Fabrication and Characterization of Metal Oxycarbide Thin Films

Abstract

Ceramic materials in the Al-O-C and Hf-O-C systems were fabricated for electrical or thermal protection applications. AlOxCy films were produced via high-vacuum chemical vapor deposition (CVD) using dimethylaluminum isopropoxide as the precursor. The deposition process was investigated from nucleation to bulk film growth stages. In the reaction-limited regime, the activation energy of the deposition process was 113 or 74 kJ/mol depending on the deposition temperature range. Electron spectroscopy techniques were used to characterize chemical compositions and elemental bonding environments within deposited films. Carbon content within films increased with increased deposition temperature. Aluminum-carbon bonding was observed in films deposited at temperatures of 538 °C and higher. Studies showed that films containing Al-C bonds exhibited dielectric constants approximately one order of magnitude smaller than a film without Al-C bonds.

Cyclopentadienyl (Cp) hafnium compounds were investigated as precursors to HfOxCy films. Bis(Cp)n-butyl hafnium and bis(methyl-Cp)dimethyl hafnium were dismissed as CVD precursors due to thermal instability and cost of synthesis, respectively. Films were produced from bis(Cp)dimethyl hafnium and bis(methyl-Cp)dimethyl hafnium through liquid phase casting methods and annealed under high vacuum. Analysis of chemical bonding in the films revealed oxidation of hafnium atoms even though precursor compounds did not contain oxygen atoms. Oxygen in the films was attributed to atmospheric exposure.