The impact of H/D substitution on the structure, composition and thermal stability of grain boundaries in sub-micron diamond films deposited on silicon

Abstract

Sub-micron polycrystalline diamond films deposited using H 2/CH 4 gasses show Raman peaks at ~ 1130 and ~ 1470, which have been assigned to the ν 1 and ν 3 modes of t-PA hydrocarbons within the diamond intergranular space. Here we report the isotopic shift of these peaks in similar diamond films grown from D 2/CD 4 gas mixtures, as well as the splitting of the 1130 cm - 1 peak to two peaks at 880 and 855 cm - 1. We suggest that this unexpected peak splitting is due to an excess of short conjugated t-PA chains and relate this to the lower amount of amorphous carbon in these deuterated films, as evidenced by Raman spectroscopy and secondary ion mass spectrometry (SIMS). This difference in grai..