Thermal decomposition and structural variation by heating on hydrogenated amorphous carbon films

• Published in: Diamond and related materials 2020-01, Vol.101, p.107609, Article 107609
• Main Authors: Akasaka, Hiroki, Tunmee, Sarayut, Rittihong, Ukit, Tomidokoro, Masashi, Euaruksakul, Chanan, Norizuki, Souta, Supruangnet, Ratchadaporn, Nakajima, Hideki, Hirata, Yuki, Ohtake, Naoto
• Format: Article
• Language: English
• Subjects: Carbon; Decomposition; Fine structure; Heat resistance; Heating; Hydrogen storage; Hydrogenated amorphous carbon film; Hydrogenation; Near edge X-ray absorption fine structure; Photoelectric emission; Spectrum analysis; Thermal decomposition; Thermal desorption spectroscopy; Thermal resistance; Uniformity of carbon bonding; X ray absorption; X-ray photoemission electron microscopy
• ISSN: 0925-9635; 1879-0062
• DOI: 10.1016/j.diamond.2019.107609

Hydrogenated amorphous carbon (a-C:H) films are only empirically known to be decomposed by heating, and this heat resistance is expected to be dependent on the structure of the film. To understand the decomposition processes and their uniformity, the thermal decomposition characteristics of two types of a-C:H film were investigated after the structural determination of the sp2/(sp2 + sp3) ratios and hydrogen contents. The mass of the gas released by thermal decomposition of the a-C:H films was detected by evaluation of the thermal desorption spectroscopy to determine the starting temperature the film with high hydrogen content started to desorb hydrogens at 400 °C and hydrocarbons at 750 °C. The film with low hydrogens started to desorb decomposition gases at 750 °C. Moreover, uniform decomposition of the films was observed using synchrotron-based X-ray photoemission electron microscopy (X-PEEM) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The thermal decomposition of a-C:H films with uniform film structure proceeds relatively uniformly, and the mechanism of thermal decomposition of the films depends on the source materials of the films. The thermal decomposition proceeds uniformly at the micron scale when the initial structure is uniform. [Display omitted] •Thermal decomposition on the hydrogenated amorphous carbon films was investigated.•The mass of gas released by thermal decomposition of the films was detected by TDS.•Starting temperature of thermal decomposition depends on the film structure.•Decomposition uniformity of sp2/sp3 carbon ratio was observed using X-PEEM and NEXAFS.•The thermal decomposition of a-C:H films with a uniform structure proceeds relatively uniformly.