Contribution of drifting carriers to the Casimir-Lifshitz and   Casimir-Polder interactions with semiconductor materials
  We develop a new theory for Casimir-Lifshitz and Casimir-Polder interactions with semiconductor surfaces that takes into account charge drift in the bulk material. The corresponding frequency-dependent dispersion relations describe a crossover between Lifshitz results for dielectrics and for good conductors. In the quasi-static limit, our calculated reflection amplitudes coincide with those recently computed to account for Debye screening in the thermal Lifshitz force with conducting surfaces with small density of carriers. 
Diego A. R. Dalvit and Steve K. Lamoreaux