Change of diamond film structure and morphology with N2 addition in MW PECVD apparatus with linear antenna delivery system

Abstract

Deposition of nano-crystalline diamond (NCD) over large areas is of high interest for industrial applications. For instance NCD is an excellent substrate for cell growth but it is also interesting for photonic applications associated with nitrogen-vacancy (NV) centres. There have been many studies on the effect of nitrogen addition on the growth of diamond using conventional resonance cavity microwave plasmas (both H and Ar based) but none using MW PECVD apparatus with linear antenna delivery system (MW-LAPECVD). In this work, we show that an ultra nano-crystalline diamond (UNCD) type of morphology can be prepared upon N2 addition to H2-CO2-CH4plasmas at low pressures (0.3 mbar) and low temperature (520 °C); however, these films despite their UNCD character show sp3 dominated Raman spectra and highly isolating behavior. The crystalline structure and morphology of the films were characterized by scanning electron microscopy, atomic force microscopy, Raman spectroscopy, grazing angle X-ray diffraction, and transmission electron microscopy. Diamond films' composition was evaluated from thermal neutron depth profiling. Films were also characterized by photoluminescence spectroscopy to study the incorporation of luminescent NV centre. Addition of nitrogen increases deposition rate and dramatically changes surface morphology and crystalline structure from well faceted diamond crystals to UNCD like morphology.