Structural and optical properties of boron-doped amorphous carbon nitride thin films synthesized by microwave electron cyclotron resonance-plasma chemical vapor deposition

The structural and optical properties of boron (B)-doped amorphous carbon nitride (a-CNx) thin films with a B content of less than 10 at. % were investigated. The B-doped a-CNx thin films were synthesized by electron cyclotron resonance (ECR)-plasma chemical vapor deposition (CVD) by varying the substrate temperature and flow rate ratio of the source gases (BCl3/CH4/N2/Ar). An increase in the B content and a decrease in the Cl content were observed with increasing substrate temperature. The Tauc energy gap of the B-doped a-CNx thin films increased with decreasing C-N sp2 bond fraction and increasing B content. The photoluminescence (PL) peak position showed larger blue shifts and a tendency of increased integrated PL intensity was observed with increasing B content. These PL results suggest an increase in PL-active B-related sp2 C-C bond cluster density.