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Structural and chemical analysis of annealed plasma-enhanced atomic layer deposition aluminum nitride films Broas, Mikael; Sippola, Perttu; Sajavaara, Timo; Vuorinen, Vesa; Perros, Alexander Pyymaki; Lipsanen, Harri; Paulasto-Kröckel, Mervi Broas, M., Sippola, P., Sajavaara, T., Vuorinen, V., Perros, A. P., Lipsanen, H., & Paulasto-Kröckel, M. (2016). Structural and chemical analysis of annealed plasmaenhanced atomic layer deposition aluminum nitride films.

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Dense arrays of zinc oxide nanorods with high specific surface areas were grown by hydrothermal method and functionalized by self-assembled monolayer (SAM) of porphyrins. The growth process was optimized to obtain dense arrays of nanorods with diameter of 60–80 nm and length up to 1.5 μm. The increase in the effective surface area was monitored by comparing the absorbances of SAM deposited both on the flat and nanorod surfaces of ZnO. To alter further semiconductor-organic SAM interactions, a 2 or 5 nm thick layer of either Al2O3 or TiO2 was deposited on the ZnO nanorods. The present results show that both carboxylic acid and triethoxysilane anchors can be used to form porphyrin SAMs on the studied metal oxide substrates, and the electronic interactions between the metal oxide and porphyrin SAM are strongly modified by a thin layer of Al2O3 or TiO2. These hybrid semiconductor-organic SAM constructions present promising model systems for advanced spectroscopy studies of semiconductor-organic interfaces with high degree of control over electronic interactions and system morphology.

A radial pattern with continuous topography gradient is presented, which induces a continuous inward wettability gradient and enables self-propelling and accurate positioning of droplets to the pattern center. The effect of droplet size and wettability gradient of the pattern on the self-mobility of droplets is investigated. The wettability gradient is found to increase towards the pattern center, enhancing the self-motion of droplets at the inner area of the pattern. Moreover, larger droplets give rise to a larger solid-liquid contact diameter, which helps to satisfy the self-motion criteria that the advancing contact angle at front edge is smaller than the receding contact angle at rear edge. Consequently, a larger droplet size favors self-motion initiated from the outer area of the pattern. The continuous topography gradient employed here allows the flexible dispensing of droplets at any place within a certain range, and avoids potential pinning defects to droplets at geometrical discontinuities.An average self-motion velocity up to 4.0 cm/s for microliter-sized droplets is achieved on the resultant patterned surface.