Electromigration forces on ions in carbon nanotubes

We calculate the electromigration forces on ions such as adsorbed alkali metal atoms in a carbon nanotube transistor. The forces are especially large in the turn-on regime of the transistor and much smaller in the off and on states. Electromigration in the channel is driven almost exclusively by the wind force. The sign of the "effective valence" Z* is independent of the actual charge sign but can be reversed with gate voltage, providing a dramatic illustration of the quantum character of the wind force. Our self-consistent nonequilibrium Green's function calculations treat a ballistic device within a tight-binding approximation.     

Core-level satellite structure in photoemission spectra of transition metals

A theory of the satellite structure of the core-level photoemission spectrum of transition metals is presented. It is applied to the $\text{2}\text{p}{}_{\mathrm{<mtext>3</mtext><mtext>2</mtext>}}$ level of metallic nickel. The calculation is carried out for both the paramagnetic and ferromagnetic states and is based on two scattering parameters, one intraband and one interband. Agreement with experiment is very good.     

Structure and energetics of the Si- SiO2 interface

Using a Monte Carlo approach, we identify low-energy structures for the (001)-oriented Si-SiO2 interface. The optimal interface structure found consists of an ordered array of Si-O-Si "bridges," with low strain energy. This structure explains several puzzling experimental observations.     

Phase coexistence during surface phase transitions

In contrast to standard thermodynamic models, we observe phase coexistence over an extended temperature range at a first-order surface phase transition. We have measured the domain evolution of the Si(111)-( 7x7) to ( 1x1) phase transition with temperature, using low-energy electron microscopy. Comparison with detailed, quantitative theoretical predictions shows that coexistence is due to long-range elastic and electrostatic domain interactions. Phase coexistence is predicted to be a universal feature of surface phase transitions.