The ion source produces beams of
H,
He,
Ne, and
Ar ions
with energies up to 20 keV.
The ionization chamber of the source can be filled
to a typical pressure of 10-7 mbar.
The gas atoms are ionized by electrons emitted by a filament,
and the positively charged ions can be subsequently accelerated
to the desire energy.
Mass selection is carried out by magnetic deflection over an angle of 90°.
The size of the beam is adjusted by a set of slits.
The main (scattering) chamber is provided with 4 Knudsen-cells (K-cells)
for molecular beam epitaxy (MBE)
sample growth and with a precision
3-axes goniometer
for the sample orientation.
The temperature of the sample mounted onto the goniometer can be varied
in the range of 40 - 680 K.
Cooling is done by a closed-cycle He refrigerator,
and heating by electron bombardment.
The main chamber is further equipped with a facility
for low-energy electron diffraction
(LEED),
and three types of detectors.
One of them is a magnetic electron multiplier mounted at
a fixed backward angle of 155° with respect to the incoming beam.
Two rotatable channel plate detectors cover the forward angle
ranges from 35° to 55° and from 0° to 30°.
A surface barrier detector is mounted at a backward angle of 150°
to measure Rutherford backscattering
(RBS) spectra.
In addition, there is a preparation chamber which is equipped with
an annealing and sputtering facility.
Annealing up to a temperature of 500 °C is possible.
The annealing oven is rotatable in order to change the angle between
the sample surface and the sputtering beam from grazing to
perpendicular incidence.
The base pressure of both chambers is 2×10-10 mbar.
The preparation chamber is connected to an oxygen oven and a nitriding oven
for in situ oxidation and nitriding of the samples.
In the oxygen oven, samples can be oxidized in an
O2 pressure
up to 100 mbar, at a temperature of 20 - 800 °C.
The characteristics of the nitrogen oven will be presented in the near future.