Electric metal contacts to monolayer blue phosphorus: electronic and chemical properties

The contact nature when monolayer blue phosphorus (blueP) interfaces with three transition metal electrodes (i. e., Pd, Ir, and Pt) was unraveled by the ab initio density functional theory calculations. Specifically, n-type Schottky contact is observed for Ir(111)-blueP, in contrast, p-type Schottky contacts are formed for Pd(111)- and Pt(111)-blueP. The Fermi level is pinned partially at metal-blueP interfaces due to two interfacial behaviors: one being the modification of metal work function caused by interface dipole formation ascribed to a redistribution of charges, and the other being the production of gap states that are dominated by P p-orbitals since the intralayer P-P bonds are weakened by the interfacial metal-P interactions. The incorporation of metal substrates would also significantly alter the chemical properties of the adsorbed monolayer blueP. The binding strength of hydrogen can be enhanced by as much as 0.9 eV, which resulted from two parts: one is the charge transfer from metal substrate to monolayer blueP rendering a stronger H-P coupling; the other is a strong interfacial interaction after the hydrogen adsorption. The free energy change of H adsorption onto Ir(111)-blueP is as low as 0.16 eV which is comparable to the most efficient catalyst of Pt. These findings would provide theoretical guidance for the future design of electronic devices based on blueP and exploration of its potential in novel catalysts for hydrogen evolution reaction.

Automated summary

The nature of the contact between monolayer blue phosphorus and transition metal electrodes was investigated using density functional theory calculations. The results showed different types of Schottky contacts for different metals, with the Fermi level pinned at the metal-blueP interfaces due to interface dipole formation and the production of gap states dominated by P p-orbitals. The addition of metal substrates also significantly altered the chemical properties of the adsorbed monolayer blueP, enhancing the binding strength of hydrogen and making it comparable to Pt catalysts. These findings provide theoretical guidance for the design of electronic devices based on blueP and the development of novel catalysts.