from a single target in a partial pressure 1 u00d7 10 u2212 5 t of sulfur onto a glass substrate the film was u02dc 200 nm thick and polycrystalline it exhibited the expected cubic pyrite crystal structure as indicated by x ray diffractometry the sample was transferred to an evaporation chamber without removal to atmosphere and a 40 nm thick layer of epitaxial zns was deposited by thermal evaporation a sketch of this sample is shown in fig1 transferring the sample between deposition chambers under vacuum or without removal to air avoids oxidation and contamination of the fes 2 surface in other embodiments high substrate temperature deposition of fes 2 may be carried out by sputtering from a multi component target to a high temperature substrate e g ts 400 u00b0 c and sulfurdizing under flowing h 2 s e g at 500 u00b0 c for 5 hours all vacuum deposited fabrication is preferred according to some aspects of the invention initial x ray photoelectron spectroscopy xps results for this sample were obtained and compared to results for bare fes 2 and films with zno and sio 2 encapsulation layers the encapsulation layers were removed in steps inside an ultra high vacuum chamber with an ion beam and xps scans were carried out after each removal step the results shown in.