Síntese a baixa temperatura de materiais bi-dimensionais de carbono: impacto da simetria do precursor sobre a morfologia dos materiais

Abstract

In 2010, Geim and Novoselov won the Nobel Prize by showing that electrons in monolayer graphene behave like massless particles - Dirac fermions - being able to move at the speed close to the speed of light within this material. This property attracted the attention of the scientific community. Graphene is hexagonal network of pure carbon atoms hybridized sp2. Since it has a atomic thickness, it is considered a 2D material. Graphene can be obtained by chemical vapour deposition (CVD), with which we obtain highly crystalline material. It can be used in organic electronic because it is a transparent conductor material. On the other hand, in field effect (FETs) the devices never turn off because graphene is a semiconductor of GAP zero, and there are always electrons available for conduction. A way of solving this problem is to open a GAP in the electronic band dispersion by controlling the morphology of the material. Some recent works, employed liquid precursors to precisely control the molecular geometry of nanoribbons. Other researches employed toluene and benzene to grow monolayer graphene at low temperature (100~300 °C). However, the authors did not correlate the geometry of the precursor with a possible break of symmetry concerning the growing direction. In this work, we investigate if the format of the liquid precursor liquid affects the synthesis of graphene, and the format of crystallites in such a way that we can control them. Thus, we studied a mechanism of synthesis of graphene much more simple than those obtained in the literature, using low temperatures, and the dehydrogenation of the precursor liquid. The CVD process can be performed at low pressures (Low Pressure CVD - LPCVD), of the order of 10−2 or 10−4 torr. In this work, we use pressures of one atmosphere (Ambient Pressure CVD - APVCD), which has the advantage of being a process less expensive than LPCVD. In addition, one can grow graphene at low temperatures with APCVD, which facilitates the manufacture of devices organic, as most organic molecules are destroyed at temperatures of the order of 1050ºC. Through control of the morphology of the graphene, we hope to control their electronic properties, expanding its use in electronic devices and optoelectronic.