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Experiment. Previous expreiment. “Molar ratio of spin-coated precursors must be matched precisely” Zinc acetate (2 acetic group) : Tin tert-butoxide (4 butoxyl group) = 2 : 1. Ratio < 2:1. Zinc precursor. Zinc tin oxide + Tin tert -butoxide. Tin precursor. Substrate. Substrate.
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Experiment Previous expreiment “Molar ratio of spin-coated precursors must be matched precisely” Zinc acetate (2 acetic group) : Tin tert-butoxide (4 butoxyl group) = 2 : 1 Ratio < 2:1 Zinc precursor Zinc tin oxide + Tin tert-butoxide Tin precursor Substrate Substrate Negative Vth, high off-current
Experiment Reduction of Sn precursor thickness 0.1M Tin butoxide 0.05M Tin butoxide 0.025M Tin butoxide 4000RPM 10-12A off current 6000RPM
Experiment Reduction of Zn precursor thickness ZnOAc 6000RPM ZnOAc 2000RPM Vth negative shift : Increased Sn/Zn+Sn ratio
Experiment Air annealing – effective than annealing in dry glovebox drybox 6hrs annealing Air 3hrs Glovebox: No oxygen, solvent vapor, etc.
Experiment Wet annealing – not very effective wet 3hrs Dry 2hrs + Wet 4hrs Designed process was non-hydrolytic – hydrolysis has to be avoided
Experiment Increasing Zn precursor thickness (0.3M zinc acetate solution) Leakage current (not p-type conductivity) Poor TFT characteristics – Acetate:Tert-butoxide >> 2:1 (Unbalanced)
Experiment Optimum Zn:Sn ratio ~ 1 : 1 In previous experiment, optimum ration was, Zinc acetate (2 acetic group) : Tin tert-butoxide (4 butoxyl group) = 2 : 1 Too obtain optimum Zn:Sn ratio, New precursor stack design Zinc acetate + Tin acetate (3:1) Tin tert-butoxide Substrate # of Acetic group : # of butoxyl group = 1:1 (For complete reaction) Zn:Sn = 1:1 (For electrical characteristic)
Experiment Zn acetate + Sn acetate solution 8:1 4:1 2:1 By poor solubility of Sn acetate
Experiment 300°C, 2hr 300°C, 2.5hr 300°C, 1hr
250°C, 1hr 270°C, 1hr 300°C, 1hr 330°C, 1hr