Résumé
Reducing the dimensions of mechanical resonators is a challenge that top-down technologies have difficulties to take up. In this context, bottom up nanomaterials are an interesting choice.I will show in this presentation how graphene and carbon nanotubes mechanical resonators can be interesting for a variety of topics ranging from fundamental mechanics to sensing.In a first part, I will focus on an optomechanical scheme to measure the intrinsic properties of graphene resonators. We demonstrated that the quality factor of those resonators is outstanding, above 10^6, if measured properly. In addition, we found that non-linearities play an important role in the motion of the resonator at these scales. We finally showed that it is possible to cool down the membrane to extremely low occupancy, near 7 phonons, and to reach a force sensitivity of ~ 400 zN/sqrt(Hz).In a second part, I will detail a more 'applied' work, where we have used a carbon nanotube both as a template and a probe for low-dimension superfluid Helium. We took advantage of the high crystalline quality and ultra-clean surface of the nanotube to grow Helium-4 films, layer by layer up to 5 layers. Thanks to the electrostatic tunability of the resonator, it was possible to separate the effects of mass and spring. This is useful for the interpretation of the low-temperature softening we observed in the Helium film, that we attributed to third sound waves rather than to superfluid decoupling.