Formation of quasi two-dimensional allotropes of phosphorus on metal substrates

Quasi 2D phosphorous in phosphorene (black-P) and blue-phosphorous (blue-P) forms are receiving an increased interest for their potential in flexible and tunable electronics. Recently, the synthesis of blue-P was demonstrated on transition metal or alloy surfaces, with black-P not grown epitaxially on any substrate to date. Our experiments confirm that the high phosphorus vapor pressure and reactivity lead mostly to the formation of metal phosphides or amorphous phosphorous with a narrow window for blue-P. Modeling efforts that assume black- and blue-P on Cu and Ag as final products show that blue-P is slightly favored by a bonding between the P-half layers that is stronger than the lower half layer-metal bond. Here, we investigate computationally the catalytic activity of various metal surfaces, which could potentially enable a stronger bonding of the lower layer. The phosphorus adsorbates have a large effect on the metal atoms which they are closest to, and strong hybridization between the p orbitals of phosphorous and d orbitals of the substrate is found, suggesting a strong coupling. Besides its impact on the material properties and possible applications, this provides a way to gain insight into the controlled formation of the allotropes of phosphorous on the metal surfaces.