Optical transitions of Cu_2O nanocrystals in SiO_2 fabricated by ion implantation and two-step annealing

摘要

Nanocrystals (NCs) of cuprous oxide (Cu_2O), cupric oxide (CuO), and copper metal (Cu) are fabricated in silica glasses (SiO_2) by implantation of 60 keV Cu~- ions at different annealing conditions. At room temperature, Cu_2O NCs show two sharp absorption peaks at 2.58 and 2.71 eV due to autoionized exciton states, and Cu NCs show a broad peak at ～2.2 eV due to the surface plasmon resonance (SPR). With decreasing temperature down to 2.8 K, the peaks of Cu_2O NCs become much narrower, while the SPR peak of Cu NCs keeps almost the same peak width.