• Le Pévédic, S.
• Schmaus, D.
• Cohen, Christina

Abstract

In this paper we describe the alloying process of ultra-thin Al layers (below 8 × 10 <SUP>15</SUP> Al/cm <SUP>2</SUP>) deposited on Ni(1 1 1). For this purpose Auger electron spectroscopy, low energy electron diffraction, and ion beam analysis-channelling measurements have been performed in situ in an ultra-high vacuum chamber. Al deposits formed at low temperature (about 130 K) are strained defective crystalline layers retaining the substrate orientation. Alloying takes place, with very progressive Ni enrichment, in a very broad temperature range between 250 K and 570 K. This feature shows that diffusion of the alloy species is more and more difficult when the Ni concentration increases. At 570 K a crystallographically and chemically ordered Ni <SUB>3</SUB>Al phase is formed, and its order continuously improves upon annealing, up to 750 K. We have shown by ion beam methods that this alloy is three-dimensional, extending up to 16 (1 1 1) planes for the thickest deposits. The Ni <SUB>3</SUB>Al phase can also be obtained directly by Al deposition at 750 K, but its crystalline quality is lower and the layer is probably formed of grains elongated along &lt;1 1 -2&gt; directions. The Al content of the thin Ni <SUB>3</SUB>Al layers formed mostly dissolves in the bulk above 800 K. However a small amount of Al remains segregated at the Ni crystal surface....

Topics

• Deposition
• impedance spectroscopy
• surface
• grain
• phase
• annealing
• Auger electron spectroscopy
• low energy electron diffraction