AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Monday Sessions
       Session NS+SS-MoM

Paper NS+SS-MoM10
Lubrication Brought to Light: Optical Signatures of Nanomechanical Effects in Organic Thin Films

Monday, November 2, 1998, 11:20 am, Room 321/322/323

Session: Tribology, Adhesion and Interfacial Forces
Presenter: R.W. Carpick, Sandia National Laboratories
Authors: R.W. Carpick, Sandia National Laboratories
D.Y. Sasaki, Sandia National Laboratories
S. Singh, Sandia National Laboratories
A.R. Burns, Sandia National Laboratories
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The properties of organic lubricant films composed of hydrocarbon chain molecules is currently of great interest, as the detailed molecular response of these films to mechanical stress remains to be understood. Molecular films of polydiacetylenes are composed of ordered hydrocarbon chains attached to a chromophoric polymer backbone. These materials exhibit strong fluorescence emission and optical absorption which can be altered by mechanical stress (mechanochromism), providing the opporutunity to exploit the optical response as a signature of specific molecular behavior. Furthermore, structurally distinct chromatic phases ("blue" and "red" phases) of the film can be produced by a combination of Langmuir-Blodgett deposition and photopolymerization. We have studied the response of these films to mechanical stress at the nanometer level using a novel scanning force microscope. The instrument combines near-field optical detection with a displacement-controlled (non-compliant) normal force sensor and a decoupled lateral force sensor. Nanomechanical properties, including local elastic modulus, adhesion, and friction are compared for different chromatic phases of the film. We examine the modes of film deformation at the molecular level by monitoring the fluorescence emission while varying the mechanical stress applied to a nanometer-sized contact area. * Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy under Contract DE-AC04-94AL85000.