Oxidation of hydrogen terminated Ge(1 0 0) surface in the presence of iodine in methanol

Surface reaction on Ge(1 0 0) in liquid methanol (MeOH) was systematically studied. In particular, the characteristics of the Ge surface in the presence of iodine (I2) in MeOH were investigated. MeOH treatment of the Ge surface in the presence of 0.05 or 0.005 mM of I2 exhibited a similar result to that without I2, which produces a GeOx-dominant oxide structure. However, when the concentration of I2 in MeOH increased to 0.5 mM, Ge surface revealed a GeO2-dominant oxide structure. Therefore, it is believed that the addition of enough I2 in MeOH modifies the Ge oxidation mechanism. Hydroxide produced by the reaction between MeOH and the iodine radical may oxidize the Ge surface to form a Ge–O layer. Because MeOH is greatly consumed by chain and series reactions when I2 concentration is high, a GeO2 structure is not etched and a GeO2-dominant oxide structure is obtained with the addition of 0.5 mM I2 in MeOH. The modified oxide layer prepared in MeOH with 0.5 mM I2 exhibited an atomically smoother surface compared to a pure MeOH- or H2O2-treated Ge surface and a much thinner oxide layer than H2O2 treatment.