  We present an angle-resolved photoelectron spectroscopy study of
YBa2Cu3O7-delta films in situ grown by pulsed laser deposition. We have
successfully produced underdoped surfaces with ordered oxygen vacancies within
the CuO chains resulting in a clear ortho-II band folding of the Fermi surface.
This indicates that order within the CuO chains affects the electronic
properties of the CuO2 planes. Our results highlight the importance of having
not only the correct surface carrier concentration, but also a very well
ordered and clean surface in order that photoemission data on this compound be
representative of the bulk.
