LabAdviser/314/Microscopy 314-307/SEM/Nova/Transmission Kikuchi diffraction: Difference between revisions
| Line 68: | Line 68: | ||
Figures 8 and 9 show the IPFZ maps overlaid with pattern quality for temperatures varying from 20°C to 900°C. A preliminary investigation of the Au film at room temperature revealed a bimodal nanostructure, with the presence of small grains with size in the range of 30 nm and large grains with size in the 150 nm range. The latter ones showed a strong [111] out-of-plane texture. During heating, the [111] grains tended to grow faster than the [110] and [100] ones. It is also possible to observe that grain growth started at a temperature below 150°C, while holes are visible at 170°C (highlighted with a red circle). The holes were formed in the vicinity of non-preferentially oriented (non-PO) [110] and [100] grains, which were also the site where the hole growth was continuing. | Figures 8 and 9 show the IPFZ maps overlaid with pattern quality for temperatures varying from 20°C to 900°C. A preliminary investigation of the Au film at room temperature revealed a bimodal nanostructure, with the presence of small grains with size in the range of 30 nm and large grains with size in the 150 nm range. The latter ones showed a strong [111] out-of-plane texture. During heating, the [111] grains tended to grow faster than the [110] and [100] ones. It is also possible to observe that grain growth started at a temperature below 150°C, while holes are visible at 170°C (highlighted with a red circle). The holes were formed in the vicinity of non-preferentially oriented (non-PO) [110] and [100] grains, which were also the site where the hole growth was continuing. | ||
<gallery widths="550px" heights="550px" perrow="2" halign="center"> image:Picture29.png|Fig. 8: IPFZ maps of the 15 nm Au | <gallery widths="550px" heights="550px" perrow="2" halign="center"> image:Picture29.png|Fig. 8: IPFZ maps of the 15 nm Au film, overlaid with pattern quality map, recorded at temperatures between 20°C and 240°C. | ||
image:Picture30.png|Fig. 9: IPFZ maps of the 15 nm Au | image:Picture30.png|Fig. 9: IPFZ maps of the 15 nm Au film, overlaid with pattern quality map, recorded at temperatures between 250°C and 900°C. </gallery> | ||
The yellow rectangles follow instead the delayed hole growth due to the presence of preferentially oriented (PO) [111] grains: the hole is visible from 170°C and grows until it is completely surrounded by larger PO grains, subsequently its growth is retarded until 500°C, while other holes continue to grow. When a hole meets a grain having a low interface energy (in this case a [111] grain), edge retraction is inhibited due to the reduced driving force for dewetting, because these grains are energetically very stable. The low-interface energy grains, which inhibited the retraction, continue to grow at the expense of neighboring grains having higher interface energy, resulting in abnormal grain | The yellow rectangles follow instead the delayed hole growth due to the presence of preferentially oriented (PO) [111] grains: the hole is visible from 170°C and grows until it is completely surrounded by larger PO grains, subsequently its growth is retarded until 500°C, while other holes continue to grow. When a hole meets a grain having a low interface energy (in this case a [111] grain), edge retraction is inhibited due to the reduced driving force for dewetting, because these grains are energetically very stable. The low-interface energy grains, which inhibited the retraction, continue to grow at the expense of neighboring grains having higher interface energy, resulting in abnormal grain | ||
growth, and the hole continues to grow in directions where grains along the hole edge have a higher interface energy with the substrate. This expansion only stops when the hole becomes completely sorrounded by low-interface energy grains, as in the case of Fig. 8 and 9. | growth, and the hole continues to grow in directions where grains along the hole edge have a higher interface energy with the substrate. This expansion only stops when the hole becomes completely sorrounded by low-interface energy grains, as in the case of Fig. 8 and 9. | ||
Since TKD measurements provided a large amount of data for each | Since TKD measurements provided a large amount of data for each scanned point in the map (54000 total acquired points at the step size of 10 nm), statistically significant quantitative data analysis could be performed from this series of measurements. The two classes of grains already observed in Fig. 9 were analyzed, defined as i) PO-grains with [111]//growth direction (using tolerance angle of 15°) and ii) non-PO grains with other orientations. The average grain size evolution of both classes of grains is shown in Fig. 10a for annealing temperatures up to 600°C. | ||
scanned point in the map (54000 total acquired points at the step size of 10 | |||
nm), statistically | The graph confirms the trend from the maps shown in Fig. 8, revealing that grain growth started already at 120°C. The PO grains were larger than the non-PO ones already from the starting nanostructure and grew considerably faster: by a temperature of 220°C, PO grains have almost triplicated their average size, while non-PO grains maintained their average size of 33 nm. Furthermore, up to 550°C practically only the PO grains grew. Fig. 10b shows the evolution of the number of indexed points for the two classes of grains, while Fig. 10c shows the number of grains of each class during annealing. The data shows that the fraction of indexed points and the number of non-PO grains started to decrease at the annealing temperature of 150°C. Considering that the holes were formed near non-PO grains as described above, the decrease of non-PO indexed points can be considered as a signal of hole formation in the film, even if holes are not visible in the image at that temperature. For PO grains, the fraction of indexed points kept increasing up to 350°C, while the number of grains already started to decrease at 180°C, indicating that such grains kept growing and coalescing before the dewetting process took place. | ||
from this series of measurements | |||
already observed in Fig. | |||
[111]//growth direction (using tolerance angle of 15°) and ii) non-PO grains | |||
with other orientations. The average grain size evolution of both classes of | |||
grains is shown in Fig. | |||
The graph | |||
that grain growth started already at 120°C. The PO grains were larger | |||
than the non-PO ones already from the starting nanostructure and grew | |||
considerably faster: by a temperature of 220°C, PO grains have almost triplicated | |||
their average size, while non-PO grains maintained their average size | |||
of 33 nm. Furthermore, up to 550°C practically only the PO grains grew. | |||
Fig. | |||
the two classes of grains, while Fig. | |||
each class during annealing. The data shows that the fraction of indexed | |||
points and the number of non-PO grains started to decrease at the annealing | |||
temperature of 150°C. Considering that the holes were formed near non-PO | |||
grains as described above, the decrease of non-PO indexed points can be | |||
considered as a signal of hole formation in the | |||
visible in the image at that temperature. | |||
[[File:Picture17.png|400px|center|thumb|Fig. 6: Schematic illustration of the on-axis TKD detector configuration.]] | |||
== Determination of the temperature of formation of the first hole == | == Determination of the temperature of formation of the first hole == | ||