In this chapter the surface structure and other surface related properties of In-terminated Si(111) are studied using Raman spectroscopy.
In-terminated Si(111) surfaces represent a prominent example of the atomic-scale 1D metallic nanowires. A monolayer of In on Si(111) allocates in In chains on the Si surfaces extending along the [1–10] direction. The In chains are a prototype example of a 1D metallic conductor at room temperature which undergoes a Peierls transition into an insulating state at low temperature [01H1]. A commonly accepted structural model has been established by experiment and theory for the room temperature phase of the In nanowire structure showing a (4 × 1) surface reconstruction. It consists of a double row of two In zigzag chains separated by a Si zigzag chain in between, resembling the π-bonded chains of the clean Si(111)(2 × 1) surface.
When the system is cooled to about 120 K, the In/Si(111) surface undergoes a phase transition into an (8 × 2) structure. Upon this phase transition, the In atoms within the double row of zigzag chains rearrange into a hexagon-like arrangement and the whole structure becomes insulating [09C]. The transition being related with a change of the 1D metallic (4 × 1) into an insulating state for the (8 × 2) structures has been associated with a first-order Peierls transition. The displacive transition between two distinct geometrical structures is associated with a charge density wave formation [10W].
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