Substrate Sensitive Mid-Infrared Photoresponse in Graphene
  We report mid-infrared photocurrent spectra of graphene nanoribbon arrays on SiO2 dielectrics showing dual signatures of the substrate interaction. First, hybrid polaritonic modes of graphene plasmons and dielectric surface polar phonons produce a thermal photocurrent in graphene with spectral features that are tunable by gate voltage, nanoribbon width, and light polarization. Secondly, phonon-polaritons associated with the substrate are excited, which indirectly heat up the graphene leading to a graphene photocurrent with fixed spectral features. Models for other commonly used substrates show that the responsivity of graphene infrared photodetectors can be tailored to specific mid-IR frequency bands by the choice of the substrate. 
Marcus Freitag, Tony Low, Luis Martin-Moreno, Wenjuan Zhu, Francisco   Guinea, and Phaedon Avouris
cond-mat.mtrl-sci cond-mat.mes-hall