Thermal decomposition reaction mechanism of ultrathin oxide on Si(111)

Tang, J.*; Ogawa, Shuichi*; Yoshigoe, Akitaka ; Nishimoto, Kiwamu*; Ishizuka, Shinji*; Teraoka, Yuden; Takakuwa, Yuji*

The decomposition kinetics of ultrathin oxide on Si(111) have been investigated by real-time photoelectron spectroscopy using He-I resonance line and synchrotron radiation to clarify the void nucleation and its 2D enlargement mechanism. The oxidized Si(111) surface prepared by exposing O at 773 K under P=4.610 Pa was decomposed by increasing T. The O2p photoelectron intensity I shows a sigmoid-type function. The activation energies are almost the same as 2.8-2.9 eV, suggesting that the rate-limiting step is SiO desorption. The correlation between changes of work function and I was measured to consider the surface migrating species. The dependences of the oxidation state and oxidation-induced strain were monitored during the decomposition. Based on the observed results, the oxide decomposition mechanism is discussed in terms of Si atoms supplied from atomic steps within voids and due to point defect generation at oxide/Si(111) interface.