Pyrolysis of Alucone Molecular Layer Deposition Films Studied Using In Situ Transmission Fourier Transform Infrared Spectroscopy

The pyrolysis of alucone molecular layer deposition (MLD) films was studied in vacuum using in situ transmission Fourier transform infrared spectroscopy. The initial alucone MLD films were grown using trimethylaluminum (TMA) and either ethylene glycol (EG) (HO-(CH2)(2)-OH) or hydroquinone (HQ) (HO-C6H4-OH) at 150 degrees C. The alucone MELD films were then pyrolyzed in vacuum at temperatures ranging from 400 to 750 degrees C. The absorbance features for the C-H, C-C, and C-O stretching vibrations were observed to be lost at pyrolysis temperatures from 350 to 500 degrees C. For the alucone films grown using TMA and EG, the loss of these absorbance features was coupled to an increase in carboxylate (R-COO-) absorbance features. The carboxylate absorbance features reached their peak at a pyrolysis temperature of 450 degrees C and then decreased slowly with higher pyrolysis temperatures. The carboxylate absorbance features are consistent with an Al2O3/carbon composite material with Al3+/COO- species at the interface. In addition, the presence of carbon in the Al2O3/carbon composite led to an increase in the background infrared absorbance for the pyrolyzed alucone films grown using HQ containing six carbons. This background infrared absorbance is linked to electrical conductance in a network of carbon domains in the pyrolyzed alucone films, as described by Drude-Zener theory. In contrast, the alucone films grown using EG containing two carbons did not display an increase in the background infrared absorbance. This absence of background infrared absorbance is consistent with less carbon in the Al2O3/carbon composite grown using EG. The pyrolysis of the alucone films on ZrO2, particles led to very conformal Al2O3/carbon composite films, as observed by transmission electron microscopy images.