A Single-Atom-Thick TiO2 Nanomesh on an Insulating Oxide.
The electronic structures and macroscopic functionalities of two-dimensional (2D) materials are often controlled according to their size, atomic structures, and associated defects. This controllability is particularly important in ultrathin 2D nanosheets of transition-metal oxides because these materials exhibit extraordinary multifunctionalities that cannot be realized in their bulk constituents. To expand the variety of materials with exotic properties that can be used in 2D transition-metal-oxide nanosheets, it is essential to investigate fabrication processes for 2D materials. However, it remains challenging to fabricate such 2D nanosheets, as they are often forbidden because of the crystal structure and nature of their host oxides. In this study, we demonstrate the synthesis of a single-atom-thick TiO2 2D nanosheet with a periodic array of holes, that is, a TiO2 nanomesh, by depositing a LaAlO3 thin film on a SrTiO3(001)-(√13×√13)-R33.7° reconstructed substrate. In-depth investigations of the detailed structures, local density of states, and Ti valency of the TiO2 nanomesh using scanning tunneling microscopy/spectroscopy, scanning transmission electron microscopy, and density functional theory calculations reveal an unexpected upward migration of the Ti atoms of the substrate surface onto the LaAlO3 surface. These results indicate that the truncated TiO5 octahedra on the surface of perovskite oxides are very stable, leading to semiconducting TiO2 nanomesh formation. This nanomesh material can be potentially used to control the physical and chemical properties of the surfaces of perovskite oxides. Furthermore, this study provides an avenue for building functional atomic-scale oxide 2D structures and reveals the thin-film growth processes of complex oxides.
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.|National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba 305-0044, Japan.
Takeo
T
Ohsawa
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.|Institute of Engineering Innovation, The University of Tokyo , Tokyo, 113-8656, Japan.
Mitsuhiro
M
Saito
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.|National Institute for Materials Science (NIMS) , 1-1 Namiki, Tsukuba 305-0044, Japan.
Ikutaro
I
Hamada
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.
Ryota
R
Shimizu
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.
Katsuya
K
Iwaya
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.
Susumu
S
Shiraki
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.
Zhongchang
Z
Wang
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.|Institute of Engineering Innovation, The University of Tokyo , Tokyo, 113-8656, Japan.|Nanostructures Research Laboratory, Japan Fine Ceramics Center , Nagoya, 456-8587, Japan.
Yuichi
Y
Ikuhara
Advanced Institute for Materials Research (AIMR), Tohoku University , Sendai 980-8577, Japan.|PRESTO, Japan Science and Technology Agency , Tokyo 102-0076, Japan.
Taro
T
Hitosugi
lanthanum aluminate; scanning tunneling microscopy; strontium titanate; transition metal oxides; two-dimensional sheets