AVS 53rd International Symposium
    Nanometer-scale Science and Technology Wednesday Sessions
       Session NS+SS+TF-WeM

Paper NS+SS+TF-WeM9
Measurements and Modeling of Shear Modulus of Multiwalled Tungsten Disulfide Nanotubes

Wednesday, November 15, 2006, 10:40 am, Room 2016

Session: Nanotribology and Nanomechanics
Presenter: S.R. Cohen, Weizmann Institute of Science, Israel
Authors: I. Kaplan-Ashiri, Weizmann Institute of Science, Israel
S.R. Cohen, Weizmann Institute of Science, Israel
N. Apter, Weizmann Institute of Science, Israel
H.D. Wagner, Weizmann Institute of Science, Israel
R. Tenne, Weizmann Institute of Science, Israel
G. Seifert, Technische Universitat Dresden, Germany
R. Shneck, Ben Gurion University, Israel
D. Barlam, Ben Gurion University, Israel
Correspondent: Click to Email
Recent investigations of the mechanical properties of inorganic fullerene have highlighted their unique properties.@footnote 1@ Although the bending modulus has been measured on single nanotubes, the shear modulus is much smaller and technically more difficult to ascertain. The S-W-S sandwich structure of individual layers of these inorganic nanotubes distinguish them chemically and mechanically from carbon nanotubes. The spacing of 6.18Å between layers is comprised of the tungsten disulfide entity, and a van der Waals gap. Direct measurements of the shear modulus of single tubes could elucidate how the tube mechanics are influenced both by the gap, and the interaction between the adjacent dichalcogenide atomic layers. Measurements were made in a scanning probe microscope (SPM) using a method similar to that described by Wu et al.:@footnote 2@ Nanotubes were dispersed on a grid structure consisting of trenches of depth 200 nm and width 500 nm. Scanning electron microscopy (SEM) was used to locate nanotubes which were appropriately aligned, and suspended over such a trench. These nanotubes were then glued to the substrate at the trench edge with amorphous carbon.@footnote 3@ The SPM was subsequently used to bend the suspended nanotubes from the side with the SPM probe by amounts ranging between 5 and 100 nm, while recording the lateral force. The results were analyzed by applying the bending equation using the known value of the bending modulus to extract shear modes. Results were further compared with both density functional calculations, and finite element analysis modeling, providing insights into mechanical interactions between the layers. @FootnoteText@ @footnote 1@ I. Kaplan-Ashiri, et al, Proc. Nat. Acad. Sci. 103, 523 (2006).@footnote 2@ B. Wu, et al, Nature Mat. 4, 525 (2005).@footnote 3@ Yu et al, Science 287, 147 (2000).