Chemically sensitive imaging of (YBa2Cu3O7)m/(PrBa2Cu3O7)n superlattices by means of high-resolution electron microscopy

Zone-axis and off-zone-axis illumination were used to observe the compositional modulation of (YBa2Cu3O7)m/(PrBa2Cu3O7)n superlattices by means of high-resolution transmission electron microscopy. In both cases a chemically sensitive image contrast allowing a distinction between Y and Pr occupancy was obtained. The optimum parameters for imaging the compositional difference between YBa2Cu3O7 and PrBa2Cu3O7 were evaluated by means of detailed image simulations. Good agreement between experimental images of (YBa2Cu3O7)m/(PrBa2Cu3O7)n superlattices obtain ed with these parameters and the corresponding simulated images was found. Both zone-axis and off-zone-axis imaging are compared and discussed with respect to their ability to yield the strongest possible chemical signal over the widest possible specimen area