AVS 47th International Symposium
    Processing at the Nanoscale/NANO 6 Tuesday Sessions
       Session NS+NANO6+MM-TuM

Paper NS+NANO6+MM-TuM6
Size-Dependent Mechanical Properties of MoO@sub 3@ Nanoplates

Tuesday, October 3, 2000, 10:00 am, Room 302

Session: Nanomechanics
Presenter: J. Wang, Harvard University
Authors: J. Wang, Harvard University
K.C. Rose, Harvard University
J.W. Hutchinson, Harvard University
C.M. Lieber, Harvard University
Correspondent: Click to Email
The mechanical properties of materials on the nanometer scale are of great interest both for furthering our fundamental understanding as well as for use in a wide range of micro- and nano-mechanical systems. Previous experimental studies have focused on one-dimensional systems, including carbide nanorods and carbon nanotubes. For example, atomic force microscopy (AFM) has been used to show that silicon carbide nanorods have similar Young's moduli to defect free macroscopic crystals and that carbon nanotubes are much stiffer than carbon whiskers and fibers. Here, we used AFM to determine the bending stiffness of individual, structurally-isolated molybdenum oxide (MoO@sub 3@) nanocrystal nanoplates (5-16 nm thick). These nanoplates were pinned to molybdenum disulfide (MoS@sub 2@) surfaces on one side and were suspended freely over MoS@sub 2@ steps on the other side. Bending forces were measured versus displacement on the unpinned side of these MoO@sub 3@ nanoplates. Finite element analysis revealed that the effective Young's moduli of these MoO@sub 3@ nanocrystals are significantly smaller than that of bulk MoO@sub 3@ single crystals and that the moduli decrease with decreasing nanocrystal thickness. This novel behavior was further substantiated in subsequent experiments where it was shown that MoO@sub 3@ nanocrystals (1.4 - 5 nm thick) had enormous flexibility when slid over multilayer MoS@sub 2@ steps. These results have important implications for the sliding of nanoscale structures on rough surfaces and even for the fabrication and manipulation of smaller mechanical systems evolving in nanotechnology.