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

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

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.

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

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.