In-Situ Surface Recombination Measurements of Oxygen Atoms on Anodized Aluminum in an Oxygen Plasma

• Published in: Journal of physical chemistry. C Vol. 112; no. 24; pp. 8963 - 8968
• Main Authors: Guha, Joydeep, Kurunczi, Peter, Stafford, Luc, Donnelly, Vincent M, Pu, Yi-Kang
• Format: Journal Article
• Language: English
• Published: American Chemical Society 19.06.2008
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp800788a

We observed the recombination of O atoms on a plasma-conditioned, anodized aluminum surface at room temperature. A cylindrical substrate was continuously exposed to the plasma and to a differentially pumped chamber where either Auger electron spectroscopy (AES) or mass spectrometry was used to detect surface and desorbing species. After long exposure to the oxygen inductively coupled plasma, the surface was heavily oxidized and contained 10% Si, a product of erosion of the fused silica discharge tube. Langmuir−Hinshelwood recombination coefficients for O on this surface were derived from the time-resolved desorption of O2, observed with delay times of 1−40 ms after plasma exposure. Recombination coefficients varied from γO = 0.06 ± 0.02 in the limit of low O flux (ΓO ≤ 1 × 1016 cm−2 s−1) to γO = 0.04 ± 0.01 0.02 at ΓO = 7.5 × 1016 cm−2 s−1. From the lack of any significant time-dependent change in O coverages measured by AES, it was concluded that a small fraction of the adsorbed O participated in surface recombination.