Van der Waals stacking of multilayer In2Se3 with 2D metals induces transition from Schottky to Ohmic contact

Abstract

The rapid development of two-dimensional (2D) ferroelectric materials has significantly facilitated the design of new electronic nanodevices. During preparation, the contact between the metal electrode and 2D ferroelectric materials plays a key role in transport performance. However, the incorporation of traditional bulk metals and semiconductor is often accompanied by the Schottky barrier. Moreover, the strong Fermi level pinning (FLP) effect greatly inhibits the Schottky to Ohmic contact conversion. Herein, by contacting ferroelectric In2Se3 with 2D metals XY2 (X = Nb, Se; Y = S, Se), this not only releases lattice mismatch but also effectively weakens FLP effect. Density of states also clearly demonstrates that the metal-induced gap states are significantly suppressed. More importantly, the Schottky barrier height can be conveniently adjusted to convert into Ohmic contact by stacking bilayers of In2Se3. The multilayer In2Se3 can form a stronger polarized field since the 2D metals do not screen the intrinsic dipole of In2Se3. This induces the rise of valence band maxima and the reduction of conduction band minimum simultaneously. Based on the tunneling probability, the NbSe2 2D metal presents the optimal electrode for In2Se3 among these 2D metals researched. Our work offers a feasible strategy to advance the more effective 2D ferroelectric In2Se3-based nanodevices.