Abstract
The preparation of thin films of two niobium carbides, NbC and Nb2C, for electron diffraction studies has been accomplished by heating in vacuo double evaporated films (carbon+Nb). NbC is formed by a carburization process in high vacuum, whilst thin films of Nb2C are produced by decomposition of NbC in air at reduced pressure (10-2∼10-3 Torr) by the reaction 2 NbC+O2 → Nb2C+CO2. The crystal structure of NbC is based on the f.c.c. lattice of Nb atoms and the carbon atoms occupy interstitial positions in a statistical manner. Nb2C, however, shows a hexagonal superlattice structure of the same type as that of ε-phase of Fe2N.

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