Structural properties of the formation of zinc-containing nanoparticles obtained by ion implantation in Si (001) and subsequent thermal annealing

Abstract

This work deals with the study of structural transformations in the near-surface layers of silicon after ion beam synthesis of zinc-containing nanoparticles. Phase formation after implantation of Zn+ ions and two-stage implantation of O+ and Zn+ ions with subsequent thermal annealing in an atmosphere of dry oxygen has been considered. We heated the substrate to 350°C during the implantation to avoid amorphization. After implantation, the specimens were annealed for 1h in a dry oxygen atmosphere at 800°C. Investigation of the structure of surface silicon layers has been carried out by X-ray diffractometry and transmission electron microscopy.We show that a damaged layer with a large concentration of radiation induced defects forms near the surface as a result of the implantation of Zn+ ions with an energy of 50keV. In the as-implanted state, nanoparticles of metallic Zn with a size of about 25nm form at a depth of 40nm inside the damaged silicon layer. Subsequent annealing at 800°C in a dry oxygen atmosphere leads to structural changes in the defect layer and the formation of Zn2SiO4 nanoparticles at a depth of 25nm with an average size of 3nm, as well as oxidation of the existing Zn particles to the Zn2SiO4 phase. The oxidation of the metallic Zn nanoparticles starts from the surface of the particles and leads to the formation of particles with a “core-shell” structure. Analysis of the phase composition of the silicon layer after two-stage implantation with O+ and Zn+ ions showed that Zn and Zn2SiO4 particles form in the as-implanted state. Subsequent annealing at 800°C in a dry oxygen atmosphere leads to an increase in the particle size but does not change the phase composition of the near-surface layer. ZnO nanoparticles were not observed under these experimental conditions of ion beam synthesis.