I am trying to deposit ITO on glass using E-Beam evaporator and anneal it in Nitrogen using RTA. The E-beam evaporator works on a vacuum of 1e-7 Torr. After deposition, the colour of the film was dark brown. After annealing the sample, it went transparent. also the resistivity was reduced, but still relatively high (1000 ohm/sqr) for a transparent electrode.
I have gone through the literature, and most of the recipes use some partial oxygen pressure in deposition. I can't do that in vacuum E-Beam, so I tried to anneal it in dry air, and resistivity have actually been reduced to (500ohm/sqr).
Can any one help me explaining this in a physical way? Oxygen deficiency (deviation from stoichiometry) is needed for conductive ITO. Why do we use partial oxygen pressure in deposition?
is there a working recipe for depositing ITO using vacuum E-Beam evaporation?
Hi Mutasem
Usually, concentration of oxygen in the ITO lattice has key influence on its properties (e.g. conductivity). Highly possible that during EB deposition significant amount of oxygen is lost due to very high vacuum. Formed oxygen vacancies may strongly change conductivity, and may be reason for darkening as well. It is suggested to add oxygen radicals to the e-Beam deposition process to control its concentration.
Please refer to J.S. Kim, et al. “Effects of oxygen radical on the properties of indium tin oxide thin films deposited at room temperature by oxygen ion beam assisted evaporation” Thin Solid Films 377-378 (2000) 103-108.
From the experimental conditions mentioned whether any Dopant was tried or not is not clear.
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