Solution processible Inorganic Nanocrystal based Thin-film Transistor Hongki Kang EE235 April 27 2009
Dec 19, 2015
Solution processible Inorganic Nanocrystal based
Thin-film Transistor Hongki Kang
EE235 April 27 2009
Flexible & Printed Electronics
- Printable (=solution processible) semiconductor material
- Organic semiconductor- Unstable (H2O, O2 etc)- Low performance (≈ amorphous Si, mobility 1cm2/Vs)
Process 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 method
Solution A: Hg(ClO4)2 + 1-thioglycerol in DI water with NaOH in N2
Gas B: H2Te gas (generated Al2Te3 + H2SO4 under N2)
Under stirring, Gas B was passed through Solution A
The precipitate containing thioglycerol-capped HgTe particles was separated by centrifugation.
- Single-crystalline - Transparent- sintering temperature ↑ => conductivity↑ optimized condition: @150 °C for 15 min
Process Flow (1) - Nanocrystal Synthesis
Process Flow (2) - Device Fabrication
65°
• 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 DG
HgSe Nanocrystals
• A HgSe nanocrystal-based flexible TFT
Result
NC HgTe HgSeType P-type N-type
Sintered NC grain size (nm) 13 15
Mobility (cm2/Vs) 4.1 4.0
ION/IOFF ratio 103 102
Sintering temp (°C) 150
Flexibility negligible characteristic variation under the 0.2% of tensile or compressive strain
Mobility: better than organic semiconductor, a-SiThermal budget: compatible with plastic substrateStability: Air stable
ION/IOFF ratio: low
Conclusion
Inorganic Nanoparticl
e
High performanc
e
Chemical stability
Plastic substrate
compatibility
Flexible & Printed Electronics
OptimizationPrintabilityMore material researchMaterial Compatibility