In situ grazing incidence x-ray diffraction system for clusters deposited on a low-temperature substrate

Abstract

A grazing-incidence x-ray diffraction (GIXRD) system combined with cluster formation and deposition chambers was constructed in order to study structures of clusters deposited on a low-temperature substrate. Clusters are formed by the vapor condensation method with helium gas in the formation chamber. They are injected into the deposition chamber through a nozzle and deposited on a silicon wafer cooled down to the liquid nitrogen temperature. After deposition, GIXRD measurement is carried out without changing vacuum and temperature conditions (in situ). Using the new apparatus, GIXRD measurements were performed on two different kinds of gold cluster deposits prepared on room-temperature and low-temperature substrates. The size distribution of gold clusters used for both preparation conditions was measured to be 15±7.5 Å by the transmission electron microscope observation of gold clusters sparsely deposited on amorphous carbon film. Diffraction pattern from the room-temperature deposit of gold clusters showed the bulk face-centered-cubic (fcc) structure with an average grain size of 42 Å estimated from a peak width, while that from the low-temperature deposit did not exhibit the simple fcc, but probably the icosahedron-like structure. The former result is due to coalescence growth among deposited clusters at room temperature, and the latter result suggests that the low-temperature cluster deposition does not destroy the characteristic structure of free clusters.