High-frequency near-field microscopy

Rosner, Björn T.; Weide, Daniel W. van der

doi:10.1063/1.1482150

Cited by 219 publications

(140 citation statements)

References 272 publications

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“…Three distinct structural phases, as seen from the high resolution TEM images and the selected-area electron diffraction (SAED) patterns in Fig. 3a, are observed in ribbons in the [11][12][13][14][15][16][17][18][19][20] growth direction. Correspondingly, typical I-V characteristics of the three phases are shown in Fig.…”

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confidence: 99%

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Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy

et al. 2009

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Driven by interactions due to the charge, spin, orbital, and lattice degrees of freedom, nanoscale inhomogeneity has emerged as a new theme for materials with novel properties near multiphase boundaries. As vividly demonstrated in complex metal oxides 1-5 and chalcogenides 6,7 , these microscopic phases are of great scientific and technological importance for research in hightemperature superconductors 1,2 , colossal magnetoresistance effect 4 , phase-change memories 5,6 , and domain switching operations [7][8][9] . Direct imaging on dielectric properties of these local phases, however, presents a big challenge for existing scanning probe techniques. Here, we report the observation of electronic inhomogeneity in indium selenide (In 2 Se 3 ) nanoribbons 10 by near-field scanning microwave impedance microscopy [11][12][13] . Multiple phases with local resistivity spanning six orders of magnitude are identified as the coexistence of superlattice, simple hexagonal lattice and amorphous structures with ~100nm inhomogeneous length scale, consistent with high-resolution transmission electron microscope studies. The atomic-force-microscope-compatible microwave probe is able to perform quantitative sub-surface electronic study in a noninvasive manner. Finally, the phase change memory function in In 2 Se 3 nanoribbon devices can be locally recorded with big signal of opposite signs. 2While the conventional wisdom on solids largely results from the real-space periodic structures and k-space band theories 14 , recent advances in physics have shown clear evidence that microscopic inhomogeneity, manifested as sub-micron spatial variations of the material properties, could indeed occur under certain conditions. Utilizing various probe-sample coupling mechanisms 15 , spatial inhomogeneity has been observed as nanometer gap variations in high-Tc superconductors 1,2 , coexisting electronic states in VO 2 near the metal-insulator transition 3 , ferromagnetic domains in manganites showing colossal magnetoresistance effect 4 , and in an ever-growing list. Probing these non-uniform phases provides not only much knowledge of the underlying interactions, but also valuable information for applications of the domain structures. In particular, spatially resolved properties are of significant interest for phase change and other switching materials to be on board the nanoelectric era [5][6][7][8][9] .While a number of contrast mechanisms 15 have been employed to visualize the electronic inhomogeneity, established scanning probe techniques do not directly access the low-frequency (f) complex permittivity ε(ω) = ε′ + iσ/ω, where ε′ is the dielectric constant and σ the conductivity, which holds a special position to study the ground state properties of materials. For local electrodynamic response, near-field technique is imperative to resolve spatial variations at length scales well below the radiation wavelength 16 . For this study, the working frequency is set at ~1GHz, i.e., in the microwave regime, to stay below resonant excitation...

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“…3b. It has been previously reported that pristine VLS-grown [11][12][13][14][15][16][17][18][19][20] In 2 Se 3 nanoribbons with superlattice structures (Fig. 3a, left) exhibit metallic behavior and room temperature R 2T as low as kilo-ohms 10 .…”

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Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy

et al. 2009

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“…Apertureless probes are commonly represented by open-ended coaxial structures. These probes generate very tight near field pattern with full-width at half-maximum (FWHM) less that λ/10 at around λ/50-λ/100 standoff distance however electromagnetic coupling of these probes to the sampled material is extremely weak, considerably limiting the image resolution amplitude contrast to less than 1-2dB [8]. The other class of probes is represented by the openended waveguide structures or apertures in conductive screens [1], [10]- [13].…”

Section: Introductionmentioning

confidence: 99%

“…The essential part of any reflectometry system responsible for electromagnetic (EM) interaction with the sample and reflected signal collection is a sensing probe. This can be apertureless [8], [9] or aperture-based [1], [8], [10]. Apertureless probes are commonly represented by open-ended coaxial structures.…”

Section: Introductionmentioning

confidence: 99%

Super-Resolution Defect Characterization Using Microwave Near-Field Resonance Reflectometry and Cross-correlation Image Processing

Malyuskin

Fusco

2017

Sens Imaging

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Abstract-A super-resolution defect characterization technique based on near-field resonance reflectometry and cross-correlation image processing is proposed in this paper. The hardware part of the microwave imaging system employs a novel loaded aperture (LA) probe which allows collimation of the electromagnetic field to approximately λ/10 focal spot(s) at λ/100 to λ/10 stand-off distances, λ being the wavelength of radiation in free space. The characteristic raw image spatial resolution of the LA probe is around λ/10 in one dimension with amplitude contrast/sensitivity exceeding 10-20dB. It is demonstrated that the LA spatial resolution can be at least two times enhanced in two dimensions in the image plane using basic crosscorrelation image processing while retaining a very high level of amplitude contrast of at least 10dB.

