A portable Hall magnetometer probe for characterization of magnetic iron oxide nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Araujo, Jefferson F.D.F.; Costa, Mateus C.; Louro, Sonia R.W.; Bruno, Antonio C., E-mail: acbruno@puc-rio.br

2017-03-15

We have built a portable Hall magnetometer probe, for measuring magnetic properties of iron oxide nanoparticles, that can be used for bulk materials and liquid samples as well. The magnetometer probe consists of four voltage-programmable commercial Hall sensors and a thin acrylic plate for positioning the sensors. In order to operate, it needs to be attached to a pole of an electromagnet and connected to an AD converter and a computer. It acquires a complete magnetization curve in a couple of minutes and has a magnetic moment sensitivity of 3.5×10{sup −7} Am{sup 2}. We tested its performance with magnetic nanoparticles containing an iron oxide core and having coating layers with different sizes. The magnetization results obtained were compared with measurements performed on commercial stand-alone magnetometers, and exhibited errors of about ±0.2 Am{sup 2}/kg (i.e 0.4%) at saturation and below 0.5 Am{sup 2}/kg (i.e. 10%) at remanence. - Highlights: • A low-cost portable Hall magnetometer probe has been built. • The Hall magnetometer probe can be attached to any electromagnet. • The Hall probe was calibrated and successfully compared to industry standard magnetometers. • The Hall probe was able to measure iron oxide nanoparticles with different coatings.

A portable Hall magnetometer probe for characterization of magnetic iron oxide nanoparticles

International Nuclear Information System (INIS)

Araujo, Jefferson F.D.F.; Costa, Mateus C.; Louro, Sonia R.W.; Bruno, Antonio C.

2017-01-01

We have built a portable Hall magnetometer probe, for measuring magnetic properties of iron oxide nanoparticles, that can be used for bulk materials and liquid samples as well. The magnetometer probe consists of four voltage-programmable commercial Hall sensors and a thin acrylic plate for positioning the sensors. In order to operate, it needs to be attached to a pole of an electromagnet and connected to an AD converter and a computer. It acquires a complete magnetization curve in a couple of minutes and has a magnetic moment sensitivity of 3.5×10 −7 Am 2 . We tested its performance with magnetic nanoparticles containing an iron oxide core and having coating layers with different sizes. The magnetization results obtained were compared with measurements performed on commercial stand-alone magnetometers, and exhibited errors of about ±0.2 Am 2 /kg (i.e 0.4%) at saturation and below 0.5 Am 2 /kg (i.e. 10%) at remanence. - Highlights: • A low-cost portable Hall magnetometer probe has been built. • The Hall magnetometer probe can be attached to any electromagnet. • The Hall probe was calibrated and successfully compared to industry standard magnetometers. • The Hall probe was able to measure iron oxide nanoparticles with different coatings.

Four-probe measurements with a three-probe scanning tunneling microscope

International Nuclear Information System (INIS)

Salomons, Mark; Martins, Bruno V. C.; Zikovsky, Janik; Wolkow, Robert A.

2014-01-01

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe

Four-probe measurements with a three-probe scanning tunneling microscope

Energy Technology Data Exchange (ETDEWEB)

Salomons, Mark [National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta T6G 2M9 (Canada); Martins, Bruno V. C.; Zikovsky, Janik; Wolkow, Robert A., E-mail: rwolkow@ualberta.ca [National Institute for Nanotechnology, National Research Council of Canada, Edmonton, Alberta T6G 2M9 (Canada); Department of Physics, University of Alberta, Edmonton, Alberta T6G 2E1 (Canada)

2014-04-15

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.

Four-probe measurements with a three-probe scanning tunneling microscope.

Science.gov (United States)

Salomons, Mark; Martins, Bruno V C; Zikovsky, Janik; Wolkow, Robert A

2014-04-01

We present an ultrahigh vacuum (UHV) three-probe scanning tunneling microscope in which each probe is capable of atomic resolution. A UHV JEOL scanning electron microscope aids in the placement of the probes on the sample. The machine also has a field ion microscope to clean, atomically image, and shape the probe tips. The machine uses bare conductive samples and tips with a homebuilt set of pliers for heating and loading. Automated feedback controlled tip-surface contacts allow for electrical stability and reproducibility while also greatly reducing tip and surface damage due to contact formation. The ability to register inter-tip position by imaging of a single surface feature by multiple tips is demonstrated. Four-probe material characterization is achieved by deploying two tips as fixed current probes and the third tip as a movable voltage probe.

Investigations of Probe Induced Perturbations in a Hall Thruster

International Nuclear Information System (INIS)

D. Staack; Y. Raitses; N.J. Fisch

2002-01-01

An electrostatic probe used to measure spatial plasma parameters in a Hall thruster generates perturbations of the plasma. These perturbations are examined by varying the probe material, penetration distance, residence time, and the nominal thruster conditions. The study leads us to recommendations for probe design and thruster operating conditions to reduce discharge perturbations, including metal shielding of the probe insulator and operation of the thruster at lower densities

Scanning microscopic four-point conductivity probes

DEFF Research Database (Denmark)

Petersen, Christian Leth; Hansen, Torben Mikael; Bøggild, Peter

2002-01-01

A method for fabricating microscopic four-point probes is presented. The method uses silicon-based microfabrication technology involving only two patterning steps. The last step in the fabrication process is an unmasked deposition of the conducting probe material, and it is thus possible to select...... the conducting material either for a silicon wafer or a single probe unit. Using shadow masking photolithography an electrode spacing (pitch) down to 1.1 mum was obtained, with cantilever separation down to 200 run. Characterisation measurements have shown the microscopic probes to be mechanically very flexible...

Two-probe atomic-force microscope manipulator and its applications

Science.gov (United States)

Zhukov, A. A.; Stolyarov, V. S.; Kononenko, O. V.

2017-06-01

We report on a manipulator based on a two-probe atomic force microscope (AFM) with an individual feedback system for each probe. This manipulator works under an upright optical microscope with 3 mm focal distance. The design of the microscope helps us tomanipulate nanowires using the microscope probes as a two-prong fork. The AFM feedback is realized based on the dynamic full-time contact mode. The applications of the manipulator and advantages of its two-probe design are presented.

Two-probe atomic-force microscope manipulator and its applications.

Science.gov (United States)

Zhukov, A A; Stolyarov, V S; Kononenko, O V

2017-06-01

We report on a manipulator based on a two-probe atomic force microscope (AFM) with an individual feedback system for each probe. This manipulator works under an upright optical microscope with 3 mm focal distance. The design of the microscope helps us tomanipulate nanowires using the microscope probes as a two-prong fork. The AFM feedback is realized based on the dynamic full-time contact mode. The applications of the manipulator and advantages of its two-probe design are presented.

A quadruple-scanning-probe force microscope for electrical property measurements of microscopic materials

International Nuclear Information System (INIS)

Higuchi, Seiji; Kubo, Osamu; Kuramochi, Hiromi; Aono, Masakazu; Nakayama, Tomonobu

2011-01-01

Four-terminal electrical measurement is realized on a microscopic structure in air, without a lithographic process, using a home-built quadruple-scanning-probe force microscope (QSPFM). The QSPFM has four probes whose positions are individually controlled by obtaining images of a sample in the manner of atomic force microscopy (AFM), and uses the probes as contacting electrodes for electrical measurements. A specially arranged tuning fork probe (TFP) is used as a self-detection force sensor to operate each probe in a frequency modulation AFM mode, resulting in simultaneous imaging of the same microscopic feature on an insulator using the four TFPs. Four-terminal electrical measurement is then demonstrated in air by placing each probe electrode in contact with a graphene flake exfoliated on a silicon dioxide film, and the sheet resistance of the flake is measured by the van der Pauw method. The present work shows that the QSPFM has the potential to measure the intrinsic electrical properties of a wide range of microscopic materials in situ without electrode fabrication.

Some aspects of achieving an ultimate accuracy during insertion device magnetic measurements by a Hall probe

International Nuclear Information System (INIS)

Vasserman, I. B.; Xu, J. Z.; Strelnikov, N. O.

2013-01-01

An extensive test of a new Senis 2-axis Hall probe was done at the Advanced Photon Source using the Undulator A device and calibration system. This new probe has clear advantages compared with previously used Bell and Sentron Hall probes: very stable zero offset (less than the noise of 0.026 G) and compensated planar Hall effect. It can be used with proper calibration even for first and second field integral measurements. A comparison with reference measurements by long stretched coil shows that the difference in the first field integral measurement results for a 2.4-m-long Undulator A device is between 17 G cm for the best of four Hall probes used for the test and 51 G cm for the worst of them for all gap ranges from 10.5 mm to 150 mm.

Measuring the homogeneity of Bi(2223)/Ag tapes by four-probe method and a Hall probe array

International Nuclear Information System (INIS)

Kovac, P.

1999-01-01

The nature of the BSCCO compound and application of the powder-in-tube technique usually lead to non-uniform quality across and/or along the ceramic fibres and finally to variations in the critical current and its irregular distribution in the Bi(2223)/Ag tape. Therefore, the gliding four-probe method and contactless field monitoring measurements have been used for homogeneity studies. The gliding potential contacts moved along the tape surface and a sensitive system based on an integrated Hall probe array containing 16 or 19 in-line probes supported by PC-compatible electronics with software allowed us to make a comparison of contact and contactless measurements at any elements of Bi(2223)/Ag sample. The results of both methods show very good correlation and the possibility of using a sensitive Hall probe array for monitoring the final quality of Bi(2223)/Ag tapes. (author)

Analysis of Hall Probe Precise Positioning with Cylindrical Permanent Magnet

International Nuclear Information System (INIS)

Belicev, P.; Vorozhtsov, A.S.; Vorozhtsov, S.B.

2007-01-01

Precise positioning of a Hall probe for cyclotron magnetic field mapping, using cylindrical permanent magnets, was analyzed. The necessary permanent magnet parameters in order to achieve ±20 μm position precision, were determined. (author)

Improved controlled atmosphere high temperature scanning probe microscope

DEFF Research Database (Denmark)

Hansen, Karin Vels; Wu, Yuehua; Jacobsen, Torben

2013-01-01

fuel cells and electrolyzer cells. Here, we report on advanced improvements of our original controlled atmosphere high temperature scanning probe microscope, CAHT-SPM. The new microscope can employ a broad range of the scanning probe techniques including tapping mode, scanning tunneling microscopy......, scanning tunneling spectroscopy, conductive atomic force microscopy, and Kelvin probe force microscopy. The temperature of the sample can be as high as 850 °C. Both reducing and oxidizing gases such as oxygen, hydrogen, and nitrogen can be added in the sample chamber and the oxygen partial pressure (pO2...

Multiple-scanning-probe tunneling microscope with nanoscale positional recognition function.

Science.gov (United States)

Higuchi, Seiji; Kuramochi, Hiromi; Laurent, Olivier; Komatsubara, Takashi; Machida, Shinichi; Aono, Masakazu; Obori, Kenichi; Nakayama, Tomonobu

2010-07-01

Over the past decade, multiple-scanning-probe microscope systems with independently controlled probes have been developed for nanoscale electrical measurements. We developed a quadruple-scanning-probe tunneling microscope (QSPTM) that can determine and control the probe position through scanning-probe imaging. The difficulty of operating multiple probes with submicrometer precision drastically increases with the number of probes. To solve problems such as determining the relative positions of the probes and avoiding of contact between the probes, we adopted sample-scanning methods to obtain four images simultaneously and developed an original control system for QSPTM operation with a function of automatic positional recognition. These improvements make the QSPTM a more practical and useful instrument since four images can now be reliably produced, and consequently the positioning of the four probes becomes easier owing to the reduced chance of accidental contact between the probes.

Magnetically filtered Faraday probe for measuring the ion current density profile of a Hall thruster

International Nuclear Information System (INIS)

Rovey, Joshua L.; Walker, Mitchell L.R.; Gallimore, Alec D.; Peterson, Peter Y.

2006-01-01

The ability of a magnetically filtered Faraday probe (MFFP) to obtain the ion current density profile of a Hall thruster is investigated. The MFFP is designed to eliminate the collection of low-energy, charge-exchange (CEX) ions by using a variable magnetic field as an ion filter. In this study, a MFFP, Faraday probe with a reduced acceptance angle (BFP), and nude Faraday probe are used to measure the ion current density profile of a 5 kW Hall thruster operating over the range of 300-500 V and 5-10 mg/s. The probes are evaluated on a xenon propellant Hall thruster in the University of Michigan Large Vacuum Test Facility at operating pressures within the range of 4.4x10 -4 Pa Xe (3.3x10 -6 Torr Xe) to 1.1x10 -3 Pa Xe (8.4x10 -6 Torr Xe) in order to study the ability of the Faraday probe designs to filter out CEX ions. Detailed examination of the results shows that the nude probe measures a greater ion current density profile than both the MFFP and BFP over the range of angular positions investigated for each operating condition. The differences between the current density profiles obtained by each probe are attributed to the ion filtering systems employed. Analysis of the results shows that the MFFP, operating at a +5 A solenoid current, provides the best agreement with flight-test data and across operating pressures

Scanning Hall-probe microscopy of a vortex and field fluctuations in La1.85Sr0.15CuO4 films

International Nuclear Information System (INIS)

Chang, A.M.; Hallen, H.D.; Hess, H.F.; Kwo, J.; Sudboe, A.; Kao, H.L.; Chang, T.Y.

1992-01-01

A high-resolution scanning Hall-probe microscope is used to spatially resolve vortices in high-temperature superconducting La 1.85 Sr 0.15 CuO 4 films. At low magnetic fields, a disordered vortex arrangement is observed. A fit to the surface field of an individual vortex is consistent with one flux quantum, and is used to determine the local penetration depth and its temperature dependence. At higher fields, magnetic fluctuations are observed and compared to a collective pinning model. For films grown with the c-axis tilted from the surface normal, oval vortices are observed. (orig.)

Image processing for HTS SQUID probe microscope

International Nuclear Information System (INIS)

Hayashi, T.; Koetitz, R.; Itozaki, H.; Ishikawa, T.; Kawabe, U.

2005-01-01

An HTS SQUID probe microscope has been developed using a high-permeability needle to enable high spatial resolution measurement of samples in air even at room temperature. Image processing techniques have also been developed to improve the magnetic field images obtained from the microscope. Artifacts in the data occur due to electromagnetic interference from electric power lines, line drift and flux trapping. The electromagnetic interference could successfully be removed by eliminating the noise peaks from the power spectrum of fast Fourier transforms of line scans of the image. The drift between lines was removed by interpolating the mean field value of each scan line. Artifacts in line scans occurring due to flux trapping or unexpected noise were removed by the detection of a sharp drift and interpolation using the line data of neighboring lines. Highly detailed magnetic field images were obtained from the HTS SQUID probe microscope by the application of these image processing techniques

Electrical conduction through surface superstructures measured by microscopic four-point probes

DEFF Research Database (Denmark)

Hasegawa, S.; Shiraki, I.; Tanabe, F.

2003-01-01

For in-situ measurements of the local electrical conductivity of well-defined crystal surfaces in ultra-high vacuum, we have developed two kinds of microscopic four-point probe methods. One involves a "four-tip STM prober," in which four independently driven tips of a scanning tunneling microscope...... (STM) are used for measurements of four-point probe conductivity. The probe spacing can be changed from 500 nm to 1 mm. The other method involves monolithic micro-four-point probes, fabricated on silicon chips, whose probe spacing is fixed around several mum. These probes are installed in scanning...

Expectations for neutrons as microscopic probes

International Nuclear Information System (INIS)

Date, M.

1993-01-01

Neutrons have been used as microscopic probes to study structural and dynamical properties of various materials. In this paper I shall give a comparative study of the neutron research in the condensed matter physics with other typical microscopic methods such as X-rays, laser optics, magnetic resonances, Moessbauer effect and μSR. It is emphasized that the neutron study will extensively be important in future beyond the condensed matter physics. Chemistry, biology, earth sciences, material engineerings and medical sciences will become new frontiers for neutron study. (author)

An Evanescent Field Optical Microscope. Scanning probe Microscopy

NARCIS (Netherlands)

van Hulst, N.F.; Segerink, Franciscus B.; Bölger, B.; Bölger, B.; Wickramasinghe, H. Kumar

1991-01-01

An Evanescent Field Optical Microscope (EFOM) is presented, which employs frustrated total internal reflection on a highly localized scale by means of a sharp dielectric tip. The coupling of the evanescent field to the sub-micrometer probe as a function of probe-sample distance, angle of incidence

Muon spin rotation and other microscopic probes of spin-glass dynamics

International Nuclear Information System (INIS)

MacLaughlin, D.E.

1980-01-01

A number of different microscopic probe techniques have been employed to investigate the onset of the spin-glass state in dilute magnetic alloys. Among these are Moessbauer-effect spectroscopy, neutron scattering, ESR of the impurity spins, host NMR and, most recently, muon spin rotation and depolarization. Spin probes yield information on the microscopic static and dynamic behavior of the impurity spins, and give insight into both the spin freezing process and the nature of low-lying excitations in the ordered state. Microscopic probe experiments in spin glasses are surveyed, and the unique advantages of muon studies are emphasized

Novel scanning probe microscope instrumentation with applications in nanotechnology

International Nuclear Information System (INIS)

Humphry, M.J.

2000-10-01

A versatile scanning probe microscope controller has been constructed. Its suitability for the control of a range of different scanning probe microscope heads has been demonstrated. These include an ultra high vacuum scanning tunnelling microscope, with which atomic resolution images of Si surfaces was obtained, a custom-built atomic force microscope, and a custom-built photon emission scanning tunnelling microscope. The controller has been designed specifically to facilitate data acquisition during molecular manipulation experiments. Using the controller, the fullerene molecule C 60 has been successfully manipulated on Si(100)-2x1 surfaces and detailed data has been acquired during the manipulation process. Evidence for two distinct modes of manipulation have been observed. A repulsive mode with success rates up to 90% was found to occur with tunnel gap impedances below 2GΩ, while between 2GΩ and 8GΩ attractive manipulation events were observed, with a maximum success rate of ∼8%. It was also found that the step size between feedback updates had a significant effect on tip stability, and that dwell time of the STM tip at each data point had a critical effect on manipulation probability. A multi-function scanning probe microscope head has been developed capable of operation as a scanning tunnelling microscope and an atomic force microscope in vacuum and a magnetic field of 7T. The custom-built controller also presented here was used to control the head. A three-axis inertial sliding motor was developed for the head, capable of reproducible step sizes of <1000A. In addition, an optical fibre interferometer was constructed with a sensitivity of 0.2A/√Hz. Preliminary development of a magnetic resonance force microscope mode has also been performed, with initial results showing such a system to be feasible. (author)

A New Method for Analyzing Near-Field Faraday Probe Data in Hall Thrusters

Science.gov (United States)

Huang, Wensheng; Shastry, Rohit; Herman, Daniel A.; Soulas, George C.; Kamhawi, Hani

2013-01-01

This paper presents a new method for analyzing near-field Faraday probe data obtained from Hall thrusters. Traditional methods spawned from far-field Faraday probe analysis rely on assumptions that are not applicable to near-field Faraday probe data. In particular, arbitrary choices for the point of origin and limits of integration have made interpretation of the results difficult. The new method, called iterative pathfinding, uses the evolution of the near-field plume with distance to provide feedback for determining the location of the point of origin. Although still susceptible to the choice of integration limits, this method presents a systematic approach to determining the origin point for calculating the divergence angle. The iterative pathfinding method is applied to near-field Faraday probe data taken in a previous study from the NASA-300M and NASA-457Mv2 Hall thrusters. Since these two thrusters use centrally mounted cathodes the current density associated with the cathode plume is removed before applying iterative pathfinding. A procedure is presented for removing the cathode plume. The results of the analysis are compared to far-field probe analysis results. This paper ends with checks on the validity of the new method and discussions on the implications of the results.

Measurement of Safety Factor Using Hall Probes on CASTOR Tokamak

Czech Academy of Sciences Publication Activity Database

Kovařík, Karel; Ďuran, Ivan; Bolshakova, I.; Holyaka, R.; Erashok, V.

2006-01-01

Roč. 56, suppl.B (2006), s. 104-110 ISSN 0011-4626. [Symposium on Plasma Physics and Technology/22nd./. Praha, 26.6.2006-29.6.2006] R&D Projects: GA AV ČR(CZ) KJB100430504 Institutional research plan: CEZ:AV0Z20430508 Keywords : Plasma * tokamak * safety factor * hall probe Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 0.568, year: 2006

Near-field optical microscope using a silicon-nitride probe

NARCIS (Netherlands)

van Hulst, N.F.; Moers, M.H.P.; Moers, M.H.P.; Noordman, O.F.J.; Noordman, O.F.J.; Tack, R.G.; Segerink, Franciscus B.; Bölger, B.; Bölger, B.

1993-01-01

Operation of an alternative near-field optical microscope is presented. The microscope uses a microfabricated silicon- nitride probe with integrated cantilever, as originally developed for force microscopy. The cantilever allows routine close contact near-field imaging o­n arbitrary surfaces without

High precision micro-scale Hall Effect characterization method using in-line micro four-point probes

DEFF Research Database (Denmark)

Petersen, Dirch Hjorth; Hansen, Ole; Lin, Rong

2008-01-01

Accurate characterization of ultra shallow junctions (USJ) is important in order to understand the principles of junction formation and to develop the appropriate implant and annealing technologies. We investigate the capabilities of a new micro-scale Hall effect measurement method where Hall...... effect is measured with collinear micro four-point probes (M4PP). We derive the sensitivity to electrode position errors and describe a position error suppression method to enable rapid reliable Hall effect measurements with just two measurement points. We show with both Monte Carlo simulations...... and experimental measurements, that the repeatability of a micro-scale Hall effect measurement is better than 1 %. We demonstrate the ability to spatially resolve Hall effect on micro-scale by characterization of an USJ with a single laser stripe anneal. The micro sheet resistance variations resulting from...

Soft control of scanning probe microscope with high flexibility.

Science.gov (United States)

Liu, Zhenghui; Guo, Yuzheng; Zhang, Zhaohui; Zhu, Xing

2007-01-01

Most commercial scanning probe microscopes have multiple embedded digital microprocessors and utilize complex software for system control, which is not easily obtained or modified by researchers wishing to perform novel and special applications. In this paper, we present a simple and flexible control solution that just depends on software running on a single-processor personal computer with real-time Linux operating system to carry out all the control tasks including negative feedback, tip moving, data processing and user interface. In this way, we fully exploit the potential of a personal computer in calculating and programming, enabling us to manipulate the scanning probe as required without any special digital control circuits and related technical know-how. This solution has been successfully applied to a homemade ultrahigh vacuum scanning tunneling microscope and a multiprobe scanning tunneling microscope.

Characterization of coating probe with Ti-DLC for electrical scanning probe microscope

International Nuclear Information System (INIS)

Shia Xiaolei; Guo Liqiu; Bai Yang; Qiao Lijie

2011-01-01

In electrical scanning probe microscope (ESPM) applications, the wear and conductivity of the probe are undoubtedly serious concerns since they affect the integrity of the measurements. This study investigates the characterization of Ti doped diamond-like-carbon (DLC) as coating material on a silicon cantilever for ESPM. We deposited a layer of Ti-DLC thin film on the surface of Si cantilever by magnetron sputtering. The morphology and composition of the Ti-DLC films were characterized by scanning electron microscopy and Raman spectroscopy, respectively. We also compared the wear resistance, electric conductivity and scanning image quality of the Ti-DLC-coated probes with those of commercially available conductive probes. The results showed that the electric conductivity and the scanning image quality of the Ti-DLC-coated probes were the same as the commercial conductive probes, while the wear resistance and service life was significantly better.

Probing thermal evanescent waves with a scattering-type near-field microscope

International Nuclear Information System (INIS)

Kajihara, Y; Kosaka, K; Komiyama, S

2011-01-01

Long wavelength infrared (LWIR) waves contain many important spectra of matters like molecular motions. Thus, probing spontaneous LWIR radiation without external illumination would reveal detailed mesoscopic phenomena that cannot be probed by any other measurement methods. Here we developed a scattering-type scanning near-field optical microscope (s-SNOM) and demonstrated passive near-field microscopy at 14.5 µm wavelength. Our s-SNOM consists of an atomic force microscope and a confocal microscope equipped with a highly sensitive LWIR detector, called a charge-sensitive infrared phototransistor (CSIP). In our s-SNOM, photons scattered by a tungsten probe are collected by an objective of the confocal LWIR microscope and are finally detected by the CSIP. To suppress the far-field background, we vertically modulated the probe and demodulated the signal with a lock-in amplifier. With the s-SNOM, a clear passive image of 3 µm pitch Au/SiC gratings was successfully obtained and the spatial resolution was estimated to be 60 nm (λ/240). The radiation from Au and GaAs was suggested to be due to thermally excited charge/current fluctuations and surface phonons, respectively. This s-SNOM has the potential to observe mesoscopic phenomena such as molecular motions, biomolecular protein interactions and semiconductor conditions in the future

Direct measurement of surface-state conductance by microscopic four-point probe method

DEFF Research Database (Denmark)

Hasegawa, S.; Shiraki, I.; Tanikawa, T.

2002-01-01

For in situ measurements of local electrical conductivity of well defined crystal surfaces in ultrahigh vacuum, we have developed microscopic four-point probes with a probe spacing of several micrometres, installed in a scanning-electron - microscope/electron-diffraction chamber. The probe...... is precisely positioned on targeted areas of the sample surface by using piezoactuators. This apparatus enables conductivity measurement with extremely high surface sensitivity, resulting in direct access to surface-state conductivity of the surface superstructures, and clarifying the influence of atomic steps...

Distribution Analysis of the Local Critical Temperature and Current Density in YBCO Coated Conductors using Low-temperature Scanning Laser and Hall Probe Microscopy

International Nuclear Information System (INIS)

Park, S. K.; Cho, B. R.; Park, H. Y.; Ri, H. C.

2011-01-01

Distribution of the local critical temperature and current density in YBCO coated conductors were analyzed using Low-temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). We prepared YBCO coated conductors of various bridge types to study the spatial distribution of the critical temperature and the current density in single and multi bridges. LTSLHPM system was modified for detailed linescan or two-dimensional scan both scanning laser and scanning Hall probe method simultaneously. We analyzed the local critical temperature of single and multi bridges from series of several linescans of scanning laser microscopy. We also investigated local current density and hysteresis curve of single bridge from experimental results of scanning Hall probe microscopy.

Optical and electrical characterization at the nanoscale with a transparent probe of a scanning tunnelling microscope

International Nuclear Information System (INIS)

Sychugov, Ilya; Omi, Hiroo; Murashita, Tooru; Kobayashi, Yoshihiro

2009-01-01

A new type of scanning probe microscope, combining features of the scanning tunnelling microscope, the scanning tunnelling luminescence microscope with a transparent probe and the aperture scanning near-field optical microscope, is described. Proof-of-concept experiments were performed under ultrahigh vacuum conditions at varying temperature on GaAs/AlAs heterostructures.

Probing Field Distributions on Waveguide Structures with an Atomic Force/Photon Scanning Tunneling Microscope

NARCIS (Netherlands)

Borgonjen, E.G.; Borgonjen, E.G.; Moers, M.H.P.; Moers, M.H.P.; Ruiter, A.G.T.; van Hulst, N.F.

1995-01-01

A 'stand-alone' Photon Scanning Tunneling Microscope combined with an Atomic force Microscope, using a micro-fabricated silicon-nitride probe, is applied to the imaging of field distribution in integrated optical ridge waveguides. The electric field on the waveguide is locally probed by coupling to

Imaging of Coulomb-Driven Quantum Hall Edge States

KAUST Repository

Lai, Keji

2011-10-01

The edges of a two-dimensional electron gas (2DEG) in the quantum Hall effect (QHE) regime are divided into alternating metallic and insulating strips, with their widths determined by the energy gaps of the QHE states and the electrostatic Coulomb interaction. Local probing of these submicrometer features, however, is challenging due to the buried 2DEG structures. Using a newly developed microwave impedance microscope, we demonstrate the real-space conductivity mapping of the edge and bulk states. The sizes, positions, and field dependence of the edge strips around the sample perimeter agree quantitatively with the self-consistent electrostatic picture. The evolution of microwave images as a function of magnetic fields provides rich microscopic information around the ν=2 QHE state. © 2011 American Physical Society.

The current distribution in Bi-2223/Ag HTS conductors: comparing Hall probe and magnetic knife

NARCIS (Netherlands)

Demencik, E.; Dhalle, Marc M.J.; ten Kate, Herman H.J.; Polak, M.

2006-01-01

We analyzed the current distribution in three Bi-2223/Ag tapes with different filament lay-out, comparing the results of magnetic knife and Hall probe experiments. Detailed knowledge of the current distribution can be useful for the diagnostics of HTS conductors. The lateral current distribution was

Design and development of a 3 axis magnetic field measurement facility using Hall probe

International Nuclear Information System (INIS)

Sahoo, Shantonu; Bhattacharyya, Sumantra; Chaddha, Niraj; Mishra, Santosh Kr.; Nandy, Partha P.; Nandi, Chinmay; Bhole, Rajendra B.; Pal, Sarbajit; Pal, Gautam

2015-01-01

A 3-axis drive system has been designed and developed in-house to measure the magnetic field with positional accuracy of 0.2 mm in a volume of 1.5 x 1.3 x 0.15 cubic-meter. Hall sensor based magnetometer is used to measure the magnetic field with a precision of 100 μT(1 Gauss). The drive of each axis has linear guide and zero backlash ball screw combination to achieve accurate movement of the hall probe with positional repeatability of +/- 0.2 micron per 50 mm. The hardware and software, also developed in-house, facilitate precise probe positioning and sophisticated visualization of field map. Dedicated microcontroller based motor controllers and encoder read-out cards for each axis have been developed. The facility is integrated with a rich touch-screen based intelligent GUI for automated scanning and data acquisition. This facility can be used for accurate magnetic field mapping of big dipole magnets, solenoids, etc. The facility has been tested successfully to characterize a Dipole Magnet designed for Radioactive Ion Beam (RIB) facility. (author)

Assessment of bilayer silicene to probe as quantum spin and valley Hall effect

Science.gov (United States)

Rehman, Majeed Ur; Qiao, Zhenhua

2018-02-01

Silicene takes precedence over graphene due to its buckling type structure and strong spin orbit coupling. Motivated by these properties, we study the silicene bilayer in the presence of applied perpendicular electric field and intrinsic spin orbit coupling to probe as quantum spin/valley Hall effect. Using analytical approach, we calculate the spin Chern-number of bilayer silicene and then compare it with monolayer silicene. We reveal that bilayer silicene hosts double spin Chern-number as compared to single layer silicene and therefore accordingly has twice as many edge states in contrast to single layer silicene. In addition, we investigate the combined effect of intrinsic spin orbit coupling and the external electric field, we find that bilayer silicene, likewise single layer silicene, goes through a phase transitions from a quantum spin Hall state to a quantum valley Hall state when the strength of the applied electric field exceeds the intrinsic spin orbit coupling strength. We believe that the results and outcomes obtained for bilayer silicene are experimentally more accessible as compared to bilayer graphene, because of strong SO coupling in bilayer silicene.

