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Brinciotti E.,Keysight Technologies Austria GmbH | Campagnaro G.,Keysight Technologies Austria GmbH | Badino G.,Keysight Technologies Austria GmbH | Kasper M.,Keysight Technologies Austria GmbH | And 6 more authors.
IEEE Transactions on Nanotechnology | Year: 2017

Broadband dS11/dV dopant profiling at gigahertz frequencies and in situ calibrated capacitance-voltage spectroscopy of silicon p-n junctions using scanning microwave microscopy (SMM) are reported. Using a 3-D finite element model to obtain the E-field distribution at the tip/sample interface, we show that the reflected S11 signal is expected to vary monotonically with the doping concentration. S11 imaging performed on two doped silicon samples confirms the simulation results for the full SMM operating frequency range of 1-20 GHz. In this frequency range, we compare the S11 data with the differential dS11/dV data commonly used for dopant profiling. In standard SMM operating conditions, the S11 data are monotonic over the full frequency range of 1-20 GHz, while the dS11/dV data show a monotonic dependence on the doping concentration between 1014 and 1020 atoms/cm3 only at lower frequencies. A nonmonotonic behavior is typically observed at higher frequencies and an interpretation based on charged carriers dynamic is given. This is important for routine and robust frequency selection workflows of dS11/dV for dopant profiling applications. We also show S11 based calibrated capacitance measurements and capacitance-voltage curves of differently doped sample regions and of p-n junction interfaces. © 2016 IEEE.


Kasper M.,Keysight Technologies Austria GmbH | Gramse G.,Johannes Kepler University | Kienberger F.,Keysight Technologies Austria GmbH
IEEE MTT-S International Microwave Symposium Digest | Year: 2016

We present a new calibration method for nanoscale complex impedance imaging by scanning microwave microscope (SMM), which does not require any calibration samples. Instead, the vector network analyser (VNA) and the corresponding electronically switched calibration (ECal) capabilities in combination with time domain gating and microwave network modelling are used to de-embed the full system. Based on this workflow the measured complex SMM-S11 signal can be directly split into the reactive and lossy sample behavior. Nano Schottky diodes on a semiconductor substrate were measured to demonstrate that the sample conductance and susceptance correspond directly to S11 amplitude and phase, respectively. In the final step of the workflow we apply a calibration based on SMM tip approach curves resulting in quantitative impedance values. This method can have various applications starting from semiconductor failure analysis to novel 2D materials and biological cells in liquid environment. © 2016 IEEE.


Biagi M.C.,Institute Of Bioenginyeria Of Catalonia Ibec | Fabregas R.,Institute Of Bioenginyeria Of Catalonia Ibec | Gramse G.,Johannes Kepler University | Van Der Hofstadt M.,Institute Of Bioenginyeria Of Catalonia Ibec | And 6 more authors.
ACS Nano | Year: 2016

We quantified the electric permittivity of single bacterial cells at microwave frequencies and nanoscale spatial resolution by means of near-field scanning microwave microscopy. To this end, calibrated complex admittance images have been obtained at ∼19 GHz and analyzed with a methodology that removes the nonlocal topographic cross-talk contributions and thus provides quantifiable intrinsic dielectric images of the bacterial cells. Results for single Escherichia coli cells provide a relative electric permittivity of ∼4 in dry conditions and ∼20 in humid conditions, with no significant loss contributions. Present findings, together with the ability of microwaves to penetrate the cell membrane, open an important avenue in the microwave label-free imaging of single cells with nanoscale spatial resolution. © 2015 American Chemical Society.


