Dynamics of Hydrogen in Silicon at Finite Temperatures from First Principles

Diana Gomes, Vladimir P. Markevich, Anthony R. Peaker, José Coutinho

Research output: Contribution to journalArticlepeer-review

Abstract

Hydrogen defects in silicon still hold unsolved problems, whose disclosure is fundamental for future advances in Si technologies. Among the open issues is the mechanism for the condensation of atomic hydrogen into molecules in Si quenched from above (Formula presented.) to room temperature. Based on first-principles calculations, the thermodynamics of hydrogen monomers and dimers is investigated at finite temperatures within the harmonic approximation. Free energies of formation indicate that the population of (Formula presented.) cannot be neglected when compared to that of (Formula presented.) at high temperatures. The results allow us to propose that molecular formation occurs during cooling processes, in the temperature window (Formula presented.), above which the molecules collide with Si—Si bonds and dissociate, and below which the fraction of (Formula presented.) becomes negligible. The formation of (Formula presented.) and most notably of a fast-diffusing neutral species can also provide an explanation for the apparent accelerated diffusivity of atomic hydrogen at elevated temperatures in comparison to the figures extrapolated from measurements carried out at cryogenic temperatures. Finally, it is shown that the observed diffusivity of molecules is better described upon the assumption that they are nearly free rotors, all along the migration path, including at the transition state.

Original languageEnglish
JournalPhysica Status Solidi (B) Basic Research
DOIs
Publication statusPublished - 16 Mar 2022

Keywords

  • defects
  • hydrogen
  • molecules
  • silicon
  • thermodynamics

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