Determination of electronic structure of oxide-oxide interfaces by photoemission spectroscopy.
A method has been developed to use the finite escape depth of the photoelectrons emitted in ultraviolet photoemission spectroscopy (UPS) to determine the electronic density-of-states at the interface between two dissimilar metal oxides. Ultrathin films of one oxide are grown heteroepitaxially, one monolayer at a time, on a single-crystal substrate of the other oxide, and UPS spectra are taken after each complete monolayer. By comparing experimental UPS spectra with calculated spectra based on specific models of the interfacial structure, the interfacial density-of-states can be extracted. The two oxide systems studied here are NiO-Fe(3)O(4) and CoO-Fe(3)O(4). The former system is found to have an atomically abrupt interface, with no significant density of interface states. For CoO, however, an interfacial electronic spectrum, different from that of either the substrate or the overlayer, is found. The spatial extent and possible origin of those interfacial states is discussed.
Wang
Hui-Qiong
HQ
Center for Research on Interface Structures and Phenomena, Department of Applied Physics, Yale University, New Haven, CT 06520, USA.
Altman
Eric
E
Broadbridge
Christine
C
Zhu
Yimei
Y
Henrich
Victor
V
D003035:Cobalt / Q000737:chemistry; D052203:Ferrosoferric Oxide / Q000737:chemistry; D008958:Models, Molecular; D009532:Nickel / Q000737:chemistry; D010087:Oxides / Q000737:chemistry*; D056951:Photoelectron Spectroscopy
D010087:Oxides; D003035:Cobalt; D009532:Nickel; C028007:nickel monoxide; C060728:cobalt oxide; D052203:Ferrosoferric Oxide