title: Full Characterization of the Mechanical Properties of 11-50 nm Ultrathin Films: Influence of Network Connectivity on the Poisson's Ratio.
abstract: Precise characterization of the mechanical properties of ultrathin films is of paramount importance for both a fundamental understanding of nanoscale materials and for continued scaling and improvement of nanotechnology. In this work, we use coherent extreme ultraviolet beams to characterize the full elastic tensor of isotropic ultrathin films down to 11 nm in thickness. We simultaneously extract the Young's modulus and Poisson's ratio of low-k a-SiC:H films with varying degrees of hardness and average network connectivity in a single measurement. Contrary to past assumptions, we find that the Poisson's ratio of such films is not constant but rather can significantly increase from 0.25 to >0.4 for a network connectivity below a critical value of ∼2.5. Physically, the strong hydrogenation required to decrease the dielectric constant k results in bond breaking, lowering the network connectivity, and Young's modulus of the material but also decreases the compressibility of the film. This new understanding of ultrathin films demonstrates that coherent EUV beams present a new nanometrology capability that can probe a wide range of novel complex materials not accessible using traditional approaches.
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Jorge N
authors.identifier: 0000-0003-3296-6929
authors.initials: JN
authors.lastname: Hernandez-Charpak
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.|Intel Corp., 2501 NW 229th Avenue, Hillsboro, Oregon 97124, United States.
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Hoogeboom-Pot
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Qing
authors.initials: Q
authors.lastname: Li
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Travis D
authors.initials: TD
authors.lastname: Frazer
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Joshua L
authors.initials: JL
authors.lastname: Knobloch
authors.affiliation: Intel Corp., 2501 NW 229th Avenue, Hillsboro, Oregon 97124, United States.
authors.forename: Marie
authors.initials: M
authors.lastname: Tripp
authors.affiliation: Intel Corp., 2501 NW 229th Avenue, Hillsboro, Oregon 97124, United States.
authors.forename: Sean W
authors.initials: SW
authors.lastname: King
authors.affiliation: Center for X-ray Optics, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Erik H
authors.initials: EH
authors.lastname: Anderson
authors.affiliation: Center for X-ray Optics, Lawrence Berkeley National Laboratory , Berkeley, California 94720, United States.
authors.forename: Weilun
authors.initials: W
authors.lastname: Chao
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Margaret M
authors.initials: MM
authors.lastname: Murnane
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.
authors.forename: Henry C
authors.initials: HC
authors.lastname: Kapteyn
authors.affiliation: JILA and Department of Physics, University of Colorado , Boulder, Colorado 80309-0440, United States.|Intel Corp., 2501 NW 229th Avenue, Hillsboro, Oregon 97124, United States.
authors.forename: Damiano
authors.initials: D
authors.lastname: Nardi
keywords: Ultrafast X-rays; nanomechanical properties; nanometrology; photoacoustics; ultrathin films