Size-controlled Si nanocrystals deposited by electron beam evaporation (I.P1.33)

Abstract

Due to the quantum confinement effect, the band gap energy tunability of silicon nanocrystals (Si-NCs) is directly related to the size of these nanostructures, which has been largely studied for its implementation in photovoltaics and light-emitting devices. Chemical deposition methods have typically been employed for matrix-embedded Si-NCs fabrication, being the utilization of toxic gases a serious handicap aiming at mass production. In contrast, physical deposition methods such as electron beam evaporation (EBE) encourage the direct deposition of the material under study without chemical reactions being involved in the process.

In this work, Si-NCs have been fabricated by means of EBE, by alternatively depositing SiO2 and Si layers, in an oxygen atmosphere. The stoichiometry of layers was determined by X-ray spectroscopy, which confirmed the controlled silicon oxidation in order to attain silicon-rich oxide (SRO) layers. A post-deposition annealing process was carried out at different temperatures in order to achieve the Si precipitation in the form of nanocrystals. Transmission electron microscopy confirmed the presence of crystalline Si-nanoprecipitates, which agrees with Raman scattering measurements. The photoluminescence (PL) spectra from the Si-NCs samples could be deconvolved into two contributions, whose dynamics suggests that PL is originated in two different luminescent centres. PL results will be discussed considering the possible origin of the luminescent centres and the published data in similar samples.