Fig. 1

(Color online) a STEM-HAADF image of FeSe\(_{0.06}\)S\(_{0.94}\) with the incident beam along the [001] direction. The [001] projection of the structure model is illustrated with yellow and green spheres representing Fe and Se/S atom, respectively. Scale bar 1nm. b Intensity profile (black circles in top) from the white dash scan line shown in (a). Two other intensity profiles from images of FeSe\(_{0.31}\)S\(_{0.69}\) and FeSe\(_{0.82}\)S\(_{0.18}\) are shown in green and red circles, respectively. The solid lines are the fitted curves based on Gaussian function to obtain the full width at half maximum (FWHM) of Fe and Se/S columns. c Normalized FWHM of Se/S columns (FWHM\(_{\text {Se/S}}\)/FWHM\(_{\text {Fe}}\)) as a function to S concentration x in FeSe\(_{1-x}\)S\(_x\). d, e Temperature dependence of in-plane resistivity \(\rho\)(T) for FeSe\(_{1-x}\)S\(_x\). Inset in d shows the \(d\rho /dT\) versus T for the indicated samples. Inset in e shows the resistivity upturn region in log\(_{10}T\) scale for x = 0.4. f, g The enlargement of superconducting transitions at low temperatures