Fig. 3: Nano-XRF and STEM–EDS analysis of lamella 1.
a–e, Elemental distribution of the absorber metals In (a), Ga (b), Ag (d), Cu (e) and Rb (c), as obtained via nano-XRF on lamella 1 from Fig. 2c. XRF peak fitting was conducted by using the dedicated software PyMca66. To account for the small thickness variations across the lamella (XRF intensityIscales with sample volume), the signal intensity of the absorber metal elements was corrected at each pixel (that is, position) by multiplying it with an individual correction factor mcor(pixel) = ISe,Max/ISe(pixel) obtained from the Se distribution map. Here, ISe,Max is the highest intensity of the Se map and ISe(pixel) is the intensity measured at each corresponding pixel. This is a valid first approximation as long as the selenium concentration can be assumed to be constant everywhere in the absorber (that is, 1:1:2 stoichiometry). Consequently, the Se distribution map is not shown. f, Corresponding STEM-BF image. g–k, Corresponding maps of a smaller area (‘Pos1.1’, indicated by a dashed whit box) derived from STEM–EDS for In (g), Ga (h), Rb (i), Ag (j) and Cu (k). The colour code refers to the atomic concentrations in at.% in case of the EDS analysis and to the density (in ng cm−2) in case of the nano-XRF analysis, ranging from the corresponding minimum (Min) to the maximum (Max) values. The scale bar is valid for all images.
