Specific Process Knowledge/Thin film deposition/Deposition of Gold/Adhesion layers: Difference between revisions
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== Nano-optic devices == | == Nano-optic devices == | ||
For nano-optic devices there are two implications: | |||
1) the grain size values of the Au thin-�lms are comparable with the sizes of plasmonic nanostructures, which are 70-200 nm. Hence, each nanostructure might have multi-grain structures that are di�erent. This might a�ect its interaction with the light and its optical response, which leads to broadening of the optical resonance peaks. | |||
Second, during light and plasmonics device interactions, the temperature can locally raise to above 795 K [127], further enhancing the alloying of Cr and Au already present at room temperature and thus deteriorating the electrical properties of the thin-�lm stack. Ti does not inter-di�use with Au at room temperature, supported by the �4PP measurements which show that the electrical properties appear to be similar to pure Au thin-�lms. The formation of a stable Ti layer under the Au prevents di�usion of Au into the underlying substrate and improves the performance-time and temperature stability of the devices. The Ti-Au inter-di�usion starts at temperatures higher than 175°C. If the devices have to be used for prolonged time above this temperature, Pd [117] and Pt [119, 120] di�usion barriers must be used. Comparative studies show a localized surface plasmon damping in plasmonic | |||
nanostructures due to the presence of a very thin adhesion layer, and overall better performances of Ti over Cr for the optical resonance of such nanostructures [128, 129, 130]. Therefore, if the choice is limited to metallic adhesion layers, Ti is preferred over Cr for nano-optics applications. A perhaps even better alternative is to use organosilane-based adhesion layers. Comparative measurements of Ti vs Mercaptopropyltrimethoxysilane (MPTMS) [131] and Cr vs Aminopropyltrimethoxysilane (APTMS) [132] show overall better performances for the organosilane-based adhesion layers over the metallic ones. A considerable disadvantage of these molecular adhesion layers is their lack of compatibility with the lithographic and lift-o� processes, which still play an important role in the fabrication of nanostructures. | |||
== Nano-electronic devices == | == Nano-electronic devices == | ||