Superhydrophilic Surface by Aluminum-Induced Crystallization

of Amorphous Silicon

Ken KolliasPennsylvania State University

Dr. Min Zou Mechanical Engineering Dept.

Dr. Li CaiElectrical Engineering Dept.

Objective

• To study the wettability of textured surfaces on glass using Aluminum-Induced Crystallization (AIC) of amorphous silicon (a-Si) technique.

• To study the stability of superhydrophilic surfaces.

• To convert superhydrophilic surface to superhydrophobic.

Outline

• Introduction

• Process– AIC of a-Si– Characterization

• Results

• Conclusion

Introduction

• AIC of a-Si– Overview

• Reasons for Studying– Wenzel’s Equation– Glass naturally hydrophilic

Process

• Glass Substrate– a-Si deposition using PECVD

• Thin film with appropriate pressure, time, temp, gas flow

– Al deposition using Thermal Evaporator• Thin film with appropriate pressure and deposition rate

– Annealing• Temp= T1, T2, and T3• Time= 5 and 10 minutes

– Al Etch

Characterization

• Wettability– Water Contact Angle (WCA)

• Crystallization– X-Ray Diffraction (XRD)

• Topography– Environmental Scanning Electron Microscopy (ESEM)

Image taken from http://www.funsci.com

Results• Wettability

T3 after 192 hrs

T3 after 192 hrs

t = 0.12 sec

t = 0.5 sec

t = 0 sec

Results

• Crystallization

100

200

300

400

500

600

700

800

27 28 29 30

Angle (2theta)

Inte

ns

ity

(a

rbit

rary

un

its

)

(T3)

(T1) (T2)

Si(111)

Results• Topography (of superhydrophilic sample)

• Change In Plans

mag=1,000x; bar=20um mag=20,000x; bar=1um

Results• Switch to Superhydrophobic (WCA = 151.2o)

Results• Discussion

– Why is this study significant?• Other Research Groups

– Future research• Reason for stability of Superhydrophilicity

• Superhydrophilic-superhydrophobic pattern

• Reproducible? Real World Applications

Conclusion

A highly stable superhydrophilic surface, with the capability of converting to superhydrophobic, was created using AIC of a-Si on glass. There is an array of potential applications for this finding.

Acknowledgements

• Ying Song and Hengyu Wang.

• National Science Foundation (NSF) through REU Site and Nanoscale Exploratory Research Programs.

• Equipment support from Oak Ridge Associated Universities through the Ralph E. Powe Junior Faculty Enhancement Award.

Questions?

or

Comments.

UVO-Tunable Superhydrophobic to Superhydrophilic Wetting

Transition on Biomimetic Nanostructured Surfaces

Abstract: A novel strategy for a tunable sigmoidal

wetting transition from superhydrophobicity to superhydrophilicity on a continuous nanostructured hybrid film via gradient UV-ozone (UVO) exposure … and superhydrophilic ( H2O < 10 within 1 s) regions simply through the optical images of water droplets on the surface …