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In the past two years, a reel-to-reel (R2R) scanning hall probe microscope (SHPM) measurement system has been developed and routinely used at the University of Houston for continuous and 100% testing of REBCO-coated conductors. The background magnetic field interference has been eliminated by introducing FFT into the current density calculation. The noise has been reduced by a factor of 5 after customizing the motor driver. Moreover, since the data acquisition module has been upgraded to 100 kSPS sampling rate, the resolution has reached 0.06 mm2 under the measurement configuration of 8 scans per second with scanning range of 18 mm and tape motion speed of 10 mm/s. Such resolution is likely the best reported by any group at such testing speed. It has enabled our R2R measurement system to obtain detailed current density map of narrow wires and striated multifilament tapes. With the features, the R2R SHPM is turning out to be very valuable metrology and quality assurance tool for long REBCO-coated conductors.

Within the last three decades Scanning Probe Microscopy has been developed to a powerful tool for measuring surfaces and their properties on an atomic scale such that users can be found nowadays not only in academia but also in industry. This development is still pushed further by researchers, who continuously exploit new possibilities of this technique, as well as companies that focus mainly on the usability. However, although imaging has become significantly easier, the time required for a safe approach (without unwanted tip-sample contact) can be very time consuming, especially if the microscope is not equipped or suited for the observation of the tip-sample distance with an additional optical microscope. Here we show that the measurement of the absolute tip-sample capacitance provides an ideal solution for a fast and reliable pre-approach. The absolute tip-sample capacitance shows a generic behavior as a function of the distance, even though we measured it on several completely different setups. Insight into this behavior is gained via an analytical and computational analysis, from which two additional advantages arise: the capacitance measurement can be applied for observing, analyzing, and fine-tuning of the approach motor, as well as for the determination of the (effective) tip radius. The latter provides important information about the sharpness of the measured tip and can be used not only to characterize new (freshly etched) tips but also for the determination of the degradation after a tip-sample contact/crash.

A magnetic measuring microscope with a spatial resolution of 3 μm in the determination of current dipole coordinates is described. For the primary transducer, a film Hall transducer with sensitive-zone dimensions of 250 × 400 μm is used. The transducer is positioned at a distance of 3 mm from the plane of scanning. Superresolution as compared to the sensor dimensions and distance from the object was reached by using a priori information about the scanned object. A means of calibration of the magnetic microscope and measurement of its metrological characteristics is proposed. The effectiveness and consistency of the obtained estimate of coordinates is shown by comparison of the random error in measurements of current dipole coordinates with the Cramer–Rao bound. The measuring microscope can be applied in studying elements of functional electronics.

Two reel-to-reel critical current (Ic) measurement systems for REBCO coated conductors (CCs) have been developed at the University of Houston. The first reel-to-reel system is based on the traditional four-probe method with a background field (up to 5 T) perpendicular to the tape surface. At present, in-field critical current of HTS tapes is measured typically over short samples cut from the ends of long tapes. Continuous in-field current transport testing of long tapes is done only at field lower than 1 T. Previously we found that Ic at low temperature in high fields, which is important for magnet applications, is strongly related to the Ic at 77 K, 3 T (perpendicular to tape) while not as much to 77 K, self-field Ic. Hence, we established a reel-to-reel system for measurement of Ic of CCs at 77 K, (B perpendicular to tape) so that in-field performance of long tapes can be qualified over their entire length and variations in in-field performance at lower temperatures can be accurately determined. The second reel-to-reel system uses a scanning Hall probe microscope (SHPM) and is for two-dimensional critical current density mapping and characterization of multi-filamentary CCs. Critical current distributions in both non-striated and 12-filament laser-striated long CCs have been mapped using this method. A novel iterative data analysis technique that was recently developed has been applied to the analysis of multi-filamentary CCs using the SHPM system.

