Abstract.
The low-energy electronic structure of a c-axis SrxAyCuO2 (A is alkaline earth cation, x+y≦1, hole- and electron-doped infinite layer) thin film, grown by laser-molecular-beam epitaxy on a SrTiO3 (001) substrate, has been studied using ultrahigh-vacuum scanning tunneling microscopy/spectroscopy. Images have been obtained for co-deposited SrxAyCuO2 thin films, which show the surface consisting of flat terraces separated by steps that are unit cell high. Tunneling spectra of undoped Sr0.3Ca0.7CuO2 indicate a wide band gap of 1.8 eV which is consistent with the charge transfer gap. Hole-doped Sr0.85CuO2 shows in-gap states appearing at both the valence and conduction band edges. In contrast, for the electron-doped Sr0.9La0.1CuO2, in-gap states appear predominantly above the Fermi level, and the spectral shape becomes asymmetric around the Fermi level. When these two systems are compared, barrier-height measurements reveal that there is no apparent shift of the Fermi level measured from the vacuum level. This suggests that the framework of the rigid-band picture might break down implying a strongly correlated electron system.
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Received: 20 August 1998 / Accepted: 15 February 1999 / Published online: 5 May 1999
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Matsumoto, T., Kawai, T. In-gap density of states in hole- and electron-doped CuO2 planes probed by scanning tunneling spectroscopy . Appl Phys A 68, 687–690 (1999). https://doi.org/10.1007/s003390050961
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DOI: https://doi.org/10.1007/s003390050961