557-pasquarello-prb-1996-10942 - PHYSICAL REVIEW B VOLUME...

Info iconThis preview shows pages 1–2. Sign up to view the full content.

View Full Document Right Arrow Icon
Theory of Si 2 p core-level shifts at the Si 001 -SiO 2 interface Alfredo Pasquarello Institut Romand de Recherche Nume ´rique en Physique des Mate ´riaux (IRRMA), IN-Ecublens, CH-1015 Lausanne, Switzerland and AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey 07974 Mark S. Hybertsen AT&T Bell Laboratories, 600 Mountain Avenue, Murray Hill, New Jersey 07974 Roberto Car Institut Romand de Recherche Nume ´rique en Physique des Mate ´riaux (IRRMA), IN-Ecublens, CH-1015 Lausanne, Switzerland and Department of Condensed Matter Physics, University of Geneva, CH-1211 Geneva, Switzerland ~ Received 18 December 1995 ! A first-principles investigation of Si 2 p core-level shifts at the Si ~ 001 ! -SiO 2 interface is presented. We introduce several relaxed interface models obtained by attaching different crystalline forms of SiO 2 to Si ~ 001 ! . These model structures contain the minimal transition region required to accommodate the three intermediate oxidation states of silicon, in accord with photoemission experiments. The bond density mismatch is fixed by saturating all the bonds, as required by electrical measurements. Calculated core shifts are primarily affected by the number of nearest-neighbor oxygen atoms, showing a linear dependence. This result confirms the tradi- tional interpretation of the photoemission spectra based on a charge-transfer model. Core relaxation plays a significant role accounting for more than 50% of the total shifts. The shifts are found to be essentially insensitive to second and further neighbors in the structure. Structural deformations, such as those implied by the distribution of Si-O bond lengths in a -SiO 2 , yield distributions of core-level shifts that are too small to account for the observed width of the photoemission peaks. In the oxide, we observe a spatial dependence of the Si 1 4 shifts with distance from the interface plane. We relate this behavior to the dielectric discontinuity at the interface and suggest that this effect explains the shift of the Si 1 4 with oxide thickness, observed in photoemission experiments. I. INTRODUCTION Despite the use of a large variety of experimental techniques, 1–3 the combined effect of a few factors, such as the difficulty of accessing a buried interface, the amorphous nature of the SiO 2 component, and the dependence on sample preparation techniques, have so far prevented a com- plete description of the structural properties at the Si ~ 001 ! - SiO 2 interface. However, the crucial role of this interface in silicon-based technology, with the present program of device development requiring highly uniform SiO 2 films of less than 100 Å on Si, calls for a better understanding at the microscopic level. Among the various experimental techniques, core-level ~ Si 2 p ) photoelectron spectroscopy ~ PES ! stands out as one of the most successful tools of investigation of the Si ~ 001 ! - SiO 2 interface.
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
Image of page 2
This is the end of the preview. Sign up to access the rest of the document.

This note was uploaded on 12/10/2009 for the course IF PFIS1200 taught by Professor Antonio during the Spring '09 term at Universidade Federal do Rio de Janeiro.

Page1 / 9

557-pasquarello-prb-1996-10942 - PHYSICAL REVIEW B VOLUME...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online