The SGM 1-Scienta beamline at ASTRID
Situated at ASTRID, is a surface science beamline, with a Scienta electron energy analyser and a Spherical Grating Monochromator (SGM) as its core elements. The system is well suited for high-resolution studies of shallow core levels (up to 300eV binding energy) of metals and semiconductors.
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 28 July 2009