Fracture of Silicon: Influence of rate, positioning accuracy, FIB machining, and elevated temperatures on toughness measured by pillar indentation splitting

Abstract

The pillar indentation splitting test is a novel technique for assessing the fracture behavior of materials using micro-scale pillar samples. One typical limitation of this technique is the necessity of fabricating samples using focused ion beam (FIB) machining, which both creates damage to the samples and limits the number of samples which can be manufactured in a set timeframe. An alternative fabrication technique, lithography, is used here to fabricate a large number of (100)oriented, Silicon micro-pillar samples. This allowed parametric studies of pillar splitting to be performed to study the influence of testing rate and positioning accuracy. Further, it allows the comparison of samples produced using different methods (lithography, Gallium FIB, and Xenon FIB) as a function of size. FIB damage was found to significantly increase the apparent toughness at smaller pillar sizes, but the influence diminishes to negligibility at pillar diameters > 10 µm. Lastly, the fracture behavior of Silicon was investigated as a function of temperatures up to 300 °C. Apparent toughness values began increasing at 175 °C due to crack blunting due to partial dislocation-mediated plasticity. At temperatures > 250 °C, the plasticity was sufficient to prevent splitting -requiring elastic-plastic fracture mechanics methods for further analysis.

Micropillar compression of single crystal tungsten carbide, Part 1: Temperature and orientation dependence of deformation behaviour

“…However, micropillar compression is not straightforward. Even at room temperature, there can be issues of reproducibility arising from the variation in precise pillar dimensions, including, for example, edge rounding and side wall taper [27], and possible damage from the ion beam [28][29][30][31] used to produce the pillar. Care must be taken to minimise the possible effect of ion beam damage on nucleation and slip of dislocations from the sample surface.…”

Conductivity, microstructure and mechanical properties of tape-cast LATP with LiF and SiO2 additives

“…Micropillars were fabricated by focused ion beam (FIB) cutting using an Auriga cross-beam instrument (Carl Zeiss Microscopy, Oberkochen, Germany) operated at an acceleration voltage and beam currents of 30 kV and 2-16 nA, respectively. In order to minimize any potential influence of FIB damage on K IC , the diameter of the pillars should be 10 lm or larger [38]. Therefore, for each specimen 5 pillars with a target diameter of 10 lm were cut.…”

“…For each pillar, topographic images were recorded in order to confirm the pillar geometry using a laser confocal LEXT OLS6000 microscopy instrument (OLYMPUS, Hamburg, Germany) employing a step size of 0.2 lm. The positioning of the indenter tip in the center of the pillars was ensured and errors due to indenter positioning can be neglected [38]. Subsequently load-controlled indentation tests were performed at a load rate of 0.5 mN/s to split the pillars using a NanoXtrem nanoindenter (Micro Materials, Wrexham, UK) equipped with a Berkovich type diamond tip.…”

Optimizing the conductivity, microstructure and mechanical properties of tape-cast LATP with LiF and SiO2 additives

“…cutting using an Auriga cross-beam instrument (Carl Zeiss Microscopy, Oberkochen, Germany) operated at an acceleration voltage and beam currents of 30 kV and 2-16 nA, respectively. In order to minimize any potential in uence of FIB damage on K IC , the diameter of the pillars should be 10 µm or larger [33].…”

“…For each pillar, topographic images were recorded in order to con rm the pillar geometry using a laser confocal LEXT OLS6000 microscopy instrument (OLYMPUS, Hamburg, Germany) employing a step size of 0.2 µm. The positioning of the indenter tip in the center of the pillars was ensured and errors due to indenter positioning can be neglected [33]. Subsequently load-controlled indentation tests were performed at a load rate of 0.5 mN/s to split the pillars using a NanoXtrem nanoindenter (Micro Materials, Wrexham, UK) equipped with a Berkovich type diamond tip.…”