Scanning tunneling microscopy of the a-b planes of Bi2(Ca,Sr)3Cu2O8+δ single crystal and thin film

Publisher Website
Google Scholar
Abstract
A scanning tunneling microscope was used to image the a‐b plane of a single crystal of Bi2(Ca,Sr)3Cu2O8+δ (Tc∼85 K) and a thin film grown epitaxially on a (100) SrTiO3 substrate. Images taken at room temperature in air of a freshly cleaved bulk sample clearly show the one‐dimensional superstructure (27.2±0.7 Å periodicity) which is common to this phase. Several images show steps 16 Å high, suggesting that the cleavage occurs between 2122 molecular units. The registry of the superstructure from terrace to terrace is either shifted by half a superlattice parameter or is aligned. Images of evaporated thin films show features of comparable size, but not the same long‐range order as the crystal. Low‐temperature conductance measurements of the thin film exhibit a BCS‐like energy gap with 2Δ/kTc≊12.