共查询到20条相似文献,搜索用时 15 毫秒
1.
J. Geerk 《辐射效应与固体损伤》2013,168(1-4):35-36
This overview outlines some basic properties of defects in insulators and describes experimental techniques by which these defects may be characterized. Then the production of defects by various types of particle irradiation is discussed. Finally some discussion is presented of the potential device application of defective crystals, including tunable colour centre lasers, miniaturised optical circuitry and neutron dosimetry. 相似文献
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In this article,the Sm-doping single crystals Ca_(1-x)Sm_xFe_2As_2(x = 0 ~0.2) were prepared by the Ca As flux method,and followed by a rapid quenching treatment after the high temperature growth.The samples were characterized by structural,resistive,and magnetic measurements.The successful Sm-substitution was revealed by the reduction of the lattice parameter c,due to the smaller ionic radius of Sm~(3+)than Ca~(2+).Superconductivity was observed in all samples with onset T_c varying from 27 K to 44 K upon Sm-doping.The coexistence of a collapsed phase transition and the superconducting transition was found for the lower Sm-doping samples.Zero resistivity and substantial superconducting volume fraction only happen in higher Sm-doping crystals with the nominal x 0.10.The doping dependences of the c-axis length and onset T_c were summarized.The high-T_c observed in these quenched crystals may be attributed to simultaneous tuning of electron carriers doping and strain effect caused by lattice reduction of Sm-substitution. 相似文献
4.
Thin GaN films are grown on (001) single-crystal GaAs substrates processed in an atmosphere of active nitrogen radicals. Auger
electron spectroscopy is applied to take the depth profiles of the basic chemical elements that enter into the composition
of the epitaxial GaN films and single-crystal GaAs substrates. It is found that the surface composition of the GaN films is
characterized by considerable nonstoichiometry (the excess nitrogen achieves ≈9%), which is caused by the presence of atomic
nitrogen in the discharge chamber. With a high-resolution X-ray diffraction method, the structural perfection of the epitaxial
layers is investigated. It is shown that low-temperature annealing (at temperatures below 700°C) is responsible for the formation
of cubic GaN films on the (001) surface of cubic GaAs, whereas higher temperature annealing results in the growth of the hexagonal
films. 相似文献
5.
Using a wax-polishing-technique and evaporated lead counter-electrodes tunneljunctions on single crystal niobium are fabricated. Crystal surfaces normal to [100], [110] and [111] are investigated. No anisotropy is found in the tunneling curves within a precision of 1%. However, the evidence of these tunneling experiments is not sufficient, to exclude any gap anisotropy with the same certainty. 相似文献
6.
Using a wax-polishing-technique and evaporated lead counter-electrodes tunneljunctions on single crystal niobium are fabricated. Crystal surfaces normal to [100], [110] and [111] are investigated. No anisotropy is found in the tunneling curves within a precision of 1%. However, the evidence of these tunneling experiments is not sufficient, to exclude any gap anisotropy with the same certainty. 相似文献
7.
Sonier JE Poon KF Luke GM Kyriakou P Miller RI Liang R Wiebe CR Fournier P Greene RL 《Physical review letters》2003,91(14):147002
We report muon-spin rotation and relaxation (muSR) measurements on single crystals of the electron-doped high-T(c) superconductor Pr2-xCexCuO4. In a zero external magnetic field, superconductivity is found to coexist with dilute Cu spins that are static on the muSR time scale. In an applied field, we observe a mu(+)-Knight shift that is primarily due to the magnetic moment induced on the Pr ions. Below the superconducting transition temperature T(c), an additional source of local magnetic field appears throughout the volume of the sample. This finding is shown to be consistent with field-induced antiferromagnetic ordering of the Cu spins. Measurements of the temperature dependence of the in-plane magnetic penetration depth lambda(ab) in the vortex state are also presented. 相似文献
8.
V. E. Yurasova S. S. Elovikov E. Yu. Zykova 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2007,1(3):328-341
Results obtained in studying the sputtering of single crystals of hexagonal, rhombohedral, and cubic boron nitride modifications by computer simulations are reported. Data on sputtering the (0001) face of BN in two graphite-like modifications and the (111) face of BN crystals with a cubic lattice are presented. The energy and angular dependences of the sputtering yields and spatial and energy distributions of sputtered particles are considered for the cases of normal and oblique ion incidence. Specific features of the anisotropy of spatial distributions of sputtered particles and mechanisms of their formations are analyzed. 相似文献
9.
The (SN)x valence band structure, for polycrystalline films as well as for single crystal samples, has been studied using He I and He II resonance radiation. In angle-resolved photoemission energy distributions from single crystals, structure in the spectra is selectively enhanced offering a possibility of assigning the photoemission as originating from particular regions of the Brillouin Zone. The observed onset of photoemission 0.2 eV below the Fermi edge is discussed. 相似文献
10.
