SIZE CONTROL OF SI NANOCRYSTALLITES FORMED IN AMORPHOUS SI MATRIX BY ER-DOPING

Si nanocrystallites formed in amorphous Si (a-Si) show intense blue lu minescence at room temperature. The samples are fabricated by crystall ization 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 ato m introduces additional strain in the a-Si matrix and behaves as a nuc leation 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 anne aling temperature. By controlling the Er density and crystallization t emperature, we have fabricated a series of nanocrystalline (nc) Si sam ples having the average sizes from 3 to 10 nm. The smallest size achie ved here is 2.7 nm. A bright blue luminescence from the Si nanocrystal lites as well as a 1.54 mu m emission from the doped Er3+ ions were ob served up to room temperature. (C) 1998 Elsevier Science S.A. All righ ts reserved.