Effect of Annealed (0001)α-Al2O3 Surfaces on Heteroepitaxial Growth of Silver Nanoparticles
A. Al-Mohammad
Nano-materials Labs, Physics Department, Atomic Energy Commission of Syria, P.O. Box6091, Damascus, Syria
Received: March 27, 2008; Revised version: September 18, 2008;
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The effect of annealed (0001)α-Al2O3 surfaces on heteroepitaxial growth of silver nanoparticles were analysed by reflection high-energy electron diffraction, transmission electron microscope and selected area electron diffraction. Ag nanoparticles were deposited on 1 × 1 stoichiometric and reconstructed (111)Al//(0001)α-Al2O3 with the Knudsen cell. The maximum cluster density method and the Lifethenz theory of Van der Waals energy were used to investigate the Ag//(0001)α -Al2O3 interface parameters. The growth modes, lattice parameters, nanoparticle forms and sizes are strongly dependent on the substrate surface structures. Initially, three-dimensional islands of Ag nanoparticles grow on both kinds of surfaces with partial hexagonal shapes. Ag nanoparticles on stoichiometric surface create the (111)Ag//(0001)α -Al2O3 interface without any preferred epitaxial direction. On this surface, Gaussian distribution is characteristic of an atom-by-atom growth mode with density of Ag nanoparticles lower than saturation density while a coalescence growth mode appears due to binary collisions between Ag nanoparticles accompanied by a liquid-like behaviour after saturation density. In case of reconstruction substrates, the epitaxial relationships between Ag nanoparticles and the surface are formed (111)Ag//(0001)α -Al2O3, 〈011〉Ag//[1230]α -Al2O3 or 〈011〉Ag//[1100]α-Al2O3. The Ag nanoparticles make rotation with angles between ±6° around the epitaxial orientations 〈1100〉 or 〈1230〉. Only the atom-by-atom growth mode were found at all Ag nanoparticles growth processes.
DOI: 10.12693/APhysPolA.115.679
PACS numbers:68.55.-a, 81.15.Aa, 61.05.jh, 61.46.Df