A study of nickel and cobalt silicides formed in the Ni/Co/Si(1 0 0) system by thermal annealing

In this work, the Ni/Co/Si system was annealed at temperatures ranging from 300 °C to 800 °C. The samples were characterized by means of X-ray diffraction (XRD), Raman spectroscopy, Rutherford backscattering spectroscopy (RBS), atomic force microscopy (AFM) and sheet resistance measurement. The XRD and Raman spectroscopy results showed that the formation of nickel and cobalt silicides (CoSi, Co2Si, Ni2Si, NiSi, NiSi2, CoSi2) is an annealing temperature dependent diffusion process. The diffusion phenomenon was evidenced by RBS. The low values of the sheet resistance which were correlated with the films surface roughness were attributed to the formation of both CoSi and NiSi phases.

Electrochemical behavior of cobalt silicides in H2SO4 + HF solutions at high anodic potentials

The voltammetric and impedance characteristics of CoSi2 and Co2Si electrodes were obtained in 0,5 M H2SO4 + x M HF (x = 0,01–0,05) and 0,05 M H2SO4 + 0,01 M HF solutions at the electrode potentials of 1.8 to 3.0 V (nhe). It was shown that the anodic processes on cobalt silicides in H2SO4 + HF solutions involve multiple steps. It is assumed that there are chemical steps in the overall process on Co2Si.

Интеркаляционный синтез силицидов кобальта под графеном, выращенным на карбиде кремния

The process of formation of cobalt silicides near the graphene-silicon carbide interface by intercalation of single-layer graphene grown on the 4 H - and 6 H -SiC(0001) polytypes with cobalt and silicon is studied. The experiments were carried out in situ in ultrahigh vacuum. The analysis of the samples is performed by high-energy-resolution photoelectron spectroscopy using synchrotron radiation, low-energy electron diffraction, and also Raman spectroscopy, atomic-force and kelvin-probe microscopies. The thicknesses of the deposited cobalt and silicon layers is varied to 2 nm, and the sample temperature, from room temperature to 1000°C. Co and Si atoms deposited on heated samples is found to penetrate under graphene and are localized between the buffer layer and the substrate, which leads to a transformation of the buffer layer into additional graphene layer. It is shown that the result of intercalation of the system with cobalt and silicon is the formation under two-layer graphene of a Co–Si solid solution and silicide CoSi coated by the surface Co_3Si phase. It is shown that the thickness and the composition of the formed silicide films can be changed by varying the amount of the intercalated material and the order of their depositions.

Интеркалирование графена на карбиде кремния кобальтом

In this paper, we studied cobalt intercalation of single-layer graphene grown on the 4 H -SiC(0001) polytype. The experiments were carried out in situ under ultrahigh vacuum conditions by high energy resolution photoelectron spectroscopy using synchrotron radiation and low energy electron diffraction. The nominal thicknesses of the deposited cobalt layers varied in the range of 0.2–5 nm, while the sample temperature was varied from room temperature to 800°C. Unlike Fe films, the annealing of Co films deposited on graphene at room temperature is shown to not intercalate graphene by cobalt. The formation of the graphene–cobalt–SiC intercalation system was detected upon deposition of Co atoms on samples heated to temperatures of above ~400°C. Cobalt films with a thickness up to 2 nm under graphene are formed using this method, and they are shown to be magnetized along the surface at thicknesses of greater than 1.3 nm. Graphene intercalation by cobalt was found to be accompanied by the chemical interaction of Co atoms with silicon carbide leading to the synthesis of cobalt silicides. At temperatures of above 500°C, the growth of cobalt films under graphene is limited by the diffusion of Co atoms into the bulk of silicon carbide.