ISO TS 22292-2021 pdf download.Nanotechnologies一3D image reconstruction of rod-supported nano- objects using transmission electron microscopy.
4.1 General
Clause 4 discusses physical properties of the sample rod. For methods that can be applied to prepare
the sample rod, see Annexes A,. and F.
4.2 Choice of sample rod diameter
Sample rod diameter considerations apply to both TEM and scanning TEM (see Annex B) as follows:
a) The sample shall be rod-shaped with cross section shape no more that 50 % different from circular cross section (1:1,5 ratio of axis length for elliptical sample rod cross section);
NOTE I Rectangular cross-section that does not exceed the 1:1,5 aspect ratio is acceptable.
b) The sample rod shall be made of low atomic number material such as carbon;
c) The sample rod diameter shall be less than one inelastic mean free path for the incident electron energy in the TEM chosen. For example, at 300 keV incident electron energy a carbon rod with less than 250 nm diameter shall be utilized;
d) Sample rod diameter that exceeds twice the inelastic mean free path shall be avoided to reduce the effect of plural electron scattering in the sample rod and the associated loss of spatial resolution[J
MIZI;
e) The effect of geometrical broadening of the electron beam shall be kept at a small fraction of desired resolution of the final 3D reconstructed volume. The geometrical broadening can be estimated from instrument convergence semi-angle and collection semi-angle (11;
f) To ensure adequate image resolution, the sample rod diameter shall not exceed two times the depth of focus I.I.l.
NOTE 2 Typical imaging conditions in convcniional TEM mode at 300 keV electron energy allow for about 250 nm sample rod diameter.
NOTE 3 The choice of imaging parameters for TEM and STEM tomography, depth focus, and rod diameter is described in detail in Reference 1151.
5 Instrument factors
51 Microscope set up
5.1.1 General
This clause provides guidance on conventional parallel beam transmission electron microscope (TEM) instrumentation set up for data acquisition. For scanning TEM (STEM) instrumentation set up. see Annex B.
The critical set up parameters for TEM data acquisition are:
a) acceleration voltage (see &LZ);
b) convergence semi-angle (see 513);
c) collection angle (see LIA);
d) microscope magnification (see &L5);
e) number of pixels of the detector (see 5.1.J2);ISO TS 22292 pdf download.