Dr. Lereah Yossi

  
Affiliation:Faculty of Engineering
Tel:  (972)-3-6407776
 
Email: lereah@eng.tau.ac.il
 
Personal Website:

 
Postal Address:Faculty of Engineering
Tel Aviv University
Tel Aviv 69978

Research Interest

Solid-Liquid Phase Transition in metallic nanoparticles

The solid-liquid transition is a 1st order transition for bulk material, however gradually surface melting is known for finite size crystals. The solid liquid transition for nanometer metallic particles is studied by In Situ Transmission Electron Microscopy. It was found that surface melting phenomenon is enhanced for particles on the scale of 10 nanometer, while for particles of lower size the solid/liquid state are not sharp defined indicating the existence of solid-liquid intermediate state. While classical solid is characterized by atoms at fixed and order positions, the solid state in nanoparticles is characterized by temporally order that fluctuate with time scale of tens millisecond. Analysis of the structural fluctuation indicates correlation with movement of planar defects (sequence of images enclosed). The dependence of the fluctuation rate on temperature indicates the activation energies that are relevant to the solid-liquid intermediate state.


Sequence of high resolution electron micrographs showing the movement of planar crystallographic defect in Pb nano-particlest

Selected Publications


  • A. Be'er, R. Kofman, F. Phillipp and Y. Lereah Spontaneous crystallographic instabilities of Pb nanoparticles in a SiO matrix Physical Review B 76 075410 (2007).
  • A. Be'er, R. Kofman, F. Phillipp and Y. Lereah Quantitative Experimental Studies of Spontanous Rotations of Bi Nano-Particles Physical Review B 74 224111 (2006).