Mechanism of copper selenide growth on copper-oxide–selenium system

Transmission electron microscopy was used to study spontaneous copper selenide formation on Cu particles covered with an oxide layer. Even if the copper particle surface was covered with a Cu2O layer, selenides were formed by diffusion through the metal oxide layer. For a particle size less than 50 nm, selenide was formed in Cu particles by the diffusion of Se atoms passing through the Cu2O layer. For particles larger than 100 nm in size, selenide was formed in Se film. It was also found that the thickness of the Cu2O layer on the surface of Cu particle accelerated diffusion of Se atoms to the copper particle.