Sample Loading on TEM grids

Sample Loading on TEM grids

Procedures

  1. Disperse your sample in acetone and ultrasonicate the sample solution for about 10 minutes.
    IPA and acetone often leave residuals after evaporation; ethanol does not leave residuals, but it is less aggressive to wash off the contaminant.


  1. Take out the silicon nitride TEM grid using a plastic tweezer (or Teflon coated tweezer) from the gel box.
    The silicon nitride TEM grid is too brittle to be handled by the metallic tweezer from the sticky gel box.
    If you     were to use metallic tweezer be extra careful.


  1. Clip the edge of the silicon nitride TEM grid with a self-closing tweezer.
    Turn the silicon nitride TEM grid so that the silicon nitride window is facing upwards.
    Never drop the silicon nitride TEM grid; never allow the silicon nitride layer in contact with any solid surface.


  1. Take out 20 uL of sample solution using a micropipette.
    Drop-cast a small quantity of liquid on the silicon nitride TEM grid     gently.
    One may drop the sample solution at an oblique angle so that the force exerts on the silicon nitride window can be reduced.


  1. Dry the silicon nitride TEM grid in an oven at ~60 oC for 20 min.
    If the sample is prone to oxidation, dry the silicon nitride TEM grid in a vacuum oven ~ 60 oC for     20 min.
    Alternatively, wick away the excess droplet with the filter paper or kimtech wipe and dry it naturally in a contamination-free environment overnight. If the sample solution is too dilute, repeat the Step 4 a few times to increase the sample loading yield.


  1. Examine if the sample is successfully loaded on the silicon window under an optical microscope or SEM.
    You shall try to see if any solvent residuals are remained, for instance, EG residual has a rainbow color.


  1. The sample-loaded silicon nitride TEM grid can be subsequently treated with the UHV Annealing System or Plasma Cleaner before STEM characterization.

Holey Carbon TEM grid vs. Silicon Nitride TEM grid

Holey Carbon TEM grids

  • An amorphous holey carbon film (dark side) is coated on the copper grid to avoid the sample drops off directly from the Cu grid.


  • We should load the sample on the dark side (i.e., front side), so that the electron beam interacts directly with the samples, followed by the amorphous carbon layer.

Silicon Nitride TEM Grids. Image source: Link

Why Silicon Nitride TEM Grid

  1. Silicon Nitride TEM grid can withstand Oxygen plasma cleaning substantially longer than Holey Carbon supported Cu Grid. Hence, organic contamination can be effectively removed in the former.

  2. Silicon Nitride TEM Grid does not generate plasmonic signals in EELS characterization. Carbon (C) and Copper (Cu) are plasmonic materials, complicating the EELS of the sample studies and analyses.

However, the silicon nitride TEM grid is much more expensive and brittle compared to the holey-carbon-supported Cu grid.

New Silicon Nitride TEM grid

Broken TEM Silicon Nitride TEM Grid