Hydrogen motion in rutile TiO₂

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• Interstitial hydrogen and deuterium are crucial defects in rutile titanium dioxide (TiO2).
• Understanding their diffusion mechanisms is vital for semiconductor applications.

Purpose of the Study:

• To investigate the diffusion of interstitial hydrogen ([H]) and deuterium ([D]) in mono-crystalline rutile TiO2.
• To determine the activation energies and diffusion constants for [H] and [D] along the [001] axis.

Main Methods:

• Uniaxial-stress experiments were conducted on rutile TiO2.
• Local vibrational modes were analyzed to detect defect alignment.
• Density-functional theory (DFT) calculations complemented experimental data.

Main Results:

• The onset of defect alignment for [H] and [D] occurred at 165 K and 185 K, respectively.
• Activation energies were determined as 0.53 eV for [H] and 0.58 eV for [D].
• Experimental diffusion constants showed excellent agreement with DFT calculations and high-temperature data.

Conclusions:

• Low-temperature stress measurements provide accurate activation energies for interstitial hydrogen and deuterium diffusion.
• The determined diffusion constants are valid over 12 orders of magnitude.
• This study enhances the understanding of hydrogen/deuterium behavior in TiO2 for materials science applications.