(167f) Low-Cost Low-Temperature ALD of Titania Using Alkylamide Precursor and Oxygen with Urbach Tail Absorption in Visible Light Range for Potential Visible Light Adsorption | AIChE

(167f) Low-Cost Low-Temperature ALD of Titania Using Alkylamide Precursor and Oxygen with Urbach Tail Absorption in Visible Light Range for Potential Visible Light Adsorption

Authors 

Bhatia, H. - Presenter, University of Illinois at Chicagio
Takoudis, C. G., University of Illinois at Chicago
Alkylamide precursors have gained a lot of attention in the past years mainly due to their high vapor pressure allowing a more saturated pulse even at lower temperatures. One such precursor, TDMAT has been studied for low temperature ALD of Titania. Due to increased volatility and lower mass of the attached ligand, ALD at temperatures as low as room temperature has been reported using Ozone as an oxidizer which has become a norm for thin metal oxide films. However, due to its high cost of production, rapid thermal decomposition and effect on organic substances, Ozone might not be the most suitable oxidizer for organic substrates mainly elastomers with C-C π bonding in an ALD reaction due to the extended time of exposure of the substrate to ozone. In this study, oxygen is used to replace ozone exploring a low-cost reaction to synthesize thin conformal films of Titania at temperatures of 120 °C, a temperature suitable for most organic substrates. With the use of a pulsed gas setup, a saturated dose of pure oxygen from an oxygen cylinder was pulsed into the reactor. With the use of oxygen, the growth rate was seen to be higher in comparison with conventional oxidizers such as water and ozone as analyzed using SE. Further characterization using XPS revealed low carbon content and highly stoichiometric films hinting towards pure Titania growth. With this method, low temperature ALD can be implemented on many organic substrates that are sensitive to Ozone and cuts out the cost for an ozone generator. One of the most interesting phenomena observed using SE was the appearance of a very small but non-zero extinction coefficient in the visible range. This extinction coefficient was similar to Urbach tail absorption usually observed in the UV range. This also points towards slight absorption of Visible light by the deposited Titania films which opens new avenues for research in photocatalytic activity of Titania films within visible light spectrum.