Highly Ordered Nano-Structured Templates: Enabling New Devices, Sensors, and Transducers

1. Highly Ordered Nano-Structured Templates: Enabling New Devices, Sensors, and Transducers Student: Gilad A. Kusne (1st Year PhD) Professors: D. N. Lambeth (ECE & MSE), G. S. Rule (Biology), E. Towe (ECE & MSE) Application Examples Motivation Methodology: Self Assembly for 2D Lattice • Many devices can benefit from regular 2D patterning at nano-scale dimensions: • Field Emission Display: Well ordered field emitter film provides large area uniform luminescence. • Photovoltaic devices: GaAs-based quantum dots for high conversion efficiency photovoltaic devices. • Quantum Dot Lasers: High precision dimensional control of lattice structure for lower energy loss. • Hard disk media: Grain size uniformity and position control for ultra low noise hard disk recording media. • Nano-scale ordered patterning can offer great benefits to many areas of technology. • Reduced noise due to greater material order. • Material property uniformity over large areas. • Improved environment and resonance effects for quantum phenomena. • More efficient energy conversion due to enhanced control of nano-scale dimensions. • Employ: • Highly monodispersed particle size • Self assembly mechanics, chemistry and biology to generate nano-scale 2-D lattice templates. • Materials: (sub-optical lithography sizes) • Ferritin • S-layer protein • Polystyrene spheres • Porous Si or Al (anodization) • Benefits of self assembly: • Faster and cheaper than common lithography methods for large scale ordering. • Narrow distribution of nano-scale material dimensions. S-layer Proteins Polystyrene Spheres Ferritin Polystyrene spheres mechanically self order into hexagonal arrays. Different diameter spheres can be used to generate templates with lattice structures of varying dimensions. Ferritin is a protein cage containing an iron oxide particle with a very narrow size distribution. The iron oxide particle can be replaced with other metal particles. The protein self orders into a 2D hexagonal lattice that can be used as a template for other templates. Breaking down the protein leaves behind an ordered array of metal particles for nucleation sites. The S-layer protein bonds to nanometer sized metal particles and self orders into various 2D hexagonal arrays. Varying types of 2D array patterns are possible with different forms of the S-layer protein. Arrays of metal particles have been shown, but not with particles of a narrow size distribution. These arrays have yet to be used as a template for solid state devices. AFM image of spin coated 0.5um diameter polystyrene spheres organized in monolayer. [1] TEM image of ferritin containing metal nano-particles. [3] TEM images of Au particles in (a) Deinococcus radiodurans S-layer protein array [5] (b) Sulfolobus acidocaldarius S-layer protein array.[6] The polystyrene monolayer can be used as a template for generating a 2D array of nucleation sites for carbon nanotubes. Disordered ferritin has been used as a precursor for carbon nanotube nucleation sites, however ordered carbon nanotube growth based on the ferritin lattice structure was not shown. (a) D. radiodurans Hexagonally Packed Intermediate (HPI) S-layer bonding structure (b) S. acidocaldarius (SAS) S-layer protein bonding structure. [6] SEM images of (a) the top and (b) the side view of carbon nanotubes generated by plasma enhanced chemical vapor deposition using Ni nucleation sites. Sites made by evaporating Ni through polystyrene sphere monolayer. [2] Diameter distribution of ferritin core estimated by TEM imaging. [4] [1] Huang ZP. Appl Phys Lett. Vol 82, No 3, p460-462, 2003. [2] Wang Y. Appl Phys Lett. Vol 85, No 20, p4741-3, 2004. [3] Mayes E. IEEE T Magn. Vol 39, No 2, p624-7, 2003. [4] Kondo D. Jpn J Appl Phys. Vol 44, No 7A, p5292-5, 2005. [5] Bergkvist M. J Phys Chem B. Vol 108, p8241-8, 2004. [6] Mark SS. Langmuir. Vol 22, p3763-74, 2006