Absolute quantum photo-yield of nanometer thick diamond films at their initial stages of formation

In this work we report on absolute quantum photoyield (QPY) measurements in the 140-220 nm (8.85-5.63 eV) photon energy range of nanometer thick diamond films. The QPY value at a photon wavelength of 140 nm increases with film deposition time from 2.5% (carbonized silicon substrate) to 14% for a nominal film thickness of 70 nm, followed by a decrease to 12% and stabilization for continuous films of thicknesses above ∼150-200 nm. Prior to QPY measurements the film's surface was conditioned by exposure to microwave hydrogen plasma, to induce negative electron affinity. The surface properties, phase composition and microstructure of the films were examined by electron spectroscopic and microscopic methods. Different factors are considered to explain the enhancement of QPY of the nano-metric thick films.