A new theoretical probe for the magnetic force microscope

Energy Technology Data Exchange (ETDEWEB)

Windmill, J.F.C. E-mail: jwindmill@plymouth.ac.uk; Clegg, W.W.; Jenkins, D.F.L.; Davey, P.J

2001-05-01

The magnetic force microscope (MFM) is established as a valuable tool for the analysis of magnetic structures. The standard design of MFM incorporates a silicon tip coated with a magnetic material. However, these tips are subject to several inherent problems, e.g. changing characteristics over time due to damage or magnetic hysteresis. A new theoretical electromagnetic MFM probe is introduced here. Although electromagnetic MFM has been discussed before by Zhou et al. (J. Vac. Sci. Technol. A 17 (1999) 2233), the design presented here is a different approach. Two different probe iterations and their magnetic field intensity distribution are modelled. The probe imaging capability is compared using the reciprocity principle (Wright and Hill, Appl. Phys. Lett. 68 (1996) 1726) to image the simulated force interaction between a sample and the probe fields. Thus, images of a sample's magnetic distribution are produced by the convolution of the different probe gradient field distributions and the sample magnetisation. Both perpendicular and longitudinal magnetisation patterns were simulated with the different probe iterations. This clearly showed the improvement of the second probe iteration, particularly for longitudinal patterns. The practical use of the new probe is also discussed, and future work outlined.

Magnetically Filtered Faraday Probe for Measuring the Ion Current Density Profile of a Hall Thruster

National Research Council Canada - National Science Library

Rovey, Joshua L; Walker, Mitchell L. R; Gallimore, Alec D; Peterson, Peter Y

2006-01-01

.../s. The probes are evaluated on a xenon propellant Hall thruster in the University of Michigan Large Vacuum Test Facility at operating pressures within the range of 4.4 x 10(-4) Pa Xe (3.3 x 10(-6) Torr Xe) to 1.1 10(-3) Pa Xe (8.4 x 10(-6) Torr Xe...

The Scanning Theremin Microscope: A Model Scanning Probe Instrument for Hands-On Activities

Science.gov (United States)

Quardokus, Rebecca C.; Wasio, Natalie A.; Kandel, S. Alex

2014-01-01

A model scanning probe microscope, designed using similar principles of operation to research instruments, is described. Proximity sensing is done using a capacitance probe, and a mechanical linkage is used to scan this probe across surfaces. The signal is transduced as an audio tone using a heterodyne detection circuit analogous to that used in…

Resolution enhancement of pump-probe microscope with an inverse-annular filter

Science.gov (United States)

Kobayashi, Takayoshi; Kawasumi, Koshi; Miyazaki, Jun; Nakata, Kazuaki

2018-04-01

Optical pump-probe microscopy can provide images by detecting changes in probe light intensity induced by stimulated emission, photoinduced absorbance change, or photothermal-induced refractive index change in either transmission or reflection mode. Photothermal microscopy, which is one type of optical pump-probe microscopy, has intrinsically super resolution capability due to the bilinear dependence of signal intensity of pump and probe. We introduce new techniques for further resolution enhancement and fast imaging in photothermal microscope. First, we introduce a new pupil filter, an inverse-annular pupil filter in a pump-probe photothermal microscope, which provides resolution enhancement in three dimensions. The resolutions are proved to be improved in lateral and axial directions by imaging experiment using 20-nm gold nanoparticles. The improvement in X (perpendicular to the common pump and probe polarization direction), Y (parallel to the polarization direction), and Z (axial direction) are by 15 ± 6, 8 ± 8, and 21 ± 2% from the resolution without a pupil filter. The resolution enhancement is even better than the calculation using vector field, which predicts the corresponding enhancement of 11, 8, and 6%. The discussion is made to explain the unexpected results. We also demonstrate the photothermal imaging of thick biological samples (cells from rabbit intestine and kidney) stained with hematoxylin and eosin dye with the inverse-annular filter. Second, a fast, high-sensitivity photothermal microscope is developed by implementing a spatially segmented balanced detection scheme into a laser scanning microscope using a Galvano mirror. We confirm a 4.9 times improvement in signal-to-noise ratio in the spatially segmented balanced detection compared with that of conventional detection. The system demonstrates simultaneous bi-modal photothermal and confocal fluorescence imaging of transgenic mouse brain tissue with a pixel dwell time of 20 µs. The

Probe-Hole Field Emission Microscope System Controlled by Computer

Science.gov (United States)

Gong, Yunming; Zeng, Haishan

1991-09-01

A probe-hole field emission microscope system, controlled by an Apple II computer, has been developed and operated successfully for measuring the work function of a single crystal plane. The work functions on the clean W(100) and W(111) planes are measured to be 4.67 eV and 4.45 eV, respectively.

Impedance measurements on Au microelectrodes using controlled atmosphere high temperature scanning probe microscope

DEFF Research Database (Denmark)

Wu, Yuehua; Hansen, Karin Vels; Jacobsen, Torben

2011-01-01

High temperature impedance measurements on Au microelectrodes deposited on polished yttria stabilized zirconia (YSZ) pellets were demonstrated using a newly designed controlled atmosphere high temperature scanning probe microscope (CAHT-SPM). Probes based on Pt0.8Ir0.2 were fabricated and employed...

Plasma Perturbations in High-Speed Probing of Hall Thruster Discharge Chambers: Quantification and Mitigation

Science.gov (United States)

Jorns, Benjamin A.; Goebel, Dan M.; Hofer, Richard R.

2015-01-01

An experimental investigation is presented to quantify the effect of high-speed probing on the plasma parameters inside the discharge chamber of a 6-kW Hall thruster. Understanding the nature of these perturbations is of significant interest given the importance of accurate plasma measurements for characterizing thruster operation. An array of diagnostics including a high-speed camera and embedded wall probes is employed to examine in real time the changes in electron temperature and plasma potential induced by inserting a high-speed reciprocating Langmuir probe into the discharge chamber. It is found that the perturbations onset when the scanning probe is downstream of the electron temperature peak, and that along channel centerline, the perturbations are best characterized as a downstream shift of plasma parameters by 15-20% the length of the discharge chamber. A parametric study is performed to investigate techniques to mitigate the observed probe perturbations including varying probe speed, probe location, and operating conditions. It is found that the perturbations largely disappear when the thruster is operated at low power and low discharge voltage. The results of this mitigation study are discussed in the context of recommended methods for generating unperturbed measurements of the discharge chamber plasma.

Large Scale Scanning Probe Microscope "Making Shear Force Scanning visible."

NARCIS (Netherlands)

Bosma, E.; Offerhaus, Herman L.; van der Veen, Jan T.; van der Veen, J.T.; Segerink, Franciscus B.; Wessel, I.M.

2010-01-01

We describe a demonstration of a scanning probe microscope with shear-force tuning fork feedback. The tuning fork is several centimeters long, and the rigid fiber is replaced by a toothpick. By scaling this demonstration to visible dimensions the accessibility of shear-force scanning and tuning fork

Theoretical study of the effect of probe shape on adhesion force between probe and substrate in atomic force microscope experiment

OpenAIRE

Yang, Li; Hu, Junhui; Kong, Lingjiang

2017-01-01

The quantitative description of adhesion force dependence on the probe shapes are of importance in many scientific and industrial fields. In order to elucidate how the adhesion force varied with the probe shape in atomic force microscope manipulation experiment, we performed a theoretical study of the influences of the probe shape (the sphere and parabolic probe) on the adhesion force at different humidity. We found that the combined action of the triple point and the Kelvin radius guiding th...

High throughput, parallel scanning probe microscope for nanometrology and nanopatterning applications

NARCIS (Netherlands)

Sadeghian Marnani, H.; Paul, P.C.; Herfst, R.W.; Dekker, A.; Winters, J.; Maturova, K.

2017-01-01

Scanning Probe microscope (SPM) is an important nanoinstrument for several applications such as bioresearch, metrology, inspection and nanopatterning. Single SPM is associated with relatively slow rate of scanning and low throughput measurement, thus not being suitable for scanning large samples

Precision of single-engage micro Hall effect measurements

DEFF Research Database (Denmark)

Henrichsen, Henrik Hartmann; Hansen, Ole; Kjær, Daniel

2014-01-01

Recently a novel microscale Hall effect measurement technique has been developed to extract sheet resistance (RS), Hall sheet carrier density (NHS) and Hall mobility (μH) from collinear micro 4-point probe measurements in the vicinity of an insulating boundary [1]. The technique measures in less...... than a minute directly the local transport properties, which enables in-line production monitoring on scribe line test pads [2]. To increase measurement speed and reliability, a method in which 4-point measurements are performed using two different electrode pitches has been developed [3......]. In this study we calculate the measurement error on RS, NHS and μH resulting from electrode position errors, probe placement, sample size and Hall signal magnitude. We show the relationship between measurement precision and electrode pitch, which is important when down-scaling the micro 4-point probe to fit...

Gwyscan: a library to support non-equidistant scanning probe microscope measurements

International Nuclear Information System (INIS)

Klapetek, Petr; Grolich, Petr; Valtr, Miroslav; Yacoot, Andrew; Nečas, David

2017-01-01

We present a software library and related methodology for enabling easy integration of adaptive step (non-equidistant) scanning techniques into metrological scanning probe microscopes or scanning probe microscopes where individual x , y position data are recorded during measurements. Scanning with adaptive steps can reduce the amount of data collected in SPM measurements thereby leading to faster data acquisition, a smaller amount of data collection required for a specific analytical task and less sensitivity to mechanical and thermal drift. Implementation of adaptive scanning routines into a custom built microscope is not normally an easy task: regular data are much easier to handle for previewing (e.g. levelling) and storage. We present an environment to make implementation of adaptive scanning easier for an instrument developer, specifically taking into account data acquisition approaches that are used in high accuracy microscopes as those developed by National Metrology Institutes. This includes a library with algorithms written in C and LabVIEW for handling data storage, regular mesh preview generation and planning the scan path on basis of different assumptions. A set of modules for Gwyddion open source software for handling these data and for their further analysis is presented. Using this combination of data acquisition and processing tools one can implement adaptive scanning in a relatively easy way into an instrument that was previously measuring on a regular grid. The performance of the presented approach is shown and general non-equidistant data processing steps are discussed. (paper)

Gwyscan: a library to support non-equidistant scanning probe microscope measurements

Science.gov (United States)

Klapetek, Petr; Yacoot, Andrew; Grolich, Petr; Valtr, Miroslav; Nečas, David

2017-03-01

We present a software library and related methodology for enabling easy integration of adaptive step (non-equidistant) scanning techniques into metrological scanning probe microscopes or scanning probe microscopes where individual x, y position data are recorded during measurements. Scanning with adaptive steps can reduce the amount of data collected in SPM measurements thereby leading to faster data acquisition, a smaller amount of data collection required for a specific analytical task and less sensitivity to mechanical and thermal drift. Implementation of adaptive scanning routines into a custom built microscope is not normally an easy task: regular data are much easier to handle for previewing (e.g. levelling) and storage. We present an environment to make implementation of adaptive scanning easier for an instrument developer, specifically taking into account data acquisition approaches that are used in high accuracy microscopes as those developed by National Metrology Institutes. This includes a library with algorithms written in C and LabVIEW for handling data storage, regular mesh preview generation and planning the scan path on basis of different assumptions. A set of modules for Gwyddion open source software for handling these data and for their further analysis is presented. Using this combination of data acquisition and processing tools one can implement adaptive scanning in a relatively easy way into an instrument that was previously measuring on a regular grid. The performance of the presented approach is shown and general non-equidistant data processing steps are discussed.

Evidence of a fractional quantum Hall nematic phase in a microscopic model

Science.gov (United States)

Regnault, N.; Maciejko, J.; Kivelson, S. A.; Sondhi, S. L.

2017-07-01

At small momenta, the Girvin-MacDonald-Platzman (GMP) mode in the fractional quantum Hall (FQH) effect can be identified with gapped nematic fluctuations in the isotropic FQH liquid. This correspondence would be exact as the GMP mode softens upon approach to the putative point of a quantum phase transition to a FQH nematic. Motivated by these considerations as well as by suggestive evidence of an FQH nematic in tilted field experiments, we have sought evidence of such a nematic FQHE in a microscopic model of interacting electrons in the lowest Landau level at filling factor 1/3. Using a family of anisotropic Laughlin states as trial wave functions, we find a continuous quantum phase transition between the isotropic Laughlin liquid and the FQH nematic. Results of numerical exact diagonalization also suggest that rotational symmetry is spontaneously broken, and that the phase diagram of the model contains both a nematic and a stripe phase.

Spin Hall effects

Science.gov (United States)

Sinova, Jairo; Valenzuela, Sergio O.; Wunderlich, J.; Back, C. H.; Jungwirth, T.

2015-10-01

Spin Hall effects are a collection of relativistic spin-orbit coupling phenomena in which electrical currents can generate transverse spin currents and vice versa. Despite being observed only a decade ago, these effects are already ubiquitous within spintronics, as standard spin-current generators and detectors. Here the theoretical and experimental results that have established this subfield of spintronics are reviewed. The focus is on the results that have converged to give us the current understanding of the phenomena, which has evolved from a qualitative to a more quantitative measurement of spin currents and their associated spin accumulation. Within the experimental framework, optical-, transport-, and magnetization-dynamics-based measurements are reviewed and linked to both phenomenological and microscopic theories of the effect. Within the theoretical framework, the basic mechanisms in both the extrinsic and intrinsic regimes are reviewed, which are linked to the mechanisms present in their closely related phenomenon in ferromagnets, the anomalous Hall effect. Also reviewed is the connection to the phenomenological treatment based on spin-diffusion equations applicable to certain regimes, as well as the spin-pumping theory of spin generation used in many measurements of the spin Hall angle. A further connection to the spin-current-generating spin Hall effect to the inverse spin galvanic effect is given, in which an electrical current induces a nonequilibrium spin polarization. This effect often accompanies the spin Hall effect since they share common microscopic origins. Both can exhibit the same symmetries when present in structures comprising ferromagnetic and nonmagnetic layers through their induced current-driven spin torques or induced voltages. Although a short chronological overview of the evolution of the spin Hall effect field and the resolution of some early controversies is given, the main body of this review is structured from a pedagogical

Modeling the hysteresis of a scanning probe microscope

DEFF Research Database (Denmark)

Dirscherl, Kai; Garnæs, Jørgen; Nielsen, L.

2000-01-01

Most scanning probe microscopes use piezoelectric actuators in open loop configurations. Therefore a major problem related to these instruments is the image distortion due to the hysteresis effect of the piezo. In order to eliminate the distortions, cost effective software control based on a model...... for hysteresis can be applied to the scanner. We describe a new rate-independent model for the hysteresis of a piezo scanner. Two reference standards were used to determine the accuracy of the model; a one-dimensional grating with a period of 3.0 mum and a two-dimensional grating with 200 nm pitch...

Study of submelt laser induced junction nonuniformities using Therma-Probe

DEFF Research Database (Denmark)

Rosseel, E.; Bogdanowicz, J; Clarysse, T.

2010-01-01

to standard and micro-four-point probe sheet resistance data, secondary ion mass spectrometry, and Hall measurements obtained during earlier studies. Besides the impact of the nonuniformities on the “conventional” thermal wave signal, they found a strong correlation to the dc reflectance of the probe laser...... both at macroscopic and microscopic levels. In this work, the authors present high resolution Therma-Probe® measurements to assess the junction nonuniformity on 0.5 keV boron junctions and zoom in on the effect of temperature variations and multiple subsequent laser scans. The results are compared...... (lambda = 675 nm). The dc probe reflectance is dominated by free carriers and is highly correlated to the sheet resistance both on blanket wafers and on real device wafers. ©2010 American Vacuum Society...

Micro-four-point probes in a UHV scanning electron microscope for in-situ surface-conductivity measurements

DEFF Research Database (Denmark)

Shiraki, I.; Nagao, T.; Hasegawa, S.

2000-01-01

For in-situ measurements of surface conductivity in ultrahigh vacuum (UHV), we have installed micro-four-point probes (probe spacings down to 4 mum) in a UHV scanning electron microscope (SEM) combined with scanning reflection-high-energy electron diffraction (RHEED). With the aid of piezoactuators...

Measurement of local critical currents in TFA-MOD processed coated conductors by use of scanning Hall-probe microscopy

International Nuclear Information System (INIS)

Shiohara, K.; Higashikawa, K.; Kawaguchi, T.; Inoue, M.; Kiss, T.; Yoshizumi, M.; Izumi, T.

2011-01-01

We have investigated 2-dimensional distribution of critical current density. We have measured TFA-MOD processed YBCO coated conductor. We used scanning Hall-probe microscopy. These provided information is useful for fabrication process of coated conductor. We have carried out 2-dimensional (2D) measurement of local critical current in a Trifluoroacetates-Metal Organic Deposition (TFA-MOD) processed YBCO coated conductor using scanning Hall-probe microscopy. Recently, remarkable R and D accomplishments on the fabrication processes of coated conductors have been conducted extensively and reported. The TFA-MOD process has been expected as an attractive process to produce coated conductors with high performance at a low production cost due to a simple process using non-vacuum equipments. On the other hand, enhancement of critical currents and homogenization of the critical current distribution in the coated conductors are definitely very important for practical applications. According to our measurements, we can detect positions and spatial distribution of defects in the conductor. This kind of information will be very helpful for the improvement of the TFA-MOD process and for the design of the conductor intended for practical electric power device applications.

Atom-probe field-ion-microscope mass spectrometer

International Nuclear Information System (INIS)

Nishikawa, Osamu

1983-01-01

The titled analyzer, called simply atom-probe, has been developed by combining a field ion microscope (FIM) and a mass spectrometer, and is divided into the time-of-flight type, magnetic sector type, and quadrupole type depending on the types of mass spectrometers. In this paper, the author first describes on the principle and construction of a high resolution, time-of-flight atom-probe developed and fabricated in his laboratory. The feature of the atom-probe lies in the analysis of atoms and molecules in hyper-fine structure region one by one utilizing the high resolution of FIM. It also has the advantages of directly determining the composition by a ratio of the numbers of respective ions because of a constant detection sensitivity regardless of mass numbers, of the resolution as high as single atom layer in depth direction, and of detecting the positional relationship among detected ions by the order of detection in a sample. To determine the composition in a hyperfine structure region, the limited small number of atoms and molecules in the region must be identified distinctly one by one. In the analyzed result of Ni-silicide formed by heating Si evaporated on a Ni tip at 1000 K for 5 minutes, each isotope was not only clearly separated, but also their abundance ratio was very close to the natural abundance ratio. The second half of the paper reports on the analysis of TiC promising for a cold cathode material, adsorption of CO and alcohol, and the composition and structure of silicides, as a few application examples. (Wakatsuki, Y.)

All Optical Measurement Proposed for the Photovoltaic Hall Effect

International Nuclear Information System (INIS)

Oka, Takashi; Aoki, Hideo

2011-01-01

We propose an all optical way to measure the recently proposed p hotovoltaic Hall effect , i.e., a Hall effect induced by a circularly polarized light in the absence of static magnetic fields. This is done in a pump-probe experiment with the Faraday rotation angle being the probe. The Floquet extended Kubo formula for photo-induced optical response is formulated and the ac-Hall conductivity is calculated. We also point out the possibility of observing the effect in two layered graphene, three-dimensional graphite, and more generally in multi-band systems such as materials described by the dp-model.

Imaging the Conductance of Integer and Fractional Quantum Hall Edge States

Directory of Open Access Journals (Sweden)

Nikola Pascher

2014-01-01

Full Text Available We measure the conductance of a quantum point contact while the biased tip of a scanning probe microscope induces a depleted region in the electron gas underneath. At a finite magnetic field, we find plateaus in the real-space maps of the conductance as a function of tip position at integer (ν=1, 2, 3, 4, 6, 8 and fractional (ν=1/3, 2/3, 5/3, 4/5 values of transmission. They resemble theoretically predicted compressible and incompressible stripes of quantum Hall edge states. The scanning tip allows us to shift the constriction limiting the conductance in real space over distances of many microns. The resulting stripes of integer and fractional filling factors are rugged on scales of a few hundred nanometers, i.e., on a scale much smaller than the zero-field elastic mean free path of the electrons. Our experiments demonstrate that microscopic inhomogeneities are relevant even in high-quality samples and lead to locally strongly fluctuating widths of incompressible regions even down to their complete suppression for certain tip positions. The macroscopic quantization of the Hall resistance measured experimentally in a nonlocal contact configuration survives in the presence of these inhomogeneities, and the relevant local energy scale for the ν=2 state turns out to be independent of tip position.

Novel optical probe for quantum Hall system

Indian Academy of Sciences (India)

to explore Landau levels of a two-dimensional electron gas (2DEG) in modulation doped ... Keywords. Surface photovoltage spectroscopy; quantum Hall effect; Landau levels; edge states. ... An optical fibre carries light from tunable diode laser.

Self-mixing laser diode included in scanning microwave microscope to the control of probe nanodisplacement

Science.gov (United States)

Usanov, D. A.; Skripal, A. V.; Astakhov, E. I.; Dobdin, S. Y.

2018-04-01

The possibilities of self-mixing interferometry for measuring nanodisplacement of a probe included in a near-field scanning microwave microscope have been considered. The features of the formation of a laser interference signal at current modulation of the wavelength of laser radiation have been investigated. Experimental responses of a semiconductor laser system included in scanning microwave microscope to control nanodisplacement of the probe have been demonstrated.To register the nanodisplacement of the probe, it is proposed to use the method of determining the stationary phase of a laser interference signal by low-frequency spectrum of a semiconductor laser. The change of the amplitudes of the spectral components in the spectrum of the interference signal due to creation of the standing wave in the external resonator of the laser self-mixing system has been shown. The form of the interference signal at current modulation of the radiation wavelength was experimentally obtained when the probe moves with a step of 80 nm. The results of measuring nanodisplacements of an electromagnetic translator STANDA 8MVT40-13 have been demonstrated. Deviation of the nanodisplacement of the proposed method does not exceed 15%.

Nanomanipulation and nanofabrication with multi-probe scanning tunneling microscope: from individual atoms to nanowires.

Science.gov (United States)

Qin, Shengyong; Kim, Tae-Hwan; Wang, Zhouhang; Li, An-Ping

2012-06-01

The wide variety of nanoscale structures and devices demands novel tools for handling, assembly, and fabrication at nanoscopic positioning precision. The manipulation tools should allow for in situ characterization and testing of fundamental building blocks, such as nanotubes and nanowires, as they are built into functional devices. In this paper, a bottom-up technique for nanomanipulation and nanofabrication is reported by using a 4-probe scanning tunneling microscope (STM) combined with a scanning electron microscope (SEM). The applications of this technique are demonstrated in a variety of nanosystems, from manipulating individual atoms to bending, cutting, breaking carbon nanofibers, and constructing nanodevices for electrical characterizations. The combination of the wide field of view of SEM, the atomic position resolution of STM, and the flexibility of multiple scanning probes is expected to be a valuable tool for rapid prototyping in the nanoscience and nanotechnology.

Real-space imaging of fractional quantum Hall liquids

Science.gov (United States)

Hayakawa, Junichiro; Muraki, Koji; Yusa, Go

2013-01-01

Electrons in semiconductors usually behave like a gas--as independent particles. However, when confined to two dimensions under a perpendicular magnetic field at low temperatures, they condense into an incompressible quantum liquid. This phenomenon, known as the fractional quantum Hall (FQH) effect, is a quantum-mechanical manifestation of the macroscopic behaviour of correlated electrons that arises when the Landau-level filling factor is a rational fraction. However, the diverse microscopic interactions responsible for its emergence have been hidden by its universality and macroscopic nature. Here, we report real-space imaging of FQH liquids, achieved with polarization-sensitive scanning optical microscopy using trions (charged excitons) as a local probe for electron spin polarization. When the FQH ground state is spin-polarized, the triplet/singlet intensity map exhibits a spatial pattern that mirrors the intrinsic disorder potential, which is interpreted as a mapping of compressible and incompressible electron liquids. In contrast, when FQH ground states with different spin polarization coexist, domain structures with spontaneous quasi-long-range order emerge, which can be reproduced remarkably well from the disorder patterns using a two-dimensional random-field Ising model. Our results constitute the first reported real-space observation of quantum liquids in a class of broken symmetry state known as the quantum Hall ferromagnet.

Field programmable gate array based reconfigurable scanning probe/optical microscope.

Science.gov (United States)

Nowak, Derek B; Lawrence, A J; Dzegede, Zechariah K; Hiester, Justin C; Kim, Cliff; Sánchez, Erik J

2011-10-01

The increasing popularity of nanometrology and nanospectroscopy has pushed researchers to develop complex new analytical systems. This paper describes the development of a platform on which to build a microscopy tool that will allow for flexibility of customization to suit research needs. The novelty of the described system lies in its versatility of capabilities. So far, one version of this microscope has allowed for successful near-field and far-field fluorescence imaging with single molecule detection sensitivity. This system is easily adapted for reflection, polarization (Kerr magneto-optical (MO)), Raman, super-resolution techniques, and other novel scanning probe imaging and spectroscopic designs. While collecting a variety of forms of optical images, the system can simultaneously monitor topographic information of a sample with an integrated tuning fork based shear force system. The instrument has the ability to image at room temperature and atmospheric pressure or under liquid. The core of the design is a field programmable gate array (FPGA) data acquisition card and a single, low cost computer to control the microscope with analog control circuitry using off-the-shelf available components. A detailed description of electronics, mechanical requirements, and software algorithms as well as examples of some different forms of the microscope developed so far are discussed.

Mode-mismatched confocal thermal-lens microscope with collimated probe beam

Energy Technology Data Exchange (ETDEWEB)

Cabrera, Humberto, E-mail: hcabrera@ictp.it [SPIE-ICTP Anchor Research Laboratory, International Centre for Theoretical Physics (ICTP), Strada Costiera 11, Trieste (Italy); Centro Multidisciplinartio de Ciencias, Instituto Venezolano de Investigaciones Científicas (IVIC), Mérida 5101 (Venezuela, Bolivarian Republic of); Korte, Dorota; Franko, Mladen [Laboratory for Environmental Research, University of Nova Gorica, Vipavska 13, 5000 Nova Gorica (Slovenia)

2015-05-15

We report a thermal lens microscope (TLM) based on an optimized mode-mismatched configuration. It takes advantage of the coaxial counter propagating tightly focused excitation and collimated probe beams, instead of both focused at the sample, as it is in currently known TLM setups. A simple mathematical model that takes into account the main features of the instrument is presented. The confocal detection scheme and the introduction of highly collimated probe beam allow enhancing the versatility, limit of detection (LOD), and sensitivity of the instrument. The theory is experimentally verified measuring ethanol’s absorption coefficient at 532.8 nm. Additionally, the presented technique is applied for detection of ultra-trace amounts of Cr(III) in liquid solution. The achieved LOD is 1.3 ppb, which represents 20-fold enhancement compared to transmission mode spectrometric techniques and a 7.5-fold improvement compared to previously reported methods for Cr(III) based on thermal lens effect.

Accurate micro Hall effect measurements on scribe line pads

DEFF Research Database (Denmark)

Østerberg, Frederik Westergaard; Petersen, Dirch Hjorth; Wang, Fei

2009-01-01

Hall mobility and sheet carrier density are important parameters to monitor in advanced semiconductor production. If micro Hall effect measurements are done on small pads in scribe lines, these parameters may be measured without using valuable test wafers. We report how Hall mobility can...... be extracted from micro four-point measurements performed on a rectangular pad. The dimension of the investigated pad is 400 × 430 ¿m2, and the probe pitches range from 20 ¿m to 50 ¿m. The Monte Carlo method is used to find the optimal way to perform the Hall measurement and extract Hall mobility most...

Non-destructive evaluation of austenite stainless steels using a scanning Hall-sensor microscope

International Nuclear Information System (INIS)

Oota, Akio

2004-01-01

Spontaneous magnetic field on the surface of austenite stainless steel SUS304 was measured under a static condition by using a scanning Hall-sensor microscope, which had magnetic sensitive area of 50μm x 50μm. The precursor of fatigue fracture was tentatively detected from the change of magnetic image observed by the microscope. Specimens used in this experiment were prepared by following procedures: Rolled SUS304 was cut into a piece of 110 mm length x 40 mm width by electric discharge processing, and then notches were carved at both centers of the length of the piece. A test of tensile strength of the piece was run at room temperature, and the change of spontaneous magnetization image was studied before and after the tensile strength test. After the test, spontaneous magnetic field was observed around the notches although it was not detected before the test. Many slip lines were found around the location where the spontaneous magnetic field was observed, and a significant increase of hardness was examined by Vickers hardness. These facts indicated that the spontaneous magnetic field observed after the test would be caused from stress-induced martensitic transformation in austenite stainless steel. The stress distribution after applying tensile stress was simulated and the result was compared with the distribution of the spontaneous magnetic field. After the comparison between the stress and the spontaneous magnetic field distribution, it was concluded that the distribution of spontaneous magnetic field resembled that of principal shear stress rather than of principal stress. Therefore, the principal shear stress would be suggested to be a driving force for the stress-induced martensitic transformation. (Y. Kazumata)

Probing bulk physics in the 5/2 fractional quantum Hall effect using the Corbino geometry

Science.gov (United States)

Schmidt, Benjamin; Bennaceur, Keyan; Bilodeau, Simon; Gaucher, Samuel; Lilly, Michael; Reno, John; Pfeiffer, Loren; West, Ken; Reulet, Bertrand; Gervais, Guillaume

We present two- and four-point Corbino geometry transport measurements in the second Landau level in GaAs/AlGaAs heterostructures. By avoiding edge transport, we are able to directly probe the physics of the bulk quasiparticles in fractional quantum Hall (FQH) states including 5/2. Our highest-quality sample shows stripe and bubble phases in high Landau levels, and most importantly well-resolved FQH minima in the second Landau level. We report Arrhenius-type fits to the activated conductance, and find that σ0 agrees well with theory and existing Hall geometry data in the first Landau level, but not in the second Landau level. We will discuss the advantages the Corbino geometry could bring to various experiments designed to detect the non-Abelian entropy at 5/2, and our progress towards realizing those schemes. The results of these experiments could complement interferometry and other edge-based measurements by providing direct evidence for non-Abelian behaviour of the bulk quasiparticles. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL8500.

Inverse spin Hall effect by spin injection

Science.gov (United States)

Liu, S. Y.; Horing, Norman J. M.; Lei, X. L.

2007-09-01

Motivated by a recent experiment [S. O. Valenzuela and M. Tinkham, Nature (London) 442, 176 (2006)], the authors present a quantitative microscopic theory to investigate the inverse spin-Hall effect with spin injection into aluminum considering both intrinsic and extrinsic spin-orbit couplings using the orthogonalized-plane-wave method. Their theoretical results are in good agreement with the experimental data. It is also clear that the magnitude of the anomalous Hall resistivity is mainly due to contributions from extrinsic skew scattering.

Metrological large range scanning probe microscope

International Nuclear Information System (INIS)

Dai Gaoliang; Pohlenz, Frank; Danzebrink, Hans-Ulrich; Xu Min; Hasche, Klaus; Wilkening, Guenter

2004-01-01

We describe a metrological large range scanning probe microscope (LR-SPM) with an Abbe error free design and direct interferometric position measurement capability, aimed at versatile traceable topographic measurements that require nanometer accuracy. A dual-stage positioning system was designed to achieve both a large measurement range and a high measurement speed. This dual-stage system consists of a commercially available stage, referred to as nanomeasuring machine (NMM), with a motion range of 25 mmx25 mmx5 mm along x, y, and z axes, and a compact z-axis piezoelectric positioning stage (compact z stage) with an extension range of 2 μm. The metrological LR-SPM described here senses the surface using a stationary fixed scanning force microscope (SFM) head working in contact mode. During operation, lateral scanning of the sample is performed solely by the NMM. Whereas the z motion, controlled by the SFM signal, is carried out by a combination of the NMM and the compact z stage. In this case the compact z stage, with its high mechanical resonance frequency (greater than 20 kHz), is responsible for the rapid motion while the NMM simultaneously makes slower movements over a larger motion range. To reduce the Abbe offset to a minimum the SFM tip is located at the intersection of three interferometer measurement beams orientated in x, y, and z directions. To improve real time performance two high-end digital signal processing (DSP) systems are used for NMM positioning and SFM servocontrol. Comprehensive DSP firmware and Windows XP-based software are implemented, providing a flexible and user-friendly interface. The instrument is able to perform large area imaging or profile scanning directly without stitching small scanned images. Several measurements on different samples such as flatness standards, nanostep height standards, roughness standards as well as sharp nanoedge samples and 1D gratings demonstrate the outstanding metrological capabilities of the instrument

Anode Fall Formation in a Hall Thruster

International Nuclear Information System (INIS)

Dorf, Leonid A.; Raitses, Yevgeny F.; Smirnov, Artem N.; Fisch, Nathaniel J.

