Thin film solid-state reactions forming carbides as contact materials for carbon-containing semiconductors

Abstract

Metal carbides are good candidates to contact carbon-based semiconductors (SiC, diamond, and carbon nanotubes). Here, we report on an in situ study of carbide formation during the solid-state reaction between thin films. The solid-state reaction was examined between 11 transition metals (W, Mo, Fe, Cr, V, Nb, Mn, Ti, Ta, Zr, and Hf) and an amorphous carbon layer. Capping layers (C or TiN) of different thicknesses were applied to prevent oxidation. Carbide formation is evidenced for nine metals and the phases formed have been identified (for a temperature ranging from 100 to 1100 °C). W first forms W2 C and then WC; Mo forms Mo2 C; Fe forms Fe3 C; Cr first forms metastable phases Cr2 C and Cr3 C2-x, and finally forms Cr3 C2; V forms V Cx; Nb transforms into Nb2 C followed by NbC; Ti forms TiC; Ta first forms Ta2 C and then TaC; and Hf transforms into HfC. The activation energy for the formation of the various carbide phases has been obtained by in situ x-ray diffraction. © 2007 American Institute of Physics.