Direct observation of in-plane ordering in the liquid at a liquid Al/α-Al2O3(<mml:math altimg="si1.gif" overflow="scroll" xmlns:xocs="http://www.elsevier.com/xml/xocs/dtd" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.elsevier.com/xml/ja/dtd" xmlns:ja="http://www.elsevier.com/xml/ja/dtd" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:tb="http://www.elsevier.com/xml/common/table/dtd" xmlns:sb="http://www.elsevier.com/xml/common/struct-bib/dtd" xmlns:ce="http://www.elsevier.com/xml/common/dtd" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:cals="http://www.elsevier.com/xml/common/cals/dtd"><mml:mrow><mml:mover accent="true"><mml:mrow><mml:mn>1</mml:mn></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover><mml:mspace width="0.25em"/><mml:mn>1</mml:mn><mml:mspace width="0.25em"/><mml:mn>0</mml:mn><mml:mspace width="0.25em"/><mml:mover accent="true"><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>¯</mml:mo></mml:mrow></mml:mover></mml:mrow></mml:math>) interface
Abstract Wetting behavior at the Al/α-Al2O3 liquid/solid interface is closely correlated with oxygen-induced structural changes at the interface. However, direct experimental evidence for the possible interfacial modifications has been rare. In the present study in situ high-resolution electron microscopy is successfully employed to characterize the structure of the interfaces between liquid Al and α-Al2O3 with [0 0 0 1] and [ 1 ¯ 1 0 2 ¯ ] surface normal directions at an elevated temperature. We provide evidence for ordering in the liquid (i.e. ordered oxygen-rich liquid interfacial layers) at both interfaces. The liquid at the Al/α-Al2O3(0 0 0 1) interface shows density perturbations in the direction perpendicular to the interface (layering) with a periodicity close to the interplanar distance of the (0 0 0 6) planes of α-Al2O3. On the other hand, the liquid at the Al/α-Al2O3( 1 ¯ 1 0 2 ¯ ) interface also reveals layering with an interlayer spacing of ∼0.25 nm and, additionally, with a degree of order occurring within the first few liquid layers (in-plane ordering), the ordered structure of which is similar to Al2O rather than α-Al2O3.