Optical transitions of Cu2O nanocrystals in SiO2 fabricated by ion implantation and two-step annealing

Nanocrystals (NCs) of cuprous oxide (Cu2O), cupric oxide (CuO), and copper metal (Cu) are fabricated in silica glasses (SiO2) by implantation of 60keV Cu− ions at different annealing conditions. At room temperature, Cu2O NCs show two sharp absorption peaks at 2.58 and 2.71eV due to autoionized exciton states, and Cu NCs show a broad peak at ∼2.2eV due to the surface plasmon resonance (SPR). With decreasing temperature down to 2.8K, the peaks of Cu2O NCs become much narrower, while the SPR peak of Cu NCs keeps almost the same peak width.