Observation of field-induced deformation on Pb films and suspended graphene
Wei-Bin Su1*
1Institute of Physics, Academia Sinica, Taipei, Taiwan
* presenting author:蘇維彬, email:wbsu@phys.sinica.edu.tw
We use scanning tunneling microscopy (STM) and spectroscopy to observe the energy shifts of the quantum well states in Pb islands under the electric field in STM gap. By measuring the energy shift at different electric field, it is found that the surface atoms can be displaced outward by the electrostatic force, which can subsequently induce the movement of atoms in the film to establish an expansion deformation. It is also observed that the expansion is proportional to the film thickness. By using the phase accumulation model, we estimate that the expansion of the interlayer spacing is 0.01 Å, which is a very subtle deformation. However, the field-induced deformation would be largely increased if the material is the suspended graphene with one atomic layer thickness. We have observed a field-induced deformation of 750 nm on a suspended graphene with a size of 60 μm by using the Raman scattering enhanced by the micrometer-size gold tip. From the measured deformation, we can further estimate that the Young’s modulus of graphene is about 1.48 TPa.

Keywords: scanning tunneling microscopy and spectroscopy, quantum well states, suspended graphene, tip enhanced raman scattering, field-induced deformation