Electronic structure of bivalent copper off-center complexes in SrF<Subscript>2</Subscript> crystals from data of EPR and ENDOR spectroscopy

The electronic structure of bivalent copper off-center complexes in SrF₂ crystals is calculated from experimental data obtained earlier by electron paramagnetic resonance (EPR) and electron-nuclear double resonance (ENDOR) spectroscopy. The electronic structure parameters characterizing the unpaired-electron density in the vicinity of the nucleus of a copper impurity ion are determined, and the parameters of covalent bonds between an impurity copper ion and three groups of the fluorine ions nearest to this impurity are calculated. It is demonstrated that states of the ground electron configuration of the bivalent copper impurity complex involve an admixture of excited electron configurations due to electron transfer from the ligand to 4s and 4p unfilled shells of the copper ion.     

Conductivity of copper phthalocyanine-polystyrene composite films in the presence of adsorbed oxygen

The electrical conductivity and adsorption-resistive response to nitrogen dioxide of composite films containing copper phthalocyanine nanoparticles dispersed into the polystyrene matrix are investigated experimentally. The results are analyzed using the two-level model of hopping conductivity. The contributions to the conductivity from intrinsic and impurity localization centers are singled out, and the concentrations of the localization centers in copper phthalocyanines free of impurities as well as the electron localization radii in impurity and intrinsic states are determined.     

Theoretical analysis of impurity precipitation in nanopores in crystals. II: Kinetics of impurity cluster growth in pores

The kinetics of the formation of impurity clusters in subsurface nanopores in crystals is studied theoretically. A physical model of precipitation of the impurity phase in nanopores in a sample with sinks of various types is developed. This model forms the basis for the calculation of the annealing kinetics of copper containing subsurface pores and cobalt impurity atoms. The optimal annealing conditions are determined in which cobalt atoms diffuse predominantly into pores and form impurity clusters in them.     

火焰原子吸收法测定工业硅中的铜

采用火焰原子吸收法测定工业硅中杂质元素铜,操作简便、快速,结果准确。     

铜合金中铁和锰的火焰原子吸收分光光度测定法

本文建立了以火焰原子吸收分光光度计同时测定铜合金中铁，锰两元素的方法，该法以硝盐混酸溶解试样，在标准系列中加入基体铜以扣除背景影响，其中杂质元素，如锌，铝，铅，镍，锑，铋，锡等，对测定铁和锰元素均无影响，方法简便快速。准确度符合要求，结果令人满意。     

Theoretical analysis of the formation of impurity precipitates in nanocavities. I. thermodynamic analysis

The formation of the impurity phase in materials containing nanopores is investigated theoretically. The formation of impurity clusters on the inner surface of pores is studied using the thermodynamic approach. The most advantageous states of metal impurities in silicon are determined, and comparison with available experimental data is carried out. The possibility of the formation of cobalt nanoclusters in subsurface cavities in copper is substantiated theoretically.     

铜沉淀对直拉硅单晶中洁净区形成的影响

研究普通热处理和快速热处理工艺下直拉单晶硅中过渡族金属铜杂质对洁净区生成的影响. 通过腐蚀和光学显微镜研究发现,常规高-低-高三步洁净区生成热处理样品中, 第一步高温热处理前对样品铜沾污,样品中没有洁净区生成,高密度的铜沉淀布满了样品整个截面. 而第二步、第三步热处理过程中引入铜杂质不影响洁净区的生成. 研究表明,高温热处理过程中生成的铜沉淀不能溶解是导致洁净区不能形成的最主要原因. 另外,由于不同温度下热处理,导致引入铜杂质的平衡浓度不同,会在一定程度上影响洁净区的厚度. 对于快速热处理样品,可以得到相似的结果. 关键词： 直拉单晶硅 铜沉淀 洁净区     

Theory of impurity scattering: Interstitial impurities

A framework for studying impurity scattering in dilute, non-magnetic, metal alloys can be developed from a knowledge of the exact electronic eigenstates of a single impurity in an otherwise perfect lattice of muffin tin potentials. Such an approach has been developed for systems in which the impurity occupies a substitutional site of the lattice, as will be discussed by Coleridge, Lee, Harris, and other speakers of this conference. In this paper, motivated by recent experimental studies of Dingle temperature anisotropies induced by hydrogen impurities in copper, we will discuss the analogous treatment of scattering by interstitial impurities. In contrast to a substitutional impurity, an interstitial impurity introduces an additional scattering site into the lattice. Whereas the substitutional impurity wavefunctions can be described in terms of the same structure factors as can the Bloch wavefunctions for the pure host lattice, the interstitial impurity wavefunctions depend upon additional structure factors appropriate to the new scattering geometry. These additional structure factors appear in the transition matrix for impurity-induced scattering between Bloch states of the host lattice, and consequently in the weight factors involved in a partial wave analysis of the Dingle temperature anisotropies.This work was supported by the National Science Foundation through the Materials Research Laboratory at the University of Chicago.     

