[en] High resolution angle resolved core level and valence band photoelectron spectroscopy have been used to characterize the electronic structures of the B/Si(111)-(√3 x √3) surfaces. The results have been compared with theoretic calculations and other group III metals and Si terminated Si(111) surfaces that share the same type of surface reconstruction. We have observed a structure evolution from B-T₄ to B-S₅ and finally to Si- T₄ as deposited boron atoms diffuse into the substrate with increasing annealing temperature. The chemically shifted component appearing in the Si 2p core level spectrum is attributed to charge transfer from the top layer Si and Si adatoms to the sublayer B-S₅ atoms. For the Si/Si(111)-(√3 x √3) surface, a newly discovered chemically shifted component is associated with back bond formation between the Si adatoms and the underneath Si atoms. A new emission feature has been observed in the valence band spectra unique to the B/Si(111)-(√3 x √3) surface with B-S₅ configuration. Thin Ge layer growth on this structure has also been performed, and we found that no epitaxial growth could be achieved and the underneath structure was little disturbed

[en] The electronic structure of the diamond C(100)-(2 x 1)/(2 x 2) has been investigated by means of angle-resolved photoelectron spectroscopy for the first time. A surface-related shift has been observed in the C 1s core level spectrum. The surface-state band dispersion was measured along the symmetry axis Γ-J' in the surface Brillouin zone. For k_parallel = 0, there is a very pronounced surface state 1.5 eV below Fermi level E_F, and it disperses downwards with increasing k_parallel. Near the boundary of the surface Brillouin zone J', we find two states with binding energies of 1.9 and 2.4 eV with respect to E_F

[en] A Comment on the Letter by M. Prietsch et al., Phys. Rev. Lett. 60, 436 (1989) and by K. Stiles and A. Kahn, Phys. Rev. Lett. 60, 440 (1988)

[en] Presents the results of two of the tools implemented within this program, analyzing the strengths and possible areas for improvement identified in the behavior of the staff regarding the expectations of fixed safety culture, both for the revision of the program according to different parameters. The results obtained allow to raise the future lines of action of the programme and the initiatives to increase the culture of security personnel. (Author)

[en] The temperature effects on the cluster formation of column III and noble metals on GaAs(110) surfaces have been studied using surface sensitive photoelectron spectroscopy. At room temperature, these metal atoms tend to form three-dimensional islands, whereas at 80 K low temperature, a Stranski--Krastanov growth mode appears because of slow surface mobility. A simple model is established to estimate the cluster size and cluster distribution density. The electronic structures of the metal clusters have been simultaneously studied and correlated with the cluster size. This study shows the evolution from isolated atoms to bulk materials. The criteria of the establishment of the overlayer metallicity are discussed

[en] Highlights: • Cold metal transfer welding–brazing of titanium to copper was performed. • Increasing wire feed speed or groove angle will get satisfied Ti/Cu joint. • Increasing wire feed speed or groove angle will increase tensile load. • Ti/Cu CMT butt joint has dual characteristics of fusion welding and brazing. - Abstract: 3 mm Pure titanium TA2 was joined to 3 mm pure copper T2 by Cold Metal Transfer (CMT) welding–brazing process in the form of butt joint with a 1.2 mm diameter ERCuNiAl copper wire. The welding–brazing joint between Ti and Cu base metals is composed of Cu–Cu welding joint and Cu–Ti brazing joint. Cu–Cu welding joint can be formed between the Cu weld metal and the Cu groove surface, and the Cu–Ti brazing interface can be formed between Cu weld metal and Ti groove surface. The microstructure and the intermetallic compounds distribution were observed and analyzed in details. Interfacial reaction layers of brazing joint were composed of Ti₂Cu, TiCu and AlCu₂Ti. Furthermore, crystallization behavior of welding joint and bonding mechanism of brazing interfacial reaction were also discussed. The effects of wire feed speed and groove angle on the joint features and mechanical properties of the joints were investigated. Three different fracture modes were observed: at the Cu interface, the Ti interface, and the Cu heat affected zone (HAZ). The joints fractured at the Cu HAZ had higher tensile load than the others. The lower tensile load fractured at the Cu interface or Ti interface was attributed to the weaker bonding degree at the Cu interface or Ti interface

