In Situ Radiation Hardness Study of Amorphous Zn-In-Sn-O Thin-Film Transistors with Structural Plasticity and Defect Tolerance

초록

Solution-processed metal-oxide thin-film transistors(TFTs) withdifferent metal compositions are investigated for ex situ and in situradiation hardness experiments against ionizing radiation exposure.The synergetic combination of structural plasticity of Zn, defecttolerance of Sn, and high electron mobility of In identifies amorphouszinc-indium-tin oxide (Zn-In-Sn-Oor ZITO) as an optimal radiation-resistant channel layer of TFTs.The ZITO with an elemental blending ratio of 4:1:1 for Zn/In/Sn exhibitssuperior ex situ radiation resistance compared to In-Ga-Zn-O,Ga-Sn-O, Ga-In-Sn-O, and Ga-Sn-Zn-O.Based on the in situ irradiation results, where a negative thresholdvoltage shifts and a mobility increase as well as both off currentand leakage current increase are observed, three factors are proposedfor the degradation mechanisms: (i) increase of channel conductivity,(ii) interface-trapped and dielectric-trapped charge buildup, and(iii) trap-assisted tunneling in the dielectric. Finally, in situradiation-hard oxide-based TFTs are demonstrated by employing a radiation-resistantZITO channel, a thin dielectric (50 nm SiO2), and a passivationlayer (PCBM for ambient exposure), which exhibit excellent stabilitywith an electron mobility of & SIM;10 cm(2)/V s and a & UDelta;V (th) of <3 V under real-time (15 kGy/h) gamma-rayirradiation in an ambient atmosphere.

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