Effect of isotope disorder on the Raman spectra of cubic boron arsenide
Akash Rai, Sheng Li, Hanlin Wu, Bing Lv, David G. Cahill
Abstract
Boron arsenide $(c\text{\ensuremath{-}}\mathrm{BAs})$ is at the forefront of research on ultrahigh thermal conductivity materials. We present a Raman scattering study of isotopically tailored cubic boron arsenide single crystals for 11 isotopic compositions spanning the range from nearly pure $c\text{\ensuremath{-}}^{10}\mathrm{BAs}$ to nearly pure $c\text{\ensuremath{-}}^{11}\mathrm{BAs}$. Our results provide insights on the effects of strong mass disorder on optical phonons and the appearance of two-mode behavior in the Raman spectra of mixed crystals. Strong isotope disorder also relaxes the one-phonon Raman selection rules, resulting in disorder-activated Raman scattering by acoustic phonons.