Measuring the Thin Film Strain Tensor Near Aluminum Grain Boundaries via a New Image Processing Approach to CBED HOLZ Patterns

Abstract

AbstractHOLZ lines formed in a CBED pattern provide the most accurate means to measure a local strain tensor with high spatial resolution over mesoscopic length scales. With the advent of energy-filtering in a field-emission TEM, the precision of this measurement increases by filtering out the inelastically scattered electrons. This paper presents an alternate approach to obtaining the same increased precision by image processing of CBED patterns formed in a conventional LaB6 microscope. This technique results in the determination of the full strain tensor within ±0.01%. It is based on developing a Wiener filter for CBED patterns, deconvoluting the point spread function of the CCD camera, using the Hough transform to measure distances between HOLZ line intersections, and subtracting out an experimentally determined projector lens distortion. The present technique has been used to measure the strain tensor for the two types of grain boundaries found in MBE grown Al thin films on Si which have the mazed bicrystal microstructure.