Physical Review Letters
Diffusion of Pd in the Pd/Cu(100) surface alloy was studied as a function of temperature using atom tracking scanning tunneling microscopy. It was shown that Pd diffused by a vacany-exchange mechanism, by following the motion of individual Pd atom incorporated in the surface. Activation energy was measured for diffusion of incorporated Pd atom and was found to be in agreement with ab intio calculated energy.
Physics Today
Abstract not provided.
Physical Review Letters
Atom-tracking scanning tunneling microscopy (AT-STM) was applied to the study of Ge-Si dimer diffusion. It was possible to measure real-time atomic intermixing, determine directly the time and the lattice site at which the intermixing occurs.
Science
The authors carry out a comparative study of the energetic and dynamics of Si-Si, Ge-Ge, and Ge-Si ad-dimers on top of a dimer row in the Si(001) surface, using first-principles calculations. The dynamic appearance of a Ge-Si dimer is distinctively different from that of a Si-Si or Ge-Ge dimer, providing a unique way for its identification by scanning tunneling microscopy (STM). Its rocking motion, observed in STM, actually reflects a 180{degree} rotation of the dimer, involving a piecewise-rotation mechanism. The calculated energy barrier of 0.74 eV is in good agreement with the experimental value of 0.82 eV.
Physical Review Letters
The positions of Ge atoms intermixed in the Si(100) surface at very low concentration are identified using empty-state imaging in scanning tunneling microscopy. A measurable degree of place exchange occurs at temperatures as low as 330 K. Contrary to earlier conclusions, good differentiation between Si atoms and Ge atoms can be achieved by proper imaging conditions.
Nature
The authors have used low-energy electron microscopy to investigate the dynamics of the Si(111) 7 x 7 {r_arrow} 1 x 1 phase transition. Because the densities of the two phases differ, the phase transformation is analogous to precipitation in bulk systems: additional material must diffuse to the phase boundaries in order for the transformation to occur. By measuring the size evolution of an ensemble of domains, and comparing the results to simulations, they have identified a new mechanism of precipitate growth. The source of material necessary for the transformation is the random creation of atom/vacancy pairs at the surface. This mechanism contrasts sharply with classical theories of precipitation, in which mass transport kinetics determine the rate of transformation.