Rigidity Percolation in Plasma Enhanced Chemical Vapor Deposited a-SiC:H Thin Films

Plasma Enhanced Chemically Vapor Deposited SiC:H thin films are compelling materials for both semiconductor nano-electronic and MEMS/NEMS technologies due to the extreme chemical inertness of this material and the ability to tune a variety of material properties across an extreme range of values. As one example of the latter, we demonstrate that using PECVD the dielectric constant and Young's modulus of SiC: H thin films can be varied from < 3 to > 7 and < 10 GPa to > 200 GPa respectively. Utilizing Fourier Infrared-Transform Spectroscopy, we show that this remarkable range in materials properties is achieved primarily via the incorporation of terminal hydrogen groups which lowers the overall connectivity of the Si-C network bonding. We find that once the average network coordination number for Si and C falls below 2.6, the SiC network becomes under constrained and there is a loss of rigidity percolating through the system thus limiting the range of materials properties that can be achieved in this system.