  We report investigation on Fe1+yTexSe1-x single crystals by using scanning
transmission electron microscopy (STEM) and electron energy loss spectroscopy
(EELS). Both nonsuperconducting samples with excess iron and superconducting
samples demonstrate nanoscale phase separation and chemical inhomogeneity of
Te/Se content, which we attribute to a miscibility gap. The line scan EELS
technique indicates ~20% or less fluctuation of Te concentration from the
nominal compositions.
