Electrically conductive diamond-like carbon coatings containing metal grains (Me-DLC) have recently been suggested for use in sensors. We found that the electrical resistance of molybdenum-containing DLC (Mo-DLC) varies with increasing cycles of cyclic bending. Because of this aging property, Mo-DLC has potential as a fatigue sensor. In this paper, we analyzed the variation of nanoscopic structure of Mo-DLC by various spectroscopic techniques and clarified the mechanism underpinning the variation of the electrical properties of Mo-DLC in terms of the hopping conduction in Me-DLC. In the Raman spectra, the intensity ratio between the D-band and G-band of Mo-DLC gradually decreased with bending, which means that the sp2 carbon in aromatic rings decreases in number. XPS indicates that carbide bonding (C–Mo) increased after bending for 107 cycles. Furthermore, EELS showed a decrease in π* bonding in the a-C:H matrix with increasing cyclic bending. From these results, we assume a mechanism that the bonding condition of carbon in the matrix changes from sp2 to carbide because the repeated bending stress changed the electrical properties of Mo-DLC. This knowledge can be useful for controlling the electrical and mechanical properties of Mo-DLC for sensing application. Furthermore, the characteristics of Mo-DLC, such as the variation in electrical properties, can be applied to sense fatigue in severe environments.
- Diamond-like carbon
- Electrical properties characterization
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Mechanical Engineering
- Materials Chemistry
- Electrical and Electronic Engineering