Diplomarbeit Diplom-Ingenieur - Institut für Halbleiter

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distribution is at about 30 nm and limited by 8 and 45 nm. If it is also taken into
account that the dot elongation can be parallel to the line of sight, most of the dots in
this sample are elongated. Unfortunately, no plan view specimen of this sample exists,
but it should look like the plan view image of Figure 4.4, which shows an annealed
3nm sample.
Figure 4.7: (a) Height distribution of the dots. The maximum is at 25nm. The upper limit
is at about 30nm. (b) Length distribution of the dots with the maximum at about 30nm.
4.3.2 Annealed 1nm layer
The same measurements were also performed for sample #28, with an originally 1nm
thick PbTe layer. The sample was annealed at 320°C for 10 min. The plan view
specimen of the sample was good enough for statistical evaluation. A cross sectional
specimen was also available and was used to check the highly symmetric shape,
which the dots show in the plan view sample. This can be seen in Figure 4.8. The
appearance of the dots in plan view is an octagon with longer {110} interfaces. The
distances between two parallel {110} interfaces were used to measure the size of the
dots. The cross sectional specimen shows the appearance of these dots in a line of
sight along the [ 110]
direction which confirmed the high symmetry. One interesting
point is the extended (111) interface of these small dots, which will be treated in part
4.4.
The distribution of the dot size can be seen in Figure 4.9. Figure 4.9a shows the
high symmetry of the dots, which seem to become ever better for larger dots. The
ideal case is again indicated with a solid line. The shift of the distribution to one side