Characterization of Thermally Cured and Laser Cured Sol-gel ITO Thin Films
Date Issued
2009
Date
2009
Author(s)
Huang, Chang-Pin
Abstract
ITO thin films were deposited on Corning Eagle 2000 glass substrates using anhydrous indium trichloride dissolved in acetylacetone, followed by a refluxing process at 70 ºC for 3 hours and then mixed with tin chloride dissolved in ethanol. By modifying the thermal processes such as prolong preheating duration, introducing post-annealing in reduced atmosphere or ultraviolet illumination, ITO thin films with a minimum resistivity of 7.88×10-3Ω-cm and the corresponding maximum concentration of 6.836×1020 cm-3 by single spin coating were obtained. The average transmittance of thermally cured ITO thin films in the visible light range was above 88%. This study also demonstrated the feasibility of an ultra low temperature (260 oC) ITO sol-gel process by 355 nm solid-state UV lasers. With the 9.09 at.% Sn dopant precursor solution, the optimized process was to preheat the triple dip-coated films at 260 oC for 5 hours, followed by laser irradiation with the fluence of 900 mJ/cm2. The minimum resistivity was 5.37×10-2Ω-cm with activated carrier concentrations of 6×1019 cm-3. The optical transmittances were comparable to those of sol-gel derived ITO thin films by thermal curing (average ~78 %; cf. the thermally cured film 79 %). An extraordinarily high tin element compositions, decreased from 34.3 to 19.4 at.% as laser fluences increased from 700 mJ/cm2 to 1000 mJ/cm2, were presented in the laser cured ITO thin films. In 500 oC thermally cured ITO thin films, only 7.1 at.% tin ratio was detected. Excess Sn ions would form complex defects by Sn (Ⅳ) and Sn (Ⅱ) which were unfavorable to electrical conduction. The calculated density of neutral scattering centers Nn ranged between 1.679×1021 cm-3 and 5.925×1021 cm-3 was nearly one order of magnitude lager than 5.748×1020 cm-3 with thermally cured ones.
Subjects
sol-gel
laser curing
neutral scattering centers
post-annealing
Type
thesis
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