Exploring structures and properties of nickel silicides at pressures of the Earth’s core

Given the highly possible existence of nickel and silicon in Earth’s core, the study of the reaction between Ni and Si and resulting structure at the pressure corresponding to the...

Влияние образования силицидов на удельное сопротивление кремния

The effect of the formation of thin films of nickel silicides on the migration of intrinsic p -type impurities in silicon was studied for the first time. It was found that bulk resistance $${{\rho }_{{v}}}$$ of a single Si crystal increases by a factor of 3–4 if a NiSi_2 film with thickness θ ≥ 50–100 Å forms on its surface. This is attributable to the migration of boron atoms toward the silicide film. The Si layer thickness enabling measurable boron migration was estimated at 800–1000 Å.

ANODIC OXYGEN EVOLUTION ON IRON, COBALT AND NICKEL SILICIDES IN ALKALINE ELECTROLYTE

The kinetics of oxygen evolution reaction on iron, cobalt and nickel monosilicides in (0.1 – 5.0) M NaOH was studied using methods of polarization and impedance measurements. The values of derivatives dE/dlgi, dlgi/dpH, dE/dpH were determined. The oxygen evolution on FeSi, CoSi and NiSi electrodes in alkaline solution was established to have regularities which are characteristic to Fe, Co and Ni electrodes, respectively.

First-principles investigation of mechanical and thermodynamic properties of nickel silicides at finite temperature -=SUP=-*-=/SUP=-

First-principles calculations are performed to investigate lattice parameters, elastic constants and 3D directional Young’s modulus E of nickel silicides (i.e., β-Ni_3Si, δ-Ni_2Si, θ-Ni_2Si, ε-NiSi, and θ-Ni_2Si), and thermodynamic properties, such as the Debye temperature, heat capacity, volumetric thermal expansion coefficient, at finite temperature are also explored in combination with the quasi-harmonic Debye model. The calculated results are in a good agreement with available experimental and theoretical values. The five compounds demonstrate elastic anisotropy. The dependence on the direction of stiffness is the greatest for δ-Ni_2Si and θ-Ni_2Si, when the stress is applied, while that for β-Ni_3Si is minimal. The bulk modulus B reduces with increasing temperature, implying that the resistance to volume deformation will weaken with temperature, and the capacity gradually descend for the compound sequence of β-Ni_3Si > δ-Ni_2Si > θ-Ni_2Si > ε-NiSi > θ-Ni_2Si. The temperature dependence of the Debye temperature ΘD is related to the change of lattice parameters, and ΘD gradually decreases for the compound sequence of ε-NiSi > β-Ni_3Si > δ-Ni_2Si > θ-Ni_2Si > θ-Ni_2Si. The volumetric thermal expansion coefficient αV, isochoric heat capacity and isobaric heat capacity C _ p of nickel silicides are proportional to T ^3 at low temperature, subsequently, αV and C _ p show modest linear change at high temperature, whereas C _v obeys the Dulong-Petit limit. In addition, β-Ni_3Si has the largest capability to store or release heat at high temperature. From the perspective of solid state physics, the thermodynamic properties at finite temperature can be used to guide further experimental works and design of novel nickel–silicon alloys.