[en] Interfacial chemistry and Fermi-level movement for interfaces of noble metals on InP(110) prepared at room temperature (RT) and 80 K low temperature (LT) have been examined using photoelectron spectroscopy. An interfacial reaction is detected for all the RT interfaces as well as the LT Cu/InP interface, and the Fermi levels are pinned at 0.95 eV above the valence-band maximum (VBM). However, for LT Au/InP and Ag/InP, no reaction is seen, and the Fermi level is pinned around 0.7 eV above the VBM. The 0.7-eV pinning position at the near ideal LT Au/InP and Ag/InP interface is associated with metal induced gap states (MIGS), whereas, that at 0.95 eV is associated with defects formed during the interfacial reaction. These results indicate that both MIGS and defects can be important in the Fermi-level pinning and that the former is dominant only when the defect density is sufficiently low

[en] An optical spectral-hole burning technique has been used to study the nuclear quadrupole splitting in the ground state of ²⁴³Am³⁺ in LaCl₃. The observed splitting is consistent with Am³⁺ ions on an axially symmetric site. The nuclear quadrupole coupling constant P=-75±1 MHz for the ⁷F₀ ground state is obtained based on an effective operator Hamiltonian. The crystal-field antishielding effect dominates whereas contributions from the 5f electrons and from the pseudoquadrupole interaction are negligible (P_5f/P_latt=0.03). The Sternheimer antishielding factor, γ_∞=-154, is determined and comparison is made between the actinide ion Am³⁺ and its rare-earth analogy Eu³⁺. copyright 1996 The American Physical Society

[en] Highlights: • Mg–Ti joints can be successfully performed at suitable welding variables by CMT. • Typical brazing–welding joints can be formed for Mg–Ti joint and Ti–Mg joint. • The brazing interface is mainly composed of Ti₃Al, Mg₁₇Al₁₂ and Mg_0.97Zn_0.03. • Elements Al and Zn are crucial to join successfully Mg and Ti base metals. - Abstract: Pure titanium TA2 was joined to Mg AZ31B by cold metal transfer (CMT) welding–brazing method in the form of two lap-shear joints (Mg–Ti joint and Ti–Mg joint) with Mg AZ61 wire. The microstructure of Ti/Mg CMT joints was identified and characterized by means of optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The mechanical properties of various welding parameters were compared and analyzed. Desired Ti/Mg CMT joints with satisfied weld appearances and mechanical properties were achieved at suitable welding variables. The Ti/Mg CMT joints had dual characteristics of a welding joint at the Mg side and a brazing joint at the Ti side. Moreover, for two joints, the brazing interfaces were composed of an intermetallic compounds (IMCs) layer including Ti₃Al, Mg₁₇Al₁₂ and Mg_0.97Zn_0.03 phases. Mg–Ti joint had the higher tensile load of 2.10 kN, and Ti–Mg joint had the tensile load of 1.83 kN

[en] Highlights: • Two Al-to-galvanized steel spot plug welding joints were studied by CMT method. • The optimum process variables for the two joints were gotten by orthogonal test. • Connection mechanism of the two joints were discussed. -- Abstract: In this study, cold metal transfer (CMT) spot plug joining of 1 mm thick Al AA6061-T6 to 1 mm thick galvanized steel (i.e., Q235) was studied. Welding variables were optimized for a plug weld in the center of a 25 mm overlap region with aluminum 4043 wire and 100% argon shielding gas. Microstructures and elemental distributions were characterized by scanning electron microscopy with energy dispersive X-ray spectrometer. Mechanical testing of CMT spot plug welded joints was conducted. It was found that it is feasible to join Al AA6061T6-to-galvanized steel by CMT spot plug welding method. The process variables for two joints with Al AA6061T6-to-galvanized mild steel and galvanized mild steel-to-Al AA6061T6 are optimized. The strength of CMT spot welded Al AA6061T6-to-galvanized mild steel is determined primarily by the strength and area of the brazed interface. While, the strength of the galvanized mild steel-to-Al AA6061T6 joint is mainly dependent upon the area of the weld metal