Electrospray Ion Beam Deposition

Vapor deposition in ultrahigh vacuum (UHV) is one of the most successful approaches to fabricate nanoscale systems. Its power is evident when combined with in-situ analysis, where it allows characterization of individual atoms, molecules, and their aggregates in an environment controlled at the atomic level.

The volatility of the atoms and molecules, however, poses an intrinsic limitation on this vapor-based deposition approach, which especially prevents large molecules such as biomolecules, and many other synthetic functional molecules with large mass to be studied.

We developed electrospray ion beam deposition (ESIBD) to solve this problem. Nonvolatile molecules are now transferred into gas phase as molecular ions by electrospray ionization (ESI) in ambient pressure. The ions are subsequently brought into vacuum through six differentially pumped vacuum chambers to form an ion beam. The beam is aimed to a sample surface in ultrahigh vacuum to deposit the molecular ions on the surface. The experimental setup features one of the most intense ESI ion sources, mass selection, mass spectrometry, as well as full spatial-, energy- and current- characterization of the ion beam. Samples are prepared for an in situ scanning tunneling microscope (STM), for various ex-situ methods, and, using a UHV-suitcase for transfer, to other specialized UHV based instruments.

Projects revolve mainly around the structural characterization of biological molecules, the electronic structure of large functional molecules, and new approaches to fabricate functional molecular films (see here). Moreover, we constantly improve the present setup, with the goal to make it a vacuum processing tool as successful as thermal vapor deposition.