Adsorbat-modifiziertes Wachstum ultradünner Seltenerdoxid ... - E-LIB

Abstract
Rare-earth oxides (REOx) are extensively investigated due to their extraordinary
physical and chemical properties, which essentially arise from the unfilled 4f electron
shell, in order to reveal the nature of these exceptional properties and ultimately to
utilize them for multiple technological applications.
To maintain the exponential increase in integration density in CMOS technology,
which is also known as Moore’s law, there is a strong desire for ultrathin, wellordered,
epitaxial REOx layers with a precisely engineered interface, which is essential
for reliable, ultrahigh-performance devices [2]. So far this has been considerably
impeded by RE-promoted silicon oxidation, leading to amorphous silicon oxide and
RE silicon formation [3].
By using complementary synchrotron radiation methods such as X-ray standing waves
(XSW), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD),
structural and spectroscopic information are inferred simultaneously from ultrathin
ceria and lanthana films grown on chlorine, silver and gallium passivated silicon(111).
In general, it is revealed that the chemical and structural composition of the interface
and the crystallinity of ultrathin REOx layers on silicon can be precisely controlled
by adsorbate-mediated growth. This might represent a crucial step towards a
perfectly engineered interface, eventually allowing for the integration of REOx as
high-k gate oxides in microelectronics.
In catalysis inverse model catalysts are studied with the aim of getting an in-depth
understanding of the basic principles of catalysis. These model systems are employed
to study, e. g., the nature of active sites and the reaction pathways in complex
catalytic converters. However, a lot remains unknown about the chemical activity
and selectivity as a function of the growth mechanism, structure and morphology of
these model systems.
The powerful spectroscopic photoemission and low-energy electron microscope, which
is able to reveal the surface structure and chemical composition at nanometer resolution,
is used to shed light on the growth, morphology and oxidation state of the
inverse model system ceria on ruthenium(0001) up to very high growth temperatures
of 1000 ℃. It is revealed that ceria on ruthemium(0001) forms a commensurate
phase. Specifically, it is shown that the ceria island size and nucleation density can
be adjusted by appropriate growth conditions, potentially giving the ability to tailor
the reactivity of the catalyst through precise structural control.
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