Estudo de sistemas de chaveamento resistivo baseados em TiO2: SnO2 MoS2

Abstract

In this thesis we investigate resistive switching processes in two distinct systems: the firts is TiO2, a standard compound used for resistive memories, with well known properties. In order to search for new possibilities SnO2 nanoparticles were inserted at the bottom of a TiO2 thin film, modifying the processo f formation of a condutive channel. Such channel consists of a non-stoichiometric oxide trail, where electronic conduction is favored over other areas of these devices. Conductive channels are partially reversible, switching from high-resistance to low resistance states depending on the polarity and intensity of the applied electric field. We show here unambiguously that SnO2 nanoparticles can guide the formation of such channels, being compatible with the exisisting TiO2 technology. A similar phenomenon is also investigated in MoS2 multilayers. For such compound resitive switching was previously observed in single layers. In our work it was possible to find a unipolar switching for the application of electric field across the layers (in the stacking direction). Scanning tunneling microscopy measurements show that impurities do nottake a major role in the conductive channel formation, which do not form at low temperatures ( below 90K)