Ultrananocrystalline Diamond Nano-Pillars Synthesized By Microwave Plasma Bias-Enhanced Nucleation And Bias-Enhanced Growth In Hydrogen-Diluted Methane

Bias-enhanced nucleation and growth of ultrananocrystalline diamond (UNCD) nano-pillars on silicon substrates by low-pressure microwave plasma chemical vapor deposition in a hydrogen-rich gas mixture with methane is reported. Direct-current biasing of the substrate in a constant-current mode is applied to substrates, which are pre-heated to 800 degrees C, to result in a negative bias voltage of greater than 350V throughout the nucleation and growth process. Self-masking by UNCD clusters, angle dependent sputtering of UNCD clusters, and ion-assisted chemical vapor deposition by bias enhanced bombardment of energetic ions are attributed to the formation of UNCD nano-pillars. High-resolution transmission electron microscopy analysis indicates that an interfacial layer exists between the silicon substrate and the UNCD nano-pillars. The porous UNCD film with high-density nano-pillars exhibits excellent optical anti-reflectivity and improved electron field emission characteristics compared to smooth and solid UNCD films. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769861]