Abstract
Density-functional theory is used to explore the Si(553)-Au surface dynamics. Our study (i)reveals a complex two-stage order-disorder phase transition where with rising temperature first the ×3 order along the Si step edges and, subsequently, the ×2 order of the Au chains is lost, (ii)identifies the transient modification of the electron chemical potential during soft Au chain vibrations as instrumental for disorder at the step edge, and (iii)shows that the transition leads to a self-doping of the Si dangling-bond wire at the step edge. The calculations are corroborated by Raman measurements of surface phonon modes and explain previous electron diffraction, scanning tunneling microscopy, and surface transport data.
Highlights
Dangling-bond nanostructures are potential fundamental building blocks for atom-scale electronics [1,2,3,4]
The calculations are corroborated by Raman measurements of surface phonon modes and explain previous electron diffraction, scanning tunneling microscopy, and surface transport data
This ×3 periodicity together with a ×2 periodicity due to Au chain dimerization is seen by scanning tunneling microscopy (STM) [17,21,22,23] and low-energy electron diffraction (LEED) [24]
Summary
Dangling-bond (db) nanostructures are potential fundamental building blocks for atom-scale electronics [1,2,3,4]. In this Letter, density-functional theory (DFT) calculations and Raman measurements are presented which (i) provide a consistent explanation for the experimental data and (ii) reveal a complex phase transition mechanism that involves the electron doping of the step edge db wire: A soft Au chain phonon mode is identified that facilitates— via Au → Si db charge transfer—an order-disorder transition at the Si step edge starting below 100 K.
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