Structure determination of the rutile-TiO₂(110)-(1 × 2) surface using total-reflection high-energy positron diffraction (TRHEPD)

Abstract

The exact structure of the rutile-TiO2(110)-(1 × 2) surface, which had been under debate over the past 30 years, was investigated using the newly developed technique of total-reflection high-energy positron diffraction (TRHEPD), which is a positron counterpart of reflection high-energy electron diffraction (RHEED). The rocking-curves for the 00-spot obtained from the experimental diffraction patterns were compared to the curves for various models calculated with a full-dynamical theory. It was found that the rocking-curves matched those for a surface consisting of a Ti2O3 configuration, originally suggested by Onishi and Iwasawa [H. Onishi and Y. Iwasawa, Surf. Sci., 1994, 313, L783], but with a further modification of atomic positions close to the ones proposed by Wang et al. [Q. Wang, A. R. Oganov, Q. Zhu and X. F. Zhou, Phys. Rev. Lett., 2014, 113, 266101]. This result demonstrates that TRHEPD can distinguish between the existence and absence of the oxygen atoms on the topmost surface, and between the Ti atoms residing in positions at the interstitial-vertical sites and those at interstitial-horizontal sites.

Polaron-Driven Surface Reconstructions

“…This phase separation into (1 × 1) and (1 × [4], recently refined by Wang et al [37] via DFT-based genetic algorithms, and supported by total-reflection high-energy positron diffraction studies [38]. Here, the stripes have a Ti 2 O 3 stoichiometry; i.e., their composition can be viewed as Ti 2 O 4 with 50% of V O 's.…”

“…Each V O supplies two excess electrons, which form two polarons. The (1 × 2) phase was constructed according to the Ti 2 O 3 model [4,37,38] by placing the reconstructed row on top of the five layers, which gives rise to two polarons per (1 × 2) unit cell.…”

“…This imaging mode is particularly valuable on the (1 × 2) reconstruction [Fig. 1(i)], where the structural model is still under debate[4,37,38,[47][48][49][50]. AFM allows a precise measurement of the positions of the surface O atoms in the x-y plane, which helps us exclude most of the proposed structures.…”

Structure of superconducting Ca-intercalated bilayer Graphene/SiC studied using total-reflection high-energy positron diffraction

“…3 are the raw experimental rocking-curves and the calculated rocking curves which were corrected for the effective sample size by the multiplying with sin θ (θ is the glancing angle). This analysis yielded the interlayer distances with their associated error values [27]. In the case of pristine bilayer graphene [ Fig.…”

Slow positron applications at slow positron facility of institute of materials structure science, KEK

“…Recently, TRHEPD has determined the structure of the rutile-TiO 2 (110) (1×2) surface 14 , which had been under debate over the past 35 years. TiO 2 is a well-known catalyst used in a variety of applications including photocatalysis, metal-nanoparticle catalyst supports, gas sensors and corrosion-protective coating materials 15,16 .…”