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Band gap reconstruction at the interface between black phosphorus and a gold electrode

We experimentally investigate charge transport through the interface between a gold electrode and a black phosphorus single crystal. The experimental $dI/dV(V)$ curves are characterized by well developed zero-bias conductance peak and two strongly different branches. We find that two branches of asymmetric $dI/dV(V)$ curves correspond to different band gap limits, which is consistent with the theoretically predicted band gap reconstruction at the surface of black phosphorus under electric field. This conclusion is confirmed by experimental comparison with the symmetric curves for narrow-gap (WTe$_2$) and wide-gap (GaSe) metal-semiconductor structures. In addition, we demonstrate p-type dopants redistribution at high bias voltages of different sign, which opens a way to use the interface structures with black phosphorus in resistive memory applications.