In situ force measurements and temperature control: the FIB/SEM as a mechanical characterization tool

Abstract text (incl. figure legends and references)

Introduction

Mechanically characterizing materials inside FIB/SEMs is a common task with a myriad of use cases in various fields of research. In addition, when studying material properties, taking the sample temperature into account can be of great importance. Furthermore, some materials (e.g. certain polymers) do not lend themselves to observation in the SEM as the energy introduced by the electron beam may alter the sample (e.g. melting). Such effects can be suppressed by reducing the sample"s temperature using a cooling stage.

Objectives

In this work, the authors will present several examples of how in situ force measurements can be performed using different setups inside the FIB/SEM's chamber, thus utilizing the FIB/SEMs capability to modify, customize or otherwise prepare samples for testing as well as image samples from different angles for a more comprehensive set of images for later analysis.

Materials & methods

The described measurements are achieved using one of three setups: 1. Smallest forces - in the range of some nN - can be measured using self-sensing, piezo-resistive AFM cantilevers. 2. Another option is to utilize moveable sample holders with precisely calibrated spring constants. In this manner the deflection observed in the FIB/SEM can be used to calculate the applied force. By choosing from spring loaded sample holders with varying spring constants, a wider range of forces can be addressed. 3. Force transducers can be used to measure large forces up to several N. Each approach has its own distinct use cases, advantages, and disadvantages. These will be discussed, as well. Several the proposed force measurement applications can be combined with a compact heating and cooling stage for temperature control during the experiment.

Results

Examples include bending FIB cut beams and comparing EBSD results obtained pre and post bend (Fig. 1: FIB cut beam after bending failure (courtesy Archie, MPIE)), flat punch experiments for elucidating forging properties of novel superalloys (Fig. 2: Flat punch of a super alloy cube set in a FIB-cut base (courtesy Roesler, TU Braunschweig)), characterizing nanowires,CNTs, and other structures, etc.

Conclusion

With the appropriate set of tools, a wide range of mechanical characterization experiments can be performed inside a FIB/SEM"s chamber thereby harnessing the power of the high SEM"s resolution imaging, the FIB"s secondary viewing angle as well as the ability to modify/shape small samples for site-specific micro-analyses, in addition to the myriad of other detectors and add-ons such as EBSD, EDX, STEM, etc.