  We report on the epitaxial growth and surface structure of infinite-layer
cuprate Sr1-xNdxCuO2 films on SrTiO3(001) substrates by combining
ozone-assisted molecular beam epitaxy and in situ scanning tunneling
microscopy. Careful substrate temperature and flux control has been used to
achieve single-phase, stoichiometric, and c-axis oriented films. The surface of
the films is usually characterized by a mixed CuO2 surface and gridlike
superstructure. The superstructure exhibits a periodicity of 3.47 nm that
corresponds to a coincidence lattice between the overlayer peroxide SrO2 and
underlying CuO2 plane, and gives rise to a conductance spectrum that is
distinct from the Mott-Hubbard band structure of CuO2. At a higher Nd
composition x > 0.1, a (2 x 2) surface characteristic of the hole-doped CuO2
emerges, which we ascribe to the intake of apical oxygens in the intervening Sr
planes.
