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Sample mounting

General

In general, suitable samples are flat plates of max. 10×10 mm² surface area (depending on the sample holder used). The materials to be analyzed must be UHV compatible, electrically conductive and if possible homogeneous. Some other types of samples can be studied only if deposited on flat conductive substrates, e.g. evaporated or sputtered thin films, powders pressesd into indium foil etc.

Several sample holders are available.

The base plate, which is the same for all sample holders, is grounded, but sample can be mounted on two insulated supports with electrical contacts, each of them tightened by two molybdenum M1.2 nuts. It allows sample to be heated and/or grounded or biased.

The thermocouple (K-type, chromel-alumel) can touch the sample from the backside or be spot-welded to the sample..

The design can be further developed depending on sample properties and user requirements (cooling, heating, thermocouple reading...).



Sample holder selection table


Sample requirements Plain mounting Crystals Silicon wafer Pocket with clamps Sapphire plates STM type
number of samples on one holder up to 12 1 1 1 1 1
can be grounded yes yes yes yes yes yes
can be biased no yes yes yes no yes
annealing up to 400 °C (700 K) no yes yes yes yes yes
annealing up to 1000 °C (1300 K) no yes yes yes no yes
measurement during annealing  ≤400 °C (700 K) no yes no yes yes yes
measurement during annealing  ≥400 °C (700 K) no no no no no yes
maximum annealing current 15 A 10 A 15 A 5 A 5 A

Sample mounting

  1. Mount the sample(s) on the selected holder.
  2. Check that all nuts are properly tightened. Do not exaggerate with the force in order not to break the fragile ceramic insulators.
  3. Measure the distances in red circles in the above drawing for both heating pins and both thermocouple pins. At the moment (Nov 2017) the heating pins should be a bit higher than the indicated 3.5 mm, between 3.6 and 3.7 mm. (Due to wear the exact distances change often.)
  4. Check electrical connections (if installed):
    • sample to ground: infinity resistance, depending on the cleanliness of the ceramic insulators, practically several kΩs
    • heating element contacts: low resistance, <1Ω for metals, higher for Si wafers
    • thermocouple contacts: low resistance, several Ωs at maximum
    • sample to thermocouple: low resistance, several Ωs at maximum
  5. Blow out any dust from the sample surface.
  6. Proceed with sample insertion.
Last Updated on Sunday, 10 May 2020 21:27