STM and RHEED study of the Si(001)-c(8x8) surface

TL;DR

This study uses STM and RHEED to investigate the Si(001) surface's structural reconstructions during annealing, revealing reversible (4x4) and (2x1) structures and identifying the c(8x8) reconstruction's formation and characteristics.

Contribution

The paper provides in situ STM and RHEED analysis of the Si(001) surface, revealing the formation and reversible nature of high-order reconstructions like c(8x8) during annealing.

Findings

c(8x8) structure identified on Si(001) surface at room temperature

Reversible transition between (2x1) and (4x4) structures with temperature changes

c(8x8) manifests as (4x4) in RHEED patterns

Abstract

The Si(001) surface deoxidized by short annealing at T~925C in the ultrahigh vacuum molecular beam epitaxy chamber has been in situ investigated by high resolution scanning tunnelling microscopy (STM) and reflected high energy electron diffraction (RHEED). RHEED patterns corresponding to (2x1) and (4x4) structures were observed during sample treatment. The (4x4) reconstruction arose at T<600C after annealing. The reconstruction was observed to be reversible: the (4x4) structure turned into the (2x1) one at T>600C, the (4x4) structure appeared again at recurring cooling. The c(8x8) reconstruction was revealed by STM at room temperature on the same samples. A fraction of the surface area covered by the c(8x8) structure decreased as the sample cooling rate was reduced. The (2x1) structure was observed on the surface free of the c(8x8) one. The c(8x8) structure has been evidenced to manifest itself as the (4x4) one in the RHEED patterns. A model of the c(8x8) structure formation has been built on the basis of the STM data. Origin of the high-order structure on the Si(001) surface and its connection with the epinucleation phenomenon are discussed.