DIET in the bulk: Evidence for hot electron cleavage of Si-H bonds in SiO2 films

D. R. Jennison, J. P. Sullivan, P. A. Schultz, M. P. Sears, E. B. Stechel

Research output: Contribution to journalArticle

10 Citations (Scopus)

Abstract

The observed increase in leakage current through SiO2 films after hot electron exposure is ascribed to dissociation induced by electronic transitions ("DIET") of bulk Si-H bonds, producing mobile hydrogen. We use ab initio supercell bandstructure calculations at the local density functional level to locate features produced by hydrogen-containing defects in α-SiO2. The edge of the Si-H σ* resonance is found to be about 2.7 eV above the conduction band rise, in good agreement with the observed threshold for hot electron induced damage in amorphous SiO2 films grown on Si substrates. The O-H σ* resonance is almost 4 eV higher. Removing H from O-H in the supercell does not affect the gap region (-O- forms); however, removing H from Si-H produces a mid-gap state, suggesting leakage current by hopping conductivity between Si dangling bonds. A Morse potential model is used to explore the dynamics of bond scission by short-lived (< 1 fs) hot electron σ* capture. Supercell calculations on interstitial atomic hydrogen indicate the energy cost to break an embedded Si-H bond is about 0.6 eV less than in the gas phase. The DIET yield is substantially increased by reducing both ground and electron-attached state binding by this amount. While uncertainty over the displaced equilibrium in the electron-attached excited state remains, the computed DIET cross-section for reasonable parameters is ≈ 10-18 cm2, and is in agreement with the semi-empirically derived value for trap creation. Comparisons are made to surface DIET processes involving Si-H bonds.

Original languageEnglish
Pages (from-to)112-118
Number of pages7
JournalSurface Science
Volume390
Issue number1-3
DOIs
Publication statusPublished - Nov 18 1997

Keywords

  • Amorphous thin films
  • Atomistic dynamics
  • Density functional calculations
  • Electron-solid interactions
  • Electron-stimulated desorption
  • Silicon oxides

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Surfaces and Interfaces
  • Surfaces, Coatings and Films
  • Materials Chemistry

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