉温,可明显减少铂包裹体及其相关缺陷.通过优化生长工艺,获得了尺寸为50mm×35mm×35mm的优质BSO单晶.     

Growth and Optical Properties of Sr_6YbSc(BO_3)_6 Crystal

1INTRODUCTION As is well known,the Yb3 ion has some advan-tages in comparison with Nd3 as laser active ion,for it has only two manifolds,i.e.,the ground2F7/2state and the excited2F5/2state.There is no excited state absorption reducing effective laser cross-section,no concentration quenching,no up-conversion,and three or four times longer emission lifetime than Nd3 ion.Yb3 ion exhibits a strong and broad ab-sorption band at ca.970nm and can be easily pumped with InGaAs diode lasers.The …     

Expression, Purification, Crystallization and Molecular Replacement Studies of TorI, an Inhibition Protein of Tor System

TorI, a Tor system inhibitor acting through protein-protein interaction with the TorR response regulator, is an excisionase that interacts with the integrase and DNA during prophage excision. It has been crystallized by the vapor-diffusion method using polyethylene glycol 3350 as a precipitant at pH 8.5. The X-ray diffraction data sets from the TorI crystal was collected at a resolution of 2.1 , using a synchrotron source. The crystal belongs to primitive monoclinic lattice with cell parameters of 46.210 × 53.992 × 73.561     

Li doped and undoped ZnO nanocrystalline thin films: a comparative study of structural and optical properties

Thin films of ZnO were grown by the sol–gel method using spin-coating technique on (0001) sapphire substrates. The effect of doping after annealing on the structural and optical properties has been investigated by means of X-ray diffraction (XRD), cathodoluminescence (CL) spectrum, scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films that were dried at 623 K and then post annealed at 873 K showed (0002) as the predominant orientation. Two emission bands have been observed from CL spectrum. Lithium doped film shows shift in the near band edge UltraViolet emission peak and suppressed defect level emission peak in the visible range. SEM analysis of the films exhibits many spherical shaped nanoparticles. Roughness of the films determined using atomic force microscopy.