Figure 5.

Topography (a, b, c) and current (d, e, f) maps obtained on a polycrystalline 5-nm-thick HfO₂ sample in different environments: air (a, d), high-vacuum (b, e), and ultra-high-vacuum (UHV)--(c, f). In current images, white areas correspond to regions with a current above 0.2 pA, while the black areas show a current lower than the noise level.