Study of outermost surface lavers of organic solids by penning ionization electron spectroscopy

Abstract

Penning ionization electron spectroscopy (PIES) applied to the surface of organic solids such as benzene, biphenyl, naphthacene (tetracene), pentacene, and Fe-phthalocyanine is discussed. To show the specific character of PIES, some results on gas-phase molecules are first described. It is pointed out that molecular PIES provides direct information on the spatial electron distribution of individual molecular Orbitals. If PIES is employed for the study of a solid surface, (i) the outermost surface layer is selectively probed, and (ii) the electron distribution of individual orbitals in the local area outside the surface can be studied. These characteristics of surface PIES can be applied to observe the changes in the molecular orientation and the electronic state of the outermost surface layer during the epitaxial growth and the amorphous-crystal transition of organic films. The change in the structure of monolayer films, and chemical reactions that take place on the outermost surface layer can also be probed by PIES.