Rapid vapor-phase fabrication of organic-inorganic hybrid superlattices with monolayer precision

We report a new layer-by-layer growth method of self-assembled organic multilayer thin films based on gas-phase reactions. In the present molecular layer deposition (MLD) process, alkylsiloxane self-assembled multilayers (SAMs) were grown under vacuum by repeated sequential adsorptions of C=C-terminated alkylsilane and titanium hydroxide. The MLD method is a self- limiting layer-by-layer growth process, and is perfectly compatible with the atomic layer deposition (ALD) method. The SAMs films prepared exhibited good thermal and mechanical stability, and various unique electrical properties. The MLD method, combined with ALD, was applied to the preparation of organic-inorganic hybrid nanolaminate films in the ALD chamber. The organic-inorganic hybrid superlattices were then used as active mediums for two-terminal electrical bistable devices. The advantages of the MLD method with ALD include accurate control of film thickness, large-scale uniformity, highly conformal layering, sharp interfaces, and a vast library of possible materials. The MLD method with ALD is an ideal fabrication technique for various organic-inorganic hybrid superlattices.     

Enhanced surface evolution induced by the molecular desorption in dodecanethiol self-assembled monolayer on Au(1 1 1)

The evolution of the surface structure in dodecanethiol self-assembled monolayer on Au(1 1 1) substrate has been studied with ultra high vacuum scanning tunneling microscopy at several temperatures. The structure of substrate Au(1 1 1) surface changed suddenly at a temperature of 110 °C. The enhanced mobility of the substrate gold atoms at this temperature is attributed to the desorption of the dodecanethiol molecules.     

Synthesis and characterization of monomeric, oligomeric, and polymeric aluminum 8-hydroxyquinolines

We report the synthesis and characterization of monomeric, oligomeric, and polymeric aluminum 8-hydroxyquinolines. The new structures of aluminum quinolate are contrived for expanding the application of AlQ(3) in the area of solution process by modifying AlQ(3) structure for improving solution processibility and crystallization resistance. Oligomeric aluminum 8-hydroxyquinoline (OALQ) was obtained using methylaluminoxane (MAO) and 8-hydroxyquinoline (8-HQ). Polymeric aluminum 8-hydroxyquinoline (PALQ) consists of 8-HQ and a polymeric Al-O backbone, simply prepared by stoichiometrically reacting 8-hydroxyquinoline, pentaerythritol propoxylate, and triethyl aluminum in the presence of chloroform. The absorption and emission spectra of OALQ and PALQ bear a clear resemblance to those of AlQ(3), and the molecular orbitals of OALQ and PALQ are virtually identical to those of AlQ(3). In the SEM images of AlQ(3) and OALQ, cylindrical rods of >100 microm in length and 5-10 microm in diameter for AlQ(3) and 20-100 microm in length and 1-5 microm in diameter for OALQ were observed, respectively. The size of the cylindrical rods of OALQ decreased compared with that of AlQ(3). As for the image of PALQ, an amorphous phase with bulge spots (ca. 5 microm) was observed. These microscope data correspond well to the X-ray powder pattern results. The chemical shifts (31.1, 57.0 ppm) and peak broadness of (27)Al NMR of AlQ(3) and its DFT calculation results present that mer- and fac-AlQ(3) appear in equilibrium through pentacoordinated intermediates. With the combination of DFT optimization and NMR calculation, models of OALQ and PALQ, hexa-, penta-, and tetracoordinated structures, were proposed, which exist in polymeric Al-O backbone and with inter- and intracoordination of Al-O bonds.     

Electrochemically active, anti-biofouling polymer adlayers on indium-tin-oxide electrodes

Here we report the synthesis of a novel electrochemically active polymer, preparation of adlayers of the polymer on optically transparent electrodes, and an application of the adlayers to immobilization of engineered cells through a direct covalent coupling reaction.     

Impact of amorphous titanium oxide film on the device stability of Al/TiO2/Al resistive memory

We have investigated the role of amorphous titanium oxide film in the reliable bipolar resistive switching of Al/TiO₂/Al resistive random access memory devices. As TiO₂ deposition temperature decreased, a more stable endurance characteristic was obtained. We proposed that the degradation of the bipolar resistive switching property of Al/TiO₂/Al devices is closely related to the imperfect migration of oxygen ions between the top insulating interface layer and the oxygen-deficient titanium oxide during the set and reset operations. In addition, the dependence of the TiO₂ film thickness on the switching property was also studied. As the thickness of the film increased, a reduction in the resistance of the high resistance state rapidly appeared. We attribute the improved endurance performance of thin and low-temperature grown TiO₂ devices to the amorphous state with a low film density.     

Ambient pressure syntheses of size-controlled corundum-type In2O3 nanocubes

Hydrolysis of In(O-iPr)3 by 10 molar excess of water at 90 degrees C in a surfactant/solvent mixture of oleylamine/oleic acid/trioctylamine provides very small nanoparticles (<5 nm in diameter) of In(O)(OH). Subsequent in situ thermolysis of the formed In(O)(OH) nanoparticles at 350 degrees C and ambient pressure produces monodisperse h-In2O3 nanocubes, which can form an extended two-dimensional array on a flat surface. The size of the In2O3 nanocubes (8, 10, and 12 nm) could be easily controlled by the simple change in the amounts of employed surfactants. The h-In2O3 nanocube samples show blue PL emissions at room temperature due to, presumably, systematic oxygen vacancy.