Surface analyses - NanoESCA, XPS

NanoESCA is a new sophisticated analytical instrument designed for imaging and small spot photoemission spectroscopy (XPS) with photoemission electron microscopy (PEEM).

Excitation sources range from a high-power monochromatic Al Kα( x-ray) source to UV sources such as He-, Mercury arc- and Deuterium lamps allow to work in three regimes:

• k-PEEM momentum microscope
• classical ESCA mode
• 2D imaging ESCA and PEEM modes. PEEM images a surface of a sample with lateral resolution < 50 nm and with X-ray source better than 500 nm and energy resolution approx. 0.3 eV. The optical column provides 2D cuts of momentum distribution of photoexcited electrons (ARPES) with energy resolution approx. 0.1 eV and angle of acceptance better than ± 0.1 Å-1.

The AXIS Supra photoelectron spectrometer is based on the proven AXIS technology comprising: magnetic and electrostatic transfer lenses, co-axil electron charge neutralization system for compensation of the surface charging of insulating samples, spherical mirror and hemispherical electron energy analyzer. The photoelectrons are excited by high power monochromatic x-ray source, where motorized multi-position Al/Ag anode is used. High resolution energy spectra are obtained by monochromatisation of the x-ray radiation using the 500 mm Rowland circle x-ray monochromator. Spectrometer can operate in spectroscopy or parallel imaging mode. In spectroscopy mode 180˚ hemispherical analyzer is applied for measurement of high resolution photoelectron spectra (the energy resolution < 0.5 eV). Pictures of lateral distribution of the elements on studied sample surface in parallel imaging mode (the guaranteed lateral resolution is 1 µm) are acquired by spherical mirror analyzer. Photoelectrons passing through the electron energy analyzer are detected by the 2-dimensional delay line detector much faster and at higher resolution in comparison with multipliers detection system.

The Axis Supra photoelectron spectrometer is equipped by an Ar cluster ion source. The ion source is capable to generate Arn+ clusters consisting of hundreds or thousands of Ar atoms. As the energy of the cluster ion is shared by all atoms in the cluster the energy per Ar atom can be as low as a few eV. At this energy cluster ions only sputtered material from the near surface region leaving the subsurface layer unmodified and undamaged. Therefore the cluster ion source can be used for depth profiling of multi layer organic and inorganic materials. The cluster ion source can also be operated in standard monoatomic Ar+ mode.

XPS spectroscopy and imaging results can be complemented by the ion scattering spectroscopy (ISS) technique.