Lithium field desorption microscope: a new tool for surface investigations

The mobility of an alkali promoter as probed in situ during a catalytic reaction: Li in the CO oxidation on Pt

“…The Li-FDM apparatus, which is based on a standard FIM in a bakeable UHV system, is described in detail elsewhere, 22 and only the principle of operation is outlined here. In the Li-FDM mode, lithium adatoms are field desorbed from the apex of the tip as Li C ions that in turn create a (channelplate intensified) projection of the adsorption sites on the fluorescent screen (see Fig.…”

“…The latter made possible the visualization of the dynamic surface processes using the Li C ions as the imaging species. 22 With this technique, surface reactions such as the CO oxidation on Pt or Rh surfaces can also be visualized in situ. 23,24 In the present study, we report on the first attempt to monitor the surface diffusion of Li during the Limodified catalytic CO oxidation on Pt with the Li-FDM.…”

Field Ion and Field Desorption Microscopy: Surface Chemistry Applications

“…29 While in the first case, the imaging process is rather instable because of the evaporation of the specimen during visualization 30 ; in the second one, especially when using Li + ions supplied by diffusion from the specimen shank, stable images comparable with those obtained by FIM can be obtained. 31 The corresponding device, lithium field desorption microscope (Li-FDM) developed by Medvedev and Suchorski in the 1990s, 32 is based on the principle that surface sites can be visualized by radial projection of the Li + ions field-desorbed from these sites themselves. Desorbed Li atoms are continuously replaced by surface diffusion from the long-lasting multilayer Li deposit on the shank of the tip (Figure 4).…”

“…The initial development of Li-FDM was concerned with the imaging of different clean and adsorbate-covered metal surfaces, investigations of the mechanisms of Li-FDM image formation, 31,32 and visualization of dynamic reaction-diffusion processes. 33 As a result, the Li-FDM is capable of operating in the presence of CO and oxygen (up to 10 À3 mbar) and of imaging at these conditions the dynamic processes on metal surfaces with a time resolution of 0.01 s. Figure 5 shows an example of such visualization for the [110]-oriented Pt tip.…”

Probing adsorption on a nanoscale: field desorption microspectroscopy

“…This concept was first realized experimentally for adsorbed alkali atoms using a lithium field desorption microscope (Li-FDM), where the Li-ions field desorbed from the surface image the latter with a nearly atomic resolution (Medvedev et al 1994), combined with a retarding potential analyzer. In this way, the binding energy of Li-adatoms field-desorbed from individual surface sites on W(111) was determined 1996).…”