Sardi G.M.,National Research Council Italy | Lucibello A.,National Research Council Italy | Kasper M.,Johannes Kepler University | Gramse G.,Johannes Kepler University | And 3 more authors.
Applied Physics Letters | Year: 2015

In this work, we present the analytical modeling and preliminary experimental results for the choice of the optimal frequencies when performing amplitude and phase measurements with a scanning microwave microscope. In particular, the analysis is related to the reflection mode operation of the instrument, i.e., the acquisition of the complex reflection coefficient data, usually referred as S11. The studied configuration is composed of an atomic force microscope with a microwave matched nanometric cantilever probe tip, connected by a λ/2 coaxial cable resonator to a vector network analyzer. The set-up is provided by Keysight Technologies. As a peculiar result, the optimal frequencies, where the maximum sensitivity is achieved, are different for the amplitude and for the phase signals. The analysis is focused on measurements of dielectric samples, like semiconductor devices, textile pieces, and biological specimens. © 2015 AIP Publishing LLC.


Oladipo A.O.,Bio Nano Consulting | Oladipo A.O.,University College London | Lucibello A.,National Research Council Italy | Kasper M.,Johannes Kepler University | And 6 more authors.
Applied Physics Letters | Year: 2014

We present a comprehensive analysis of the imaging characteristics of a scanning microwave microscopy (SMM) system operated in the transmission mode. In particular, we use rigorous three-dimensional finite-element simulations to investigate the effect of varying the permittivity and depth of sub-surface constituents of samples, on the scattering parameters of probes made of a metallic nano-tip attached to a cantilever. Our results prove that one can achieve enhanced imaging sensitivity in the transmission mode SMM (TM-SMM) configuration, from twofold to as much as 5× increase, as compared to that attainable in the widely used reflection mode SMM operation. In addition, we demonstrate that the phase of the S21-parameter is much more sensitive to changes of the system parameters as compared to its magnitude, the scattering parameters being affected the most by variations in the conductivity of the substrate. Our analysis is validated by a good qualitative agreement between our modeling results and experimental data. These results suggest that TM-SMM systems can be used as highly efficient imaging tools with new functionalities, findings which could have important implications to the development of improved experimental imaging techniques. © 2014 AIP Publishing LLC.


PubMed | Johannes Kepler University, University of Zagreb and Keysight Technologies Austria GmbH
Type: Journal Article | Journal: Biosensors | Year: 2016

We developed an impedance quartz crystal microbalance (QCM) approach with the ability to simultaneously record mass changes and calibrated energy dissipation with high sensitivity using an impedance analyzer. This impedance QCM measures frequency shifts and resistance changes of sensing quartz crystals very stable, accurately, and calibrated, thus yielding quantitative information on mass changes and dissipation. Resistance changes below 0.3 were measured with corresponding dissipation values of 0.01 U (micro dissipation units). The broadband impedance capabilities allow measurements between 20 Hz and 120 MHz including higher harmonic modes of up to 11th order for a 10 MHz fundamental resonance frequency quartz crystal. We demonstrate the adsorbed mass, calibrated resistance, and quantitative dissipation measurements on two biological systems including the high affinity based avidin-biotin interaction and nano-assemblies of polyelectrolyte layers. The binding affinity of a protein-antibody interaction was determined. The impedance QCM is a versatile and simple method for accurate and calibrated resistance and dissipation measurements with broadband measurement capabilities for higher harmonics measurements.


PubMed | Johannes Kepler University, University of Manchester, Institute Of Bioenginyeria Of Catalonia Ibec and Keysight Technologies Austria GmbH
Type: Journal Article | Journal: ACS nano | Year: 2016

We quantified the electric permittivity of single bacterial cells at microwave frequencies and nanoscale spatial resolution by means of near-field scanning microwave microscopy. To this end, calibrated complex admittance images have been obtained at 19 GHz and analyzed with a methodology that removes the nonlocal topographic cross-talk contributions and thus provides quantifiable intrinsic dielectric images of the bacterial cells. Results for single Escherichia coli cells provide a relative electric permittivity of 4 in dry conditions and 20 in humid conditions, with no significant loss contributions. Present findings, together with the ability of microwaves to penetrate the cell membrane, open an important avenue in the microwave label-free imaging of single cells with nanoscale spatial resolution.


