Pyrolysis of Titanicone Molecular Layer Deposition Films as Precursors for Conducting TiO2/Carbon Composite Films

• Published in: Journal of physical chemistry. C 2013-08, Vol.117 (34), p.17442-17450
• Main Authors: Abdulagatov, Aziz I., Terauds, Kalvis E., Travis, Jonathan J., Cavanagh, Andrew S., Raj, Rishi, George, Steven M.
• Format: Article
• Language: English
• Subjects: Applied sciences; Condensed matter: structure, mechanical and thermal properties; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Physics; Solubility, segregation, and mixing; phase separation; Structure and morphology; thickness; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Thin film structure and morphology
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp4051947

Titanium alkoxide films known as “titanicones” were grown using molecular layer deposition (MLD) techniques using the sequential exposure of TiCl4 and glycerol. These titanicone MLD films were then pyrolyzed under argon to yield conducting TiO2/carbon composite films. The Raman spectra of the pyrolyzed titanicone films revealed the characteristic “D” and “G” peaks associated with sp2-graphitic carbon. X-ray diffraction analysis of the pyrolyzed titanicone films displayed the signatures for anatase and rutile TiO2 after heating to 600 °C and then only rutile TiO2 after heating to 900 °C. X-ray photoelectron depth profiling of the pyrolyzed titanicone films showed that the carbon was distributed throughout the film and began to segregate to the surface after heating to 900 °C. The sheet resistance of the pyrolyzed titanicone films dropped dramatically versus pyrolysis temperature and reached a minimum sheet resistance of 2.2 × 104 Ω/□ after heating to 800 °C. On the basis of the measured film thickness of 88 nm, the resistivity of the pyrolyzed titanicone film after heating to 800 °C was ρ = 0.19 Ω cm. Segregation of other hybrid organic–inorganic films into sp2-graphitic carbon and metal oxide domains after pyrolysis under argon was also observed for alucone films and various metalcone films based on Zn, Zr, Hf, and Mn. The conducting TiO2/carbon composite films and other metal oxide/carbon composite films could have important electrochemical applications as electrodes for Li ion batteries or pseudocapacitance supercapacitors.