含氢气氛下区熔硅单晶中缺陷的研究

利用化学腐蚀和X射线投影貌相方法研究了含氢气氛下区熔无位错硅单晶中的缺陷,发现异常腐蚀现象、缺陷密度与气氛中氢含量紧密相关,观测了纯氢气氛下无位错硅单晶退火后的缺陷,找到了貌相与蚀象的对应关系,还观察了二次退火效应,最后,综合所观测到的结果,讨论了氢在硅单晶中的集聚、沉淀和位错环列的发射、运动及交互作用。 关键词：     

Defect samarium ions and electromotive-force generation in SmS

A model explaining electromotive-force generation in SmS under heating in the absence of external temperature gradients is considered. An analysis of data on the density of SmS single crystals with compositional deviations from stoichiometry in the homogeneity range suggests that excess samarium ions occupy vacancies on the sulfur sublattice. Possible concentrations of defect samarium ions are determined (up to 2.8×10²¹ cm^?3). The temperature interval within which electromotive force appears in various SmS samples (440–640 K) and the critical conduction-electron concentrations at which the generation sets in [(6.0–8.5)×10¹⁹ cm^?3] are calculated. An expression permitting estimation of the magnitude of the observed effect is proosed.     

Hydrogen incorporation behaviour and radiation damage in proton bombarded InP single crystals

Abstract

In proton bombarded InP single crystals the incorporation behaviour of different hydrogen isotopes is studied in relation to implantation induced radiation defects. Investigations of the fluence dependence (D = 10¹⁶-10¹⁸ cm^?2), of the depth profile and of the annealing behaviour (T _an = 300–1000 K) of hydrogen incorporation and of damage density indicate that only a small fraction of the implanted hydrogen is chemically bonded to host lattice atoms. These bonded hydrogen atoms saturate dangling bonds at defect sites.     

单晶YSZ的Xe+辐照损伤的电子显微分析

不同注量200keV Xe+ 注入YSZ单晶样品的电子显微分析结果表明,随着辐照注量的增加,缺陷簇的密度增大,在1×1015~1×1016cm-2Xe+注量,缺陷簇密度迅速增大,形成间隙型位错环;当Xe+注量增大到1×1017cm-2,缺陷簇密度的增加变得缓慢,并且有直径为2～4nm的Xe气泡析出。选区电子衍射花样表明YSZ样品没有产生非晶化转变。在Xe+辐照的离位率高达约350dpa的情况下,YSZ晶体没有非晶化,其原因主要是由于注入的Xe+以气泡形式析出。     

重离子辐照SiO2通过能量损失产生发光色心的研究

通过红外光谱和荧光发射光谱分别对600 keV、4 MeV和5 MeV Kr离子辐照的SiO2进行发光特性的研究。在低能量辐照体系中,简单色心(F2色心)的形成在损伤过程中占据主导地位,其主要诱发蓝光发射带;在高能离子辐照条件下,离子径迹上的能量密度较大,因此缺陷浓度的增大产生了一些缺陷团簇和离子径迹,形成了复杂的色心(F2+和F3+色心等)并诱发了强烈的绿光发射带和红光发射带。该实验结果与能量损失过程中统一热峰理论模型(一个综合的基于电子能损与核能损的非弹性碰撞模型和弹性碰撞模型)的模拟结果能够很好地吻合,表明在keV～MeV能区上存在电子能损过程与核能损过程的协同效应。     

Enhancement of F-centre colouration during plastic deformation of alkali halides

Stimulated growth of F-centres was observed by irradiating alkali-halide single crystals during uniaxial deformation at controlled rates. Quantitative monitoring of the phenomena was performed for pure KCl at L.N.T. as well as in the range from R.T. to 106°C. Distinct forms for the kinetics of growth were obtained in the two regions. A correlation was also established between the growth of excess colouration and the evolution of stress, in the higher temperature range. The data on the kinetics, stress dependence and temperature dependence suggest that the production of excess F-centres arises from the radiolysis of vacancy-producing debris (possibly, dislocation dipoles) that are also effective agents of hardening. The process is limited by thermally activated annealing, with an activation energy appropriate for free-vacancy migrations. It is suggested that the limiting reaction is a recombination of the excess negative-ion vacancies with an antimorph defect, contained in a complementary type of dislocation debris.     