Point-contact spectroscopy of electron-phonon interaction in alloys

The point contact spectroscopy is used for the investigation of the electron-phonon interation in alloys. The possibilities offered by the method are studied for the case when the impurity electron mean free path is comparable with or much smaller than the point contact diameter. The changes of the electron-phonon interaction spectra of CuNi and CuFe alloys caused by those in impurity concentrations are studied and compared with the PC spectra of pure copper.     

Theory of impurity scattering: Interstitial impurities

A framework for studying impurity scattering in dilute, non-magnetic, metal alloys can be developed from a knowledge of the exact electronic eigenstates of a single impurity in an otherwise perfect lattice of muffin tin potentials. Such an approach has been developed for systems in which the impurity occupies a substitutional site of the lattice, as will be discussed by Coleridge, Lee, Harris, and other speakers of this conference. In this paper, motivated by recent experimental studies of Dingle temperature anisotropies induced by hydrogen impurities in copper, we will discuss the analogous treatment of scattering by interstitial impurities. In contrast to a substitutional impurity, an interstitial impurity introduces an additional scattering site into the lattice. Whereas the substitutional impurity wavefunctions can be described in terms of the same structure factors as can the Bloch wavefunctions for the pure host lattice, the interstitial impurity wavefunctions depend upon additional structure factors appropriate to the new scattering geometry. These additional structure factors appear in the transition matrix for impurity-induced scattering between Bloch states of the host lattice, and consequently in the weight factors involved in a partial wave analysis of the Dingle temperature anisotropies.     

Quadrupole effects in63Cu NMR spectroscopy of copper nanocrystals

Quadrupole effects in room-temperature continuous-wave (CW)⁶³Cu nuclear magnetic resonance (NMR) spectra, “π/2” pulse length shortening and amplitudes of two-pulse generated echoes were investigated on nanocrystalline copper powders produced by cryogenic melting and by ball milling techniques. Systematic measurements on the parent polycrystalline copper and on copper-based copper-palladium dilute alloys on the basis of the same experimental techniques were also made and the results were compared to that of the nanophase samples. Fractions of Cu nuclei contributing to the specific NMR responses and average field gradients coming from noncubic neighborhoods were estimated in all the investigated cases. The satellite and/or central component origins of NMR spectra of the samples are not a priori trivial even in the simplest case. Comparative analysis of CW and pulsed experiments allowed a surprising technological conclusion to be drawn by finding a smaller chemical impurity content inside the nanograins than the value characteristic of the entire sample. The measured decrease of the impurity concentration in the inner region of the copper nanoparticles is the consequence of the applied technologies: cryogenic melting and ball milling. These preparation methods cause grain-boundary segregation and result in a cleaner inside of copper nanoparticles.     

Local structure of bivalent copper centers in SrF2 crystals: An ENDOR spectroscopic study

Structural distortions of the SrF₂ crystal lattice near the bivalent copper impurity Jahn-Teller center are investigated by the ENDOR method (v=9.3 GHz, T=4.2 K). The approximate directions and the magnitudes of displacements of a Cu²⁺ impurity ion and its surrounding F^? ions are determined with respect to one of the anionic networks in the crystal matrix. The tensor components for the ligand hyperfine interaction (LHFI) with fluorine ions separated from the impurity by a distance R≤6.2 Å are obtained from the angular dependences of the location of the ENDOR resonance lines. It is found that the parameters of magnetic interactions between the impurity and these ligands contain the contributions determined by the covalence of bonds in the impurity complex and the polarization of electron shells of the ligands.     

Creep and diffusion parameters in submicrocrystalline metals

We have studied the creep of nickel and copper in a submicrocrystalline (SMC) state in a vacuum and in the presence of a diffusion contact with an impurity (Cu and Al, respectively). It is shown that a reduction of the resistance in the presence of a diffusion contact with an impurity is observed in the SMC materials in the temperature range 398 to 473 K. This range is 200 to 400 K lower than the corresponding range for coarse-grained material. It is shown that in this temperature interval the coefficients of grain boundary diffusion for copper in SMC nickel are 5 to 6 orders of magnitude larger than in the coarse-grained material. We propose that the reduction in the temperature for the manifestation of a creep activation effect in the presence of a diffusion contact with an impurity in SMC materials is caused by the increase in the diffusion permeability of the submicrocrystalline grain boundaries. Institute of Materials and Strength Physics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 77–82, March, 1998.     

