SEM images of thin film surface, showing the effect of Increasing Oxygen Concentration on the silica films at: D = 0 % O2; E = 0.5 % O2; F = 0% O2

SEM images of thin film surface, showing the effect of Amplitude Modulation of the Voltage Signal on the silica films at: A = 50 Hz at 10 kHz; B = 500 Hz at 10 kHz; C = 1 kHz at 10 kHz

School of Research, Enterprise and Innovation Vacation Studentship 2016

Production of scratch resistant coating using atmospheric pressure chemical vapour deposition via dielectric barrier discharge

By David Ashworth (Mchem)

• Deposition of hundreds of nanometre thick layers of functional films onto polymer gives rise to unique properties that allow for their utilisation as scratch resistant coatings, barrier layers and their use in the semiconductor industry.

• Current methods use low pressure plasma enhanced chemical vapour deposition (PECVD) that requires expensive vacuum equipment, the use of atmospheric pressure PECVD allows for the production of low cost coatings onto a range of substrates.

• This project focuses on the deposition of silica and the change in surface properties that accompany changes in the experimental conditions.

• Samples were coated using a dielectric barrier discharge chamber with two 1 mm thick alumina dielectric measuring 50x50 mm coated with approx. 5 micron thick copper coating forming the electrode and separated by 1mm.

• The plasma was generated from a custom power supply consisting of signal generator, amplifier and transformer. Standard commercially available BOPP was used as the substrate along with standard glass slides for deposition rate testing.

• The total flow rate was fixed at 5 SLM and HMDSO concentration fixed at 500 ppm in argon.

• Oxygen concentration was varied, in addition to amplitude modulation of the voltage signal.

Successfully built plasma CVD system and produced silica coatings under a variety of operating conditions.

Identified a change in Si-O bond character when amplitude modulation of the voltage waveform was utilised, this was identified by taking the second derivative of the FTIR data.

Observed a decrease in C-H bond intensity and an increase in Si-O signal strength, as oxygen concentration was raised over the range 0-2%.

Conclusions

Reactor Configuration

Introduction Results:

A B C

D E F

Voltage and Current traces when the 10 kHz signal driving the plasma is modulated by a signal of 1 kHz

Second derivative of Si-O2 peak in FTIR spectrum of silica thin film. showing a shift with amplitude modulation of driving voltage.

FTIR spectrum of silica thin films showing the effect of increasing O2 concentration during the plasma CVD process

David Ashworth, Dr. Zaenab Abd-Allah, Professor Peter Kelly, Dr. David Sawtell

Surface profilometry of thin film surface, showing: G, typical film surface, and H, film thickness.

G H