Study of carbon thin films deposited by dc and high power impulse magnetron sputtering

Amorphous carbon (a-C) thin films known for their hardness, can be tuned by varying the sp3/sp2 hybridization ratio. Generally direct current magnetron sputtering (dcMS) is a commonly used method to prepare good quality of a-C thin films. But dcMS plasma is mostly consist of neutral particles. An ionized plasma process e.g. high-power impulse magnetron sputtering (HiPIMS) is expected to grow even better-quality films due to increased adatom mobility. Therefore, in this work, we deposited carbon thin films using HiPIMS and compared them to dcMS for similar deposition conditions. We found from atomic force microscopy (AFM) measurements that the average particle size is about 1.3 times larger in HiPIMS deposited films than that of dcMS. However, from x-ray reflectivity (XRR) measurements, we found that the imaginary part of refractive index (Im( r)) was about an order of magnitude larger in HiPIMS deposited C films. It appears that high plasma density and high adatom mobility in the HiPIMS process creates defects which are manifested in terms of enhanced C-O and C=O bonding in Carbon k-edge x-ray absorption spectroscopy (XAS) measurements. (author)