Ultrafast photoluminescence of nanocrystalline diamond films

Abstract

Abstract We report on ultrafast photoluminescence of nanocrystalline diamond membranes and films on silicon and fused silica glass measured by femtosecond upconversion technique. The nanodiamond samples were prepared by microwave plasma enhanced CVD technique. Photoluminescence with very fast non‐exponential decay with the effective time of about 1 ps was observed in the investigated spectral interval 1.8–2.8 eV. The decay was spectrally dependent being faster at higher photon energies. We have found that the photoluminescence dynamics are affected by temperature and ambient pressure. We interpret the photoluminescence dynamics in terms of charge‐carrier relaxation via the continuum of the nanocrystal surface‐related energy states lying energetically below the diamond band‐gap energy. The results can be explained by the spectral dependence of the density of these states and its changes due to ambient conditions. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)