ReactorSPMTM

 

In a joint collaboration with the group of prof. Frenken at Leiden University, we have combined a scanning probe microscope with a flow-reactor, which allows us to "look" to a model catalyst surface at high pressures and elevated temperatures, during a catalytic reaction. Study the surface at nano-scale inside a flow reactor!

 

Benefits:

  • STM in high pressure gas flow
  • UHV sample preparation
  • Sample temp. 300K ... 570K (during flow)
  • Sample temp. 300K .. >1000K (UHV)
  • Sample exchange
  • Vibration isolation system

Applications:

Sketch of the ReactorSTM

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General information

The revolutionary new aspect of the LPM ReactorSTM system is that now samples can be both prepared and analyzed in an uncompromised UHV environment, and, without breaking the UHV, chemical reactions on the surface can be studied by STM at the atomic scale under high pressures of agressive gasses. During STM operation, the STM-tip and the sample are comprised in a tiny sealed volume inside the UHV-system.

The system can be equipped with a basic load-lock for sample introduction or with a more extended preparation chamber for ion-sputtering, LEED/Auger inspection, annealing, deposition, etc, making the system a cutting-edge surface science platform. Even a dedicated XPS-chamber can be installed. Below the functionality of the system is summarized. Click here for more information and a list of system specifications.

Measurement in gas flow

After preparation in UHV conditions, the sample can be easily transferred into the STM, without breaking the ultra-high vacuum. Having sealed off the reactor volume with our special UHV seal, immediately the approach of the STM-tip to the sample can be started, and the sample can be exposed to a high pressure of aggressive gas mixtures. In the design great care has been taken to make the mechanical loop of the STM small and stiff. As a result, the gas flows and pressure in the reactor can be changed during STM imaging. The inner parts of the reactor that are exposed to the gas are made of non-reactive materials, such as ceramics, gold-plated metals and aluminum. The sample holder is designed such, that only one specific facet of the sample is exposed to the reactive gas.

Analysis of reaction products

During the experiments, a fraction of the reacted gas is fed back into the UHV, where it is analyzed using a mass-spectrometer. In contrast to systems where the whole UHV is filled with gas, the reactor volume of our system is minimal (~ 0.5 ml). This guarantees a fast response of the gas-analyzer on the change in reaction-conditions. Aafter the high-pressure STM experiments, the STM-reactor volume can be opened directly for further analysis of the sample in the UHV environment.

The system can be tailored to meet custom requirements. Currently, and ReactorAFM upgrade for the STM system is under development. Don’t hesitate to contact the LPM office for more information or custom options.

Example:

Mass spectrometer signals and STM images measured simultaneously during CO oxidation on the Pt(110) surface at a temperature of 425 K in a flow of mixtures of CO and/or O2 at 0.5 bar. (Upper panel) Mass spectrometer signals of O2, CO, and CO2, measured directly from the reactor cell.

 

Labels (A)-(H) correspond to the STM images in the lower panel. STM images (210 nm×210 nm) are from an STM movie (65 s / image, It = 0.2 nA, Vt = 80 mV). The images were differentiated to enhance the contrast. Images (A), (B), (E), (F) and (H) show flat terraces separated by steps of the Pt lattice. This corresponds to the metallic, CO-covered surface (see text). Image (C) shows the change of the surface accompanying the step in activity at t = 2109 s (the image was built up from bottom to top). The bright scan lines and the change in slope are the result of extra thermal drift due to the increased, exothermic reaction.

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