Elastic properties of a-C:N:H films

Dual dc-rf plasma system has been used to deposit hydrogenated carbon nitride (CNx:H) films that exhibit high elastic recovery (75%). Transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectra and Raman spectra were subsequently used to study the microstructure and bonding of the resultant films. The structure of the films from TEM is seen to consist of many particles embedded in an amorphous carbon matrix, and the films can be described as graphitelike or onionlike with interplanar distances of ≈1.15, 1.95, and 3.5Å, as obtained from selected area electron diffraction (SAED). FTIR shows that nitrogen promotes the formation of sp2 CC∕CN aromatic rings in the films. Raman spectra shows two apparent peaks at about 700 and 1200cm−1 in addition to the G and D peaks. Only by adding two extra peaks at approximately 1230 and 1470cm−1 can we deconvolute the Raman spectra of CNx:H in the region of 1000–2000cm−1. Combining TEM and SAED, we attribute the three peaks at about 700, 1200, and 1470cm−1 to fullerene or onion structure. However, the elastic recovery is relatively lower than elastic hydrogenated free carbon nitride films. We think that this is due to the fact that hydrogen is mainly incorporated to sp3 carbon and suppresses cross-linking three-dimensional (3D) network growth.