Electronic transport in carbon nanotubes under pressure

J.-C. Blancon1, L. Marty2, A. Ayari1, A. San Miguel1

1LPMCN & LASIM, Université Lyon 1, Domaine Scientifique de la Doua, 69622 Villeurbanne, France2Institut Néel, CNRS et Université Joseph Fourier, BP 166, F-38042 Grenoble Cedex 9, France

Carbon nanotubes (CNTs) and graphene exhibit interesting electrical properties making them good candidates for the development of new nano-electronic devices. These materials are promising in the field of pressure nano-sensing. Such devices aim at utilising the high pressure-sensitivity of contact states between graphene or CNT and lithographed metallic contacts [1]. Additional insights in the strain-induced behaviours of these objects are gained while focusing on the pressure-evolution of their intrinsic electronic properties. Some model predict an evolution of the nanotubes cross-section under pressure (Fig. 1), but up to now nobody has been able to observe its influence on their intrinsic electronic transport properties. Moreover, theoretical calculations predict transition metal/semiconductor or semiconductor/ metal in CNTs, as well as the opening of a gap in graphene. We have developed a new system to perform transport measurements on CNTs and graphene under high pressure and at low temperature [2]. This unique system probes directly the changes occurring in the electronic structure of these two types of materials under pressure.

In this work, we present preliminary results of the electrical response of individual semiconducting CNTs under hydrostatic pressure, both at ambient and low temperatures. On the one hand, we observed the pressure-dependent field-effect transistor responses of nanotubes up to 0.9 Gpa at ambient temperature. Our data show clearly an evolution of the electronic properties for different pressures. At low pressure, alteration of contact states between the CNTs and their metal contacts are predominant. At higher pressures, two effects take place being the intrinsic mechanical changes in the CNTs cross-section, and the evolution the adhesion-state of the CNT on a rough surface coupled with substrate-CNT charge transfer mechanisms. On the other hand, we present the first transport measurements performed at both low temperature and high pressure on an individual nano-object (Fig. 2). In fact, single-electron transistor (SET) responses of nanotubes were measured at pressures up to 0.4 GPa.

fig1-HPSP
Fig. 1: Sketch of the evolution of carbon nanotubes cross-section under pressure. The ovalization process is observed in the low pressure range (middle) while nanotubes are collapsed at higher pressure (right).[2]

fig2-HPSP
Fig. 2: SET response observed in a semiconducting CNT at 4.5 kbar. The source-drain tension is 15 mV.

References
[1] C. Caillier et al., App. Phys. Lett. 2010, 97, 173111.
[2] C. Caillier et al., Advanced Functional Materials 2010, 20, 3330.
[3] A. L. Aguiar et al., The Journal of Physical Chemistry C 2011, 115, 5378.