AVS 46th International Symposium
    Surface Science Division Tuesday Sessions
       Session SS-TuP

Paper SS-TuP21
Nickel Graphite Intercalation Compound formed by High Temperature Deposition of Ni on SiC

Tuesday, October 26, 1999, 5:30 pm, Room 4C

Session: Poster Session
Presenter: K. Robbie, Linköping University, Sweden
Authors: K. Robbie, Linköping University, Sweden
T. Jemander, Linköping University, Sweden
N. Lin, Linköping University, Sweden
R. Erlandsson, Linköping University, Sweden
G.V. Hansson, Linköping University, Sweden
L.D. Madsen, Linköping University, Sweden
Correspondent: Click to Email
While studying the growth of sputter-deposited nickel on 6H SiC (0001) substrates, an unexpected islanded structure was formed. Nickel, deposited at room temperature and annealed to 950 C to form Ni@sub 2@Si, is the most common approach for forming ohmic contacts to n-type SiC. In this study aimed at gaining understanding of the contact formation process, we sputter-deposited Ni layers of varying nominal thickness (sub- to 1000 monolayers) onto hydrogen-etched on-axis SiC substrates at temperatures ranging from ambient to 1000 C and subsequently annealed to 1000 C. In-situ analysis was performed with RHEED, LEED and/or STM. Unlike all previous experience with Ni deposited onto SiC, we observed the formation of islands of two types, one of which had very steep sidewalls (>60 degrees) and an extremely flat top with a peculiar "stitched" surface structure. Microspot AES analysis has shown that the islands are composed of Ni and C, or Ni, Si, and C, and that the carbon is bound graphitically in both types. Investigations with STM, AFM, and AES, and comparison to literature, has led us to believe that a new type of graphite intercalation compound was formed in the flat topped islands with a composition of approximately NiC@sub 12@, and that Ni on the top graphite sheet produced the "stitched" surface structure observed by STM. Previously, only alkali metals and transition metal chlorides have been shown to intercalate into the galleries of graphite, and the reactivity and instability of these compounds has limited their use in spite of their very exciting electronic, magnetic, and other physical properties.