Conversion electron Mössbauer spectroscopy (CEMS) was used to study the interface behavior between Nb and Fe2O3 layers. The interfacial reaction between Nb and Fe2O3 was enhanced by argon ion irradiation and the rupture of Fe-O bonding caused by irradiation was also observed. The correlation between the Fe-O bonding energy calculated via Molecular Orbital theory and irradiation induced ionization at the Nb/Fe2O3 interface was established to explain the observed phenomena. The subsequent thermal annealing of the irradiated bilayers led to the interdiffusion between Nb and free Fe precipitated from the oxide, with an Fe-Nb phase of ferromagnetic character possibly forming at the interface region. © 1988.

Li J.;Liu B. X.

Nuclear Inst and Methods in Physics Research B

1988

In the Co-Nb system, seven amorphous alloys were synthesized by room-temperature 200 keV xenon ion mixing of multilayered films with various compositions. The composition range favouring amorphization was determined to be from 23 to 80 at.% Co. In addition, two metastable crystalline (MX) phases were consecutively formed in the Co23Nb77 multilayered films, i.e. an HCP phase at a dose of 1*10¹⁵ Xe⁺ cm ^-2 and a FCC phase at a dose of 6*10¹⁵ Xe ⁺ cm^-2. The thermal stabilities of both ion-mixed amorphous alloys and the MX phases were examined by subsequent annealing. To obtain a deep insight concerning all the above observations, a free-energy diagram of the Co-Nb system was constructed by calculating the free-energy curves of the solid solutions, the amorphous phase, the equilibrium compound and the MX phases, which were considered as compound-like phases. To test the relevance of the constructed diagram in its outline, steady-state thermal annealing of the as-deposited Co23Nb77 multilayered films was performed and the results confirmed the calculated relative energy levels of the phases considered. The free-energy diagram can explain the amorphization range as well as the observed evolution of the ion-mixed phases.

Zhang Z. J.;Liu B. X.

Journal of Physics Condensed Matter

1994

Significant enhancement of Fe atom magnetic moment was observed in Fe/nobel metal (Cu, Ag and Au) multilayers prepared by vapor-deposition, and a negative linear relationship was found between the maximum magnetic moment per Fe atom versus the difference of the covalent radius of the constituent metals. It was also found that Pd atoms in Pd/3d- metals (Fe, Co and Ni) multilayered were polarized by the neighboring ferromagnetic atoms, and the magnetic behaviors of the three multilayers were different in three systems.

Liu B. X.;Yang T.;Pan F.

Proceedings of SPIE the International Society for Optical Engineering

1994

Using a metal vapour vacuum arc (MEVVA) ion source, high current Fe ion implantations directly into Si or through an iron film deposited on Si wafers are carried out at an extraction voltage of 40 kV with a current density from 65 to 152 μA cm⁻² at a nominal dose from 3 × 10¹⁷ to 3 × 10¹⁸ cm⁻². For the directly implanted Si wafers, at a fixed dose of 4 × 10¹⁷ cm⁻², a semiconducting β‐FeSi2 layer gradually grows with increasing current density. The unique semiconductivity of the formed β‐FeSi2 layer is evidenced by the measured Hall mobility being in the range of 60 to 100 cm²/Vs. Implanting with the current density of 152 μA cm⁻², the β‐FeSi2 transforms into a metallic α‐FeSi2 phase with a sheet resistance of 42 Ω/□ at a nominal dose of 3 × 10¹⁸ cm⁻². For the Si wafers with deposited Fe film, β‐FeSi2 is also formed by Fe ion implantation. Post‐implantation annealing of the implanted samples provides some useful information for the understanding of the formation mechanism, which is discussed in terms of the simultaneous thermal annealing caused by beam heating during implantation. Copyright © 1995 WILEY‐VCH Verlag GmbH & Co. KGaA

Zhu D. H.;Chen Y. G.;Liu B. X.