氮化铌(NbN)纳米线是超导纳米线单光子探测器(SNSPD)常用的光敏材料,其光学性质是影响SNSPD性能的关键因素.本文结合实验数据和仿真结果,系统研究了多种NbN超导纳米线探测器器件结构的光学特性,表征了以下四种器件结构下的反射光谱以及透射光谱:1)双面热氧化硅衬底背面对光结构;2)双面SiN硅衬底背面对光结构;3)硅衬底上以金层+SiN缓冲层为反射镜的正面对光结构;4)以分布式布拉格反射镜(DBR)为衬底的正面对光结构.并在上述四种器件结构基础上,生长了不同厚度的NbN薄膜,观察不同厚度NbN薄膜的吸收效率.经分析,发现在不同器件结构下的最佳NbN厚度与光吸收率的关系如下:双面热氧化硅衬底上的NbN层在1606 nm处最大吸收率为91.7%,其余结构在最佳NbN厚度条件下吸收率都能达到99%以上.其中双面SiN的硅衬底结构中最大吸收率为99.3%, Au+SiN为99.8%, DBR为99.9%.最后,将DBR器件实测结果与仿真结果进行了差异性分析.这些结果对高效率SNSPD设计与研制具有指导意义. 相似文献
11.
Planar waveguides in neodymium-doped calcium niobium gallium garnet crystals produced by proton implantation
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In this work, the fabrication and optical properties of a planar waveguide in a neodymium-doped calcium niobium gallium garnet(Nd:CNGG) crystal are reported. The waveguide is produced by proton(H~+) implantation at 480 ke V and a fluence of 1.0×10~(17) ions/cm~2. The prism-coupling measurement is performed to obtain the dark mode of the waveguide at a wavelength of 632.8nm. The reflectivity calculation method(RCM) is used to reconstruct the refractive index profile. The finite-difference beam propagation method(FD-BPM) is employed to calculate the guided mode profile of the waveguide.The stopping and range of ions in matter 2010(SRIM 2010) code is used to simulate the damage profile induced by the ion implantation. The experimental and theoretical results indicate that the waveguide can confine the light propagation. 相似文献
12.
Weili Zhang Yiben XiaJianhua Ju Linjun WangZhijun Fang Minglong Zhang 《Solid State Communications》2003,126(3):163-166
The electrical conductivity of nitride carbon (DLC: N) films has been studied. It is found that the electrical conductivity of the deposited films increases slowly with increasing nitrogen content, however, it decreases after the nitrogen content in the film reaches a certain value of 12.8 at%. Thermal treatment results show that the electrical conductivity of the lowly nitrogen doped DLC film increases rapidly, while that of the heavily doped film decreases after annealing at 300 °C for 30 min. Raman and XPS spectra results show that when the nitrogen content in the films reaches a certain value, there appears nonconductive phases. Therefore the electrical conductivity of the heavily doped films decreases. FTIR spectra analysis results show that the nitrogen atom as an impurity center undergoes an ‘activation’ process during the thermal treatment, which leads to the increase of the electrical conductivity. Therefore, the nitrogen in these two kinds of films has different effects on the electrical conductivity. 相似文献
13.
The transverse electro-optic(EO)modulation system is built based on cubic boron nitride(cBN)single crystals unintentionally doped and synthesized at a high pressure and high temperature.The photoelectric output of the system includes two parts that can be measured respectively and the value of elements in the linear EO tensor of the cBN crystal can be obtained.This method does not need to measure the absolute light intensity.All of the surfaces of the tiny cBN crystals whose hardness is next to the hardest diamonds are{111}planes.The rectangular parallelepiped cBN samples are obtained by cleaving along{110}planes and subsequently grinding and polishing{112}planes of the tiny octahedral cBN flakes.Three identical non-zero elements of the EO tensor of the cBN crystal are measured via two sample configurations,and the measured results are very close,about 3.68 and 3.95 pm/V,respectively,which are larger than the linear EO coefficients of the general III-V compounds. 相似文献
14.
《中国科学:物理学 力学 天文学(英文版)》2017,(2)
By using a hydrothermal ion-exchange method, we have successfully grown superconducting crystals of Li OHFe S with Tcof about 2.8 K. Being different from the sister sample(Li1-xFex)OHFe Se, the energy dispersion spectrum analysis on Li OHFe S shows that the Fe/S ratio is very close to 1:1, suggesting an almost charge neutrality and less electron doping in the Fe S planes of the system. Comparing with the non superconducting Li OHFe S crystal, each peak of the X-ray diffraction pattern of the superconducting crystal splits into two, and the diffraction peaks locating at lower reflection angles are consistent with that of non-superconducting ones. The rest set of diffraction peaks with higher reflection angles is corresponding to the superconducting phase, suggesting that the superconducting phase may has a shrunk c-axis lattice constant. Magnetization measurements indicate that the magnetic shielding due to superconductivity can be quite high under a weak magnetic field. The resistivity measurements under various magnetic fields show that the upper critical field is quite low, which is similar to the tetragonal Fe S superconductor. 相似文献
15.