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“…Coaxial AFM probes have previously been used for microassembly 11 and near field optical and microwave microscopy. 12 In this paper, we demonstrate dielectrophoretic imaging with a coaxial AFM probe. Imaging with dielectrophoresis ͑DEP͒ can provide topographical information as well as information about the local dielectric constant and spectrum.…”

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Coaxial atomic force microscope probes for imaging with dielectrophoresis

Brown

Berezovsky

Westervelt

2011

Applied Physics Letters

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We demonstrate atomic force microscope ͑AFM͒ imaging using dielectrophoresis ͑DEP͒ with coaxial probes. DEP provides force contrast allowing coaxial probes to image with enhanced spatial resolution. We model a coaxial probe as an electric dipole to provide analytic formulas for DEP between a dipole, dielectric spheres, and a dielectric substrate. AFM images taken of dielectric spheres with and without an applied electric field show the disappearance of artifacts when imaging with DEP. Quantitative agreement between our model and experiment shows that we are imaging with DEP. © 2011 American Institute of Physics. ͓doi:10.1063/1.3585670͔The atomic force microscope ͑AFM͒ has proved to be a useful tool to study dielectric materials at the nanoscale. 1,2 Many AFM imaging modes have emerged to study dielectric materials. Scanning polarization force microscopy has been used to study the dielectric properties of adsorbed liquid films. 3 Electrostatic force microscopy has been used to quantitatively measure the dielectric constant 4,5 and dielectric spectrum 6 of thin films. Techniques such as scanning near field microwave microscopy, 7 scanning nonlinear dielectric microscopy, 8,9 and scanning capacitance microscopy 10 directly observe electrical signals that vary with local dielectric properties. Coaxial AFM probes have previously been used for microassembly 11 and near field optical and microwave microscopy. 12 In this paper, we demonstrate dielectrophoretic imaging with a coaxial AFM probe. Imaging with dielectrophoresis ͑DEP͒ can provide topographical information as well as information about the local dielectric constant and spectrum. We begin by modeling a coaxial probe as an electric dipole to find an analytic formula for the dielectrophoretic force due to a dielectric sphere and dielectric substrate. The simulated electric field of a coaxial AFM probe is found to be well approximated by a dipolar electric field. We topographically image microspheres with a coaxial probe and find many artifacts due to the similar size of the tip and the microspheres. Imaging the same spheres under the same imaging conditions with an applied electric field improves the imaging quality and removes artifacts from tip shape. A dipole model of dielectrophoretic imaging with the coaxial tip provides an accurate fit to topographical scans of microspheres showing that imaging with DEP allows for greatly improved noncontact imaging.We model a coaxial probe as an electric dipole to find the dielectrophoretic force between a coaxial probe and dielectric spheres. Consider a dipole p ជ in vacuum oriented in the z-direction, as shown in the inset of Fig. 1. A nearby dielectric sphere of permittivity P and radius a will become polarized and experience a dielectrophoretic force, 13where 0 is the permittivity of free space and E is the electric field created by the dipole. In a vacuum, the sphere is pulled toward electric field maxima; this is positive DEP. The z-component of the force on the dipole due to the sphere is found by substituting the e...

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High-frequency near-field microscopy

Cited by 219 publications

References 272 publications

Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy

Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy

Super-Resolution Defect Characterization Using Microwave Near-Field Resonance Reflectometry and Cross-correlation Image Processing

Coaxial atomic force microscope probes for imaging with dielectrophoresis

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High-frequency near-field microscopy

Cited by 219 publications

References 272 publications

Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy

Nanoscale Electronic Inhomogeneity in In2Se3 Nanoribbons Revealed by Microwave Impedance Microscopy

Super-Resolution Defect Characterization Using Microwave Near-Field Resonance Reflectometry and Cross-correlation Image Processing

Coaxial atomic force microscope probes for imaging with dielectrophoresis

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Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy

Nanoscale Electronic Inhomogeneity in In₂Se₃ Nanoribbons Revealed by Microwave Impedance Microscopy