Ultrathin films of quaterthiophene (4T) were deposited on a Ag(111) su
rface by vacuum sublimation and characterized with respect to their ge
ometric and electronic properties using several surface-sensitive tech
niques. For the monolayer (1 ML), a long-range ordered superstructure
is found by electron diffraction (LEED). This is commensurate to the A
g(111) surface due to covalent bonding of the ''flat-lying'' 4T molecu
le via its pi-system. The bonding properties can be deduced from photo
electron spectroscopy results (UPS, XPS). For multilayers (3-20 ML) a
gradual decrease of the orientational order is observed by infrared sp
ectroscopy and X-ray absorption.