AVS 50th International Symposium
    Nanometer Structures Monday Sessions
       Session NS-MoM

Paper NS-MoM9
Si Nanocrystal Synthesis in an Oxide Matrix: A Multiscale Computational Study

Monday, November 3, 2003, 11:00 am, Room 316

Session: Quantum Dots and Nanoscale Devices
Presenter: D. Yu, University of Texas at Austin
Authors: D. Yu, University of Texas at Austin
G.S. Hwang, University of Texas at Austin
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Nanocrystalline Si (nc-Si) embedded in a SiO@sub2@ matrix is receiving great attention due to its interesting fundamental physical properties and promising applications for advanced microelectronic devices and optoelectronic devices. The unique electrical and optical properties of embedded Si nanocrystals appear to be strongly influenced by their crystallite size, shape, density as well as Si/SiO@sub2@ interface structures. It is therefore necessary to develop a detailed understanding of the nc-Si growth and Si-SiO@sub2@ interfacial interactions. Although experiments offer many clues to the nanocrystal formation and interface properties, their interpretations often remain controversial. In this talk, we will present our multiscale computational model for the synthesis of Si nanoclusters in an oxide matrix. Our multiscale model integrates various state-of-the-art theoretical methods at different time and length scales, such as first principles quantum mechanics, molecular mechanics, and kinetic Monte Carlo. Using the multiscale approach, we have examined i) formation mechanism of Si clusters in silicon suboxide, ii) shape evolution of embedded nanoclusters, iii) Si-SiO@sub2@ interface structure and strains. Our simulations show that small silicon clusters agglomerate very rapidly at the early stage of thermal annealing mostly via coalescence. As the Si cluster density gets lower, the coalescence becomes less probable and the cluster growth continues mainly by Ostwald ripening (which appears be several orders of magnitude slower than the initial stage coalescence). Our theoretical study also demonstrates that the average size of silicon clusters is a strong function of the initial silicon supersaturation. Our results are in good agreement with recent experimental observations.