The monochromatic x-ray photoelectron spectrometer (XPS) is used for chemical analyses of ion beam modified and biomaterials surfaces. The XPS is coupled to an ion beam modification chamber is shown below. Briefly, it consists of a differentially pumped ion source attached to a preparation chamber. The ions are formed in an electron impact source at 80 eV electron energy, extracted and accelerated to ~1000 eV, mass-selected by a Wien filter, bent slightly, decelerated, refocused and transported by a series of DC lenses to the target at normal incidence and at the appropriate kinetic energy. Typical ion currents are 10 - 15 nA/cm2 with energy distributions of 2 - 3 eV FWHM and a beam width of ~1 cm. The preparation chamber also has a quartz thin film microbalance to monitor weight loss in a polymer film (Sycon), a quadrupole mass analyzer for residual gas analysis, and a Faraday cup for ion beam analysis.
The preparation chamber is connected to the XPS chamber via a load lock to transfer samples from air into ultrahigh vacuum. The x-ray source has a 600 W AlK-alpha x-ray gun mounted on a 0.7m radius Rowland circle monochromator (VSW Ltd., Macclesfield, UK). An ultraviolet source has recently been for ultraviolet photoelectron spectroscopy. The 150 mm hemispherical analyzer is equipped with a five channeltron detector (VSW). The XPS has been demonstrated to provide a maximum resolution of 0.48 eV at 3000 cps for the Ag 2p3/2 line of a clean Ag foil. There is an electron flood gun for sample neutralization. The entire system is pumped with ion and turbomolecular pumps, providing a base pressure of 2 x 10-9 torr. This instrument is shared with the research group of Mike Trenary. The ion source chamber is not shared and can be used independently of the XPS chamber.