Model 290 Hot/Cold module leakage current

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The 10-325 specimen stage, which is commonly used on PHI Physical Electronics 5600 through 5800 XPS X-ray photo-electron spectrometer surface analysis systems, is often equipped with the model 290 Hot/Cold module.

The design of the Model 290 Hot/Cold module incorporates some zirconium oxide ceramics to electrically and thermally isolate the specimen holder from the specimen stage. Zirconium oxide has a very low thermal conductivity that is about 10% of the thermal conductivity of the more common alumina (aluminum oxide) ceramic material used on many UHV optics units. Zirconium oxide is a good choice for hot or cold specimen stages.

Over time, though, the evaporation of materials from specimens, as well as the evaporation of the filament on the Model 290, can coat the zirconium oxide ceramics. This coating can cause the specimen sample holder to become resistive to ground, which in turn affects the accuracy of target current measurements.  The leakage current of a coated ceramic might be several hundred nano amps.   This means that only target currents above that several hundred nano amps value would be measurable.   ISS or static SIMS (both options on XPS systems) need the ion current to be set in the range of 1 to 2 nA.  And aligning the monochromator requires measuring currents of 3 nA or less. If the specimen stage leakage current is high, then it would be impossible to accurately measure or set those currents.

To test your target leakage current, simply measure the target current using the +90V bias box and picoammeter without any electron, ion, or X-ray source turned on.   Typically, the leakage current will be just a few 10s of picoamps.  If the leakage current is much higher than low picoamps, the zirconium ceramics shown in the image below may be coated and should be replaced the next time the system is up to air for maintenance.

The replacement procedure is simple.

  1. Vent the chamber and remove the specimen stage.
  2. Place the specimen stage on a workbench with some aluminum foil (UHV foil preferred) so that you can catch parts that will come off the specimen stage while you are working on it.
  3. Remove the end screw and washer and slide out the first long ceramic.
  4. Install a new long ceramic and replace the washer and screw.
  5. Repeat for the other long ceramic.
  6. For the back short ceramic, first remove the bearing by removing the C clamp on the shaft and sliding the shaft out. Note that two thin washers that will come off the bearing shaft as you pull it out.
  7. Next loosen the two pan head slotted screws and slide out the old ceramic and replace it with the new one.  Tighten the 2 flat head slotted screws and then replace the bearing.
  8. For the front short ceramic, just loosen the two pan head slotted screws and remove the old ceramic and replace it with the new ceramic. Then tighten the two pan head slotted screws.

After replacing all of the zirconium oxide ceramics, the leakage current should be minimal. 

Reinstall the 10-325 specimen stage then pump down and bake out the chamber.

The RBD part number for the set of 4 ceramics is 290CK-4RE.    Contact us for more information

Coated Ceramics
Coated Ceramics


Insert new ceramic
Insert new ceramic
New ceramics installed
New ceramics installed

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