Elastodynamic properties of embedded amorphous carbon layer in diamond investigated by surface Brillouin scattering

Abstract

By combining ion implantation and annealing, it is possible to create electrical conducting channels buried beneath the surface of the diamond. Recent Seebeck measurements have suggested the existence of a coupling between conduction electrons in the channel and vibrational phonons from the matrix. In this paper, we study the dispersion of the lowest frequency surface acoustic modes, the Rayleigh mode, propagating from a buried amorphous channel in diamond by means of inelastic scattering of monochromatic light using surface Brillouin scattering at room temperature. Spectra were collected over a wide range of incidence angles on the uncoated and Al-coated diamond implanted and annealed surfaces. The Rayleigh mode at low frequency could be reproduced well for angles above 30° with the simulated spectra from Green's functions analysis which considered the entire layered structure (bulk diamond-graphitic buried channel-top diamond layer) which has not been compared in previous studies for angles below 50°. This is the first surface Brillouin study that used an Al coating on the diamond surface where the buried channel was created ≈293 nm below the diamond surface by He ion implantation. The Al coating was shown to increase the peak intensity of the Rayleigh with little impact on its frequencies. The speed of the surface Rayleigh wave of the buried channel was calculated to be ≈8000–9000 m/s from the experimental data for 30°–80° for the Al coated implanted diamond. The departure from theory for data measured for scattering angles below 30° still needs to be resolved.