Phase transition between (2 × 1) and c(8 × 8) reconstructions observed on the Si(001) surface around 600°C

The Si(001) surface subjected to different treatments in ultrahigh vacuum molecular beam epitaxy chamber for SiO 2 film decomposition has been in situ investigated by reflected high energy electron diffraction (RHEED) and high resolution scanning tunneling microscopy (STM). A transition between (2 × 1) and (4 × 4) RHEED patterns was observed. The (4 × 4) pattern arose at T ≤ 600°C during the post-treatment cooling of the sample. The reconstruction was observed to be reversible. The c (8 × 8) structure has been revealed by STM at room temperature on the same samples. The (4 × 4) patterns have been evidenced to be a manifestation of the c (8 × 8) surface structure in RHEED. The phase transition appearance has been found to depend on thermal treatment conditions and sample cooling rate.