Direct measurement of strain in a Ge island on Si(001)

We report on a direct measurement of the strain in a single Ge “quantum dot” island grown on Si by chemical vapor deposition. This transmission electron microscopy method is reliable: without the need for detailed modeling of the strain field, it measures the maximum in-plane displacement. Good agreement is found between the experimental value of $0.86±0.17%$ average strain and finite element simulations assuming pure Ge. Thus no evidence of significant alloying with Si is observed.