Nanoindentation of high-purity vapor deposited lithium films: The elastic modulus

Nanoindentation has been used to measure the elastic modulus of 5 and 18 μm thick high-purity vapor deposited polycrystalline lithium films at 31 °C. Over indentation depths ranging from 150 to 1100 nm, the modulus is found to vary with film thickness from 9.8 GPa ± 11.9% to 8.2 GPa ± 14.5%. These results are well within the range of lithium’s orientation dependent elastic modulus, which spans approximately 3.1 to 21.4 GPa. The measured values may also indicate (111) and (100) texture for the 5 and 18 μm thick films, respectively. The potential effects of pileup and surface contamination are found to be negligible if any at all. Small but discernible changes in damping capability near the free surface may provide insight into the subsurface defect structure and the potential for localized heating. Numerous experimental challenges are addressed and key metrics are used to validate the measured elastic modulus.