Si atom density of the Si(111)-(5×2)-Au surface: STM study

Two types of the (5×2) domain, island and depression, have been observed by depositing Au onto a Si(111)-(7×7) surface. For Au deposition performed at room temperature followed by heating, in addition to the (5×2) areal density being consistent with the Au coverage, both the number and areal densities of the (5×2) domain in regions far from steps are independent of heating temperature, indicating that the total number of Si atoms participating in the (7×7) to (5×2) transition is conserved. This, however, is not the case for deposition performed on surfaces at elevated temperatures. From the areal ratio of the two types of the (5×2) domain, we determine that the number of Si atoms in a (5×2) unit cell is 13±1.