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.

Ai Dong Lan;百新 柳;Xin De Bai

Chinese Physics Letters

1997

An n-body Ni-Ti potential is derived and applied in a molecular dynamics simulation to study the maximum supersaturated solubility of the terminal solid solutions and solid-state reaction in a Ni/Ti bilayer. It reveals that during interfacial reaction of the Ni/Ti bilayer the Ti lattice reaches its maximum solubility by dissolving Ni earlier than Ni does through dissolution-of Ti, which results in a sequential disordering of first Ti and then Ni, although Ti has a higher melting point than Ni. In the Ni-Zr, Ni-Mo and Ni-Ta systems, however, the Ni lattice collapses more rapidly because it reaches a maximum solubility earlier than its partners, which have higher melting points than Ni. A solubility criterion is thus relevant for all the above cases; the lower the maximum solid solubility the less stable is the lattice of the metal upon solid-state reaction.

文生 赖;Q. Zhang;百新 柳;恩 马

Philosophical Magazine Letters

2001-1

Based on thermodynamic calculations, a Gibbs free energy diagram was constructed to predict the possibility of metastable alloy formation in the equilibrium immiscible Au-W system characterized by a large positive heat of formation of +17kJ/mol. Accordingly, in the properly designed Au-W multilayered films, a unique super-saturated fcc solid solution was obtained by ion beam irradiation on the Au-rich side. More interestingly, on the W-rich side, an amorphous alloy was formed through a two-step structural transition. First, a low dose (2×10¹⁵ Xe⁺/cm²) irradiation resulted in the formation of a super-saturated bcc solid solution. Second, the bcc solid solution transformed into an amorphous state upon further irradiation up to a dose of 8×10¹⁵ Xe⁺/cm². We report, in this paper, results of thermodynamic calculations and the experimental observations concerning the metastable alloy formation in the Au-W system together with a brief discussion of the structural transition mechanism.

R. F. Zhang;百新 柳

Journal of Alloys and Compounds

2004-7-28

Based on the projector-augmented wave method, ab initio calculations were performed for more than 60 binary metastable Fe-Cu, Fe-Ag and Fe-Au compounds. It was found that the magnetic moment of Fe can be greatly enhanced and could even reach a value beyond 3 μ_B in these metastable alloys. A distinct positive correlation between the magnetic moment of Fe and atomic volume was observed in these ferromagnetic alloys, suggesting Fe atoms locating in large-sized structures may possess high magnetic moments.

J. H. Li;Y. Kong;K. W. Geng;百新 柳

Scripta Materialia

2007-7

Abnormal structural changes were observed in the equilibrium immiscible Co₅₀Cu₅₀ multilayers induced by 200 keV xenon-ion irradiation at 77 K. First, a dodecagonal quasicrystal phase was formed at an irradiation dose of 1 × 10¹⁵ Xe⁺ cm^-2. Secondly, series of selected diffraction patterns taken later showed that the dodecagonal phase formed evolved to feature a high degree of ordering with increasing ion dose. Moreover, molecular dynamics simulations verified the possibility of formation of a metastable phase in the Co-Cu system. A mechanism possibly responsible for the observed structural changes upon ion irradiation is also discussed.

Z. F. Li;百新 柳

Journal of Physics Condensed Matter

2001-6-25

Amorphous thin films are formed by 300 ke V Xe⁺ ion mixing of multiple‐layered samples in the Ni‐Nb (f.c.c.–b.c.c.) system at four different compositions (Ni₃₅Nb₆₅, Ni₅₅Nb₄₅, Ni₆₅Nb₃₅, and Ni₈₀Nb₂₀). This confirms the “structural difference rule for amorphous alloy formation” by ion mixing. Some properties of the Ni‐Nb amorphous thin films, including their recrystallization temperatures and irradiation stability, are studied. The amorphous alloy formation in this system, as well as the said properties, are compared to those of a similar system, the Ni‐Mo (f.c.c.–b.c.c.) system.

K. T‐Y Kung;百新 柳;M. ‐A Nicolet

Physica Status Solidi (A) Applied Research

1983-5-16

An fcc-structured Fe55 Nb45 alloy with a large lattice constant of a≈0.408 nm was synthesized by 200 keV xenon ion irradiation at a dose of 3× 1015 Xe+ cm2. The Fe atom in Fe55 Nb45 alloy presents a distinct magnetic moment as high as 2.41 μB, confirming a high-spin ferromagnetic state of fcc Fe predicted by ab initio calculation. Further irradiation, i.e., at a dose of 5× 1015 Xe+ cm2, induced phase separation, resulting in fractal growth consisting of Fe72 Nb28 nanoclusters embedded in Fe35 Nb65 matrix. The formation mechanism of alloy phases as well as fractal pattern was discussed in terms of the atomic collision theory.

K. P. Tai;T. L. Wang;百新 柳

Applied Physics Letters

2007

Amorphization in the Ni/Zr bilayer upon isothermal annealing is observed by a molecular-dynamics simulation using an n-body potential. The disordering process is found to initiate and extend from a preset disordered interfacial layer through atomic diffusion and alloying between Ni and Zr layers. Furthermore, it is clearly evidenced by our simulation that the growing process of amorphous phase follows a t1/2 time dependence kinetics, featuring a typical diffusion-limited growth with asymmetric speeds in two opposite directions. All these results suggest that the observed amorphization is, in fact, a result of diffusion-limited-reaction.

文生 赖;百新 柳

Computational Materials Science

1999-2

Inherent hierarchical structure and its effect on shear localization were clarified for ternary Mg-Cu-Ni metallic glasses via molecular dynamics studies based on a newly constructed n-body potential for the system. Assisted by a proposed index to detect the medium-range correlation heterogeneity, it was found that the Cu/Ni-centered icosahedra and specific Mg-centered clusters exhibit a strong preference to interconnect, leading to the formation, over an extended scale, of a percolated network that serves as structural skeleton in the glassy matrix. In constituting the skeleton network, the clusters mainly integrate in an interpenetrating mode, while the noninterpenetrating linkages provide additional reinforcements, jointly consolidating the structural and energetic stability of the skeleton. Furthermore, by monitoring the structural evolution upon compressive deformation, it was revealed that the gradual collapse of the skeleton network is intimately correlated to the mechanical response of metallic glasses and acts as a structural signature of the initiation and propagation of shear bands.

Q. Wang;J. H. Li;J. B. Liu;百新 柳

Physical Chemistry Chemical Physics

2014-8-20

Employing the Vienna ab initio simulation package, the first-principles total energy and magnetic moment calculations are performed for Co under constant system-volume and fixed crystal symmetry conditions. The calculated results propose an isosteric Bain path (IBP) for Co and under a constant system-volume condition, there exist two total-energy minimum points or only one minimum point along the hexagonal IBPs. The stability of the minimum points is correlated to the elastic restrictions of the crystals and a critical system volume is found to be about 1.5 times that at the equilibrium ground state, predicting that the possible states of Co could only be stable when the system volume is smaller than the critical value but not otherwise. In addition, the calculated atomic magnetic moment is found to feature a strong correlation with the system volume.

H. B. Guo;J. H. Li;L. T. Kong;百新 柳

Physical Review B - Condensed Matter and Materials Physics

2005-10-1