Size control of Si nanocrystallites formed in amorphous Si matrix by Er-doping

Si nanocrystallites formed in amorphous Si (a-Si) show intense blue luminescence at room temperature. The samples are fabricated by crystallization of a-Si thin films, which leads to a large size dispersion of the nanocrystallites due to a random distribution of strain fields in the a-Si phase. In this work, we demonstrate a process of controlling the crystallite size by doping Er in the a-Si layers. The doped Er atom introduces additional strain in the a-Si matrix and behaves as a nucleation center during the crystallization. It is demonstrated that the average size of the Si nanocrystallites is almost independent of the crystallization time for a certain Er concentration and a certain annealing temperature. By controlling the Er density and crystallization temperature, we have fabricated a series of nanocrystalline (nc) Si samples having the average sizes from 3 to 10 nm. The smallest size achieved here is 2.7 nm. A bright blue luminescence from the Si nanocrystallites as well as a 1.54 μm emission from the doped Er3+ ions were observed up to room temperature.