Large in-plane vibrational and optical anisotropy in natural 2D heterostructure abramovite.

The design and formation of van der Waals (vdW) heterostructures with different two-dimensional (2D) materials provide an opportunity to create materials with extraordinary physical properties tailored toward specific applications. Mechanical exfoliation of natural vdW materials has been recognized as an effective way for producing high-quality ultrathin vdW heterostructures. Abramovite is one of such naturally occurring vdW materials, where the superlattice is composed of alternating PbBiS and SnInS 2D material lattices.

Reorientation kinetics of hydroxyl groups in anatase TiO.

The reorientation kinetics of hydrogen in a variety of complexes in the anatase polymorph of TiO was investigated by means of stress-induced dichroism. For the hydrogen-defect resulting in an O-H vibrational mode with a frequency of 3389 cm, the energy barrier separating adjacent equivalent in-plane sites of hydrogen was determined to be independent of the isotope and equal to 0.74 ± 0.

Hydrogen motion in rutile TiO.

Uniaxial-stress experiments have been performed for the 3287- and 2445-cm local vibrational modes assigned to the positive charge state of interstitial hydrogen [Formula: see text] and deuterium [Formula: see text], respectively, occurring in mono-crystalline rutile TiO2. The onset of the defect alignment under the stress applied perpendicular to the [001] axis is detected at 165 K (185 K), which corresponds to the activation energy of 0.53 eV (0.