Solid state magnetic resonance investigation of the thermally-induced structural evolution of silicon oxide-doped hydrogenated amorphous carbon. (August 2016)

• Record Type: Journal Article
• Authors: Peng, Jing; Sergiienko, Anastasiia; Mangolini, Filippo; Stallworth, Phillip E.; Greenbaum, Steve; Carpick, Robert W.
• Is Part Of: Carbon. Volume 105(2016)
• Page Start: 163
• Page End: 175
• Publication Date: 2016-08
• Subjects: Carbon -- Periodicals; Carbone -- Périodiques; Koolstof; Toepassingen; Electronic journals; 546.681
• DOI: 10.1016/j.carbon.2016.04.021
• Languages: English
• ISSNs: 0008-6223

Abstract

Abstract: Due to their increased stability in extreme environments, relative to amorphous hydrogenated carbons (a-C:H), amorphous thin film silicon oxide-doped hydrogenated amorphous carbons (a-C:H:Si:O) are being commercially developed as solid lubricants and protective coatings. Although various properties of a-C:H:Si:O have been investigated, no definitive structure of a-C:H:Si:O has ever been proposed, nor has its thermally-induced structural evolution been thoroughly studied. The aim of this work is to better understand the structure of a-C:H:Si:O through solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) spectroscopies. Deeper insights into the thermally-driven structural evolution are obtained by annealing a-C:H:Si:O between 50 °C and 300 °C under anaerobic conditions and taking NMR/EPR measurements after each step. EPR results show that the number of paramagnetic defects decreases by 70% with annealing at 300 °C. 1 H NMR shows the hydrogen concentration decreases with annealing temperature from 2 × 10 22 g −1, and then levels off at approximately 0.7 × 10 22 g −1 for anneals between 200 °C and 300 °C. The carbon–silicon–oxygen network exhibits some structural reorganization, seen directly as a slight increase in the sp 2 / sp 3 ratio in the 13 C NMR with annealing. These results combined with relaxation data are interpreted according to a two-component structure largely defined by differences in hydrogen and defect contents.