Ambient pressure photoelectron spectroscopy
Electron-based spectroscopies are amongst the most powerful surface characterization techniques available. The reason lies in their surface sensitivity, which limits the information depth to just a few nanometers below a surface. In particular, X-ray photoelectron spectroscopy (XPS) is an extensively used laboratory technique that permits monitoring both changes in chemistry and electronic properties. However, the application of these techniques to real-time characterization of surface processes (“in-operando”) is limited, since they typically need to operate in ultra-high vacuum (UHV) conditions.
Further technical advances have resulted in the development of high pressure photoelectron spectroscopy instruments, the so-called high-pressure, or near ambient-pressure (NAP) XPS. These instruments combine differential pumping of the spectrometer analyzer with improved focusing of the emitted photoelectrons, allowing to perform photoelectron spectroscopy up to pressures of the order of several hundreds of mbar.
What we have here is a multi-purpose analytical system dedicated to the investigation of surface and interface dynamics, consisting of a NAP-XPS laboratory-based spectrometer (from SPECS) in combination with in-situ, real-time IR characterization (IRRAS) that can measure “in-operando” up to pressures of 25 mbar.
As you can imagine, the possibility to perform a chemical analysis of the surface in the presence of gases has opened the door to a million possibilities. The technique of ambient-pressure XPS (AP-XPS) is showing its strength in areas such as catalysis, electrochemistry, or gas sensing.