The 2π Electron Diffractometer, is the LEED system used at York for analytical LEED I-V studies. The most important feature of the instrument is that the retarding grids and phosphor screen are complete hemispheres, as shown in figure 1. This enables the imaging of diffracted beams over a complete 2p solid angle which provides a significant increase in the size of the dataset available for analysis compared with that offered by conventional LEED optics. The green phosphor-coated screen of the 2p solid angle LEED apparatus can be clearly seen in the photograph.
The York system operates at a base pressure of ~1×10-10 mbar. As well as the LEED optics it is equipped with facilities for performing AES and SEM on samples and a quadrupole mass spectrometer is fitted to allow for the monitoring of residual gas composition in the chamber. The chamber also houses the equipment needed for sample preparation, including a sample heating system, deposition sources, a quartz crystal film thickness monitor, an ion gun and provision for gas dosing.
