Activation Energies for Structural and Optical Changes in Sputtered ITO Thin Films for Applications on Polymers
(Room Room 104-C)
29 Apr 19
1:40 PM
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2:00 PM
A deeper understanding of the annealing mechanism for ITO films is needed for devices made at low temperatures, e.g., for polymer substrates, especially in achieving high optical clarity. While progress was made using flash lamp annealing for devices on thin glass substrates, such FLA has yet to show promise for polymers. At issue is how to increase the Eg and reduce the sub-bandgap absorption of ITO in its as-deposited amorphous state to crystalline’s preferred values. Such understanding lacks the activation energies Ea for this transition. To this end, oven annealing experiments (300, 400 and 500 °C, duration from 1-25 min) were made on soda lime glass substrates, where 250 nm ITO is encapsulated to prevent atmospheric interference, which were deposited at ambient temperatures by quasi-reactive pulsed dc magnetron sputtering (ceramic ITO target). Structural changes are measured by XRD and correlated with optical Tauc gap determined by [R,T] data from UV-Vis-NIR spectroscopy. This structural conversion correlates with increasing Eg, showing different rates of change depending on Ta. These change rates, plotted over inverse Ta, lead to the Arrhenius plot from which Ea is calculated and varies between 0.19 to 0.23 eV depending on the O2 flow rate and stating stoichiometric condition.