  We have used a scanning tunneling microscope to demonstrate that a single
CuO_2 plane can form a stable and atomically ordered layer at the surface of
Bi_2Sr_2CaCu_2O_{8+delta}. In contrast to previous studies on high-T_c
surfaces, the CuO_2-terminated surface exhibits a strongly suppressed tunneling
conductance at low voltages. We consider a number of different explanations for
this phenomena and propose that it may be caused by how the orbital symmetry of
the CuO_2 plane's electronic states affects the tunneling process.
