Nano-wire to Film Transitions During Pulsed-Laser Deposition: the Role of Plasma Plume Expansion

Due to their high conductivity, optical transparency, and high surface/volume ratio, indium-tin oxide (ITO) nanowires (NWs) are promising for flexible transparent electronics and gas sensors. During pulsed laser deposition (PLD) of ITO, NWs vs. films are typically selected via inert vs reactive atmospheres. In other studies, both NWs and films are observed during PLD in inert atmospheres. Here, we the consider the influence of the plasma plume expansion on NW vs film formation. For low pressure N2, we hypothesize that oxygen is strongly scattered, leaving a metal-rich plume, resulting in metal droplet formation, followed by vapor-liquid-solid growth of NW. As the N2 pressure is increased, the plasma plume and its metal rich core are compressed, resulting in a transition to films growth. This approach is likely applicable to a wide variety of metal-oxide NW core-shell structure for nanoscale devices. We gratefully acknowledge the support of NSF Grant # ECCS-1610362 and BSF Grant #2015700.