2004-01-01

As was reported in our previous work, accurate, nondisturbing near-anode measurements of the plasma density, electron temperature, and plasma potential performed with biased and emissive probes allowed the first experimental identification of both electron-repelling (negative anode fall) and electron-attracting (positive anode fall) anode sheaths in Hall thrusters. An interesting new phenomenon revealed by the probe measurements is that the anode fall changes from positive to negative upon removal of the dielectric coating, which appears on the anode surface during the course of Hall thruster operation. As reported in the present work, energy dispersion spectroscopy analysis of the chemical composition of the anode dielectric coating indicates that the coating layer consists essentially of an oxide of the anode material (stainless steel). However, it is still unclear how oxygen gets into the thruster channel. Most importantly, possible mechanisms of anode fall formation in a Hall thruster with a clean and a coated anodes are analyzed in this work; practical implication of understanding the general structure of the electron-attracting anode sheath in the case of a coated anode is also discussed

Full-field parallel interferometry coherence probe microscope for high-speed optical metrology.

Science.gov (United States)

Safrani, A; Abdulhalim, I

2015-06-01

Parallel detection of several achromatic phase-shifted images is used to obtain a high-speed, high-resolution, full-field, optical coherence probe tomography system based on polarization interferometry. The high enface imaging speed, short coherence gate, and high lateral resolution provided by the system are exploited to determine microbump height uniformity in an integrated semiconductor chip at 50 frames per second. The technique is demonstrated using the Linnik microscope, although it can be implemented on any polarization-based interference microscopy system.

A near-field scanning microwave microscope based on a superconducting resonator for low power measurements.

Science.gov (United States)

de Graaf, S E; Danilov, A V; Adamyan, A; Kubatkin, S E

2013-02-01

We report on the design and performance of a cryogenic (300 mK) near-field scanning microwave microscope. It uses a microwave resonator as the near-field sensor, operating at a frequency of 6 GHz and microwave probing amplitudes down to 100 μV, approaching low enough photon population (N ∼ 1000) of the resonator such that coherent quantum manipulation becomes feasible. The resonator is made out of a miniaturized distributed fractal superconducting circuit that is integrated with the probing tip, micromachined to be compact enough such that it can be mounted directly on a quartz tuning-fork, and used for parallel operation as an atomic force microscope (AFM). The resonator is magnetically coupled to a transmission line for readout, and to achieve enhanced sensitivity we employ a Pound-Drever-Hall measurement scheme to lock to the resonance frequency. We achieve a well localized near-field around the tip such that the microwave resolution is comparable to the AFM resolution, and a capacitive sensitivity down to 6.4 × 10(-20) F/Hz, limited by mechanical noise. We believe that the results presented here are a significant step towards probing quantum systems at the nanoscale using near-field scanning microwave microscopy.

Micro-four-point Probe Hall effect Measurement method

DEFF Research Database (Denmark)

Petersen, Dirch Hjorth; Hansen, Ole; Lin, Rong

2008-01-01

barriers and with a magnetic field applied normal to the plane of the sheet. Based on this potential, analytical expressions for the measured four-point resistance in presence of a magnetic field are derived for several simple sample geometries. We show how the sheet resistance and Hall effect...

Quantum Hall Valley Nematics: From Field Theories to Microscopic Models

Science.gov (United States)

Parameswaran, Siddharth

The interplay between quantum Hall ordering and spontaneously broken ``internal'' symmetries in two-dimensional electron systems with spin or pseudospin degrees of freedom gives rise to a variety of interesting phenomena, including novel phases, phase transitions, and topological excitations. I will discuss a theory of broken-symmetry quantum Hall states, applicable to a class of multivalley systems, where the symmetry at issue is a point-group element that combines a spatial rotation with a permutation of valley indices. I will explore its ramifications for the phase diagram of a variety of experimental systems, such as AlAs and Si quantum wells and the surface states of bismuth. I will also discuss unconventional transport phenomena in these phases in the presence of quenched randomness, and the possible mechanisms of selection between degenerate broken-symmetry phases in clean systems. I acknowledge support from NSF DMR-1455366.

Microminiature Hall probes based on n-InSb(Sn)/i-GaAs heterostructure for pulsed magnetic field applications up to 52 T

Energy Technology Data Exchange (ETDEWEB)

Mironov, O.A.; Myronov, M.; Durov, S.; Drachenko, O.; Leotin, J

2004-04-30

Microminiature Hall probes with sensitive area down to 33x115 {mu}m and based on n-InSb/i-GaAs optimized Sn-doped MBE-grown heterostructures are reported. The 'metallurgical' thicknesses of the n-InSb epilayers lie in the range d{sup m}=1.1-10.5 {mu}m giving room-temperature mobilities of (9-15)x10{sup 3} cm{sup 2}/Vs with carrier densities of (0.96-2.56)x10{sup 18} cm{sup -3}. Characterization of the devices was performed by magnetotransport measurements in quasi-static and pulsed magnetic fields. In the temperature range 1.1-300 K and in magnetic fields up to 12 T (static) and up to 52 T (pulsed, {tau}=120 mS), transport measurements yield remarkable linearity of the Hall voltage up to 52 T and sensitivity, as well as demonstrating the high-temperature stability of the Hall voltage, the offset voltage and the device resistivity. No significant effect of the high current up to 150 mA on either the sensitivity or the resistivity is observed.

W∞ gauge theory and the quantum Hall effect

International Nuclear Information System (INIS)

Shizuya, K.

1994-05-01

It is shown that a planar system of Hall electrons coupled to an applied electromagnetic field is written in the form of a W ∞ gauge theory. The associated W ∞ gauge field is expressed nonlinearly in terms of an infinite set of multipoles of the electromagnetic field. The W ∞ transformations generate mixing among the Landau levels. They provide a systematic way to classify the electromagnetic characteristics of the Hall system according to the resolution of external probes. In particular, an exact long-wavelength connection is derived between the carrier density and the Hall conductance in the presence of electron-electron interactions. Our approach is complementary to an earlier one and reveals a dual role the W ∞ gauge symmetry plays in the Hall dynamics. (author)

Design of a scanning probe microscope with advanced sample treatment capabilities: An atomic force microscope combined with a miniaturized inductively coupled plasma source

International Nuclear Information System (INIS)

Hund, Markus; Herold, Hans

2007-01-01

We describe the design and performance of an atomic force microscope (AFM) combined with a miniaturized inductively coupled plasma source working at a radio frequency of 27.12 MHz. State-of-the-art scanning probe microscopes (SPMs) have limited in situ sample treatment capabilities. Aggressive treatments such as plasma etching or harsh treatments such as etching in aggressive liquids typically require the removal of the sample from the microscope. Consequently, time consuming procedures are required if the same sample spot has to be imaged after successive processing steps. We have developed a first prototype of a SPM which features a quasi in situ sample treatment using a modified commercial atomic force microscope. A sample holder is positioned in a special reactor chamber; the AFM tip can be retracted by several millimeters so that the chamber can be closed for a treatment procedure. Most importantly, after the treatment, the tip is moved back to the sample with a lateral drift per process step in the 20 nm regime. The performance of the prototype is characterized by consecutive plasma etching of a nanostructured polymer film

Precise Orientation of a Single C60 Molecule on the Tip of a Scanning Probe Microscope

Science.gov (United States)

Chiutu, C.; Sweetman, A. M.; Lakin, A. J.; Stannard, A.; Jarvis, S.; Kantorovich, L.; Dunn, J. L.; Moriarty, P.

2012-06-01

We show that the precise orientation of a C60 molecule which terminates the tip of a scanning probe microscope can be determined with atomic precision from submolecular contrast images of the fullerene cage. A comparison of experimental scanning tunneling microscopy data with images simulated using computationally inexpensive Hückel theory provides a robust method of identifying molecular rotation and tilt at the end of the probe microscope tip. Noncontact atomic force microscopy resolves the atoms of the C60 cage closest to the surface for a range of molecular orientations at tip-sample separations where the molecule-substrate interaction potential is weakly attractive. Measurements of the C60C60 pair potential acquired using a fullerene-terminated tip are in excellent agreement with theoretical predictions based on a pairwise summation of the van der Waals interactions between C atoms in each cage, i.e., the Girifalco potential [L. Girifalco, J. Phys. Chem. 95, 5370 (1991)JPCHAX0022-365410.1021/j100167a002].

Mapping degenerate vortex states in a kagome lattice of elongated antidots via scanning Hall probe microscopy

Science.gov (United States)

Xue, C.; Ge, J.-Y.; He, A.; Zharinov, V. S.; Moshchalkov, V. V.; Zhou, Y. H.; Silhanek, A. V.; Van de Vondel, J.

2017-07-01

We investigate the degeneracy of the superconducting vortex matter ground state by directly visualizing the vortex configurations in a kagome lattice of elongated antidots via scanning Hall probe microscopy. The observed vortex patterns, at specific applied magnetic fields, are in good agreement with the configurations obtained using time-dependent Ginzburg-Landau simulations. Both results indicate that the long-range interaction in this nanostructured superconductor is unable to lift the degeneracy between different vortex states and the pattern formation is mainly ruled by the nearest-neighbor interaction. This simplification makes it possible to identify a set of simple rules characterizing the vortex configurations. We demonstrate that these rules can explain both the observed vortex distributions and the magnetic-field-dependent degree of degeneracy.

Plan for SQUID microscope at ASRC: Vision, purposes and the present status

International Nuclear Information System (INIS)

Kadowaki, K.; Kakeya, I.; Suzuki, J.; Hata, Y.; Hojyo, K

2001-01-01

A new research plan to develop SQUID microscope and apply it to advanced science and technology research was started in the year of 2000 at the Advanced Science Research Center (ASRC) of JAERI (Japan Atomic Energy Research Institute). This plan was made to develop 'research of ultrafine magnetic structures with magnetic microscope' and is scheduled to continue five years. Principle of SQUID magnetic microscope is to observe changes of magnetic field in microscopic space using SQUID element as the magnetic probe. At present this type of instrument is fabricated by Seiko Instruments Inc. in Japan and is commercially available. Therefore, this plan is being promoted in collaboration with Seiko Instruments Inc. One of the main issues of the present plan is to raise the spatial resolution to the extremity. As of magnetic microscopes, 'magnetic force microscope' and 'scanning Hall probe microscope' also exist. They have different characteristics of their own. The present plan needs challenging technical developments in various fields. Supposed the spatial resolution be made very high, for example, by making very fine SQUID loop with ultrafine processing, critical technologies like sensitivity, electronics, quantum size effect and so on are to be solved at the same time. Characteristics of the existing instrument are being examined from various aspects. At present, the following three issues are taken up and being studied. (1) High resolution and related technical developments. (2) High sensitivity. (3) High performance of cooling system. Among them, the high resolution is the most serious problem. Completely new design of the SQUID system may be needed. By using the existing instrument, magnetic fluxes trapped on YBCO films are observed and the image quality is being examined. Some of the issues which are considered to be taken up now are listed as follows. (1) Magnetic domain structures on thin film magnetic materials. (2) Observation of structures of Josephson magnetic

Spin Hall Effect in Doped Semiconductor Structures

Science.gov (United States)

Tse, Wang-Kong; Das Sarma, Sankar

2006-03-01

We present a microscopic theory of the extrinsic spin Hall effect based on the diagrammatic perturbation theory. Side-jump (SJ) and skew-scattering (SS) contributions are explicitly taken into account to calculate the spin Hall conductivity, and we show their effects scale as σxy^SJ/σxy^SS ˜(/τ)/ɛF, where τ being the transport relaxation time. Motivated by recent experimental work we apply our theory to n-doped and p-doped 3D and 2D GaAs structures, obtaining analytical formulas for the SJ and SS contributions. Moreover, the ratio of the spin Hall conductivity to longitudinal conductivity is found as σs/σc˜10-3-10-4, in reasonable agreement with the recent experimental results of Kato et al. [Science 306, 1910 (2004)] in n-doped 3D GaAs system.

Probing the local microwave properties of superconducting thin films by a scanning microwave near-field microscope

CERN Document Server

Wu, L Y; Wang, K L; Jiang, T; Kang, L; Yang, S Z; Wu, P H

2002-01-01

In this paper, we present our approach to probe the local microwave properties of superconducting thin films by using the microwave near-field scanning technique. We have employed a coaxial cavity together with a niobium tip as the probe and established a scanning sample stage cooled by liquid nitrogen to study thin film devices at low temperature in our scanning microwave near-field microscope. Nondestructive images have been obtained on the inhomogeneity of the YBaCuO superconducting thin films at microwave frequency. We believe that these results would be helpful in evaluating the microwave performance of the devices.

Plasmon Geometric Phase and Plasmon Hall Shift

Science.gov (United States)

Shi, Li-kun; Song, Justin C. W.

2018-04-01

The collective plasmonic modes of a metal comprise a simple pattern of oscillating charge density that yields enhanced light-matter interaction. Here we unveil that beneath this familiar facade plasmons possess a hidden internal structure that fundamentally alters its dynamics. In particular, we find that metals with nonzero Hall conductivity host plasmons with an intricate current density configuration that sharply departs from that of ordinary zero Hall conductivity metals. This nontrivial internal structure dramatically enriches the dynamics of plasmon propagation, enabling plasmon wave packets to acquire geometric phases as they scatter. At boundaries, these phases accumulate allowing plasmon waves that reflect off to experience a nonreciprocal parallel shift. This plasmon Hall shift, tunable by Hall conductivity as well as plasmon wavelength, displaces the incident and reflected plasmon trajectories and can be readily probed by near-field photonics techniques. Anomalous plasmon geometric phases dramatically enrich the nanophotonics toolbox, and yield radical new means for directing plasmonic beams.

Geometrical modelling of scanning probe microscopes and characterization of errors

International Nuclear Information System (INIS)

Marinello, F; Savio, E; Bariani, P; Carmignato, S

2009-01-01

Scanning probe microscopes (SPMs) allow quantitative evaluation of surface topography with ultra-high resolution, as a result of accurate actuation combined with the sharpness of tips. SPMs measure sequentially, by scanning surfaces in a raster fashion: topography maps commonly consist of data sets ideally reported in an orthonormal rectilinear Cartesian coordinate system. However, due to scanning errors and measurement distortions, the measurement process is far from the ideal Cartesian condition. The paper addresses geometrical modelling of the scanning system dynamics, presenting a mathematical model which describes the surface metric x-, y- and z- coordinates as a function of the measured x'-, y'- and z'-coordinates respectively. The complete mathematical model provides a relevant contribution to characterization and calibration, and ultimately to traceability, of SPMs, when applied for quantitative characterization

Drift-insensitive distributed calibration of probe microscope scanner in nanometer range: Virtual mode

Science.gov (United States)

Lapshin, Rostislav V.

2016-08-01

A method of distributed calibration of a probe microscope scanner is suggested. The main idea consists in a search for a net of local calibration coefficients (LCCs) in the process of automatic measurement of a standard surface, whereby each point of the movement space of the scanner can be characterized by a unique set of scale factors. Feature-oriented scanning (FOS) methodology is used as a basis for implementation of the distributed calibration permitting to exclude in situ the negative influence of thermal drift, creep and hysteresis on the obtained results. Possessing the calibration database enables correcting in one procedure all the spatial systematic distortions caused by nonlinearity, nonorthogonality and spurious crosstalk couplings of the microscope scanner piezomanipulators. To provide high precision of spatial measurements in nanometer range, the calibration is carried out using natural standards - constants of crystal lattice. One of the useful modes of the developed calibration method is a virtual mode. In the virtual mode, instead of measurement of a real surface of the standard, the calibration program makes a surface image ;measurement; of the standard, which was obtained earlier using conventional raster scanning. The application of the virtual mode permits simulation of the calibration process and detail analysis of raster distortions occurring in both conventional and counter surface scanning. Moreover, the mode allows to estimate the thermal drift and the creep velocities acting while surface scanning. Virtual calibration makes possible automatic characterization of a surface by the method of scanning probe microscopy (SPM).

Photon scanning tunneling microscope in combination with a force microscope

NARCIS (Netherlands)

Moers, M.H.P.; Moers, M.H.P.; Tack, R.G.; van Hulst, N.F.; Bölger, B.; Bölger, B.

1994-01-01

The simultaneous operation of a photon scanning tunneling microscope with an atomic force microscope is presented. The use of standard atomic force silicon nitride cantilevers as near-field optical probes offers the possibility to combine the two methods. Vertical forces and torsion are detected

A PC Based Level Indicating Controller Using a Hall Probe Sensor

Directory of Open Access Journals (Sweden)

S. C. Bera

2007-10-01

Full Text Available A PC-based measurement and control of liquid level is a very important part of the modern instrumentation system of a process plant in any process industry. In this measurement and control system, the liquid level is measured by using a suitable level transducer. Among the different types of level transducers for measurement and control of liquid level in storage tank the cheapest one is perhaps the float type sensor and the movement of the float with level is generally converted into the movement of a pointer or that of a flapper or that of a potentiometer. In all of these system float is connected with the output device through a mechanical linkage and thus the measurement is subjected to errors due to wear and tear, friction etc. at the mechanical linkage. Here a non-contact float & magnet type level transducer using hall probe has been described in the present paper. A control system has been designed by using thyristor driven pump as the final control element, the speed of which is controlled by the computer through an opto-isolator unit. Experiments have been performed to find the operational characteristics of the transducer and the control loop. The experimental reports are presented in the paper. A very good performance characteristic has been observed.

Versatile variable temperature and magnetic field scanning probe microscope for advanced material research

Science.gov (United States)

Jung, Jin-Oh; Choi, Seokhwan; Lee, Yeonghoon; Kim, Jinwoo; Son, Donghyeon; Lee, Jhinhwan

2017-10-01

We have built a variable temperature scanning probe microscope (SPM) that covers 4.6 K-180 K and up to 7 T whose SPM head fits in a 52 mm bore magnet. It features a temperature-controlled sample stage thermally well isolated from the SPM body in good thermal contact with the liquid helium bath. It has a 7-sample-holder storage carousel at liquid helium temperature for systematic studies using multiple samples and field emission targets intended for spin-polarized spectroscopic-imaging scanning tunneling microscopy (STM) study on samples with various compositions and doping conditions. The system is equipped with a UHV sample preparation chamber and mounted on a two-stage vibration isolation system made of a heavy concrete block and a granite table on pneumatic vibration isolators. A quartz resonator (qPlus)-based non-contact atomic force microscope (AFM) sensor is used for simultaneous STM/AFM operation for research on samples with highly insulating properties such as strongly underdoped cuprates and strongly correlated electron systems.

Novel Hall sensors developed for magnetic field imaging systems

International Nuclear Information System (INIS)

Cambel, Vladimir; Karapetrov, Goran; Novosad, Valentyn; Bartolome, Elena; Gregusova, Dagmar; Fedor, Jan; Kudela, Robert; Soltys, Jan

2007-01-01

We report here on the fabrication and application of novel planar Hall sensors based on shallow InGaP/AlGaAs/GaAs heterostructure with a two-dimensional electron gas (2DEG) as an active layer. The sensors are developed for two kinds of experiments. In the first one, magnetic samples are placed directly on the Hall sensor. Room temperature experiments of permalloy objects evaporated onto the sensor are presented. In the second experiment, the sensor scans close over a multigranular superconducting sample prepared on a YBCO thin film. Large-area and high-resolution scanning experiments were performed at 4.2 K with the Hall probe scanning system in a liquid helium flow cryostat

Measurement of in-plane magnetic relaxation in RE-123 coated conductors by use of scanning Hall probe microscopy

International Nuclear Information System (INIS)

Shiohara, K.; Higashikawa, K.; Inoue, M.; Kiss, T.; Iijima, Y.; Saitoh, T.; Yoshizumi, M.; Izumi, T.

2013-01-01

Highlights: ► We have investigated electric field criterion of in-plane critical current density. ► We could measure magnetic relaxation in a remanent state. ► The SHPM results show good agreement with the measurements by the 4-probe method. -- Abstract: We have investigated electric field criterion of in-plane critical current density in a coated conductor characterized by scanning Hall-probe microscopy (SHPM). From remanent field distribution and its relaxation measurements, we could obtain critical current distribution and induced electric field simultaneously by considering the Biot-Savart law and the Faraday’s law, respectively. These results lead us to evaluate a distribution of local critical current density and the corresponding criterion of electric field. As a result, it was found that the electric field criterion for the SHPM analysis was several orders lower than that used in the conventional 4-probe resistive method. However, the data point obtained by the SHPM shows good agreement with E–J curve analytically extended from the measurements by the 4-probe method. This means that we could characterize in-plane distribution of critical current density in a coated conductor at an electric field criterion quantitatively by this method in a nondestructive manner. These findings will be very important information since the uniformity of local critical current density in a coated conductor at extremely low electric fields is a key issue (1) especially for DC applications, (2) for quality control of coated conductors, and (3) for the standardization of the characterization of critical current among different methods

Exploring 4D quantum Hall physics with a 2D topological charge pump.

Science.gov (United States)

Lohse, Michael; Schweizer, Christian; Price, Hannah M; Zilberberg, Oded; Bloch, Immanuel

2018-01-03

The discovery of topological states of matter has greatly improved our understanding of phase transitions in physical systems. Instead of being described by local order parameters, topological phases are described by global topological invariants and are therefore robust against perturbations. A prominent example is the two-dimensional (2D) integer quantum Hall effect: it is characterized by the first Chern number, which manifests in the quantized Hall response that is induced by an external electric field. Generalizing the quantum Hall effect to four-dimensional (4D) systems leads to the appearance of an additional quantized Hall response, but one that is nonlinear and described by a 4D topological invariant-the second Chern number. Here we report the observation of a bulk response with intrinsic 4D topology and demonstrate its quantization by measuring the associated second Chern number. By implementing a 2D topological charge pump using ultracold bosonic atoms in an angled optical superlattice, we realize a dynamical version of the 4D integer quantum Hall effect. Using a small cloud of atoms as a local probe, we fully characterize the nonlinear response of the system via in situ imaging and site-resolved band mapping. Our findings pave the way to experimentally probing higher-dimensional quantum Hall systems, in which additional strongly correlated topological phases, exotic collective excitations and boundary phenomena such as isolated Weyl fermions are predicted.

Exploring 4D quantum Hall physics with a 2D topological charge pump

Science.gov (United States)

Lohse, Michael; Schweizer, Christian; Price, Hannah M.; Zilberberg, Oded; Bloch, Immanuel

2018-01-01

The discovery of topological states of matter has greatly improved our understanding of phase transitions in physical systems. Instead of being described by local order parameters, topological phases are described by global topological invariants and are therefore robust against perturbations. A prominent example is the two-dimensional (2D) integer quantum Hall effect: it is characterized by the first Chern number, which manifests in the quantized Hall response that is induced by an external electric field. Generalizing the quantum Hall effect to four-dimensional (4D) systems leads to the appearance of an additional quantized Hall response, but one that is nonlinear and described by a 4D topological invariant—the second Chern number. Here we report the observation of a bulk response with intrinsic 4D topology and demonstrate its quantization by measuring the associated second Chern number. By implementing a 2D topological charge pump using ultracold bosonic atoms in an angled optical superlattice, we realize a dynamical version of the 4D integer quantum Hall effect. Using a small cloud of atoms as a local probe, we fully characterize the nonlinear response of the system via in situ imaging and site-resolved band mapping. Our findings pave the way to experimentally probing higher-dimensional quantum Hall systems, in which additional strongly correlated topological phases, exotic collective excitations and boundary phenomena such as isolated Weyl fermions are predicted.

Measuring minority-carrier diffusion length using a Kelvin probe force microscope

International Nuclear Information System (INIS)

Shikler, R.; Fried, N.; Meoded, T.; Rosenwaks, Y.

2000-01-01

A method based on Kelvin probe force microscopy for measuring minority-carrier diffusion length in semiconductors is described. The method is based on measuring the surface photovoltage between the tip of an atomic force microscope and the surface of an illuminated semiconductor junction. The photogenerated carriers diffuse to the junction and change the contact potential difference between the tip and the sample, as a function of the distance from the junction. The diffusion length L is then obtained by fitting the measured contact potential difference using the minority-carrier continuity equation. The method was applied to measurements of electron diffusion length in GaP pn and Schottky junctions. The measured diffusion length was found to be ∼2 μm, in good agreement with electron beam induced current measurements

Parity effect of bipolar quantum Hall edge transport around graphene antidots.

Science.gov (United States)

Matsuo, Sadashige; Nakaharai, Shu; Komatsu, Katsuyoshi; Tsukagoshi, Kazuhito; Moriyama, Takahiro; Ono, Teruo; Kobayashi, Kensuke

2015-06-30

Parity effect, which means that even-odd property of an integer physical parameter results in an essential difference, ubiquitously appears and enables us to grasp its physical essence as the microscopic mechanism is less significant in coarse graining. Here we report a new parity effect of quantum Hall edge transport in graphene antidot devices with pn junctions (PNJs). We found and experimentally verified that the bipolar quantum Hall edge transport is drastically affected by the parity of the number of PNJs. This parity effect is universal in bipolar quantum Hall edge transport of not only graphene but also massless Dirac electron systems. These results offer a promising way to design electron interferometers in graphene.

Nondestructive hall coefficient measurements using ACPD techniques

Science.gov (United States)

Velicheti, Dheeraj; Nagy, Peter B.; Hassan, Waled

2018-04-01

Hall coefficient measurements offer great opportunities as well as major challenges for nondestructive materials characterization. The Hall effect is produced by the magnetic Lorentz force acting on moving charge carriers in the presence of an applied magnetic field. The magnetic perturbation gives rise to a Hall current that is normal to the conduction current but does not directly perturb the electric potential distribution. Therefore, Hall coefficient measurements usually exploit the so-called transverse galvanomagnetic potential drop effect that arises when the Hall current is intercepted by the boundaries of the specimen and thereby produce a measurable potential drop. In contrast, no Hall potential is produced in a large plate in the presence of a uniform normal field at quasi-static low frequencies. In other words, conventional Hall coefficient measurements are inherently destructive since they require cutting the material under tests. This study investigated the feasibility of using alternating current potential drop (ACPD) techniques for nondestructive Hall coefficient measurements in plates. Specifically, the directional four-point square-electrode configuration is investigated with superimposed external magnetic field. Two methods are suggested to make Hall coefficient measurements in large plates without destructive machining. At low frequencies, constraining the bias magnetic field can replace constraining the dimensions of the specimen, which is inherently destructive. For example, when a cylindrical permanent magnet is used to provide the bias magnetic field, the peak Hall voltage is produced when the diameter of the magnet is equal to the diagonal of the square ACPD probe. Although this method is less effective than cutting the specimen to a finite size, the loss of sensitivity is less than one order of magnitude even at very low frequencies. In contrast, at sufficiently high inspection frequencies the magnetic field of the Hall current induces a

Specimen preparation of irradiated materials for examination in the atom probe field ion microscope

International Nuclear Information System (INIS)

Russell, K.F.; Miller, M.K.

1994-01-01

The atom probe field ion microscope (APFIM) requires specimens in the form of ultrasharp needles. Basic protective measures used to reduce exposure druing specimen preparation are discussed. The low-level radioactive specimen blanks may be made using a two-stage electropolishing process using a thin layer of electrolyte floating on a denser inert liquid; this produces a necked region and eventually two specimens from each single blank. The amount of material handled may also be reduced using a micropolishing technique to repolish blunt or fractured specimens. Control of contamination and possible spills is discussed

Diagnostic Setup for Characterization of Near-Anode Processes in Hall Thrusters

International Nuclear Information System (INIS)

Dorf, L.; Raitses, Y.; Fisch, N.J.

2003-01-01

A diagnostic setup for characterization of near-anode processes in Hall-current plasma thrusters consisting of biased and emissive electrostatic probes, high-precision positioning system and low-noise electronic circuitry was developed and tested. Experimental results show that radial probe insertion does not cause perturbations to the discharge and therefore can be used for accurate near-anode measurements

Observing Fluorescent Probes in Living Cells using a Low-Cost LED Flashlight Retrofitted to a Common Vintage Light Microscope

Directory of Open Access Journals (Sweden)

G. A. Babbitt

2013-03-01

Full Text Available While the application of molecular biological techniques based upon fluorescent probes has rapidly expanded over recent decades, the equipment cost of fluorescent microscopy has largely prevented its adoption in the college and high school classroom. We offer a simple solution to this problem by describing in detail how to build with simple tools, a fluorescent microscope using a common brand of colored LED flashlights and second-hand components of vintage Nikon microscopes. This extremely low cost solution is qualitatively compared to an expensive modern Zeiss system.

Photonic topological boundary pumping as a probe of 4D quantum Hall physics.

Science.gov (United States)

Zilberberg, Oded; Huang, Sheng; Guglielmon, Jonathan; Wang, Mohan; Chen, Kevin P; Kraus, Yaacov E; Rechtsman, Mikael C

2018-01-03

When a two-dimensional (2D) electron gas is placed in a perpendicular magnetic field, its in-plane transverse conductance becomes quantized; this is known as the quantum Hall effect. It arises from the non-trivial topology of the electronic band structure of the system, where an integer topological invariant (the first Chern number) leads to quantized Hall conductance. It has been shown theoretically that the quantum Hall effect can be generalized to four spatial dimensions, but so far this has not been realized experimentally because experimental systems are limited to three spatial dimensions. Here we use tunable 2D arrays of photonic waveguides to realize a dynamically generated four-dimensional (4D) quantum Hall system experimentally. The inter-waveguide separation in the array is constructed in such a way that the propagation of light through the device samples over momenta in two additional synthetic dimensions, thus realizing a 2D topological pump. As a result, the band structure has 4D topological invariants (known as second Chern numbers) that support a quantized bulk Hall response with 4D symmetry. In a finite-sized system, the 4D topological bulk response is carried by localized edge modes that cross the sample when the synthetic momenta are modulated. We observe this crossing directly through photon pumping of our system from edge to edge and corner to corner. These crossings are equivalent to charge pumping across a 4D system from one three-dimensional hypersurface to the spatially opposite one and from one 2D hyperedge to another. Our results provide a platform for the study of higher-dimensional topological physics.

Photonic topological boundary pumping as a probe of 4D quantum Hall physics

Science.gov (United States)

Zilberberg, Oded; Huang, Sheng; Guglielmon, Jonathan; Wang, Mohan; Chen, Kevin P.; Kraus, Yaacov E.; Rechtsman, Mikael C.

2018-01-01

When a two-dimensional (2D) electron gas is placed in a perpendicular magnetic field, its in-plane transverse conductance becomes quantized; this is known as the quantum Hall effect. It arises from the non-trivial topology of the electronic band structure of the system, where an integer topological invariant (the first Chern number) leads to quantized Hall conductance. It has been shown theoretically that the quantum Hall effect can be generalized to four spatial dimensions, but so far this has not been realized experimentally because experimental systems are limited to three spatial dimensions. Here we use tunable 2D arrays of photonic waveguides to realize a dynamically generated four-dimensional (4D) quantum Hall system experimentally. The inter-waveguide separation in the array is constructed in such a way that the propagation of light through the device samples over momenta in two additional synthetic dimensions, thus realizing a 2D topological pump. As a result, the band structure has 4D topological invariants (known as second Chern numbers) that support a quantized bulk Hall response with 4D symmetry. In a finite-sized system, the 4D topological bulk response is carried by localized edge modes that cross the sample when the synthetic momenta are modulated. We observe this crossing directly through photon pumping of our system from edge to edge and corner to corner. These crossings are equivalent to charge pumping across a 4D system from one three-dimensional hypersurface to the spatially opposite one and from one 2D hyperedge to another. Our results provide a platform for the study of higher-dimensional topological physics.

