Doping density dependence of 4f-4f couplings between Er and Yb ions in nanocrystalline Si

This paper presents the formation and time-resolved investigation of Er and Yb co-doped nc-Si thin films. Since the energy of the only one excited state ²F₅2/ of a Yb³⁺ ion is almost same to that of the second excited state ⁴I₁₁2/ of an Er^3- ion, the optical transition between them is expected to raise the excitation rate of the Er³⁺ ion.