XPS Facility at IOP


                      Technique of XPS

                    Photoelectrons result from the interaction of electromagnetic radiation
                    with matter. Useful energy range for the exciting radiation  is  soft X-Ray
in X-Ray Photoelectron  Spectroscopy, XPS, leading to core level
                    electrons excitation and hence to elemental selectivity. Excited photo-
                    electrons are analyzed
according to their kinetic energy, which is, at
                    least for core electrons, a fingerprint of the emitting element. Elemental                 
                    identification is therefore possible (apart
from H and He) for core level       
                    photoemission. Elements' relative abundance can in addition be made
                    semi-quantitative or quantitative.

                    Information on chemical bonds is derived either from core level shifts.    
                    Characteristic of the technique is its surface sensitivity (a few monolayers),
combined with an etching process (usually through sputtering by
                    accelerated noble ions) allows to measure elemental depth distributions.

                    The most important feature is its ability to provide detailed chemical
                    information on virtually any kind of solid sample, i.e. also on insulating
                    or easily damaged
samples.  XPS finds wide applications in several fields
                    of science (surface physics, material science, geophysics, nanomaterials,
                    biomaterials, polymers, organic

                    Specification of IOP XPS system:

                     System:                     VG system (operating since  July 2001)

                     X-Ray Source:           Dual anode  MgKa and AlKa radiation

                     Analyzer:                  Concentric Hemispherical Analyser (CHA)
                                                       with variable pass energy

                     Energy resolution:   ~0.9eV FWHM on Au4f7/2 with a pass energy of
                                                                               20eV for XPS;

                      In-depth info.:         Ar+ gun   for deph profiling

                      Sample  Stage:        Tiltable stage for angle dependent analysis
                                                       Can be resistivily heated to 8000C

                      Sensitivity:              0.5-1at%