Effect of Anode Dielectric Coating on Hall Thruster Operation

International Nuclear Information System (INIS)

Dorf, L.; Raitses, Y.; Fisch, N.J.; Semenov, V.

2003-01-01

An interesting phenomenon observed in the near-anode region of a Hall thruster is that the anode fall changes from positive to negative upon removal of the dielectric coating, which is produced on the anode surface during the normal course of Hall thruster operation. The anode fall might affect the thruster lifetime and acceleration efficiency. The effect of the anode coating on the anode fall is studied experimentally using both biased and emissive probes. Measurements of discharge current oscillations indicate that thruster operation is more stable with the coated anode

Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement.

Science.gov (United States)

Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua; Jia, Jin-Feng

2015-05-01

Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO3 surface.

Development of micro-four-point probe in a scanning tunneling microscope for in situ electrical transport measurement

Energy Technology Data Exchange (ETDEWEB)

Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn; Jia, Jin-Feng, E-mail: canhualiu@sjtu.edu.cn, E-mail: jfjia@sjtu.edu.cn [Key Laboratory of Artificial Structures and Quantum Control (Ministry of Education), Department of Physics and Astronomy, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240 (China)

2015-05-15

Electrons at surface may behave differently from those in bulk of a material. Multi-functional tools are essential in comprehensive studies on a crystal surface. Here, we developed an in situ microscopic four-point probe (4PP) transport measurement system on the basis of a scanning tunneling microscope (STM). In particular, convenient replacement between STM tips and micro-4PPs enables systematic investigations of surface morphology, electronic structure, and electrical transport property of a same sample surface. Performances of the instrument are demonstrated with high-quality STM images, tunneling spectra, and low-noise electrical I-V characteristic curves of a single-layer FeSe film grown on a conductive SrTiO{sub 3} surface.

Probing plasmons in three dimensions by combining complementary spectroscopies in a scanning transmission electron microscope

International Nuclear Information System (INIS)

Hachtel, J A; Haglund, R F; Pantelides, S T; Marvinney, C; Mayo, D; Mouti, A; Lupini, A R; Chisholm, M F; Mu, R; Pennycook, S J

2016-01-01

The nanoscale optical response of surface plasmons in three-dimensional metallic nanostructures plays an important role in many nanotechnology applications, where precise spatial and spectral characteristics of plasmonic elements control device performance. Electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) within a scanning transmission electron microscope have proven to be valuable tools for studying plasmonics at the nanoscale. Each technique has been used separately, producing three-dimensional reconstructions through tomography, often aided by simulations for complete characterization. Here we demonstrate that the complementary nature of the two techniques, namely that EELS probes beam-induced electronic excitations while CL probes radiative decay, allows us to directly obtain a spatially- and spectrally-resolved picture of the plasmonic characteristics of nanostructures in three dimensions. The approach enables nanoparticle-by-nanoparticle plasmonic analysis in three dimensions to aid in the design of diverse nanoplasmonic applications. (paper)

Experimental Studies of Anode Sheath Phenomena in a Hall Thruster Discharge

International Nuclear Information System (INIS)

Dorf, L.; Raitses, Y.; Fisch, N.J.

2004-01-01

Both electron-repelling and electron-attracting anode sheaths in a Hall thruster were characterized by measuring the plasma potential with biased and emissive probes [L. Dorf, Y. Raitses, V. Semenov, and N.J. Fisch, Appl. Phys. Let. 84 (2004) 1070]. In the present work, two-dimensional structures of the plasma potential, electron temperature, and plasma density in the near-anode region of a Hall thruster with clean and dielectrically coated anodes are identified. Possible mechanisms of anode sheath formation in a Hall thruster are analyzed. The path for current closure to the anode appears to be the determining factor in the anode sheath formation process. The main conclusion of this work is that the anode sheath formation in Hall thrusters differs essentially from that in the other gas discharge devices, like a glow discharge or a hollow anode, because the Hall thruster utilizes long electron residence times to ionize rather than high neutral pressures

Effective-field-theory model for the fractional quantum Hall effect

International Nuclear Information System (INIS)

Zhang, S.C.; Hansson, T.H.; Kivelson, S.

1989-01-01

Starting directly from the microscopic Hamiltonian, we derive a field-theory model for the fractional quantum hall effect. By considering an approximate coarse-grained version of the same model, we construct a Landau-Ginzburg theory similar to that of Girvin. The partition function of the model exhibits cusps as a function of density and the Hall conductance is quantized at filling factors ν = (2k-1)/sup -1/ with k an arbitrary integer. At these fractions the ground state is incompressible, and the quasiparticles and quasiholes have fractional charge and obey fractional statistics. Finally, we show that the collective density fluctuations are massive

Critical current density analysis of ex situ MgB2 wire by in-field and temperature Hall probe imaging

International Nuclear Information System (INIS)

Bartolome, E; Granados, X; Cambel, V; Fedor, J; Kovac, P; Husek, I

2005-01-01

The irreversible magnetic behaviour at different temperatures of an ex situ Fe-alloy/MgB 2 wire, exhibiting a granular compositional distribution, was studied using an in-field, high resolution Hall probe imaging system. Quantitative information about the local current density was obtained by solving the Biot-Savart inversion problem. The flux penetration and current distribution maps obtained can be attributed to a inhomogeneous compositional 'plum-cake-like' system, consisting of large, isolated MgB 2 agglomerations embedded in a matrix of finely distributed MgB 2 +MgO. The critical current densities within the grains and their evolution with the applied magnetic field and temperature have been obtained, and compared to the mean J c (H,T) in the matrix

An experimental investigation of the internal magnetic field topography of an operating Hall thruster

International Nuclear Information System (INIS)

Peterson, Peter Y.; Gallimore, Alec D.; Haas, James M.

2002-01-01

Magnetic field measurements were made in the discharge channel of the 5 kW-class P5 laboratory-model Hall thruster to investigate what effect the Hall current has on the static, applied magnetic field topography. The P5 was operated at 1.6 and 3.0 kW with a discharge voltage of 300 V. A miniature inductive loop probe (B-Dot probe) was employed to measure the radial magnetic field profile inside the discharge channel of the P5 with and without the plasma discharge. These measurements are accomplished with minimal disturbance to thruster operation with the High-speed Axial Reciprocating Probe system. The results of the B-Dot probe measurements indicate a change in the magnetic field topography from that of the vacuum field measurements. The measured magnetic field profiles are then examined to determine the possible nature and source of the difference between the vacuum and plasma magnetic field profiles

Focused ion beam patterned Hall nano-sensors

International Nuclear Information System (INIS)

Candini, A.; Gazzadi, G.C.; Di Bona, A.; Affronte, M.; Ercolani, D.; Biasiol, G.; Sorba, L.

2007-01-01

By means of focused ion beam milling, we fabricate Hall magnetometers with active areas as small as 100x100nm 2 . The constituent material can either be metallic (Au), semimetallic (Bi) or doped bulk semiconducting (Si doped GaAs). We experimentally show that Au nano-probes can work from room temperature down to liquid helium with magnetic flux sensitivity -1 Φ 0

Microscopic model of quasiparticle wave packets in superfluids, superconductors, and paired Hall states.

Science.gov (United States)

Parameswaran, S A; Kivelson, S A; Shankar, R; Sondhi, S L; Spivak, B Z

2012-12-07

We study the structure of Bogoliubov quasiparticles, bogolons, the fermionic excitations of paired superfluids that arise from fermion (BCS) pairing, including neutral superfluids, superconductors, and paired quantum Hall states. The naive construction of a stationary quasiparticle in which the deformation of the pair field is neglected leads to a contradiction: it carries a net electrical current even though it does not move. However, treating the pair field self-consistently resolves this problem: in a neutral superfluid, a dipolar current pattern is associated with the quasiparticle for which the total current vanishes. When Maxwell electrodynamics is included, as appropriate to a superconductor, this pattern is confined over a penetration depth. For paired quantum Hall states of composite fermions, the Maxwell term is replaced by a Chern-Simons term, which leads to a dipolar charge distribution and consequently to a dipolar current pattern.

Study of mechanically stimulated ferroelectric domain formation using scanning probe microscope

Energy Technology Data Exchange (ETDEWEB)

Kim, J H; Baek, J; Khim, Z G [School of Physics and Nano-Systems Institute, Seoul National University, Seoul 151-747 (Korea, Republic of)

2007-03-15

The stress-related ferroelectric properties have been studied on the Triglycine sulfate (TGS) by scanning probe microscope (SPM). Together with normal stress of the tip, the lateral stress is applied to the sample with piezoelectric transducers. With this study, we characterized the way the ferroelectricity of TGS responds to the axis-specific stress. Specially, the b-directional stress applicable to the surface can amount to several GPa such that the polarization switching by mechanical stress is observable. Although the lateral stress is not strong enough to view such phenomena, a-axis(c-axis) stress still affects the polarization value so as to fortify (lessen) the electric field inside, respectively. These contrasting results can be explained by the sign relation of piezo-coefficients about the individual axis. This work can be a touchstone of future researches in characterizing the electromechanical properties of more popular ferroelectrics such as PZT or BTO.

Optical method for distance and displacement measurements of the probe-sample separation in a scanning near-field optical microscope

International Nuclear Information System (INIS)

Santamaria, L.; Siller, H. R.; Garcia-Ortiz, C. E.; Cortes, R.; Coello, V.

2016-01-01

In this work, we present an alternative optical method to determine the probe-sample separation distance in a scanning near-field optical microscope. The experimental method is based in a Lloyd’s mirror interferometer and offers a measurement precision deviation of ∼100 nm using digital image processing and numerical analysis. The technique can also be strategically combined with the characterization of piezoelectric actuators and stability evaluation of the optical system. It also opens the possibility for the development of an automatic approximation control system valid for probe-sample distances from 5 to 500 μm.

Optical method for distance and displacement measurements of the probe-sample separation in a scanning near-field optical microscope

Energy Technology Data Exchange (ETDEWEB)

Santamaria, L.; Siller, H. R. [Tecnológico de Monterrey, Eugenio Garza Sada 2501 Sur, Monterrey, N.L., 64849 (Mexico); Garcia-Ortiz, C. E., E-mail: cegarcia@cicese.mx [CONACYT Research Fellow – CICESE, Unidad Monterrey, Alianza Centro 504, Apodaca, NL, 66629 (Mexico); Cortes, R.; Coello, V. [CICESE, Unidad Monterrey, PIIT, Alianza Centro 504, Apodaca, NL, 66629 (Mexico)

2016-04-15

In this work, we present an alternative optical method to determine the probe-sample separation distance in a scanning near-field optical microscope. The experimental method is based in a Lloyd’s mirror interferometer and offers a measurement precision deviation of ∼100 nm using digital image processing and numerical analysis. The technique can also be strategically combined with the characterization of piezoelectric actuators and stability evaluation of the optical system. It also opens the possibility for the development of an automatic approximation control system valid for probe-sample distances from 5 to 500 μm.

Proposal for an Experimental Test of the Role of Confining Potentials in the Integral Quantum Hall Effect

OpenAIRE

Brueckner, Reinhold

2000-01-01

We propose an experiment using a three-gate quantum Hall device to probe the dependence of the integral quantum Hall effect (IQHE) on the shape of the lateral confining potential in edge regions. This shape can, in a certain configuration determine whether or not the IQHE occurs.

Reducing Plasma Perturbations with Segmented Metal Shielding on Electrostatic Probes

International Nuclear Information System (INIS)

Staack, D.; Raitses, Y.; Fisch, N.J.

2002-01-01

Electrostatic probes are widely used to measure spatial plasma parameters in the quasi-neutral plasma created in Hall thrusters and similar E x B electric discharge devices. Significant perturbations of the plasma, induced by such probes, can mask the actual physics involved in operation of these devices. In an attempt to reduce these perturbations in Hall thrusters, the perturbations were examined by varying the component material, penetration distance, and residence time of various probe designs. This study leads us to a conclusion that secondary electron emission from insulator ceramic tubes of the probe can affect local changes of the plasma parameters causing plasma perturbations. A probe design, which consists of a segmented metal shielding of the probe insulator, is suggested to reduce these perturbations. This new probe design can be useful for plasma applications in which the electron temperature is sufficient to produce secondary electron emission by interaction of plasma electrons with dielectric materials

Investigations of reactions between pure refractory metals and light gases with the field ion microscope and atom probe

International Nuclear Information System (INIS)

Krautz, E.; Haiml, G.

1989-01-01

The initial stages of selected reactions of the refractory metals tungsten, niobium and tantalum with hydrogen, oxygen, nitrogen and methane have been studied with the field ion microscope in atomic resolution whereby the composition of single net planes converages and surface zones could absolutely be analyzed with the atom probe by using field desorption under defined conditions at low temperatures. 14 refs., 9 figs. (Author)

Development of a detachable high speed miniature scanning probe microscope for large area substrates inspection

Energy Technology Data Exchange (ETDEWEB)

Sadeghian, Hamed, E-mail: hamed.sadeghianmarnani@tno.nl, E-mail: h.sadeghianmarnani@tudelft.nl [Department of Optomechatronics, Netherlands Organization for Scientific Applied Research, TNO, Stieltjesweg 1, 2628 CK Delft (Netherlands); Department of Precision and Microsystems Engineering, Delft University of Technology, Mekelweg 2, 2628 CD Delft (Netherlands); Herfst, Rodolf; Winters, Jasper; Crowcombe, Will; Kramer, Geerten; Dool, Teun van den; Es, Maarten H. van [Department of Optomechatronics, Netherlands Organization for Scientific Applied Research, TNO, Stieltjesweg 1, 2628 CK Delft (Netherlands)

2015-11-15

We have developed a high speed, miniature scanning probe microscope (MSPM) integrated with a Positioning Unit (PU) for accurately positioning the MSPM on a large substrate. This combination enables simultaneous, parallel operation of many units on a large sample for high throughput measurements. The size of the MSPM is 19 × 45 × 70 mm{sup 3}. It contains a one-dimensional flexure stage with counter-balanced actuation for vertical scanning with a bandwidth of 50 kHz and a z-travel range of more than 2 μm. This stage is mechanically decoupled from the rest of the MSPM by suspending it on specific dynamically determined points. The motion of the probe, which is mounted on top of the flexure stage is measured by a very compact optical beam deflection (OBD). Thermal noise spectrum measurements of short cantilevers show a bandwidth of 2 MHz and a noise of less than 15 fm/Hz{sup 1/2}. A fast approach and engagement of the probe to the substrate surface have been achieved by integrating a small stepper actuator and direct monitoring of the cantilever response to the approaching surface. The PU has the same width as the MSPM, 45 mm and can position the MSPM to a pre-chosen position within an area of 275×30 mm{sup 2} to within 100 nm accuracy within a few seconds. During scanning, the MSPM is detached from the PU which is essential to eliminate mechanical vibration and drift from the relatively low-resonance frequency and low-stiffness structure of the PU. Although the specific implementation of the MSPM we describe here has been developed as an atomic force microscope, the general architecture is applicable to any form of SPM. This high speed MSPM is now being used in a parallel SPM architecture for inspection and metrology of large samples such as semiconductor wafers and masks.

ExB Measurements of a 200 W Xenon Hall Thruster (Preprint)

National Research Council Canada - National Science Library

Ekholm, Jared M; Hargus, Jr, William A

2007-01-01

Angularly resolved ion species fractions of Xe+1, Xe+2, and Xe+3 in a low power xenon Hall thruster Busek BHT-200 plume were measured using an ExB probe under a variety of thruster operating conditions and background pressures...

Frequency Response of the Sample Vibration Mode in Scanning Probe Acoustic Microscope

International Nuclear Information System (INIS)

Ya-Jun, Zhao; Qian, Cheng; Meng-Lu, Qian

2010-01-01

Based on the interaction mechanism between tip and sample in the contact mode of a scanning probe acoustic microscope (SPAM), an active mass of the sample is introduced in the mass-spring model. The tip motion and frequency response of the sample vibration mode in the SPAM are calculated by the Lagrange equation with dissipation function. For the silicon tip and glass assemblage in the SPAM the frequency response is simulated and it is in agreement with the experimental result. The living myoblast cells on the glass slide are imaged at resonance frequencies of the SPAM system, which are 20kHz, 30kHz and 120kHz. It is shown that good contrast of SPAM images could be obtained when the system is operated at the resonance frequencies of the system in high and low-frequency regions

Shear force distance control in a scanning near-field optical microscope: in resonance excitation of the fiber probe versus out of resonance excitation

International Nuclear Information System (INIS)

Lapshin, D.A.; Letokhov, V.S.; Shubeita, G.T.; Sekatskii, S.K.; Dietler, G.

2004-01-01

The experimental results of the direct measurement of the absolute value of interaction force between the fiber probe of a scanning near-field optical microscope (SNOM) operated in shear force mode and a sample, which were performed using combined SNOM-atomic force microscope setup, are discussed for the out-of-resonance fiber probe excitation mode. We demonstrate that the value of the tapping component of the total force for this mode at typical dither amplitudes is of the order of 10 nN and thus is quite comparable with the value of this force for in resonance fiber probe excitation mode. It is also shown that for all modes this force component is essentially smaller than the usually neglected static attraction force, which is of the order of 200 nN. The true contact nature of the tip-sample interaction during the out of resonance mode is proven. From this, we conclude that such a detection mode is very promising for operation in liquids, where other modes encounter great difficulties

Interplay between snake and quantum edge states in a graphene Hall bar with a pn-junction

Energy Technology Data Exchange (ETDEWEB)

Milovanović, S. P., E-mail: slavisa.milovanovic@uantwerpen.be; Peeters, F. M., E-mail: francois.peeters@uantwerpen.be [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Ramezani Masir, M., E-mail: mrmphys@gmail.com [Departement Fysica, Universiteit Antwerpen, Groenenborgerlaan 171, B-2020 Antwerpen (Belgium); Department of Physics, University of Texas at Austin, 2515 Speedway, C1600 Austin, Texas 78712-1192 (United States)

2014-09-22

The magneto- and Hall resistance of a locally gated cross shaped graphene Hall bar is calculated. The edge of the top gate is placed diagonally across the center of the Hall cross. Four-probe resistance is calculated using the Landauer-Büttiker formalism, while the transmission coefficients are obtained using the non-equilibrium Green's function approach. The interplay between transport due to edge channels and snake states is investigated. When two edge channels are occupied, we predict oscillations in the Hall and the bend resistance as function of the magnetic field, which are a consequence of quantum interference between the occupied snake states.

Sensitivity study of micro four-point probe measurements on small samples

DEFF Research Database (Denmark)

Wang, Fei; Petersen, Dirch Hjorth; Hansen, Torben Mikael

2010-01-01

probes than near the outer ones. The sensitive area is defined for infinite film, circular, square, and rectangular test pads, and convergent sensitivities are observed for small samples. The simulations show that the Hall sheet resistance RH in micro Hall measurements with position error suppression...

Sub-wavelength imaging by depolarization in a reflection near-field optical microscope using an uncoated fiber probe

DEFF Research Database (Denmark)

Madsen, Steen; Bozhevolnyi, Sergey I.; Hvam, Jørn Märcher

1998-01-01

We present a reflection scanning near-field optical microscope utilizing counter-directional light propagation in an uncoated fiber probe, cross-polarized detection and shear-force feedback. Topographical and near-field optical imaging with a scanning speed of up to 10 mu m/s and a lateral...... resolution better than 40 nm are demonstrated with a latex projection test sample. Determination of the optical resolution as well as correlation between topographical and near-field optical images are discussed. (C) 1998 Elsevier Science B.V....

z calibration of the atomic force microscope by means of a pyramidal tip

DEFF Research Database (Denmark)

Jensen, Flemming

1993-01-01

A new method for imaging the probe tip of an atomic force microscope cantilever by the atomic force microscope itself (self-imaging) is presented. The self-imaging is accomplished by scanning the probe tip across a sharper tip on the surface. By using a pyramidal probe tip with a very well......-defined aspect ratio, this technique provides an excellent z-calibration standard for the atomic force microscope....

Scanning micro-Hall probe mapping of magnetic flux distributions and current densities in YBa{sub 2}Cu{sub 3}O{sub 7}

Energy Technology Data Exchange (ETDEWEB)

Xing, W.; Heinrich, B. [Simon Fraser Univ., British Columbia (Canada); Zhou, H. [CTF Systems, Inc., British Columbia (Canada)] [and others

1994-12-31

Mapping of the magnetic flux density B{sub z} (perpendicular to the film plane) for a YBa{sub 2}Cu{sub 3}O{sub 7} thin-film sample was carried out using a scanning micro-Hall probe. The sheet magnetization and sheet current densities were calculated from the B{sub z} distributions. From the known sheet magnetization, the tangential (B{sub x,y}) and normal components of the flux density B were calculated in the vicinity of the film. It was found that the sheet current density was mostly determined by 2B{sub x,y}/d, where d is the film thickness. The evolution of flux penetration as a function of applied field will be shown.

Electrical control of the anomalous valley Hall effect in antiferrovalley bilayers

Science.gov (United States)

Tong, Wen-Yi; Duan, Chun-Gang

2017-08-01

In analogy to all-electric spintronics, all-electric valleytronics, i.e., valley manipulation via electric means, becomes an exciting new frontier as it may bring revolutions in the field of data storage with ultra-high speed and ultra-low power consumption. The existence of the anomalous valley Hall effect in ferrovalley materials demonstrates the possibility of electrical detection for valley polarization. However, in previously proposed valley-polarized monolayers, the anomalous valley Hall effect is controlled by external magnetic fields. Here, through elaborate structural design, we propose the antiferrovally bilayer as an ideal candidate for realizing all-electric valleytronic devices. Using the minimal k.p model, we show that the energy degeneracy between valley indexes in such system can be lifted by electric approaches. Subsequently, the anomalous valley Hall effect strongly depends on the electric field as well. Taking the bilayer VSe2 as an example, all-electric tuning and detecting of anomalous valley Hall effect is confirmed by density-functional theory calculations, indicating that the valley information in such antiferrovalley bilayer can be reversed by an electric field perpendicular to the plane of the system and easily probed through the sign of the Hall voltage.

A versatile LabVIEW and field-programmable gate array-based scanning probe microscope for in operando electronic device characterization.

Science.gov (United States)

Berger, Andrew J; Page, Michael R; Jacob, Jan; Young, Justin R; Lewis, Jim; Wenzel, Lothar; Bhallamudi, Vidya P; Johnston-Halperin, Ezekiel; Pelekhov, Denis V; Hammel, P Chris

2014-12-01

Understanding the complex properties of electronic and spintronic devices at the micro- and nano-scale is a topic of intense current interest as it becomes increasingly important for scientific progress and technological applications. In operando characterization of such devices by scanning probe techniques is particularly well-suited for the microscopic study of these properties. We have developed a scanning probe microscope (SPM) which is capable of both standard force imaging (atomic, magnetic, electrostatic) and simultaneous electrical transport measurements. We utilize flexible and inexpensive FPGA (field-programmable gate array) hardware and a custom software framework developed in National Instrument's LabVIEW environment to perform the various aspects of microscope operation and device measurement. The FPGA-based approach enables sensitive, real-time cantilever frequency-shift detection. Using this system, we demonstrate electrostatic force microscopy of an electrically biased graphene field-effect transistor device. The combination of SPM and electrical transport also enables imaging of the transport response to a localized perturbation provided by the scanned cantilever tip. Facilitated by the broad presence of LabVIEW in the experimental sciences and the openness of our software solution, our system permits a wide variety of combined scanning and transport measurements by providing standardized interfaces and flexible access to all aspects of a measurement (input and output signals, and processed data). Our system also enables precise control of timing (synchronization of scanning and transport operations) and implementation of sophisticated feedback protocols, and thus should be broadly interesting and useful to practitioners in the field.

Microscopic studies of RIB target materials and ion induced nanostructures

International Nuclear Information System (INIS)

Karmakar, Prasanta; Bhattacharya, Shampa; Roy, Tapatee Kundu; Bhowmick, Debasis; Chakrabarti, Alok

2010-01-01

The invention of electron microscope and scanning probe microscope has empowered us to visualize the tiny world that has explored many fundamental laws of natures. Further technological advancements have made these tools capable to probe micron size structures to individual atom. These microscopes are used to image and study micron size fibers or grain structures used for high yield radioactive products, to few nanometer size ripple, dot and hole structures produced by ion irradiation. Electron Microscope has also been used to characterize the ion beam synthesized dilute magnetic systems

Hall effect measurement for precise sheet resistance and thickness evaluation of Ruthenium thin films using non-equidistant four-point probes

Directory of Open Access Journals (Sweden)

Frederik Westergaard Østerberg

2018-05-01

Full Text Available We present a new micro Hall effect measurement method using non-equidistant electrodes. We show theoretically and verify experimentally that it is advantageous to use non-equidistant electrodes for samples with low Hall sheet resistance. We demonstrate the new method by experiments where Hall sheet carrier densities and Hall mobilities of Ruthenium thin films (3-30 nm are determined. The measurements show that it is possible to measure Hall mobilities as low as 1 cm2V−1s−1 with a relative standard deviation of 2-3%. We show a linear relation between measured Hall sheet carrier density and film thickness. Thus, the method can be used to monitor thickness variations of ultra-thin metal films.

Accurate Extraction of Charge Carrier Mobility in 4-Probe Field-Effect Transistors

KAUST Repository

Choi, Hyun Ho; Rodionov, Yaroslav I.; Paterson, Alexandra F.; Panidi, Julianna; Saranin, Danila; Kharlamov, Nikolai; Didenko, Sergei I.; Anthopoulos, Thomas D.; Cho, Kilwon; Podzorov, Vitaly

2018-01-01

Charge carrier mobility is an important characteristic of organic field-effect transistors (OFETs) and other semiconductor devices. However, accurate mobility determination in FETs is frequently compromised by issues related to Schottky-barrier contact resistance, that can be efficiently addressed by measurements in 4-probe/Hall-bar contact geometry. Here, it is shown that this technique, widely used in materials science, can still lead to significant mobility overestimation due to longitudinal channel shunting caused by voltage probes in 4-probe structures. This effect is investigated numerically and experimentally in specially designed multiterminal OFETs based on optimized novel organic-semiconductor blends and bulk single crystals. Numerical simulations reveal that 4-probe FETs with long but narrow channels and wide voltage probes are especially prone to channel shunting, that can lead to mobilities overestimated by as much as 350%. In addition, the first Hall effect measurements in blended OFETs are reported and how Hall mobility can be affected by channel shunting is shown. As a solution to this problem, a numerical correction factor is introduced that can be used to obtain much more accurate experimental mobilities. This methodology is relevant to characterization of a variety of materials, including organic semiconductors, inorganic oxides, monolayer materials, as well as carbon nanotube and semiconductor nanocrystal arrays.

Accurate Extraction of Charge Carrier Mobility in 4-Probe Field-Effect Transistors

KAUST Repository

Choi, Hyun Ho

2018-04-30

Charge carrier mobility is an important characteristic of organic field-effect transistors (OFETs) and other semiconductor devices. However, accurate mobility determination in FETs is frequently compromised by issues related to Schottky-barrier contact resistance, that can be efficiently addressed by measurements in 4-probe/Hall-bar contact geometry. Here, it is shown that this technique, widely used in materials science, can still lead to significant mobility overestimation due to longitudinal channel shunting caused by voltage probes in 4-probe structures. This effect is investigated numerically and experimentally in specially designed multiterminal OFETs based on optimized novel organic-semiconductor blends and bulk single crystals. Numerical simulations reveal that 4-probe FETs with long but narrow channels and wide voltage probes are especially prone to channel shunting, that can lead to mobilities overestimated by as much as 350%. In addition, the first Hall effect measurements in blended OFETs are reported and how Hall mobility can be affected by channel shunting is shown. As a solution to this problem, a numerical correction factor is introduced that can be used to obtain much more accurate experimental mobilities. This methodology is relevant to characterization of a variety of materials, including organic semiconductors, inorganic oxides, monolayer materials, as well as carbon nanotube and semiconductor nanocrystal arrays.

Operation of a scanning near field optical microscope in reflection in combination with a scanning force microscope

NARCIS (Netherlands)

van Hulst, N.F.; Moers, M.H.P.; Moers, M.H.P.; Noordman, O.F.J.; Noordman, O.F.J.; Faulkner, T.; Segerink, Franciscus B.; van der Werf, Kees; de Grooth, B.G.; Bölger, B.; Bölger, B.

1992-01-01

Images obtained with a scanning near field optical microscope (SNOM) operating in reflection are presented. We have obtained the first results with a SiN tip as optical probe. The instrument is simultaneously operated as a scanning force microscope (SFM). Moreover, the instrument incorporates an

Accuracy of micro four-point probe measurements on inhomogeneous samples: A probe spacing dependence study

DEFF Research Database (Denmark)

Wang, Fei; Petersen, Dirch Hjorth; Østerberg, Frederik Westergaard

2009-01-01

In this paper, we discuss a probe spacing dependence study in order to estimate the accuracy of micro four-point probe measurements on inhomogeneous samples. Based on sensitivity calculations, both sheet resistance and Hall effect measurements are studied for samples (e.g. laser annealed samples...... the probe spacing is smaller than 1/40 of the variation wavelength, micro four-point probes can provide an accurate record of local properties with less than 1% measurement error. All the calculations agree well with previous experimental results.......) with periodic variations of sheet resistance, sheet carrier density, and carrier mobility. With a variation wavelength of ¿, probe spacings from 0.0012 to 1002 have been applied to characterize the local variations. The calculations show that the measurement error is highly dependent on the probe spacing. When...

Disorder effect on chiral edge modes and anomalous Hall conductance in Weyl semimetals

International Nuclear Information System (INIS)

Takane, Yositake

2016-01-01

Typical Weyl semimetals host chiral surface states and hence show an anomalous Hall response. Although a Weyl semimetal phase is known to be robust against weak disorder, the effect of disorder on chiral states has not been fully clarified so far. We study the behavior of such chiral states in the presence of disorder and its consequences on an anomalous Hall response, focusing on a thin slab of Weyl semimetal with chiral surface states along its edge. It is shown that weak disorder does not disrupt chiral edge states but crucially affects them owing to the renormalization of a mass parameter: the number of chiral edge states changes depending on the strength of disorder. It is also shown that the Hall conductance is quantized when the Fermi level is located near Weyl nodes within a finite-size gap. This quantization of the Hall conductance collapses once the strength of disorder exceeds a critical value, suggesting that it serves as a probe to distinguish a Weyl semimetal phase from a diffusive anomalous Hall metal phase. (author)

Tunneling Spectroscopy of Quantum Hall States in Bilayer Graphene

Science.gov (United States)

Wang, Ke; Harzheim, Achim; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip

In the quantum Hall (QH) regime, ballistic conducting paths along the physical edges of a sample appear, leading to quantized Hall conductance and vanishing longitudinal magnetoconductance. These QH edge states are often described as ballistic compressible strips separated by insulating incompressible strips, the spatial profiles of which can be crucial in understanding the stability and emergence of interaction driven QH states. In this work, we present tunneling transport between two QH edge states in bilayer graphene. Employing locally gated device structure, we guide and control the separation between the QH edge states in bilayer graphene. Using resonant Landau level tunneling as a spectroscopy tool, we measure the energy gap in bilayer graphene as a function of displacement field and probe the emergence and evolution of incompressible strips.

