(a) 100 µm - Helmholtz-Zentrum Berlin

66 Results
annealed at TA = 450 °C. This leads to the conclusion that the nucleation density
does not correspond directly to a crystallographic grain size. Further investiga-
tions concerning the structure within the areas growing from one nucleus in the
seed layers have to be performed.
The inverse pole figures for the two most distinct case for (a) the sample type B
(native oxide) annealed at low temperature (TA = 450 °C) and (b) sample type
C (thermal oxide) annealed at high temperature (TA = 550 °C) are shown in
Fig. 4.13. The inverse pole figure is the superposition of all equivalent orienta-
tions. The three corners correspond to the the three low index orientations (100),
(110) and (111) like the color code from the EBSD maps. The detection spots
agglomerate close to the (100) orientation in Fig. 4.13(a) and close to the (111)
orientation in Fig. 4.13(b).
In order to quantify the result obtained for the different samples the red fraction
of the maps has been analyzed. The red fraction is changed with the tilting angle
α with respect to the (100) orientation (α = 0° = (100)). All angles larger than 45°
have no red fraction. The ratio of orientation within α ≤ 20° to the overall area
under investigation is referred to as preferential (100) orientation R(100). Fig. 4.14
shows R(100) for the six EBSD maps. The solid circles correspond to the native
oxide results (sample type B) and the open circles to the thermal oxide (sample
type C). The above described trend can be confirmed for the preferential (100)
orientation R(100). The native oxide and lower annealing temperature TA enhance
the degree of preferential (100) orientation. For the sample of type B annealed at
450 °C R(100) is close to 70 %. For sample of type C and an annealing temperature
of 550 °C R(100) decreased below 10 % 5 .
Usually preferential orientations are determined by the fastest growth of a partic-
ular orientation. Depending on the velocity of a process or subprocess preferential
orientations are formed. In the presented case the thermal oxide (sample type C)
5 The preferential (100) orientation R(100) is quantitative but limited number for the orientations
in the films. It allows for a quantitative evaluation but comparison of the EBSD maps in Fig. 4.12
with the result shown in Fig. 4.14 shows strong differences even for similar R (100).