Liquid-Metal-Assisted Deposition and Patterning of Molybdenum Dioxide at Low Temperature

Molybdenum dioxide (MoO 2 ), considering its near-metallic conductivity and surface plasmonic properties, is a great material for electronics, energy storage devices and biosensing. Yet to this day, room-temperature synthesis of large area MoO 2, which allows deposition on arbitrary substrates, has remained a challenge. Due to their reactive interfaces and specific solubility conditions, gallium-based liquid metal alloys offer unique opportunities for synthesizing materials that can meet these challenges. Herein, a substrate-independent liquid metal-based method for the room temperature deposition and patterning of MoO 2 is presented. By introducing a molybdate precursor to the surrounding of a eutectic gallium-indium alloy droplet, a uniform layer of hydrated molybdenum oxide (H 2 MoO 3 ) is formed at the interface. This layer is then exfoliated and transferred onto a desired substrate. Utilizing the transferred H 2 MoO 3 layer, a laser-writing technique is developed which selectively transforms this H 2 MoO 3 into crystalline MoO 2 and produces electrically conductive MoO 2 patterns at room temperature. The electrical conductivity and plasmonic properties of the MoO 2 are analyzed and demonstrated. The presented metal oxide room-temperature deposition and patterning method can find many applications in optoelectronics, sensing, and energy industries.