Initial stages of Ni reaction both on Si(100) and hydrogen (H)-termina
ted Si(100)-(2 X 1)-H surfaces have been studied using scanning tunnel
ing microscopy (STM). STM images reveal that deposited Ni atoms react
directly with Si atoms on the clean surface and induce defective sites
, while those on the H-terminated surface are prevented from reacting
with Si atoms and forms clusters. In the latter case, we find a new ad
sorption site of Ni atom which sticks in dimerised Si atoms, causing t
he dimer splitting into both sides. It is also found that, in the case
of the deposition on the clean surface followed by annealing, the Si
substrate surrounding NiSi2 island is rather disordered, while on the
H-terminated surface, the surface shows a homogeneous (2 x n) structur
e, reflecting the surface morphology at the initial stages of Ni react
ion. (C) 1998 Elsevier Science B.V. All rights reserved.