Intended uses of the Alto 2500 with DualBeam FIB-SEM

The Alto 2500 Cryo-system has recently been attached to a FEI DB235 DualBeam FIB-SEM at Harvard's new Center for Imaging and Mesoscale Structures. This powerful combination can perform all the cryo applications that a regular SEM can provide and also enables additional applications with the FIB.

In general, when a sample is frozen and entered onto the Alto stage, a fracture surface is prepared by using the knife. Thus when the fracture path occurs along features of interest, then subsequent SEM imaging of that fracture-prepared surface provides the necessary information.

However, when the fracture does not reveal the feature of interest, then subsequent FIB milling of that surface can expose additional features for SEM imaging. Three categories of applications are being investigated with the cryo-FIB.

1. The largest category is biological applications, cross-sectioning specimens ranging from bamboo to E coli. In all applications, it is hoped that by FIB sectioning it will be possible to reveal smaller features than are typically imaged by cryo-SEM.

2. It is desired to study the agglomeration of particles within a colloid. Often such particles are studied by drying; however, the distribution of particles changes during the drying process. By freezing the solution and then sectioning with a FIB, the position of particles as they truly exist within the suspension is revealed. Repeated slicing and imaging (using specialised software) will provide a set of pictures to evaluate 3-dimensional arrangements. Material systems range from oil-based lubricants to spin-coating composite films.

3. Many thin film devices are produced which contain films that are "soft" (and/or easily volatilized), such that exposure to FIB sectioning destroys the layer. It is hoped that "FIB-ing" at cryo temperatures will enable FIB without damaging the specimen.

For more information on the ALTO™ 2500, click here.

For more information about the Center for Imaging and Mesoscale Structures, click here.