AdS/QHE: towards a holographic description of quantum Hall experiments

International Nuclear Information System (INIS)

Bayntun, Allan; Burgess, C P; Lee, Sung-Sik; Dolan, Brian P

2011-01-01

Transitions among quantum Hall plateaux share a suite of remarkable experimental features, such as semicircle laws and duality relations, whose accuracy and robustness are difficult to explain directly in terms of the detailed dynamics of the microscopic electrons. They would naturally follow if the low-energy transport properties were governed by an emergent discrete duality group relating the different plateaux, but no explicit examples of interacting systems having such a group are known. Recent progress using the AdS/CFT correspondence has identified examples with similar duality groups, but without the dc ohmic conductivity characteristic of quantum Hall experiments. We use this to propose a simple holographic model for low-energy quantum Hall systems, with a nonzero dc conductivity that automatically exhibits all of the observed consequences of duality, including the existence of the plateaux and the semicircle transitions between them. The model can be regarded as a strongly coupled analogue of the old 'composite boson' picture of quantum Hall systems. Non-universal features of the model can be used to test whether it describes actual materials, and we comment on some of these in our proposed model. In particular, the model indicates the value 2/5 for low-temperature scaling exponents for transitions among quantum Hall plateaux, in agreement with the measured value 0.42±0.01.

Pulsed eddy current differential probe to detect the defects in a stainless steel pipe

Science.gov (United States)

Angani, C. S.; Park, D. G.; Kim, C. G.; Leela, P.; Kishore, M.; Cheong, Y. M.

2011-04-01

Pulsed eddy current (PEC) is an electromagnetic nondestructive technique widely used to detect and quantify the flaws in conducting materials. In the present study a differential Hall-sensor probe which is used in the PEC system has been fabricated for the detection of defects in stainless steel pipelines. The differential probe has an exciting coil with two Hall-sensors. A stainless steel test sample with electrical discharge machining (EDM) notches under different depths of 1-5 mm was made and the sample was laminated by plastic insulation having uniform thickness to simulate the pipelines in nuclear power plants (NPPs). The driving coil in the probe is excited by a rectangular current pulse and the resultant response, which is the difference of the two Hall-sensors, has been detected as the PEC probe signal. The discriminating time domain features of the detected pulse such as peak value and time to zero are used to interpret the experimental results with the defects in the test sample. A feature extraction technique such as spectral power density has been devised to infer the PEC response.

Effet Hall quantique, liquides de Luttinger et charges fractionnaires

Science.gov (United States)

Roche, Patrice; Rodriguez, V.; Glattli, D. Christian

We review some basic properties of the Fractional Quantum Hall Effect and particularly address the physics of the edge states. The chiral Luttinger liquid properties of the edges are discussed and probed experimentally using transport measurements. Shot noise measurements, which allow determination of the quasiparticle charge are also discussed. To cite this article: P. Roche et al., C. R. Physique 3 (2002) 717-732.

Real time drift measurement for colloidal probe atomic force microscope: a visual sensing approach

Energy Technology Data Exchange (ETDEWEB)

Wang, Yuliang, E-mail: wangyuliang@buaa.edu.cn; Bi, Shusheng [Robotics Institute, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191 (China); Wang, Huimin [Department of Materials Science and Engineering, The Ohio State University, 2041 College Rd., Columbus, OH 43210 (United States)

2014-05-15

Drift has long been an issue in atomic force microscope (AFM) systems and limits their ability to make long time period measurements. In this study, a new method is proposed to directly measure and compensate for the drift between AFM cantilevers and sample surfaces in AFM systems. This was achieved by simultaneously measuring z positions for beads at the end of an AFM colloidal probe and on sample surface through an off-focus image processing based visual sensing method. The working principle and system configuration are presented. Experiments were conducted to validate the real time drift measurement and compensation. The implication of the proposed method for regular AFM measurements is discussed. We believe that this technique provides a practical and efficient approach for AFM experiments requiring long time period measurement.

Topological phase transitions and quantum Hall effect in the graphene family

Science.gov (United States)

Ledwith, P.; Kort-Kamp, W. J. M.; Dalvit, D. A. R.

2018-04-01

Monolayer staggered materials of the graphene family present intrinsic spin-orbit coupling and can be driven through several topological phase transitions using external circularly polarized lasers and static electric or magnetic fields. We show how topological features arising from photoinduced phase transitions and the magnetic-field-induced quantum Hall effect coexist in these materials and simultaneously impact their Hall conductivity through their corresponding charge Chern numbers. We also show that the spectral response of the longitudinal conductivity contains signatures of the various phase-transition boundaries, that the transverse conductivity encodes information about the topology of the band structure, and that both present resonant peaks which can be unequivocally associated with one of the four inequivalent Dirac cones present in these materials. This complex optoelectronic response can be probed with straightforward Faraday rotation experiments, allowing the study of the crossroads between quantum Hall physics, spintronics, and valleytronics.

Investigation of the Radial Compression of Carbon Nanotubes with a Scanning Probe Microscope

Science.gov (United States)

Shen, Weidian; Jiang, Bin; Han, Bao Shan; Xie, Si-Shen

2001-03-01

Carbon nanotubes have attracted great interest since they were first synthesized. The tubes have substantial promise in a variety of applications due to their unique properties. Efforts have been made to characterize the mechanical properties of the tubes. However, previous work has concentrated on the tubes’ longitudinal properties, and studies of their radial properties lag behind. We have operated a scanning probe microscope, NanoScopeTM IIIa, in the indentation/scratching mode to carry out a nanoindentation test on the top of multiwalled carbon nanotubes. We measured the correlation between the radial stress and the tube compression, and thereby determined the radial compressive elastic modulus at different compressive forces. The measurements also allowed us to estimate the radial compressive strength of the tubes. Support of this work by an Eastern Michigan University Faculty Research Fellowship and by the K. C. Wong Education Foundation, Hong Kong is gratefully acknowledged.

ac driving amplitude dependent systematic error in scanning Kelvin probe microscope measurements: Detection and correction

International Nuclear Information System (INIS)

Wu Yan; Shannon, Mark A.

2006-01-01

The dependence of the contact potential difference (CPD) reading on the ac driving amplitude in scanning Kelvin probe microscope (SKPM) hinders researchers from quantifying true material properties. We show theoretically and demonstrate experimentally that an ac driving amplitude dependence in the SKPM measurement can come from a systematic error, and it is common for all tip sample systems as long as there is a nonzero tracking error in the feedback control loop of the instrument. We further propose a methodology to detect and to correct the ac driving amplitude dependent systematic error in SKPM measurements. The true contact potential difference can be found by applying a linear regression to the measured CPD versus one over ac driving amplitude data. Two scenarios are studied: (a) when the surface being scanned by SKPM is not semiconducting and there is an ac driving amplitude dependent systematic error; (b) when a semiconductor surface is probed and asymmetric band bending occurs when the systematic error is present. Experiments are conducted using a commercial SKPM and CPD measurement results of two systems: platinum-iridium/gap/gold and platinum-iridium/gap/thermal oxide/silicon are discussed

Observation of the Zero Hall Plateau in a Quantum Anomalous Hall Insulator

Energy Technology Data Exchange (ETDEWEB)

Feng, Yang; Feng, Xiao; Ou, Yunbo; Wang, Jing; Liu, Chang; Zhang, Liguo; Zhao, Dongyang; Jiang, Gaoyuan; Zhang, Shou-Cheng; He, Ke; Ma, Xucun; Xue, Qi-Kun; Wang, Yayu

2015-09-16

We report experimental investigations on the quantum phase transition between the two opposite Hall plateaus of a quantum anomalous Hall insulator. We observe a well-defined plateau with zero Hall conductivity over a range of magnetic field around coercivity when the magnetization reverses. The features of the zero Hall plateau are shown to be closely related to that of the quantum anomalous Hall effect, but its temperature evolution exhibits a significant difference from the network model for a conventional quantum Hall plateau transition. We propose that the chiral edge states residing at the magnetic domain boundaries, which are unique to a quantum anomalous Hall insulator, are responsible for the novel features of the zero Hall plateau.

Secondary mineralization in carious lesions of human dentin. Electron-probe, electron microscope, and electron diffraction studies

Energy Technology Data Exchange (ETDEWEB)

Ogiwara, H [Tokyo Dental Coll. (Japan)

1975-02-01

Dentinal carious lesions having a remineralized surface layer were studied by means electron-probe microanalysis, electron microscopy, electron diffraction. As the results of electron-probe study, F, Mg, and Na were found to be distributed mainly in the remineralized surface layer and S in the decalcified region where decreases in Ca, P, and Mg concentration were usually observed. The decrease in Mg concentration always started earlier than that of Ca and P concentration. Electron microscope and electron diffraction studies revealed that apatic crystals in the remineralized surface layer were much larger than those in the intact dentin. Although they were less conspicuous, crystals in the decalcified region also were larger than those in the intact region. Dentinal tubules, occluded by many crystals, were frequently seen during the observations. Crystals in the tubules varied in morphology, showing granular, needle, rhomboid, and tabular shapes. By means of electron diffraction, the granular- or needle-shaped crystals were identified as apatite and the rhomboid-shaped crystals as whitlockite. Some of the tabular-shaped crystals appeared to be cotacalcium phosphate.

Circularly polarized near-field optical mapping of spin-resolved quantum Hall chiral edge states.

Science.gov (United States)

Mamyouda, Syuhei; Ito, Hironori; Shibata, Yusuke; Kashiwaya, Satoshi; Yamaguchi, Masumi; Akazaki, Tatsushi; Tamura, Hiroyuki; Ootuka, Youiti; Nomura, Shintaro

2015-04-08

We have successfully developed a circularly polarized near-field scanning optical microscope (NSOM) that enables us to irradiate circularly polarized light with spatial resolution below the diffraction limit. As a demonstration, we perform real-space mapping of the quantum Hall chiral edge states near the edge of a Hall-bar structure by injecting spin polarized electrons optically at low temperature. The obtained real-space mappings show that spin-polarized electrons are injected optically to the two-dimensional electron layer. Our general method to locally inject spins using a circularly polarized NSOM should be broadly applicable to characterize a variety of nanomaterials and nanostructures.

Development of the Atomic-Resolution Environmental Transmission Electron Microscope

DEFF Research Database (Denmark)

Gai, Pratibha L.; Boyes, Edward D.; Yoshida, Kenta

2016-01-01

The development of the novel atomic-resolution environmental transmission electron microscope (atomic-resolution ETEM) for directly probing dynamic gas–solid reactions in situ at the atomic level under controlled reaction conditions consisting of gas environment and elevated temperatures is descr......The development of the novel atomic-resolution environmental transmission electron microscope (atomic-resolution ETEM) for directly probing dynamic gas–solid reactions in situ at the atomic level under controlled reaction conditions consisting of gas environment and elevated temperatures...... is used to study steels, graphene, nanowires, etc. In this chapter, the experimental setup of the microscope column and its peripherals are described....

Experimental and theoretical studies of cylindrical Hall thrusters

International Nuclear Information System (INIS)

Smirnov, Artem; Raitses, Yegeny; Fisch, Nathaniel J.

2007-01-01

The Hall thruster is a mature electric propulsion device that holds considerable promise in terms of the propellant saving potential. The annular design of the conventional Hall thruster, however, does not naturally scale to low power. The efficiency tends to be lower and the lifetime issues are more aggravated. Cylindrical geometry Hall thrusters have lower surface-to-volume ratio than conventional thrusters and, thus, seem to be more promising for scaling down. The cylindrical Hall thruster (CHT) is fundamentally different from the conventional design in the way the electrons are confined and the ion space charge is neutralized. The performances of both the large (9-cm channel diameter, 600-1000 W) and miniaturized (2.6-cm channel diameter, 50-300 W) CHTs are comparable with those of the state-of-the-art conventional (annular) design Hall thrusters of similar sizes. A comprehensive experimental and theoretical study of the CHT physics has been conducted, addressing the questions of electron cross-field transport, propellant ionization, plasma-wall interaction, and formation of the electron distribution function. Probe measurements in the harsh plasma environment of the microthruster were performed. Several interesting effects, such as the unusually high ionization efficiency and enhanced electron transport, were observed. Kinetic simulations suggest the existence of the strong fluctuation-enhanced electron diffusion and predict the non-Maxwellian shape of the electron distribution function. Through the acquired understanding of the new physics, ways for further optimization of this means for low-power space propulsion are suggested. Substantial flexibility in the magnetic field configuration of the CHT is the key tool in achieving the high-efficiency operation

Microscopic investigation of InGaN/GaN heterostructure laser diode degradation using Kelvin probe force microscopy

International Nuclear Information System (INIS)

Lochthofen, A; Mertin, W; Bacher, G; Furitsch, M; Bruederl, G; Strauss, U; Haerle, V

2008-01-01

We report on Kelvin probe force microscopy (KPFM) measurements on fresh and artificially aged InGaN/GaN laser test structures. In the case of an unbiased laser diode, a comparison of the surface potential between a fresh and a stressed laser diode shows a pronounced modification of the laser facet due to the aging process. Performing KPFM measurements under forward bias, a correlation between the macroscopic I-V characteristics and the microscopic voltage drop across the heterostructure layer sequence is found. This clearly demonstrates the potential of KPFM for investigating InGaN/GaN laser diode degradation

Sensitivity of resistive and Hall measurements to local inhomogeneities

DEFF Research Database (Denmark)

Koon, Daniel W.; Wang, Fei; Petersen, Dirch Hjorth

2014-01-01

We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. ...... simulations on both a linear four-point probe array on a large circular disc and a van der Pauw square geometry. Furthermore, the results also agree well with Náhlík et al. published experimental results for physical holes in a circular copper foil disc.......We derive exact, analytic expressions for the sensitivity of sheet resistance and Hall sheet resistance measurements to local inhomogeneities for the cases of nonzero magnetic fields, strong perturbations, and perturbations over a finite area, extending our earlier results on weak perturbations. We...

Effect of the interaction conditions of the probe of an atomic-force microscope with the n-GaAs surface on the triboelectrization phenomenon

Energy Technology Data Exchange (ETDEWEB)

Baklanov, A. V., E-mail: baklanov@mail.ioffe.ru [St. Petersburg State Polytechnical University, Institute of Physics, Nanotechnology, and Telecommunications (Russian Federation); Gutkin, A. A.; Kalyuzhnyy, N. A. [Russian Academy of Sciences, Ioffe Institute (Russian Federation); Brunkov, P. N. [St. Petersburg State Polytechnical University, Institute of Physics, Nanotechnology, and Telecommunications (Russian Federation)

2015-08-15

Triboelectrization as a result of the scanning of an atomic-force-microscope probe over an n-GaAs surface in the contact mode is investigated. The dependences of the local potential variation on the scanning rate and the pressing force of the probe are obtained. The results are explained by point-defect formation in the surface layers of samples under the effect of deformation of these layers during probe scanning. The charge localized at these defects in the case of equilibrium changes the potential of surface, which is subject to triboelectrization. It is shown that, for qualitative explanation of the observed dependences, it is necessary to take into account both the generation and annihilation of defects in the region experiencing deformation.

Temperature Gradient in Hall Thrusters

International Nuclear Information System (INIS)

Staack, D.; Raitses, Y.; Fisch, N.J.

2003-01-01

Plasma potentials and electron temperatures were deduced from emissive and cold floating probe measurements in a 2 kW Hall thruster, operated in the discharge voltage range of 200-400 V. An almost linear dependence of the electron temperature on the plasma potential was observed in the acceleration region of the thruster both inside and outside the thruster. This result calls into question whether secondary electron emission from the ceramic channel walls plays a significant role in electron energy balance. The proportionality factor between the axial electron temperature gradient and the electric field is significantly smaller than might be expected by models employing Ohmic heating of electrons

Intrinsic spin and momentum relaxation in organic single-crystalline semiconductors probed by ESR and Hall measurements

Science.gov (United States)

Tsurumi, Junto; Häusermann, Roger; Watanabe, Shun; Mitsui, Chikahiko; Okamoto, Toshihiro; Matsui, Hiroyuki; Takeya, Jun

Spin and charge momentum relaxation mechanism has been argued among organic semiconductors with various methods, devices, and materials. However, little is known in organic single-crystalline semiconductors because it has been hard to obtain an ideal organic crystal with an excellent crystallinity and controllability required for accurate measurements. By using more than 1-inch sized single crystals which are fabricated via contentious edge-casting method developed by our group, we have successfully demonstrated a simultaneous determination of spin and momentum relaxation time for gate-induced charges of 3,11-didecyldinaphtho[2,3- d:2',3'- d']benzo[1,2- b:4,5- b']dithiophene, by combining electron spin resonance (ESR) and Hall effect measurements. The obtained temperature dependences of spin and momentum relaxation times are in good agreement in terms of power law with a factor of approximately -2. It is concluded that Elliott-Yafet spin relaxation mechanism can be dominant at room temperature regime (200 - 300 K). Probing characteristic time scales such as spin-lattice, spin-spin, and momentum relaxation times, demonstrated in the present work, would be a powerful tool to elucidate fundamental spin and charge transport mechanisms. We acknowledge the New Energy and Industrial Technology Developing Organization (NEDO) for financial support.

Femtosecond photoelectron point projection microscope

International Nuclear Information System (INIS)

Quinonez, Erik; Handali, Jonathan; Barwick, Brett

2013-01-01

By utilizing a nanometer ultrafast electron source in a point projection microscope we demonstrate that images of nanoparticles with spatial resolutions of the order of 100 nanometers can be obtained. The duration of the emission process of the photoemitted electrons used to make images is shown to be of the order of 100 fs using an autocorrelation technique. The compact geometry of this photoelectron point projection microscope does not preclude its use as a simple ultrafast electron microscope, and we use simple analytic models to estimate temporal resolutions that can be expected when using it as a pump-probe ultrafast electron microscope. These models show a significant increase in temporal resolution when comparing to ultrafast electron microscopes based on conventional designs. We also model the microscopes spectroscopic abilities to capture ultrafast phenomena such as the photon induced near field effect

Surface characterization of superconductive Nd1Ba2Cu3Oy thin films using scanning probe microscopes

International Nuclear Information System (INIS)

Ting, W.; Badaye, M.; Itti, R.; Morishita, T.; Koshizuka, N.; Tanaka, S.

1996-01-01

Recently, superconductive Nd 1 Ba 2 Cu 3 O y (Nd123) thin films with high superconducting transition temperature (T c ) have been successfully fabricated at the authors institute employing the standard laser ablation method. In this paper, they report parts of the results of surface characterization of the Nd123 thin films using an ultrahigh vacuum scanning tunneling microscope/spectroscopy (UHV-STM/STS) and an atomic force microscope (AFM) system operated in air. Clear spiral pattern is observed on the surfaces of Nd123 thin films by STM and AFM, suggesting that films are formed by two-dimensional island growth mode at the final growing stage. Contour plots of the spirals show that the step heights of the spirals are not always the integer or half integer numbers of the c-axis parameter of the structure. This implies that the surface natural termination layer of the films may not be unique. Surface atomic images of the as-prepared Nd123 thin films are obtained employing both STM and AFM. STS measurements show that most of the surfaces are semiconductive, or sometimes even metallic. The results of STS measurements together with the fact that they are able to see the surface atomic images using scanning probe microscopes suggest that exposure to air does not cause serious degradation to the as-prepared surfaces of Nd123 thin films

Anomalous Integer Quantum Hall Effect in the Ballistic Regime with Quantum Point Contacts

NARCIS (Netherlands)

Wees, B.J. van; Willems, E.M.M.; Harmans, C.J.P.M.; Beenakker, C.W.J.; Houten, H. van; Williamson, J.G.; Foxon, C.T.; Harris, J.J.

1989-01-01

The Hall conductance of a wide two-dimensional electron gas has been measured in a geometry in which two quantum point contacts form controllable current and voltage probes, separated by less than the transport mean free path. Adjustable barriers in the point contacts allow selective population and

Probing the interaction of microscopic material defects with quasiparticles using a superconducting qubit

Energy Technology Data Exchange (ETDEWEB)

Bilmes, Alexander; Lisenfeld, Juergen; Weiss, Georg; Ustinov, Alexey V. [PI, Fakultaet fuer Physik, KIT, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe (Germany); Heimes, Andreas; Zanker, Sebastian; Schoen, Gerd [TFP, Fakultaet fuer Physik, KIT, Wolfgang-Gaede-Strasse 1, 76131 Karlsruhe (Germany)

2015-07-01

Two-Level-Systems (TLS) are one of the main sources of decoherence in superconducting nano-scale devices such as SQUIDs, photon detectors, resonators and quantum bits (qubits), although the TLS' microscopic nature remains unclear. We use a superconducting phase qubit to detect TLS contained within the tunnel barrier of the qubit's Josephson junction. We coherently operate individual TLS by resonant microwave pulses and access their quantum state by utilizing their strong coupling to the qubit. Our previous measurements of TLS coherence in dependence of the temperature indicate that quasiparticles may give rise to TLS energy loss and dephasing. Here, we probe the TLS-quasiparticle interaction using a reliable method of in-situ quasiparticle injection via an on-chip dc-SQUID that is pulse-biased beyond its critical current. The quasiparticle density is calibrated by measuring associated characteristic changes to the qubit's resonance frequency and energy relaxation rate. We will present experimental data that clearly show the influence of quasiparticles on TLS coherence.

Patterning a hydrogen-bonded molecular monolayer with a hand-controlled scanning probe microscope

Directory of Open Access Journals (Sweden)

Matthew F. B. Green

2014-10-01

Full Text Available One of the paramount goals in nanotechnology is molecular-scale functional design, which includes arranging molecules into complex structures at will. The first steps towards this goal were made through the invention of the scanning probe microscope (SPM, which put single-atom and single-molecule manipulation into practice for the first time. Extending the controlled manipulation to larger molecules is expected to multiply the potential of engineered nanostructures. Here we report an enhancement of the SPM technique that makes the manipulation of large molecular adsorbates much more effective. By using a commercial motion tracking system, we couple the movements of an operator's hand to the sub-angstrom precise positioning of an SPM tip. Literally moving the tip by hand we write a nanoscale structure in a monolayer of large molecules, thereby showing that our method allows for the successful execution of complex manipulation protocols even when the potential energy surface that governs the interaction behaviour of the manipulated nanoscale object(s is largely unknown.

Development and Optical Testing of the Camera, Hand Lens, and Microscope Probe with Scannable Laser Spectroscopy (CHAMP-SLS)

Science.gov (United States)

Mungas, Greg S.; Gursel, Yekta; Sepulveda, Cesar A.; Anderson, Mark; La Baw, Clayton; Johnson, Kenneth R.; Deans, Matthew; Beegle, Luther; Boynton, John

2008-01-01

Conducting high resolution field microscopy with coupled laser spectroscopy that can be used to selectively analyze the surface chemistry of individual pixels in a scene is an enabling capability for next generation robotic and manned spaceflight missions, civil, and military applications. In the laboratory, we use a range of imaging and surface preparation tools that provide us with in-focus images, context imaging for identifying features that we want to investigate at high magnification, and surface-optical coupling that allows us to apply optical spectroscopic analysis techniques for analyzing surface chemistry particularly at high magnifications. The camera, hand lens, and microscope probe with scannable laser spectroscopy (CHAMP-SLS) is an imaging/spectroscopy instrument capable of imaging continuously from infinity down to high resolution microscopy (resolution of approx. 1 micron/pixel in a final camera format), the closer CHAMP-SLS is placed to a feature, the higher the resultant magnification. At hand lens to microscopic magnifications, the imaged scene can be selectively interrogated with point spectroscopic techniques such as Raman spectroscopy, microscopic Laser Induced Breakdown Spectroscopy (micro-LIBS), laser ablation mass-spectrometry, Fluorescence spectroscopy, and/or Reflectance spectroscopy. This paper summarizes the optical design, development, and testing of the CHAMP-SLS optics.

Comparing the photocatalytic activity of TiO2 at macro- and microscopic scales

DEFF Research Database (Denmark)

Torras-Rosell, Antoni; Johannsen, Sabrina Rostgaard; Dirscherl, Kai

2016-01-01

. The photocatalytic properties of TiO2 at macro- and microscopic scales are investigated by comparing photocatalytic degradation of acetone and electrochemical experiments to Kelvin probe force microscopy. The good agreement between the macro- and microscopic experiments suggests that Kelvin probe force microscopy...

Fast micro Hall effect measurements on small pads

DEFF Research Database (Denmark)

Østerberg, Frederik Westergaard; Petersen, Dirch Hjorth; Nielsen, Peter F.

2011-01-01

Sheet resistance, carrier mobility, and sheet carrier density are important parameters in semiconductor production, and it is therefore important to be able to rapidly and accurately measure these parameters even on small samples or pads. The interpretation of four-point probe measurements on small...... pads is non-trivial. In this paper we discuss how conformal mapping can be used to evaluate theoretically expected measurement values on small pads. Theoretical values calculated from analytical mappings of simple geometries are compared to the values found from the numerical conformal mapping...... of a square onto the infinite half-plane, where well-established solutions are known. Hall effect measurements are performed to show, experimentally, that it is possible to measure Hall mobility in less than one minute on squares as small as 7070 lm2 with a deviation of 66.5% on a 1r level from accurate...

Tunneling between edge states in a quantum spin Hall system.

Science.gov (United States)

Ström, Anders; Johannesson, Henrik

2009-03-06

We analyze a quantum spin Hall device with a point contact connecting two of its edges. The contact supports a net spin tunneling current that can be probed experimentally via a two-terminal resistance measurement. We find that the low-bias tunneling current and the differential conductance exhibit scaling with voltage and temperature that depend nonlinearly on the strength of the electron-electron interaction.

Experimental halls workshop summary

International Nuclear Information System (INIS)

Thorndike, A.

1976-01-01

On May 26 and 27, 1976, approximately 50 people met for an informal workshop on plans for experimental halls for ISABELLE. Plans as they exist in the May 1976 version of the ISABELLE proposal were presented. Discussions were held on the following four general topics by separate working groups: (1) pros and cons of open areas as compared with enclosed halls; (2) experimental hall needs of ep, anti pp, and other options; (3) hall for the lepton detector; and (4) hall for the hadron spectrometer. The planning for experimental halls at PEP, the hall for the lepton detector, the hadron spectrometer, and open areas are discussed

Quantitative characterization of semiconductor structures with a scanning microwave microscope.

Science.gov (United States)

Korolyov, S A; Reznik, A N

2018-02-01

In this work, our earlier method for measuring resistance R sh of semiconductor films with a near-field scanning microwave microscope [A. N. Reznik and S. A. Korolyov, J. Appl. Phys. 119, 094504 (2016)] is studied in a 0.1 kΩ/sq microscope model in the form of a monopole or dipole antenna interacting with an arbitrary layered structure. The model fitting parameters are determined from the data yielded by calibration measurements on a system of etalon samples. The performance of the method was analyzed experimentally, using strip-probe and coaxial-probe microscopes in the frequency range of 1-3 GHz. For test structures, we used doped GaN films on the Al 2 O 3 substrate and also transistor structures based on the AlGaN/GaN heterojunction and AlGaAs/GaAs/InGaAs/GaAs/AlGaAs quantum well with a conducting channel. The obtained microwave microscope data were compared with the results of measurements by the van der Pauw method. At the first stage of the experiment, the calibration etalons were bulk homogeneous samples with different permittivity/conductivity values. In this case, satisfactory agreement between the microscope and the van der Pauw data was obtained with a strip probe on all tested samples in the entire range of R sh . With a coaxial probe, such accordance was observed only in high-ohmic samples with R sh > 1 kΩ/sq. The use of GaN film structures as a calibration system helped to increase the accuracy of the coaxial-probe-aided measurement of R sh to a level of ∼10%.

Internal plasma potential measurements of a Hall thruster using xenon and krypton propellant

International Nuclear Information System (INIS)

Linnell, Jesse A.; Gallimore, Alec D.

2006-01-01

For krypton to become a realistic option for Hall thruster operation, it is necessary to understand the performance gap between xenon and krypton and what can be done to reduce it. A floating emissive probe is used with the Plasmadynamics and Electric Propulsion Laboratory's High-speed Axial Reciprocating Probe system to map the internal plasma potential structure of the NASA-173Mv1 Hall thruster [R. R. Hofer, R. S. Jankovsky, and A. D. Gallimore, J. Propulsion Power 22, 721 (2006); and ibid.22, 732 (2006)] using xenon and krypton propellant. Measurements are taken for both propellants at discharge voltages of 500 and 600 V. Electron temperatures and electric fields are also reported. The acceleration zone and equipotential lines are found to be strongly linked to the magnetic-field lines. The electrostatic plasma lens of the NASA-173Mv1 Hall thruster strongly focuses the xenon ions toward the center of the discharge channel, whereas the krypton ions are defocused. Krypton is also found to have a longer acceleration zone than the xenon cases. These results explain the large beam divergence observed with krypton operation. Krypton and xenon have similar maximum electron temperatures and similar lengths of the high electron temperature zone, although the high electron temperature zone is located farther downstream in the krypton case

Experimental halls workshop summary

International Nuclear Information System (INIS)

Thorndike, A.

1976-01-01

A brief discussion is given of: (1) pros and cons of open areas as compared with enclosed halls; (2) experimental hall needs of ep, anti p p, and other options; (3) hall for the lepton detector; and, (4) hall for the hadron spectrometer

Experimental halls workshop summary

International Nuclear Information System (INIS)

Thorndike, A.

1976-01-01

At the experimental halls workshop, discussions were held on: (1) open areas as compared with enclosed halls; (2) the needs of ep, anti pp, and other options; (3) the hall for the lepton detector; and (4) the hall for the hadron spectrometer. The value of different possibilities for the future experimental program was explored. A number of suggestions emerged which will be used as the design of the experimental halls progresses

On-chip microwave circulators using quantum Hall plasmonics

Science.gov (United States)

Mahoney, Alice; Colless, James; Pauka, Sebastian; Hornibrook, John; Doherty, Andrew; Reilly, David; Peeters, Lucas; Fox, Eli; Goldhaber-Gordon, David; Kou, Xuefeng; Pan, Lei; Wang, Kang; Watson, John; Gardner, Geoffrey; Manfra, Michael

Circulators are directional circuit elements integral to technologies including radar systems, microwave communication transceivers and the readout of quantum information devices. Their non-reciprocity commonly arises from the interference of microwaves over the centimetre-scale of the signal wavelength in the presence of bulky magnetic media that breaks time-reversal symmetry. We present a completely passive on-chip microwave circulator with size 1/1000th the wavelength by exploiting the chiral, `slow-light' response of a GaAs/AlGaAs 2-dimensional electron gas in the quantum Hall regime. Further, by implementing this circulator design on a thin film of a magnetic topological insulator (Cr0.12(Bi0.26Sb0.62)2Te3), we show that similar non-reciprocity can be achieved at zero magnetic field. This additional mode of operation serves as a non-invasive probe of edge states in the quantum anomalous Hall effect, while also extending the possibility for integration with superconducting devices.

Scanning Hall-probe microscopy system for two-dimensional imaging of critical current density in RE-123 coated conductors

International Nuclear Information System (INIS)

Higashikawa, K.; Inoue, M.; Kawaguchi, T.; Shiohara, K.; Imamura, K.; Kiss, T.; Iijima, Y.; Kakimoto, K.; Saitoh, T.; Izumi, T.

2011-01-01

Nondestructive characterization method of in-plane distribution of critical current density for coated conductors. Current distribution in a coated conductor compared with that from theoretical analysis. Relationship between local critical current density and local magnetic field. We have developed a characterization method for two-dimensional imaging of critical current density in coated conductors (CCs) based on scanning Hall-probe microscopy (SHPM). The distributions of the magnetic field around a sample were measured for several different conditions of external magnetic fields, and then were converted to those of the sheet current density which flowed to shield the external magnetic field or to trap the penetrated magnetic field. As a result, it was found that the amplitude of the sheet current density corresponded to that of critical current density almost in all the area of the sample except for the region where current direction changed. This indicates that we could obtain an in-plane distribution of the critical current density with a spatial resolution of around 100 μm in non-destructive manner by this method. We believe that this measurement will be a multifunctional and comprehensive characterization method for coated conductors.

