The electric field strength calculations inside porous alumina barrier layer during electrochemical anodizing in aqueous solutions of oxalic acid at a forming voltage of 90 to 250 V have been performed. The configuration of porous alumina cells with a porosity from 1 to 10 % have been used as the input data for calculations. It is found that the value of electric field strength inside porous alumina reaches 1010-1011 V/m. New phenomena and effects, appeared during alumina anodizing process with high forming voltages, have been analyzed.

Experimental data and a model are presented, and the electric field that appears in porous alumina during electrochemical anodic oxidation of aluminum in electrolytes based on an aqueous solution of oxalic acid at a voltage of 90–250 V is calculated. It is found that the electric field in the layers with a porosity of 1–10% in growing alumina reaches 109–1010 V/m, which exceeds the electric strength of the material and causes microplasma patterns emitting visible light at the pore bottom, the self-organization of the structure of porous alumina, and the anisotropy of local porous anodizing. Moreover, other new effects are to be expected during aluminum anodizing under the conditions that ensure a high electric field inside the barrier layer of porous oxide.

Physics, Chemistry and Applications of Nanostructures, pp. 124-127 (2015) No AccessELECTRONIC AND ATOMIC STRUCTURE OF SILICON NANOCRYSTALS IN ALUMINUM MATRIX AND WITHOUT ITV. A. TEREKHOV, D. S. USOLTSEVA, S. Yu. TURISHCHEV, I. E. ZANIN, B. L. AGAPOV, A. A. LESHOK and P. S. KATSUBAV. A. TEREKHOVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, D. S. USOLTSEVAVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, S. Yu. TURISHCHEVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, I. E. ZANINVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, B. L. AGAPOVVoronezh State University, Universitetskaya 1, 394006 Voronezh, Russia, A. A. LESHOKBelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarus and P. S. KATSUBABelarusian State University of Informatics and Radioelectronics, P. Browka 6, 220013 Minsk, Belarushttps://doi.org/10.1142/9789814696524_0032Cited by:0 PreviousNext AboutSectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack CitationsRecommend to Library ShareShare onFacebookTwitterLinked InRedditEmail Abstract: Al–Si nanocomposites have been produced by magnetron sputtering of a compound target onto a silicon substrate. Nanostructured silicon films have further been obtained by selective removal of aluminum. It has been found that silicon particles are nanocrystals with the mean size of 20-25 nm, which surface is covered by an amorphous layer with a thickness of ~5 nm. The band structure (in particular, near the bottom of the valence band) of the nanocomposite films was found to differ from the bulk material because of an influence of the aluminum matrix. After the aluminum removal, the valence band structure becomes identical to that in the bulk material. FiguresReferencesRelatedDetails Physics, Chemistry and Applications of NanostructuresMetrics History PDF download

The design and fabrication technology of integrated optical and electrical interconnects on silicon are developed. The light-emitting diodes in the presented construction are based on nanostructured silicon built in an alumina matrix. The optocouple with the current transforming coefficient of about 1 % is fabricated. The advantages of the developed design are shown in comparison with existing analogues.

Films of Al-Si nanocomposites produced by magnetron evaporation of a complex target onto a silicon substrate have been investigated using scanning electron microscopy, X-ray diffraction, ultrasoft X-ray emission spectroscopy, and X-ray absorption near edge structure spectroscopy. It has been found that silicon inclusions are nanocrystals with the mean size of 20–25 nm, with the surface covered by an amorphous silicon layer. The presence of the aluminum matrix in the initial films changes their band structures, in particular, near the bottom of the valence band. After the removal of aluminum, the structure of the valence band becomes identical to that in the bulk material and the structure of the conduction band indicates the presence of a disordered surface layer with a thickness of ∼5 nm.

Nanostructured silicon films were fabricated by magnetron sputtering of an Al+Si composite target with a subsequent selective etching off the aluminum phase from the deposited film. It is shown that the film structure consists of silicon submicron conglomerates of 60-160 nm, which in turn are composed of nanoscale grains arranged as a "bunch of grapes". The regularities of the nanostructured silicon film formation are discussed.

Heat-segregation calculations inside porous alumina barrier layer have been performed. It is shown that Joule heat on pore bottom surface is four orders of magnitude greater than in other porous oxide areas. This effect leads to local heating of this areas and microplasma formations during anodizing process. The recommendations about the heat dissipation efficiency increasing in order to improve the uniformity of the structures have been advised.

Electric resistance of an aluminum foil was used to monitor its temperature during anodization in the regimes providing porous alumina formation. Current densities higher than 100 mA/cm2 were found to be accompanied by the sample heating several tens of degrees above the electrolyte temperature. Local heating of different regions in the forming porous nanostructured alumina was calculated to show considerable anisotropy of the effect.

The design and technology of manufacturing of optical interconnections on the basis of nanostructured silicon have been developed. The optoelectronic couple with conversion coefficient of current of about 1% has been produced. The possibility of integration of optical and electron interconnections on the silicon chip is demonstrated.

The technology of nanostructured silicon built-in an anodic alumina films has been developed. The films thickness was varied from 20 to 140 nm. Structural properties and photovoltage phenomena are investigated in these films. Fast and slow components have been observed in photovoltage transients assigned to intra- and interparticle transport of excess photogenerated carriers, respectively. The linear dependence of the photovoltage amplitude on the film thickness gives an evidence that silicon nanoparticles form an interconnected network inside the dielectric matrix. Applications of nanostructured silicon built-in anodic alumina films are discussed.

An electroluminescent structure based on nanostructured porous silicon embedded in a layer of anodic alumina has been suggested and fabricated. The heat conductivity of the alumina matrix markedly exceeds that of the silicon-containing insulators. The effective heat removal makes it possible to attain an 0.5% quantum efficiency of electroluminescence, which is comparable with the best parameters of silicon-based light-emitting devices. The physical phenomena responsible for the emission of light by the structure under study are considered.

Anodization of Al-W alloys with a W concentration in the range of 1-40 at. % has been performed to fabricate a composite nanoporous oxide. An increase of the W content is found to enlarge few times the size of pores. Composite oxide films with the weight ratio WO3/Al2O3 > 50 % have been formed for the first time. Applications of nanostructured aluminium-tungsten oxide composite films are discussed.