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

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 sp(2)-graphitic carbon. X-ray diffraction analysis of the pyrolyzed titanicone films displayed the signatures for anatase and rutile TiO2 after heating to 600 degrees C and then only ruble TiO2 after heating to 900 degrees 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 degrees C. The sheet resistance of the pyrolyzed titanicone films dropped dramatically versus pyrolysis temperature and reached a minimum sheet resistance of 2.2 x 10(4) Omega/square after heating to 800 degrees C. On the basis of the measured film thickness of 88 nm, the resistivity of the pyrolyzed titanicone film after heating to 800 degrees C was rho = 0.19 Omega cm. Segregation of other hybrid organic-inorganic films into sp(2)-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.