The new digital teslameter system (also called Gaussmeter) incorporates a 3-axis Hall probe, analog electronics based on the spinning-current technique, 24-bit analog-to-digital converter, computer, and 7-digit touch-screen display. The Hall probe is a single silicon chip with monolithically integrated horizontal and vertical Hall magnetic sensors and a temperature sensor. The Hall sensor chip is encapsulated in a robust ceramic package, a version of which is only 250 μm thick. The spinning-current eliminates most of the Hall probe offset, low-frequency noise, and the planar Hall voltage. The errors due to the Hall element non-linearity and the variations in the probe electronics temperatures are eliminated by a calibration procedure based on a three-variable second-order polynomial. The errors due to the angular errors of the Hall probe are eliminated by a calibration of the sensitivity tensor of the probe. These new developments resulted in a teslameter that can measure magnetic field vectors from about 1 μT to 30 T, with the spatial resolution 100 μm, magnetic resolution ±2 ppm of the range, the accuracy ±0.0001% of reading +0.001% of range, temperature coefficient less than 5 ppm/°C, and angular errors less than 0.1 deg.

International audience

The fracture of the atomic-scale contact should be investigated for understanding the mechanism of the mechanical processing. Using a combination of the scanning probe microscope (SPM) with possible high space resolution and the acoustic emission (AE) with high sensitivity for fracture is one of the possible way of investigating the fracture mechanism. When using the SPM, the AE signal might be detected with receiving the AE wave by the piezoelectric tube scanner of the SPM receiving the AE wave, where by the piezoelectric effect the electric signal due to the AE wave is superimposed on the scan signal. Based on that, in this study, a novel method to detect AE signal from the scan signal is proposed. With this method, without changing the SPM body, the AE could be detected, and a two-dimensional AE source location could be possible by using four divided electrodes of the piezoelectric tube scanner. By a simple experiment using the AE wave simulator, the AE signal seems to be detected by the piezoelectric scanner of the SPM. Also, one of the typical data from the experiment suggests the AE source location might be possible. In the experiment of the indentation using atomic force microscope (AFM), which is one of the SPM, the AE signal is observed reproducibly.

A tapping mode scanning probe microscopy (TM SPM) system for surface measurement in nanoscale is developed, of which the main element is a scanning probe consisting of quartz tuning fork and a long sharp tungsten tip. Quartz tuning fork is a very good resonant element with piezoelectrical characteristic, and it acts as an actuator and a force sensor simultaneously in the probe. The vertical spatial resolution of the TM SPM is up to sub-nanometer (0.11 nm) and the measuring force is in micro Newton magnitude (about 30 μN). In the scanning operation, the probe vibrates at its resonant frequency, so that the amplitude or frequency (or phase) of the resonant tuning fork is very sensitive to external forces (Its quality factor in air is about 3138). Using the TM SPM constructed by this probe, silicon samples are scanned. Their topography and phase images which indicate the surface material characteristics are reconstructed effectively with a high resolution and low destructiveness. Soft materials, such as Protein structure can also be scanned theoretically without damage. In addition, because of the using of the long sharp tungsten tip, the system has the capacity of measuring micro structures with large aspect ratio, such as large micro steps, deep micro trenches, etc.

Polarization interferometric nonlinear confocal microscope has been developed to observe a submicron size object in high contrast. The microscope succeeded in resolving the inside of a 200-nm-diameter polymeric nanoparticle. According to CTF (contrast transfer function) measurement and three-dimensional imaging with the microscope, the best spatial resolution for the microscope is 10 nm.

We report on investigations of the quantum Hall chiral edge states using a near-field scanning optical microscope that enables us to irradiate circularly polarized light from the probe tip with spatial resolution below the diffraction limit. We have found a clear evidence for the formation of spin-split incompressible strips near the edge of a two-dimensional electron system in high magnetic fields.

A 12-filament laser striated coated conductor is studied using Scanning Hall Probe Microscopy (SHPM). Remanent field is measured and critical current density distribution is calculated according to the measured field map. The results show that the SHPM technique is very sensitive to defects. A point-like defect can be readily discerned in the magnetic field map, even when the drop in critical current density is small. We also found that the choice of a proper filter is important for obtaining accurate critical current density values, especially for the multifilament superconducting tapes.

A wave optical calculation of the probe size of a low energy scanning electron microscope is presented. The resolution for the optimal aperture was computed and compared with results of standard approaches. The effect of deflection aberrations is also considered, and it was found to be critical for the landing energies below 5eV and fields of view larger than 100 x 100 μm2.

