Characterization of Li Ion Battery
Figure 1: SSRM is an implementation of a well-established SRP method used for micro- and nano-scale. A generic SRP, however, is a dual-probe technique, whereas in SSRM a conductive AFM tip scans a small device region with a common electrode. The operation of conductive AFM and SSRM is identical except that SSRM scans the cross-sectioned surface of a device, whereas in conductive AFM a generalized surface is scanned.
Te current distribution of the sample is mapped each time the tip engages the sample surface. Te current flow, pro- duced by the applied bias voltage between the conductive tip and sample, is measured at each landing point to acquire the electrical data. Generally, the current flow is very small and needs to be augmented by a current amplifier before it can be processed into an image. Te NX-Hivac AFM supports the use of internal current amplification with a variable gain of 106
∼ 1012
applied external sample bias used in this experiment was 3V. Additionally, at each point of the image, the force-distance curve was acquired and used to calculate the mechanical properties of the sample being measured. During data acqui- sition, the XY scanner stops, and the contact time is con- trolled to give enough time for the scanner to acquire precise and accurate data. All images were analyzed using Park XEI soſtware, which
drew a corresponding line profile and performed the image analysis.
Results and Discussion Conducting this experiment under high vacuum led to
improvement in sensitivity and resolution measurements when compared to the use of other techniques [11]. High vacuum also led to improved accuracy and repeatability while mini- mizing damage suffered by the tip and/or sample. Te applied force between the tip and sample under high vacuum can be substantially lower when compared to experiments conducted in ambient air or N2
, since the residual thin liquid film, always
present under ambient conditions, reduces the quality of the electrical contact [11]. Te qualitative and quantitative results acquired dur-
ing these experiments are shown in Figures 3 and 4. Figure 3 presents the topography and electrical data measured in the sample. Te topography image (Figure 3A) shows that the sample surface consists of circular-shaped plateaus with diameters ranging from 2 to 8 μm. Te circular plateaus with brighter colors represent areas with greater height, whereas
50
Figure 2: The Park Systems NX-Hivac AFM provides improved sensitivity and resolution of measurements through SSRM in high vacuum. Because high- vacuum scanning offers greater accuracy and better repeatability than ambient or dry N2 conditions, users can measure a wide range of dopant concentration and signal
PinPoint™ with SSRM enables
response in failure-analysis applications. The integration of simultaneous acquisition of
electrical, and mechanical property data.
www.microscopy-today.com • 2020 May topography, V/A that is applicable to most measurements. Te
the areas with darker color represent low-lying areas. Te resistance image (Figure 3B) features brighter-colored areas that represent higher surface resistivity, whereas areas with darker colors represent lower surface resistivity. Te darker colors on the conductance image (Figure 3C) represent areas with lower surface conductivity, whereas brighter colors rep- resent higher conductivity. When comparing topography and resistance images, one can easily observe that higher circular plateaus have lower resistance when compared to low-lying areas. Comparison of the topography and conductance images demonstrates that circular plateaus with higher height have higher conductance when compared to low-lying areas. Tis
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