MBE preparation and in-situ characterization of FeTe thin fims

Within the family of Fe based superconductors, Fe chalcogenides have received particular attention due to their simple crystal structure. Fe_1+yTe, which is not superconducting, has been studied extensively in bulk form and, more recently, some efforts have been made regarding the synthesis of thin films, resorting to pulsed laser deposition and molecular beam epitaxy (MBE). Here we report the results of Fe_1+yTe thin fims grown by means of MBE under Te-limited growth conditions. We found that epitaxial layer-by-layer growth is possible for a wide range of excess Fe values, wider than expected from what is known from studies on the bulk material. Using x-ray magnetic circular dichroism spectroscopy at the Fe L_2,3 and Te M_4,5 edges, we observed that fims with high excess Fe contain ferromagnetic clusters while films with lower excess Fe remain nonmagnetic. Moreover, x-ray absorption spectroscopy showed that it is possible to obtain fims with very similar electronic structure as that of a high-quality bulk single crystal Fe_1.14Te. Our results suggest that MBE with Te-limited growth may provide an opportunity to synthesize FeTe films with smaller amounts of excess Fe as to come closer to a possible superconducting phase.