General
Two gas pulsing setups are available at the SLE for the time-resolved APXPS measurements: piezo valves and pneumatic valves.
| Sample mounting | Omicron plates (as per the solid-gas endstation) on a 3 axis x,y,z manipulator. |
| Sample heating | Up to ~550 C via a resistive heater |
| Sample preparation | No UHV sample preparation is available. Samples must be prepared outside and transferred via air (or inert atmosphere using the glove box). The preparation chamber in the solid-gas endstation can be used for ex-situ sample preparation. |
| Base pressure | ~ 5e-7 mbar |
Gas Pulsing
Fast piezoelectric or pneumatic valves can be installed to provide short chemical perturbations to a sample in the form of gas pulses. Synchronization of the valves with the delay-line detector (DLD) allows measuring the sample’s response with microsecond time resolution.
| Piezo Valves | Pneumatic valves | |
|---|---|---|
| Type | Attotech GR020 | Swagelok ALD valve manifold |
| Open/close duty cycle | down to 30 µs | < 5 ms |
| Gas pulse rising edge width | ~80 µs | ~10 ms |
| Typical pulsing period | tens – hundreds ms | few seconds |
| Typical local pressure | few mbars | few mbars |
The figure below shows a gas pulse created by injecting nitrogen gas onto the sample using pneumatic valves.
Detector
| Type | 2D delaylile detector |
| Max time resolution | 100 ps |
| Max. period | inf |
| Timig modes | non time-resolved, extended time, free-running |
| Software | fully supported in Specs Prodigy |
Examples
The figure below shows time-resolved N1s spectra during the pulsing of nitrogen gas using the piezo valve. The frequency of pulsing is 50 Hz. Each spectrum is equivalent to 10 µs acquisition time. With the piezo valves, one can achieve a pulse with an 80 µs rising edge and ca 1.3 ms FWHM. For more details about the setup and spike-like ga scientific examples, please see these publications.
The figure below shows the O 1s spectra measured during pulsing CO (around 0 ms) into the flow of O2 on Pt(111) at 320 C. The right panel shows examples of spectra with 160 µs resolution measured at two different time delays.
