Controlled Synthesis of Sub-Millimeter Nonlayered WO<inf>2</inf> Nanoplates via a WSe<inf>2</inf>-Assisted Method

Abstract

2D metal oxides (2DMOs) have stimulated tremendous attention due to their distinct electronic structures and abundant surface chemistry. However, it remains a standing challenge for the synthesis of 2DMOs because of their intrinsic 3D lattice structure and ultrahigh synthesis temperature. Here, a reliable WSe2-assisted chemical vapor deposition (CVD) strategy to grow nonlayered WO2 nanoplates with tunable thickness and lateral dimension is reported. Optical microscopy and scanning electron microscopy studies demonstrate that the WO2 nanoplates exhibit a well-faceted rhombic geometry with a lateral dimension up to the sub-millimeter level (≈135 µm), which is the largest size of 2DMO single crystals obtained by CVD to date. Scanning transmission electron microscopy studies reveal that the nanoplates are high-quality single crystals. Electrical measurements show the nanoplates exhibit metallic behavior with strong anisotropic resistance, outstanding conductivity of 1.1 × 106 S m−1, and breakdown current density of 7.1 × 107 A cm−2. More interestingly, low-temperature magnetotransport studies demonstrate that the nanoplates show a quantum-interference-induced weak-localization effect. The developed WSe2-assisted strategy for the growth of WO2 nanoplates can enrich the library of 2DMO materials and provide a material platform for other property explorations based on 2D WO2.