A simple, low-cost, and nontoxic aqueous ink chemistry is described for digital printing of ZnO films. Selective design through controlled precipitation, purification, and dissolution affords an aqueous Zn(OH)(x)(NH(3))(y)((2-x)+) solution that is stable in storage, yet promptly decomposes at temperatures below 150 degrees C to form wurtzite ZnO. Dense, high-quality, polycrystalline ZnO films are deposited by ink-jet printing and spin-coating, and film structure is elucidated via X-ray diffraction and electron microscopy. Semiconductor film functionality and quality are examined through integration in bottom-gate thin-film transistors. Enhancement-mode TFTs with ink-jet printed ZnO channels annealed at 300 degrees C are found to exhibit strong field effect and excellent current saturation in tandem with incremental mobilities from 4-6 cm(2) V(-1) s(-1). Spin-coated ZnO semiconductors processed at 150 degrees C are integrated with solution-deposited aluminum oxide phosphate dielectrics in functional transistors, demonstrating both high performance, i.e., mobilities up to 1.8 cm(2) V(-1) s(-1), and the potential for low-temperature solution processing of all-oxide electronics.

A ZnO transparent thin-film transistor (TTFT) with a channel layer formed via spin-coating deposition is demonstrated. The TTFT is highly transparent and exhibits n-channel, enhancement-mode behaviour with a channel mobility as large as 0.20 cm2 V−1 s−1 and a drain current on-to-off ratio of nearly 107.

Aluminum oxide phosphate thin films have been deposited via spin coating from aqueous solution and utilized as gate dielectrics in thin-film transistors. Films are atomically smooth, dense, and amorphous, while exhibiting excellent morphological stability to 1000 °C. Film chemistry and structure are investigated by using an array of analytical techniques including X-ray diffraction, FT-IR spectroscopy, and electronmicroprobe analysis. Dielectric film functionality and quality are explored through integration in capacitor and thin-film transistor devices. Film permittivity for an Al 2 PO 5.5 composition is found to be 4.8 in combination with leakage current densities <10 nA cm -2 at 1 MV cm -1 and current-limited breakdown fields up to 10 MV cm -1 . Thin-film transistors fabricated with these oxide phosphate dielectrics and sputtered ZnO channels exhibit strong field-effect and current saturation with incremental mobilities up to 3.5 cm 2 V -1 s -1 . The ability of the amorphous matrix to accommodate additional oxide components is demonstrated by the incorporation of La 2 O 3 and a resulting increase in film permittivity to 8.5, while maintaining breakdown fields >4 MV cm -1 .

New thin‐film dielectrics and nanolaminates have been synthesized via aqueous‐solution deposition of Hf and Zr sulfates, where facile gelation and vitrification of the precursor solution have been achieved without organic additives. X‐ray reflectivity, imaging, and metal‐insulator‐metal capacitor performance reveal that smooth, atomically dense films are readily produced by spin coating and modest thermal treatment (T < 325 °C). Dielectric characteristics include permittivities covering the range of 9–12 with breakdown fields up to 6 MV cm–1. Performance as gate dielectrics is demonstrated in field‐effect transistors exhibiting small gate‐leakage currents and qualitatively ideal device performance. The low‐temperature processing, uniformity, and pore‐free nature of the films have also allowed construction of unique, high‐resolution nanolaminates exhibiting individual layers as thin as 3 nm.

New, stable aqueous solutions have been developed for the deposition of high-quality HfO2 thin films. The low ionic strength of the solution relative to a stoichiometric salt provides the means to directly spin coat a film without organic additives. Peroxide mediates particle interaction in the solution, while enabling relatively low-energy pathways for condensation of the precursor species to a film. Film structure, chemistry, and density are investigated by X-ray diffraction, FT-IR, electron-probe microanalysis, SEM, and X-ray reflectivity. Results from these measurements collectively reveal that smooth and dense HfO2 films are readily produced from the precursors with annealing at moderate temperatures. Optical properties of the films are studied by spectroscopic ellipsometry and transmission/reflection measurements. The observed refractive indices (1.89−1.93) are comparable to those achieved via vapor deposition techniques. Dielectric properties are evaluated through integration of the films into capacitors and thin film transistors. Performance as capacitor dielectrics is characterized by leakage current densities <10 nA/cm2 (at 1 MV/cm) and breakdown fields up to 5.5 MV/cm. As gate dielectrics in thin film transistors with amorphous indium gallium zinc oxide channels, the films exhibit small gate leakage, enabling transistor performance with incremental mobilities near 13 cm2/V·s.

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Low-Energy Path to Dense HfO 2 Thin Films with Aqueous Precursor.-High-quality, smooth and dense HfO2 thin films are deposited by spin coating using an aqueous H2O2/HNO3 solution of the precipitate obtained from an aq. pH 8.5 solution of HfOCl2 and NH3 as a precursor. The films are characterized by XRD, FTIR, SEM, and X-ray reflectivity. Dielectric properties are evaluated through integration of the films into capacitors and thin film transistors. The performance as capacitor dielectrics is characterized by leakage current densities <10 nA/cm 2 (at 1 MV/cm) and breakdown fields up to 5.5 MV/cm. The optical and dielectric properties of the films substantively exceed those produced by any other solution technique and in most respects rival those produced via advanced vapor methods, enabling their use as a high-performance dielectric. -(JIANG, K.; ANDERSON, J. T.; HOSHINO, K.; LI, D.; WAGER, J. F.; KESZLER*, D. A.; Chem. Mater. 23 (2011) 4, 945-952, http://dx.doi.org/10.1021/cm102082j ; Dep. Chem., Oreg. State Univ., Corvallis, OR 97331, USA; Eng.) -W. Pewestorf 16-006