Red Phosphorus by Atomic Layer Deposition

Herein, a new synthetic procedure for red phosphorus (RP) by atomic layer deposition (ALD) is presented. The deposition of RP thin films was obtained by combining tin tetrachloride and home-synthesized tris(trimethyltin)phosphide. The ALD window was identified between 175 and 200 °C, and the self-limiting nature of the ALD process was verified. The RP thin films deposited on Si/SiO₂ wafer, soda lime glass, and carbon paper were extensively characterized by different techniques, revealing that the phosphorus was deposited exclusively as elemental RP without any concomitant phosphorus species. The assessment of the optical properties revealed an optical bandgap of ≈1.9 eV confirming the semiconducting nature of the RP thin films. To gain valuable insight into the ALD reaction mechanism, density functional theory calculations suggested a plausible mechanism that combined ligand exchange and redox steps. This work extends the portfolio of ALD precursors and fills the gap in the missing deposition of elemental P.