The composite structures based on nickel rods in the matrix of silicon dioxide formation peculiarities study using synchrotron XANES in the electrons and photons yield registration modes

Abstract

Purpose. The aim of this work was atomic and electronic structure and phase composition study of submicron Nirods arrays formed by electrochemical deposition in a porous SiO2 matrix on crystalline silicon depending on the conditions of their production by the synchrotron technique of X-ray Absorption Near Edge Structure (XANES) in the near-surface layers sensitive registration mode of total electron yield detection and bulk sensitive registration mode of fluorescence yield detection. Methods and Methodology. Nickel rods arrays were obtained by electrochemical deposition of metal into the pores of the silicon dioxide matrix formed by the ion-tracking technique. Latent tracks were formed by irradiating the SiO2 layer with heavy gold ions at the Han-Meitner Institute accelerator (Berlin, Germany). In the first case, ion fluence under irradiation was 1·108 cm-2, and etching time was 40 minutes (group A), in the second case ion fluence was 5·108 cm-2, etching time was 80 minutes (group B). The initial SiO2/Si structures (from the formed oxide layer to the finished porous matrix) and Ni/SiO2/Si composite structures were studied using the scanning electron microscopy (SEM) with the use of LEO1455-VP microscope. The surface morphology was studied in the mode of secondary electrons detection. The local atomic and electronic structure in Ni/SiO2/Si composite structures was studied by XANES spectra. XANES were simultaneously recorded by the method of measuring total electron yield and by the fluorescent photons detection mode. X-ray spectroscopy data were obtained at the Russian German beamline of BESSY II synchrotron of the Helmholtz Zentrum Berlin (Germany). The vacuum in the spectrometers chambers was 10-10 Torr, the instrument broadening was 0.1 eV. When registering TEY, the analysis depth was ∼ 10 nm (O K absorption edge) and 15 nm (Ni L2,3 absorption edge). At the same time the depth of analysis for XANES data recording in fluorescence yield mode exceeds hundreds of nanometers. A pure gold foil signal was used to calibrate and normalize the experimental spectra. The following objects were used as reference objects: SiO2 matrix without nickel filling, thermal SiO2 film with thickness of 100 nm, commercial: metallic nickel, nickel oxide NiO, nickel silicide Ni2Si produced by Alfa Aesar. Results. SEM studies have shown effective electrodeposition of nickel in the pores of the oxide layer on crystalline silicon. The direct dependence of the formation efficiency and density of nickel particles coating (resp. pores) of the composite structure Ni/SiO2/Si is demonstrated from the fluence of ions as the main parameter of the formation tracks, and the time of electrochemical deposition. However, the metal/semiconductor interface (particle / substrate), the characteristics of which can have a significant effect on the properties of the composite structure, is generally hidden for SEM analysis from the surface at least by the layer thickness of the silicon oxide dielectric matrix.