Abstract
Polycrystalline diamond, as a composite material, primarily consists of sp(3) and sp(2) hybridized carbon phases in different ratio. The amount of grain boundaries, sp(2) non-diamond carbon phase and other defects and impurities play a crucial role in relaxation and recombination of photo-excited charge carriers in diamond films.
The transient transmission measurements are performed using non-degenerate pump and probe technique using few-cycle laser pulses with temporal resolution of similar to 15 fs. We show that the initial processes occurring after interaction of light with diamond membranes are sensitive to the sp(3)/sp(2) ratio phases.
We propose a simple microscopic model of electron relaxation via sub-gap energy levels caused by surface states, sp(2) carbon phase and defects of the crystal lattice of diamond grains.