Nanoscale Mapping of Dielectric Properties of Nanomaterials from Kilohertz to Megahertz Using Ultrasmall Cantilevers

Cadena, Maria J.; Sung, Seung Hyun; Boudouris, Bryan W.; Reifenberger, R.; Raman, Arvind

doi:10.1021/acsnano.5b06893

Cited by 33 publications

(20 citation statements)

References 61 publications

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“…Labardi proposed an extended model of the interaction between EFM probe tip and thin dielectric film on a conductive substrate, in which higher accurate dielectric permittivity was obtained by single-frequency measurements [18]. Taking the advantage of the high resonant frequency and low thermal noise of a subminiature cantilever beam, cantilever dynamics is correlated to the complex dielectric functions of nanoscale dielectrics at a frequency approaching to a few MHz [19]. In addition to extending the dielectric spectral range of atomic force microscopy (AFM), the method can also identify the electrostatic excitation frequency, thereby providing a higher dielectric contrast for characterizing nanomaterials.…”

Section: Introductionmentioning

confidence: 99%

Characterizing Dielectric Permittivity of Nanoscale Dielectric Films by Electrostatic Micro-Probe Technology: Finite Element Simulations

Sun

2019

Sensors

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Finite element simulations for detecting the dielectric permittivity of planar nanoscale dielectrics by electrostatic probe are performed to explore the microprobe technology of characterizing nanomaterials. The electrostatic force produced by the polarization of nanoscale dielectrics is analyzed by a capacitance gradient between the probe and nano-sample in an electrostatic detection system, in which sample thickness is varied in the range of 1 nm–10 μm, the width (diameter) encompasses from 100 nm to 10 μm, the tilt angle of probe alters between 0° and 20°, and the relative dielectric constant covers 2–1000 to represent a majority of dielectric materials. For dielectric thin films with infinite lateral dimension, the critical diameter is determined, not only by the geometric shape and tilt angle of detecting probe, but also by the thickness of the tested nanofilm. Meanwhile, for the thickness greater than 100 nm, the critical diameter is almost independent on the probe geometry while being primarily dominated by the thickness and dielectric permittivity of nanomaterials, which approximately complies a variation as exponential functions. For nanofilms with a plane size which can be regarded as infinite, a pertaining analytical formalism is established and verified for the film thickness in an ultrathin limit of 10–100 nm, with the probe axis being perpendicular and tilt to film plane, respectively. The present research suggests a general testing scheme for characterizing flat, nanoscale, dielectric materials on metal substrates by means of electrostatic microscopy, which can realize an accurate quantitative analysis of dielectric permittivity.

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Section: Introductionmentioning

confidence: 99%

Characterizing Dielectric Permittivity of Nanoscale Dielectric Films by Electrostatic Micro-Probe Technology: Finite Element Simulations

Sun

2019

Sensors

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“…CNT distribution characterization of the prepared SWCNT/PI nanocomposite samples was achieved by means of 2 ω e ‐EFM [ 35–37 ] implemented on an Asylum Research MFP‐3D‐BIO atomic force microscope while using a conductive cantilever (AC240TM‐Olympus) with a spring constant k = 1.98 N m −1 and resonance frequency ω 0 = 75.98 kHz. The 2 ω e ‐EFM technique permits the detection of subsurface CNTs in the capacitance gradient ( ∂C/∂z ) maps of SWCNT/PI samples, as similarly reported for several electrical‐based AFM techniques.…”

Section: Methodsmentioning

confidence: 99%

Enhancing Electromagnetic Interference Shielding Effectiveness of Polymer Nanocomposites by Modifying Subsurface Carbon Nanotube Distribution

Castañeda-Uribe

Bernal

2020

Adv Eng Mater

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Enhancing electromagnetic interference (EMI) shielding effectiveness (SE) of polymer nanocomposites (PNCs) relies on modification of carbon nanotube (CNT) distributions achieved by controlling fabrication parameters. However, establishing correlations between fabrication parameters, CNT distributions, and SE properties is a challenging task due to the restrictions on the traditionally implemented CNT network detection techniques and qualitative CNT distribution descriptors. Herein an SE enhancing methodology for single‐walled carbon nanotubes/polyimide (SWCNT/PI) nanocomposite films in which AC sinusoidal voltages (5, 10, and 15 V at 10 Hz) are applied during processing to control CNT distribution is presented. The prepared nanocomposite samples are characterized using scattering‐parameter measurements for SE estimation and second‐harmonic electrostatic force microscopy (2ωe‐EFM) for subsurface CNT network detection. The detected CNT networks are described by implementing the uniform‐distancing (CNTD), agglomeration (CNTA), and shielding (CNTS) quantitative CNT descriptors. The results show enhancement on the nanocomposite SE values with the increment on the CNTS descriptor, which increases with lower applied voltages during processing. The SWCNT/PI nanocomposite studied herein exhibits a predominant absorption SE mechanism, which makes it a candidate for potential EMI absorber material applications. The proposed methodology represents an alternative for the quantitative assessment of correlations between PNC properties, CNT distributions, and fabrication parameters.

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“…Nanomaterials are explorable in the field of EM and RF studies. The nanoscale mapping is possible, and dielectric values of nanomaterials can be derived over the frequency of kilohertz to megahertz . The properties of nanomaterials based on frequency pave the way for its application in EM and RF design.…”

Section: Sar Reduction Methods Based On Shield Materialsmentioning

confidence: 99%

An investigation on specific absorption rate reduction materials with human tissue cube for biomedical applications

Stephen

Hemanth

2019

Int J RF Microw Comput Aided Eng

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The objective of this study is to investigate the impact of human exposure due to electromagnetic fields and to reduce the specific absorption rate (SAR). This work focuses on the implementation of different electromagnetic shield materials such as conductive materials, dielectric materials, ferrite materials, and metamaterials that are currently used for SAR reduction. The experimental analysis is performed with the global system for mobile communication (GSM) dipole antenna operating at 900 MHz as its radiation source. The designed dipole is placed in front of a cube with similar dielectric properties of human tissue. The computation, implementation, and evaluation are performed by using the method of moments. Further calculation of SAR reduction factor (SRF), SAR 1 g, gain, directivity, and beamwidth are estimated for 15 different shield materials. There is a need for an ideal shield material that could reduce SAR and does not compromise the performance of the radiation structure. This work investigates and proposes the nanomaterials and composites as suitable shield materials for SAR reduction. This novel approach of implementation of nanomaterials has proved to increase the SRF over 90% than conventional reduction materials. In addition, gain and directivity are also increased by 50% than the existing shield materials. The currently used materials are compared with the proposed nanomaterials, and the results are analyzed. The results indicate that the nanomaterials and its composites are ideal shield material for SAR reduction.

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Nanoscale Mapping of Dielectric Properties of Nanomaterials from Kilohertz to Megahertz Using Ultrasmall Cantilevers

Cited by 33 publications

References 61 publications

Characterizing Dielectric Permittivity of Nanoscale Dielectric Films by Electrostatic Micro-Probe Technology: Finite Element Simulations

Characterizing Dielectric Permittivity of Nanoscale Dielectric Films by Electrostatic Micro-Probe Technology: Finite Element Simulations

Enhancing Electromagnetic Interference Shielding Effectiveness of Polymer Nanocomposites by Modifying Subsurface Carbon Nanotube Distribution

An investigation on specific absorption rate reduction materials with human tissue cube for biomedical applications

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