UHV System

In the Ion and Molecular Beam Laboratory, the growth of thin films using Molecular Beam Epitaxy (MBE) can be combined with structural characterization on an atomic scale. The setup consists of several UHV chambers, all connected to one central tube. A schematic plan view of the diffrent UHV preparation and analysis chambers is shown below.

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The samples are transported through the UHV tube with a monorail train. By means of transfert sticks, the samples can be exchanged between the train and the chambers. In this way the MBE preparation chamber is connected to various analysis chambers where structural as well as functional characterisation can be carried out. This means that as-deposited samples can be transported from the growth chamber to either one of the analysis chambers in an environment with a base pressure of 1×10-10 Torr, which protects them from oxidation.

A first UHV chamber is equipped with a Mössbauer spectrometer (CEMS). This nuclear technique provides unique microscopic information about the hyperfine interaction around the probe nuclei. Other UHV chambers are equipped with scanning tunneling microscopy (STM), which gives a direct view on the surface of the prepared layer on a atomic scale, low energy electron diffraction (LEED), which is used to obtain more information on the crystallographic structure of the film and Auger electron spectroscopy (AES), which is used to analyse the chemical composition of the film.

As mentioned in the section overview one UHV chamber which is connected to the transport tube has also access to the ion beams selected either from the Leuven ion separator or the Pelletron accelerator allowing us to perform implantations or in situ RBS measurements on MBE-grown samples. Additionally a decelaration stage is mounted in front of the sample which enables us to slow down the ion beams to a few eV on the sample position, so called "soft landing".