Phase transition from Langmuir-type adsorption to two-dimensional oxide island growth during oxidation on Si(0 0 1) surface

• Published in: Applied surface science 2003-06, Vol.216 (1), p.133-140
• Main Authors: Takakuwa, Yuji, Ishida, Fumiaki, Kawawa, Takuo
• Format: Article
• Language: English
• Subjects: Auger electron spectroscopy; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Materials science; Oxidation; Phase transitions and critical phenomena; Physics; Real-time monitoring; Reflection high-energy electron diffraction (RHEED); Silicon; Solid surfaces and solid-solid interfaces; Surface chemical reaction; Surface treatments; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/S0169-4332(03)00501-4

The phase transition from Langmuir-type adsorption to two-dimensional (2D) oxide island growth during initial oxidation on the Si(0 0 1) surface was investigated by real-time Auger electron spectroscopy (AES) combined with reflection high-energy electron diffraction (RHEED). Curve-fitting analysis of the oxygen uptake curve obtained by O-KLL Auger electron intensity revealed that the phase transition occurs steeply at ∼630 °C and no oxidation occurs after completion of 2D growth of oxide islands, whereas oxides grows gradually at the interface following Langmuir-type adsorption. It was observed that the very thin oxide layer grown at 616 °C is more easily decomposed than that grown at 653 °C in spite of almost the same thickness. Furthermore, the RHEED intensity ratio between half-order spots indicated that etching of the surface starts suddenly just at the phase transition temperature of ∼630 °C. The steepness of the phase transition, the sudden start of SiO desorption and the difference in the interfacial oxidation and decomposition between two oxidation schemes are comprehensively interpreted using a surface reaction model in which O 2 adsorption on the Si(0 0 1) 2×1 surface changes drastically from barrier-less adsorption into dimer backbonds for Langmuir-type adsorption to formation of desorption precursor SiO ∗ in pairs with dimer vacancies for 2D oxide island growth, and coalescence of SiO ∗ leads to nucleation and 2D growth of oxide islands.