PubMed | Johannes Kepler University, U.S. National Institute on Drug Abuse, Keysight Technologies Austria GmbH and Medical University of Vienna
Type: Journal Article | Journal: Angewandte Chemie (International ed. in English) | Year: 2016

Controversy regarding the number and function of ligand binding sites in neurotransmitter/sodium symporters arose from conflicting data in crystal structures and molecular pharmacology. Here, we have designed novel tools for atomic force microscopy that directly measure the interaction forces between the serotonin transporter (SERT) and the S- and R-enantiomers of citalopram on the single molecule level. This approach is based on force spectroscopy, which allows for the extraction of dynamic information under physiological conditions thus inaccessible via X-ray crystallography. Two distinct populations of characteristic binding strengths of citalopram to SERT were revealed in Na(+)-containing buffer. In contrast, in Li(+) -containing buffer, SERT showed only low force interactions. Conversely, the vestibular mutant SERT-G402H merely displayed the high force population. These observations provide physical evidence for the existence of two binding sites in SERT when accessed in a physiological context. Competition experiments revealed that these two sites are allosterically coupled and exert reciprocal modulation.


PubMed | Johannes Kepler University, National Research Council Italy and Keysight Technologies Austria GmbH
Type: Journal Article | Journal: The Review of scientific instruments | Year: 2016

In this paper, we present in detail the design, both electromagnetic and mechanical, the fabrication, and the test of the first prototype of a Scanning Microwave Microscope (SMM) suitable for a two-port transmission measurement, recording, and processing the high frequency transmission scattering parameter S21 passing through the investigated sample. The S21 toolbox is composed by a microwave emitter, placed below the sample, which excites an electromagnetic wave passing through the sample under test, and is collected by the cantilever used as the detector, electrically matched for high frequency measurements. This prototype enhances the actual capability of the instrument for a sub-surface imaging at the nanoscale. Moreover, it allows the study of the electromagnetic properties of the material under test obtained through the measurement of the reflection (S11) and transmission (S21) parameters at the same time. The SMM operates between 1 GHz and 20 GHz, current limit for the microwave matching of the cantilever, and the high frequency signal is recorded by means of a two-port Vector Network Analyzer, using both contact and no-contact modes of operation, the latter, especially minded for a fully nondestructive and topography-free characterization. This tool is an upgrade of the already established setup for the reflection mode S11 measurement. Actually, the proposed setup is able to give richer information in terms of scattering parameters, including amplitude and phase measurements, by means of the two-port arrangement.


PubMed | Keysight Technologies Austria GmbH
Type: Journal Article | Journal: Nanoscale | Year: 2015

We present a new method to extract resistivity and doping concentration of semiconductor materials from Scanning Microwave Microscopy (SMM) S11 reflection measurements. Using a three error parameters de-embedding workflow, the S11 raw data are converted into calibrated capacitance and resistance images where no calibration sample is required. The SMM capacitance and resistance values were measured at 18 GHz and ranged from 0 to 100 aF and from 0 to 1 M, respectively. A tip-sample analytical model that includes tip radius, microwave penetration skin depth, and semiconductor depletion layer width has been applied to extract resistivity and doping concentration from the calibrated SMM resistance. The method has been tested on two doped silicon samples and in both cases the resistivity and doping concentration are in quantitative agreement with the data-sheet values over a range of 10(-3) cm to 10(1) cm, and 10(14) atoms per cm(3) to 10(20) atoms per cm(3), respectively. The measured dopant density values, with related uncertainties, are [1.1 0.6] 10(18) atoms per cm(3), [2.2 0.4] 10(17) atoms per cm(3), [4.5 0.2] 10(16) atoms per cm(3), [4.5 1.3] 10(15) atoms per cm(3), [4.5 1.7] 10(14) atoms per cm(3). The method does not require sample treatment like cleavage and cross-sectioning, and high contact imaging forces are not necessary, thus it is easily applicable to various semiconductor and materials science investigations.

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