  Polar phonons can induce electric fields in an adjacent layer, whether
non-polar or polar, producing remote phonon scattering of electrons. Treatment
of remote phonon scattering has been based on the dielectric continuum model
which takes only the electrical boundary conditions into account. We show that
crystals whose polar modes satisfy both mechanical and electric boundary
conditions cannot introduce remote phonon effects in the absence of dispersion.
Further, even in the presence of dispersion, remote phonon effects are
negligible, as a consequence of the necessity of satisfying mechanical boundary
conditions.
