Fig. 2: Real-space observation of self-organised periodic interstitial modulation near FeTe/CdTe interface.
From: Superconductivity and suppressed monoclinic distortion in FeTe films enabled by higher-order epitaxy
a Cross-sectional HAADF-STEM image near an FeTe/CdTe interface. The yellow, brown, and magenta spheres indicate Te, Fe, and Cd atoms, respectively. b Integrated-intensity profiles along the cut A and B indicated in a. The dots above the profile indicate the equilibrium position for each atom. The grey areas indicate the nearest sites where the interfacial ions approach most closely. The red arrows represent the interfacial interstitials. The vertical solid black lines represent peak position for the sites 2 and 4, showing a slight modulation from the equilibrium towards the nearest sites. c Wide-area HAADF-STEM image near an FeTe/CdTe interface. The red shaded region indicates the position of the periodic interstitials. The yellow arrows denote the period of modulation, which corresponds to 6 unit cells (UCs) of FeTe, which approximately equals to 5 UCs of CdTe. Areas labelled as FFT1 and FFT2 correspond to the regions where fast Fourier transformation (FFT) was performed. d FFT image taken within FFT1 in c. The blue, magenta, and red arrows indicate Bragg peaks for FeTe, CdTe, and the interfacial modulation, respectively. e FFT profiles integrated along Qc as a function of Qa divided by the wave number QFeTe, corresponding to a Bragg peak of FeTe (0 1 0). The red and black lines correspond to the results taken in FFT1 and FFT2, respectively. The blue, magenta, and red arrows are the same as d, while the grey arrows indicate harmonics of the interfacial modulation, which appear at fractions of QFeTe. f Top-view schematics of the 6 × 6 superlattice of the interfacial interstitials.