In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

Science.gov (United States)

Polzin, Kurt; Korman, Valentin

2009-01-01

One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster s operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. There are many different sensors and techniques that have been employed to quantify discharge channel erosion in Hall thrusters. Snapshots of the wear pattern can be obtained at regular shutdown intervals using laser profilometry. Many non-intrusive techniques of varying complexity and sensitivity have been employed to detect the time-varying presence of erosion products in the thruster plume. These include the use quartz crystal microbalances, emission spectroscopy, laser induced flourescence, and cavity ring-down spectroscopy. While these techniques can provide a very accurate picture of the level of eroded material in the thruster plume, it is more difficult to use them to determine the location from which the material was eroded. Furthermore, none of the methods cited provide a true in-situ measure of erosion at the channel surface while

Complex scattering dynamics and the integer quantum Hall effect

International Nuclear Information System (INIS)

Trugman, S.A.; Waugh, F.R.

1987-01-01

The effect of a magnetic field on potential scattering is investigated microscopically. A magnetic field renders the scattering of a classical charged particle far more complex than previously suspected. Consequences include possible 1/f noise and an explanation of the observed breakdown of the quantum Hall effect at large currents. A particular scatterer is described by a discontinuous one dimensional Hamiltonian map, a class of maps that has not previously been studied. A renormalization group analysis indicates that singular behavior arises from the interplay of electron orbits that are periodic and orbits that are quasiperiodic

Performance of a Permanent-Magnet Cylindrical Hall-Effect Thruster

Science.gov (United States)

Polzin, K. A.; Sooby, E. S.; Kimberlin, A. C.; Raites, Y.; Merino, E.; Fisch, N. J.

2009-01-01

The performance of a low-power cylindrical Hall thruster, which more readily lends itself to miniaturization and low-power operation than a conventional (annular) Hall thruster, was measured using a planar plasma probe and a thrust stand. The field in the cylindrical thruster was produced using permanent magnets, promising a power reduction over previous cylindrical thruster iterations that employed electromagnets to generate the required magnetic field topology. Two sets of ring-shaped permanent magnets are used, and two different field configurations can be produced by reorienting the poles of one magnet relative to the other. A plasma probe measuring ion flux in the plume is used to estimate the current utilization for the two magnetic topologies. The measurements indicate that electron transport is impeded much more effectively in one configuration, implying higher thrust efficiency. Thruster performance measurements on this configuration were obtained over a power range of 70-350 W and with the cathode orifice located at three different axial positions relative to the thruster exit plane. The thrust levels over this power range were 1.25-6.5 mN, with anode efficiencies and specific impulses spanning 4-21% and 400-1950 s, respectively. The anode efficiency of the permanent-magnet thruster compares favorable with the efficiency of the electromagnet thruster when the power consumed by the electromagnets is taken into account.

Field effect in the quantum Hall regime of a high mobility graphene wire

Energy Technology Data Exchange (ETDEWEB)

Barraud, C., E-mail: cbarraud@phys.ethz.ch, E-mail: clement.barraud@univ-paris-diderot.fr; Choi, T.; Ihn, T.; Ensslin, K. [Solid State Physics Laboratory, ETH Zürich, CH-8093 Zürich (Switzerland); Butti, P.; Shorubalko, I. [Swiss Federal Laboratories of Materials Science and Technologies, EMPA Elect. Metrol. Reliabil. Lab., CH-8600 Dübendorf (Switzerland); Taniguchi, T.; Watanabe, K. [National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044 (Japan)

2014-08-21

In graphene-based electronic devices like in transistors, the field effect applied thanks to a gate electrode allows tuning the charge density in the graphene layer and passing continuously from the electron to the hole doped regime across the Dirac point. Homogeneous doping is crucial to understand electrical measurements and for the operation of future graphene-based electronic devices. However, recently theoretical and experimental studies highlighted the role of the electrostatic edge due to fringing electrostatic field lines at the graphene edges [P. Silvestrov and K. Efetov, Phys. Rev. B 77, 155436 (2008); F. T. Vasko and I. V. Zozoulenko, Appl. Phys. Lett. 97, 092115 (2010)]. This effect originates from the particular geometric design of the samples. A direct consequence is a charge accumulation at the graphene edges giving a value for the density, which deviates from the simple picture of a plate capacitor and also varies along the width of the graphene sample. Entering the quantum Hall regime would, in principle, allow probing this accumulation thanks to the extreme sensitivity of this quantum effect to charge density and the charge distribution. Moreover, the presence of an additional and counter-propagating edge channel has been predicted [P. Silvestrov and K. Efetov, Phys. Rev. B 77, 155436 (2008)] giving a fundamental aspect to this technological issue. In this article, we investigate this effect by tuning a high mobility graphene wire into the quantum Hall regime in which charge carriers probe the electrostatic potential at high magnetic field close to the edges. We observe a slight deviation to the linear shift of the quantum Hall plateaus with magnetic field and we study its evolution for different filling factors, which correspond to different probed regions in real space. We discuss the possible origins of this effect including an increase of the charge density towards the edges.

Dual-MWCNT Probe Thermal Sensor Assembly and Evaluation Based on Nanorobotic Manipulation inside a Field-Emission-Scanning Electron Microscope

Directory of Open Access Journals (Sweden)

Zhan Yang

2015-03-01

Full Text Available We report a thermal sensor composed of two multiwalled carbon nano-tubes (MWCNTs inside a field-emission-scanning electron microscope. The sensor was assembled using a nanorobotic manipulation system, which was used to construct a probe tip in order to detect the local environment of a single cell. An atomic force microscopy (AFM cantilever was used as a substrate; the cantilever was composed of Si3N4 and both sides were covered with a gold layer. MWCNTs were individually assembled on both sides of the AFM cantilever by employing nanorobotic manipulation. Another AFM cantilever was subsequently used as an end effector to manipulate the MWCNTs to touch each other. Electron-beam-induced deposition (EBID was then used to bond the two MWCNTs. The MWCNT probe thermal sensor was evaluated inside a thermostated container in the temperature range from 25°C to 60°C. The experimental results show the positive characteristics of the temperature coefficient of resistance (TCR.

Topological Hall and spin Hall effects in disordered skyrmionic textures

KAUST Repository

Ndiaye, Papa Birame; Akosa, Collins Ashu; Manchon, Aurelien

2017-01-01

We carry out a thorough study of the topological Hall and topological spin Hall effects in disordered skyrmionic systems: the dimensionless (spin) Hall angles are evaluated across the energy-band structure in the multiprobe Landauer-Büttiker formalism and their link to the effective magnetic field emerging from the real-space topology of the spin texture is highlighted. We discuss these results for an optimal skyrmion size and for various sizes of the sample and find that the adiabatic approximation still holds for large skyrmions as well as for nanoskyrmions. Finally, we test the robustness of the topological signals against disorder strength and show that the topological Hall effect is highly sensitive to momentum scattering.

Topological Hall and spin Hall effects in disordered skyrmionic textures

KAUST Repository

Ndiaye, Papa Birame

2017-02-24

We carry out a thorough study of the topological Hall and topological spin Hall effects in disordered skyrmionic systems: the dimensionless (spin) Hall angles are evaluated across the energy-band structure in the multiprobe Landauer-Büttiker formalism and their link to the effective magnetic field emerging from the real-space topology of the spin texture is highlighted. We discuss these results for an optimal skyrmion size and for various sizes of the sample and find that the adiabatic approximation still holds for large skyrmions as well as for nanoskyrmions. Finally, we test the robustness of the topological signals against disorder strength and show that the topological Hall effect is highly sensitive to momentum scattering.

Hall effect thruster with an AlN chamber

International Nuclear Information System (INIS)

Barral, S.; Jayet, Y.; Mazouffre, S.; Veron, E.; Echegut, P.; Dudeck, M.

2005-01-01

The plasma discharge of a Hall-effect thruster (SPT) is strongly depending of the plasma-insulated wall interactions. These interactions are mainly related to the energy deposition, potential sheath effect and electron secondary emission rate (e.s.e.). In usual SPT, the annular channel is made of BN-SiO 2 . The SPT100-ML (laboratory model will be tested with an AlN chamber in the French test facility Pivoine in the laboratoire d'Aerothermique (Orleans-France). The different parameters such as discharge current, thrust, plasma oscillations and wall temperature will studied for several operating conditions. The results will be compared with a fluid model developed in IPPT (Warsaw-Poland) taking into account electron emission from the internal and external walls and using previous experimental measurements of e.s.e. for AlN from ONERA (Toulouse-France). The surface state of AlN will be analysed before and after experiments by an Environmental Scanning Electron Microscope and by a Strength Electron Microscope. (author)

Evaluation of ion collection area in Faraday probes.

Science.gov (United States)

Brown, Daniel L; Gallimore, Alec D

2010-06-01

A Faraday probe with three concentric rings was designed and fabricated to assess the effect of gap width and collector diameter in a systematic study of the diagnostic ion collection area. The nested Faraday probe consisted of two concentric collector rings and an outer guard ring, which enabled simultaneous current density measurements on the inner and outer collectors. Two versions of the outer collector were fabricated to create gaps of 0.5 and 1.5 mm between the rings. Distribution of current density in the plume of a low-power Hall thruster ion source was measured in azimuthal sweeps at constant radius from 8 to 20 thruster diameters downstream of the exit plane with variation in facility background pressure. A new analytical technique is proposed to account for ions collected in the gap between the Faraday probe collector and guard ring. This method is shown to exhibit excellent agreement between all nested Faraday probe configurations, and to reduce the magnitude of integrated ion beam current to levels consistent with Hall thruster performance analyses. The technique is further studied by varying the guard ring bias potential with a fixed collector bias potential, thereby controlling ion collection in the gap. Results are in agreement with predictions based on the proposed analytical technique. The method is applied to a past study comparing the measured ion current density profiles of two Faraday probe designs. These findings provide new insight into the nature of ion collection in Faraday probe diagnostics, and lead to improved accuracy with a significant reduction in measurement uncertainty.

Evaluation of ion collection area in Faraday probes

International Nuclear Information System (INIS)

Brown, Daniel L.; Gallimore, Alec D.

2010-01-01

A Faraday probe with three concentric rings was designed and fabricated to assess the effect of gap width and collector diameter in a systematic study of the diagnostic ion collection area. The nested Faraday probe consisted of two concentric collector rings and an outer guard ring, which enabled simultaneous current density measurements on the inner and outer collectors. Two versions of the outer collector were fabricated to create gaps of 0.5 and 1.5 mm between the rings. Distribution of current density in the plume of a low-power Hall thruster ion source was measured in azimuthal sweeps at constant radius from 8 to 20 thruster diameters downstream of the exit plane with variation in facility background pressure. A new analytical technique is proposed to account for ions collected in the gap between the Faraday probe collector and guard ring. This method is shown to exhibit excellent agreement between all nested Faraday probe configurations, and to reduce the magnitude of integrated ion beam current to levels consistent with Hall thruster performance analyses. The technique is further studied by varying the guard ring bias potential with a fixed collector bias potential, thereby controlling ion collection in the gap. Results are in agreement with predictions based on the proposed analytical technique. The method is applied to a past study comparing the measured ion current density profiles of two Faraday probe designs. These findings provide new insight into the nature of ion collection in Faraday probe diagnostics, and lead to improved accuracy with a significant reduction in measurement uncertainty.

Development of Scanning Ultrafast Electron Microscope Capability.

Energy Technology Data Exchange (ETDEWEB)

Collins, Kimberlee Chiyoko [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Talin, Albert Alec [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Chandler, David W. [Sandia National Lab. (SNL-CA), Livermore, CA (United States); Michael, Joseph R. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

2016-11-01

Modern semiconductor devices rely on the transport of minority charge carriers. Direct examination of minority carrier lifetimes in real devices with nanometer-scale features requires a measurement method with simultaneously high spatial and temporal resolutions. Achieving nanometer spatial resolutions at sub-nanosecond temporal resolution is possible with pump-probe methods that utilize electrons as probes. Recently, a stroboscopic scanning electron microscope was developed at Caltech, and used to study carrier transport across a Si p-n junction [ 1 , 2 , 3 ] . In this report, we detail our development of a prototype scanning ultrafast electron microscope system at Sandia National Laboratories based on the original Caltech design. This effort represents Sandia's first exploration into ultrafast electron microscopy.

Mode transition of a Hall thruster discharge plasma

International Nuclear Information System (INIS)

Hara, Kentaro; Sekerak, Michael J.; Boyd, Iain D.; Gallimore, Alec D.

2014-01-01

A Hall thruster is a cross-field plasma device used for spacecraft propulsion. An important unresolved issue in the development of Hall thrusters concerns the effect of discharge oscillations in the range of 10–30 kHz on their performance. The use of a high speed Langmuir probe system and ultra-fast imaging of the discharge plasma of a Hall thruster suggests that the discharge oscillation mode, often called the breathing mode, is strongly correlated to an axial global ionization mode. Stabilization of the global oscillation mode is achieved as the magnetic field is increased and azimuthally rotating spokes are observed. A hybrid-direct kinetic simulation that takes into account the transport of electronically excited atoms is used to model the discharge plasma of a Hall thruster. The predicted mode transition agrees with experiments in terms of the mean discharge current, the amplitude of discharge current oscillation, and the breathing mode frequency. It is observed that the stabilization of the global oscillation mode is associated with reduced electron transport that suppresses the ionization process inside the channel. As the Joule heating balances the other loss terms including the effects of wall loss and inelastic collisions, the ionization oscillation is damped, and the discharge oscillation stabilizes. A wide range of the stable operation is supported by the formation of a space charge saturated sheath that stabilizes the electron axial drift and balances the Joule heating as the magnetic field increases. Finally, it is indicated from the numerical results that there is a strong correlation between the emitted light intensity and the discharge current.

Hall effect in hopping regime

International Nuclear Information System (INIS)

Avdonin, A.; Skupiński, P.; Grasza, K.

2016-01-01

A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.

Hall effect in hopping regime

Energy Technology Data Exchange (ETDEWEB)

Avdonin, A., E-mail: avdonin@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Skupiński, P. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Grasza, K. [Institute of Physics, Polish Academy of Sciences, Al. Lotników 32/46, 02-668 Warszawa (Poland); Institute of Electronic Materials Technology, ul. Wólczyńska 133, 01-919 Warszawa (Poland)

2016-02-15

A simple description of the Hall effect in the hopping regime of conductivity in semiconductors is presented. Expressions for the Hall coefficient and Hall mobility are derived by considering averaged equilibrium electron transport in a single triangle of localization sites in a magnetic field. Dependence of the Hall coefficient is analyzed in a wide range of temperature and magnetic field values. Our theoretical result is applied to our experimental data on temperature dependence of Hall effect and Hall mobility in ZnO. - Highlights: • Expressions for Hall coefficient and mobility for hopping conductivity are derived. • Theoretical result is compared with experimental curves measured on ZnO. • Simultaneous action of free and hopping conduction channels is considered. • Non-linearity of hopping Hall coefficient is predicted.

Sparse sampling and reconstruction for electron and scanning probe microscope imaging

Science.gov (United States)

Anderson, Hyrum; Helms, Jovana; Wheeler, Jason W.; Larson, Kurt W.; Rohrer, Brandon R.

2015-07-28

Systems and methods for conducting electron or scanning probe microscopy are provided herein. In a general embodiment, the systems and methods for conducting electron or scanning probe microscopy with an undersampled data set include: driving an electron beam or probe to scan across a sample and visit a subset of pixel locations of the sample that are randomly or pseudo-randomly designated; determining actual pixel locations on the sample that are visited by the electron beam or probe; and processing data collected by detectors from the visits of the electron beam or probe at the actual pixel locations and recovering a reconstructed image of the sample.

Anomalous Hall effect in semiconductor quantum wells in proximity to chiral p -wave superconductors

Science.gov (United States)

Yang, F.; Yu, T.; Wu, M. W.

2018-05-01

By using the gauge-invariant optical Bloch equation, we perform a microscopic kinetic investigation on the anomalous Hall effect in chiral p -wave superconducting states. Specifically, the intrinsic anomalous Hall conductivity in the absence of the magnetic field is zero as a consequence of Galilean invariance in our description. As for the extrinsic channel, a finite anomalous Hall current is obtained from the impurity scattering with the optically excited normal quasiparticle current even at zero temperature. From our kinetic description, it can be clearly seen that the excited normal quasiparticle current is due to an induced center-of-mass momentum of Cooper pairs through the acceleration driven by ac electric field. For the induced anomalous Hall current, we show that the conventional skew-scattering channel in the linear response makes the dominant contribution in the strong impurity interaction. In this case, our kinetic description as a supplementary viewpoint mostly confirms the results of Kubo formalism in the literature. Nevertheless, in the weak impurity interaction, this skew-scattering channel becomes marginal and we reveal that an induction channel from the Born contribution dominates the anomalous Hall current. This channel, which has long been overlooked in the literature, is due to the particle-hole asymmetry by nonlinear optical excitation. Finally, we study the case in the chiral p -wave superconducting state with a transverse conical magnetization, which breaks the Galilean invariance. In this situation, the intrinsic anomalous Hall conductivity is no longer zero. Comparison of this intrinsic channel with the extrinsic one from impurity scattering is addressed.

Real-space and reciprocal-space Berry phases in the Hall effect of Mn(1-x)Fe(x)Si.

Science.gov (United States)

Franz, C; Freimuth, F; Bauer, A; Ritz, R; Schnarr, C; Duvinage, C; Adams, T; Blügel, S; Rosch, A; Mokrousov, Y; Pfleiderer, C

2014-05-09

We report an experimental and computational study of the Hall effect in Mn(1-x)Fe(x)Si, as complemented by measurements in Mn(1-x)Co(x)Si, when helimagnetic order is suppressed under substitutional doping. For small x the anomalous Hall effect (AHE) and the topological Hall effect (THE) change sign. Under larger doping the AHE remains small and consistent with the magnetization, while the THE grows by over a factor of 10. Both the sign and the magnitude of the AHE and the THE are in excellent agreement with calculations based on density functional theory. Our study provides the long-sought material-specific microscopic justification that, while the AHE is due to the reciprocal-space Berry curvature, the THE originates in real-space Berry phases.

Designs for a quantum electron microscope.

Science.gov (United States)

Kruit, P; Hobbs, R G; Kim, C-S; Yang, Y; Manfrinato, V R; Hammer, J; Thomas, S; Weber, P; Klopfer, B; Kohstall, C; Juffmann, T; Kasevich, M A; Hommelhoff, P; Berggren, K K

2016-05-01

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This 'quantum weirdness' could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or "quantum electron microscope". A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Contribution of the study of the Hall Effect. Hall Effect of powder products

International Nuclear Information System (INIS)

Cherville, Jean

1961-01-01

This research thesis reports the development of an apparatus aimed at measuring the Hall Effect and the magneto-resistance of powders at room temperature and at the liquid nitrogen temperature. The author also proposes a theoretical contribution to the Hall Effect and reports the calculation of conditions to be met to obtain a correct value for the Hall constant. Results are experimentally verified. The method is then applied to the study of a set of powdered pre-graphitic graphites. The author shows that their Hall coefficient confirms the model already proposed by Mrozowski. The study of the Hall Effect of any kind of powders can thus be performed, and the Hall Effect can therefore be a mean to study mineral and organic compounds, and notably powdered biological molecules [fr

Cryogenic microsize Hall sensors

International Nuclear Information System (INIS)

Kvitkovic, J.; Polak, M.

1993-01-01

Hall sensors have a variety of applications in magnetic field measurements. The active area of the Hall sensor does not play an important role in measuring of homogeneous magnetic field. Actually Hall sensors are widely used to measure profiles of magnetic fields produced by magnetization currents in samples of HTC superconductors, as well as of LTC ones. Similar techniques are used to measure magnetization of both HTC and LTC superconductors. In these cases Hall sensor operates in highly inhomogeneous magnetic fields. Because of that, Hall sensors with very small active area are required. We developed and tested Hall sensors with active area 100 μm x 100 μm - type M and 50 μm x 50 μm - type V. Here we report on the most imporant parameters of these units, as well as on their properties as differential magnetometer. (orig.)

Topological Hall and Spin Hall Effects in Disordered Skyrmionic Textures

OpenAIRE

N'diaye, P. B.; Akosa, C. A.; Manchon, A.

2016-01-01

We carry out a throughout study of the topological Hall and topological spin Hall effects in disordered skyrmionic systems: the dimensionless (spin) Hall angles are evaluated across the energy band structure in the multiprobe Landauer-B\\"uttiker formalism and their link to the effective magnetic field emerging from the real space topology of the spin texture is highlighted. We discuss these results for an optimal skyrmion size and for various sizes of the sample and found that the adiabatic a...

Ultrafast supercontinuum fiber-laser based pump-probe scanning magneto-optical Kerr effect microscope for the investigation of electron spin dynamics in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution.

Science.gov (United States)

Henn, T; Kiessling, T; Ossau, W; Molenkamp, L W; Biermann, K; Santos, P V

2013-12-01

We describe a two-color pump-probe scanning magneto-optical Kerr effect microscope which we have developed to investigate electron spin phenomena in semiconductors at cryogenic temperatures with picosecond time and micrometer spatial resolution. The key innovation of our microscope is the usage of an ultrafast "white light" supercontinuum fiber-laser source which provides access to the whole visible and near-infrared spectral range. Our Kerr microscope allows for the independent selection of the excitation and detection energy while avoiding the necessity to synchronize the pulse trains of two separate picosecond laser systems. The ability to independently tune the pump and probe wavelength enables the investigation of the influence of excitation energy on the optically induced electron spin dynamics in semiconductors. We demonstrate picosecond real-space imaging of the diffusive expansion of optically excited electron spin packets in a (110) GaAs quantum well sample to illustrate the capabilities of the instrument.

Tuning giant anomalous Hall resistance ratio in perpendicular Hall balance

Energy Technology Data Exchange (ETDEWEB)

Zhang, J. Y.; Yang, G. [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China); State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, S. G., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Liu, J. L. [State Key Laboratory of Magnetism, Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Wang, R. M. [Department of Physics, Beijing University of Aeronautics and Astronautics, Beijing 100191 (China); Amsellem, E.; Kohn, A. [Department of Materials Engineering, Ilse Katz Institute for Nanoscale Science and Technology, Ben-Gurion University of the Negev, Beer-Sheva 84105 (Israel); Yu, G. H., E-mail: sgwang@iphy.ac.cn, E-mail: ghyu@mater.ustb.edu.cn [Department of Materials Physics and Chemistry, University of Science and Technology Beijing, Beijing 100083 (China)

2015-04-13

Anomalous Hall effect at room temperature in perpendicular Hall balance with a core structure of [Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4} has been tuned by functional CoO layers, where [Pt/Co]{sub 4} multilayers exhibit perpendicular magnetic anisotropy. A giant Hall resistance ratio up to 69 900% and saturation Hall resistance (R{sub S}{sup P}) up to 2590 mΩ were obtained in CoO/[Pt/Co]{sub 4}/NiO/[Co/Pt]{sub 4}/CoO system, which is 302% and 146% larger than that in the structure without CoO layers, respectively. Transmission electron microscopy shows highly textured [Co/Pt]{sub 4} multilayers and oxide layers with local epitaxial relations, indicating that the crystallographic structure has significant influence on spin dependent transport properties.

The infrared Hall effect in YBCO: Temperature and frequency dependence of Hall scattering

International Nuclear Information System (INIS)

Grayson, M.; Cerne, J.; Drew, H.D.; Schmadel, D.C.; Hughes, R.; Preston, J.S.; Kung, P.J.; Vale, L.

1999-01-01

The authors measure the Hall angle, θ H , in YBCO films in the far- and mid-infrared to determine the temperature and frequency dependence of the Hall scattering. Using novel modulation techniques they measure both the Faraday rotation and ellipticity induced by these films in high magnetic fields to deduce the complex conductivity tensor. They observe a strong temperature dependence of the mid-infrared Hall conductivity in sharp contrast to the weak dependence of the longitudinal conductivity. By fitting the frequency dependent normal state Hall angle to a Lorentzian θ H (ω) = ω H /(γ H minus iω) they find the Hall frequency, ω H , is nearly independent of temperature. The Hall scattering rate, γ H , is consistent with γ H ∼ T 2 up to 200 K and is remarkably independent of IR frequency suggesting non-Fermi liquid behavior

The fluctuation Hall conductivity and the Hall angle in type-II superconductor under magnetic field

Energy Technology Data Exchange (ETDEWEB)

Tinh, Bui Duc, E-mail: tinhbd@hnue.edu.vn [Institute of Research and Development, Duy Tan University, K7/25 Quang Trung, Danang (Viet Nam); Department of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam); Hoc, Nguyen Quang; Thu, Le Minh [Department of Physics, Hanoi National University of Education, 136 Xuan Thuy, Cau Giay, Hanoi (Viet Nam)

2016-02-15

Highlights: • The time-dependent Ginzburg–Landau was used to calculate fluctuation Hall conductivity and Hall angle in type-II superconductor in 2D and 3D. • We obtain analytical expressions for the fluctuation Hall conductivity and the Hall angle summing all Landau levels without need to cutoff higher Landau levels to treat arbitrary magnetic field. • The results were compared to the experimental data on YBCO. - Abstract: The fluctuation Hall conductivity and the Hall angle, describing the Hall effect, are calculated for arbitrary value of the imaginary part of the relaxation time in the frame of the time-dependent Ginzburg–Landau theory in type II-superconductor with thermal noise describing strong thermal fluctuations. The self-consistent Gaussian approximation is used to treat the nonlinear interaction term in dynamics. We obtain analytical expressions for the fluctuation Hall conductivity and the Hall angle summing all Landau levels without need to cutoff higher Landau levels to treat arbitrary magnetic field. The results are compared with experimental data on high-T{sub c} superconductor.

Study by Hall probe mapping of the trapped flux modification produced by local heating in YBCO HTS bulks for different surface/volume ratios

International Nuclear Information System (INIS)

Laurent, Ph; Mathieu, J-P; Mattivi, B; Fagnard, J-F; Meslin, S; Noudem, J G; Ausloos, M; Cloots, R; Vanderbemden, Ph

2005-01-01

The aim of this report is to compare the trapped field distribution under a local heating created at the sample edge for different sample morphologies. Hall probe mappings of the magnetic induction trapped in YBCO bulk samples maintained out of thermal equilibrium were performed on YBCO bulk single domains, YBCO single domains with regularly spaced hole arrays, and YBCO superconducting foams. The capability of heat draining was quantified by two criteria: the average induction decay and the size of the thermally affected zone caused by a local heating of the sample. Among the three investigated sample shapes, the drilled single domain displays a trapped induction which is weakly affected by the local heating while displaying a high trapped field. Finally, a simple numerical modelling of the heat flux spreading into a drilled sample is used to suggest some design rules about the hole configuration and their size

Atom probe field ion microscope study of the range and diffusivity of helium in tungsten

International Nuclear Information System (INIS)

Wagner, A.

1978-08-01

A time-of-flight (TOF) atom-probe field-ion microscope (FIM) specifically designed for the study of defects in metals is described. With this automated system 600 TOF min -1 can be recorded and analyzed. Performance tests of the instrument demonstrated that (1) the seven isotopes of molybdenum and the five isotopes of tungsten can be clearly resolved; and (2) the concentration and spatial distribution of all constitutents present at levels greater than 0.05 at. % in a W--25 at. % Re, Mo--1.0 at. % Ti, Mo--1.0 at. % Ti--0.08 at. % Zr (TZM), a low swelling stainless steel (LS1A) and a metallic glass (Metglas 2826) can be measured. The effect of the rate of field evaporation on the quantitative atom probe analysis of a Mo--1.0 at. % Ti alloy and a Mo--1.0 at. % Ti--0.08 at. % Zr alloy was investigated. As the field evaporation rate increased the measured Ti concentration was found to also increase. A simple qualitative model was proposed to explain the observation. The spatial distribution of titanium in a fast neutron irradiated Mo--1.0 at. % Ti alloy has been investigated. No evidence of Ti segregation to the voids was detected nor has any evidence of significant resolution of Ti from the TiC precipitates been detected. A small amount of segregation of carbon to a void was detected

Measurement of erosion rate by absorption spectroscopy in a Hall thruster

International Nuclear Information System (INIS)

Yamamoto, Naoji; Yokota, Shigeru; Matsui, Makoto; Komurasaki, Kimiya; Arakawa, Yoshihiro

2005-01-01

The erosion rate of a Hall thruster was estimated with the objective of building a real-time erosion rate monitoring system using a 1 kW class anode layer type Hall thruster. This system aids the understanding of the tradeoff between lifetime and performance. To estimate the flux of the sputtered wall material, the number density of the sputtered iron was measured by laser absorption spectroscopy using an absorption line from ground atomic iron at 371.9935 nm. An ultravioletAl x In y Ga (1-x-y) N diode laser was used as the probe. The estimated number density of iron was 1.1x10 16 m -3 , which is reasonable when compared with that measured by duration erosion tests. The relation between estimated erosion rate and magnetic flux density also agreed with that measured by duration erosion tests

Microscope-controlled glass bead blasting: a new technique

Directory of Open Access Journals (Sweden)

Peter Kotschy

2011-01-01

Full Text Available Peter Kotschy1, Sascha Virnik2, Doris Christ3, Alexander Gaggl21Private Practice, Vienna, Austria; 2Department of Oral and Maxillofacial Surgery, Central Hospital, Klagenfurt, Austria; 3Klagenfurt, AustriaObjective: The aim of periodontal therapy is the healing of periodontal inflammation; the protection of the attachment and the alveolar bone; and the regeneration of the periodontal structures. In the therapy of periodontitis, supra- and subgingival scaling and root planing plays a main role. The procedure described combines perfect root cleaning without scaling and root planing and minimal invasive periodontal surgery without a scalpel.Material and methods: Glass beads of 90 µm were used with the kinetic preparation unit PrepStart® under a pressure of 0.5–5 bar. This technique was practised only under visual control using the OPMI® PRO Magis microscope. Seven examinations were carried out at baseline after 3, 6, 12, 18, 24, and 36 months.Results: Time shows a statistically significant influence on all of the considered target variables (P < 0.0001 for all. As the according estimate is negative, probing depth decreases over time. The major decrease seems to be during the first 6 months. Considering probing depth, plaque on the main effect root shows significant influence (again, P < 0.0001 for all. Observations with high probing depth at the beginning were faster than those with low probing depth. The same characteristic appears by attachment level. Patients with more loss of attachment show more gain.Conclusions: Using microscope-controlled glass bead blasting results in a perfectly clean root surface using visual control (magnification 20×. Microscope-controlled glass bead blasting is therefore a good alternative to periodontal surgery.Keywords: periodontal therapy, microscope, periodontitis

Skyrmions and Hall viscosity

Science.gov (United States)

Kim, Bom Soo

2018-05-01

We discuss the contribution of magnetic Skyrmions to the Hall viscosity and propose a simple way to identify it in experiments. The topological Skyrmion charge density has a distinct signature in the electric Hall conductivity that is identified in existing experimental data. In an electrically neutral system, the Skyrmion charge density is directly related to the thermal Hall conductivity. These results are direct consequences of the field theory Ward identities, which relate various physical quantities based on symmetries and have been previously applied to quantum Hall systems.

