Self-assembled magnetic nitride dots on Cu(100) surfaces

We describe here a procedure for the direct fabrication of a self-organized, ordered pattern of Fe4N magnetic dots on an otherwise clean Cu(100) surface. It is based on the evaporation of Fe in a flux of atomic N produced by a plasma source onto a Cu(100) surface kept at 700 K. The large-scale morphology of the surface is demonstrated by scanning tunneling microscope. The average lateral size of the islands is 10 nm and they penetrate three to four layers into the substrate. The iron nitride dots present a characteristic p4g(2 X 2) surface reconstruction, detected also on 25 nm thick, nonstructured films grown in the same conditions, on which x-ray diffraction, conversion electron Mossbauer spectroscopy, Rutherford backscattering spectroscopy, and magneto-optic Kerr effect confirm the existence of a pure magnetic, cubic, gamma'-Fe4N(100) layer epitaxial with the Cu(100) substrate.