Inorganic Phosphors and ACTFEL Devices on Flexible Plastic Substrates J. P. Bender and J. F. Wager Department of Electrical Engineering and Computer Science S. Park, B. L. Clark, and D. A. Keszler Department of Chemistry Oregon State University Corvallis, Oregon USA

Organization 1.Hydrothermal annealing overview 2.Hydrothermally annealed Zn 2 GeO 4 3.Zn 2 GeO 4 :Mn on flexible plastic substrates 4.Conclusions

Hydrothermal Annealing Modification of conventional hydrothermal dehydration technique Refractory oxide films crystallized using this technique include MnO 2, ZrO 2, Zn 2 SiO 4, and Zn 2 GeO 4 Substrate is sealed in a Teflon-lined reaction vessel with water and heated Material is repeatedly dissolved and redeposited, causing crystalline grain growth

Hydrothermal Annealing of rf Sputtered Zn 2 GeO 4 :Mn Zn 2 GeO 4 :Mn ACTFEL devices with L 40 > Hz and CIE x,y = 0.300,0.667 have been demonstrated Hydrothermal annealing is possible due to small solubility of Zn 2 GeO 4 in water

Hydrothermally Annealed Zn 2 GeO 4 :Mn Annealed film roughness can be controlled from R q ~ 10 nm to ~ film thickness by adjusting anneal temperature, time, and amount of water added

Hydrothermally Annealed Zn 2 GeO 4 :Mn PL emission observed: – 125 °C for hydrothermal anneal – 625 °C for furnace anneal Approximately equal PL intensity: – 200 °C, 2 hrs for hydrothermal anneal – 680 °C, 2 hrs for furnace anneal

Zn 2 GeO 4 :Mn films on Plastic Substrates Three plastics successfully employed: –polypropylene –Kapton polyimide –Appear 3000 Substrate requirements: –withstand 150 °C –withstand UV & O radicals –withstand exposure to H 2 O –retain dimensions and flexibility

Kapton Polyimide T g > 360 °C Chemically very stable Relatively low CTE Deep amber or black color Dupont Kapton 500HPP-ST preferred for better thin-film adhesion

Bright PL from Inorganic Phosphor on Flexible Substrate Hydrothermally annealed Zn 2 GeO 4 :Mn film shows bright green photoluminescence Polyimide film may be bent moderately without cracking or delamination of film

Inverted ACTFEL Device Polyimide film (5 mils) Ti adhesion/contact (100 nm) Zn 2 GeO 4 :Mn (500 nm) SiO 2 (300 nm) ITO (320 nm)

Appear 3000 Clear plastic film from Promerus designed for display applications Less attractive than polyimide films in many respects, but: 92% transparent

Normal ACTFEL Device Appear 3000 film (5 mils) Ti adhesion (10 nm) Zn 2 GeO 4 :Mn (500 nm) SiO 2 (300 nm) Al (320 nm) ITO (160 nm) Ti adhesion (10 nm)

Conclusions Thin-films of crystalline refractory oxides have been deposited on flexible plastic substrates Operational ACTFEL devices have been fabricated on flexible plastic, exhibiting dim EL Further work is needed to improve performance: –Better low temperature dielectric –Improved performance from hydrothermally annealed Zn 2 GeO 4 :Mn –Investigation of hydrothermal annealing for other oxide phosphors

Acknowledgements This work was supported by the National Science Foundation under Contract Nos. DMR and DMR Kellie Schmitt of DuPont, Joe McDaniel of Promerus, and Ivo Thys of AFGA provided plastic film samples for evaluation.

Young’s modulus (GPa) CTE (ppm/ °C) Tg (°C) Kapton 500HPP-ST polyimide 2.8(20) Promerus Appear Polypropylene0.9 – (~90) Materials Properties