Size characterisation of noble-metal nano-crystals formed in sapphire by ion irradiation and subsequent thermal annealing

Metallic nano-particles embedded in transparent dielectrics are very important for new technological applications because of their unique optical properties. These properties depend strongly on the size and shape of the nano-particles. In order to achieve the synthesis of metallic nano-particles it has been used the technique of ion implantation. This is a very common technique because it allows the control of the depth and concentration of the metallic ions inside the sample, limited mostly by straggling, without introducing other contaminant agents. The purpose of this work was to measure the size of the nano-particles grown under different conditions in Sapphire and its size evolution during the growth process. To achieve this goal, α-Al2O3 single crystals were implanted with Ag or Au ions at room temperature with different fluences (from 2 × 1016 ions/cm2 to 8 × 1016 ions/cm2). Afterwards, the samples were annealed at different temperatures (from 600 °C to 1100 °C) in oxidising, reducing, Ar or N2 atmospheres. We measured the ion depth profile by Rutherford Backscattering Spectroscopy (RBS) and the nano-crystals size distribution by using two methods, the surface plasmon resonance in the optical extinction spectrum and the Transmission Electron Microscopy (TEM).