Performance Test of a Laboratory-Based Ambient Pressure X-ray Photoelectron Spectroscopy System at the Gwangju Institute of Science and Technology

Abstract

The performance test of a laboratory based ambient pressure X-ray photoelectron spectroscopy (AP-XPS) system at the Gwangju Institute of Science and Technology (GIST) was carried out. The system, consisted of a Scienta R4000 HiPP-3 electron analyzer and a monochromatized Al Kα X-ray source, is designed to operate a gas pressure of up to 25 Torr. An Al polyimide X-ray window is used to isolate the X-ray source from the back-filled-type ambient pressure measurement chamber. Two modes of XPS operations were tested, a one-dimensional chemical imaging mode and a transmission mode. In the transmission mode, the lens voltage of analyzer was optimized for maximum detection of photo-excited electrons under elevated pressure condition, i.e., a typical standard lens operation mode. On the other hand, in the imaging mode, spatial information on the outgoing electrons is conserved to generate a one-dimensional chemical image of surface being measured. The test of the imaging mode on a Au/Si reference sample showed a spatial resolution of ∼10 µm under an Ar gas pressure of 500 mTorr. With the superb design of the differential pump and the electron transfer optics, a good signal-to-noise ratio was obtained for the XPS core-level spectra at Ar gas pressure up to 1 Torr.