Surface Plasmon-Assisted Nanolithography on Silicon

• Author / Creator

  Liu, Fenglin

• Nanoscale lithography on silicon is of interest for applications ranging from computer chip design to tissue interfacing. Block copolymer-based self-assembly, also called directed self-assembly (DSA) within the semiconductor industry, can produce a variety of complex nanopatterns on silicon, but these polymeric films typically require transformation into functional materials. The fabrication of plasmonic stamps is demonstrated, which is an optically transparent flexible PDMS stamps with patterned gold hemispheroids that were produced via block copolymer self-assembly on silicon surfaces. Gold salt metallization and subsequent plasma treatment of solvent annealed block copolymers led to the gold nanopatterns on flat silicon surfaces. With sequential steps of precursor spin-coating, curing, and peeling off of the PDMS layer, a plasmonic stamp with embedded ordered gold hemispheroid arrays can be obtained. By varying the molecular weight of the block copolymer templates, controllable size and spacings of Au nanopatterns in the plasmonic stamp can be captured. By using these plasmonic stamps, direct functionalization of silicon surfaces can be achieved via hydrosilylation of selected 1-alkenes or 1-alkynes on a sub-100 nm scale, leading to nanopattern transfer from self-assembled block copolymer templates to the 1-alkyl or 1-alkenyl molecular patterns on flat silicon surfaces. The molecular patterns were captured by AFM, and can be further visualized by surface modification involving thiol-ene chemistry to obtain thiol-terminated patterns, followed by attachment of gold nanoparticles or gold electroless deposition in the thiol-terminated regions. In terms of energy exchange between metals and semiconductors, there are a number of ways to complete the energy transfer in radiative or non-radiative manners. Based on the mechanistic discussions and results on simulation and Au-Si distance studies, we propose that the intense electric near-field that results from the localized surface plasmons resonance of the gold nanoparticles in the plasmonic stamps upon illumination with green light, leads to generation of electron-hole pairs in the silicon that drive spatially-localized hydrosilylation. Free charge carrier impact ionization, induced by the electric field of the local plasmons of the gold nanohemispheroids is proposed to explain the role of doping. This approach demonstrates how localized surface plasmons can be used to enable functionalization of technologically relevant surfaces with nanoscale control, implying the potential applications for direct imaging intense electric fields in the plasmonic nanostructures.

• Subjects / Keywords

  • Surface plasmon
  • Block copolymers
  • Hydrosilylation

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3T43JH1N

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.