硅单晶氢致缺陷分布的实验研究

利用X射线形貌术方法研究了含氢硅单晶中氢致缺陷的分布。将原生晶棒从内部切开,观察到在切口暴露表面附近,热处理后产生的氢致缺陷的密度与尺寸与内部未暴露部分相同,而不同于薄片退火的情况,对此结果作了简要的讨论。 关键词：     

四方相BaTiO_3:Ce及Mn离子注入的BaTiO_3:Ce的拉曼散射的研究

四方相ＢａＴｉＯ３：Ｃｅ及Ｍｎ离子注入的ＢａＴｉＯ３：Ｃｅ的拉曼散射的研究刘玉龙朱恪张昊朱镛（中科院物理研究所北京１０００８０）赵金涛（张掖师范高等专科学校物理系甘肃张掖７３４０００）萧季驹（香港城市大学物理及材料科学系香港九龙）ＲａｍａｎＳｐｅｃ...     

Kinetics of high-temperature precipitation in dislocation-free silicon single crystals

The defect structure of dislocation-free silicon single crystals has been calculated using the approximate solution of the Fokker-Planck partial differential equations. It has been demonstrated that the precipitation starts to occur near the crystallization front due to the disappearance of excess intrinsic point defects on sinks whose role is played by oxygen and carbon impurities.     

Near-damage threshold femtosecond laser irradiation of dielectric surfaces: desorbed ion kinetics and defect dynamics

We study the modification of fluoride single crystals after irradiation with femtosecond laser pulses for a range of incident intensities from well below to near damage threshold. The behavior of the desorbed positive ion yields, as analyzed by time-of-flight mass spectrometry, is corroborated with temporal characteristics of radiation induced defects in fluorides. The ion yield evolution upon repetitive irradiation (incubation) exhibits the typical reduction of the multi-shot damage threshold with increasing number of pulses. The experimental data point towards an exponential growth of the transient defect density as the origin of this effect. On the other hand, measurements of the time decay of transient defect fluorescence inside the transparent sample show that the defect lifetime may be even longer than tens of milliseconds. To account for the incubation and the increase of the radiation-target coupling efficiency, a model relating the defect lifetime to a pulse-by-pulse accumulation of transient defects is presented, based on a calculation of the free electron density.     

单晶YSZ的Xe+辐照损伤的电子显微分析

 不同注量200keV Xe⁺ 注入YSZ单晶样品的电子显微分析结果表明，随着辐照注量的增加，缺陷簇的密度增大，在1×10¹⁵~1×10¹⁶cm^-2Xe⁺注量，缺陷簇密度迅速增大，形成间隙型位错环；当Xe⁺注量增大到1×10¹⁷cm^-2，缺陷簇密度的增加变得缓慢，并且有直径为2～4nm的Xe气泡析出。选区电子衍射花样表明YSZ样品没有产生非晶化转变。在Xe⁺辐照的离位率高达约350dpa的情况下，YSZ晶体没有非晶化，其原因主要是由于注入的Xe⁺以气泡形式析出。     

Displacement field induced by a vacancy in nickel and some implications for the solubility of hydrogen

The displacement field induced by a vacancy in nickel and its possible implications for the hydrogen solubility in the interstitial sites is investigated up to 1100 K. The displacement field is extracted from our previous atomistic-scale density functional theory calculations and is compared with continuous isotropic models with and without image forces due to the distribution of the defects. This procedure put in forward the contribution of the elastic anisotropy and the vacancy concentration on the elastic displacement field. Then, we calculate the dilatation of the interstitial sites due to the presence of the defect and the local hydrostatic stress acting on them. This local hydrostatic stress modifies the hydrogen solubility in the interstitial sites. Elastic distortions contribute to reduce the local solubility inside the vacancy core and the opposite out of it. Finally, we extract the elastic contribution of the trapping energy of hydrogen in the displacement field of the vacancy. We find that the elastic energy is significant only for the closest interstitial sites of the defect core and limits the attractive electronic contribution to the trapping energy. In addition, we show that the elastic anisotropy and the vacancy concentration have moderate effects on the local solubility in the displacement field close to the defect core.     

ESR of chromium(+1) in sulfur-deprived zinc sulfide

ZnS : Cr single crystals were grown under conditions which favored the formation of sulfur vacancies. In some cases a vacancy paired with a Cr⁺ ion at a nearest-neighbor Zn site to form a complex defect. Identification of the defect was made by use of ESR and heat treatments of the crystals.     

The Role of Oxygen Containing Impurities in Defects Formation in Cesium Halide Crystals

The dependence of defect formation efficiency in CsI single crystals both on the type of oxygen containing impurities and the value of the absorbed irradiation dose was studied. Correlative results were obtained under investigation by methods of ionic thermocurrent (ITC), thermostimulated exoemission (TSEE), electrical conductivity and optical spectroscopy. The peculiarities of defect formation in γ-irradiated CsI-CO₃(SO₄, OH) and X-irradiated CsI-OH single crystals are discussed.     

