The magnetic behavior of Co atoms on the surface and in the interior of the noble metals Au,Ag and Cu

The magnetism of Co atoms in the interior and on the surface of the noble metals has been studied by means of the anomalous Hall effect. On the surface of all three noble metals Co possesses a magnetic moment even at lowest studied coverages of 0.02 atomic layers. Ferromagnetic ordering appears at Co thicknesses of about one atomic layer. Co as a bulk impurity is non-magnetic in Cu whereas it is magnetic in Ag.     

铒离子注入绝缘体上Si的射程分布研究

利用离子注入掺杂技术设计、制作半导体集成器件时,了解离子注入半导体材料的射程分布和横向离散规律等是很重要的.用200—500 keV能量的铒(Er)离子注入SOI(silicon-on-insulator,绝缘体上的硅)样品中,利用卢瑟福背散射(RBS)技术研究了剂量为2×1015cm-2的Er离子注入SOI的平均投影射程Rp和射程离散△Rp,把测出的实验值和SRIM软件得到的理论计算值进行了比较,发现平均投影射程Rp的实验值跟理论计算值符合较好,射程离散△Rp的实验值和理论计算值差别大一些.     

Three-dimensional range distribution of 400 KeV Nd ions implanted into Si

Abstract

The 400 keV Nd ions were implanted into Si at a variety of tilt angles from 7° to 75°. The range distributions were accurately measured by the TOF-SIMS (Time-of-Flight secondary ion mass spectrometry) method. The results show that the measured range profiles can be represented by Pearson I type distributions which are in the same category as predicted by TRIM (TRansport of Ions in Matter). The first four statistical moments of the Nd-depth distribution, namely range, longitudinal straggling, skewness, and kurtosis, were obtained from the fitted profiles, and compared with the corresponding TRIM calculated values. Results show that the experimentally obtained range profiles are obviously deeper and broader than TRIM'95 (version 95.2) predictions, but very good agreements were obtained between the measured values and TRIM'98 (version 98.10) calculation. The longitudinal and lateral range stragglings for normal incidence were deduced from the angular dependence of the measured range distributions. Based on the range distributions for different angle implantation, the three-dimensional range distribution was reconstructed, and the lateral range straggling was obtained from the three-dimensional distribution and compared with both the predicted TRIM values and the deduced value.     

Perturbed angular distribution of recoil implanted F19-nuclei in a nickel-environment

Magnetic hyperfine fields acting on F¹⁹ in a Nickel lattice have been investigated. Time-dependent spin rotation has been observed following the excitation and recoil implantation with a pulsed proton beam using the reaction F¹⁹(p,p′)F¹⁹?. Two hyperfine fields were detected at 290 °K:H _hf ⁽¹⁾ =+17.6 ± 0.5 kGH _hf ⁽²⁾ =+91 ± 3 kG. The variation of the effective fields with the external polarizing field was studied. The mean life of the 197 keV level has been remeasured as τ=128±2 nsec.     

Superconductivity in α-phase alloys of Cu,Ag and Au

We have found f.c.c. alloys rich in noble metals to be superconducting. From these data, extrapo lated values for the transition temperatures of Au, Ag and Cu can be obtained.     

Recoil energies of fragments photoproduced in Cu,Ag and Au

The recoil energies of²⁴Na produced in Cu, Ag and Au and of a series of fragments produced in Cu irradiated with 800 MeV bremsstrahlung have been measured in directions forward, backward and perpendicular to the beam using the thick target-thick catcher method. Comparison of the measured values with theoretical calculations indicates that²⁴Na is produced through fission in Ag and Au and that fission is competing with spallation even in Cu.     

Virtual bound states of Pd in Cu,Ag and Au and of Pt in Ag

The positions and widths of the virtual bound states of 5 and 10% Pd in Cu, Ag and Au and of 5 and 10% Pt in Ag have been measured by XPS. The spin—orbit splitting of the Pt state in Ag is reduced from the theoretical value, but comparable to the spectroscopic atomic value. The host lattice d-band structure is perturbed in the alloys.     

Nuclear spin-lattice relaxation of dilute Mn in Cu,Ag, and Au

We have developed a new method of determining nuclear spinlattice relaxation times of dilute impurity nuclei in non-magnetic host metals. Direct measurement of these extremely rapid relaxation times has hitherto been difficult. The present method is based on fast pulsed heating of a sample containing oriented radioactive nuclei and is applicable to a wide range of impurity-host combinations and over a large range of applied magnetic fields. Results are presented for extremely dilute Mn in noble metal hosts.     

Interpretation of perturbed angular distribution results for19F implanted into diamond

Perturbed Angular Distribution measurements have been made on natural diamond using recoil implanted fluorine ions as probes. Two distinct lattice sites for fluorine in diamond were found. Site identifications prompted by theoretical cluster calculations are presented. The PAD data are well described by a texture theory, though the origin of the texture effects is presently not known.     

