Barrier-height (BH) imaging using scanning tunneling microscopy (STM) was used to study the growth of Co films on Au(001) surfaces. We have observed BH of metastable bcc Co film (>1 ML) for the first time, and that showed a large BH value (similar to 6 eV), whereas the observed BH of the Au(001) surface (similar to 3.5 eV) was consistent with the previous results. The origin of the large BH was qualitatively understood by considering that 3d electrons for tunneling are dominant for the Co(001) surface. We have observed numerous islands with different sizes and heights after 0.15 ML Co coverage and successfully obtained, from the BH imaging, an element-specific contrast, i.e. recognizing aggregated Au islands and Co islands, and information about inhomogenities of BH with proper consideration of the artifacts near the step edges. The height modification by the large BH difference is discussed.
STM/BH studies of FePt films revealed two kinds of monolayer heights, the sum which was equal to the c axis lattice constant of L1(O) FePt. Two different dl/dz signal levels were observed on atomically flat terraces. (C) 2011 Elsevier B.V. All rights reserved.