Self-Adaptation of Oxygen Adsorption and Sub-Surface Junction Formation in Thin Nanometric Sheets of Metal Oxides

Gerhard Müller, Giorgio Sberveglieri

Research output: Contribution to journalArticlepeer-review

Abstract

Oxygen adsorption at metal oxide (MOX) surfaces and the formation of sub-surface depletion zones in thin nanometric sheets of MOX materials are theoretically investigated. It is shown that—under conditions of sufficient oxygen mobility—the bulk thermal generation of oxygen vacancy donors and the adsorption of surface oxygen ions cooperate in a self-organizing manner to form narrow sub-surface depletion zones which optimally fit into the limited spaces of MOX layers with nanometric cross sections. With this self-organization process in place, both the oxygen adsorption at free surfaces and the bulk generation of oxygen vacancy donors continuously increases as the MOX sheet thickness L is reduced, maintaining at the same time overall electro-neutrality and a state of perfect volume depletion of free carriers in bulk. This process comes to an end when MOX sheet thicknesses of L ≈ 1 nm are approached and when 3d-volumes of about 1 nm3 contain only one single double-donor and two surface oxygen ions on average. It is argued that at this limit of miniaturization, different interpretations of MOX gas sensing phenomena might be required than on larger length scales.

Original languageEnglish
Article number352
JournalChemosensors
Volume11
Issue number6
DOIs
StatePublished - Jun 2023
Externally publishedYes

Keywords

  • defect equilibration
  • gas sensitivity
  • limits of miniaturization
  • metal oxide gas sensor
  • minimum grain size
  • nanostructures
  • oxygen adsorption
  • oxygen vacancy donors
  • sub-surface junction formation

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