Ga-In liquid metal nanoparticles prepared by physical vapor deposition

Controlled synthesis and appropriate characterization of nanoscale particles of gallium-based liquid metals are critical to fulfilling their broad range of applications in the field of flexible, stretchable, and printable micro-/nanoelectronics. Herein, we report a new way to synthesize surfactant-free gallium-indium nanoparticles with controlled particle size on a variety of substrates through a facile physical vapor deposition method. It was found that with prolonged deposition time the liquid metal nanoparticles gradually grew from near-monodispersed small particles with a diameter of ~25 nm to bimodal distributed particles. A nucleation, growth, ripening and merging process was proposed to explain the observed evolution of particle size. Atomic force microscopy measurement indicates that the fabricated liquid metal nanoparticles demonstrate elastic deformation with a certain range of loads and the scanned particle size is dependent on the applied loads. We further investigated the gradual breaking process of the core-shell structured liquid metal nanoparticles, which was evidenced by multiple kinks on the force-separation curve. This work presents a new bottom-up approach to prepare nanoscale liquid metal particles and demonstrates that atomic force microscopy is a suitable technique to characterize the synthesized liquid metal nanoparticles.