LAUSR

We report on the epitaxial growth and surface structure of infinite-layer cuprate ${\mathrm{Sr}}_{1\ensuremath{-}x}{\mathrm{Nd}}_{x}{\mathrm{CuO}}_{2}$ films on ${\mathrm{SrTiO}}_{3}$(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 ${\mathrm{CuO}}_{2}$ surface and gridlike superstructure. The superstructure exhibits a periodicity of 3.47 nm that corresponds to a coincidence lattice between the overlayer peroxide ${\mathrm{SrO}}_{2}$ and underlying ${\mathrm{CuO}}_{2}$ plane, and gives rise to a conductance spectrum that is distinct from the Mott-Hubbard band structure of ${\mathrm{CuO}}_{2}$. At a higher Nd composition $xg0.1$, a $(2\ifmmode\times\else\texttimes\fi{}2)$ surface characteristic of the hole-doped ${\mathrm{CuO}}_{2}$ emerges, which we ascribe to the intake of apical oxygens in the intervening Sr planes.