Fejfar, A.; Hývl, M.; Vetushka, A.; Pikna, P.; Hájková, Z.; Ledinský, M.; Kocka, J.; Klapetek, P.; Marek, A.; Mašková, C.; Vyskocil, J.; Merkel, J.; Becker, C.; Itoh, T.; Misra, S.; Foldyna, M.; Yu, L.; Roca i Cabarrocas, P.: Correlative microscopy of radial junction nanowire solar cells using nanoindent position markers. Solar Energy Materials and Solar Cells 135 (2015), p. 106–112
Radial junction solar cells with only ~100 nm thin amorphous Si absorber layer deposited on Si nanowires can be prepared by a relatively simple and low-cost thin film technology. Metal assisted Si nanowire growth leads to a disorder in nanowire orientations, lengths and shapes, which is then preserved by the conformal absorber layer. Interestingly high conversion efficiencies are reached in spite of the disorder. In this contribution we describe microscopic methods aiming at exploring the role of structural disorder on the local electronic properties of radial junction cells. A method for locating the same nanostructure in different microscopes, using the nanoindentation marks for orientation on the sample, is described. Indents can be easily located by optical microscopy, scanning electron microscopes or scanning probe microscopes. Groups of three indents arranged in triangles can serve as coordinate systems for triangulation on samples, enabling correlative microscopy even in instruments which were not designed for it. This approach also enables localization of the same positions on samples even after repeated mounting in various microscopes with a precision better than 50 nm. This is possible even on samples without any structural features, as demonstrated for the flat silicon thin films prepared by solid phase crystallization, for which we have correlated crystallographic maps from electron backscattering diffraction and conductivity maps by atomic force microscopy. The technique allows observing the same locations before and after technological steps, as shown for the hot wire chemical vapour deposition of carbon nanowalls.