Development of a Micro-SPM (Scanning Probe Microscope by Post-Assembly of a MEMS-Stage and an Independent Cantilever

Directory of Open Access Journals (Sweden)

Zhi Li

2007-08-01

Full Text Available The development of miniature scanning probe microscopes (SPM on the basis of the MEMS technique has gained more and more interest. Here a novel approach is presented to realize a micro-SPM, in which by means of post-assembly a conventional cantilever is mounted onto a MEMS positioning stage and used to detect the topography variation of the surface under test. Compared with other integrated micro-SPMs, the proposed micro-SPM can maintain the lateral resolution by simply renewing its cantilever in use, and therefore features low cost, practicability and longer lifetime. Preliminary experimental results are reported, which demonstrate that the proposed microSPM can be realized.

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

Science.gov (United States)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

Energy Technology Data Exchange (ETDEWEB)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris, E-mail: hammel@physics.osu.edu [Department of Physics, The Ohio State University, Columbus, Ohio 43210 (United States)

2015-05-07

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

Science.gov (United States)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-05-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems.

Microscopic studies of nonlocal spin dynamics and spin transport (invited)

International Nuclear Information System (INIS)

Adur, Rohan; Du, Chunhui; Cardellino, Jeremy; Scozzaro, Nicolas; Wolfe, Christopher S.; Wang, Hailong; Herman, Michael; Bhallamudi, Vidya P.; Pelekhov, Denis V.; Yang, Fengyuan; Hammel, P. Chris

2015-01-01

Understanding the behavior of spins coupling across interfaces in the study of spin current generation and transport is a fundamental challenge that is important for spintronics applications. The transfer of spin angular momentum from a ferromagnet into an adjacent normal material as a consequence of the precession of the magnetization of the ferromagnet is a process known as spin pumping. We find that, in certain circumstances, the insertion of an intervening normal metal can enhance spin pumping between an excited ferromagnetic magnetization and a normal metal layer as a consequence of improved spin conductance matching. We have studied this using inverse spin Hall effect and enhanced damping measurements. Scanned probe magnetic resonance techniques are a complementary tool in this context offering high resolution magnetic resonance imaging, localized spin excitation, and direct measurement of spin lifetimes or damping. Localized magnetic resonance studies of size-dependent spin dynamics in the absence of lithographic confinement in both ferromagnets and paramagnets reveal the close relationship between spin transport and spin lifetime at microscopic length scales. Finally, detection of ferromagnetic resonance of a ferromagnetic film using the photoluminescence of nitrogen vacancy spins in neighboring nanodiamonds demonstrates long-range spin transport between insulating materials, indicating the complexity and generality of spin transport in diverse, spatially separated, material systems

Energy consumption of sport halls

Energy Technology Data Exchange (ETDEWEB)

1983-01-01

The energy consumption of Finland's sports halls (ball games halls, ice hockey halls and swimming halls) represent approximately 1% of that of the country's whole building stock. In the light of the facts revealed by the energy study the potential energy saving rate in sports halls is 15-25%. The total savings would be something like FIM 30-40 million per annum, of which about a half would be achieved without energy-economic investments only by changing utilization habits and by automatic control measures. The energy-economic investments are for the most part connected with ventilation and their repayment period is from one to five years. On the basis of the energy study the following specific consumption are presented as target values: swimming halls: heat (kWh/m*H3/a)100, electricity (kWh/m*H3/a)35, water (l/m*H3/a)1000 icehockey halls (warm): heat (kWh/m*H3/a)25, electricity (kWh/m*H3/a)15, water (l/m*H3/a)200, ball games halls (multi-purpose halls): heat (kWh/m*H3/a)30, electricity (kWh/m*H3/a)25, water (l/m*H3/a)130. In the study the following points proved to be the central areas of energy saving in sports halls: 1. Flexible regulation of the temperature in sports spaces on the basis of the sport in question. 2. The ventilation of swimming halls should be adjusted in such a way that the humidity of the hall air would comply with the limit humidity curve determined by the quality of structures and the temperature of the outdoor air. 3. An ice skating hall is an establishment producing condensing energy from 8 to 9 months a year worth of approx. 100.000-150.000 Finnmarks. The development of the recovery of condensing energy has become more important. 4. The ventilation of ball games halls may account for over 50% of the energy consumption of the whole building. Therefore special attention should be paid to the optimatization of ventilation as a whole.

Optical probing of quantum Hall effect of composite fermions and of the liquid-insulator transition

International Nuclear Information System (INIS)

Rossella, F; Bellani, V; Dionigi, F; Amado, M; Diez, E; Kowalik, K; Biasiol, G; Sorba, L

2011-01-01

In the photoluminescence spectra of a two-dimensional electron gas in the fractional quantum Hall regime we observe the states at filling factors ν = 4/5, 5/7, 4/11 and 3/8 as clear minima in the intensity or area emission peak. The first three states are described as interacting composite fermions in fractional quantum Hall regime. The minimum in the intensity at ν 3/8, which is not explained within this picture, can be an evidence of a suppression of the screening of the Coulomb interaction among the effective quasi-particles involved in this intriguing state. The magnetic field energy dispersion at very low temperatures is also discussed. At low field the emission follows a Landau dispersion with a screened magneto-Coulomb contribution. At intermediate fields the hidden symmetry manifests. At high field above ν = 1/3 the electrons correlate into an insulating phase, and the optical emission behaviour at the liquid-insulator transition is coherent with a charge ordering driven by Coulomb correlations.

Quasiparticle-mediated spin Hall effect in a superconductor.

Science.gov (United States)

Wakamura, T; Akaike, H; Omori, Y; Niimi, Y; Takahashi, S; Fujimaki, A; Maekawa, S; Otani, Y

2015-07-01

In some materials the competition between superconductivity and magnetism brings about a variety of unique phenomena such as the coexistence of superconductivity and magnetism in heavy-fermion superconductors or spin-triplet supercurrent in ferromagnetic Josephson junctions. Recent observations of spin-charge separation in a lateral spin valve with a superconductor evidence that these remarkable properties are applicable to spintronics, although there are still few works exploring this possibility. Here, we report the experimental observation of the quasiparticle-mediated spin Hall effect in a superconductor, NbN. This compound exhibits the inverse spin Hall (ISH) effect even below the superconducting transition temperature. Surprisingly, the ISH signal increases by more than 2,000 times compared with that in the normal state with a decrease of the injected spin current. The effect disappears when the distance between the voltage probes becomes larger than the charge imbalance length, corroborating that the huge ISH signals measured are mediated by quasiparticles.

Electromagnetic microscope compared with a conventional pulsed eddy-current probe

Science.gov (United States)

Podney, Walter N.

1998-03-01

A superconductive probe presently can detect a crack at a rivet hole that is two to three times smaller than the smallest crack detectable by a conventional probe. As the technology matures and noise resolution approaches a limit set by SQUIDS, approximately 1 fH, it will enable detecting submillimeter cracks down to approximately 15 mm.

Experimental probes of emergent symmetries in the quantum Hall system

CERN Document Server

Lutken, C A

2011-01-01

Experiments studying renormalization group flows in the quantum Hall system provide significant evidence for the existence of an emergent holomorphic modular symmetry Gamma(0)(2). We briefly review this evidence and show that, for the lowest temperatures, the experimental determination of the position of the quantum critical points agrees to the parts per mille level with the prediction from Gamma(0)(2). We present evidence that experiments giving results that deviate substantially from the symmetry predictions are not cold enough to be in the quantum critical domain. We show how the modular symmetry extended by a non-holomorphic particle hole duality leads to an extensive web of dualities related to those in plateau insulator transitions, and we derive a formula relating dual pairs (B, B(d)) of magnetic field strengths across any transition. The experimental data obtained for the transition studied so far is in excellent agreement with the duality relations following from this emergent symmetry, and rule out...

Use of oligodeoxynucleotide signature probes for identification of physiological groups of methylotrophic bacteria

International Nuclear Information System (INIS)

Tsien, H.C.; Bratina, B.J.; Tsuji, K.; Hanson, R.S.

1990-01-01

Oligodeoxynucleotide sequences that uniquely complemented 16S rRNAs of each group of methylotrophs were synthesized and used as hybridization probes for the identification of methylotrophic bacteria possessing the serine and ribulose monophosphate (RuMP) pathways for formaldehyde fixation. The specificity of the probes was determined by hybridizing radiolabeled probes with slot-blotted RNAs of methylotrophs and other eubacteria followed by autoradiography. The washing temperature was determined experimentally to be 50 and 52 degrees C for 9-α (serine pathway) and 10-γ (RuMP pathway) probes, respectively. RNAs isolated from serine pathway methylotrophs bound to probe 9-α, and RNAs from RuMP pathway methylotrophs bound to probe 10-γ. Nonmethylotrophic eubacterial RNAs did not bind to either probe. The probes were also labeled with fluorescent dyes. Cells fixed to microscope slides were hybridized with these probes, washed, and examined in a fluorescence microscope equipped with appropriate filter sets. Cells of methylotrophic bacteria possessing the serine or RuMP pathway specifically bind probes designed for each group. Samples with a mixture of cells of type I and II methanotrophs were detected and differentiated with single probes or mixed probes labeled with different fluorescent dyes, which enabled the detection of both types of cells in the same microscopic field

Local work function analysis of Pt/TiO2 photocatalyst by a Kelvin probe force microscope

International Nuclear Information System (INIS)

Hiehata, K; Sasahara, A; Onishi, H

2007-01-01

Nanometre-sized Pt clusters were prepared on a TiO 2 (110)-(1 x 1) surface, and the lateral distribution of work function was examined by using a Kelvin probe force microscope. Local work function on the Pt clusters was smaller than that on the surrounding TiO 2 surface. Assuming that the dipole moments which perturb the work function are produced by uneven electron distribution, the decrease of the work function indicates electron transfer from the clusters to the TiO 2 surface. After decomposition of pivalate anions on the surfaces by UV irradiation, the work function increased on some Pt clusters. It is known that holes photoexcited in TiO 2 attach to pivalate anions to cause a decomposition reaction. Hence the increase of the observed work function by UV irradiation can be ascribed to the trapping of the accompanying electrons to the Pt clusters

In situ electrical probing and bias-mediated manipulation of dielectric nanotubes in a high-resolution transmission electron microscope

International Nuclear Information System (INIS)

Golberg, D.; Mitome, M.; Kurashima, K.; Zhi, C.Y.; Tang, C.C.; Bando, Y.; Lourie, O.

2006-01-01

Boron nitride nanotubes filled with magnesium oxides [MgO, MgO 2 ] and/or hydroxide [Mg(OH) 2 ] are electrically probed and delicately manipulated inside a 300 kV JEOL-3000F high-resolution transmission analytical electron microscope equipped with a side-entry 'Nanofactory Instruments' piezoholder. At a low bias the nanotubes demonstrate truly insulating behavior. At a high bias of ±30 V they show reversible breakdown current of several dozens of nA. Under 300 kV electron beam irradiation the nanotubes are positively charged that allows us to perform on-demand manipulation with them through tuning of polarity and/or value of a bias voltage on a gold counterelectrode from -140 to +140 V, owing to the prominent electrostatic nanotube-electrode interactions

Probing chirality with a femtosecond reaction microscope

Directory of Open Access Journals (Sweden)

Janssen M. H. M.

2013-03-01

Full Text Available Detection of molecular chirality with high sensitivity and selectivity is important for many analytical and practical applications. Photoionization has emerged as a very sensitive probe of chirality in molecules. We show here that a table top setup with a femtosecond laser and a single imaging detector for both photoelectrons and photoions enables detection of chirality up to 3 orders of magnitude better than the existing conventional absorption based techniques.

Scanning optical microscope with long working distance objective

Science.gov (United States)

Cloutier, Sylvain G.

2010-10-19

A scanning optical microscope, including: a light source to generate a beam of probe light; collimation optics to substantially collimate the probe beam; a probe-result beamsplitter; a long working-distance, infinity-corrected objective; scanning means to scan a beam spot of the focused probe beam on or within a sample; relay optics; and a detector. The collimation optics are disposed in the probe beam. The probe-result beamsplitter is arranged in the optical paths of the probe beam and the resultant light from the sample. The beamsplitter reflects the probe beam into the objective and transmits resultant light. The long working-distance, infinity-corrected objective is also arranged in the optical paths of the probe beam and the resultant light. It focuses the reflected probe beam onto the sample, and collects and substantially collimates the resultant light. The relay optics are arranged to relay the transmitted resultant light from the beamsplitter to the detector.

Gate-controlled tunneling of quantum Hall edge states in bilayer graphene

Science.gov (United States)

Zhu, Jun; Li, Jing; Wen, Hua

Controlled tunneling of integer and fractional quantum Hall edge states provides a powerful tool to probe the physics of 1D systems and exotic particle statistics. Experiments in GaAs 2DEGs employ either a quantum point contact or a line junction tunnel barrier. It is generally difficult to independently control the filling factors νL and νR on the two sides of the barrier. Here we show that in bilayer graphene both νL and νR as well as their Landau level structures can be independently controlled using a dual-split-gate structure. In addition, the height of the line-junction tunnel barrier implemented in our experiments is tunable via a 5th gate. By measuring the tunneling resistance across the junction RT we examine the equilibration of the edge states in a variety of νL/νR scenarios and under different barrier heights. Edge states from both sides are fully mixed in the case of a low barrier. As the barrier height increases, we observe plateaus in RT that correspond to sequential complete backscattering of edge states. Gate-controlled manipulation of edge states offers a new angle to the exploration of quantum Hall magnetism and fractional quantum Hall effect in bilayer graphene.

PC-based digital feedback control for scanning force microscope

International Nuclear Information System (INIS)

Mohd Ashhar Khalid

2002-01-01

In the past, most digital feedback implementation for scanned-probe microscope were based on a digital signal processor (DSP). At present DSP plug-in card with the input-output interface module is still expensive compared to a fast pentium PC motherboard. For a magnetic force microscope (MFM) digital feedback has an advantage where the magnetic signal can be easily separated from the topographic signal. In this paper, a simple low-cost PC-based digital feedback and imaging system for Scanning Force Microscope (SFM) is presented. (Author)

Atom-probe field-ion microscope for the study of the interaction of impurity atoms or alloying elements with defects

International Nuclear Information System (INIS)

Wagner, A.; Hall, T.M.; Seidman, D.N.

1976-10-01

A time-of-flight (TOF) atom-probe field-ion microscope (FIM) designed for the study of defects is described. This atom probe features: (1) a variable magnification internal-image-intensification system; (2) a liquid-helium goniometer stage; (3) a low-energy (less than or equal 3 keV) gas-ion gun for in-situ irradiations; (4) an ultra-high vacuum (approximately 3.10 -10 torr) chamber; (5) a high vacuum (approximately 10 -6 torr) specimen-exchange device; (6) a Chevron ion detector; and (7) an eight-channel digital timer with a +-10 nsec resolution for measuring the TOFs. The entire process of applying the evaporation pulse to the specimen, measuring the voltages, and analyzing the TOF data is controlled by a computer. With this system we can record and analyze 600 TOFmin. Results on unirradiated specimens of molybdenum, tungsten, W/25 at. % Re, Mo/1.0 at. % Ti, Mo/1.0 at. % Ti/0.08 at. % Zr and a special low swelling stainless steel alloy (LS1A) demonstrate the instrument's ability to quantitatively determine concentrations at the 5.10 -4 at fr level and to determine their spatial distribution with a resolution of a few angstroms

SO(8) fermion dynamical symmetry and strongly correlated quantum Hall states in monolayer graphene

Science.gov (United States)

Wu, Lian-Ao; Murphy, Matthew; Guidry, Mike

2017-03-01

A formalism is presented for treating strongly correlated graphene quantum Hall states in terms of an SO(8) fermion dynamical symmetry that includes pairing as well as particle-hole generators. The graphene SO(8) algebra is isomorphic to an SO(8) algebra that has found broad application in nuclear physics, albeit with physically very different generators, and exhibits a strong formal similarity to SU(4) symmetries that have been proposed to describe high-temperature superconductors. The well-known SU(4) symmetry of quantum Hall ferromagnetism for single-layer graphene is recovered as one subgroup of SO(8), but the dynamical symmetry structure associated with the full set of SO(8) subgroup chains extends quantum Hall ferromagnetism and allows analytical many-body solutions for a rich set of collective states exhibiting spontaneously broken symmetry that may be important for the low-energy physics of graphene in strong magnetic fields. The SO(8) symmetry permits a natural definition of generalized coherent states that correspond to symmetry-constrained Hartree-Fock-Bogoliubov solutions, or equivalently a microscopically derived Ginzburg-Landau formalism, exhibiting the interplay between competing spontaneously broken symmetries in determining the ground state.

Power Dependence of the Electron Mobility Profile in a Hall Thruster

Science.gov (United States)

Jorns, Benjamin A.; Hofery, Richard H.; Mikellides, Ioannis G.

2014-01-01

The electron mobility profile is estimated in a 4.5 kW commercial Hall thruster as a function of discharge power. Internal measurements of plasma potential and electron temperature are made in the thruster channel with a high-speed translating probe. These measurements are presented for a range of throttling conditions from 150 - 400 V and 0.6 - 4.5 kW. The fluid-based solver, Hall2De, is used in conjunction with these internal plasma parameters to estimate the anomalous collision frequency profile at fixed voltage, 300 V, and three power levels. It is found that the anomalous collision frequency profile does not change significantly upstream of the location of the magnetic field peak but that the extent and magnitude of the anomalous collision frequency downstream of the magnetic peak does change with thruster power. These results are discussed in the context of developing phenomenological models for how the collision frequency profile depends on thruster operating conditions.

Exotic Non-Abelian Topological Defects in Lattice Fractional Quantum Hall States

Science.gov (United States)

Liu, Zhao; Möller, Gunnar; Bergholtz, Emil J.

2017-09-01

We investigate extrinsic wormholelike twist defects that effectively increase the genus of space in lattice versions of multicomponent fractional quantum Hall systems. Although the original band structure is distorted by these defects, leading to localized midgap states, we find that a new lowest flat band representing a higher genus system can be engineered by tuning local single-particle potentials. Remarkably, once local many-body interactions in this new band are switched on, we identify various Abelian and non-Abelian fractional quantum Hall states, whose ground-state degeneracy increases with the number of defects, i.e, with the genus of space. This sensitivity of topological degeneracy to defects provides a "proof of concept" demonstration that genons, predicted by topological field theory as exotic non-Abelian defects tied to a varying topology of space, do exist in realistic microscopic models. Specifically, our results indicate that genons could be created in the laboratory by combining the physics of artificial gauge fields in cold atom systems with already existing holographic beam shaping methods for creating twist defects.

Designs for a quantum electron microscope

Energy Technology Data Exchange (ETDEWEB)

Kruit, P., E-mail: p.kruit@tudelft.nl [Department of Imaging Physics, Delft University of Technology, Lorentzweg 1, 2628CJ Delft (Netherlands); Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Hammer, J.; Thomas, S.; Weber, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A. [Department of Physics, Stanford University, Stanford, California 94305 (United States); Hommelhoff, P. [Department of Physics, Friedrich Alexander University Erlangen-Nürnberg (FAU), Staudtstrasse 1, d-91058 Erlangen (Germany); Berggren, K.K. [Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

2016-05-15

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

Designs for a quantum electron microscope

International Nuclear Information System (INIS)

Kruit, P.; Hobbs, R.G.; Kim, C-S.; Yang, Y.; Manfrinato, V.R.; Hammer, J.; Thomas, S.; Weber, P.; Klopfer, B.; Kohstall, C.; Juffmann, T.; Kasevich, M.A.; Hommelhoff, P.; Berggren, K.K.

2016-01-01

One of the astounding consequences of quantum mechanics is that it allows the detection of a target using an incident probe, with only a low probability of interaction of the probe and the target. This ‘quantum weirdness’ could be applied in the field of electron microscopy to generate images of beam-sensitive specimens with substantially reduced damage to the specimen. A reduction of beam-induced damage to specimens is especially of great importance if it can enable imaging of biological specimens with atomic resolution. Following a recent suggestion that interaction-free measurements are possible with electrons, we now analyze the difficulties of actually building an atomic resolution interaction-free electron microscope, or “quantum electron microscope”. A quantum electron microscope would require a number of unique components not found in conventional transmission electron microscopes. These components include a coherent electron beam-splitter or two-state-coupler, and a resonator structure to allow each electron to interrogate the specimen multiple times, thus supporting high success probabilities for interaction-free detection of the specimen. Different system designs are presented here, which are based on four different choices of two-state-couplers: a thin crystal, a grating mirror, a standing light wave and an electro-dynamical pseudopotential. Challenges for the detailed electron optical design are identified as future directions for development. While it is concluded that it should be possible to build an atomic resolution quantum electron microscope, we have also identified a number of hurdles to the development of such a microscope and further theoretical investigations that will be required to enable a complete interpretation of the images produced by such a microscope. - Highlights: • Quantum electron microscopy has the potential of reducing radiation damage. • QEM requires a fraction of the electron wave to pass through the sample

Improve performance of scanning probe microscopy by balancing tuning fork prongs

International Nuclear Information System (INIS)

Ng, Boon Ping; Zhang Ying; Wei Kok, Shaw; Chai Soh, Yeng

2009-01-01

This paper presents an approach for improving the Q-factor of tuning fork probe used in scanning probe microscopes. The improvement is achieved by balancing the fork prongs with extra mass attachment. An analytical model is proposed to characterize the Q-factor of a tuning fork probe with respect to the attachment of extra mass on the tuning fork prongs, and based on the model, the Q-factors of the unbalanced and balanced tuning fork probes are derived and compared. Experimental results showed that the model fits well the experimental data and the approach can improve the Q-factor by more than a factor of three. The effectiveness of the approach is further demonstrated by applying the balanced probe on an atomic force microscope to obtain improved topographic images.

Not your grandfather's concert hall

Science.gov (United States)

Cooper, Russell; Malenka, Richard; Griffith, Charles; Friedlander, Steven

2004-05-01

The opening of Judy and Arthur Zankel Hall on 12 September 2003, restores Andrew Carnegie's original 1891 concept of having three outstanding auditoriums of different sizes under one roof, and creates a 21st-century venue for music performance and education. With concerts ranging from early music to avant-garde multimedia productions, from jazz to world music, and from solo recitals to chamber music, Zankel Hall expands the breadth and depth of Carnegie Hall's offerings. It allows for the integration of programming across three halls with minifestivals tailored both to the size and strengths of each hall and to the artists and music to be performed. The new flexible space also provides Carnegie Hall with an education center equipped with advanced communications technology. This paper discusses the unique program planned for this facility and how the architects, theatre consultants, and acousticians developed a design that fulfilled the client's expectations and coordinated the construction of the facility under the floor of the main Isaac Stern Auditorium without having to cancel a single performance.

Report of experimental hall subworking group

International Nuclear Information System (INIS)

Miyake, K.; Ohama, T.; Takahashi, K.

1982-01-01

The general plan of constructing the TRISTAN e + e - colliding beam experimental halls may be divided into two parts. The first step is to construct two test-experimental halls associated with the 6.5 GeV x 6.5 GeV e + e - accumulator ring, and the second step is to build four experimental halls at the 30 GeV x 30 GeV e + e - TRISTAN main ring. At this workshop, extensive discussions on the detailed design of the four main ring experimental halls have been made. Four experimental areas will be built at the main ring, and two test-experimental halls at the accumulating ring. Among the four areas at the main ring, two will be used for electron-proton possible as well as electron-positron colliding beam experiment. The other two will be used exclusively for e + e - colliding experiments. Only a preliminary design has been made for these four experimental areas. A tentative plan of a larger experimental hall includes a counting and data processing room, a utility room, and a radiation safety control room. Two smaller halls have simpler structure. The figures of the experimental halls are presented. The two test-experimental halls at the accumulator ring will be used to test the detectors for e + e - colliding experiments before the final installation. The utility rooms designed for the halls are used to supply coolant and electric power of superconducting magnets. At the workshop, various ideas concerning the preliminary plan are presented. (Kato, T.)

75 FR 7467 - Gary E. Hall and Rita C. Hall; Notice of Application Accepted for Filing With the Commision...

Science.gov (United States)

2010-02-19

... Rita C. Hall; Notice of Application Accepted for Filing With the Commision, Soliciting Motions To.... Project No.: 13652-000. c. Date filed: January 11, 2010. d. Applicant: Gary E. Hall and Rita C. Hall. e... Policies Act of 1978, 16 U.S.C. 2705, 2708. h. Applicant Contact: Mr. Gary E. Hall and Ms. Rita C. Hall, P...

Polarization resolved imaging with a reflection near-field optical microscope

DEFF Research Database (Denmark)

Bozhevolnyi, Sergey I.; Xiao, Mufei; Hvam, Jørn Märcher

1999-01-01

Using a rigorous microscopic point-dipole description of probe-sample interactions, we study imaging with a reflection scanning near-field optical microscope. Optical content, topographical artifacts, sensitivity window-i.e., the scale on which near-field optical images represent mainly optical...... configuration is preferable to the cross-linear one, since it ensures more isotropic (in the surface plane) near-field imaging of surface features. The numerical results are supported with experimental near-field images obtained by using a reflection microscope with an uncoated fiber tip....

Hall Effect Gyrators and Circulators

Science.gov (United States)

Viola, Giovanni; DiVincenzo, David P.

2014-04-01

The electronic circulator and its close relative the gyrator are invaluable tools for noise management and signal routing in the current generation of low-temperature microwave systems for the implementation of new quantum technologies. The current implementation of these devices using the Faraday effect is satisfactory but requires a bulky structure whose physical dimension is close to the microwave wavelength employed. The Hall effect is an alternative nonreciprocal effect that can also be used to produce desired device functionality. We review earlier efforts to use an Ohmically contacted four-terminal Hall bar, explaining why this approach leads to unacceptably high device loss. We find that capacitive coupling to such a Hall conductor has much greater promise for achieving good circulator and gyrator functionality. We formulate a classical Ohm-Hall analysis for calculating the properties of such a device, and show how this classical theory simplifies remarkably in the limiting case of the Hall angle approaching 90°. In this limit, we find that either a four-terminal or a three-terminal capacitive device can give excellent circulator behavior, with device dimensions far smaller than the ac wavelength. An experiment is proposed to achieve GHz-band gyration in millimeter (and smaller) scale structures employing either semiconductor heterostructure or graphene Hall conductors. An inductively coupled scheme for realizing a Hall gyrator is also analyzed.

An electron microscope for the aberration-corrected era

Energy Technology Data Exchange (ETDEWEB)

Krivanek, O.L. [Nion Co., 1102 8th Street, Kirkland, WA 98033 (United States)], E-mail: krivanek.ondrej@gmail.com; Corbin, G.J.; Dellby, N.; Elston, B.F.; Keyse, R.J.; Murfitt, M.F.; Own, C.S.; Szilagyi, Z.S.; Woodruff, J.W. [Nion Co., 1102 8th Street, Kirkland, WA 98033 (United States)

2008-02-15

Improved resolution made possible by aberration correction has greatly increased the demands on the performance of all parts of high-end electron microscopes. In order to meet these demands, we have designed and built an entirely new scanning transmission electron microscope (STEM). The microscope includes a flexible illumination system that allows the properties of its probe to be changed on-the-fly, a third-generation aberration corrector which corrects all geometric aberrations up to fifth order, an ultra-responsive yet stable five-axis sample stage, and a flexible configuration of optimized detectors. The microscope features many innovations, such as a modular column assembled from building blocks that can be stacked in almost any order, in situ storage and cleaning facilities for up to five samples, computer-controlled loading of samples into the column, and self-diagnosing electronics. The microscope construction is described, and examples of its capabilities are shown.

An electron microscope for the aberration-corrected era

International Nuclear Information System (INIS)

Krivanek, O.L.; Corbin, G.J.; Dellby, N.; Elston, B.F.; Keyse, R.J.; Murfitt, M.F.; Own, C.S.; Szilagyi, Z.S.; Woodruff, J.W.

2008-01-01

Improved resolution made possible by aberration correction has greatly increased the demands on the performance of all parts of high-end electron microscopes. In order to meet these demands, we have designed and built an entirely new scanning transmission electron microscope (STEM). The microscope includes a flexible illumination system that allows the properties of its probe to be changed on-the-fly, a third-generation aberration corrector which corrects all geometric aberrations up to fifth order, an ultra-responsive yet stable five-axis sample stage, and a flexible configuration of optimized detectors. The microscope features many innovations, such as a modular column assembled from building blocks that can be stacked in almost any order, in situ storage and cleaning facilities for up to five samples, computer-controlled loading of samples into the column, and self-diagnosing electronics. The microscope construction is described, and examples of its capabilities are shown

Optical characterication of probes for photon scanning tunnelling microscopy

DEFF Research Database (Denmark)

Vohnsen, Brian; Bozhevolnyi, Sergey I.

1999-01-01

The photon scanning tunnelling microscope is a well-established member of the family of scanning near-field optical microscopes used for optical imaging at the sub-wavelength scale. The quality of the probes, typically pointed uncoated optical fibres, used is however difficult to evaluate...

Scanning Probe Microscopy at 650 °C in Air

DEFF Research Database (Denmark)

Hansen, Karin Vels; Jacobsen, Torben; Nørgaard, Anne-Mette

2009-01-01

The controlled atmosphere high temperature scanning probe microscope was designed to study the electrical properties of surfaces at elevated temperatures by using the probe as an electrode. The capability of a simultaneous acquisition of topographical and electrical data for the same surface area...

The extended wedge method: atomic force microscope friction calibration for improved tolerance to instrument misalignments, tip offset, and blunt probes.

Science.gov (United States)

Khare, H S; Burris, D L

2013-05-01

One of the major challenges in understanding and controlling friction is the difficulty in bridging the length and time scales of macroscale contacts and those of the single asperity interactions they comprise. While the atomic force microscope (AFM) offers a unique ability to probe tribological surfaces in a wear-free single-asperity contact, instrument calibration challenges have limited the usefulness of this technique for quantitative nanotribological studies. A number of lateral force calibration techniques have been proposed and used, but none has gained universal acceptance due to practical considerations, configuration limitations, or sensitivities to unknowable error sources. This paper describes a simple extension of the classic wedge method of AFM lateral force calibration which: (1) allows simultaneous calibration and measurement on any substrate, thus eliminating prior tip damage and confounding effects of instrument setup adjustments; (2) is insensitive to adhesion, PSD cross-talk, transducer/piezo-tube axis misalignment, and shear-center offset; (3) is applicable to integrated tips and colloidal probes; and (4) is generally applicable to any reciprocating friction coefficient measurement. The method was applied to AFM measurements of polished carbon (99.999% graphite) and single crystal MoS2 to demonstrate the technique. Carbon and single crystal MoS2 had friction coefficients of μ = 0.20 ± 0.04 and μ = 0.006 ± 0.001, respectively, against an integrated Si probe. Against a glass colloidal sphere, MoS2 had a friction coefficient of μ = 0.005 ± 0.001. Generally, the measurement uncertainties ranged from 10%-20% and were driven by the effect of actual frictional variation on the calibration rather than calibration error itself (i.e., due to misalignment, tip-offset, or probe radius).

