| AVS 60th International Symposium and Exhibition | |
| Helium Ion Microscopy Focus Topic | Thursday Sessions |
| Session HI-ThA |
| Session: | Imaging and Lithography with Helium Ions |
| Presenter: | D. Pickard |
| Authors: | D. Pickard H.F. Hao, National University of Singapore V. Viswanathan, National University of Singapore M. Bosman, IMRE , A*STAR J. Dorfmüller, University of Stuttgart, Germany H. Giessen, University of Stuttgart, Germany A.S. Yusuf, National University of Singapore Z.K. Ai, National University of Singapore Y. Wang, National University of Singapore M. Mahmoudi, National University of Singapore |
| Correspondent: | Click to Email |
Metallic nanostructures, resonant at optical frequencies, provide controlled enhancement and concentration of electromagnetic energy in the near-field. One example is the enhanced transmission and field localization through sub-wavelength C-apertures on thin metallic films, where transmission gains of 6x and field enhancements of 550x have been reported by others. [1] [#_ftn1]-[2] [#_ftn2] Typically, the critical dimensions of optical apertures are on the order of tens of nanometers (for low-order structures in the near-IR). These dimensions are accessible with conventional focused gallium ion beam patterning, and this has traditionally been the technique used for fabrication. However, for patterning dimensions smaller than 30 nm (typical of visible and ultraviolet structures, or higher order resonant structures), gallium based systems have not performed as successfully. The most critical shortcomings of Ga+ patterning in this regime are the degradation of the fine structure by etching with the beam’s tail, and the shift in the optical characteristics or quenching of the resonant metal’s properties due to gallium implantation. gallium implantation [3] [#_ftn1].
We have employed the Helium Ion Microscope to directly pattern high order, sub-10 nm optical fractal apertures (free of implanted metal impurities) through optically thick, polycrystalline metallic films and single crystal metal nanoplatelets. Our experimental measurements of the near-field mode profiles with electron energy loss spectroscopy (EELS) demonstrate tight field confinement in multiple modes as predicted by FDTD simulations. This has resulted in extremely high fidelity, optically-active resonant structures (down to 10 nm critical dimension). Controlled fabrication of structures on this size scale opens fascinating prospects for engineering complex multi-modal structures which were previously unrealizable by other techniques. We report our investigations in this arena and detail a variety of novel structures that are now accessible with this technique.
[1] X.L. Shi, L. Hesselink, J. Opt. Soc. Am. B 21, 13 (2004)
[1] B. Lee, I.M. Lee, S. Kim, D. Ho Oh, L. Hesselink, J. Mod. Optic. 57, 19 (2010)
[1] J.B. Leen, P. Hansen, Y.T. Cheng, L. Hesselink, OptLett 33, 23 (2008)