Fullerene-like CNx and CPx Thin Films; Synthesis, Modeling, and Applications

This Thesis concerns the development of fullerene-like (FL) carbon nitride (CNx) thin films and the discovery of phosphorus-carbide (CPx) compounds. The work dedicated to CPx include first-principles theoretical simulations of the growth and properties of FL–CPx structures. I have employed DC magnetron sputtering methods to synthesize both CNx and CPx thin films. The deposition conditions for CPx films were chosen on the basis of the theoretical results as well as from the experience from the deposition of FL–CNx thin films. The characterization of the CPx films is divided into three main directions: structural characterization by transmission electron microscopy and scanning electron microscopy, analysis of the amount of elements and chemical bonds present in the structure by X-ray photoelectron spectroscopy and Auger spectroscopy, and mechanical property analysis by nanoindentation. The CPx films exhibit a short range ordered structure with FL characteristics for substrate temperature of 300 °C and for a phosphorus content of 10–15 at.%, which is consistent with the theoretical findings. These films also displayed the best mechanical properties in terms of hardness and resiliency, which are better than those of the corresponding FL–CNx films. For the FL–CNx thin film material, I find that the surface water adsorption is lower compared to commercial computer hard disk top coatings. Following that line the dangling bonds in FL–CNx coatings have been investigated by electron spin resonance (ESR). The absence of ESR signal for FL–CNx indicates very low density of dangling bonds in the material, which explains the low water adsorption tendency. The potential for using highly elastic FL–CNx coatings in an automotive valvetrain environment has also been investigated. CNx coatings of different nitrogen content were investigated using microscopy, wear testing, nanoindentation testing, and in an experimental cam-tappet testing rig. The FL–CNx coating with the higher value of hardness/elastic modulus showed greater durability in cam-tappet wear testing. Thin Film Physics Division Department of Physics, Chemistry and Biology (IFM) Linköpings universitet, SE-581 83 Linköping, Sweden