Molecular beam epitaxy preparation and <i>in situ</i> characterization of FeTe thin films
V. M. Pereira, C. N. Wu, C. E. Liu, S.-C. Liao, C. F. Chang, C.-Y. Kuo, C. Koz, U. Schwarz, H.-J. Lin, C. T. Chen, L. H. Tjeng, S. G. Altendorf
Abstract
We have synthesized ${\mathrm{Fe}}_{1+y}\mathrm{Te}$ thin films by means of molecular beam epitaxy (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 films 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 films with very similar electronic structure as that of a high quality bulk single crystal ${\mathrm{Fe}}_{1.14}\mathrm{Te}$. 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.