IRG 3: Adhesion, Deformation And Transport At Contacts In Small Structures

Top photo, left to right: Antoine Kahn (co-leader), Giacinto Scoles, Annabella Selloni, Stefan Bernhard, Roberto Car, Kyle Vanderlick (co-leader)

Bottom row, left to right: Steve Forrest, Wole Soboyejo, David Srolovitz

Many state-of-the-art microelectronic, photonic and MEMS devices are based upon small scale contacts for which performance and fabrication are governed by the deformation, adhesion, and transport properties of many diverse materials and interfaces. Examples include a recently introduced adhesion-based lift-off patterning method for forming contacts to organic electronic devices and high frequency, microscale electromechanical switches. Yet despite the widespread use of such devices, there is only a limited understanding of the phenomena governing adhesion, a shortfall that has seriously impeded science-based design and analysis, especially as the devices become smaller and new materials and functions are introduced.

Existing protocols for robust design on the macroscale have derived primarily from developments in solid mechanics and electromagnetics, manifest in commercially available continuum codes (e.g., finite element methods). The main assumptions underlying these protocols become invalid at the nano-scale, below ~50 nm, because as plastic flows become discrete, failure phenomena become nucleation rather than propagation controlled, and electrical conductivity becomes ballistic or becomes confined along individual molecules in contacts. To address these challenges, a new “atom-aware, mechanics-based” protocol is needed, requiring: small scale probes, atomic scale structure resolution, ultra-sensitive deformation and adhesion measurements, precise conductivity measurements, high resolution microscopy, ab-initio and atomistic simulations, and modeling of morphology evolution and interfacial structure.

The primary focus of this IRG is to develop the multi-disciplinary science that governs the fabrication and operation of a broad class of new, small-scale devices that depend upon electrical contacts.

Selected Publications:

• C. Kim, Y. Cao, W. O. Soboyejo, S. R. Forrest, “Patterning of Active Organic Materials by Direct Transfer for Organic Devices”, J. Appl. Phys., 97, 113512 (2005).
• A. Salomon, T. Boeckling, C.K. Chan, F. Amy, O. Girshevitz, D. Cahen, and A. Kahn, “How Do Electronic Carriers Cross Si-Bound Alkyl Monolayers? ”, Phys. Rev. Lett., 95, 266807 (2005).
• S. Möller, C. Perlov, W. Jackson, C. Taussig and S. R. Forrest, “A Polymer/Semiconductor Write Once Read Many Times Memory Element”, Nature, 426, 166 (2003).