Cesium/oxide interactions for ultrathin films on {alpha}-Al{sub 2}O{sub 3}(0001) and {alpha}-Al{sub 2}O{sub 3}(1{bar 1}02)
- Sandia National Labs., Albuquerque, NM (United States)
- AEA Technology, Albuquerque, NM (United States)
The interaction of cesium at the (0001) and (1{bar 1}02) surfaces of sapphire has been investigated using a variety of surface analytical techniques. Reflection mass spectrometric measurements yield initial Cs adsorption probabilities of 0.9 and 0.85 for the unreconstructed (0001) and (1{bar 1}02) surfaces, respectively. The adsorption probability decreases dramatically for these surfaces at critical Cs coverages of 2.O {times} 10{sup 14} and 3.4 {times} 10{sup 14} atoms/cm{sup 2}, respectively. Thermally induced reconstruction of the (0001) surface to form an oxygen deficient surface results in a decrease in the initial probability and capacity for Cs adsorption. Low energy electron diffraction (LEED) demonstrates that an intermediate, mixed domain surface yields an initial adsorption probability of 0.5 while a ({radical}31 {times} {radical}31) R {plus_minus} 9{degree} reconstructed surface yields a value of 0.27. Thermal desorption mass spectrometry (TDMS) shows that surface reconstruction eliminates the high binding energy states of Cs (2.7 eV/atom), consistent with the observed changes in adsorption probability. In contrast, reconstruction of the (1{bar 1}02) surface produces only minor changes in Cs adsorption. X-ray photoelectron spectroscopy (XPS) indicates that no formal reductive/oxidative chemistry takes place at the interface. We interpret the facile adsorption and strong binding of Cs on sapphire to result from Cs interacting with coordinatively unsaturated oxygen.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC04-94AL85000
- OSTI ID:
- 31677
- Report Number(s):
- SAND--95-0309C; CONF-941144--84; ON: DE95008159
- Country of Publication:
- United States
- Language:
- English
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