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Negative Contrast Curves for Two-photon Free Radical Polymerization Systems and Their Potential Applications in Sub-diffraction Limited Two-photon Photolithography

Published online by Cambridge University Press:  10 April 2013

Robert J. DeVoe ,
Tzu-Chen Lee  and
Brian J. Gates
Robert J. DeVoe
Affiliation:
3M Corporate Research Materials Labs, St. Paul, MN 55144
Tzu-Chen Lee
Affiliation:
3M Corporate Research Materials Labs, St. Paul, MN 55144
Brian J. Gates
Affiliation:
3M Corporate Research Materials Labs, St. Paul, MN 55144
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Abstract:

Two-photon fabrication is a powerful method of fabricating complex microstructures. Superresolution by methods analogous to stimulated emission depletion (STED) has been described previously, enabling sub-100 nm imaging with 800 nm light. STED-related methods of enhancing imaging resolution require photoresists with exposure conditions for which the photoresist exhibits negative contrast, i.e., image density decreases with increasing exposure from the depletion beam. We have observed decreasing voxel size with increasing exposure during two-photon initiated polymerization of acrylate- and methacrylate-based photoresists, that is, negative imaging contrast, γ < 0, independent of the type of photoinitiator. Negative contrast is not observed in epoxy-type photoresists containing photoacid generators. An investigation of the exposure conditions has led us to conclude that radical-radical recombination at high exposure is responsible for negative contrast. Results of the investigation, discussion of the proposed mechanism for negative contrast and implications for two-photon superresolution will be presented.

Keywords

microstructurepolymerizationlaser-induced reaction
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1499: Symposium N – Precision Polymer Materials―Fabricating Functional Assemblies, Surfaces, Interfaces and Devices , 2013 , mrsf12-1499-n05-202
Copyright
Copyright © Materials Research Society 2013

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References

REFERENCES

DeVoe, Robert J., Lee, Tzu-Chen, Larsen, Jeremy K., Ender, David A., Sahlin, Jennifer J., Sykora, Craig R., Patnaude, Cheryl A., Atkinson, Matthew R., Griffin, Michael E., Gates, Brian J., and Redinger, David H., MRS 2011 Spring Symposium Proceeding, Symposium TT, TT09–14, R1. Google Scholar
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