Electronic structures of TPD/metal interfaces studied by photoemission andKelvin probe method

Citation
E. Ito et al., Electronic structures of TPD/metal interfaces studied by photoemission andKelvin probe method, APPL SURF S, 175, 2001, pp. 407-411
Citations number
11
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Apllied Physucs/Condensed Matter/Materiales Science","Material Science & Engineering
Journal title
APPLIED SURFACE SCIENCE
ISSN journal
0169-4332 → ACNP
Volume
175
Year of publication
2001
Pages
407 - 411
Database
ISI
SICI code
0169-4332(20010515)175:<407:ESOTIS>2.0.ZU;2-P
Abstract
Interfacial electronic structures for TPD/metal (Au, Ag, and Ca) systems we re investigated by Kelvin probe method (KP), ultraviolet photoemission spec troscopy (UPS), X-ray photoemission spectroscopy (XPS), and metastable atom electron spectroscopy (MAES). KP results showed that an abrupt vacuum leve l shift occurred right at the interface, and no further shift was observed by further deposition of TPD up to the thickness of about 100 nm. Similar a brupt shift was also observed from the onset of the lower kinetic electron energy in the UPS spectra. These results suggest that band bending does not occur in the TPD/metal interface. From the MAES and XPS measurements, chem ical interaction between TPD and Ca was observed, while the interaction bet ween TPD and Au or Ag was weak. These results show that the origin of the v acuum level shift for TPD/Ca is of more chemical nature, and is different f rom that for TPD/Au or Ag systems. The highest occupied molecular orbital ( HOMO) and C Is levels of the TPD films gradually shifted by deposition of t he TPD and their trends were different from the abrupt shift of the vacuum level. We consider that such gradual shift is due to the final-state screen ing effect in photoemission measurements, not due to the band bending in th e space charge layer. (C) 2001 Elsevier Science B.V. All rights reserved.