Accession Number:

ADA160699

Title:

A SIMS Study of the Influence of Low Levels of Silicon and Calcium on the Adsorption Properties of O2 on Pt(111).

Descriptive Note:

Technical rept. 1 Jan-31 Dec 85,

Corporate Author:

TEXAS UNIV AT AUSTIN DEPT OF CHEMISTRY

Report Date:

1985-10-15

Pagination or Media Count:

17.0

Abstract:

Surface impurity levels of Calcium, Silicon and Aluminum at or below the detectability limits of AES were followed in SIMS and correlated with oxygen adsorption on Pt 111. It is shown that oxidation of Silicon to Si0x, monitored by the rise in SIMS Si ion intensity, takes place above 5400K during oxygen TPD. Si0x starts decomposing above 1100K and can be reduced within 200 sec by 2x10 to the minus 8th power torr of H2 at 1200K. The oxygen adsorbeddesorbed in a TPD cycle depends on the immediate history of the impurity levels on the surface. Si0x presence correlates with an increase in the overall oxygen sticking coefficient. These results highlight the importance of impurity levels below AES detectability and suggest pretreatment methods for obtaining better reproducibility.

Subject Categories:

  • Atomic and Molecular Physics and Spectroscopy

Distribution Statement:

APPROVED FOR PUBLIC RELEASE