Ambient-processable high capacitance hafnia-organic self-assembled nanodielectrics

Ken Everaerts, Jonathan D. Emery, Deep Jariwala, Hunter J. Karmel, Vinod K. Sangwan, Pradyumna L. Prabhumirashi, Michael L. Geier, Julian J. McMorrow, Michael J. Bedzyk, Antonio Facchetti, Mark C. Hersam, Tobin J. Marks

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48 Citations (Scopus)

Abstract

Ambient and solution-processable, low-leakage, high capacitance gate dielectrics are of great interest for advances in low-cost, flexible, thin-film transistor circuitry. Here we report a new hafnium oxide-organic self-assembled nanodielectric (Hf-SAND) material consisting of regular, alternating π-electron layers of 4-[[4-[bis(2-hydroxyethyl)amino]phenyl]diazenyl]-1-[4- (diethoxyphosphoryl) benzyl]pyridinium bromide) (PAE) and HfO2 nanolayers. These Hf-SAND multilayers are grown from solution in ambient with processing temperatures ≤150 C and are characterized by AFM, XPS, X-ray reflectivity (2.3 nm repeat spacing), X-ray fluorescence, cross-sectional TEM, and capacitance measurements. The latter yield the largest capacitance to date (1.1 μF/cm2) for a solid-state solution-processed hybrid inorganic-organic gate dielectric, with effective oxide thickness values as low as 3.1 nm and have gate leakage <10-7 A/cm2 at ±2 MV/cm using photolithographically patterned contacts (0.04 mm 2). The sizable Hf-SAND capacitances are attributed to relatively large PAE coverages on the HfO2 layers, confirmed by X-ray reflectivity and X-ray fluorescence. Random network semiconductor-enriched single-walled carbon nanotube transistors were used to test Hf-SAND utility in electronics and afforded record on-state transconductances (5.5 mS) at large on:off current ratios (ION:IOFF) of ∼105 with steep 150 mV/dec subthreshold swings and intrinsic field-effect mobilities up to 137 cm2/(V s). Large-area devices (>0.2 mm2) on Hf-SAND (6.5 nm thick) achieve mA on currents at ultralow gate voltages (<1 V) with low gate leakage (<2 nA), highlighting the defect-free and conformal nature of this nanodielectric. High-temperature annealing in ambient (400 C) has limited impact on Hf-SAND leakage densities (<10-6 A/cm 2 at ±2 V) and enhances Hf-SAND multilayer capacitance densities to nearly 1 μF/cm2, demonstrating excellent compatibility with device postprocessing methodologies. These results represent a significant advance in hybrid organic-inorganic dielectric materials and suggest synthetic routes to even higher capacitance materials useful for unconventional electronics.

Original languageEnglish
Pages (from-to)8926-8939
Number of pages14
JournalJournal of the American Chemical Society
Volume135
Issue number24
DOIs
Publication statusPublished - Jun 19 2013

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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    Everaerts, K., Emery, J. D., Jariwala, D., Karmel, H. J., Sangwan, V. K., Prabhumirashi, P. L., Geier, M. L., McMorrow, J. J., Bedzyk, M. J., Facchetti, A., Hersam, M. C., & Marks, T. J. (2013). Ambient-processable high capacitance hafnia-organic self-assembled nanodielectrics. Journal of the American Chemical Society, 135(24), 8926-8939. https://doi.org/10.1021/ja4019429