Slide 1Flexible ElectronicsPrinted ElectronicsFlexible & Printed ElectronicsInorganic SemiconductorNano particle SinteringNano particle SinteringHgTe/HgSe inorganic nanoparticle based TFTsProcess Flow (1) - Nanocrystal SynthesisSlide 10Process Flow (2) - Device FabricationDevice CharacteristicResultConclusionConclusionSolution processible Inorganic Nanocrystal based Thin-film Transistor Hongki KangEE235 April 27 2009Flexible ElectronicsPolymer Vision: ReadiusPrinted ElectronicsFlexible & Printed Electronics- Printable (=solution processible) semiconductor material- Organic semiconductor- Unstable (H2O, O2 etc)- Low performance (≈ amorphous Si, mobility 1cm2/Vs)Inorganic SemiconductorNano particle Sinteringlarge surface-to-volume ratioNano particle SinteringHgTe/HgSe inorganicnanoparticle based TFTsProcess Flow (1) - Nanocrystal Synthesis HgTe, HgSe-High mobility (µHgTe,p: 320cm2/Vs, µHgSe,n: 15,000cm2/Vs @300K)-Low melting point (Tm,HgTe: 670°C, Tm,HgSe: 799°C)NC synthesis (diameter ~5nm)-synthesized in an aqueous solution by a colloidal methodSolution A: Hg(ClO4)2 + 1-thioglycerol in DI water with NaOH in N2Gas B: H2Te gas (generated Al2Te3 + H2SO4 under N2)Under stirring, Gas B was passed through Solution AThe precipitate containing thioglycerol-capped HgTe particles was separated by centrifugation.- Single-crystalline - Transparent- sintering temperature ↑ => conductivity↑ optimized condition: @150 °C for 15 minProcess Flow (1) - Nanocrystal SynthesisProcess Flow (2) - Device Fabrication65° • Prohibiting the water vapor from penetrating the bare poly-ether-sulfone (PES)• Minimizing the damage of the PVP layers occurring during photo-resist development and lift-off processes • Cross-linked poly-4-vinylphenol (C-PVP) buffer layer on PES substrate (spin coating) • Patterning(photolithography) • HgTE/HgSe nanocrystal channel layer(spin coating) • Lift-off process • Changing the layers into hydrophilic easily and rapidly(a) Before UV/ozone treatment • Gold gate electrode(thermal evaporator) • Al2O3 insulator (atomic layer deposition) • UV/ozone treatment(b) After UV/ozone treatment • Sintering process at 150 oC for 15 minutes • Source/drain electrodes • HgSe nanocrystal-basedthin film transistor (TFT)S DGHgSe Nanocrystals • A HgSe nanocrystal-based flexible TFTDevice Characteristic<HgTe> <HgSe>ResultNC HgTe HgSeType P-type N-typeSintered NC grain size (nm)13 15Mobility (cm2/Vs) 4.1 4.0ION/IOFF ratio 103102Sintering temp (°C)150Flexibilitynegligible characteristic variation under the 0.2% of tensile or compressive strainMobility: better than organic semiconductor, a-SiThermal budget: compatible with plastic substrateStability: Air stableION/IOFF ratio: lowConclusionFlexible & Printed ElectronicsOptimizationPrintabilityMore material researchMaterial
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