Au 2 + -Implanted Regions in Silicon Visualized Using a Modulated Free-Carrier Absorption Method

Silicon samples were implanted with Au2+ ions of energy 100 keV and doses of 1014cm-2. The area of the implanted region was 2mm×2mm. The size of the Si substrate samples was 5mm×5mm×0.4mm. Spatial distributions of the amplitude and profiles of the modulated free-carrier absorption (MFCA) signal of the implanted silicon samples were recorded and analyzed. The data were obtained using an experimental setup built specifically for MFCA amplitude mapping and measurements of frequency characteristics. For example, the maps and profiles showed that for 520 nm laser illumination, the MFCA amplitude in the implanted region was considerably smaller than that for the substrate. The values of the amplitude of the MFCA signal from the implanted region depended on the wavelength of illuminating light. They convey information related to the optical absorption coefficient of the implanted layers.