25 research outputs found
Calibration of shielded microwave probes using bulk dielectrics
A stripline-type near-field microwave probe is microfabricated for microwave
impedance microscopy. Unlike the poorly shielded coplanar probe that senses the
sample tens of microns away, the stripline structure removes the stray fields
from the cantilever body and localizes the interaction only around the
focused-ion beam deposited Pt tip. The approaching curve of an oscillating tip
toward bulk dielectrics can be quantitatively simulated and fitted to the
finite-element analysis result. The peak signal of the approaching curve is a
measure of the sample dielectric constant and can be used to study unknown bulk
materials.Comment: 10 pages, 3 figure
Modeling of a Cantilever-Based Near-Field Scanning Microwave Microscope
We present a detailed modeling and characterization of our scalable microwave
nanoprobe, which is a micro-fabricated cantilever-based scanning microwave
probe with separated excitation and sensing electrodes. Using finite-element
analysis, the tip-sample interaction is modeled as small impedance changes
between the tip electrode and the ground at our working frequencies near 1GHz.
The equivalent lumped elements of the cantilever can be determined by
transmission line simulation of the matching network, which routes the
cantilever signals to 50 Ohm feed lines. In the microwave electronics, the
background common-mode signal is cancelled before the amplifier stage so that
high sensitivity (below 1 atto-Farad capacitance changes) is obtained.
Experimental characterization of the microwave probes was performed on
ion-implanted Si wafers and patterned semiconductor samples. Pure electrical or
topographical signals can be realized using different reflection modes of the
probe.Comment: 7 figure
Microwave imaging of mesoscopic percolating network in a manganite thin film
Many unusual behaviors in complex oxides are deeply associated with the
spontaneous emergence of microscopic phase separation. Depending on the
underlying mechanism, the competing phases can form ordered or random patterns
at vastly different length scales. Using a microwave impedance microscope, we
observed an orientation-ordered percolating network in strained Nd0.5Sr0.5MnO3
thin films with a large period of 100 nm. The filamentary metallic domains
align preferentially along certain crystal axes of the substrate, suggesting
the anisotropic elastic strain as the key interaction in this system. The local
impedance maps provide microscopic electrical information of the hysteretic
behavior in strained thin film manganites, suggesting close connection between
the glassy order and the colossal magnetoresistance effects at low
temperatures.Comment: 4 pages,4 figure
Full-wave modeling of broadband near field scanning microwave microscopy
The authors would like to thank professor Dr. Gabriel Gomila from Institut de Bioenginyeria de Catalunya
(IBEC) and Universitat de Barcelona for the fruitful discussion and support, as well as to Dr. Georg Gramse from
Johannes Kepler University Linz for the experimental data. B.W. thanks the funding from the China Scholarship
Council (CSC) for the support of his research at Queen Mary University of London, UK. Y.H. would like to thank
EU-FP7 Nanomicrowave project for the financial support
Data for: Effects of Sm Substitution on Ferroelectric Domains and Conductivity in Bismuth Ferrite Ceramics
1 raw data from XRD measurement8 PFM and C-AFM images12, 13, 18 I-V curve
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Hierarchy of Electronic Properties of Chemically Derived and Pristine Graphene Probed by Microwave Imaging
Local electrical imaging using microwave impedance microscope is performed on graphene in different modalities, yielding a rich hierarchy of the local conductivity. The low-conductivity graphite oxide and its derivatives show significant electronic inhomogeneity. For the conductive chemical graphene, the residual defects lead to a systematic reduction of the microwave signals. In contrast, the signals on pristine graphene agree well with a lumped-element circuit model. The local impedance information can also be used to verify the electrical contact between overlapped graphene pieces
Data for: Effects of Sm Substitution on Ferroelectric Domains and Conductivity in Bismuth Ferrite Ceramics
1 raw data from XRD measurement8 PFM and C-AFM images12, 13, 18 I-V curvesTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV
Ferroelectric domain evolution in gold nanoparticle-modified perovskite barium titanate ceramics by piezoresponse force microscopy
<p>This work addresses the domain evolution processes in polycrystalline barium titanate (BaTiO<sub>3</sub>, BT)-based ceramics containing various amounts of gold nanoparticles (AuNPs) as an additive by using piezoresponse force microscopy (PFM). The obtained PFM images of the AuNPs-modified BT ceramics revealing the change of one spontaneously polarized state to another under various applied direct current (DC) voltage are discussed in terms of their domain topology, PFM phase shift and PFM amplitude. In general, complex microstructures containing almost round-shaped and micron-sized grains, and grain boundary regions are clearly seen in the topographic images of all samples. The obtained results point towards possibility of control the polarization switching of the AuNPs-modified BT ceramics with fined-grains sizes, by a selection of the proper applied DC voltage (V<sub>DC</sub>). The PFM investigation confirmed good dipole orientation within the AuNPs-modified BT ceramics containing submicron grain size at the elevated external fields and proved the lack of convenient domain switching of the unmodified BT case resulting from their larger grain size.</p