This paper is dedicated to develop an atomic force microscope (AFM) system cou-pled with a high resolution optical microscope (OM), which serves to observe AFM image from a desired micro-area. The system employs through-the-lens optical path for detecting atomic force based on optical lever. By switching the objective lenses from low to high magni cation, a micro-area for obtaining AFM image can be easily found. AFM images of magnetic nanodotarrays with 300 nm and 150 nm pitches are obtained from two local micro-areas using the system. The results demonstrate the proposed prototype has the su cient function to nd out a micro-area for obtaining AFM image.

In this study, we tried to develop the scanning near-field polarization microscope (SNPM) and challenge to observe magnetization of the magnetic nanodot in the arrays. The CoPt dot arrays with a size of 25 nm and a pitch of 150 nm were adopted. The nanodots change contrast after changing the direction of the external magnetic field. This implied that our prototyped SNPM system had the resolution of less than 25 nm. So, it is demonstrated that SNPM is an effective tool for the observation of magnetization of the magnetic nanodot on the nanometer scale.

The process of scanning a focused light beam by a metal-coated fiber probe with a subwavelength aperture is simulated using the finite element method for the two- and three-dimensional cases. Intensity pictures of a focal spot are obtained. For various configurations of the probes, sensitivity to electromagnetic components is investigated. Qualitative differences in the results of the two- and three-dimensional simulation are discussed. In the two-dimensional case, the probe response is found to be independent of the aperture size. However, in the three-dimensional case, the probe response depends heavily on the aperture diameter.

Summary This paper presents a method for differential magnetic force microscope imaging based on a two-pass scanning procedure to extract differential magnetic forces and eliminate or significantly reduce background forces with reversed tip magnetization. In the work, the difference of two scanned images with reversed tip magnetization was used to express the local magnetic forces. The magnetic sample was first scanned with a low lift distance between the MFM tip and the sample surface, and the magnetization direction of the probe was then changed after the first scan to perform the second scan. The differential magnetic force image was obtained through the subtraction of the two images from the two scans. The theoretical and experimental results have shown that the proposed method for differential magnetic force microscope imaging is able to reduce the effect of background or environment interference forces, and offers an improved image contrast and signal to noise ratio (SNR). SCANNING 37:112–115, 2015. © 2015 Wiley Periodicals, Inc.

Electric force microscope (EFM) testing is based on Coulombic force interactions between an EFM probe and a test point. An electric signal on an interconnected line creates an electric force between the tip and the device under test which causes a detectable bending of the cantilever. This bending amount is optically detected and electrically analyzed by a lock-in amplifier. In capacitive coupling method, an electrode is placed in close proximity to a pad on the wafer. The voltage transients on the pad induce weak displacement currents on the electrode. This effect can be used to detect electrical pulses propagating through an IC. For current measurements, scanning magnetoresistive probe has also been suggested to detect currents in a contactless manner.

It was found that the results of magnetic force microscope (MFM) imaging weredifferent with the probe scanning directions, and the images were often distorted. Thispaper studied the effect of scanning directions on the MFM imaging, and a method forthe distortion compensation was proposed to reduce the errors. In the study, threedifferent scanning directions with the angles of 0°, 45° and 90°, were used to measurethe magnetic force distribution of a magnetic sample with a regular structure. Thetheoretical and experimental results have shown that the scanning direction parallel tothe magnetic structure will cause a minimum phase shift difference and lead to a structure distortion. With the proposed compensation method, the distortion structureswere corrected and the effect of scanning directions on the MFM imaging wassignificantly reduced. This work provides a way to obtain the correct images ofmagnetic structures using an MFM and to improve the imaging quality in a wide range of MFM applications.

In this paper, a magnetic force microscope (MFM) was developed for applications in liquid environment. The 3D structure of the developed MFM system was designed first and then the components of every part were machined and assembled. The laser beam horizontally reached the mirror and reflected vertically to the cantilever of the probe to reduce the effect of air, glass and liquid refraction. This research focuses on the design of a specific MFM system to obtain the magnetic force images in liquids.

