Advanced AFM

Our suite of advanced atomic force microscopes (AFM) systems enables structural and functional imaging across a broad range of materials, from soft polymeric systems to ceramic ferroelectrics. In addition, characterization can be performed in a variety of conditions including ambient, controlled gaseous and liquid environments. Nanometer mapping of electronic, magnetic, mechanical, electromechanical and electrochemical responses are made through conventional techniques or those developed at our center. The capabilities available allow these measurements to be performed under a range of external stimuli including temperature and exposure to optical excitation.

Science Overview

AFM tools available consist of four Cypher AFM (Asylum Research), two MFP-3D (Asylum Research) and two Icon Dimensions (Bruker). All instruments are coupled with peripheral instruments to enable advanced imaging and spectroscopies developed in house. These include multifrequency (e.g. band excitation) imaging and spectroscopy developed to enable crosstalk free and quantitative analysis of local material functionality. The newly developed G-Mode technique makes accessible, system dynamics/kinetics at µsec speeds. These advanced techniques enable characterization of local material properties including viscoelastic, magnetic, piezoelectric, as well as electronic and ionic transport mechanisms.

Applications

Hybrid organic–inorganic perovskites (HOIPs), have shown great potential for optoelectronic applications. However, the intrinsic physical properties, in particular the potential role of ferroelectricity has yet to be fully understood. Using band excitation, it was possible to track the AFM resonance to unveil the origin of the twin domain contrast which were previously reported by several groups. The BE data suggests that the twin domains are due to variations in elastic modulus (as opposed to piezoelectric behavior) arising from a strain driven chemical segregation. https://doi.org/10.1038/s41563-018-0152-z

AFM has opened the door to nanoscale functional imaging, but in comparison to optical or ion microscopies it is inherently slow and hence limited to exploring static or very slow processes. CNMS developments have overcome this by utilizing high speed data acquisition (G-Mode), advanced machine learning algorithms and a new fast free force recovery (F³R) procedure to denoize and deconvolute the intrinsic cantilever dynamics from the photodetector signal. We demonstrate the usefulness of this approach for ultrafast material property by applying to Kelvin Probe Force Microscopy (KPFM). We have successfully imaged ultrafast ion migration in a perovskite (CH₃NH₃PbBr₃) device in response to an applied electric field at ~15 µs readout rate, orders of magnitude faster than traditional KPFM (~4 ms). Collins, L., M. Ahmadi, T. Wu, B. Hu, S. V. Kalinin, and S. Jesse. ACS nano (2017).

Specifications

General

Sample size up to 12x12 mm²
Scan range (30 um, 80 um)
Environmental Control
- - - glove box
    - environmental cells for gases: humidity, nonreactive
    - environmental cells for liquids: aqueous buffers, ionic liquids
Temperature stage (sample heating 0-250 °C)
Photothermal Excitation (405 nm)
Electrochemical Cell