Influence of intercalated Gd atoms on graphene-4H-SiC(0001) properties

Abstract

In this work, the influence of intercalated gadolinium (Gd) atoms on graphene-4H-SiC(0001) properties are presented, using X-ray photoelectron spectroscopy, low energy electron diffraction and density functional theory calculations. Detailed analysis, ranging from adsorption to temperature induced intercalation under the graphene, of the chemical composition, surface structures, charge transfer and changes in the graphene band structure is performed. The investigation is carried out for various initial Gd film thicknesses and temperature of annealing, which allows to obtain and observe interactions between elements in the subsequent stages of intercalation. Calculations show that the deeper Gd is placed into the substrate the more energetically favourable configuration is obtained, which indicates the possibility of intercalation process to occur. Moreover, intercalated Gd strongly affects the electronic properties of both graphene and buffer layer. Simultaneously, experiment results show that Gd induces n-type doping in graphene. Additionally, temperature induced intercalation causes the buffer layer decoupling and transformation into new graphene one. The presence of gadolinium at the graphene-SiC interface results also in chemical shifts to the lower binding energy range and follows the trend in which the more gadolinium intercalates the higher shift is observed.