Fig. 1: Basic atomic-scale characterization.
From: Direct visualization of stacking-selective self-intercalation in epitaxial Nb1+xSe2 films
a Schematic of the hybrid pulsed laser deposition (hPLD) growth of Nb1+xSe2 thin films. b, c Reflection high-energy electron diffraction patterns at different stages of the growth: (b) sapphire substrate before deposition and (c) Nb1+xSe2 film after 17,700 laser pulses; direction [1–100]; electron energy 10 keV. d Atomically resolved scanning tunneling microscopy topographic image; setpoint −125 mV, 50 pA. The bright spots correspond to surface Se atoms. e Crystal structure of a NbSe2 layer shown in two perspectives. The letter “c” labels the top-layer Se atoms (shaded in orange) seen in (c). The lines marked by the letters “f” and “g” depict the view along which the cross-sections in (f) and (g) are seen. f, g High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images of the cross-section of a Nb1+xSe2 (x ~ 0.29) thin film viewed along the [1–100] direction of the sapphire substrate, corresponding to two distinct film domains with 30° rotation (cuts shown in e). The insets show intralayer lattice structure and their structural models. h–j A close-up HAADF-STEM image revealing the Nb1+xSe2 lattice structure (h) and the calculated interlayer spacing (i) and Se-Nb-Se angle (j) averaged over each NbSe2 layer, as illustrated by the insets. The error bars correspond to the standard deviations of the Se-Nb-Se angles in each NbSe2 layer.
