Experimental and theoretical evidence for hydrogen doping in polymer solution-processed indium gallium oxide

Wei Huang; Po-Hsiu Chien; Kyle McMillen; Sawankumar Patel; Joshua Tedesco; Li Zeng; Subhrangsu Mukherjee; Binghao Wang; Yao Chen; Gang Wang; Yang Wang; Yanshan Gao; Michael J Bedzyk; Dean M DeLongchamp; Yan-Yan Hu; Julia E Medvedeva; Tobin J Marks; Antonio Facchetti

doi:10.1073/pnas.2007897117

Experimental and theoretical evidence for hydrogen doping in polymer solution-processed indium gallium oxide

Proc Natl Acad Sci U S A. 2020 Aug 4;117(31):18231-18239. doi: 10.1073/pnas.2007897117. Epub 2020 Jul 23.

Authors

Wei Huang^{1

2}, Po-Hsiu Chien^{3

4}, Kyle McMillen⁵, Sawankumar Patel³, Joshua Tedesco⁶, Li Zeng^{7

8}, Subhrangsu Mukherjee⁹, Binghao Wang^{1

2}, Yao Chen^{1

2}, Gang Wang^{1

2}, Yang Wang^{1

2}, Yanshan Gao^{1

2}, Michael J Bedzyk^{10

8}, Dean M DeLongchamp¹¹, Yan-Yan Hu^{12

4}, Julia E Medvedeva¹³, Tobin J Marks^{14

2}, Antonio Facchetti^{14

2

15}

Affiliations

¹ Department of Chemistry, Northwestern University, Evanston, IL 60208.
² Materials Research Center, Northwestern University, Evanston, IL 60208.
³ Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306.
⁴ Center of Interdisciplinary Magnetic Resonance, National High Magnetic Field Laboratory, Tallahassee, FL 32310.
⁵ Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409.
⁶ Department of Materials Science and Engineering, Rutgers, The State University of New Jersey, Piscataway, NJ 08901.
⁷ Applied Physics Program, Northwestern University, Evanston, IL, 60208.
⁸ Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208.
⁹ Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899.
¹⁰ Applied Physics Program, Northwestern University, Evanston, IL, 60208; bedzyk@northwestern.edu dean.delongchamp@nist.gov yhu@fsu.edu juliaem@mst.edu t-marks@northwestern.edu a-facchetti@northwestern.edu.
¹¹ Materials Science and Engineering Division, National Institute of Standards and Technology, Gaithersburg, MD 20899; bedzyk@northwestern.edu dean.delongchamp@nist.gov yhu@fsu.edu juliaem@mst.edu t-marks@northwestern.edu a-facchetti@northwestern.edu.
¹² Department of Chemistry and Biochemistry, Florida State University, Tallahassee, FL 32306; bedzyk@northwestern.edu dean.delongchamp@nist.gov yhu@fsu.edu juliaem@mst.edu t-marks@northwestern.edu a-facchetti@northwestern.edu.
¹³ Department of Physics, Missouri University of Science and Technology, Rolla, MO 65409; bedzyk@northwestern.edu dean.delongchamp@nist.gov yhu@fsu.edu juliaem@mst.edu t-marks@northwestern.edu a-facchetti@northwestern.edu.
¹⁴ Department of Chemistry, Northwestern University, Evanston, IL 60208; bedzyk@northwestern.edu dean.delongchamp@nist.gov yhu@fsu.edu juliaem@mst.edu t-marks@northwestern.edu a-facchetti@northwestern.edu.
¹⁵ Flexterra Corporation, Skokie, IL 60077.

Abstract

The field-effect electron mobility of aqueous solution-processed indium gallium oxide (IGO) thin-film transistors (TFTs) is significantly enhanced by polyvinyl alcohol (PVA) addition to the precursor solution, a >70-fold increase to 7.9 cm²/Vs. To understand the origin of this remarkable phenomenon, microstructure, electronic structure, and charge transport of IGO:PVA film are investigated by a battery of experimental and theoretical techniques, including In K-edge and Ga K-edge extended X-ray absorption fine structure (EXAFS); resonant soft X-ray scattering (R-SoXS); ultraviolet photoelectron spectroscopy (UPS); Fourier transform-infrared (FT-IR) spectroscopy; time-of-flight secondary-ion mass spectrometry (ToF-SIMS); composition-/processing-dependent TFT properties; high-resolution solid-state ¹H, ⁷¹Ga, and ¹¹⁵In NMR spectroscopy; and discrete Fourier transform (DFT) analysis with ab initio molecular dynamics (MD) liquid-quench simulations. The ⁷¹Ga{¹H} rotational-echo double-resonance (REDOR) NMR and other data indicate that PVA achieves optimal H doping with a Ga···H distance of ∼3.4 Å and conversion from six- to four-coordinate Ga, which together suppress deep trap defect localization. This reduces metal-oxide polyhedral distortion, thereby increasing the electron mobility. Hydroxyl polymer doping thus offers a pathway for efficient H doping in green solvent-processed metal oxide films and the promise of high-performance, ultra-stable metal oxide semiconductor electronics with simple binary compositions.

Keywords: hydrogen doping; indium gallium oxide; oxide semiconductor; polymer incorporation; transistor.