• Weststrate, C. J. Kees-Jan
• Lauritsen, Jeppe Vang
• Li, Zheshen
• Niemantsverdriet, J. W. Hans
• Gleeson, Michael A.
• Rodríguez, Daniel García
• Yu, Xin

Abstract

<p>Thin iron films evaporated onto Cu(1 0 0) were carburized using ethylene to produce iron carbide surfaces for use as model systems in experimental research. XPS and AES confirm that ethylene dissociation produces a pure iron carbide. A maximum of 0.5 ML carbon can be deposited for film thicknesses below 12 ML where Fe grows as γ-iron (FCC). For thick, BCC-Fe(1 1 0) films, post-treatment with ethylene leads to carbon coverages beyond 0.5 ML where some carbon diffuses into the bulk. The film remains α-iron (BCC) and a different surface carbide with a (4 × 3) unit cell is found. On the thin FCC-Fe(1 0 0) films, carbon reconstructs the surface into a p4g(2 × 2)-Fe₂C layer which has a special stability and acts as a carbon trap that prevents carbon diffusion into the bulk. Fe₂C is thermally stable up to 700 K above which Fe diffuses into the copper substrate while leaving graphitic carbon behind. Carbon segregates to the surface during evaporation of iron on top of an Fe₂C-covered FCC-Fe film and causes the film to retain the FCC structure up to a thickness of at least 30 ML, far beyond 12 ML where BCC-Fe forms on Cu(1 0 0) in absence of surface carbon.</p>

Topics

• impedance spectroscopy
• surface
• Carbon
• x-ray photoelectron spectroscopy
• carbide
• copper
• iron
• evaporation
• atomic emission spectroscopy
• Auger electron spectroscopy