ABSTRACT
Transmission electron microscopy (TEM) dark-field imaging is sensitive to the chemical and structural properties of strained quantum heterostructures. Quantitative chemical analysis in TEM can be carried out by using various techniques such as high resolution TEM, energy dispersive spectroscopy (EDS), electron energy-loss spectroscopy (EELS), analysis of thickness fringes or convergent beam electron diffraction. TEM wedge shaped samples were prepared by mechanical thinning and Ar+ ion milling such that the zone axis is parallel to the electron beam. EDS and EELS are limited by channelling effects, long acquisition times and related high irradiation doses. The chemical contrast remains constant for a series of InGaAs layers with constant composition and increasing layer thickness. Changing the sign of the diffraction vector reverses the position of the contrast to the other side of the InGaAs layer. The position of the minimum of the strain contrast moves away from the layer when the strain field increased.
