Atom probe contribution to the caracterisation of CIGSe grain boundaries

Atom Probe Tomography (APT) technique is the only nano-scale-sensitive analytic tool allowing 3D chemical analysis with atomic scale resolution. For long restricted to conductive samples, implementation of ultra fast laser pulsing extend now the field of applications to the analysis of semiconductor materials. In the present study, high efficiency Cu(In, Ga)Se₂ (CIGSe) thin films have been investigated by APT in order to solve interrogations about grain boundaries (GBs) composition. The analyzed CIGSe layers have been grown by co-evaporation on Mo-coated soda-lime glass substrates following the standard 3-stage process and the atom probe tips prepared using a focused ion beam (FIB) equipment. In order to ensure the presence of GB in the small APT investigated volume, location and misorientation of GBs have been determined by electron backscattering scanning diffraction (EBSD) and one GB interface placed close to the edge of the tip. From APT analyses, spatial distribution of CIGSe elements can be imaged at atomic scale; particular attention has been devoted to the composition profiles at the vicinity of the CIGSe GB interface. New results are compared with usual CIGSe GB passivation models.