Deposition of mass-selected clusters studied by thermal energy atom scattering and low-temperature scanning tunneling microscopy: An experimental setup

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Abstract
We present an experimental setup for the investigation of the processes occurring during the deposition of mass-selected clusters on a well-defined surface. The sample is analyzed in situ by two complementary methods: thermal energy atom scattering (TEAS) and scanning tunneling microscopy (STM). TEAS is used to study the dynamical processes during the deposition and to gather statistical information about the resulting structures on the surface. Subsequent STM measurements allow us to investigate the collision outcome on an atomic scale. The setup is highly versatile and guarantees ultra-high-vacuum conditions and cryogenic temperatures (≈30 K) of the sample at all times even during sample transfer. Clusters are produced in a CORDIS-type cluster source. A new compact multichannel effusive He source in combination with a new Wien-filter-based He detector are used for TEAS measurements. The new low-temperature STM allows measurements in a temperature range between 8 and 450 K. Atomic resolution on the Pt(111) surface is regularly observed at T sample =8 K . The performances of the setup are illustrated by STM images obtained after the deposition of Ag 7 + clusters with E kin =95 and 1000 eV on bare Pt(111) and by measurements made of the deposition of Ag 7 + clusters with E kin =20 eV in a Xe–rare-gas matrix adsorbed on Pt(111).