Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions

← Older edit Newer edit →

VisualWikitext

@@ Line 131: / Line 131: @@
 the change due to the increase in temperature. It is currently unclear if the use of adhesion layers can have a positive impact on the stability of the Au nanostructure at elevated temperatures: this is the main point addressed in the following.
-Figure 6.1 shows the TKD maps of �lm nanostructure evolution for a di�erent set of temperatures of a 20 nm pure Au �lm (left column), 2 nm Ti/20 nm Au (center column) and 2 nm Cr/20 nm Au (right column) bilayer systems. The nanostructure of pure Au at room temperature consisted of small grains having [100] and [110] crystal orientations with respect to the sample surface orientation and larger grains having [111] orientation, as already described in the previous chapters. The �lm started to dewet between 100°C and 200°C. In general, the evolution of the nanostructure was in agreement with the results reported in Chapters 3 and 4. When Ti was used as adhesion layer, the nanostructure of Au at room temperature had a smaller grain size and complete [111] orientation, as described in Subsection 5.2.1. When the sample was treated with the same annealing conditions as pure Au, the e�ect of the temperature on the nanostructure was very di�erent: the annealing did not a�ect the continuity of the �lm up to 500°C and up to 200°C there was little grain growth. From 400°C the grain size started to increase, but not at the levels of pure Au. For the Cr/Au bilayer system, the Au �lm had a slightly smaller average grain size than in the Ti/Au case. Due to the low average grain size, a lot of grains were not properly indexed and are displayed as black areas. The Au layer maintained a continuous morphology
+Figure 15 shows the TKD maps of film nanostructure evolution for a different set of temperatures of a 20 nm pure Au film (left column), 2 nm Ti/20 nm Au (center column) and 2 nm Cr/20 nm Au (right column) bilayer systems. The nanostructure of pure Au at room temperature consisted of small grains having [100] and [110] crystal orientations with respect to the sample surface orientation and larger grains having [111] orientation, as already described above.
-up to 500°C also in this case, but the increase of the grain size was more limited than in the Ti/Au sample. A more quantitative analysis of the grain size increase for all three samples was performed between the map at room temperature and the one after the annealing at 200°C, since at such temperature the nanostructure of Au was still continuous and the dewetting was not a�ecting the analysis signi�cantly. The results are reported in Fig. 6.2.
-The average grain size of the pure Au sample increased from 97 nm to 105 nm in the evaluated temperature range (Fig. 6.2a), the one of the Ti/Au sample from 45 nm to 56 nm (Fig. 6.2b) and the one of the Cr/Au sample almost did not change, increasing from 34 nm to 36 nm (Fig. 6.2c). At higher temperatures, the Au grain size increase was very di�erent
+The film started to dewet between 100°C and 200°C. When Ti was used as adhesion layer, the nanostructure of Au at room temperature had a smaller grain size and complete [111] orientation. When the sample was treated with the same annealing conditions as pure Au, the effect of the temperature on the nanostructure was very different: the annealing did not affect the continuity of the film up to 500°C and up to 200°C there was little grain growth. From 400°C the grain size started to increase, but not at the levels of pure Au. For the Cr/Au bilayer system, the Au film had a slightly smaller average grain size than in the Ti/Au case. Due to the low average grain size, a lot of grains were not properly indexed and are displayed as black areas. The Au layer maintained a continuous morphology up to 500°C also in this case, but the increase of the grain size was more limited than in the Ti/Au sample.
-between the two adhesion layers. Figure 6.3a shows the variation for Ti/Au between room temperature and 500°C: the plotted average grain size value increased from 45 nm to 113 nm after the annealing. Figure 6.3b shows the variation for Cr/Au: in this case the grain size increase is lower, varying from 34 nm to 44 nm, highlighting the higher nanostructure stability guaranteed by Cr respect to Ti.
-In the pure Au and Ti/Au samples, was clearly visible with a visual inspection of the maps that the grain growth proceeded through grain coalescence (marked by white circles in the maps of Fig. 6.4). However, the mechanism of growth looks slightly di�erent between the two samples. In pure Au, the growth proceeds trough the coalescence between the smaller[100] and [110] grains and the larger and more energetically stable [111] grains, as already described in Subsection 4.4.2. In the Ti/Au sample instead, the coalescence takes place between [111] grains, since they are the only ones present in the nanostructure. The grain size increase in the Cr/Au sample is due to a mechanism most likely similar to the one of Ti/Au, as also this sample only [111] Au grains are present; however the grain coalescence was not immediately visible due to the higher stability of the Au nanostructure.
+[[File:PictureA.png|550px|center|thumb|Fig. 3: IPFZ maps showing the nanostructure evolution with temperature of a 20 nm pure Au �lm (left column), a 2nm Ti/20 nm Au bilayer (center column) and a 2nm Cr/20 nm Au bilayer system (right column).]]
+A more quantitative analysis of the grain size increase for all three samples was performed between the map at room temperature and the one after the annealing at 200°C, since at such temperature the nanostructure of Au was still continuous and the dewetting was not affecting the analysis significantly. The results are reported in Fig. 16. The average grain size of the pure Au sample increased from 97 nm to 105 nm in the evaluated temperature range (Fig. 16a), the one of the Ti/Au sample from 45 nm to 56 nm (Fig. 16b) and the one of the Cr/Au sample almost did not change, increasing from 34 nm to 36 nm (Fig. 16c). At higher temperatures, the Au grain size increase was very different between the two adhesion layers. Figure 17a shows the variation for Ti/Au between room temperature and 500°C: the plotted average grain size value increased from 45 nm to 113 nm after the annealing. Figure 17b shows the variation for Cr/Au: in this case the grain size increase is lower, varying from 34 nm to 44 nm, highlighting the higher nanostructure stability guaranteed by Cr respect to Ti.