One cannot forget that in TEM proper specimen preparation is imperative: It might determine failure or success. In order to meet needs of modern materials scientists, the HREM has a dual-beam focused ion beam: a dual-beam FIB. (figure 1) The instrument is a combination of a scanning electron microscope (SEM) and a focused ion beam (FIB). The instrument is also equipped with an energy-dispersive X-ray spectrometer (EDX) for chemical identification and an electron backscatter diffraction system (EBSD) for crystallographic analysis.

    The dual-beam Focused Ion Beam instrument of the National Centre for High-Resolution Electron Microscopy.

                                                                    Figure 1

Sculpting 3-dimensional miniature objects is the main use of the dual-beam FIB. This is achieved by directing fast ions (30 keV Ga⁺) onto an object. The ions that impinge on the object eject (or sputter) atoms and electrons from the bombarded area (figure2). Furthermore, some ions are implanted and some particles, gas-molecules that have adsorbed on the surface, are being incorporated into the material.

                                          Processes that can occur when an ion beam bombards a surface.
                                                                            Figure 2

The result is that we cut (mill) materials; or, if we deposit continuously new layers, grow materials (figure 3) Growth and milling occur only locally: at the site where the ion beam hits the surface. This allows us to sculpt 3-dimensional objects with sizes as small as the diameter of the ion beam: 10 nanometers.

Cutting (milling) a hole in and depositing a box onto a material. Milling and growth occurs only where the rastered beam hits the surface. Growth occurs only if an appropriate gas in introduced.

We use the dual-beam FIB to:

* prepare thin specimens for TEM analysis
* open materials for internal analysis
* manufacture nanodevices (figure 4)

A pattern of 100 nm wide holes in a 70 nm thick gold foil, manufactured by ion-beam milling. T he foil is being supported by a network of siliconnitride. (The foil has partially ruptured because the gold layer thickness was not homogeneous.) The perforated gold foil is used to manipulate light.