The dependence of diffusion upon rapid thermal annealing was studied in Yb-doped material. During annealing at temperatures of between 800 and 1000C, the Yb segregated at crystal/amorphous interfaces and at the free surfaces. The efficiency of optical activation also increased with annealing temperature. The amorphous layer re-grew, and no photoluminescence was observed, after annealing at 1200C.

T.B.Xu, P.R.Zhu, D.Q.Li, T.Q.Ren, H.L.Sun, S.K.Wan: Physics Letters A, 1994, 189[5], 423-7