Info

f

Figure 27. Transition between Cu and CujO. Layered structure tilted by 2°. (a) Unfiltered image. (b) PS of the unfiltered image. (c) Filtered image. (d) PS of c. (e) Filtered image with reflection e only. (f) Filtered image with reflection f only.

Figure 26. HRTEM image (a) of a Ag cylinder deposited on NaCl (100). (b) Detail. (c) PS. Reprinted with permission from [47], N. Nepi-jko et al., Chem. Phys. Chem. 3, 140 (2000). © 2000, Wiley-VCH.

Figure 27. Transition between Cu and CujO. Layered structure tilted by 2°. (a) Unfiltered image. (b) PS of the unfiltered image. (c) Filtered image. (d) PS of c. (e) Filtered image with reflection e only. (f) Filtered image with reflection f only.

Figure 28. Computer simulation consisting of two layers tilted by 2° with different lattice constants (a, b) to explain Figure 27. (c) Sum of layers a and b.

are Fourier-filtered images with a single pair of reflections e and f, respectively. In Figure 27c moiré fringes are observed, whereas the lattice lines in both images e and f are undisturbed over the total region of the particle. It is concluded that there is a layered structure of the two different lattices causing the moiré fringes. The small deformation of the lattices and their distortion must be introduced to fit the different layers to each other. An optical model is shown in Figure 28.

Figures 29 and 30 show computer simulations of cuprite (top) and experimental images together with PS for preparations without O2 but after air exposure for 100 h. In Figure 29 cuprite is shown for a cluster in the [110] orientation. The orientation of the cluster in Figure 30 is [112]. No splitting of the reflections is observed. This means that the oxidation process for cuprite is terminated.

Figures 31 and 32 also show cuprite clusters in the [001] and [111] orientations. The preparation was performed with 2 x 10-3 mbar O2 partial pressure and after 100 h of air exposure. There is also no splitting of reflections present, which means that the oxidation process is finished.

Figure 33 shows the image of a cluster prepared with less than 10-3 mbar partial pressure of oxygen and after air exposure for 114 h. The splitting of the reflections indicates a transitional state between CuO and Cu2O. Figure 33c and

0 0

Post a comment