Effect of copper on dislocation luminescence centers in silicon

The effect of copper on dislocation luminescence centers in silicon has been investigated using photoluminescence and transmission electron microscopy. It has been demonstrated that there exist two main mechanisms responsible for quenching of dislocation luminescence by the copper impurity. The first mechanism is dominant at high copper concentrations and associated with the decrease in the time of nonradiative recombination of nonequilibrium charge carriers due to the formation of copper precipitates in silicon. This leads to the quenching of the entire dislocation luminescence and the edge exciton luminescence. The second mechanism is associated with the interaction of individual copper atoms with deep dislocation centers D1/D2, which results in the passivation of the recombination activity of these centers. This mechanism takes place even at room temperature and is highly effective at low copper concentrations.     

Enthalpies and entropies of solution of first row transition metals in liquid copper

New experimental data for the enthalpies of solution of the first row transition metals in liquid copper are compared with the semiempirical predictions of Miedema et al. For solute metals from vanadium to nickel the enthalpies of solution also are compared with Gibbs energy data to yield excess entropies of solution. For Cr, Mn and Fe in liquid copper it is noted that the observed excess entropies in large measure may arise from the difference between the disordering entropy resulting from the destruction of the quasi-bound magnetic impurity states and the electronic entropy of the pure metal.     

Electroluminescence in (ZnS-ZnSe)Cu,H systems

A series of copper doped sulpho-selenide binary solid solutions, giving electroluminescent emission, right from green to red, has been prepared using ZnS and ZnSe in varying proportions. The behaviour of such polycrystalline samples was studied by usual methods in audio-frequency range. While the hydrogen ion acted as the main donor impurity in the entire series, its comparative study was made with chlorine coactivated samples. As regards the electroluminescent emission, while in the case of hydrogen coactivation, it is the transition from donor levels to the copper level that predominates, Cl-coactivation favoured direct transition from conduction band to same fundamental copper level. On frequency variation while the samples with ZnS-ZnSe composition showed marked peak shifts in their respective emission bands, no such effect could be observed in samples with single base.     

Model calculation of binding energies for multihole copper centers in germanium

Multihole binding energies of copper centers in germanium are calculated within a pseudoatom variational scheme in which a Heine-Abarenkov-type model potential is used as the impurity potential. Screening the hole-hole interaction by a position-dependent dielectric function is found to be crucial in understanding the observed multihole binding energies.     

银饰品中铜杂质含量的激光剥离—激光诱导击穿光谱定量分析

正交双波长双脉冲的激光剥离—激光诱导击穿光谱技术能够在较少样品烧蚀的前提下获得高的光谱分析灵敏度,因此该技术可以从根本上解决在单脉冲激光诱导击穿光谱技术中空间分辨本领与光谱分析灵敏度之间的矛盾。为了消除在该光谱技术中的实验参数对光谱信号强度及其定量分析结果的影响,实验研究了银饰品中杂质铜的光谱信号与银元素的光谱信号的相关性。研究结果表明：324.75 nm的铜原子辐射线与328.07 nm的银原子辐射线的强度呈很高的线性相关性,因此选择以银328.07 nm的光谱线作为内标线,采用内标法就可以消除双光束激光的空间几何配置以及剥离激光脉冲能量等实验参数对铜原子辐射信号的影响,从而可以采用正交双波长双脉冲激光剥离——激光诱导击穿光谱技术开展银饰品中铜杂质含量的定量分析。选择银328.07 nm的光谱线作为内标线,基于内标法建立了铜的校正曲线。当激光烧蚀坑洞直径约为17 μm时, 当前实验条件下银饰品中铜元素的检出限可以达到44 ppm。     

Local moment formation in the superconducting state of a doped Mott insulator

A microscopic theory is presented for the local moment formation near a nonmagnetic impurity or a copper defect in high-Tc superconductors. We use a renormalized mean-field theory of the t-J model for a doped Mott insulator and study the fully self-consistent, spatially unrestricted solutions of the d-wave superconducting (SC) state in both the spin S=0 and S=1/2 sectors. We find a transition from the singlet d-wave SC state to a spin doublet SC state when the renormalized exchange coupling exceeds a doping dependent critical value. The induced S=1/2 moment is staggered and localized around the impurity. It arises from the binding of an S=1/2 nodal quasiparticle to the impurity. The local density of states is calculated and connections to NMR and STM experiments are discussed.     

On the thermostability of electrical properties of <Emphasis Type="Italic">p</Emphasis>-Si<P,Ni> and <Emphasis Type="Italic">p</Emphasis>-Si<P,Cu>

Silicon samples with various nickel and copper concentrations were studied by the method of isochronal annealing. In so doing, the temperature of total decomposition of Ni and Cu centers was found to depend on the concentration of nickel and copper atoms in silicon overcompensated from the n-to the p-type. The decomposition temperatures of Ni and Cu centers increase with decreasing the distance between the impurity atoms. This effect is explained by the peculiarities in the distribution of the compensating-impurity atoms within the fluctuation regions being formed in silicon during doping. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 73–75, December, 2005.