High lateral resolution energy dispersive X-ray spectroscopy and cathodoluminescence on lamellae of CIGSe solar cells

Abstract

The spatial resolution of conventional measurement geometries for energy dispersive X-ray spectroscopy and cathodoluminescence is limited by the excitation volume. For Cu(In,Ga)Se 2 solar cells high acceleration voltages up to 30 kV are needed to excite the K-shell of the investigated elements. As a consequence, the expansion of the excitation volume is in the magnitude of the layer thickness. Hence, thin lamellae were prepared with a focused ion beam and thinned out to a specimen thickness down to 50 nm. As a result, the spatial resolution was increased up to 25 nm, because the excitation volume is limited by the thickness of the lamellae and in first approximation only depends on the diameter of the electron beam. Highly resolving EDS measurements were performed to determine the gallium profile in the Cu(In,Ga)Se 2 absorber and the expected behavior was verified. Furthermore, cathodoluminescence images were taken of the lamellae and the determined grain structure was compared with the structure measured via scanning transmission electron microscope.Index Terms -cathodoluminescence (CL), EDS, Cu(In,Ga)Se 2 (CIGS) , lamellae, photovoltaic, thin film solar cells.

Development of a shear‐force scanning near‐field cathodoluminescence microscope for characterization of nanostructures’ optical properties

“…Advanced collection systems based on confocal mirror optics (Narvaaez et al ., ) have allowed increasing the lateral resolution, but it remains in the order of hundreds of nanometres for typical operation conditions in scanning electron microscope (SEM)‐based systems (Chan et al ., ; Mohtashami et al ., ; Moseley et al ., ; Leto et al ., ). Increased resolution combined with hyperspectral imaging has been made available on STEM‐based systems (Kociak et al ., ,b; Schönherr et al ., ; Picher et al ., ), but the special sample preparation required for the TEM/STEM systems limit the size and the type of sample that can be imaged with this type of CL setup. For such CL techniques, even if the resolution has lately been improved for particular systems and operating conditions (Sapienza et al .,), the sensitivity remains an issue due to far‐field collection of the emitted photons.…”

“…Tel: +33(0)326051901; fax: +33(0)326051900; e-mail: michael.molinari@univ-reims.fr ley et al, 2014;Leto et al, 2015). Increased resolution combined with hyperspectral imaging has been made available on STEM-based systems (Kociak et al, 2011a,b;Schönherr et al, 2014;Picher et al, 2015), but the special sample preparation required for the TEM/STEM systems limit the size and the type of sample that can be imaged with this type of CL setup. For such CL techniques, even if the resolution has lately been improved for particular systems and operating conditions (Sapienza et al,2012), the sensitivity remains an issue due to far-field collection of the emitted photons.…”