Fine-tuning of the surface free energy (SFE) of a solid material facilitates its use in a wide range of applications requiring precise control of the ubiquitous presence of liquid on the surface. In this study, we found that the SFE of rare-earth oxide (REO) thin films deposited by atomic layer deposition (ALD) gradually decreased with increasing film thickness; however, these changes could not be understood by classical interaction models. Herein, the mechanism underlying the aforesaid decrease was systematically studied by measuring contact angles, surface potential, adhesion force, crystalline structures, chemical compositions, and morphologies of the REO films. A growth mode of the REO films was observed: layer-by-layer growth at the initial stage with an amorphous phase and subsequent crystalline island growth, accompanied by a change in the crystalline structure and orientation that affects the SFE. The portion of the surface crystalline facets terminated with (222) and (440) planes evolved with an increase in ALD cycles and film thickness, as an amorphous phase was transformed. Based on this information, we demonstrated an SFE-tuned liquid tweezer with selectivity to target liquid droplets. We believe that the results of this fundamental and practical study, with excellent selectivity to liquids, will have significant impacts on coating technology.
|Number of pages||12|
|Publication status||Published - 2020 Jan 28|
Bibliographical noteFunding Information:
The analysis using SIMS and XPS was supported by Korea Basic Science Institute. This research was supported in part by the Department of Energy under award number DE-SC0004782 (L.Z. and S.F.B.), and GIWAXS was performed at the SSRL. This research was also supported by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (2018R1D1A1B07049247) as well as by the Ministry of Trade, Industry and Energy (MOTIE) (10080643) and Korea Semiconductor Research Consortium (KSRC) support program for the development of future semiconductor devices.
© 2020 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Physics and Astronomy(all)