Comparative study of water and carbon dioxide adsorption on CuFeO$_{\mathrm{2}}$ and CuFe$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$O$_{\mathrm{2\thinspace }}$highly epitaxial thin films*

Thermal programmed desorption (TPD) of CO$_{\mathrm{2}}$ and H$_{\mathrm{2}}$O from a 200 nm thick CuFeO$_{\mathrm{2}}$ and 52 nm thick CuFe$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$O$_{\mathrm{2\thinspace }}$delafossite surfaces was performed in a Ultra-high vacuum (UHV) chamber. The thin films with epitaxial quality were grown by Pulsed Laser Deposition (PLD) on Al$_{\mathrm{2}}$O$_{\mathrm{3}}$ (0001) substrates . The adsorption / desorption of CO2 and H2O process was also monitored with X-ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Our results revealed that carbon dioxide is preferentially chemisorbed by CuFe$_{\mathrm{1-x}}$Ga$_{\mathrm{x}}$O$_{\mathrm{2}}$ over water and we observed the opposite behavior with regard to chemisorption of CO$_{\mathrm{2}}$ and H$_{\mathrm{2}}$O over CuFeO$_{\mathrm{2}}$. Hydroxyls and metal carbonates were formed on the surface due to the chemisorption of H$_{\mathrm{2}}$O and CO$_{\mathrm{2}}$. Arrhenius plots for CO$_{\mathrm{2}}$ and H$_{\mathrm{2}}$O desorption were done and activation energy for desorption were obtained.