Figure 1

Representative IXS spectra of $h$-BN for the TA branch along the [110] direction, polarized along the $c$ axis. The symbols represent the IXS data whereas the solid (red) curves display the least-squares fit. The corresponding portion of the phonon dispersion is shown in the inset, where $q$ is given in reciprocal lattice units (r.l.u.). The IXS data of the upper branch (ZA) were obtained for $(qq3)$ total momentum transfers.Reuse & Permissions

Figure 2

(a) Phonon dispersion relations of $h$-BN along the main symmetry directions. The open (red) circles display modes polarized in the hexagonal plane whereas the solid (blue) circles correspond to modes polarized along the $c$ axis. The solid curves represent the calculated phonon dispersion and infrared [22] and Raman [14, 21, 22] data at the $\Gamma$ point are displayed by open (magenta) and solid (green) diamonds. (b) Calculated phonon dispersions of a monolayer of $h$-BN deposited on 3 layers of Ni (solid lines) compared to the EELS data from Ref. 9 (red open circles). Note that in the experiment only vibrational modes involving boron or nitrogen atoms were detected while in the calculations also the vibrational modes of the Ni substrate are included.Reuse & Permissions

Figure 3

Comparison of the second-order Raman spectrum of $h$-BN (solid, black) reported in Ref. 14 with our calculations for the one-phonon (dotted, blue line) and two-phonon (dashed, red line) DOS. The energy axis of the one-phonon DOS has been multiplied by a factor 2, in the same fashion as in Ref. 14. The most relevant features of the experimental spectrum are labeled, and their energies compared with IXS data and calculations in Table .Reuse & Permissions