Direct observation of thickness and foreign interlayer driven abrupt structural transformation in ultrathin carbon and hybrid silicon nitride/carbon films

Despite its predominant role in controlling the functional properties, a longstanding concern in the research of ultrathin amorphous carbon and its hybrid materials is the inadequate understanding of their structural properties, especially on ceramic substrates. This constitutes a barrier for many technological developments. Here we comprehensively examine the structural properties of ultrathin carbon and hybrid silicon nitride/carbon (SiNx/C) films on a ceramic substrate. We observe large Raman G peak shifting, colossal enhancement (small but visible increase) in the sp3 carbon bonding of filtered cathodic vacuum arc-processed (sputter-processed) carbon films with increasing film thickness from 0.5 to 20 nm. We construct a novel three-phase model to explain the results which are also supported by core-level photoemission spectroscopy. We notice a huge change in sp3 growth dynamics for 1-7 nm thick films which is found to be significantly larger for filtered cathodic vacuum arc-processed (∼7%/nm) than sputter-processed (∼1.1%/nm) carbon films, based on Raman spectroscopy. We also observe strong SiNx layer(s)-driven shifting of the Raman G peak, reduction of the ID/IG ratio and tuning of the sp3 bonding in SiNx/C bilayer and multilayer films. These results are very important for fundamental science and ultrathin carbon-based technologies.

Graphical abstractA thickness driven tuning of sp3 bonding was observed in ultrathin carbon films. The huge change in sp3 growth dynamics for 1-7 nm thick films was noticed which calculated to be significantly larger for filtered cathodic vacuum arc (FCVA)-processed (∼7%/nm) than sputter-processed (∼1.1%/nm) carbon films, based on Raman spectroscopy.Download high-res image (124KB)Download full-size image