Oxygen plasma-treatment effects on Si transfer

Area of Science:

• Surface science and materials engineering.
• Nanotechnology and microfabrication.
• Polymer science and surface modification.

Background:

• Poly(dimethylsiloxane) (PDMS) stamps are widely used in microcontact printing (muCP) for their hydrophilicity.
• Oxygen plasma treatment enhances PDMS hydrophilicity but can lead to silicon-containing fragment transfer.
• The impact of plasma parameters on this undesirable silicon transfer is not well understood.

Purpose of the Study:

• To investigate the effect of oxygen plasma treatment parameters on silicon transfer from PDMS stamps during muCP.
• To quantify silicon transfer using X-ray photoelectron spectroscopy (XPS).
• To analyze topographical changes on PDMS stamps using scanning electron microscopy (SEM).

Main Methods:

• Unpatterned PDMS stamps were treated with oxygen plasma under varied conditions.
• Stamps were used for muCP of deionized water onto poly(methyl methacrylate) (PMMA) substrates.
• PMMA substrates were analyzed by XPS for silicon quantification; PDMS stamps were analyzed by SEM for topography.

Main Results:

• All oxygen plasma treatments significantly reduced silicon transfer compared to untreated PDMS stamps.
• Silicon transfer originates from residual PDMS fragments not eliminated by plasma treatment.
• No correlation was found between stamp topographical changes and the extent of silicon transfer.

Conclusions:

• Oxygen plasma treatment is effective in minimizing silicon transfer during muCP of PDMS.
• Understanding plasma parameters is crucial for optimizing PDMS surface modification and reducing contamination.
• Stamp topography changes do not predict the amount of silicon fragment transfer.