Electrostatic doping determined by band alignment in graphene on ferroelectric LiNbO3(0001) polar surfaces

Abstract

Herein, first-principles density functional theory calculations are performed to investigate the interface coupling and electrostatic doping effect in the graphene/LiNbO3(0001) [denoted as Gr/LNO(0001)] heterostructure. The results show that, in addition to the coupling mechanism of the large ionic–van der Waals interaction, an unusual electrostatic doping, which is in contrast with the polarization compensation mechanism, appears in the Gr/LNO(0001) system: for graphene adsorbed on the thermodynamically preferred ferroelectric LiNbO3(0001) [denoted as LNO(0001)] positive (Z+) and negative (Z−) surfaces, carriers are of p- and n-type, respectively. Further analysis indicates that the electrostatically doped effect of the graphene layer adsorbed on the LNO(0001) polar surfaces should be determined by the particular band alignment between the LNO(0001) polar surfaces and graphene. Our studies provide theoretical evidence for designing p–n homojunctions in a graphene sheet by engineering the domain structure of the LNO(0001) ferroelectric substrates. Furthermore, the significant change in carrier density caused by the reversal of the ferroelectric polarization direction suggests that the Gr/LNO(0001) system could be a promising platform to explore ferroelectric field-effect transistors.