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The dielectric constant of TCNQ single crystals as deduced by reflection electron energy loss spectroscopy

Published online by Cambridge University Press:  03 March 2011

G. Mondio
Affiliation:
Istituto di Struttura della Materia dell'Universitá di Messina and Centro Siciliano per le Ricerche Atmosferiche e di Fisica dell'Ambiente, Salita Sperone 31, 98166 S. Agata, Messina, Italy
F. Neri
Affiliation:
Istituto di Struttura della Materia dell'Universitá di Messina, Salita Sperone 31, 98166 S. Agata, Messina, Italy
G. Curró
Affiliation:
Istituto di Struttura della Materia dell'Universitá di Messina, Salita Sperone 31, 98166 S. Agata, Messina, Italy
S. Patané
Affiliation:
Istituto di Struttura della Materia dell'Universitá di Messina, Salita Sperone 31, 98166 S. Agata, Messina, Italy
G. Compagnini
Affiliation:
Dipartimento di Fisica dell'Universitá di Catania, Corso Italia 57, 95129 Catania, Italy
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Abstract

The dielectric constant of tetracyanoquinodimethane (TCNQ) single crystals has been obtained by reflection electron energy loss spectroscopy (REELS) over the 0–60 eV energy range, using primary electron energies ranging from 0.5 to 1.5 keV at an incidence angle of about 40°. A self-consistent method is discussed concerning the evaluation of the surface and bulk contributions to the loss spectra. As a result, for the first time, the Im(−1/∊) function and the dielectric constant of TCNQ have been deduced in such a wide energy range. According to the results obtained by other authors, the low-energy loss spectral profile is characterized by two main structures ascribed to the π → π dipole-allowed transitions located at about 3.5 and 6.5 eV while, at higher energy loss, the π + σ plasmon, centered at about 21.5 eV, dominates the spectrum. The differences among the spectra taken at different primary energies are interpreted as due only to surface effects, more evident in the low-energy-loss spectral region. The results are in good agreement with those obtained by recent transmission-mode (TEELS) experiments.

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Articles
Copyright
Copyright © Materials Research Society 1993

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References

REFERENCES

1Ohno, Y., Phys. Rev. B 39, 8209 (1989).CrossRefGoogle Scholar
2Raether, H., Excitation of Plasmons and Interband Transitions by Electrons-Springer Tracts in Modern Physics (Springer-Verlag, Berlin, 1980), Vol. 88.Google Scholar
3Netzer, F. P., Matthew, J. A., and Bertel, E., in Spectroscopy of Surfaces, edited by Clark, R. J. H. and Hester, R. E. (John Wiley & Sons, Ltd., New York, 1988), Chap. VI, pp. 283376.Google Scholar
4Chiarello, G., Colavita, E., De Crescenzi, M., and Nannarone, S., Phys. Rev. B 29, 4878 (1984).CrossRefGoogle Scholar
5Ingram, J. C., Nebesny, K. W., and Pemberton, J. E., Appl. Surf.Sci. 44, 279 (1990).CrossRefGoogle Scholar
6Wehenkel, C. and Gauthe, B., Phys. Status Solidi B 64, 515 (1974).CrossRefGoogle Scholar
7Wehenkel, C., Le Journal de Physique 36, 199 (1975).CrossRefGoogle Scholar
8Egerton, R. F. and Crozier, P. A., Scanning Microscopy Suppl. 2, 245 (1988).Google Scholar
9Egerton, R. F., in Electron Energy Loss Spectroscopy in the Electron Microscope (Plenum Press, New York, 1986).Google Scholar
10Mondio, G., Neri, F., Patane, S., Arena, A., Marietta, G., and Iacona, F., Thin Solid Films 207, 313 (1992).CrossRefGoogle Scholar
11Mondio, G., Neri, F., Curro, G., Duo, L., and Wandelt, K., Physica Scripta T 41, 153 (1992).CrossRefGoogle Scholar
12Weber, W. H. and Webb, M. B., Phys. Rev. 177, 1103 (1969).CrossRefGoogle Scholar
13Tougaard, S. and Kraaer, J., Phys. Rev. 43, 1651 (1991).CrossRefGoogle Scholar
14Arakawa, E. T., Williams, M. W., Ashley, J. C., and Painter, L. R., J. Appl. Phys. 52, 3579 (1981).CrossRefGoogle Scholar
15Ritsko, J. J., Brillson, L. J., and Sandman, D. J., Solid State Commun. 24, 109 (1977).CrossRefGoogle Scholar
16Ritsko, J. J., Lipari, N. O., Gibbons, P. C., Schnatterly, S. E., Fields, J. R., and Devaty, R., Phys. Rev. Lett. 36, 210 (1976).CrossRefGoogle Scholar
17Burkert, M., Link, R., Puhlmann, N., and Vollmann, W., Phys. Status Solidi B 145, K121 (1988).Google Scholar
18Girlanda, R., Martino, G., Mezzasalma, A. M., Mondio, G., Perillo, P., and Saitta, G., II Nuovo Cimento 7, 469 (1986).CrossRefGoogle Scholar
19Yubero, F. and Tougaard, S., Phys. Rev. B 46, 2486 (1992).CrossRefGoogle Scholar