  We study the free energies of heavy quarks calculated from Polyakov loop
correlation functions in full 2-flavour QCD using the p4-improved staggered
fermion action. A small but finite Baryon number density is included via Taylor
expansion of the fermion determinant in the Baryo-chemical potential mu. For
temperatures above Tc we extract Debye screening masses from the large distance
behaviour of the free energies and compare their mu-dependence to perturbative
results.
