Effective absorption correction for energy dispersive X‐ray mapping in a scanning transmission electron microscope: analysing the local indium distribution in rough samples of InGaN alloy layers

Abstract

SummaryWe have applied our previous method of self-consistent k*-factors for absorption correction in energy-dispersive X-ray spectroscopy to quantify the indium content in X-ray maps of thick compound InGaN layers. The method allows us to quantify the indium concentration without measuring the sample thickness, density or beam current, and works even if there is a drastic local thickness change due to sample roughness or preferential thinning. The method is shown to select, pointby-point in a two-dimensional spectrum image or map, the k*-factor from the local Ga K/L intensity ratio that is most appropriate for the corresponding sample geometry, demonstrating it is not the sample thickness measured along the electron beam direction but the optical path length the X-rays have to travel through the sample that is relevant for the absorption correction.

Self‐consistent absorption correction for quantifying very noisy X‐ray maps: group III nitride nanowires as an example

“…The In concentration correlated with the broad photoluminescence (PL) peak in the as‐grown sample would then indicate values of x = 0.175 ± 0.06, respectively, which correlates well with our above quantification from EDXS. The blue shift of the nanowire PL spectrum, however, cannot be explained by strain relaxation (Wang et al ., ) but probably results from a reduction of the piezoelectric effect after strain relaxation (Peng et al ., ; Bochkateva et al ., ).…”

“…In ADF imaging regions thicker or richer in heavy elements such as indium appear brighter (Wang et al ., ), whereas regions thinner or where lighter elements like aluminium are enriched appear darker. Hence, in Figure the multiple thin bright layers can tentatively be identified as InGaN, the thick darker layers as AlGaN.…”