What is a TEM Grid?

A TEM grid (Transmission Electron Microscope grid) is a core component used to support samples in TEM imaging. It is typically a circular metal disc with a standard diameter of 3.05 mm, featuring a micron-scale array of holes (e.g., square, round, or polygonal) that hold nanoscale samples (such as thin films, nanoparticles, or biological sections). Its primary function is to provide mechanical support while allowing the electron beam to pass through both the sample and the grid's open areas, enabling high-resolution transmission electron imaging.

1. Structure and Materials

Base Material:

Metal grids: Commonly made of copper (Cu), gold (Au), nickel (Ni), or molybdenum (Mo). Copper is the most widely used due to its low cost and good conductivity.

Specialized grids: Titanium (Ti) for corrosive environments, gold for biological samples (reduces background interference).

Grid Types:

Standard grids: E.g., 200 mesh (hole spacing ~75 μm), 300 mesh (~50 μm).

Ultra-thin carbon-film grids: Metal grids coated with a thin carbon layer (3–10 nm) to support nanoparticles or fragile samples.

Silicon nitride (Si₃N₄) window grids: Metal frames with low-stress silicon nitride membranes (50–200 nm thick), ideal for high-resolution or beam-sensitive samples.

2. Key Parameters

Mesh size: Higher mesh numbers correspond to smaller holes (e.g., 400 mesh has ~40 μm spacing).

Hole shape: Square (most common), round, or hexagonal.

Support films:

Organic films: Collodion or Formvar (polyvinyl formal), ~10–20 nm thick, used for biological samples.

Inorganic films: Carbon or silicon nitride films, more resistant to electron beam damage.

3. Applications

Materials Science:

Nanoparticles or 2D materials (e.g., graphene) dispersed directly on carbon-film grids.

Cross-section samples (e.g., semiconductor devices) prepared via FIB and transferred onto grids.

Life Sciences:

Cryo-EM (Cryo-Electron Microscopy) uses holey carbon grids (e.g., Quantifoil) for frozen-hydrated samples.

Negative-stained samples adsorbed onto organic-film grids.

Semiconductor Analysis:

Silicon nitride window grids for beam-sensitive materials (e.g., MOFs) in situ observations.

The choice of TEM grid significantly impacts imaging quality. It must be matched to the sample’s properties (conductivity, thickness, stability) and observation requirements.