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Formation mechanism of Zn2SiO4 nanoparticles depending on the Zn/Si ratio of Zn-Si-O films
|Young-Hwan Kim , Woon-Jo Cho , Seong-Il Kim|
Nano Device Research Center, Korea Institute of Science and Technology (KIST), P.O.Box 131, Cheongryang, Seoul 130-650, Korea, South
Low dimensional materials have attracted much interest due to potential to optoelectronic and/or electronic device applications using their unique properties. From the viewpoint of practical applications, fabrication of low dimensional materials directly on silicon substrates, which are mostly used for various devices, is important issue. In this work, Zn-Si-O films with various compositions were sputter-deposited on Si (100) substrates and post-annealed by using rapid thermal process at 700 oC for 3 minutes in a nitrogen atmosphere. The composition of Zn-Si-O films ranging from Zn/Si=0.4 to Zn/Si=11.2, measured by EDS equipped with high-resolution TEM (HRTEM), could be obtained by controlling the area ratio of ZnO to Si target. As a result of HRTEM analysis, the microstructures of Zn-Si-O films were strongly dependent on the Zn/Si ratio. Three types of microstructure were evolved depending on the Zn/Si ratio. When the Zn/Si ratio was below ~1.6, nanoparticles were distributed in an amorphous matrix of SiOx. In this case, nanoparticles exist almost independently. When Zn/Si ratio was ~4.0, nanoparticles are almost interconnected and nanoparticle-network structure was developed. When Zn/Si ratio was ~11.2, ZnO film structure was formed, in which ZnO film was grown in a preferred orientation of  normal to substrate surface. From the HRTEM analysis, the nanoparticles could be identified as a Zn2SiO4 phase. Consequently, Zn2SiO4 nanoparticles could be simply synthesized by controlling the film composition and post-annealing conditions, which show strong UV-blue cathodoluminescent emission leading to optoelectronic device application. The mechanism of formation of a Zn2SiO4 nanoparticle will be systematically discussed based on the HRTEM analysis of Zn-Si-O films and the XRD results of Zn2SiO4 bulk annealed at various temperatures.
Presentation: Poster at E-MRS Fall Meeting 2007, Symposium A, by Young-Hwan Kim
See On-line Journal of E-MRS Fall Meeting 2007
Submitted: 2007-05-14 16:52 Revised: 2009-06-07 00:44