City Research Online

Abstract

Low Energy Electron Diffraction and Auger Electron Spectroscopy have been applied to very simple alloy situations in which calibrated films of copper and gold have been grown epitaxially on platinum single crystals. The results of the quantitative use of A.E.S. for these alloy systems were found to depend on the presence of impurities and the surface atom geometry. LMM Auger peaks from copper films of 33 monolayers on Pt(100) were enhanced after oxygen treatment while no peak shape changes were detected.

Low surface mobility of copper on Pt(100) at 20°C prevented complete monolayer growth with apparent mean free paths for 927 eV and 239 eV electrons in copper of 3.1340.47 and 2.4040.36 monolayers at the copper density of 1.54 x 10'9 atoms m7°/monolayer. True monolayer growth occurred after 2 monolayers when the 927 eV m.f.p. was found to be 1.91 monolayers (3.4540,.52 f).

Pseudomorphic growth of copper on Pt(100) was observed up to 6 monolayers (platin m surface density 1.30 x 1019 atone n7*/monolayer) at 20°C. Gas adsorption on these surfaces differed from that on Pt(100) and did not form all reported Cu(100) structures. The adsorption of H,S, followed by LEED and A.E.S.,enabled copper island areas to be determined in films of <2 monolayers.

Copper formed disordered arrangements on Pt(111) at 2006 but grew epitaxially at 400°C.

A Pt(100) crystal surface exhibited a Pt(100)-(5x1) LEED pattern when cleaned to show no impurities by A.E.S. or when carbon was detected by LEED and A.E.S. The Pt(100)-(5x1) pattern, attributed to incomplete layers of distorted Pt(111) on Pt(100), reverted to Pt(100)-(1x1) after deposition of <0.1 8 of copper or gold.

Gold formed a Pt(100)-(7x1)-Au structure after 4.5 monolayers. This was attributed to a distorted Au(111) surface layer.

Publication Type:	Thesis (Doctoral)
Subjects:	Q Science > Q Science (General) Q Science > QD Chemistry
Departments:	School of Science & Technology School of Science & Technology > School of Science & Technology Doctoral Theses

Export

Downloads