Wafer-Scalable Single-Layer Amorphous Molybdenum Trioxide

Abstract

Molybdenum trioxide (MoO3), an important transition metal oxide (TMO), has been extensively investigated over the past few decades due to its potential in existing and emerging technologies, including catalysis, energy and data storage, electrochromic devices, and sensors. Recently, the growing interest in two-dimensional (2D) materials, often rich in interesting properties and functionalities compared to their bulk counterparts, has led to the investigation of 2D MoO3. However, the realization of large-area true 2D (single to few atom layers thick) MoO3 is yet to be achieved. Here, we demonstrate a facile route to obtain wafer-scale monolayer amorphous MoO3 using 2D MoS2 as a starting material, followed by UV–ozone oxidation at a substrate temperature as low as 120 °C. This simple yet effective process yields smooth, continuous, uniform, and stable monolayer oxide with wafer-scale homogeneity, as confirmed by several characterization techniques, including atomic force microscopy, numerous spectroscopy methods, and scanning transmission electron microscopy. Furthermore, using the subnanometer MoO3 as the active layer sandwiched between two metal electrodes, we demonstrate the thinnest oxide-based nonvolatile resistive switching memory with a low voltage operation and a high ON/OFF ratio. These results (potentially extendable to other TMOs) will enable further exploration of subnanometer stoichiometric MoO3, extending the frontiers of ultrathin flexible oxide materials and devices.

Two-Dimensional Crystals as a Buffer Layer for High Work Function Applications: The Case of Monolayer MoO3

“…We emphasize that, among global properties and efficiency of the applied materials, the functional layers should be deeply studied on the nanoscale by electronic structure-sensitive techniques, as this is where potential optimization should be looked for. This approach especially paves the way for designing more complex vdW heterostructures. , …”

“…This approach especially paves the way for designing more complex vdW heterostructures. 32,33 ■ RESULTS AND DISCUSSION Monolayer MoO 3 �Morphological Characterization. We synthesized monolayer MoO 3 directly on HOPG in UHV through thermal evaporation of MoO 3 powder at elevated substrate temperatures, as described in our previous work.…”

Graphene and Beyond: Recent Advances in Two-Dimensional Materials Synthesis, Properties, and Devices

“…259 The switching behavior shows SET voltage at ∼1 V where the device transitions from HRS to LRS and RESET voltage at ∼ −0.5 V where the device is switched back to HRS from LRS (Figure 16e), confirming the resistive-switching property is intrinsic to MoO 3-x . 259 Unlike its bulk TMO device counterpart, nanometer MoO 3-x based nonvolatile devices does not need the forming process to establish a conductive filament. Additionally, its small switching voltage (<1 V) and large ON/OFF ratio (>10 7 ) can inspire further investment on ultrathin flexible memory and neuromorphic computing.…”

“…Needless to say, 2D TMOs will be technologically important for nanoelectronics, memory, sensors, and heterogeneous integration with other 2D materials because their high surface-to-volume ratio and thickness-independent electronic properties are essential for device scaling, low-power electronics, and high photon and gas sensitivity. − To realize its practical applications, it is necessary to have techniques that can prepare scalable and highly uniform 2D TMOs. So far, standard thin-film depositions (PVD, PLD, CVD, and MBE) can synthesize large-area MoO 3‑ x atomically thin films.…”

Role of Hydrogen in Suppressing Secondary Nucleation in Chemical Vapor-Deposited MoS2

“…35 Moreover, the N−MoS 2 has a distinct Mo-3d 3/2 peak at ∼235 eV, corresponding to the Mo(V) oxidation state of non-stoichiometric oxides. 49 Conducting the growth in a reducing environment strongly suppresses the Mo(VI) oxidation state, as observed in H−MoS 2 [Figure 2c], leading to a significantly decreased fraction of oxidized molybdenum in the near-surface region. The corresponding S-2p peaks are shown in Figure 2d−f.…”