CBED determinations of step-heights on etched and annealed MgO (100) surfaces

The annealing in air of acid-etched (100)-oriented MgO substrates at 1350°C for 10 mins or more, has been shown to promote the formation of relatively large and well-defined surface steps. YBCO, in particular, has been shown to exhibit grapho-epitaxy, in which steps on the surface promote the nucleation of islands and influence the subsequent growth into an interconnected film. The formation of this interconnected film may be influenced by the height of the steps on the substrate, whilst the height of the steps also may play a role in the island nucleation event itself. Therefore, a study of the step heights in the acid-etched and annealed substrates employed is important. Presented is the application of CBED technique for the measurement of step heights.