2 research outputs found
Strain Discontinuity, Avalanche, and Memory in Carbon Nanotube Serpentine Systems
This work addresses the problem of
how a nano-object adheres to a supporting media. The case of study
are the serpentine-like structures of single-wall carbon nanotubes
(SWNTs) grown on vicinal crystalline quartz. We develop in situ nanomanipulation
and confocal Raman spectroscopy in such systems, and to explain the
results, we propose a dynamical equation in which static friction
is treated phenomenologically and implemented as cutoff for velocities,
via Heaviside step function and an adhesion force tensor. We demonstrate
that the strain profiles observed along the SWNTs are due to anisotropic
adhesion, adhesion discontinuities, strain avalanches, and memory
effects. The equation is general enough to make predictions for various
one- and two-dimensional nanosystems adhered to a supporting media
Characterization of Few-Layer 1Tā² MoTe<sub>2</sub> by Polarization-Resolved Second Harmonic Generation and Raman Scattering
We study the crystal
symmetry of few-layer 1Tā² MoTe<sub>2</sub> using the polarization
dependence of the second harmonic
generation (SHG) and Raman scattering. Bulk 1Tā² MoTe<sub>2</sub> is known to be inversion symmetric; however, we find that the inversion
symmetry is broken for finite crystals with even numbers of layers,
resulting in strong SHG comparable to other transition-metal dichalcogenides.
Group theory analysis of the polarization dependence of the Raman
signals allows for the definitive assignment of all the Raman modes
in 1Tā² MoTe<sub>2</sub> and clears up a discrepancy in the
literature. The Raman results were also compared with density functional
theory simulations and are in excellent agreement with the layer-dependent
variations of the Raman modes. The experimental measurements also
determine the relationship between the crystal axes and the polarization
dependence of the SHG and Raman scattering, which now allows the anisotropy
of polarized SHG or Raman signal to independently determine the crystal
orientation