Figure 6.

FEBID-based electric AFM modes. (a–d) show height (left) and Kelvin force microscopy (KFM) (right) images of SiGe quantum ring, performed with commercial, Pt–Ir coated AFM tips (upper row) and Pt–C nano-pillar modified tips (lower row). While the resolution improvement is evident by the more circular feature shapes, the KFM images reveal many more details, as representatively indicated by the blue and white rings. Adapted and reprinted from Chen et al., IEEE 2012 [94]. (e,f) show TEM micrographs of the tip region of a Pt-based FEBID nano-pillar after deposition (e) and after full purification using e-beam assisted carbon removal in H₂O atmospheres at room temperature [44,90]. As evident, the pillar gets smaller in width, which entails a slight reduction of the apex radius in the sub-10 nm regime. The larger Pt crystals and the dense packing are evident, while the carbon-free character was confirmed by scanning transmission electron microscopy-based electron energy loss spectroscopy (STEM-EELS) measurements. Such highly conductive tips are then used for C-AFM measurements, as representatively shown in (g) and (h). The scheme below shows the layer setup, consisting of Au paths separated by Al₂O₃ lines on Si. The advantage of the high aspect ratio pillar is an accurate edge profiling in the height image (g), while the current signal (skin overlay in (h)) allows for the identification of non-conductive regions of thick (red circles) and nanometer thin (purple rings) impurity layers. Image copyright GETec Microscopy 2019 [95].