In-situ thermal stability analysis of amorphous Si-doped carbon films

Abstract

Doping enhances diamond like carbon (DLC) coatings for extreme high-temperature applications. However, understanding the enhancement mechanism is elusive. This study employs a novel system integrating Raman spectroscopy and depth-sensing indentation with a heating chamber to monitor chemical structural, and mechanical properties of doped and un-doped hydrogenated DLC films, with temperature. This in-situ investigation represents extreme working conditions, revealing how doping enhances DLC films thermal stability. It is shown that the thermal stability of the a-C:H:Si films could be maximized by increasing the Si content. The film with the highest Si content was stable until 650 ̊C while the films with lower Si or No–Si content graphitized at lower temperatures. This study presents hardness measurement under high-temperature conditions that were not available before. In-situ observations reveal how Si doping correlates with stability of mechanical properties at elevated temperatures. The correlation of the mechanical properties with WG reveals that the mechanism of thermal stability is that Si doping makes the film resistant to graphitization by promoting sp3 hybridization. Furthermore, our in-situ approach makes it possible to conduct characterization that emulates real service conditions, and therefore, our results show great potential of the industrial application of DLC coatings in extreme thermal conditions.