Ni atoms (Ni-1) and nanoclusters (Ni-3,Ni-9) were deposited on clean Si(1 1 1)-(7 x 7) surfaces by a soft landing method at room temperature. Observations by X-ray photoelectron spectroscopy have revealed that the sticking probability of Ni-1 to the Si substrate is significantly smaller than that of Ni-3 or Ni-9. It was suggested by direct observations using scanning tunneling microscopy that Ni-9 clusters are separately fixed to the position where they landed, while Ni3 clusters diffuse on the surface and aggregate into characteristic nanosized structures. (C) 2002 Elsevier Science B.V. All rights reserved.