We have studied 6H-SiC(0 0 0 1)Si surfaces with and without Ni atoms on top. 6H-SiC(0 0 0 1) clean surfaces were obtained by resistive heating of a SiC sample for a few minutes at about 1100 degreesC in UHV Structural change of such clean 6H-SiC(0 0 0 1) surface was studied by scanning tunneling microscope (STM) after heat treatment at several temperatures. Then we deposited 1-2 Angstrom of Ni on thus cleaned surface. The initial stage of the adsorption process of Ni atoms on 6H-SiC(0 0 0 1) substrate was analyzed using STM to clarify Ni islands formation. Furthermore, we heated Ni(1-2 Angstrom)/6H-SiC(0 0 0 1)Si specimens at 400-800 degreesC. After heating at 600 degreesC, 2root3 x 2root3 surface structure was observed. Structure model of this surface has been proposed. (C) 2003 Elsevier Science B.V. All rights reserved.