  Photoelectron spectroscopy (PES) and microscopy are highly demanded for
exploring morphologically complex solid-gas and solid-liquid interfaces under
realistic conditions, but the very small electron mean free path inside the
dense media imposes serious experimental challenges. Currently, near ambient
pressure PES is conducted using sophisticated and expensive electron energy
analyzers coupled with differentially pumped electron lenses. An alternative
economical approach proposed in this report uses ultrathin graphene membranes
to isolate the ambient sample environment from the PES detection system. We
demonstrate that the graphene membrane separating windows are both mechanically
robust and sufficiently transparent for electrons in a wide energy range to
allow PES of liquid and gaseous water. The reported proof-of-principle
experiments also open a principal possibility to probe vacuum-incompatible
toxic or reactive samples enclosed inside the hermetic environmental cells.

Instrumentation and Detectors;Materials Science