Mechanism of creation and destruction of oxygen interstitial atoms by nonpolar zinc oxide(101̄0) surfaces

Ertekin

ACS Appl. Mater. Interfaces

2022

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Initial synthesis of semiconducting oxides leaves behind poorly controlled concentrations of unwanted atomic-scale defects that influence numerous electrical, optical, and reactivity properties. We have discovered through self-diffusion measurements and first-principles computations that poison-free oxide surfaces inject interstitial oxygen atoms into the crystalline solid when simply contacted with liquid water near room temperature. These interstitials diffuse quickly to depths of 20 nm–2 μm and are likely to eliminate prominent classes of unwanted defects or neutralize their action. The mild conditions of operation access a regime for oxide fabrication that relaxes important thermodynamic constraints that hamper defect regulation by conventional methods at higher temperatures. The surface-based approach appears well-suited for use with nanoparticles, porous oxides, and thin films for applications in advanced electronics, renewable energy storage, photocatalysis, and photoelectrochemistry.

“…The spring constant was set to −5 eV Å –1 . Prior publications have detailed other specifications for surface models of ZnO and TiO 2 ; the same procedures were employed here.…”

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Surface-Based Post-synthesis Manipulation of Point Defects in Metal Oxides Using Liquid Water

Ertekin

ACS Appl. Mater. Interfaces

2022

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Effects of Ultraviolet Illumination on Oxygen Interstitial Injection from TiO₂ under Liquid Water

2022

J. Phys. Chem. C

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Super-band-gap illumination influences the reaction rates of semiconducting oxide surfaces with gases and liquids, so it seems plausible that illumination also affects the analogous rates of surfaces with point defects in the interior of the solid. However, such effects have not been investigated. The present paper fills that gap by employing isotopic self-diffusion measurements to demonstrate ultraviolet-enhanced creation of oxygen interstitial atoms from rutile TiO 2 (110) surfaces exposed to liquid water. Illumination affects both the injection rate and the mean diffusion length into the solid, although by different mechanisms. These effects offer a new means to enhance post-synthesis defect tailoring via oxide surfaces.

Strong Isotopic Fractionation of Oxygen in TiO₂ Obtained by Surface-Enhanced Solid-State Diffusion

2022

J. Phys. Chem. Lett.

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Isotopically pure semiconductors have important applications for cooling electronic devices and quantum computing and sensing. Raw materials of sufficiently high isotopic purity are expensive and difficult to obtain; therefore, a post-synthesis method for removing isotopic impurities would be valuable. Through isotopic self-diffusion measurements of oxygen in rutile TiO2 single crystals immersed in water, we demonstrate fractionation of 18O by a factor of 3 below natural abundance in a near-surface region up to 10 nm wide. The submerged surface injects O interstitials that displace lattice 18O deeper into the solid as a result of the statistics of interstitialcy-mediated diffusion combined with steep chemical gradients of O interstitials. Slightly acidic and slightly basic liquid solutions both enhance the fractionation and affect the details of isotopic profile shapes through several chemical and physical mechanisms.