Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions
| Line 42: | Line 42: | ||
The smaller grain size is attributed to an enhanced wetting of the deposited Au promoted by the adhesion layer. The enhanced wetting behaviour increases the number of nucleation sites compared to the pure Au film case, where Au is evaporated directly onto the SiO2 surface. This eventually leads to a much denser nucleation of the Au grains, which at the | The smaller grain size is attributed to an enhanced wetting of the deposited Au promoted by the adhesion layer. The enhanced wetting behaviour increases the number of nucleation sites compared to the pure Au film case, where Au is evaporated directly onto the SiO2 surface. This eventually leads to a much denser nucleation of the Au grains, which at the | ||
same time facilitates the inter-diffusion of Au atoms. The enhanced wetting might be due to the formation of Ti-Au and Cr-Au bonds. The very dominant [111] crystal orientation observed implies a decrease of the energy barrier for the formation of the energetically most favourable Au crystal structure. This is promoted by the denser nucleation and stronger inter-diffusion of Au atoms described above. In contrast to the pure Au case, all the grains have the same diffusion rate of the (111) exposed planes, and therefore the grains grow with a narrow grain size distribution. Since the film has been deposited at room temperature, the system did not have enough energy to overcome the energy barrier for grain coalescence, hence resulting in grains with a small average size. For the Cr case, also small grains with [100] and [110] crystal orientations were detected. This might suggest that for Au on Cr the [111] orientation is energetically less favored with respect to the [100] and [110] orientations compared to the Ti/Au case. | same time facilitates the inter-diffusion of Au atoms. The enhanced wetting might be due to the formation of Ti-Au and Cr-Au bonds. | ||
The very dominant [111] crystal orientation observed implies a decrease of the energy barrier for the formation of the energetically most favourable Au crystal structure. This is promoted by the denser nucleation and stronger inter-diffusion of Au atoms described above. In contrast to the pure Au case, all the grains have the same diffusion rate of the (111) exposed planes, and therefore the grains grow with a narrow grain size distribution. Since the film has been deposited at room temperature, the system did not have enough energy to overcome the energy barrier for grain coalescence, hence resulting in grains with a small average size. For the Cr case, also small grains with [100] and [110] crystal orientations were detected. This might suggest that for Au on Cr the [111] orientation is energetically less favored with respect to the [100] and [110] orientations compared to the Ti/Au case. | |||
== Bilayer chemical composition and elemental distribution == | == Bilayer chemical composition and elemental distribution == | ||