Thermo-mechanical evolution of multilayer thin films: Part II. Microstructure evolution in Au/Cr/Si microcantilevers

Residual stress evolution during long-term and cyclic aging and annealing of gold films deposited by electron beam evaporation

“…This is in Table 1 Experiment procedure of cyclic aging and annealing of gold films. 1 NP TH NP TH TH NP TH TH NP TH TH TH NP TH TH TH TH accordance with the literature that twins are seen frequently in gold thin films due to low stacking fault energy [16]. Ignoring the twin boundaries, an irregular column structure can be clearly seen.…”

“…The same effect can also be used to explain the tensile stress generation during post-deposition annealing. Miller [14e16] indicated that defect annihilation was the reason for tensile stress generation caused by annealing in a limited regime (T < 125 C) [15,16]. The SEM and STEM micrographs revealed that an abundance of defects exist in the as deposited gold film and defect annihilation might be the main reason of the tensile stress increase in the present study.…”

“…In the limited regime (T < 125 C) [15,16], higher temperature can facilitate a series of thermally activated processes and would lead to a faster and more thorough recovery process. As the consequence, change of the residual stress due to recovery is much significant at higher temperature.…”

Incipient yielding behavior during indentation for gold thin films before and after annealing

“…The modulus of 115.3 GPa and Poisson's ratio of 0.37 might be expected for the gold, based on the 〈111〉 anisotropic values, i.e., the dominant texture of the gold films. 25,[32][33][34] The indentation of a single crystal has been studied, even for the case of highly anisotropic material. 35,36 These studies suggest that the Hill material property values (the average of the isostress and isostrain conditions) are reasonable estimates, even when indenting anisotropic single crystals.…”

“…After being cut to size, separate specimens were annealed at room temperature or 177°C for 4 h. The annealing temperatures are sufficiently low that the 20-nm-thick chromium layer, used to adhere the gold to the polycrystalline silicon underneath, was not observed to diffuse into the other materials. 25 A Nano DCM (MTS Systems Corp., Minneapolis, MN) was used to indent into the specimens with a diamond Berkovich tip at room temperature. When performed in "continuous stiffness" mode, 26 instrumented indentation can be used to obtain the hardness and modulus of a material at discrete instances (unloading events) throughout its thickness, according to the Oliver-Pharr method.…”