Study of ferromagnetism in Co-doped rutile powders and float-zone grown single crystals

Co-doped rutile samples in the form of both powders and bulk single crystals have been studied with particular emphasis on the dependence of their magnetic, compositional and structural properties upon the type of atmosphere used during their preparation. Both powders and single crystals were characterized using X-ray diffractometry and vibrating sample magnetometry, while the crystals were also studied using the X-ray Laue technique, scanning electron microscopy and energy dispersive X-ray analysis. The results indicate that an oxygen deficient environment during the preparation of Co-doped TiO₂ powders is crucial for the observation of room temperature ferromagnetism, while preparation in oxygen rich conditions destroys the ferromagnetism due to the formation of the paramagnetic second phase CoTiO₃. Floating zone growth of crystals under oxygen also led to the formation of material containing second phase CoTiO₃ that was paramagnetic at room temperature, while crystals grown under argon were ferromagnetic and contained Co-rich inclusions.     

Multi-sample loading technique for comparative physical property measurements in the diamond-anvil cell

ABSTRACT

We present a method to perform improved measurements of the effects of chemical variability on physical properties of single-crystal samples in the diamond-anvil cell by employing a multi-sample approach. By customizing the sizes and shapes of the samples using a focused ion beam machine the simultaneous loading of relatively large crystals into a single sample chamber becomes feasible. To illustrate the potential of this approach, elastic properties of four single crystals of ringwoodite with different chemical compositions have been measured at high pressure. Our results suggest that the multi-sample approach allows for the quantification of small effects of chemical variations, such as iron and hydrogen incorporation, on physical properties. Furthermore, we discuss the possibility of using the multi-sample approach to load several crystals with different crystallographic orientations of the same material into one sample chamber in order to map out the direction dependence of anisotropic physical properties.     

锂改性点缺陷石墨烯储氢性能的第一性原理研究

本研究采用基于密度泛函理论的第一性原理方法计算了两种石墨烯点缺陷处原子的分波态密度(PDOS),能带结构和差分电荷密度等,研究了锂掺杂对两种本征石墨烯缺陷C-Bridge和C7557电子结构的改性,以及对其储氢能力的影响.结果表明Li原子能够稳定的掺杂且不易形成团簇,并且Li原子掺杂石墨烯能够对石墨烯能带中的狄拉克锥和费米面起到调控作用,增强了缺陷石墨烯的电子活性.本征缺陷石墨烯的储氢能力较弱,缺陷石墨烯的储氢能力可以通过Li掺杂来改善.     

Properties of the band gap of two-dimensional plasma photonic crystals

Employing the finite-difference time-domain (FDTD) method, we study the filtering properties of twodimensional plasma photonic crystals. We show that the transmission spectra of the defects in the plasma photonic crystals vary with change in the defect location, its radius, the plasma frequency, and the frequency of electron–ion collisions in the plasma. We demonstrate that the two-dimensional defect structure from the viewpoint of its frequency characteristic (such as an adjustable filter characteristic) is similar to the one-dimensional structure. We find that by changing the parameters of the defect location, the plasma frequency, and the frequency of electron–ion collisions in the plasma, one can obtain different ranges of transmission peaks at different frequencies, which fully reflects the adjustable filter characteristics of the structure. Therefore, the two-dimensional structure is more important than the one-dimensional structure, and it can be used to produce actual microwave devices.     

Dependence of the structure of ion-modified NiTi single crystal layers on the orientation of irradiated surface

The composition and structure of Si layers implanted into titanium nickelide single crystals with different orientations relative to the ion beam propagation direction have been studied using Auger electron spectroscopy and transmission electron microscopy. The role of the “soft” [111]_B2 and “hard” [001]_B2 NiTi orientations in the formation of the structure of ion-modified surface layer, as well as the defect structure of the surface layers of the single crystals, has been revealed. Orientation effects of selective sputtering and channeling of ions, which control the composition and thickness of the oxide and amorphous layers being formed, ion and impurity penetration depth, as well as the concentration profile of the Ni distribution over the surface, have been detected.     

Effect of the current density on the volume expansion of the deposited thin films of aluminum during porous oxide formation

The effect of the anodic current density, temperature and concentration of the oxalic acid on the volume expansion of porous alumina films formed from 1.8 μm thick aluminum films has been investigated. The volume expansion of the aluminum during oxidation was determined by the step height between the aluminum surface and the porous alumina surface at the edge of the anodized region, which was measured with a mechanical profiler with computer signal processing. Experiments showed, that the volume expansion factor as well as the cell dimensions is proportional to the anodizing voltage. The dependence of the volume expansion factor (k) on the anodizing voltage (U) has the linear nature. The volume expansion factor in the 4% solution of oxalic acid can be defined by the following equation: k=1.092+0.007U. It was established, that the dependence of the logarithm of the ion current density on the inverse volume expansion factor of porous alumina has the linear nature.