Elastic modulus films

Many materials deposited by CVD have a high elastic modulus and a low fracture toughness and are therefore affected by residual film stresses. 

Indentation has been used for over 100 years to determine hardness of materials [8J. For a given indenter geometry (e.g. spherical or pyramidal), hardness is determined by the ratio of the applied load to the projected area of contact, which was determined optically after indentation. For low loads and contacts with small dimensionality (e.g. when indenting thin films or composites), a new way to determine the contact size was needed. Depth-sensing nanoindentation [2] was developed to eliminate the need to visualize the indents, and resulted in the added capability of measuring properties like elastic modulus and creep. 

There are many experimental details to consider in nanoindentation, but the end result is that both hardness and elastic modulus can be determined relatively routinely on very small samples, including thin films and nanocomposites. What is more, the hardness measurement is quantitative and reproducible. A typical hardness-modulus-indentation depth curve is shown in Figure 5.22 for an Si(lOO) plane. 

Polyurethanes based on the HDI cyclic trimer show a rubberlike mechanical behavior. In fact, the Z1030/1072 and Z1031-H films show a low elastic modulus E, no yielding, and an ultimate, widely reversible, deformation beyond 100-150%, likely underestimated owing to the difficulty in assessing the ultimate properties of self-supported thin films. 

In the following, we calculate K and H for the model of polymer film in which part of the amorphous phase is connected in series with the crystalline phase and part in parallel (Fig. 10). The amorphous phase is characterized by a complex elastic modulus,... 

Fukada and Sakurai (1971) measured the temperature dependence of df3 and df2 for a drawn and polarized PVDF film (Fig. 30). The relaxational behavior is somewhat masked by the rapid monotonic increase with increasing temperature on account of the decrease in the elastic modulus. Details of the curves, however, seem to indicate that d has a maximum at relaxational temperatures and, in accordance with this, d" has a maximum and a succeeding minimum at these temperatures. 

The calculation of thermal stresses in functionally graded materials is already a relatively old topic (Yang et al., 2003). Two methods can be distinguished analytical methods and finite element methods. However, the complicating effect of the elastic modulus variation with the position severely limits the scope of problems that can be solved analytically. Therefore, the majority of the analytical work has been for FGM films or other simple structures (Becker et al., 2000). Analytical models have been developed for the calculation of thermal stresses for 1-D FGM symmetrical plates (Jung et al., 2003), non-... 

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