Silicon vibration amplitude determined by energy-filtered CBED

Abstract

The frozen phonon method was recently developed to include the effects of thermal vibrations in the multislice calculation. In this method, each atom in the simulated specimen is displaced by a random amount which follows a Gaussian distribution with a standard deviation equal to the atomic vibration amplitude. Convergent beam electron diffraction (CBED) patterns calculated by this technique contain Kikuchi bands and a thermal diffuse background which were matched quantitatively to experimental Si (100) CBED patterns for scattering angles up to the first order Laue Zone. In this paper, we report the measurement of the room temperature silicon vibration amplitude from comparison of energy filtered CBED with frozen phonon calculations.The energy filtered Si (100) patterns were obtained with a VG HB501A STEM in microdiffraction mode by fixing a convergent probe (7.5mrad half angle, probe size ≈ 40Å) on the specimen and scanning the post specimen electrons over a small axial collector aperture (1.6mrad).