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Published on: November 9, 2015
Nanoscale Soft Wetting Observed in Co/Sapphire during Pulsed Laser Irradiation
Jung Won Choi1, Daseul Ham2, Seonghyun Han1
1School of Materials Science and Engineering and Department of Physics and Photon Science, Gwangju Institute of Science and Technology, Gwangju 61005, Korea.
Abstract:
Liquid drops on deformable soft substrates exhibit quite complicated wetting behavior as compared to those on rigid solid substrates. We report on a soft wetting behavior of Co nanoparticles (NPs) on a sapphire substrate during pulsed laser-induced dewetting (PLID). Co NPs produced by PLID wetted the sapphire substrate with a contact angle near 70°, which is in contrast to typical dewetting behavior of metal thin films exhibiting contact angles greater than 90°. In addition, a nanoscale γ-Al2O3 wetting ridge about 15 nm in size and a thin amorphous Al2O3 interlayer were observed around and beneath the Co NP, respectively. The observed soft wetting behavior strongly indicates that the sapphire substrate became soft and deformable during PLID. Moreover, the soft wetting was augmented under PLID in air due to the formation of a CoO shell, resulting in a smaller contact angle near 30°.
