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Initial oxidation processes of ultrathin hafnium film and hafnium disilicide islands on Si(100)-2$$times$$1 surfaces studied using core-level X-ray photoelectron spectroscopy

Kakiuchi, Takuhiro*; Yamasaki, Hideki*; Tsukada, Chie*; Yoshigoe, Akitaka 

We investigated the initial oxidation of ultrathin hafnium (Hf) film on Si(100)-2$$times$$1 using photoelectron spectroscopy. Metallic Hf rapidly oxidized, transforming into hafnium dioxide (HfO$$_{2}$$) and its suboxides. The other HfSi component at the interface was nearly unreactive with O$$_{2}$$ molecules. These facts suggest that the metallic Hf component plays a vital role in the initial oxidation of the ultrathin Hf/Si(100) film. After annealing from 873 K to 973 K, the Hf suboxides in low ionic valences progressed into fully oxidized HfO$$_{2}$$. Once the annealing temperature reached c.a.1073 K, oxygen atoms were entirely removed from the ultrathin HfO$$_{2}$$/Si(100) film containing SiO$$_{2}$$ at the interface. Simultaneously, ultrathin HfO$$_{2}$$ layers changed into islands of Hf disilicide ($$i$$-HfSi$$_{2}$$) on a bare Si(100)-2$$times$$1 surface. The $$i$$-HfSi$$_{2}$$ component showed slight reactivity with O$$_{2}$$ molecules at 298 K. In contrast to the initial oxidation of clean Si(100)-2$$times$$1 surface, the dangling bonds on bare Si(100)-2$$times$$1 surface among $$i$$-HfSi$$_{2}$$ oxidized preferentially.



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Category:Chemistry, Physical



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