International audience; The design, fabrication and experimental validation of a novel near-field scanning millimeter-wave microscope (NSMM) built inside a scanning electron microscope (SEM) is presented. The instrument developed can perform hybrid characterizations by providing simultaneously atomic force, complex microwave impedance and electron microscopy images of a sample with nanometer spatial resolution. By combining the measured data, the system offers unprecedentable capabilities for tackling the issue between spatial resolution and high frequency quantitative measurements.

This paper presents a novel low cost three dimensional near-field scanning system consisting of a near field scanner and a three dimensional magnetic probe which reduces the large scanning time of the existing near field scanning systems and increases the spatial resolution. The paper focuses on the design, calibration and validation of a printed circuit three dimensional magnetic field probe. The proposed probe is printed on both sides an FR4 substrate of 3.2mm height. The total dimensions of the probe are 9×9×3.2mm3. The antenna factor of the designed probes is calculated using TEM cell for a frequency range from 10 MHz to 1 GHz. The proposed scanning system is validated by mapping the magnetic field above a wire over ground structure.

The method for measuring the electron distribution density in a probe of a low voltage scanning electron microscope is proposed. It is shown that a focused probe has the Gaussian shape. A defocused probe can be presented as several Gaussian probes of different intensities shifted relative to each other.

In this paper, improvement of the magnetic field detection accuracy of Scanning Hall probe microscopy (SHPM) by reducing the lift-off distance was studied. The distribution of the three dimensional residual magnetic flux density components was observed around the magnetization point on the surface of carbon tool steel at several lift-off distances ranging from 350 μm to 1500 μm. The observation at 350 μm lift-off distance achieved more 2.7 times intensity than at 1500 μm lift-off distance and a correlation between the magnetic flux density and the lift-off distance was found. Based on the 350 μm lift-off observation, a successful observation of magnetization caused by plastic deformation around the Vickers indentation was succeeded to be performed.

Methods of determining the basic metrological characteristics of a near-field scanning optical microscope, i.e., scale factor and spatial resolution, defined as the diameter of the optical probe, are proposed. The use of the proposed method for calibration of the near-field scanning optical microscope directly in the course of measurements of the parameters of biological objects is investigated.

Recently a multi-beam scanning electron microscope (MBSEM) has been developed, which delivers 196 focused beams to a sample, each of which has around 1nA. In this article a design for an optical system is described and analyzed which can focus all these beams onto a single spot, using an array of micro electron lenses. Although each individual micro lens will be of lower quality than a single macro objective lens, a system is obtained with larger beam current than the conventional SEM. The goal set in an example design is to focus a total current of 200nA within 50nm at a landing energy of 500eV.

A four-channel Kirkpatrick-Baez microscope working at multiple energy bands is developed for multiframe X-ray imaging diagnostics at the Shenguang-II laser facility. The response to the multiple energy bands is realized by coating the double-periodic multilayers on the reflected surfaces of the microscope. Because of the limited size of the microstrips in the X-ray framing camera, the image separation is controlled by the conical angle of the reference cores during microscope assembly. This study describes the optical and multilayer design, assembly, and alignment of the developed microscope. The microscope achieves a spatial resolution of 4-5 mm in the laboratory and 10-20 mm at Shenguang-II laser facility within a 300 mm field of view. The versatile nature of the developed microscope enables the multiple microscopes currently installed in the laser facility to be replaced with a single, multipurpose microscope.

Atomic force microscope (AFM) – is device widely used in many scientific fields for nano-scale surface scanning. AFM also can be used to probe mechanical stiffness, electrical conductance, resistivity, magnetism and other properties. The main limitation of AFM implementation is relatively low scanning speed. This speed depends from dynamical characteristics of AFM sensor and from surface roughness of scanned sample. Our research is focused on increasing scanning speed of AFM microscope assuming AFM mechanical sensor as sensitive dynamic system. Our proposed method enables increase of scanning speed by modifying some features of mechanical sensor by adding non-linear force to the surface of cantilever of AFM sensor. Proposed method is modelled theoretically using Simulink features. This paper presents research of mechanical sensor of AFM. After performed research, obtained results are presented on graphical form. At the end of paper discussion presented and conclusions are drawn.

