Influência de impurezas ionizadas e moléculas adsorvidas no mecanismo de transporte elétrico de grafeno

Abstract

The discovery of graphene and methods to isolate it raised the prospect of a new class of nanoelectronic devices based on its physical and electrical properties. Soon enough it was discovered that its electronic properties are strongly sensitive to the environment and also by molecules assembled on its surface. In this context, studies regarding the interaction between hydrogen (H2) and graphene devices have become particularly important due to the possibility of using graphene as a hydrogen storage material, besides a new type of gas sensor devices. In this work, the electronic properties of monolayer graphene have been investigated (in situ) under the exposure of molecular hydrogen. We have measured the conductivity versus gate voltage of graphene devices at different temperatures. Experiments during H2 adsorption and desorption at different conditions of hydrogen concentration and temperature were performed. The field-effect transistor mobility of graphene is shown to be highly sensitive to H2 exposure, demonstrating its direct effect on graphene charge scattering mechanisms. Furthermore, it is shown that the H2 infiltrates between the graphene sheet and SiO2 behaves as short-range scattering centers that cause an asymmetric effect in the hole and electron mobilities under hydrogen interaction. More than that, we show that the whole process is fully reversible and happens in all temperatures analyzed. In summary, this work shows a reproductive form of modification of intrinsic electronic properties of graphene devices through adsorption of hydrogen molecules. We also conclude that the changes observed are due to gas interaction process and, thus, demonstrate the ability to use systems such as sensors or gaseous hydrogen storage.