Surface morphology of SiO₂ on a Si(111) 7×7 surface formed after alternating exposure to caesium and oxygen and subsequent annealing

The features of Cs enhanced oxidation of silicon is studied with the quases-Tougaard method. It is found that Cs oxide forms islands on the Si(111) 7×7 surface for exposure up to eight cycles (1 cycle=1 ML Cs+100 L O₂). These islands in turn form islands of SiO₂ on the surface after annealing. The surface coverage of Cs-oxide islands and silicon-oxide islands is found to be the same. At higher (≥10 cycles) exposures, the Cs oxide as well as the SiO₂2 layer covers the surface completely. It is also shown, that the catalytic effect of Cs is local and that the amount of produced SiO₂2 is directly proportional to the amount of Cs.