First-Principles Study of Silicon-Embedded Ni(110)

Abstract

First-principles total energy calculations were performed to investigate stable atomic structures for the displacive adsorption of silicon on the Ni(110) surface. Gibbs free energies were compared for 0-4 silicon atoms embedded into the top layer in a 2×2 unit for the Ni(110) surface. When a half monolayer of Si was embedded, the p(1×2) structure had the lowest energy, and the c(2×2) structure had only 13 meV/1×1 higher energy than the p(1×2) structure. By extending to a 4×2 unit, the c(4×2) structures had almost the same energy with the p(1×2) structure. Alternating Si-Ni chains along the close-packed [110] row play an essential role to stabilize these structures. Si and Ni are alternatively aligned in separate [110] rows forming a p(2×1) structure, which had 276 meV/1×1 higher energy than the p(1×2) structure. For the p(2×1) structure, unique one-dimensional electronic bands derived by the Si-3s states were formed along the [110] direction.

First-principles Study of Si-embedded Ni(100) Surfaces

“…The exchange energy was estimated to be 0.79 eV from the difference of band edge energies between the majority spins (−0.49 eV) and the minority spins (+0.30 eV). The exchange energy is in good agreement with our previous calculations for the Ni(110) surface [10]. Top Ni on the Ni(100) surface in Figure 5(b) shows similar PDOS, but the 3d band is slightly narrower than the bulk band, which is also similar to our previous calculation for the Ni(110) surface [10].…”

“…The exchange energy is in good agreement with our previous calculations for the Ni(110) surface [10]. Top Ni on the Ni(100) surface in Figure 5(b) shows similar PDOS, but the 3d band is slightly narrower than the bulk band, which is also similar to our previous calculation for the Ni(110) surface [10]. On the other hand, the exchange splitting of surface Ni was 0.83 eV (−0.46 eV for majority spins and +0.37 eV for minority spins), which is larger than that of bulk, and gives a larger magnetic moment of 0.73 μB compared to the bulk value of 0.64 μ B .…”

“…A striking feature is an isolated parabolic band from −8 to −10.5 eV. This band is derived from the embedded Si 3s states and was previously found on the Si/Ni(110) surface [10]. Since the Ni(100) surface has a four-fold symmetry, the Si 3p states are separated from the 3s states and they are hybridized to surrounding Ni with p 3 configuration.…”

“…A striking feature of these 2D silicides is that Si and Ni alternate in the close-packed [11 _ 0] row. The stability of these half-monolayer structures was confirmed by first-principles calculations [10]. Furthermore, we recently reported detailed atomic structures of 2D silicides on the Ni(100) surface.…”

Formation of two-dimensional silicide on Ni(100) surface

“…Indeed, only a few reports discussing the structure and reaction of silicidation on metal surfaces have been published. [25][26][27][28][29][30][31] It was reported that 2 × 2 and 3 3 -R30°structures are formed by exposing a Ni(111) surface to silane at high temperatures. 25) In a later study, it was found that a one-third monolayer of Si is involved in the 3 3 -R30°structure, indicating the formation of 2-D Ni 2 Si.…”