Already a single atom or molecule added to or taken from a nanoscopic system may alter its properties significantly. This makes sample preparation in nanoscale science a great challenge. Vapor deposition in ultrahigh vacuum (UHV) is one of the most successful approaches to fabricate nanoscale systems. Combined with in-situ analysis it allows to characterize the properties of individual atoms, molecules, and their aggregates, while the environment is controlled at the atomic level. The volatility of the atoms and molecules, however, poses an intrinsic limitation on this approach, which especially prevents large molecules such as polymers, dendrimers, biomolecules, and many other synthetic functional molecules with large mass from being subject of research.
We developed electrospray ion beam deposition (ES-IBD) to solve this problem. Nonvolatile molecules can be transferred into intact molecular gas phase ions by electrospray ionization (ESI). As this requires ambient pressure conditions, a differentially pumped, six chamber vacuum system is used to form an ion beam and guide it to a sample surface in ultrahigh vacuum, where the molecular ions are deposited. The experimental setup features one of the most intense ESI sources, mass selection, mass spectrometry as well as full spatial-, energy- and current characterization of the ion beam. Samples can be 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. Moreover, we constantly improve the present setup, with the goal to make it a vacuum processing tool as successful as thermal vapor deposition.