Real-time monitoring of phase transitions of vacuum deposited organic films by molecular beam deposition LEED

Abstract

We describe a special low energy electron diffraction (LEED) system that allows us to record diffraction patterns during the adsorption process of vacuum-deposited organic thin films. With this instrument that combines Knudsen cells within a reverse view LEED instrument we can evaporate three different organic materials independently and simultaneously from each other. In contrast to conventional LEED, this molecular beam deposition LEED (MBD–LEED) allows us to study the kinetics of structural phase transitions from the sub-monolayer regime up to several layers without changing the position of the sample which is located on a temperature-controlled sample holder. The performance of the device is demonstrated by a growth study of perylene-3,4,9,10-tetracarboxylic-dianhydride on Ag(110). A phase transition was in situ observed after the preparation of a single domain oriented homogeneous monolayer (“brick stone”) structure to a condensed (“herring bone”) structure which is commensurate in one direction.