NanoESCA (Photoelectron spectroscopy)
The BrUNEL (Bristol Ultraquiet NanoESCA Laboratory) in the School of Chemistry provides state-of-the-art X-ray photoelectron spectroscopy (XPS) and photoelectron emission microscopy (PEEM) instruments for surface and materials analysis. These techniques operate under ultra-high vacuum (UHV), with a typical base pressure of 1 x 10-11 mbar.
BrUNEL is housed in the ultra-quiet laboratories of the NSQI building, and is used for studying the chemical environment of new materials and nanoscale investigation of the electronic and chemical properties of device surfaces and interfaces.
X-ray photoelectron spectroscopy (XPS)
XPS is a very versatile probe of the surface chemistry and physics of materials, and BrUNEL’s XPS system is used to study a wide range of samples from biological specimens and biomolecules to electronic device interfaces and materials for quantum technology.
The instrument offers 4 different X-ray probes, including monochromatic Al Kα (1486.7 eV), small spot (60 – 200 μm) analysis, XPS imaging, angle-resolved XPS and high-resolution (≈ 300 meV) spectroscopy. A charge neutraliser is also available for non-conducting samples, and in combination with a focused Ar+ ion source, high-quality depth profiling of materials is also possible.
NanoESCA platform
The NanoESCA instrument is an energy-filtered photoelectron emission microscope (EF-PEEM) and momentum microscope capable of angle-resolved photoemission spectroscope (ARPES). The BrUNEL EF-PEEM is used to build work function maps of novel electronic device surfaces and interfaces, while ARPES is used to study the electronic band structure of quantum materials.
The instrument has a lateral resolution down to 13 nm, energy resolution < 20 meV, and momentum resolution of < 16 mÅ-1. The field of view can be adjusted between 3 μm and 1100 μm. Three monochromatic photon energies are available for spectroscopy: Ar I (11.6 eV), He I (21.2 eV) or He II (40.8 eV), at sample temperatures between 30 K and 600 K. Ultraviolet photoemission spectroscopy (UPS) can also be performed.
Surface preparation
A range of UHV surface preparation techniques are available: sample heating up to 1,300 °C; gas treatment (e.g. O2); e-beam and thermal evaporation; Ar+ ion sputter cleaning and/or etching with small spot (< 150 μm) and rastering; low-energy electron diffraction (LEED) including LEED-IV and SPA-LEED.