Real-time observation of the dry oxidation of the Si (100) surface with ambient … (original) (raw)
Related papers
Journal of Applied Physics, 2008
The initial stages of wet thermal oxidation of Si͑100͒ − ͑2 ϫ 1͒ have been investigated by in situ ambient pressure x-ray photoemission spectroscopy, including chemical-state resolution via Si 2p core-level spectra. Real-time growth rates of silicon dioxide have been monitored at 100 mTorr of water vapor. This pressure is considerably higher than in any prior study using x-ray photoemission spectroscopy. Substrate temperatures have been varied between 250 and 500°C. Above a temperature of ϳ400°C, two distinct regimes, a rapid and a quasisaturated one, are identified, and growth rates show a strong temperature dependence which cannot be explained by the conventional Deal-Grove model.
Japanese Journal of Applied Physics, 2007
High-resolution O 1s and Si 2p photoelectron spectroscopy using synchrotron radiation was employed to clarify a layer-bylayer oxidation reaction mechanism on a Si(001) surface from the viewpoint of point defect generation due to an oxidationinduced strain at a SiO 2 /Si interface. The Si and Si components in Si 2p 3=2 spectra, which are assigned to the first and second strained Si layers, respectively, below the transition layer composed of suboxides, Si 1þ , Si 2þ , and Si 3þ , significantly decrease during the step-by-step temperature increase-enhanced growth of the second oxide layer. Because of the corresponding band bending changes measured using the O 1s peak position, which are caused by defect-related band gap states, the observed decreases in Si and Si components, indicating a decrease in interfacial strain, are induced not only by the structural relaxation of a SiO 2 network due to a thermal annealing effect, but also due to the generation of point defects at the SiO 2 /Si interface. Continuous band bending changes with the growth of the third oxide layer also suggest that the point defects are generated during oxide growth, whereas the Si and Si components are maintained almost constant. On the basis of the observed interfacial strain and point defect generation changes, the layer-by-layer growth kinetics of the first, second and third oxide layers is discussed using a unified Si oxidation reaction model mediated by point defect generation at the SiO 2 /Si interface [S.
Applied Surface Science, 2003
The initial oxidation on a Si(110)-16 Â 2 surface at room temperature and 540 C has been investigated by real-time X-ray photoemission spectroscopy (O 1s) using 687 eV photons. At both temperatures, the initial oxidation of Si(110) is characterized by its unique rapid oxidation regime immediately after the introduction of oxygen molecules. O 1s spectra are shown to consist of at least four oxidation states. It is likely that oxidation at or around the adatoms of pentagon pairs, reportedly present on the Si(110)-16 Â 2 reconstructed surface, is the predominant process in the very early stage of oxidation.
All-optical determination of initial oxidation of Si(100) and its kinetics
The European Physical Journal B, 2008
By comparison of measured and ab initio calculated surface optical spectra we demonstrate that two main oxidation processes initially occur after dissociation of oxygen molecules, forming in both cases Si-O-Si entities: (i) breaking of Si dimers by incorporation of oxygen atoms; (ii) incorporation into the silicon backbonds. The kinetics up to half-monolayer coverage is determined, and explained in terms of Langmuir-like adsorption mechanisms with different probabilities.
Physical Review B, 2009
We have investigated the first stages of the room-temperature oxidation of the Si͑100͒ surface combining experimental surface optical spectra with the results of ab initio calculations. High-resolution reflectance anisotropy spectra ͑RAS͒ and surface differential reflectance spectra ͑SDRS͒ have been measured for the clean surfaces and various exposures up to 183 L, which have been compared with calculated RAS and SDRS in the independent-particle approximation. Our results, yielding a consistent description of both RAS and SDRS, suggest the coexistence of different structural domains, whose weight changes smoothly with the oxygen exposure. The main oxidation mechanisms together with their occurrence versus coverage are discussed.
The Journal of Chemical Physics, 2007
First principles calculations and scanning tunneling microscopy studies of the oxidation of Si͑100͒-͑2 ϫ 1͒ surfaces by molecular oxygen reveal that the surface silanone ͑O͒͑Siv O͒ species is remarkably stable, constituting the key intermediate for initial oxidation. The propensity for oxygen to remain within the top surface layer as opposed to incorporating within Si-Si backbonds is surprisingly high. This resistance to incorporation into a cubic lattice even at higher coverages could be a factor to facilitate surface amorphization in subsequent steps.
The initial stages of the oxidation of Si(100)2 x 1 studied by STM
Ultramicroscopy, 1992
The initial stages of the oxidation of the Si(100)2x 1 surface was studied at room temperature by scanning tunneling microscopy (STM). We found that "type-C defects" which are believed to be two half-dimers have a strong preference for oxidation, compared with areas having no defects. Oxidized type-C defects appear to be depressions in both positive and negative sample bias voltages. We also found two oxidized sites having no defects. Single steps are quite stable against oxidation. The oxidation of the Si(100)2 x 1 surface is discussed in terms of these sites.
Microscopic mechanisms of initial oxidation of Si(100): Reaction pathways and free-energy barriers
Physical Review B, 2012
Various reaction pathways and corresponding activation barriers in the initial oxidation of Si(100) surfaces are clarified by free-energy sampling techniques combined with the Car-Parrinello molecular dynamics. We find a crucial stable geometry which is ubiquitous during the oxidation and links the dissociation of O 2 molecules and the oxidation of subsurfaces. The calculated free-energy landscape provides a comprehensive picture of the various competing reaction pathways.