Diplomarbeit Diplom-Ingenieur - Institut für Halbleiter

34
and increases the height of the PbTe material lines. The increase of the local layer
thickness can be seen in Fig. 4.2. The image shows a cross-sectional specimen of an
originally 5nm epi-layer sample. The PbTe wires contracts until the thickness of the
Figure 4.2: BF TEM image of an annealed PbTe layer recorded slightly away from the
[110] zone axis on a cross sectional specimen of series #31. Growth direction was along
the [001] axis. The sample was originally a 5 nm SQW and was annealed at 320°C for
10min, which was not sufficient for complete precipitation. The sample contains still
interconnected 2D part with a height form 5 to 20 nm. The lateral dimension shrinks for
thicker layers. Dot-shaped material with sharp interfaces can be seen in the 20 nm layer.
Figure 4.3: Images of several constrictions of the PbTe wires during the dot
precipitation. The images were recorded on a cross section specimen of series #5, as-
grown sample. (a) shows a DF image, (b) and (c) show BF images. The layer was
originally 5nm thick. The dot material already shows sharp interface to the host material.
The shape of the separated material shows larger in-plane dimensions than height.