We have investigated the (0 0 1) surface of single crystal niobium annealed
at 1000 degreesC in ultra-high vacuum. Oxygen as well as niobium atoms wer
e detected from the surface with the composition ratio of Nb:O = 1:0.9 by X
-ray photoemission spectroscopy. Scanning tunneling microscopy observation
revealed that the entire surface is covered by small (nanometer in size) pr
otrusions having a pyramid shape with a flat top. Based on these results we
have concluded that the protrusions are single nano-crystals of NbO grown
epitaxially on the (001) surface of metallic niobium. (C) 2001 Elsevier Sci
ence B.V. All rights reserved.