ИСТИНА

In the present study the porous anodic alumina films obtained on single crystal substrates with different crystallographic orientations were quantitative characterized by SAXS technique. The diffraction experiments were performed at the beamline BM26B “DUBBLE” of ESRF. The AAO porous film, grown on Al(111) substrate exhibits a spot-like diffraction pattern that corresponds to the long-range orientational order. In case of substrate with (100) orientation several rings with uniform distribution of intensity indicate that porous domains are completely disoriented in the plane of the oxide film. In order to observe the influence of the crystallographic orientation on the longitudinal pore arrangement, a specially designed Al(100) single crystal with the vicinal edges tilted from the (100) plane by 5° was used. It was shown, that the grown direction of AAO channels is tailored by two competing factors: (i) electromigration of ions under external electric field, which push it along the normal to the Al surface; (ii) presence of stable crystal faces of (100) family, crossing of which by the pore is energetically unfavourable due to hampered diffusion of oxygen ions through dense atomic planes. Aforementioned factors lead to coexisting of two preferable pore grown directions in AAO with disorientation of about 0.3°.