Large-area synthesis of 2D MoO _{3− x} for enhanced optoelectronic applications

Abstract

Two-dimensional (2D) molybdenum trioxide has been attracting research interest due to its bandgap tunability and a wide variety of desirable electronic/optoelectronic properties. However, the lack of a reproducible synthesis process for obtaining large coverage 2D MoO3 has limited the use of this material. Here we report the synthesis of large area 2D MoO3-x via physical vapor deposition, using MoO3 powder as the precursor. The as-grown layers are directly deposited on SiO2/Si, eliminating the necessity for any transfer process. These as-grown MoO3-x layers allow for the large-scale fabrication of planar device arrays. The applicability of 2D MoO3-x in optoelectronics is established via the demonstration of low-power ultraviolet (UV) sensor arrays, with rapid response times (200 µs) and responsivity up to 54.4

A Self‐Powered High‐Performance UV Photodetector Based on Core–Shell GaN/MoO3–x Nanorod Array Heterojunction

“…No preferential orientation for the MoO 3– x layer exists, and minimal interfacial MoO x oxide is present possibly due to the effects of rapid heating and cooling PVD process. [ 36,39 ] The Raman spectra of bare GaN NRAs and GaN/MoO 3– x NRAs heterojunctions show the same Raman peak position and intensity in 564.4 cm −1 corresponding to the GaN E 2 (high) phonon mode (Figure 2d). [ 40 ] This observation indicates the good quality and stability of GaN NRAs after MoO 3– x layer deposition.…”

“…[ 34 ] The additional peaks at 23.3° and 27.4° correspond to (011) and (021) planes of the α‐MoO 3– x , respectively, confirming the quasi‐layered crystal structure. [ 36 ] The predicted 2θ peaks of each (hkl) plane based on the standard JPCDS files are shown in Figure 2c for comparison. For gaining insight into the atomic structure of as‐synthesized GaN/MoO 3– x NRAs heterojunction, high‐resolution transmission electron microscopy (HRTEM) was adopted.…”

“…Previous works used similar experimental conditions of PVD have reported oxygen deficiencies of MoO 3– x . [ 36,39,44 ] The oxygen defect reaction can be given by reaction () where V O is the oxygen vacancy and x O represents the lost oxygen atoms. The emergence of oxygen vacancy forces and rearranges the other atoms of the crystal lattice.…”

“…[ 32–34 ] Orthorhombic structured molybdenum trioxide (α‐MoO 3 ) is a rising and amazing TMO semiconductor with wide bandgap over 3.2 eV and is very suitable for UV light absorbers. [ 35,36 ] The energy band structures of α‐MoO 3 have been carried out through first‐principle calculations (Figure S1, Supporting Information), indicating that α‐MoO 3 is an excellent candidate in constructing heterojunctions with GaN NRAs.…”

Influence of an external electric field on the rapid synthesis of MoO3 micro- and nanostructures by Joule heating of Mo wires

“…28) or by physical evaporation deposition. 29 Here, the presence of a small amount of monoclinic phase could be related to the high speed of the growth process that allows low temperature metastable phases formation. Also in ref.…”