We propose using short-period superlattices as substrates to control the vi
brational relaxation dynamics of adsorbate overlayers. The mass modulation
of superlattices creates both band gaps and large spectral enhancements in
the phonon density of states. These modifications can dramatically alter th
e coupling between vibrational modes of the adsorbate overlayer and the sub
strate lattice, thereby significantly affecting the lifetime of adsorbate m
odes.