Electric field gradients in dilute alloys of Cu,Ag and Au

In this paper we present perturbed angular correlation (PAC) measurements on¹⁰⁰Rh and¹¹¹Cd in a number of dilute alloys of Cu, Ag and Au. We discuss the electric field gradient (EFG) values derived from these and other experiments in the framework of a theory of the EFG at nearest neighbours of point defects in metals, essentially based on the screening of a point charge in a free electron gas. We include in our discussion the EFG due to a neighbour monovacancy for a number of fcc metals.     

Transport in fullerene device coupled to Cu,Ag and Au electrodes

We present an ab initio approach of the electronic transport through a single molecular junction based on C₂₀ fullerene. The electronic properties of a single molecular junction constrained within two semi-infinite metallic electrodes are largely affected by the choice of electrode material. The two-probe device formed by the mechanically control break technique has been modelled with three distinct electrode materials from group IB of the periodic table, namely copper, silver and gold. The quantum characteristics of these mechanically stable devices are obtained by utilising first-principle density functional theory together with non-equilibrium green function method. We evaluate the quantum characteristics, namely density of states, transmission spectrum, energy levels, current and conductance, which essentially determine the behaviour of a molecule linked to different electrodes. Our investigation concludes that copper, silver and gold electrode configuration in conjunction with C₂₀ fullerene behaves as metallic, non-metallic and semi-metallic in nature, respectively.     

Mass distribution of fission fragments in the19F+197Au reaction

Mass distributions of fission fragments have been measured for the reaction of¹⁹F on¹⁹⁷Au as a function of scattering angle. The mean fragment mass is dependent on the scattering angle, the asymmetry increasing with increasing projectile energy.     

Refined equations of state for Cu,Ag, and Au in the sub-TPa region

The Equations of State for Cu, Ag, and Au in the sub-TPa region are constraint by correlated fits of all the thermo-physical data at ambient pressure and by theoretical estimates of the intrinsic anharmonicities. A hierarchy in the parameters provides a robust fitting procedure with typical accuracies of the finally calculated pressures of probably better than 1% at temperatures to the melting curve and pressures into the TPa-region.     

II. XPS study of 3d-metal ions dissolved in noble metals

Valence and core level spectra ofAgMn,AuFe,AuCo,AuNi,CuFe,CuCo andCuNi will be reported. Clearly defined virtual bound states (vbs) can only be detected in the spin fluctuating systemsAuNi andCuNi. An increase in the density of states near the Fermi energy, in the region of the flats-p band of the host metal is observed in the other magnetic alloys. There are indications that a large hybridization between the impurity and the host metald-electrons exist. The impurity core levels show satellites. They can originate from the emission from real isolated impurities and from many body effects.     

Interaction of 12.7 GeV He ions with U, Pb, Au and Ag targets

The processes of production of fragments Z 8 in the interactions of 12.7 GeV ⁴He with U, Pb, Au and Ag have been analyzed using the polycarbonate track detector Makrofol. A sandwich technique was used which enables direct evidence for multiple fragment emission by a single nucleus. The decay channels ending with one, two or more (three, four) fragments were detected. A classification scheme based on the multiplicity of heavy fragments M_H (Z> 20) was used in order to identify events belonging to the different reaction channels. Cross sections, excitation energies and multiplicities of intermediate mass fragments (8 Z 20) have been evaluated for various reaction mechanisms. The experimental features of the fragmentation process have been analyzed as a function of the target mass.     

Bonding in Cu,Ag, and Au clusters: relativistic effects,trends, and surprises

Electronic structure and bonding in anionic coinage metal clusters are investigated via density-functional calculations, focusing on an extensive set of isomers of Cu(-)(7), Ag(-)(7), and Au(-)(7). While the ground states of Cu(-)(7) and Ag(-)(7) are three dimensional (3D), that of Au(-)(7) is planar, separated from the optimal 3D isomer by 0.5 eV. The simulated thermally weighted photoabsorption spectrum of Au(-)(7) is dominated by planar structures, and it agrees well with the measured one. The propensity of Au(-)(N) clusters to favor planar structures (with N as large as 13) is correlated with strong hybridization of the atomic 5d and 6s orbitals due to relativistic effects.     

Photoelectric energy distributions associated with interconduction band transitions in Cu,Ag and Au

The photoelectric energy distributions associated with direct transitions between the bulk conduction bands in the three noble metals have been calculated using the interconduction band structures determined in analyses of the piezo-optical response. The good overall agreement between the calculated and observed line shapes strongly corroborates the piezo-optical determinations. However, small discrepancies for initial energies around the Fermi energy are noted which we believe can not be attributed to direct transitions in the bulk.     

Large Z1-range effect for Eu,Yb and Au ions implanted in amorphized silicon

The Z₁-range oscillation amplitude is investigated as a function of energy for Eu, Yb and Au ions implanted in amorphous Si at energies from 10 to 390 keV. The obtained experimental results are not reproduced by the recent theoretical predictions of Burenkov and collaborators, showing large discrepancies for energies lower than 50 keV.