From Surfaces to Interfaces: Ambient Pressure XPS and Beyond

The rapidly increasing field of surfaces under ambient conditions of temperature, and pressure in gas and liquid environments, reflects the importance of understanding surface properties in conditions closer to practical situations. This has been enabled by the emergence in the last two decades of a number of new techniques, both spectroscopy and microscopy, that can deliver atomic scale information with the required surface/interface sensitivity. Here we present a short review of recent advances to illustrate the novel understanding derived from the use of new techniques focusing on the gas-solid interface, where two barriers have been bridged: the pressure gap, and the temperature gap. The later gap is very important when dealing with weakly bound molecules, where only by the presence of gas at a suitable pressure can a measurable coverage of adsorbed molecules be achieved. The temperature gap manifests also in the removal of kinetic barriers. Future developments to continue extending the range of pressures are also mentioned. Finally, new challenges that appear, both from X-ray and electron-induced damage to the sample, and from contamination under high pressure of desired gases, while maintaining very low pressures of undesirable ones.