J.P. Zhao Z.Y. Chen T. Yano T. Ooie M. Yoneda J. Sakakibara 《Applied Physics A: Materials Science & Processing》2001,73(1):97-101
Carbon nitride films with high nitrogen content were prepared by reactive pulsed-laser deposition at nitrogen partial pressures
varying from 0.1 to 20.0 Torr. It was found that the nitrogen content in the films first increases with increase of the nitrogen
pressure, reaches a maximum of 46 at. % at 5.0 Torr, and then decreases to 37 at. % at 20.0 Torr. The almost pure carbon nitride
films were systematically characterized by using X-ray photoelectron spectroscopy (XPS) concerning the core-level and valence-band
structures. Some fingerprint information, which shows the role of nitrogen in controlling the electronic structure of carbon
nitride films, was found based on the XPS studies. With enhancing the nitrogen incorporation, both the binding energy and
the peak intensity of the core-level and the valence-band spectra vary systematically as a function of nitrogen content in
the films.
Received: 26 June 2000 / Accepted: 26 June 2000 / Published online: 20 September 2000 相似文献
16.
《Journal of Molecular Spectroscopy》1990,143(1):169-179
State-averaged (SA) complete-active-space self-consistent-field (CASSCF) multireference configuration-interaction (MRCI) calculations are reported for the singlet and triplet states of NbN below about 20 000 cm−1 and the quintet states below about 30 000 cm−1. The theoretical spectroscopic constants for the four lowest triplet states, X3Δ, A3Σ−, B3Φ, and C3Π, are in excellent agreement with experiment. The calculations predict the ordering of states in the singlet manifold to be a1Δ, b1Σ+, c1Γ, d1Σ+, and e1Π. These states have all been experimentally observed, except for the d1Σ+ state near 13 000 cm−1. The lowest quintet state, 5Π, is predicted to lie above 17 000 cm−1. The calculations confirm the experimental conjecture, based on hyperfine splittings, that the X3Δ state is of predominantly 4dδ15s1 character. Although the NbN molecule is very ionic, the ground-state dipole moment of 3.68 D is only moderately large, because of the polarization of the 5s electron away from nitrogen atom. Electronic transition moments are computed for all of the dipole-allowed transitions in the singlet and triplet manifolds. The radiative lifetimes for the v′ = 0 level are computed to be 37 ns, 35 ns, 1 μs, and 64 ns for the B3Φ, C3Π, d1Σ+, and e1Π states, respectively. For small v′, the largest Einstein coefficients all involve transitions with v′ = v″, because the transitions in NbN are nearly vertical. We constrast our results for NbN with similar calculations for the isoelectronic ZrO molecule. The considerable differences between the spectroscopy of ZrO and that of NbN are a result of the greater stability of the d orbitals for Nb, and the fact that Nb has a 4dn+15s1 ground state, whereas Zr has a 4dn5s2 ground state. 相似文献
17.
Nitrogen ion implantation in single wall carbon nanotubes 总被引:1,自引:0,他引:1
F. Xu M. Minniti C. Giallombardo A. Cupolillo P. Barone A. Oliva L. Papagno 《Surface science》2007,601(13):2819-2822
We report an X-ray photoemission and electron energy loss study on 3 keV ion implantation in single wall carbon nanotubes. Our results show that nitrogen atoms can bind to carbon in tetrahedral sp3, defects related pyridine-like, and triangular sp2 configurations and such bondings are stable for annealing up to 650 K. Heating at higher temperatures results in preferential substitutional nitrogen doping. This technique opens a new channel for controlled doping in carbon nanotubes for device applications. 相似文献
18.
J. V. Pinto M. M. Cruz R. C. da Silva N. Franco A. Casaca E. Alves M. Godinho 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(3):253-260
The magnetic and electrical properties of Co-implanted
single crystalline TiO2 rutile are presented. For fluences of
the order of 1017 cm-2 and implantation energy of 150
keV the maximum atomic concentration of cobalt is 13 at% at a depth
of 65 nm from the surface. The as implanted single crystals exhibit
superparamagnetic behaviour attributed to the formation of nanosized
cobalt clusters. After annealing at 1073 K an anisotropic
ferromagnetic behaviour emerges with the easy magnetization axis
lying in the (001) plane of rutile. The ferromagnetic behaviour is
associated with oriented cobalt aggregates. Electrical conductivity
of the implanted samples annealed in vacuum also exhibits
anisotropic behaviour at low temperatures, but no magnetoresistive
effects were detected. 相似文献
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