The SGM 1-Scienta beamline at ASTRID
Situated on ASTRID, was a surface science beamline, with a Scienta electron energy analyser and a Spherical Grating Monochromator (SGM) as its core elements. The system was well suited for high-resolution studies of shallow core levels (up to 300eV binding energy) of metals and semiconductors.
When the new ring, ASTRID2, was built it was decided not to transfer this beam line to the new facility. However, the Scienta electron energy analyser from the endstation was incorporated into the new endstation for the AU-MatLine on ASTRID2.
The SGM1 monochromator has a usable energy range from 30 eV to 400 eV. Typical flux values are ≥ 1010 photons/sec. at 130eV (50 µm slits) and ≥109 photons/sec. at 350eV (100 µm slits). The resolution for 50 µm slits is shown in Fig. 1.
Fig. 1: Resolution of the SGM1 monochromator with a typical working setting of the slits at 50 mm.
The electron energy analyser
The system is equipped with a 200 mm mean radius spherical electron analyser (Scienta) with a video based multi-channel detector system. A resolution down to 5 meV has been demonstrated, whereas a typical working resolution is about 40 meV.
Shown in Fig. 2 is an example of a core level spectrum. The Al-2p spectrum was acquired in about two minutes, with a combined instrumental resolution of 60 meV.
Fig. 2: Al-2p core level spectrum recorded with a photon energy of 130 eV on the Al(100)-c(2x2)-Li structure
The end-station consists of two Mu-metal UHV chambers, mounted on top of each other, the upper for crystal preparation, and the lower for the analyser. The preparation chamber is equipped with a noble gas sputter gun, a LEED optic, a mass spectrometer, a gas inlet system, and facilities for alkali metal and Barium evaporation. Other metals can be deposited with an e-beam source. This source can handle rods of metal with a diameter up to 1mm. Also non-metals can be evaporated upon request. In the analyser chamber an X-ray tube is supplementing the SR from ASTRID (for impurity checks etc.).
At present we have two sample holders, one with direct current heating (up to 20A) for thin (~0.5mm) wafers (e.g. Si), and one with e- bombardment heating. Both can be cooled via a LN2 flow cryostat. The sample manipulator has x,y,z movement as well as polar and azimuthal rotations.
For further information please contact: Zheshen Li,
Last Modified 30 August 2016