Thickness-Insensitive Properties of α-MoO₃ Nanosheets by Weak Interlayer Coupling

Abstract

van der Waals (vdW) materials have shown unique electrical and optical properties depending on the thickness due to strong interlayer interaction and symmetry breaking at the monolayer level. In contrast, the study of electrical and tribological properties and their thickness-insensitivity of van der Waals oxides are lacking due to difficulties in the fabrication of high quality two-dimensional oxides and the investigation of nanoscale properties. Here we investigated various tribological and electrical properties, such as, friction, adhesion, work function, tunnel current, and dielectric constant, of the single-crystal α-MoO3 nanosheets epitaxially grown on graphite by using atomic force microscopy. The friction of atomically smooth MoO3 is rapidly saturated within a few layers. The thickness insensitivity of friction is due to very weak mechanical interlayer interaction. Similarly, work function (4.73 eV for 2 layers (hereafter denoted as L)) and dielectric constant (6 for 2L and 10.5–11 for >3L) of MoO3 in MoO3 showed thickness insensitivity due to weak interlayer coupling. Tunnel current measurements by conductive atomic force microscopy showed that even 2L MoO3 of 1.4 nm is resistant to tunneling with a high dielectric strength of 14 MV/cm. The thickness-indifferent electrical properties of high dielectric constant and tunnel resistance by weak interlayer coupling and high crystallinity show a promise in the use of MoO3 nanosheets for nanodevice applications.

A Schottky‐Barrier‐Free Plasmonic Semiconductor Photocatalyst for Nitrogen Fixation in a “One‐Stone‐Two‐Birds” Manner

“…To identify the physical origin of the scattering peaks, a series of numerical calculations were performed based on the Mie theory (see the Experimental Section in the Supporting Information). [38,39] Because our synthesized material is different from those reported previously in many aspects, [40][41][42] the reported dielectric function is not suitable for our material. The dielectric function of the MoO 3−x spheres in this work was modeled using the Drude-Lorentz model based on the charge carrier density calculated from the Mott-Schottky plot (Figure S14, Supporting Information).…”

Tailored Hydrogen-Free Carbon Films by Tuning the sp2/sp3 Configuration

“…While capturing a topography image, the CPD image was simultaneously captured with an AC modulation of 1 V at 20 kHz. The work function of the sample (ϕ s ) was calculated from the measured CPD using the following equation where e is the elementary charge. The work function of the tip (ϕ tip ) was calibrated using an Au-coated substrate.…”

Investigation of laser-induced-metal phase of MoTe2 and its contact property via scanning gate microscopy

“…However, it is reasonable to consider that MoOx does not contribute to the metallic behavior of the LIM phase since the MoOx is usually an insulator. 30 The existence of Mo atoms is confirmed also by energy dispersive X-ray spectroscopy (EDS, see supporting information #S3 for the detail). Interestingly, the ratio of Mo and Te is almost 1:1 in the LIM region.…”

“…3(f) shows a diode-like rectification for negative carriers; electron injection is strongly suppressed at the Pd contact due to the existence of a 20 ~ 80 meV-high Schottky barrier at the interface between Pd and a valence band of 2H-MoTe2 extracted from several temperature-dependence experiments. [34][35][36] Considering a Fermi-level pinning effect 30 , the barrier height from the Fermi level of Pd to the conduction band of 2H-MoTe2 is much larger than that to the valence band, because of the larger work function of Pd (~5.4 eV). 37 8 Such a diode-like behavior has been reported in a MoS2 device due to asymmetric Schottky contact.…”