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

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

60 Scopus citations

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 (US)
Pages (from-to)8926-8939
Number of pages14
JournalJournal of the American Chemical Society
Volume135
Issue number24
DOIs
StatePublished - Jun 19 2013

ASJC Scopus subject areas

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

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