Since a few years, it is possible to isolate sheets with thickness of an atom and width of dozens of micrometers. It is possible to proceed with metallic, insulating, or semi-conductors materials and to assemble them in various heterostructures. One of these materials is the MoS2. However, few experiences were made on suspended membranes of this material in a controlled way and where the strain can be modulated. By taking into account the 2D confinment and the high tunability of the crystalline structure, for example by means of the mechanical stress, this interseting material possesses various surprising properties for electrons, as for photons or phonons.
Researchers of the Centre de Nanosciences et de Nanotechnologies/Centre for Nanoscience and Nanotechnology – C2N (CNRS/Université Paris-Sud), in collaboration with the University of Pennsylvania, have studied a new sample type with large monolayer MoS2 deposited on carpets of SiO2 pillars, with electrical contacts. With the control over pillars geometry, they were able to create periodic networks of high-quality mechanical resonators. Their work is published in the journal ACS Nano.
To reach it, it was necessary, at first, to extract by microRaman, the intrinsic properties of our system: the doping, the thermal conductivity and especially the stress engendered by pillars, and this for numerous types of geometries. The researchers demonstrated for the first time that it is possible to obtain a high-quality and homogeneous system over many periods of pillars. This type of hybrid structure of opto-electro-mechanic (NOEMS) couples at the same time the nanomechanics with interesting properties of the MoS2 as very strong photocurrent, electronical memory effects or another localized optical emission engendered by the fold of the MoS2 by pillars.
Figure: On the left, some sample of monolayer MoS2 suspended on SiO2 pillars array with a schematic. On the right, a diagram of the respective peak position obtained by Raman spectroscopy, which discriminate the strain, doping or heating. It is possible to correlate a predominant MoS2 property variation with a specific pillars array design. © C2N / J. Chaste
Reference:
Intrinsic Properties of Suspended MoS2 on SiO2/Si Pillar Arrays for Nanomechanics and Optics,
J. Chaste1, A. Missaoui1, S. Huang1, H. Henck1, Z. Ben Aziza1, L. Ferlazzo1, C. Naylor2, A. Balan2, A. T. C. Johnson2, R. Braive1,3, A. Ouerghi1, ACS Nano (2018)
DOI: doi:10.1021/acsnano.7b07689
1 Centre de Nanosciences et de Nanotechnologies – C2N (CNRS/Université Paris-Sud)
2 Department of Physics and Astronomy, University of Pennsylvania, USA
3 Université Paris Diderot, Sorbonne Paris Cité
Contact: Julien Chaste, CNRS researcher at C2N
