A. Mozalev

Evolution of Surface Morphology, Crystallite Size, and Texture of WO3 Layers Sputtered onto Si-Supported Nanoporous Alumina Templates

Thin Al films sputtered on n-silicon wafers were anodized in two potentiodynamic steps in 0.4 M tartaric acid at 210 V and 0.4 M malonic acid at 95 V to prepare nanoporous alumina templates of type A and B, respectively. Processes at the Al/n-Si interface were closely examined to avoid field-assisted alumina dissolution during anodizing. WO 3 semiconductor layers were radiofrequency magnetron sputtered onto the as-anodized and pore-widened templates. It was revealed that the sputtered WO 3 layers covered the entire surface of type A templates while only partly penetrating into the widened pores of type B templates. The WO 3 layers crystallized at 350°C, with monoclinic phase of P2 1 /n symmetry and an average crystallite size of 28.0 nm (type A) and 32.5 nm (type B). Amorphous alumina in the Al 2 O 1 /n-Si systems did not crystallize up to 1200°C. The common trend for the WO 3 /Al 2 O 3 /n-Si systems was a preferential growth of WO 3 nanocrystallites in the direction, the texture increasing with further pore widening. Besides, the crystal texture in the WO 3 layer was systematically higher on type B templates. The link between the structural features and the gas-sensing ability of the WO 3 /Al 2 O 3 /n-Si systems has been discussed.

Porous alumina-based cathode for organic light-emitting devices

We propose a new cathode for organic light-emitting devices based on anodic porous alumina films. For this purpose usual and modified porous alumina and structured aluminum with removed porous alumina layer can be used. The usage of porous alumina cathode results in more inhomogeneous electric field and, as a consequence, more intensive auto electron emission and cathode efficiency. Owing to extended surface this matrix also gives the possibility to reach higher luminophor concentration without noticeable luminescence quenching. Organic electroluminescent devices of this type are easily produced and can be more efficient and stable as compared with usual layered structures. An intensive secondary electron emission is observed after irradiating of activated alumina matrix by an electron beam. We developed one of the proposed porous alumina cathode based organic electroluminescence structure doped with amorphous naphthalimide derivative. A bright electroluminescence of naphthalimide in such a structure was observed for the first time. The ways of the further development of this structure are pointed out.

Luminescent properties of organic compounds in nanodimensional aluminium oxide structures

Dielectric anodic oxide alumina films have a nanoscale 2D structure consisting of cylindrical pores placed perpendicularly to the surface. Such films with a regular structure where pores distance is equal to pore diameter and can be changed from 5 nm to 400 nm are created. The spectral and luminescent properties of different organic compounds luminescing in a wide spectral region included into the pores were studied. The photonic pseudo band gap have been established for both transmission and reflection spectra.

WO 3 nanorods on Si by anodising A1/W/Ti laers

In this paper we show a method based on electrochemistry to obtain tungsten oxide nanorods on the surface of a silicon substrate. The technique implies the anodisation of an aluminium/ tungsten bilayer and the selective etching of porous alumina. The resulting nanostructured metal oxide films show a very high surface to volume ratio, which is of interest in a wide range of applications including gas and bio sensors or as special coatings in medical applications.

A H 2 microsensor based on nanocolumnar tungsten oxide grown by template-assisted anodization

Sensors embedded in micro fuel cells can help in controlling some important parameters such as temperature, humidity or gas concentration. In this paper we introduce the fabrication procedure for MEMs-compatible nanocolumnar tungsten oxide gas microsensors and show the results of measuring their responses to H2, CO and humidity. Tungsten oxide nanoculumns were grown by smart anodization of Al/W layers on silicon micro-hotplate substrates. An excellent linear sensor response was observed for hydrogen in the 0–20 ppm concentration range and a low response to CO and moisture in the usual operating conditions of micro fuel cells. The sensors operated at moderate temperature due to the high surface-to-volume ratio and the nanostructured morphology of the sensing films.

P-31: New Organic Electroluminescence Structures Using Porous Alumina Films

Porous alumina based organic electroluminescence structure doped with naphthalimide deriative is developed. The usage of porous alumina cathode results in more inhomogeneous electric field and, as a consequence, more intensive autoelectron emission. Organic electroluminescent devices of this type are easily produced and can be more efficient and stable as compared with usual structures.