Physica Status Solidi A

1995

An investigation of Si ion implantation into Si single crystals covered with a SiO2 layer of various thicknesses (1000-3000 Å) was conducted and new characteristic luminescence bands were observed. A visible band that peaked around 1.89 or 2.0 eV was observed from the as-implanted samples. After high temperature post annealing, a visible band located in the range of 1.7 eV was detected. Interestingly, a new luminescence band around 1.5 eV was observed, for the first time, in a sample covered with a 3000 Å SiO2 layer, after high dose implantation and annealing. We report, in this letter, the experimental results and a brief discussion concerning the various possible mechanisms responsible for the observed luminescence bands.

Lan Aidong;Liu Baixin;Bai Xinde

Japanese Journal of Applied Physics Part 2 Letters

1997

Silicon single crystals with a SiO 2 overlayer of various thicknesses (1000-6000Å) were implanted by 120 and 160 keV Si-ions to doses in a range of (0.5-1.0)×10 ¹⁷cm ^-2 to study the visible light emission in their as-implanted and post-annealed states. An emission band peaked around 2.0 eV was visible in the photoluminescence (PL) spectra of all the as-implanted samples. After post-annealing at 1100° C in a flowing N 2 gas, it was found that a visible band peaked in the range of 1.7 eV is detectable from all the samples and that the PL intensity exihibits a correlation with the oxygen concentration in the implanted region. Possible mechanisms responsible for the observed light emission were also discussed. © 1997 by Allerton Press, Inc.

Lan Ai-Dong;Liu Bai-Xin;Bai Xin-De

Chinese Physics Letters

1997

Si-ion implantation into Si single crystals with SiO2 overlayers of various thicknesses was carried out to study the implantation-induced visible light emission. Some new characteristic luminescence bands associated with the thin SiO2 overlayer were observed. A visible band peaked in the range of 1.7 eV was observed after post annealing at 1100°C in a flowing N2 and this band appeared from the samples covered with a very thin layer (1000 Å). A new luminescence band around 1.5 eV was detected in the samples with a thick SiO2 (3000 Å) layer after post annealing. Possible mechanisms responsible for the observed light emission were also discussed.

Lan A. D.;Bai X. D.;Liu B. X.

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms

1997

The SiO2 layer thermally grown on Si was implanted by 130 and 160 keV Si ions at liquid nitrogen temperature or room temperature to a dose of 1 × 10¹⁷ ions cm^-2. From the as-implanted samples, a visible photoluminescence band centered around 2.0 eV was observed. After post annealing at 1100 °C, another visible band in the range of 1.7 eV was detected. Interestingly, with increasing the annealing time, a blue shift of the peak energy and intensity variation of the 1.7 eV band were observed. A possible interpretation for the observations is also discussed. © 1998 Elsevier Science S.A. All rights reserved.

Liu B. X.;Lan A. D.;Bai X. D.

Materials Chemistry and Physics

1998

NiSi2 layer was formed on Si wafers by metal vapor vacuum arc (MEVVA) ion implantation by a selected Ni-ion current density of 35 μΑ/cm² corresponding to a Si surface temperature rise of 380 °C, at which there was no size difference between the growing NiSi2 and Si substrates. After implantation to a nominal dose of 2 × 10¹⁷ cm^-2, the resistivities of the formed NiSi2 layers were measured to be 9 μΩ cm for the bare Si and down to 6 μΩ cm for the Si with a pre-deposited 10 nm Ni overlayer, respectively. The unique electrical property of the so-formed NiSi2 layer is discussed in terms of those structure-related factors involved in forming and cooling processes © 1998 Elsevier Science B.V. All rights reserved.

Gao K. Y.;Liu B. X.

Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms

1998

Thermal analysis, x-ray diffraction and TEM selected area electron diffraction (SAD) methods were used to investigate the phase evolution of the Nd2Fe14B-C system upon solid state reaction. The experimental results revealed that there were some solid state reactions of carbon with the Nd2Fe14B phase and two new Nd-enriched carbides were formed in the Nd2Fe14B-C system, i.e. a bcc phase with a lattice parameter of a = 0.5131 nm and a tetragonal phase with lattice parameters a = 1.0143 nm, c = 1.4486 nm. It was also found that the formation of Nd-enriched carbides was related to the thermal reaction temperature and carbon concentration in the sample.

Pan F.;Zhang M.;Zhao R. F.;Liu B. X.;Tokunaga M.

Journal of Physics D Applied Physics

1998