Full Information Acquisition
Table 1 : Continued.
Scanning Probe Microscopy Mode
Emerging Applications: Multi-frequency imaging (GDM)
Target Materials / Systems
Ferroelectrics and multiferroics
Liquid-based imaging Polymer systems Biological systems
processed using appropriate statistical and physical methods for visualization and interpretation. In this manner, G-Mode is an alternative to lock-in, PLL, or BE detection schemes. Similar to classic detection schemes, measuring the response as a function of local or global stimuli facilitates construction of spectroscopic imaging modes [ 48 , 51 ].
SPM via G-Mode provides several unique advantages over classical detection schemes that cannot be enabled in other multi-frequency detection schemes. First, the availability of the complete, broadband data stream provides knowledge about the AFM tip-sample interaction for multiple resonance peaks, harmonics, mode mixing, and other non-linear phenomena.
Significance
Complete understanding of dynamic response. Probes temperature-dependent material properties at the nanoscale
Information Provided
System response at all frequencies for all excitation frequencies.
Measured quantity is the heat dissipated to the sample
G-Mode can be applied to all SPM modalities
Furthermore, the complete data also facilitates adaptive and data-driven signal fi ltering in the frequency domain instead of using predefi ned fi lters as in conventional AFM modes. Second, G-Mode enables multi-resolution imaging, which allows the same data to be represented as a 512 × 512 image with a low noise level or a 512 × 4096 image with higher noise level. T is advantage is ideal for measurements requiring precise lateral positioning or imaging of large areas containing small features. T ird, G-Mode enables high veracity separation of surface regions with diff erent mechanical, chemical, and electrostatic properties within a single experiment. Below, we illustrate G-Mode implemen- tation for electrostatic force microscopy (EFM), Kelvin probe
Figure 3 : G-Mode KPFM. (a) Topography image of an HOPG sample. (b) Single-point parabolas (averaged over the 4 ms pixel time) for two different locations (indicated via the red and blue squares on (a)) showing a 49 mV offset in the CPD between positions. (c) Second and (d) fi rst order fi tting coeffi cient determined from fi tting the parabola at each spatial location for the fi rst period of oscillation. (e) The CPD determined from fi tting parameters for the fi rst period of oscillation. Reprinted with permission from L Collins et al., Scientifi c Reports 6 (2016) 30557.
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www.microscopy-today.com • 2017 July
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