PhD Candidate, Purdue University
Adding a third dimension to nanoscale imaging in the atomic force microscope: 3D subsurface imaging and reconstruction
In 1986, Binnig, Quate and Gerber at Stanford University and IBM invented a scientific tool that has revolutionized the way to see and manipulate matter at nanoscale . The atomic force microscope (AFM) has been ranked among the top ten advances of the past fifty years in materials science  and not surprisingly, its inventors received the prestigious 2016 Kavli Prize for nanoscience. AFM is traditionally known as an instrument for surface characterization. However, it also has the potential to investigate buried, subsurface objects, opening a third dimension for observation. The underlying principle is the detection of interactions between an AFM probe and a sample by an external wave or field that penetrates beneath the surface.
This work presents emerging techniques in AFM for 3D imaging and reconstruction of buried subsurface objects with sub-micron resolution. This approach is notable because it offers one of few ways for the non-destructive and non-invasive characterization of sub-micron size buried features, without the need of complex destructive sample preparation or the use of high energy beams, which are commonplace in other high-resolution microscopy techniques. Such characterization is relevant to understand the performance or lack thereof of diverse systems encountered when scaling down technologies or when characterizing multiphase/multilayer materials. For instance, it allows the detection of subsurface defects and analysis of interconnects in 3D structures and overlays, or the investigation of fillers distribution in nanocomposites used in flexible electronic devices.
The results demonstrate sensitive subsurface imaging with high signal-to-noise ratio of composite materials using an AFM probe that detects electrical or mechanical stress fields. This involves experimental configurations of resonance-enhanced detection techniques, such as Kelvin Probe Force Microscopy (KPFM) and contact resonance AFM (CR-AFM), respectively [3,4]. The observables consist of 2D high resolution maps, which in combination with built surrogate models, are used to estimate the properties of buried objects, thus enabling computer aided tomography from AFM data.
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 M.J. Cadena, R. Misiego, K.C. Smith, A. Avila, B. Pipes, R. Reifenberger, and A. Raman, Nanotechnology 24, 135706 (2013).
 M.J. Cadena, Y. Chen, R.G. Reifenberger, and A. Raman, Appl. Phys. Lett. 110, 123108 (2017)
Maria J. Cadena is currently a Ph.D. candidate in the school of mechanical engineering at Purdue University. She is advised by Prof. Arvind Raman and Prof. Ron Reifenberger. Her research focuses on high resolution imaging and quantitative reconstruction of subsurface nanoscale features using dynamic atomic force microscopy (AFM). This involves both experimental AFM measurements and computational modeling. The work requires a knowledge of fundamental principles in several disciplines such as electrostatics, solid mechanics, vibrations, dynamics of microcantilever beams, data acquisition/signal processing, finite element analysis, and surrogate modelling.
She received her B.Sc. degree with honors in Electronic Engineering from University of Nariño in Pasto (Colombia). After graduation, she attended University of Los Andes in Bogota (Colombia), where she received a M.Sc. degree in engineering with emphasis in electronic engineering and computers. She first joined Purdue University as a visiting research scholar in Prof. Raman’s group. During this time, she participated within the NSF grant “Cyber-enabled predictive models for polymer nanocomposites: multiresolution simulations and experiments”. After graduating from University of Los Andes, she was accepted by Purdue University to pursue a Ph.D. degree. Cadena is currently a graduate research assistant with expertise in dynamic atomic force microscopy techniques for high resolution characterization of the surface and subsurface of materials at nanoscale. She collaborates within the NSF grant “Large Scale Manufacturing of Low-Cost Functionalized Carbon Nanomaterials for Energy Storage and Biosensor Applications”. She is the superuser for the AFM recharge center at Birck Nanotechnology Center.
Her research interests include functional atomic force microscopy techniques, particularly Kelvin probe force microscopy, electrostatic force microscopy and contact resonance AFM, high resolution subsurface imaging at micro/nanoscale, three-dimensional reconstruction of nanoscale features / nanotomography, nanoscale material characterization, nanocomposites and nanoelectronic devices, inverse problems in vision and 3D tomography, computer aided design of experiments, response surface methodology.