Formation and photoluminescence of Ge and Si nanoparticles encapsulated in oxide layers

Ge and Si semiconductor nanoparticles encapsulated in oxide layers were prepared by the inert gas condensation method. High-resolution electron microscopy and energy dispersive X-ray spectrometry showed the formation of the core-shell structures with a size below 10 nm. The optical absorption spectra of Ge showed the band edges at higher energy compared to the ordinary Ge element. Photoluminescence measurements of them showed the luminescence at 2.2–2.6 eV, which would be due to the formation of core-shell structures. Especially, Ge clusters with a size of approximately 1 nm were formed in the GeOx matrix, which showed strong luminescence at 3.12 eV, which would be due to the quantum size effect of the clusters. The present work indicates that formation of the core-shell structure of semiconductor nanoparticles with oxide layers would be effective for blue shifts of the energy band.