| AVS 55th International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThP |
| Session: | Aspects of Thin Films |
| Presenter: | G. Kutluk, Hiroshima University, Japan |
| Authors: | G. Kutluk, Hiroshima University, Japan M. Nakatake, Hiroshima University, Japan H. Namatame, Hiroshima University, Japan M. Taniguchi, Hiroshima University, Japan |
| Correspondent: | Click to Email |
Small change in the electronic structure of lantanide-based compounds may lead to quite distinct alteration in physical properties, and such systems have considerable technological interest since they are being used in e.g., microelectronic industry, in catalysis, and in strong permanent magnets. Sm may be of particular interest from a fundamental point of view since two different isoenergetic states may coexist. Relatively small change in chemical environment may induce a change in the valence states. In order to limit (or prevent) interface alloy formation between substrate, the HOPG (highly oriented pyrolytic graphite) was chosen as substrate. HOPG surface is very inert, and therefore sample cleaning is much less time-consuming compared to other substrates. Oxygen chemisorption on Sm overlayer can be more easily studied using graphite surfaces than on oxide surfaces, since there is no background oxygen signal on graphite surfaces. Metallic properties of HOPG allow electron spectroscopy and microscopy experiments without surface charging problem. In situ photoemission spectroscopy on Sm overlayers on HOPG in coverage regime 0.2~10Å were performed at room temperature in an ultrahigh vacuum (UHV) with base pressure of 1x10-10 torr. The resonance photoemission spectra indicate that the divalent feature was observed for the coverage below than 1.0Å, and the trivalent structures are enhanced for films coverage exceeding the 1.0Å. The oxidization of Sm overlayers even in an UHV environment cannot be avoided during measurement, however that is not only due to the residual oxygen species attacking to Sm normally, the VUV (Vacuum ultraviolet) light also take a part of stimulating the oxidization process, that has been observed from valence band spectra. And the morphology of Sm overlayer was evaluated by AFM (atomic force microscopy). A self-assembled nanostuctures of shower of cherry blossoms shape (island shape) dominate the morphology of Sm overlayer in a lower coverage regime below than 1.0Å. The Sm overlayers were deposited on to HOPG in an UHV chamber with base pressure of 3x10-10 torr, and transferred to measurement chamber without exposing to the atmosphere. The coverages of Sm films were monitored by a quartz-crystal microbalance. The VUV light supplied from monochrometor BL-7 was employed for the photoemission spectroscopy at Hiroshima synchrotron radiation research center (HiSOR)