A scanning probe microscope with an electrostatic force probe has been introduced for the dimensional measurement of the surface profile measurement. Since the intensity of the electrostatic force is strongly depended on the distance between a probe and the sample surface, the electrostatic force probe can be used for the measurement of the surface profile in non contact condition. In order to detect the electrostatic force between the probe tip and the sample surface, a method of the frequency modulation AFM has been employed. When the bias voltage is applied between the probe and the surface, the resonance frequency of the probe oscillation is shifted owing to the electrostatic force. In this paper, the basic characteristics of the electrostatic probe are investigated, experimentally. And then, the absolute distance between the probe tip and the sample surface is calculated by using the differences of the frequency shift of the probe. Finally, the measurement of surface profile is demonstrated in non-contact condition by utilizing the developed electrostatic force probe.

A method for measuring the scan nonlinearity of a scanning electron microscope is discussed. This method is tested using a mass-produced microscope and demonstrates good results.

The medium-term storage stability and reproducibility defined in the course of calibration of the scale factor of scanning electron microscopes are established with the use of an MShPS-2.0K measure. Conclusions are drawn to the effect that the dependence of the scale factor on the working distance may lead to some scatter of the measurement results and that direct comparison of the dimensions of the measured subject and a reference object obtained with the same parameters of the microscope is required to increase the measurement accuracy.

Known methods for determining the resolution of a scanning electron microscope are discussed. It is shown that none of them can unambiguously characterize the scanning electron microscope.

Using the microwave atomic force microscope (M-AFM) measuring system, the sample of Au nanowires arranged on glass wafer was sensed with three kinds of scanning speed. As the results shown, the spatial resolution of topographies is increased with the decrease of scanning speed. However, the precision of microwave images is not changed much with decreasing the scanning speed. Since M-AFM with the compact microwave instrument can always implement the real time measurement, the variation of scanning speed will not affect the microwave measurement.

The scan nonlinearity of scanning electron microscopes is estimated with the use of a relief element with known geometric form of the profile. The mean value of the step of the test relief structure, which is determined as a test sample is moved along the scanning axis X, is measured. It is experimentally demonstrated that with a 5× magnification, the maximum relative deviation from the mean value of the step of the test structure for a given microscope does not exceed 0.4%.

The distribution of the local current in GdBCO coated conductors was investigated using low-temperature scanning laser and Hall probe microscopy (LTSLHPM). We prepared GdBCO coated conductors to study the spatial distribution of the current density in a single bridge. Inhomogeneity in the bridge was analyzed using the experimental results of scanning laser microscopy near the superconducting transition. The local transport and screening currents in the bridge were also obtained by scanning Hall probe microscopy. From the experimental results of scanning laser and Hall probe microscopy, we have observed redistribution of the current caused by defects of the coated conductors.

The measurement of nano-scale line-width has always been important and difficult in the field of nanometer measurements, while the rapid development of integrated circuit greatly raises the demand again. As one kind of scanning probe microscope (SPM), atomic force microscope (AFM) can realize quasi three-dimensional measurement, which is widely used in nanometer scale line-width measurement. Our team researched a dual-probes atomic force microscope, which can eliminate the prevalent effect of probe width on measurement results. In dual-probes AFM system, a novel head are newly designed. A kind of self-sensing and self-exciting probes which is Nanosensors cooperation’s patented probe—Akiyama probe, is used in this novel head. The Akiyama probe applied to dual-probe atomic force microscope is one of the most important issues. The characterization of Akiyama probe would affect performance and accuracy of the whole system. The fundamental features of the Akiyama probe are electrically and optically characterized in “approach-withdraw” experiments. Further investigations include the frequency response of an Akiyama probe to small mechanical vibrations externally applied to the tip and the effective loading force yielding between the tip and the sample during the periodic contact. We hope that the characterization of the Akiyama probe described in this paper will guide application for dual-probe atomic force microscope.

International audience; A near-field scanning microwave microscope based on an interferometric technique is proposed in this work. To ensure an optimal spatial resolution, crucial parameters of the evanescent microwave probe are finely studied including the tip apex, the stand-off distance and the scanning step size. © 2016 EuMA.

