Desegregation of boron at the grain boundaries of the in situ boron doped diamond films

High quality in situ boron doped polycrystalline diamond films were grown on the scratched Si (100) substrate. A saturated deionized water solution of boron acid was chosen as a dopant source. The concentration profiles of boron, tantalum, and oxygen were examined by using scanning Auger nanoprobe and secondary ion mass spectroscopy. The boron atoms are uniformly distributed inside each diamond grain. However, no Auger signal from boron was observed at grain boundaries within the detection limit. In contrast, tantalum atoms are uniformly distributed across diamond grains and grain boundaries. A simple model was proposed in explaining the boron desegregation.