The nature of the silicon oxide transition region in the vicinity of the Si/SiO2 interface is probed by infrared and x-ray photoelectron spectroscopies. The layer-by-layer composition of the interface is evaluated by uniformly thinning thermal oxide films from 31 Å down to 6 Å. We find that the thickness dependence of the frequencies of the transverse optical and longitudinal optical phonons of the oxide film cannot be reconciled by consideration of simple homogeneous processes such as image charge effects or stress near the interface. Rather, by applying the Bruggeman effective medium approximation, we show that film inhomogeneity in the form of substoichiometric silicon oxide species accounts for the observed spectral changes as the interface is approached. The presence of such substoichiometric oxide species is supported by the thickness dependence of the integrated Si suboxide signal in companion x-ray photoelectron spectra.

We report on growth and characterization of both epitaxial and amorphous films Gd2O3 of (ε=14) and Y2O3(ε=18) as the gate dielectrics for Si prepared by ultrahigh vacuum vapor deposition. The use of vicinal Si (100) substrates is key to the growth of (110) oriented, single-domain films in the Mn2O3 structure. Typical electrical leakage results are 10−3 A/cm2 at 1 V for single domain epitaxial Gd2O3 and Y2O3 films with an equivalent SiO2 thickness, teq of 15 Å, and 10−6 A/cm2 at 1 V for smooth amorphous Y2O3 films (ε=18) with a teq of only 10 Å. For all the Gd2O3 films, the absence of SiO2 segregation at the interface is established from infrared absorption measurements.

The dissociation of NH3 on Si(100)-(2x1) is investigated by a combination of infrared absorption spectroscopy and density functional cluster calculations, revealing that this reaction is governed by a complex set of interdimer interactions involving both bare and adsorbate-covered Si dimers. We propose that such adsorbate-induced changes in the electronic structure of neighboring dimers may have general implications for controlling the two-dimensional ordering of reactions on the dimerized Si(100) surface.

Articles you may be interested inThe thermal chemistry of saturated layers of acetylene and ethylene on Ni(100) studied by in situ synchrotron xray photoelectron spectroscopy Surface infrared spectroscopy and density functional cluster calculations are used to study the thermal and atomic hydrogen-induced decomposition of water molecules on the clean Si͑100͒-͑2ϫ1͒ surface. We report the first observation of the Si-H bending modes associated with the initial insertion of oxygen into the dimer and backbonds of a silicon dimer. We find that, while one and two oxygen-containing dimers are formed almost simultaneously during the thermal decomposition of water on this surface, atomic H can be used to drive the preferential formation of the singly oxidized dimer. This work highlights the sensitivity of Si-H bending modes to the details of local chemical structure in an inhomogeneous system, suggesting that the combined experimental and theoretical approach demonstrated herein may be extremely useful in studying even more complex systems such as the hydrogenation of defects in SiO 2 films.

Articles you may be interested inGrowth of silicon quantum dots by oxidation of the silicon nanocrystals embedded within silicon carbide matrix AIP Advances 4, 107106 (2014); 10.1063/1.4897378 Mechanistic and kinetic study of the CH 3 CO + O 2 reaction Effect of oxygen precipitates and induced dislocations on oxidation-induced stacking faults in nitrogen-doped Czochralski silicon J. Appl. Phys. 96, 3031 (2004); 10.1063/1.1777804Oxidation study of plasma-enhanced chemical vapor deposited and rf sputtered hydrogenated amorphous silicon carbide filmsThe microscopic mechanism of the formation of ultrathin oxides on Si͑100͒ has been investigated using a combination of infrared spectroscopy and ab initio quantum chemical cluster calculations. The 0˜2 monolayer oxide films are grown sequentially from the ''bottom-up'' using repeated water exposures and annealing cycles, with the partial pressure of water ranging from 10 Ϫ10 to 10 Torr. The resultant films were then compared to the equivalent thicknesses of thermal and native oxide films. In this way, we obtain unprecedented insight into the essential chemical structures formed during the initial oxidation and subsequent layer growth of these technologically relevant films.