Casimir-Lifshitz quantum state of superhydrophobic black-silicon surfaces manufactured by a metal-assisted hierarchical nano-microtexturing process

ABSTRACT

We investigated superhydrophobic Si nanosurfaces similar to the lotus leaf by performing a hierarchical nanotexturing process on micropyramidal Si surfaces. The process was carried out using a metal-assisted chemical etching process based upon the deposition of Ag nanoparticles. The hierarchical micro-nanosurfaces showed a superhydrophobic character with contact angles of approximately 134∼150°. The photon tunnelling also provides a strong light absorption as a black Si. The surface-light emission from broad and sharp photoluminescence was observed in the wavelength ranges of 414.7∼440 and 509∼516.2 nm. The field-induced tunnelling current on nanosurface shows the formation of quantum surface states. From the analyses of Casimir-Lifshitz quantum state of a photon in vacuum, the superhydrophobic behaviour of water droplet is closely related to the nanosurface and the nanoporous cavity shows the absorption of terahertz energy. Si nanosurface shows the broadband absorption in the spectral range of 800∼900 cm⁻¹ corresponding to the energy range of 99.2∼111.6 meV with 24∼27 THz.

KEYWORDS:

• Metal-assisted etching
• Ag nanodot deposition
• hierarchical nano-microstructure
• superhydrophobic nanosurface

Acknowledgments

This research was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF), funded by the Ministry of Education (NRF-2014R1A1A2056184). The AFM topographic images and the conductance images were measured by Dr. Marcel Winhold of Nanosurf Co. and the contribution of Ms. Fanny Dorta also from Nanosurf Co. is greatly appreciated.

Disclosure statement

No potential conflict of interest was reported by the authors.

ORCID

Bhaskar Parida http://orcid.org/0000-0002-4026-1366

Keunjoo Kim http://orcid.org/0000-0002-5103-699X

Additional information

Funding

This work was supported by Basic Science Research Program of the National Research Foundation of Korea (NRF): [Grant Number NRF-2014R1A1A2056184].