Synthesis of biocompatible surfaces by nanotechnology methods

SYNTHESIS OF BIOCOMPATIBLE SURFACES BY NANOTECHNOLOGY METHODS 705Min:−1664Max:1308dN(E)Ti−C202 214 226 238 250 262Energy, eV274 286Fig. 12. AES spectrum of the acid-etched surface of titanium in the region of poor wetting (where the contact angle varied within5°–90°).was 0.039 nm per cycle. We have prepared sampleswith film thicknesses of 8, 24, and 48 nm, which wereobtained using n = 200, 600, and 1200 reaction cycles,respectively.In addition to high precision in maintaining presetfilm thicknesses, the ALD method also ensures uniqueresults with respect to the uniform (conformal) coatingof large developed surfaces (including those ofcomplicated shapes), which is achieved by virtue of thefact that the reaction proceeds every time in a singlelayer chemisorbed on the substrate surface. We haveexperimentally checked for this on test structuresobtained by the ion-beam processing of a silicon platein which trapezoid-profiled grooves with a base widthof ~2 μm and a depth of ~4 μm were formed and subsequentlycoated by titanium dioxide using the ALDmethod. As can be seen from Fig. 13, the TiO 2 layerthickness is virtually the same over the entire surfacewith a complicated relief.Characterization of TiO 2 Films Obtainedby the ALD Method on TitaniumThe TiO 2 layers on titanium substrates were studiedby Fourier transform IR spectroscopy (FTIR)(Perkin-Elmer Spectrum 100 spectrometer) and X-ray diffraction (XRD) (Rigaku Ultima IY universaldiffractometer), which showed that both the thicknessand structure of TiO 2 layers depend on thenumber of reaction cycles. Figure 14 shows theFTIR spectra measured in the reflection modebefore (curve 1) and after (curves 2–4) TiO 2 depositionby the ALD method. As can be seen, the spectraof both the titanium substrate (curve 1) and TiO 2layer deposited for 200 cycles (curve 2) display abroad absorption band at 700–1000 cm –1 , whichcorresponds to amorphous titanium dioxide [9]. Anincrease in the number of cycles to n > 600 leads tothe appearance of a sharp peak at 870 cm –1 , whichcorresponds to a crystalline TiO 2 with an anatasestructure (curves 3 and 4). According to the FTIRdata, similar changes from the amorphous to polycrystallineanatase structure were observed for thefilms grown by the ALD on silicon substrates.The appearance of a polycrystalline anatase structurein the layer grown by ALD with increasing numberof reaction cycles was also confirmed by the XRDdata (Fig. 15).LayerTiO 2Bottomlayer2 μmFig. 13. SEM image of the surface of silicon with a trapezoidalgroove formed using ion-beam processing followedby TiO 2 deposition by the ALD method.NANOTECHNOLOGIES IN RUSSIA Vol. 5 Nos. 9–10 2010