The study of the electronic transport through 2D nanomaterials and their stacked heterostructures have undergone great advances in the recent years. This is due to the fact that these are ultra-thin, highly flexible materials which form atomically defined interfaces and present interesting optical properties. One of the open issues about these 2D vertical heterostructures is the electronic transport mechanism between their composite atomic planes. In this sense, SPM techniques, in special the CAFM measurements have been applied to deepen the knowledge of the electronic behavior of these systems. Furthermore, the small contacr area (~1E-15 m2) allows for studying the properties of these systems in extreme conditions (pressures on the order of GPa).

In this work we discuss the latest developments in the pressure dependence of the vertical transport of thin samples of 2D materials using the CAFM technique. In these experiments a conducting AFM tip is contacted to a the 2D material flake which has been deposited on a conductive substrate. The electric current between the substrate and the AFM tip is measured as a function of the applied bias and the loading force. Recent measurements performed on few-layer MoS2 on a micropatterned gold contact showed that for loading forces below a hundred nanoNewtons (~0.1 GPa), the system behaves as a back-to-back combination of diodes, with one diode performing almost ideally. As the loading force is increased above a few hundreds of nanoNewtons, the conductivity of the system grows abruptly, such that at pressures approaching 1 GPa the system behaves as a conductor. The transition pressure increases with increasing number of layers. We also discuss how different tip and substrate materials affect the overall results and the possibility of studying differently stacked heterostructures.