The sensitivity of electron scattering to sample temperature (T) as a function of the scattering angle in scanning transmission electron microscopy (STEM) is investigated. Thermal vibration of atoms in crystal lattice results in attenuated Bragg reflections and a diffuse background in electron diffraction patterns, which have direct implications on STEM images. The scattering intensities at higher angle are known to be dominated by thermal diffuse scattering (TDS) and the column intensity is expected to have a negative correlation with increasing T because of the disrupted channeling, but the T susceptivity of the scattering intensity at smaller angles is less known. Our experiment shows that the T dependency of annular averaged diffraction intensity inverts its sign two times outside the direct beam, and the T sensitivity varies significantly as a function of scattering angle. The intensity shows a positive correlation with increasing T at the low to intermediate angular ranges before it returns to the negative correlation at the higher angle range. A reasonable agreement is found between the experimental data and multislice simulation data. Absorptive model is used to provide theoretical insights into the observed trends. Similar inversions of T dependency of column intensities are also observed in experimental and simulated atomic-resolution STEM images. The findings provide an important implication to the precise quantification of local T at high spatial resolution by optimizing the collection angles in STEM.
Keywords: 4D STEM; PACBED Phonon; Temperature measurement; Thermal diffuse scattering; Thermal property.
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