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

The knowledge of the chemical composition and elemental distribution of the bilayer systems is important to understand the type of interaction between the layers and their different structure. To obtain such information, the bilayer systems were investigated using STEM-EDX, STEM-EELS and XPS depth profiling.

For the chemical distribution of the elements in the 2nm Ti/2nm  Au sample, the STEM-EDX measurements at the Ti/Au interface showed the presence of a continuous Ti layer below the Au layer (Fig. 8a). The analysis of the 2nm Cr/2nm Au sample showed instead the presence of Cr throughout the whole thickness of the Au layer (Fig. 8b). Since Cr and Au were deposited sequentially and not by a co-deposition process, this result suggests a strong inter-diffusion. The 2nm Cr/20nm Au sample was also investigated, to understand the degree of inter-diffusion for a thicker Au layer (Fig. 8c). In this case the inter-diffusion between the elements was incomplete, being present for a thickness of 2-3 nm. This suggests that the diffusion process is limited to such a thickness when Cr and Au are deposited at room temperature.

[[File:Picture29.png|550px|center|thumb|Fig. 8: STEM-EDX maps of the 2nm Ti/2nm Au sample (a), 2nm Cr/2nm Au sample (b) and 2nm Cr/20nm Au sample (c). The Au L-alpha signal is acquired at 9713 eV, the Ti K-alpha signal at 4510.9 eV and the Cr K-alpha signal at 5414.7 eV.]]

To verify the chemical composition of the samples, in particular to investigate a possible presence of oxygen in the adhesion layer, STEM-EELS analysis was used. A line scan across the layer interfaces of the 2-Ti/2-Au sample shows the presence of a Ti core loss L3 edge at 460 eV and an L2 edge at 465 eV. A SiO2 O-K edge is visible at 538 eV, while the O-K edge of O bounded to Ti is found at 532 eV (Fig. 5.10a).

 

direction, which con�rms di�usion into the Au layer. For the length of the tail there is no presence of OCr-K edge, indicating that Cr inside Au is in metallic form. This is in good agreement with the observed di�usion, which involves only metallic Cr.