Chemistry Reference
In-Depth Information
Fig. 11.7
REM images of Si(111) surface morphology during annealing at 900
◦
C after deposition
of 0.7ML of gold (
a
-
d
)
into the bulk. After 16min of annealing the step-bunched structure (Fig.
11.7
a) was
fluently transformed into an array of regular steps (Fig.
11.7
b). This transformation
was supplemented by atomic step motion in both (step-up and step-down) direc-
tions and increasing fluctuations of step shape. At the same time the observation
of RHEED pattern revealed no any additional reflections at 900
◦
C but the intensity
of the basic (1
1) reflections increased in comparison with one measured imme-
diately after gold deposition. After formation of regular array of atomic steps the
sample temperature was reduced to 500
◦
C and the RHEED picture was analyzed.
Additional patterns corresponding to the Si(111)-(5
×
2)Au reconstruction were reg-
istered. According to the surface phase diagrams [
55
,
56
] the formation of the (5
×
2)
domains on gold-deposited silicon surface occurs in gold coverage range of 0.42-
0.6ML.
Subsequent isothermal annealing at 900
◦
C in an ultra high vacuum chamber dur-
ing 23min caused step bunching (Fig.
11.7
c). This transition was supplemented
by increasing the (1
×
1) reflection intensity at RHEED pattern. Further annealing
during 27min caused the formation of regular steps on the surface (Fig.
11.7
d).
Decreasing to 500
◦
C, RHEED picture clearly identified the (7
×
×
7) reflections that
