Heterostructures with at least one single digit nanometer dimension, and participation of organic molecules, are emerging as exciting alternatives to inorganic semiconductors and insulators for low cost, printable, and flexible electronics. Interfaces in such materials are integral to function, but are becoming increasingly complex in structure and chemistry. Quantitative imaging of all-organic or hybrid organic/inorganic nanomaterials is a formidable challenge to established electron optical methods. Laser-pulsed atom probe tomography (APT) is emerging as a potentially transformative analytical tool. In this project, supported by the NSF Solid State and Materials Chemistry Program, the experience of PI Joester will be leveraged in sample preparation, APT operation, and spectral interpretation to establish the scope of APT for the atomic-scale characterization of emergent organic and organic/inorganic hybrid materials from single nanoparticles to devices.
Specifically, it is proposed to investigate model systems for three important classes of materials: I) DNA-wrapped single wall carbon nanotubes (SWNT) as representatives of self-assembled building blocks for molecular electronic/optical devices. II) Self-assembled nano-dielectrics (SANDs) as examples for organic thin films in electronic applications. III) Ferritin nanocages with metallic and metal oxide nanoparticle payloads as examples for hybrid nanomaterials. In each case, APT has the potential to greatly facilitate future structure-function analyses. For example, APT imaging of DNA-wrapped SWNT will enable systematic investigation of impact of DNA sequence and nanotube chirality on the complex geometry and electronic properties. Outcomes will provide input for rational design of single chirality SWNT purification schemes and programmed assembly of CNTFET devices. Visualizing SAND atomic scale structure will dramatically enhance the ability to correlate processing, defect formation, and device performance. Model systems were selected to generate maximum synergy with existing research efforts at the NU MRSEC and the International Institute for Nanotechnology at NU. Proposed activities include research training for young investigators from undergraduates to postdocs and a summer school in atom probe tomography to disseminate hands-on skills beyond the project team.
NON-TECHNICAL SUMMARY: Rapid materials innovation is integral to enhancing US competitiveness in flexible/printable electronics, ultra-low power, or ultra-high speed circuits for emergent applications. Northwestern University is leading the development of all-organic and low dimensional organic/inorganic heterostructures such as carbon nanotube field effect transistors (CNTFETs) or self-assembled nanodielectric (SAND) thin films. However, shortcomings of current analytical tools hinder realization of the potential of these unconventional electronic materials. Laser-pulsed atom probe tomography (APT), an atomic scale quantitative chemical imaging tool with unrivaled spatial resolution and unbiased chemical selectivity, may rise to the challenge. In this project, funded by the NSF Solid State and Materials Chemistry Program, it is proposed to leverage the experience of PI Joester in APT to investigate model systems for 0D, 1D, and 2D hybrid electronic nanomaterials in close collaboration with leading experts and centers at NU. Outcomes of the proposed work will have immediate impact by facilitating structure-function studies and greatly accelerating innovation at NU and its partner institutions. Research areas impacted at NU include energy materials, nano-electronics, sensors, optical, and spintronic devices. In addition to training the next generation of scientists and engineers, the impact of the proposed activities will be significantly broadened by providing hands-on training in sample preparation techniques and APT to users outside the project team in a summer school on APT.
