Brillouin scattering of zero-valent Au-, Cu-, Ag-intercalated hexagonal boron nitride

Brillouin laser light scattering spectra of hexagonal boron nitride were measured in its pure form as well as with zero-valent copper, gold, and silver intercalants including one sample co-intercalated with copper and silver. Up to four of the five independent elastic stiffness constants were determined along with the associated sound velocities for the five distinct materials. Intercalation radically changes the optical color of the boron nitride. Brillouin scattering measurements show almost no change in the c₃₃ out-of-plane elastic stiffness and the c₆₆ in-plane shear modulus, while the c₁₁ in-plane stiffness increases by roughly 100 GPa with copper-silver co-intercalation and decreases by roughly 30 GPa with silver intercalation. The results lie within the broad range of literature values for c₁₁, c₃₃, and c₄₄ but differ substantially for c₆₆.