Chemistry Reference
In-Depth Information
Figure 6.9. TMAFM image taken at ambient conditions of a TTF-TCNQ thin film
(thickness
m) grown on KCl(100), revealing its polycrystalline morphol-
ogy. Reprinted from
Surface Science
, Vol. 482-485, C. Rojas, J. Caro, M. Gri-
oni and J. Fraxedas,
Surface characterization of metallic molecular organic thin
films: tetrathiafulvalene tetracyanoquinodimetane
, 546-551, Copyright (2001),
with permission from Elsevier.
∼
1
µ
irradiation. In fact great care has to be taken to avoid photon-induced surface dam-
age by minimizing the exposure to the incident radiation, in particular when using
synchrotron light. The effect is demonstrated in Fig. 6.11, which shows spectra
taken at
k
F
. For a surface prepared immediately after cleavage of the crystal, an in-
tense peak is observed close to
E
F
(continuous line). After two hours of exposure to
VUV radiation its intensity strongly decreases and its peak position shifts by more
than 0.1 eV away from
E
F
(discontinuous line). However, the original spectrum is
recovered by taking data on another previously unexposed sample spot.
Let us now return to the Fermi liquid vs. Luttinger liquid competition. Figure
6.12 shows the negative second energy derivative of the photoemission intensity
displayed in Fig. 6.8, as a grey-scale plot in the
E
−
k
plane. This mathematical
procedure enhances the visibility of the spectral structures and helps to visualize
their dispersion. Also shown are DFT calculations of the bands using the GGA
(Sing
et al.
, 2003b). The comparison of experiment and theory reveals significant
