| AVS 62nd International Symposium & Exhibition | |
| Electronic Materials and Processing | Monday Sessions |
| Session EM+AS+SS-MoM |
| Session: | Rectenna Solar Cells, MIM Diodes, and Oxide Interfaces |
| Presenter: | Richard M. Osgood, US Army NSRDEC |
| Authors: | R.M. Osgood, US Army NSRDEC J. Xu, Brown University G.E. Fernandes, Brown University M. Rothschild, MIT Lincoln Laboratory K. Diest, MIT Lincoln Laboratory M. Kang, Seoul National University, Republic of Korea K.B. Kim, Seoul National University, Republic of Korea L. Parameswaran, MIT Lincoln Laboratory P. Periasamy, IBM M. Chin, Army Research Laboratory S. Kooi, MIT Institute for Soldier Nanotechnologies S. Giardini, US Army NSRDEC R. O'Hayre, Colorado School of Mines P. Joghee, Colorado School of Mines |
| Correspondent: | Click to Email |
We investigate arrays of “microrectennas” (with sub-micron features tuned for the near-and short-wave infrared) consisting of “stripe-teeth” metamaterial antennasconducting vertically through the coupled, underlying metal-insulator-metal (MIM) diode into a metallic substrate. Stripes, with cross-stripe resonances, conduct current out of the array, while antenna-like teeth break left-right symmetry and concentrate a high vertical electric field (Ez) at the end of the teeth at their antenna resonance. If plasmonic field enhancement and concentration reduce the capacitance and/or increase the effective voltage across the MIM diode, new research and development of large-area ultrafast optical rectennas will be enabled, requiring patterning and alignment of only the top metal layer.
Stripe-teeth arrays were designed, fabricated, and analyzed both experimentally and theoretically. Substrates were layers (“ground planes”) of Nb and Al, and a Au nanowire array patterned using novel high-throughput e-beam technology.1 Substrates were oxidized/anodized, or had oxides deposited, to form microantenna-coupled MIM diodes consisting of Al-Al2O3-Al, Au/Ti-NbOx-Nb, Al-Al2O3-Au, Ag/Ti-NbOx-Nb, Ag/Ti-NiO-Ni, Pt-NbOx-Nb, after deposition of top metal layers of Ag/Ti, Au/Ti, Pt, and Al (only a few nm of Ti). Conduction through 10-25 nm thick oxide layers in the MIM diodes occurred via quantum mechanical tunneling and thermionic emission, with asymmetric barrier heights all less than 1 V except for the Al-Al2O3-Al diodes. The Au-Al2O3-Al system required modeling the “hot spot” from top metal protrusions into the Al2O3barrier layers and in close (tunneling) proximity to the ground plane, probably because of the surface roughness and variation in Al2O3 thickness; the planar-planar MIM diode model was inapplicable in this case.
The top metal was patterned into the stripe-teeth arrays. Reflective Al substrates provided sharp optical antenna resonances while Nb layers produced broader, weaker antenna resonances due to Nb absorption, similar to stripe-only arrays reported in Ref. 2. We also report the result of visible light (514 nm – 630 nm) laser illumination of Nb/NbOx/Ag(Ti) stripe-teeth arrays, including the observation of a short-circuit current and open-circuit voltage, in response to power densities in the range 80 W/cm2.
1. H. S. Lee, et. al., “Electron beam projection nanopatterning using crystal lattice images obtained from high resolution transmission electron microscopy”, Adv. Mats. 19 4189 (2007).
2. Wu, C., et.al.“ Large-area wide-angle spectrally selective plasmonic absorber,” Phys. Rev. B, Vol. 84, 075102-7, 2011.