Scanning transmission electron microscopy strain measurement from millisecond frames of a direct electron charge coupled device

Abstract

A high-speed direct electron detection system is introduced to the field of transmission electron microscopy and applied to strain measurements in semiconductor nanostructures. In particular, a focused electron probe with a diameter of 0.5 nm was scanned over a fourfold quantum layer stack with alternating compressive and tensile strain and diffracted discs have been recorded on a scintillator-free direct electron detector with a frame time of 1 ms. We show that the applied algorithms can accurately detect Bragg beam positions despite a significant point spread each 300 kV electron causes during detection on the scintillator-free camera. For millisecond exposures, we find that strain can be measured with a precision of 1.3 × 10 - 3, enabling, e.g., strain mapping in a 100 × 100 nm 2 region with 0.5 nm resolution in 40 s. © 2012 American Institute of Physics.