Effect of bonding and antibonding character of electronic states on their tunneling spectra

We argue that the bonding or antibonding character of electronic states a substrate can influence significantly observed scanning tunneling microscopy (STM) spectra. In particular, formed by nonorthogonal orbitals present much stronger extension in vacuum compared to corresponding combinations and are therefore more visible STM experiments. A clear example is provided black phosphorus (BP), which one most interesting two-dimensional layered materials nowadays. The pronounced asymmetry its conductance spectra, with significant increase at positive voltage, be attributed nature conduction band valence band, despite same ${p}_{z}$-orbital character. Furthermore, this origin different broadenings frontier molecular experimentally for molecules on BP.