STM images of sub-surface Mn atoms in GaAs: evidence of hybridization of   surface and impurity states
  We prove that scanning tunneling microscopy (STM) images of sub-surface Mn atoms in GaAs are formed by hybridization of the impurity state with intrinsic surface states. They cannot be interpreted in terms of bulk-impurity wavefunction imaging. High atomic resolution images obtained using a low-temperature apparatus are compared with advanced, parameter-free tight-binding simulations accounting for both the buckled (110) surface and vacuum electronic properties. 
J.-M. Jancu, J.-Ch. Girard, M. Nestoklon, A. Lemaitre, F. Glas, Z.Z.   Wang