Functional Ultrathin Films and Nanolaminates from Aqueous Solutions

Nanolaminates composed of TiO 2 and Al 4 O 3 (PO 4 ) 2 (AlPO) thin films have been fabricated from aqueous solution precursors. By adjusting precursor concentrations individual layers can be controlled to a thickness near 1 nm. Characterization by X-ray reflectivity and transmission electron microscopy (TEM) reveals near-atomically smooth interfaces and a high degree of regularity in the film stacks. X-ray diffraction is utilized to investigate the crystallization behavior of TiO 2 layers under one-dimensional confinement of the glassy AlPO layers. TiO 2 –AlPO nanolaminates incorporated into capacitor structures exhibit low leakage current densities (<10 nA/cm 2 at 1 MV/cm) and high breakdown fields up to 5.4 MV/cm with annealing temperatures as low as 350 °C. Tailorable dielectric constants have also been demonstrated by varying the relative thickness of the TiO 2 and AlPO films. As gate dielectrics in thin-film transistors with solution-processed amorphous indium gallium zinc oxide channels, the nanolaminates exhibit small gate leakage, enabling ideal transistor performance with incremental mobilities near 3 cm 2 /V·s.