Synthesis and fluorescence properties of a nanoisland-structured SiOx/CuxO composite

Abstract

A nanoisland-structured SiO_x (x ≤ 2)/Cu_xO (x ≤ 2) composite was prepared from a Cu-deposited Si wafer by electrochemical anodization in a hydrofluoric acid (HF) and ferric nitrate (Fe(NO₃)₃) electrolyte. The surface of the nanoisland comprised Cu, Cu oxides, Si nanoparticles and Si oxides. The distribution of elemental Cu on the surface was uniform. Cracks and native Cu-oxides in the deposited Cu layer are the two main factors for the formation of the nanoisland-structured surface. Different from the single red photoluminescence (PL) band emitted from the electrochemical anodized bare Si wafer, a dual-visible PL band with comparable intensities at red and blue ranges was observed. The red PL quenching did not occur in this Cu-ion-doped nanostructured Si due to the different distribution areas of Cu⁺ and the red PL centre. The red PL originates due to oxygen defects in the band gap of Si nanoparticles/Si oxides; the blue PL is the consequence of the band-to-band transitions between 3d¹⁰ and 3d⁹4s¹ of Cu⁺ ions and the intra d → d band transition of Cu²⁺ ions in the interstitial vacancies of Si oxides. Compared with the electrochemical anodized bare Si sample with a single PL band, the nanoisland-structured SiO_x/Cu_xO composite emitting a dual-PL-band is more promising for fabricating white light emitters.