Biomedical subjects

B S Swartzentruber

Publications and source records attributed to B S Swartzentruber.

4 recordsLinked to original sources

PubMed2003

Changing the diffusion mechanism of Ge-Si dimers on Si(001) using an electric field.

We change the diffusion mechanism of adsorbed Ge-Si dimers on Si(001) using the electric field of a scanning tunneling microscope tip. By comparing the measured field dependence with first-principles calculations we conclude that, in negative field, i.e., when electrons are attracted towards the vacuum, the dimer diffuses as a unit, rotating as it translates, whereas, in positive field the dimer bond is substantially stretched at the transition state as it slides along the substrate. Furthermore, the active mechanism in positive fields facilitates intermixing of Ge in the Si lattice, whereas intermixing is suppressed in negative fields.

Journal Article↗

PubMed2003

Vacancy-mediated and exchange diffusion in a Pb/Cu(111) surface alloy: concurrent diffusion on two length scales.

Pb diffuses in a Pb/Cu(111) surface alloy predominantly by exchange with surface vacancies and, much less frequently, by exchange with thermal Cu adatoms. Because the infrequent adatom exchanges transport Pb atoms much farther, both processes affect observations of Pb transport in the Pb/Cu(111) surface alloy.

Journal Article↗

PubMed2001

Diffusion kinetics in the Pd/Cu(001) surface alloy.

We use atom-tracking scanning tunneling microscopy to study the diffusion of Pd in the Pd/Cu(001) surface alloy as a function of temperature. By following the motion of individual Pd atoms incorporated in the surface, we show that Pd diffuses by a vacancy-exchange mechanism. We measure an activation energy for the diffusion of incorporated Pd atoms of 0.88 eV, which is in good agreement with our ab initio calculated energy of 0.94 eV.

Journal Article↗

PubMed2000

Unique dynamic appearance of a Ge-Si ad-dimer on Si(001).

We carry out a comparative study of the energetics 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 degrees 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.

Journal Article↗