Nonuniformity in lattice contraction of bismuth nanoclusters heated near its melting point

作者：Esmail A; Abdel Fattah M; Elsayed Ali H E^*

来源：Journal of Applied Physics, 2011, 109(8): 084317.

DOI：10.1063/1.3565028

The structural properties of bismuth nanoclusters were investigated with transmission high-energy electron diffraction from room temperature up to 525 +/- 6 K. The Bi nanoclusters were fabricated by thermal evaporation at room temperature on transmission electron microscope grids coated with an ultrathin carbon film, followed by thermal and femtosecond laser annealing. The annealed sample had an average cluster size of similar to 14 nm along the minor axis and similar to 16 nm along the major axis. The Debye temperature of the annealed nanoclusters was found to be 53 +/- 6 K along the [012] direction and 86 +/- 9 K along the [110] direction. At T=464 +/- 6 K, the diffraction intensity started to deviate from Debye-Waller behavior due to increased lattice anharmonicity. The onset of the melting of the Bi nanoclusters was T similar to 500 +/- 6 K, as measured by the reduction of the nanocluster size through the formation of a liquid shell detected by the width of the diffraction rings. The thermal expansion coefficient of the Bi (012) and (110) planes is positive up to similar to 499 +/- 11 K. However, the expansion coefficient of the Bi (012) planes showed a transition from a positive to a negative value tha

• 出版日期2011-4-15