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The combined test specimen standard provides a 3 in 1 method for testing the performance of the TEM. The combined test specimen consists of graphitised carbon particles on a holey carbon which are shadowed with gold. Combines astigmatism test using perforated carbon film with resolution tests using graphitised carbon black and fine gold particles. The evaporated gold forms small polycrystalline islands in which lattice fringes can be resolved. The combined test specimen can also be used for contamination measurements by noting the carbon depositing rate within the holes of the gold film. Mounted on a 300 mesh copper TEM grid
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The finely dispersed thin gold particles on a carbon film provide an excellent high resolution TEM standard. The gold particle size distribution is normally in the 2nm to 9nm range. Image quality, magnification and instrument stability are readily determined. For resolution assessment, this standard offers a choice of crystalline orientation on static or low tilt stages. The thickness of the crystals can be calculated form the projected shape of the gold crystal. The background noise from the structure of the carbon support film helps in determining the operating transfer function.
