Nanoscale Detection of Water Vapor Contamination in Vacuum-Deposited Thin Films via Perfluorinated Organic Erbium Probes

Low contamination trapped in nanomaterials is important for the performance, efficiency, and stability of advanced optoelectronic devices. Although vacuum conditions are standard for low-temperature fabrication of such devices, water contamination remains challenging to fully eliminate. Our study demonstrates that even under a pressure of <10^-8 mbar, water molecules trapped in nanoscale thin films can exist at concentrations comparable to the functional materials. We employ the transient optical properties of perfluorinated organic erbium compounds to probe trapped water, offering an effective detection within 8 Å spatial resolution, which none of the available probing methods can ever achieve. These findings suggest that maintaining ultrahigh vacuum conditions below 10^-8 mbar is essential to minimize trapped water contamination in nanoscale thin films. Improved control of these contamination levels could contribute to enhanced stability and performance in nanoscale optoelectronic devices.