MORPHOLOGY OF NANOSTRUCTURED SnO 2 FILMS PREPARED WITH POLYMERS EMPLOYMENT

The gas sensitivity applied problems solutions needs a consideration and detailed investigation of the material’s electronic and ionic subsystems’ behavior. These systems’ behavior at their own turn are tightly connected with the structure and morphology of surfaces. The morphology investigations results are given for the SnO 2 layers obtained with the polymers usage. The nanoscaled materials have physical properties principally differing from the corresponding ones of microscaled objects, and are widely used in electronic, optical and magnetic devices such as gas, optical sensors, photodiodes, sun cells, monoelectron transistors and memory units. [1]. The nanomaterials’ specific peculiarity is their great active surface which defines the crucial time and temperature decrease for the chemical reactions proceeding [2]. The mentioned property is widely used for the constructing of the new gas sensors’ generation with perfect speed of responce and low energy consumption. In connection with the said it is reasonable to elaborate the nanograins materials, with controlled development surface for the gas analysis. The technique using polymers as the components assisting in structuring is proposed for the aims of obtaining of well developed surface layers having the nanoscaled grains. The nanocrystallized tin dioxide having the electroconductivity highly sensible to the state of the surface in the (300—800) K temperature region specific for the oxidizing-recollecting reactions has the most practical use in the gas analysis[3]. It is one of not many materials, which may be obtained in highly dispersed state (crystallite sizes 5—20 nm). The tin dioxide surface has perfect adsorptive properties and reaction ability which are defined by the surface and bulk oxygen vacancies and active chemisorbed oxygen [3] and are tightly connected with the surface morphology. These ideas predefined the SnO 2 surface morphology investigation. The transparent thin nanostructured Tin dioxide films were prepared using polymer materials in the sol-gel method. The production technique had several stages: preparation of the Tin containing organic fillers, preparation of polymer material sol in the solution and, finally, insertion the tin containing compounds into it. Further, the gel obtained was deposited on the substrate and finally annealed in the muffle stove. The annealing time and temperature were chosen with the consideration of the polymer’s decomposition time. After the polymer‘s decay products full removal during the annealing and the following it oxidation, the thin Tin dioxide layers with developed nanostuctured surface were formed. The films obtained had different degrees of transparency (from milk-white to fully transparent) and different adhesive properties. Having obtained these results, it is clear that the preparation of such films needs both different solvents (water, acetone), polymer materials (polyvinyl spirits, cellulose, poly-methyl-metacrylat and others) and Tin containing fillers. The films based on the polyvinyl spirits gel had weak coherence with substrates and were of milk-white color. This witnesses about presence in the film of not only Tin dioxide, but and other reaction’s products. Films based on the cellulose had the dark brown color, which is specific for the bivalent tin oxide — SnO. The darkening of the films may be caused by the extremely great carbon contain, which stays in the film after the cellulose was burn away. The films based on polyvinyl-acetate (PVA) with the addition of acetylacetonate of tin appeared to be fully transparent with tight adhesion with the substrate. The initial sol was prepared as following. PVA was cleaned by 25% ammonia (NH 4 OH) solution, was washed three times in a distilled water, then was dried by the CaCl 2 dryer, then was polymerized by means of 1% benzoil peroxide solution and finally was grinded. Then the PVA obtained was inserted into the dissolver (acetone) at the room temperature. In a case of polymer’s insolubility in the solvent, the monomer of the same substance may be used. The gel-type structure was formed after 20—60 minutes of thorough mixing. The solution of acetylacetonate of tin powder in acetone was inserted into the gel obtained. After special preparations of the glass substrate it was covered by the mono layer of the film. Then it was kept for 5 minutes in the open air for the acetone may