Coverage of the 7x7 reconstructed region on quenched Si(111) surfaces has been compared for two types of Si wafers with different oxygen concentration, CZ and modified-FZ (m-FZ) wafers. The m-FZ wafer clearly showed the lower coverage, which suggested that oxygen had some influence on the formation of 7x7 structure. The activation energy of formation of the 7x7 structure has been estimated to be 2.4 eV.
Cooling rate dependence of the 7x7 coverage on the surfaces of CZ-Si(111) (○) and the m-FZ-Si(111) (●). The length of the error bars mean the standard deviation.