Surface Characteristics of Silicon Nanowires/Nanowalls Subjected to Octadecyltrichlorosilane Deposition and n-octadecane Coating

Abstract

In this study, nanowires/nanowalls were generated on a silicon wafer through a chemical etching method. Octadecyltrichlorosilane (OTS) was deposited onto the nanowire/nanowall surfaces to alter their hydrophobicity. The hydrophobic characteristics of the surfaces were further modified via a 1.5-μm-thick layer of n-octadecane coating on the OTS-deposited surface. The hydrophobic characteristics of the resulting surfaces were assessed using the sessile water droplet method. Scratch and ultraviolet (UV)-visible reflectivity tests were conducted to measure the friction coefficient and reflectivity of the surfaces. The nanowires formed were normal to the surface and uniformly extended 10.5 μm to the wafer surface. The OTS coating enhanced the hydrophobic state of the surface, and the water contact angle increased from 27° to 165°. The n-octadecane coating formed on the OTS-deposited nanowires/nanowalls altered the hydrophobic state of the surface. This study provides the first demonstration that the surface wetting characteristics change from hydrophobic to hydrophilic after melting of the n-octadecane coating. In addition, this change is reversible; i.e., the hydrophilic surface becomes hydrophobic after the n-octadecane coating solidifies at the surface, and the process again occurs in the opposite direction after the n-octadecane coating melts.

Laser-induced silicon nanocolumns by ablation technique

“…The average size of the spherical tip at the top of Si nanocolumns was 250 nm reached to 500 nm. Si Nanocolumns in Figure 4 (Yilbas et al, 2016). In our case the Si nanoclumns size was bigger and this due to the property of coherent light and single wavelength in UV range of laser beam that ablate a uniform and large quantity from the surface of silicon and finally it forms a bigger size (Acikgoz et al, 2012).…”

Reversible exchange of wetting state of a hydrophobic surface via phase change material coating

“…12 The thin lm of solid phase of n-octadecane does not signicant effect on the hydrophobic characteristics of the surface; in which case, the surface can remain as hydrophobic aer solidication of n-octadecane lm. 12 However, the liquid phase of the n-octadecane lm covers the hydrophobic surface while changing the wetting state from hydrophobic to hydrophilic. Since the reversible exchange of wetting state has the practical importance in advanced multifunctional systems, such as biomaterials, and microuidic devices, [14][15][16] investigation of processes and physical insight into the reversible exchange of the wetting state on the surface becomes essential.…”

Mobility of A Water Droplet on Liquid Phase of N-Octadecane Coated Hydrophobic Surface

“…This becomes particularly interesting if the change of the wetting state takes place reversibly. One of the methods to achieve reversible wetting state is to deposit a thin layer of phase change material on to the hydrophobic surface 10 . This arrangement provides the surface wetting state change in such a way that the surface becomes hydrophilic when the thin liquid film is in the liquid phase and it remains hydrophilic when the film is in the solid phase 10 .…”

“…One of the methods to achieve reversible wetting state is to deposit a thin layer of phase change material on to the hydrophobic surface 10 . This arrangement provides the surface wetting state change in such a way that the surface becomes hydrophilic when the thin liquid film is in the liquid phase and it remains hydrophilic when the film is in the solid phase 10 . However, the droplet behavior on the liquid film formed from the phase change material is important in terms of practical applications of reversible exchanging of the surface wetting state.…”

“…In addition, the water droplet mobility on a hydrophobic surface under a thermal radiative heating was investigated 20 ; however, the influence of gravitational potential energy on the droplet motion on the inclined impregnated surface was left for the future study. The exchange of the surface wetting state is demonstrated to be possible when the surface is coated by a thin layer of a phase change material 10 , 21 ; however, the droplet mobility on the liquid phase of the thin film of the phase change material needs to be examined further. This becomes essential to assess water droplet behavior on the reversibly exchanging wetting state surface, if the surface remains in a liquid phase.…”