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.