The Nanoscale World

PeakForce TUNA - Simultaneous Electrical and Mechanical Property Mapping

Sat, Mar 12 2011

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PeakForce TUNA - Simultaneous Electrical and Mechanical Property Mapping

AFM-based conductivity measurements are a powerful technique for nanometer-scale electrical characterization on a wide range of samples. Traditionally, these measurements have been categorized into two classes: Conductive AFM (CAFM), which covers the higher current range (sub-nA up to μA), and Tunneling AFM (TUNA), which covers the lower current range (sub-pA up to nA). Because of practical limitations, most conductive AFM measurements have been restricted to the Contact Mode of AFM operation. As for TUNA, it has become common to use the term to refer to both the sensing module and the measurement technique, regardless of the current-level. As a technique, TUNA has 3 key elements: 1) the current sensor, also known as the TUNA module, 2) the conductive AFM probe, and 3) the base mode of AFM operation. Each of these elements contributes to the technique's capabilities, but also to its limitations. Improvement to any of these areas has the potential to improve the technique's overall performance and applications. Bruker has developed an enhanced TUNA module with its proprietary PeakForce Tapping™ mode of operation1 that makes significant improvements to all three of these elements to enable 1) exquisite tip-sample force control, which is ideal for soft delicate samples, 2) quantitative nano-mechanical material property mapping through PeakForce QNM™, 3) correlated nanoscale electrical property characterization through TUNA, and 4) extreme ease of use through the ScanAsyst™ image optimization algorithms. A special probe has also been designed for use on particularly challenging samples. This note discusses the basics of PeakForce TUNA™, compares it to standard Contact Mode–based TUNA, and provides data demonstrating the unique capabilities and differentiated applications enabled through the combination of PeakForce Tapping and AFM conductivity measurement.

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