  Zn and Ni impurities in the hole-doped high-temperature superconductors are
known to have strong effects on thermodynamic and transport properties. A
recent scanning tunneling microscope study of Zn-doped Bi2212 (Pan et al.,
Nature 403, 746 (2000)) has provided high-resolution images of the local
density of states around non-magnetic impurities in d-wave superconductors.
These pictures contain detailed information about the spinor wave functions
u(r) and v(r) of bound states with energy E_0 \sim Delta/30, centered at the
Zn-sites. We show that this type of wave function follows from the solutions of
the Bogoliubov-de Gennes equations for d-wave superconductors.
