Vibration-Driven Self-Doping of Dangling-Bond Wires on Si(553)-Au Surfaces

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 x3 order along the Si step edges and, subsequently, the x2 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.