Driving forces for texture transformation in thin Ag films

Abstract

The well-known thickness-dependent (111)-to-(100) texture transformation in thin FCC films is usually attributed to a competition between interface and strain energies. In this model, thin films retain their (111) texture due to the lower energy of the (111) interface, while thick films transform to (100) due to the lower stiffness and thus strain energy of a (100) film. However, recent work has called this model into question, suggesting that neither the stress nor the interface energy play a dominant role in texture transformation. We investigated the driving forces involved in this transformation by using a bulge test apparatus to induce different stresses in thin Ag films under identical annealing conditions. In situ synchrotron XRD measurements show the change in texture during annealing, and reveal that applied stresses have no effect on the transformation. Stress analysis shows that differences in driving forces for texture transformation due to applied bulge pressure were significant (≈200 kJ/m 3 ), suggesting that a different, much larger driving force must be responsible. Reduction in defect energy has been proposed as an alternative. However, vacancy and dislocation densities must be exceptionally high to significantly exceed the strain energy and do not provide obvious orientation selection © 2016. This manuscript version is made available under the Elsevier user license http://www.elsevier.com/open-access/userlicense/1.0/ mechanisms. Nanotwins in reported densities are shown to provide greater driving force (≈ 1000 kJ/m 3 ) and may account for orientation selection. The large difference between the calculated strain and defect energies and the driving force for grain growth (21,100 kJ/m 3 ) casts doubt on the applicability of a simple thermodynamic model of texture transformation.

Initiation and stagnation of room temperature grain coarsening in cyclically strained gold films

“…To support this statement one can mention the texture transition effect leading to the growth of (100) grains at the expense of (111) grains in Cu and Ag thin films at relatively low homologous temperatures [39,40]. Although the exact nature of the driving force is still under discussion [40], it is a clear example of GB migration and selective grain growth due to a thermodynamic driving force. Another prominent example of grain growth induced by a specific driving force is texture transition under ion beam irradiation.…”

Limitations of Thermal Stability Analysis via In-Situ TEM/Heating Experiments

“…Images of rapidly grown grains near stagnant grains are shown in Figures 1 and 2. The secondary grain growth is also associated with the development of the sample texture [31][32][33] due to the selective rapid grain growth of certain orientations as mentioned earlier. This is also demonstrated in Figure 2b for the thin area heated in-situ when compared to the ex-situ bulk material results (Figure 2c) or the thick region of the in-situ results (Figure 2d).…”

<i>Ab-Initio</i> Study of (111) to (001) Texture Transformation in Ag Thin Films

“…This result is consistent with the previously reported experimental observation that the strain in Ag thin films varies from compressive to tensile as the texture transforms from (111) to (001). 8,9)…”