In this paper the design of a new 3D magnetic field (H-field) probe with a near-field scanning system is presented. The proposed system was developed in order to determine the magnetic near-field emitted by electronic devices. The designed isotropic H-field probe consists of three orthogonal and identical loops each of diameter of 6 mm having 3 turns. The antenna factor of the designed probe is presented for a frequency range from 1 MHz to 1 GHz. In order to verify the performance of the designed probe, magnetic near-field measurements were done for a standard circuit. The comparison between the measured results and the theoretical calculations was performed for validation.

This paper presents an assembled comb-drive XYZ-microstage with large displacements for the scanning of magnetic resonance force microscopy (MRFM) at cryogenic environment. The scanning XYZ-microstage with little affection to the thermal variation and magnetic fields is required. The comb-drive XYZ-microstage is assembled with an XY-microstage, two Z-actuators and a silicon base substrate using a microassembly technology. For measurements, a sample of 1, 1-Diphenyl-2-picrylhydrazyl radical (DPPH) is glued onto the assembled XYZ-microstage. The imaging system is consisted of the scanning XYZ-microstage with DPPH sample, a sensitive cantilever sensor with a small magnetic particle, a fiber-optic interferometer to detect the vibration of the cantilever and a radio frequency (RF) coil. The measurements are performed at low pressure in a vacuum chamber. The vibration of the cantilever sensor based on magnetic force from electron spin resonance (ESR) spectroscopy can be detected through adjusting the magnetic field intensity of the RF coil.

We report on the design and performance of a high stability scanning confocal microscope for optical microscopy at low temperatures. By scanning the beam in a cold objective lens system, we achieve wide fields of view without compromising image quality. Photoluminescence from single nitrogen-vacancy centers in high purity diamond is used to illustrate the imaging and stability performance of the microscope. © 2010 American Institute of Physics.

Scanning Hall probe microscopy is a widely used technique for quantitative high resolution imaging of magnetic stray fields. Up to now probes with nanometer spatial resolution have only been realized by electron beam lithography, which is a slow and expensive fabrication technique. In this thesis, we employ corner lithography to enable batch fabrication of high resolution scanning Hall probes. The initial design consisted of a sub-&m Hall cross supported by four free standing wires in a pyramidal configuration, located at the end of an AFMtype cantilever. This implementation was mechanically and electrically too fragile to operate. Therefore the design was improved by supporting the wires with a robust silicon-nitride membrane. These robust probes allowed for scanning operation, but we discovered that the output signals suffered from large topographic crosstalk. We determined that this crosstalk was caused by the combination of cross asymmetry, resulting from fabrication imperfections, and topography induced probe-sample distance modulation, leading to temperature variation. To circumvent the crosstalk, we introduced an electronic compensation method to suppress the effect of temperature variation on the detected Hall signal. The method suppresses the temperature effect by at least a factor of ten, provided that the probe temperature varies uniformly over the entire structure. However, the method is not capable of compensating temperature changes within the probe structure itself, for instance caused by asymmetric probe cooling at step edges on the sample, or cantilever torsion. To increase the signal-to-noise ratio and improve the electrical robustness of the probes even more, we improved the probe design further by widening the leads to the Hall cross and increasing its dimensions. Using this final design, we successfully demonstrated imaging on a thermo-magnetically patterned magnetic sample with domains of 10 &m£10 &m, at a sensitivity of 4.12 V/T.

In this paper cantilever detection methods of microscopy that allow to get an image of surface with high spatial resolution are discussed. The functionality of the scanning tunneling microscope and principle of its operation are analyzed. Basing on the simulated data, it is possible to show how microscope operating parameters affect the results of its measurements.

This paper reports the first single-chip scanning probe microscope (sc-SPM) that is capable of simultaneously performing atomic force microscopy (AFM) and scanning thermal microscopy (SThM) without requiring any off-chip scanning or sensing components. A thermal-piezoresistive resonant sensor is used to hold the tip-sample interaction force constant, while a bolometer-style probe measures local heat transfer effects. The reported instrument obtains local thermal measurements of powered electrothermal MEMS devices and also achieves the first patterning results with a single-chip scanning probe instrument. Importantly, subsurface features on a 22nm CMOS chip are revealed by thermal phase imaging with the present device.