Nanocrystalline diamond films growth by microwave ECR CVD: Studies of structural and photoconduction properties

• Nanodiamond films were grown using ECR CVD by BEN process.
• XRD, HRTEM measurements showed formation of diamond nanocrystals with different sizes.
• Raman, PL measurements indicate presence of amorphous carbon and sp2 carbon clusters in the films.
• I-V measurements show higher photocurrent in film with smaller diamond nanocrystals and more sp2 carbon clusters.

We report studies on growth of nanocrystalline diamond films by electron cyclotron resonance chemical vapour deposition (ECR CVD) and their structural and photoconduction properties. Bias enhanced nucleation (BEN) under higher methane partial pressure has been used to grow diamond nanocrystals with sp2 carbon clusters at grain boundaries in an amorphous carbon matrix. Structural studies indicate the size of diamond nanocrystals decreased and sp2 content increased in the films with increase in methane partial pressure, which is explained using subplantation model. Current- Voltage (I-V) measurements under dark and deep ultraviolet (DUV) light illumination conditions showed higher photocurrent in films with smaller sized diamond nanocrystals (3 nm–8 nm) compared to films having diamond nanocrystals of larger size (∼15 nm). The results indicates that the photocurrent generated in the films has major contributions from photoexcited electrons in diamond nanocrystals and sp2 carbon nanoclusters, with minor contribution from amorphous carbon phase.