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Jaehyun Park

Jaehyun Park. EE235 Student presentation / Mar 09, 2009. Motivation. Among NGL methods : use molds for imprinting features into thin polymer films Evaluation of resolution limits : most effectively done by using molds

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Jaehyun Park

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  1. Jaehyun Park EE235 Student presentation / Mar 09, 2009

  2. Motivation • Among NGL methods : use molds for imprinting features into thin polymer films • Evaluation of resolution limits : most effectively done by using molds • Difficult to fabricate structures of sub 5nm using conventional methods : resolution limit and non-uniformities

  3. Their solution • Use SWNTs as templates • Features of SWNT (single-walled nanotube) • Cylindrical cross-sections • Atomic scale uniformity • Chemical inertness • Ability to grow or deposit them in large quantities over large areas : 0.5~5nm dia.,1~10 tubes/μm2 • Research on polymer characteristics with SWNT molds

  4. Fabrication process • Master mold : • Grow SWNT using CVD on SiO2/Si • Replicated mold : • Spin h-PDMS on cured PDMS • Casting & curing: Platinum catalyst used to form 3D crosslinking • Imprinting : • Spin low viscosity PU • Lightly press mold & cure under UV • Peel off

  5. Experiments : AFM • AFM Shows heights of features • Accurately reproduces nanoscale features over multiple cycles • Some distortions : surface roughness of molded PU

  6. Experiments : TEM TEM : mold • TEM shows widths of features • PAA used instead of PU • Imprinted structures similar to master features • For widths below 3nm : difficult to determine due to grain size of Pt/C (~1nm) TEM : master

  7. Experiments : AFM at sub 2nm scale • defects appeared

  8. Polymer limits resolution • Clues • Beaks in molded feature occurs at the same position • Imprinted features with dissimilar polymers have similar surface roughness • SiO2/Si has 0.19nm surface roughness • Distance between crosslinks of polymer (1nm for h-PDMS)

  9. Density of crosslinks • Crosslink density : affects capability of defining small feature and retaining shape • Attempts to increase in h-PDMS : failed due to stiction to mater mold

  10. Surface roughness • F. Hua, et. al., “Processing Dependent Behavior of Soft Imprint Lithography on the 1-10 nm Scale”, IEEE Trans. on Nanotechnology, 5, 301 (2006) • Got 0.26nm RMS at 9k rpm of polymer spin • Processing conditions : extremely important in achieving high-fidelity nanoimprint lithography in the 1-10nm regime.

  11. Conclusion • Simple method for evaluating resolution limits on imprinting polymers, as small as 2nm • Resolution is determined by both polymer chemistry and process condition • To enhance the resolution • Polymer having high crosslink density • Process to make smaller roughness

  12. Supplements : TEM • TEM analysis for lateral dimension • Sample prepared by metal shadowing technique • PAA can replicate fine feature and is dissolvable by water • Pt/C has fine grain • Carbon mechamically support the thin film

  13. Supplements : Pt catalyst

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