Investigation of phosphorus-doped nanocrystalline diamond films for effective electron photoemission under picosecond laser pulses

Phosphorus-doped nanocrystalline diamond (P-NCD) films deposited by the chemical vapor deposition method on conductive silicon substrates have been experimentally studied. The grown 100 nm-thick films were characterized by a high content of the diamond carbon phase, which allowed the films to be doped with phosphorus (during growth) to achieve predominant incorporation of phosphorus atoms into diamond grains rather than at the grain boundaries. The photoemission properties of the grown doped and undoped as-grown NCD films were tested, demonstrating different photoemission properties under the influence of a picosecond laser pulse. For undoped NCD films, the emitted charge increased linearly with increasing laser pulse energy, while for phosphorus-doped P-NCD films, it increased quadratically. It was found that the presence of phosphorus in the doped film was responsible for the change from linear to quadratic. This dependence in photoemission from P-NCD films was observed for the first time. An explanation for the quadratic increase in emitted charge with increasing laser pulse energy is proposed.