Ambient-Processable High Capacitance Hafnia-Organic Self-Assembled Nanodielectrics

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• 作者：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
• 刊名：The Journal of the American Chemical Society
• 出版年：2013
• 出版时间：June 19, 2013
• 年：2013
• 卷：135
• 期：24
• 页码：8926-8939
• 全文大小：735K
• 年卷期：v.135,no.24(June 19, 2013)
• ISSN：1520-5126

文摘

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 蟺-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 鈮?50 掳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 渭F/cm²) for a solid-state solution-processed hybrid inorganic鈥搊rganic gate dielectric, with effective oxide thickness values as low as 3.1 nm and have gate leakage <10^鈥? A/cm² at 卤2 MV/cm using photolithographically patterned contacts (0.04 mm²). 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 (I_ON:I_OFF) 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 掳C) has limited impact on Hf-SAND leakage densities (<10^鈥? A/cm² at 卤2 V) and enhances Hf-SAND multilayer capacitance densities to nearly 1 渭F/cm², demonstrating excellent compatibility with device postprocessing methodologies. These results represent a significant advance in hybrid organic鈥搃norganic dielectric materials and suggest synthetic routes to even higher capacitance materials useful for unconventional electronics.