Opto-mechano-electrical tripling in ZnO nanowires probed by photocurrent spectroscopy in a high-resolution transmission electron microscope

Energy Technology Data Exchange (ETDEWEB)

Zhang, C.; Golberg, D., E-mail: xuzhi@iphy.ac.cn, E-mail: golberg.dmitri@nims.go.jp [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Graduate School of Pure and Applied Sciences, University of Tsukuba, Tennodai 1, Tsukuba, Ibaraki 3058577 (Japan); Xu, Z., E-mail: xuzhi@iphy.ac.cn, E-mail: golberg.dmitri@nims.go.jp [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Kvashnin, D. G. [National University of Science and Technology, MISIS, Leninskiy Prospect 4, Moscow 119049 (Russian Federation); Tang, D.-M.; Xue, Y. M.; Bando, Y. [International Center for Materials Nanoarchitectonics (MANA), National Institute for Materials Science (NIMS), Namiki 1-1, Tsukuba, Ibaraki 3050044 (Japan); Sorokin, P. B. [National University of Science and Technology, MISIS, Leninskiy Prospect 4, Moscow 119049 (Russian Federation); Moscow Institute of Physics and Technology, Institutsky Lane 9, Dolgoprudny 141700 (Russian Federation)

2015-08-31

Photocurrent spectroscopy of individual free-standing ZnO nanowires inside a high-resolution transmission electron microscope (TEM) is reported. By using specially designed optical in situ TEM system capable of scanning tunneling microscopy probing paired with light illumination, opto-mechano-electrical tripling phenomenon in ZnO nanowires is demonstrated. Splitting of photocurrent spectra at around 3.3 eV under in situ TEM bending of ZnO nanowires directly corresponds to nanowire deformation and appearance of expanded and compressed nanowire sides. Theoretical simulation of a bent ZnO nanowire has an excellent agreement with the experimental data. The splitting effect could be explained by a change in the valence band structure of ZnO nanowires due to a lattice strain. The strain-induced splitting provides important clues for future flexible piezo-phototronics.

Theoretical analysis of a dual-probe scanning tunneling microscope setup on graphene

DEFF Research Database (Denmark)

Settnes, Mikkel; Power, Stephen R.; Petersen, Dirch Hjorth

2014-01-01

Experimental advances allow for the inclusion of multiple probes to measure the transport properties of a sample surface. We develop a theory of dual-probe scanning tunneling microscopy using a Green's function formalism, and apply it to graphene. Sampling the local conduction properties at finite...... to different scattering processes. We compute the conductance maps of graphene systems with different edge geometries or height fluctuations to determine the effects of nonideal graphene samples on dual-probe measurements. © 2014 American Physical Society....

Topological honeycomb magnon Hall effect: A calculation of thermal Hall conductivity of magnetic spin excitations

Energy Technology Data Exchange (ETDEWEB)

Owerre, S. A., E-mail: solomon@aims.ac.za [African Institute for Mathematical Sciences, 6 Melrose Road, Muizenberg, Cape Town 7945, South Africa and Perimeter Institute for Theoretical Physics, 31 Caroline St. N., Waterloo, Ontario N2L 2Y5 (Canada)

2016-07-28

Quite recently, the magnon Hall effect of spin excitations has been observed experimentally on the kagome and pyrochlore lattices. The thermal Hall conductivity κ{sup xy} changes sign as a function of magnetic field or temperature on the kagome lattice, and κ{sup xy} changes sign upon reversing the sign of the magnetic field on the pyrochlore lattice. Motivated by these recent exciting experimental observations, we theoretically propose a simple realization of the magnon Hall effect in a two-band model on the honeycomb lattice. The magnon Hall effect of spin excitations arises in the usual way via the breaking of inversion symmetry of the lattice, however, by a next-nearest-neighbour Dzyaloshinsky-Moriya interaction. We find that κ{sup xy} has a fixed sign for all parameter regimes considered. These results are in contrast to the Lieb, kagome, and pyrochlore lattices. We further show that the low-temperature dependence on the magnon Hall conductivity follows a T{sup 2} law, as opposed to the kagome and pyrochlore lattices. These results suggest an experimental procedure to measure thermal Hall conductivity within a class of 2D honeycomb quantum magnets and ultracold atoms trapped in a honeycomb optical lattice.

Tunneling Anomalous and Spin Hall Effects.

Science.gov (United States)

Matos-Abiague, A; Fabian, J

2015-07-31

We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

Quantum hall effect. A perspective

International Nuclear Information System (INIS)

Aoki, Hideo

2006-01-01

Novel concepts and phenomena are emerging recently in the physics of quantum Hall effect. This article gives an overview, which starts from the fractional quantum Hall system viewed as an extremely strongly correlated system, and move on to present various phenomena involving internal degrees of freedom (spin and layer), non-equilibrium and optical properties, and finally the spinoff to anomalous Hall effect and the rotating Bose-Einstein condensate. (author)

Planar Hall effect bridge magnetic field sensors

DEFF Research Database (Denmark)

Henriksen, A.D.; Dalslet, Bjarke Thomas; Skieller, D.H.

2010-01-01

Until now, the planar Hall effect has been studied in samples with cross-shaped Hall geometry. We demonstrate theoretically and experimentally that the planar Hall effect can be observed for an exchange-biased ferromagnetic material in a Wheatstone bridge topology and that the sensor signal can...... Hall effect bridge sensors....

Near-field scanning optical microscopy using polymethylmethacrylate optical fiber probes

International Nuclear Information System (INIS)

Chibani, H.; Dukenbayev, K.; Mensi, M.; Sekatskii, S.K.; Dietler, G.

2010-01-01

We report the first use of polymethylmethacrylate (PMMA) optical fiber-made probes for scanning near-field optical microscopy (SNOM). The sharp tips were prepared by chemical etching of the fibers in ethyl acetate, and the probes were prepared by proper gluing of sharpened fibers onto the tuning fork in the conditions of the double resonance (working frequency of a tuning fork coincides with the resonance frequency of dithering of the free-standing part of the fiber) reported earlier for the case of glass fibers. Quality factors of the probes in the range 2000-6000 were obtained, which enables the realization of an excellent topographical resolution including state-of-art imaging of single DNA molecules. Near-field optical performance of the microscope is illustrated by the Photon Scanning Tunneling Microscope images of fluorescent beads with a diameter of 100 nm. The preparation of these plastic fiber probes proved to be easy, needs no hazardous material and/or procedures, and typical lifetime of a probe essentially exceeds that characteristic for the glass fiber probe.

Hall viscosity of hierarchical quantum Hall states

Science.gov (United States)

Fremling, M.; Hansson, T. H.; Suorsa, J.

2014-03-01

Using methods based on conformal field theory, we construct model wave functions on a torus with arbitrary flat metric for all chiral states in the abelian quantum Hall hierarchy. These functions have no variational parameters, and they transform under the modular group in the same way as the multicomponent generalizations of the Laughlin wave functions. Assuming the absence of Berry phases upon adiabatic variations of the modular parameter τ, we calculate the quantum Hall viscosity and find it to be in agreement with the formula, given by Read, which relates the viscosity to the average orbital spin of the electrons. For the filling factor ν =2/5 Jain state, which is at the second level in the hierarchy, we compare our model wave function with the numerically obtained ground state of the Coulomb interaction Hamiltonian in the lowest Landau level, and find very good agreement in a large region of the complex τ plane. For the same example, we also numerically compute the Hall viscosity and find good agreement with the analytical result for both the model wave function and the numerically obtained Coulomb wave function. We argue that this supports the notion of a generalized plasma analogy that would ensure that wave functions obtained using the conformal field theory methods do not acquire Berry phases upon adiabatic evolution.

Spin Hall effect by surface roughness

KAUST Repository

Zhou, Lingjun

2015-01-08

The spin Hall and its inverse effects, driven by the spin orbit interaction, provide an interconversion mechanism between spin and charge currents. Since the spin Hall effect generates and manipulates spin current electrically, to achieve a large effect is becoming an important topic in both academia and industries. So far, materials with heavy elements carrying a strong spin orbit interaction, provide the only option. We propose here a new mechanism, using the surface roughness in ultrathin films, to enhance the spin Hall effect without heavy elements. Our analysis based on Cu and Al thin films suggests that surface roughness is capable of driving a spin Hall angle that is comparable to that in bulk Au. We also demonstrate that the spin Hall effect induced by surface roughness subscribes only to the side-jump contribution but not the skew scattering. The paradigm proposed in this paper provides the second, not if only, alternative to generate a sizable spin Hall effect.

Magneto-optical Faraday effect probed in a scanning tunneling microscope

NARCIS (Netherlands)

Prins, M.W.J.; Wielen, van der M.C.M.M.; Abraham, D.L.; Kempen, van H.; Kesteren, van H.W.

1994-01-01

Semiconductor tips are used as local photodetectors in a scanning tunneling microscope. We demonstrate that this configuration is sensitive to small light intensity variations, as supported by a simple model. The principle is applied to the detection of Faraday ellipticity of a Pt/Co multilayer

Gauge invariance and fractional quantized Hall effect

International Nuclear Information System (INIS)

Tao, R.; Wu, Y.S.

1984-01-01

It is shown that gauge invariance arguments imply the possibility of fractional quantized Hall effect; the Hall conductance is accurately quantized to a rational value. The ground state of a system showing the fractional quantized Hall effect must be degenerate; the non-degenerate ground state can only produce the integral quantized Hall effect. 12 references

Scanning laser microscope for imaging nanostructured superconductors

International Nuclear Information System (INIS)

Ishida, Takekazu; Arai, Kohei; Akita, Yukio; Miyanari, Mitsunori; Minami, Yusuke; Yotsuya, Tsutomu; Kato, Masaru; Satoh, Kazuo; Uno, Mayumi; Shimakage, Hisashi; Miki, Shigehito; Wang, Zhen

2010-01-01

The nanofabrication of superconductors yields various interesting features in superconducting properties. A variety of different imaging techniques have been developed for probing the local superconducting profiles. A scanning pulsed laser microscope has been developed by the combination of the XYZ piezo-driven stages and an optical fiber with an aspheric focusing lens. The scanning laser microscope is used to understand the position-dependent properties of a superconducting MgB 2 stripline of length 100 μm and width of 3 μm under constant bias current. Our results show that the superconducting stripline can clearly be seen in the contour image of the scanning laser microscope on the signal voltage. It is suggested from the observed image that the inhomogeneity is relevant in specifying the operating conditions such as detection efficiency of the sensor.

Scanning laser microscope for imaging nanostructured superconductors

Science.gov (United States)

Ishida, Takekazu; Arai, Kohei; Akita, Yukio; Miyanari, Mitsunori; Minami, Yusuke; Yotsuya, Tsutomu; Kato, Masaru; Satoh, Kazuo; Uno, Mayumi; Shimakage, Hisashi; Miki, Shigehito; Wang, Zhen

2010-10-01

The nanofabrication of superconductors yields various interesting features in superconducting properties. A variety of different imaging techniques have been developed for probing the local superconducting profiles. A scanning pulsed laser microscope has been developed by the combination of the XYZ piezo-driven stages and an optical fiber with an aspheric focusing lens. The scanning laser microscope is used to understand the position-dependent properties of a superconducting MgB 2 stripline of length 100 μm and width of 3 μm under constant bias current. Our results show that the superconducting stripline can clearly be seen in the contour image of the scanning laser microscope on the signal voltage. It is suggested from the observed image that the inhomogeneity is relevant in specifying the operating conditions such as detection efficiency of the sensor.

Edge physics of the quantum spin Hall insulator from a quantum dot excited by optical absorption.

Science.gov (United States)

Vasseur, Romain; Moore, Joel E

2014-04-11

The gapless edge modes of the quantum spin Hall insulator form a helical liquid in which the direction of motion along the edge is determined by the spin orientation of the electrons. In order to probe the Luttinger liquid physics of these edge states and their interaction with a magnetic (Kondo) impurity, we consider a setup where the helical liquid is tunnel coupled to a semiconductor quantum dot that is excited by optical absorption, thereby inducing an effective quantum quench of the tunneling. At low energy, the absorption spectrum is dominated by a power-law singularity. The corresponding exponent is directly related to the interaction strength (Luttinger parameter) and can be computed exactly using boundary conformal field theory thanks to the unique nature of the quantum spin Hall edge.

Topologically induced fractional Hall steps in the integer quantum Hall regime of MoS 2

Science.gov (United States)

Firoz Islam, SK; Benjamin, Colin

2016-09-01

The quantum magnetotransport properties of a monolayer of molybdenum disulfide are derived using linear response theory. In particular, the effect of topological terms on longitudinal and Hall conductivity is analyzed. The Hall conductivity exhibits fractional steps in the integer quantum Hall regime. Further complete spin and valley polarization of the longitudinal conductivitity is seen in presence of these topological terms. Finally, the Shubnikov-de Hass oscillations are suppressed or enhanced contingent on the sign of these topological terms.

Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

International Nuclear Information System (INIS)

Seidman, D.N.

1979-06-01

A brief review is presented of: the basic physical principles of the field-ion and atom-probe microscopes; the many applications of these instruments to the study of defects and radiation damage in solids; and the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He in tungsten

Precision of quantization of the hall conductivity in a finite-size sample: Power law

International Nuclear Information System (INIS)

Greshnov, A. A.; Kolesnikova, E. N.; Zegrya, G. G.

2006-01-01

A microscopic calculation of the conductivity in the integer quantum Hall effect (IQHE) mode is carried out. The precision of quantization is analyzed for finite-size samples. The precision of quantization shows a power-law dependence on the sample size. A new scaling parameter describing this dependence is introduced. It is also demonstrated that the precision of quantization linearly depends on the ratio between the amplitude of the disorder potential and the cyclotron energy. The data obtained are compared with the results of magnetotransport measurements in mesoscopic samples

Magnetic Measuring Instrumentation with Radiation-Resistant Hall Sensors for Fusion Reactors: Experience of Testing at JET

Czech Academy of Sciences Publication Activity Database

Bolshakova, I.; Quercia, A.; Coccorese, V.; Murari, A.; Holyaka, R.; Ďuran, Ivan; Viererbl, L.; Konopleva, R.; Yerashok, V.

2012-01-01

Roč. 59, č. 4 (2012), s. 1224-1231 ISSN 0018-9499. [International Conference on Advancements in Nuclear Instrumentation, Measurement Methods and their Applications. Ghent, 06.06.2011-09.06.2011] R&D Projects: GA ČR GAP205/10/2055 Institutional research plan: CEZ:AV0Z20430508 Keywords : plasma * tokamak * JET * Hall probes * radiation resistance Subject RIV: BL - Plasma and Gas Discharge Physics Impact factor: 1.219, year: 2012

公共图书馆建设音乐欣赏厅之研究%Research on the Construction of Music Appreciation Hall in Public Library

Institute of Scientific and Technical Information of China (English)

邓文婷

2015-01-01

ABSTRACT:This paper illustrates the necessity and present situation of the construction of music appreciation hall in public library, analyzes the characteristics and functions of the music appreciation hall, and based on this, probes into the concrete implementation methods for constructing the music appreciation hall in public library.%阐述了公共图书馆建设音乐欣赏厅的必要性与现状，分析了音乐欣赏厅的特点与作用，在此基础上，探讨了公共图书馆建设音乐欣赏厅的具体实施方法。

ac spin-Hall effect

International Nuclear Information System (INIS)

Entin-Wohlman, O.

2005-01-01

Full Text:The spin-Hall effect is described. The Rashba and Dresselhaus spin-orbit interactions are both shown to yield the low temperature spin-Hall effect for strongly localized electrons coupled to phonons. A frequency-dependent electric field E(ω) generates a spin-polarization current, normal to E, due to interference of hopping paths. At zero temperature the corresponding spin-Hall conductivity is real and is proportional to ω 2 . At non-zero temperatures the coupling to the phonons yields an imaginary term proportional to ω. The interference also yields persistent spin currents at thermal equilibrium, at E = 0. The contributions from the Dresselhaus and Rashba interactions to the interference oppose each other

Quantifying touch-feel perception on automotive interiors by a multi-function tribological probe microscope

International Nuclear Information System (INIS)

Liu, X; Chan, M K; Hennessey, B; Ruebenach, T; Alay, G

2005-01-01

In this paper we will report the preliminary study of people's subjective feelings on stroking surfaces of different materials and the measured properties of these surfaces, in order to understand exactly what properties matter and to what extent the different factors weight the human perception. Ten specimens with materials ranging from natural wood, leather to engineered plastics and metal were selected for this study. These specimens were first tested by a group of untrained people for describing their subjective feel sensation in terms of smoothrough, soft-hard, slippery-grippy, warm-cold and overall judgement of like and dislike for the sample being touched. Then the same specimens were measured for their surface properties by various techniques. In particular, the multi-function measurement has been carried out on each of specimens by a novel tribological probe microscope (TPM). The TPM is capable of measuring four functions in a single scan to provide area mappings of topography, friction, Young's modulus and hardness. As the TPM mapping is based on a point-by-point scanning so values of the four measured functions are linked in space and in time, therefore cross correlation between functions can be established. Although the TPM measured area is small compared to fingertip, the results show that the perception is influenced by nano- and microscale structure of surfaces

Nanobits, Nembranes and Micro Four-Point Probes: Customizable Tools for insitu Manipulation and Characterisation of Nanostructures

DEFF Research Database (Denmark)

Bøggild, Peter; Petersen, Dirch Hjorth; Sardan Sukas, Özlem

2010-01-01

We present a range of highly adaptable microtools for direct interaction with nanoscale structures; (i) semiautomatic pick-and-place assembly of multiwalled carbon nanotubes onto cantilevers for high-aspect ratio scanning probe microscopy, using electrothermal microgrippers inside a SEM. Topology...... on a cantilever; (ii) scanning micro four point probes allow fast, non- destructive mapping of local electrical properties (sheet resistance and Hall mobility) and hysteresis effects of graphene sheets; (iii) sub 100 nm freestanding devices with wires, heaters, actuators, sensors, resonators and probes were...

Hall effect measurements on proton-irradiated ROSE samples

International Nuclear Information System (INIS)

Biggeri, U.; Bruzzi, M.; Borchi, E.

1997-01-01

Bulk samples obtained from two wafers of a silicon monocrystal material produced by Float-Zone refinement have been analyzed using the four-point probe method. One of the wafers comes from an oxygenated ingot; two sets of pure and oxygenated samples have been irradiated with 24 GeV/c protons in the fluence range from 10 13 p/cm 2 to 2x10 14 p/cm 2 . Van der Pauw resistivity and Hall coefficient have been measured before and after irradiation as a function of the temperature. A thermal treatment (30 minutes at 100C) has been performed to accelerate the reverse annealing effect in the irradiated silicon. The irradiated samples show the same exponential dependence of the resistivity and of the Hall coefficient on the temperature from 370K to 100K, corresponding to the presence of radiation-induced deep energy levels around 0.6-0.7eV in the silicon gap. The free carrier concentrations (n, p) have been evaluated in the investigated fluence range. The inversion of the conductivity type from n to p occurred respectively at 7x10 13 p/cm 2 and at 4x10 13 p/cm 2 before and after the annealing treatment, for both the two sets. Only slight differences have been detected between the pure and oxygenated samples

Anisotropic excitation of surface plasmon polaritons on a metal film by a scattering-type scanning near-field microscope with a non-rotationally-symmetric probe tip

Directory of Open Access Journals (Sweden)

Walla Frederik

2018-01-01

Full Text Available We investigated the excitation of surface plasmon polaritons on gold films with the metallized probe tip of a scattering-type scanning near-field optical microscope (s-SNOM. The emission of the polaritons from the tip, illuminated by near-infrared laser radiation, was found to be anisotropic and not circularly symmetric as expected on the basis of literature data. We furthermore identified an additional excitation channel via light that was reflected off the tip and excited the plasmon polaritons at the edge of the metal film. Our results, while obtained for a non-rotationally-symmetric type of probe tip and thus specific for this situation, indicate that when an s-SNOM is employed for the investigation of plasmonic structures, the unintentional excitation of surface waves and anisotropic surface wave propagation must be considered in order to correctly interpret the signatures of plasmon polariton generation and propagation.

Probing nuclear structure with nucleons

International Nuclear Information System (INIS)

Bauge, E.

2007-01-01

The goal of this lecture is to show how nucleon scattering can be used to probe the structure of target nuclei, and how nucleon scattering observables can be interpreted in terms of nuclear structure using microscopic optical potentials. After a brief overview of the specificities of nucleon-nucleus scattering, and a quick reminder on scattering theory, the main part of this lecture is devoted to the construction of optical potentials in which the target nuclei structure information is folded with an effective interaction. Several examples of such microscopic optical model potentials are given. (author)

Transient measurements with an ultrafast scanning tunneling microscope

DEFF Research Database (Denmark)

Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

1998-01-01

We use a photoconductively gated ultrafast scanning tunneling microscope to resolve laser-induced transients on transmission lines and photoconductors. The photoconductive switch on the tunneling probe is illuminated through a rigidly attached fiber. The use of the fiber enables us to scan across...... the transmission line while the change in delay time between pump beam (on the sample) and probe beam (on the probe) provides the temporal information. The investigated photoconductor sample is a low-temperature-grown GaAs layer placed on a sapphire substrate with a thin, semitransparent gold layer. In tunneling...... mode the probe is sensitive to laser-induced field changes in the semiconductor layer. Laser-induced transient signals of 2.2 ps widths are detected. As for the transmission lines, the signals can be explained by a capacitive coupling across the tunneling gap....

Interfacial scattering effect on anisotropic magnetoresistance and anomalous Hall effect in Ta/Fe multilayers

KAUST Repository

Zhang, Qiang

2017-12-26

The effect of interfacial scattering on anisotropic magnetoresistance (AMR) and anomalous Hall effect (AHE) was studied in the (Ta12n/Fe36n)n multilayers, where the numbers give the thickness in nanometer and n is an integer from 1 to 12. The multilayer structure has been confirmed by the XRR spectra and STEM images of cross-sections. The magneto-transport properties were measured by four-point probe method in Hall bar shaped samples in the temperature range of 5 - 300 K. The AMR increases with n, which could be ascribed to the interfacial spin-orbit scattering. At 5 K, the longitudinal resistivity (ρ) increases by 6.4 times and the anomalous Hall resistivity (ρ) increases by 49.4 times from n =1 to n =12, indicative of the interfacial scattering effect. The skew-scattering, side-jump and intrinsic contributions to the AHE were separated successfully. As n increases from 1 to 12, the intrinsic contribution decreases because of the decaying crystallinity or finite size effect and the intrinsic contribution dominated the AHE for all samples. The side jump changes from negative to positive because the interfacial scattering and intralayer scattering in Fe layers both contribute to side jump in the AHE but with opposite sign.

Theoretical analysis of a dual-probe scanning tunneling microscope setup on graphene.

Science.gov (United States)

Settnes, Mikkel; Power, Stephen R; Petersen, Dirch H; Jauho, Antti-Pekka

2014-03-07

Experimental advances allow for the inclusion of multiple probes to measure the transport properties of a sample surface. We develop a theory of dual-probe scanning tunneling microscopy using a Green's function formalism, and apply it to graphene. Sampling the local conduction properties at finite length scales yields real space conductance maps which show anisotropy for pristine graphene systems and quantum interference effects in the presence of isolated impurities. Spectral signatures in the Fourier transforms of real space conductance maps include characteristics that can be related to different scattering processes. We compute the conductance maps of graphene systems with different edge geometries or height fluctuations to determine the effects of nonideal graphene samples on dual-probe measurements.

Scanning Quantum Cryogenic Atom Microscope

Science.gov (United States)

Yang, Fan; Kollár, Alicia J.; Taylor, Stephen F.; Turner, Richard W.; Lev, Benjamin L.

2017-03-01

Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed-matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity high-resolution scanning probe magnetometers. We introduce a quantum-noise-limited scanning probe magnetometer that can operate from room-to-cryogenic temperatures with unprecedented dc-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. The SQCRAMscope has a field sensitivity of 1.4 nT per resolution-limited point (approximately 2 μ m ) or 6 nT /√{Hz } per point at its duty cycle. Compared to point-by-point sensors, the long length of the BEC provides a naturally parallel measurement, allowing one to measure nearly 100 points with an effective field sensitivity of 600 pT /√{Hz } for each point during the same time as a point-by-point scanner measures these points sequentially. Moreover, it has a noise floor of 300 pT and provides nearly 2 orders of magnitude improvement in magnetic flux sensitivity (down to 10-6 Φ0/√{Hz } ) over previous atomic probe magnetometers capable of scanning near samples. These capabilities are carefully benchmarked by imaging magnetic fields arising from microfabricated wire patterns in a system where samples may be scanned, cryogenically cooled, and easily exchanged. We anticipate the SQCRAMscope will provide charge-transport images at temperatures from room temperature to 4 K in unconventional superconductors and topologically nontrivial materials.

Helium ion beam induced growth of hammerhead AFM probes

NARCIS (Netherlands)

Nanda, G.; Veldhoven, E. van; Maas, D.J.; Sadeghian Marnani, H.; Alkemade, P.F.A.

2015-01-01

The authors report the direct-write growth of hammerhead atomic force microscope (AFM) probes by He+ beam induced deposition of platinum-carbon. In order to grow a thin nanoneedle on top of a conventional AFM probe, the authors move a focused He+ beam during exposure to a PtC precursor gas. In the

Resonant difference-frequency atomic force ultrasonic microscope

Science.gov (United States)

Cantrell, John H. (Inventor); Cantrell, Sean A. (Inventor)

2010-01-01

A scanning probe microscope and methodology called resonant difference-frequency atomic force ultrasonic microscopy (RDF-AFUM), employs an ultrasonic wave launched from the bottom of a sample while the cantilever of an atomic force microscope, driven at a frequency differing from the ultrasonic frequency by one of the contact resonance frequencies of the cantilever, engages the sample top surface. The nonlinear mixing of the oscillating cantilever and the ultrasonic wave in the region defined by the cantilever tip-sample surface interaction force generates difference-frequency oscillations at the cantilever contact resonance. The resonance-enhanced difference-frequency signals are used to create images of nanoscale near-surface and subsurface features.

A combined scanning tunnelling microscope and x-ray interferometer

Science.gov (United States)

Yacoot, Andrew; Kuetgens, Ulrich; Koenders, Ludger; Weimann, Thomas

2001-10-01

A monolithic x-ray interferometer made from silicon and a scanning tunnelling microscope have been combined and used to calibrate grating structures with periodicities of 100 nm or less. The x-ray interferometer is used as a translation stage which moves in discrete steps of 0.192 nm, the lattice spacing of the silicon (220) planes. Hence, movements are traceable to the definition of the metre and the nonlinearity associated with the optical interferometers used to measure displacement in more conventional metrological scanning probe microscopes (MSPMs) removed.

Single electron probes of fractional quantum hall states

Science.gov (United States)

Venkatachalam, Vivek

When electrons are confined to a two dimensional layer with a perpendicular applied magnetic field, such that the ratio of electrons to flux quanta (nu) is a small integer or simple rational value, these electrons condense into remarkable new phases of matter that are strikingly different from the metallic electron gas that exists in the absence of a magnetic field. These phases, called integer or fractional quantum Hall (IQH or FQH) states, appear to be conventional insulators in their bulk, but behave as a dissipationless metal along their edge. Furthermore, electrical measurements of such a system are largely insensitive to the detailed geometry of how the system is contacted or even how large the system is... only the order in which contacts are made appears to matter. This insensitivity to local geometry has since appeared in a number of other two and three dimensional systems, earning them the classification of "topological insulators" and prompting an enormous experimental and theoretical effort to understand their properties and perhaps manipulate these properties to create robust quantum information processors. The focus of this thesis will be two experiments designed to elucidate remarkable properties of the metallic edge and insulating bulk of certain FQH systems. To study such systems, we can use mesoscopic devices known as single electron transistors (SETs). These devices operate by watching single electrons hop into and out of a confining box and into a nearby wire (for measurement). If it is initially unfavorable for an electron to leave the box, it can be made favorable by bringing another charge nearby, modifying the energy of the confined electron and pushing it out of the box and into the nearby wire. In this way, the SET can measure nearby charges. Alternatively, we can heat up the nearby wire to make it easier for electrons to enter and leave the box. In this way, the SET is a sensitive thermometer. First, by operating the SET as an

Pump-probe differencing technique for cavity-enhanced, noise-canceling saturation laser spectroscopy.

Science.gov (United States)

de Vine, Glenn; McClelland, David E; Gray, Malcolm B; Close, John D

2005-05-15

We present an experimental technique that permits mechanical-noise-free, cavity-enhanced frequency measurements of an atomic transition and its hyperfine structure. We employ the 532-nm frequency-doubled output from a Nd:YAG laser and an iodine vapor cell. The cell is placed in a folded ring cavity (FRC) with counterpropagating pump and probe beams. The FRC is locked with the Pound-Drever-Hall technique. Mechanical noise is rejected by differencing the pump and probe signals. In addition, this differenced error signal provides a sensitive measure of differential nonlinearity within the FRC.

Hall C

Data.gov (United States)

Federal Laboratory Consortium — Hall C's initial complement of equipment (shown in the figure), includes two general-purpose magnetic spectrometers. The High Momentum Spectrometer (HMS) has a large...

Hall A

Data.gov (United States)

Federal Laboratory Consortium — The instrumentation in Hall A at the Thomas Jefferson National Accelerator Facility was designed to study electroand photo-induced reactions at very high luminosity...

The measurement and calculation of the X-ray spatial resolution obtained in the analytical electron microscope

International Nuclear Information System (INIS)

Michael, J.R.; Williams, D.B.

1990-01-01

The X-ray microanalytical spatial resolution is determined experimentally in various analytical electron microscopes by measuring the degradation of an atomically discrete composition profile across an interphase interface in a thin-foil of Ni-Cr-Fe. The experimental spatial resolutions are then compared with calculated values. The calculated spatial resolutions are obtained by the mathematical convolution of the electron probe size with an assumed beam-broadening distribution and the single-scattering model of beam broadening. The probe size is measured directly from an image of the probe in a TEM/SETEM and indirectly from dark-field signal changes resulting from scanning the probe across the edge of an MgO crystal in a dedicated STEM. This study demonstrates the applicability of the convolution technique to the calculation of the microanalytical spatial resolution obtained in the analytical electron microscope. It is demonstrated that, contrary to popular opinion, the electron probe size has a major impact on the measured spatial resolution in foils < 150 nm thick. (author)

Flux and Hall states in ABJM with dynamical flavors

Energy Technology Data Exchange (ETDEWEB)

Bea, Yago [Departamento de Física de Partículas and Instituto Galego de Física de Altas Enerxías,Universidade de Santiago de Compostela,E-15782 Santiago de Compostela (Spain); Jokela, Niko [Department of Physics and Helsinki Institute of Physics, University of Helsinki,P.O. Box 64, FIN-00014 (Finland); Lippert, Matthew [Institute for Theoretical Physics, University of Amsterdam,1098XH Amsterdam (Netherlands); Ramallo, Alfonso V. [Departamento de Física de Partículas and Instituto Galego de Física de Altas Enerxías,Universidade de Santiago de Compostela,E-15782 Santiago de Compostela (Spain); Zoakos, Dimitrios [Centro de Física do Porto and Departamento de Física e Astronomia,Faculdade de Ciências da Universidade do Porto,Rua do Campo Alegre 687, 4169-007 Porto (Portugal)

2015-03-02

We study the physics of probe D6-branes with quantized internal worldvolume flux in the ABJM background with unquenched massless flavors. This flux breaks parity in the (2+1)-dimensional gauge theory and allows quantum Hall states. Parity breaking is also explicitly demonstrated via the helicity dependence of the meson spectrum. We obtain general expressions for the conductivities, both in the gapped Minkowski embeddings and in the compressible black hole ones. These conductivities depend on the flux and contain a contribution from the dynamical flavors which can be regarded as an effect of intrinsic disorder due to quantum fluctuations of the fundamentals. We present an explicit, analytic family of supersymmetric solutions with nonzero charge density, electric, and magnetic fields.

Flux and Hall states in ABJM with dynamical flavors

Science.gov (United States)

Bea, Yago; Jokela, Niko; Lippert, Matthew; Ramallo, Alfonso V.; Zoakos, Dimitrios

2015-03-01

We study the physics of probe D6-branes with quantized internal worldvolume flux in the ABJM background with unquenched massless flavors. This flux breaks parity in the (2+1)-dimensional gauge theory and allows quantum Hall states. Parity breaking is also explicitly demonstrated via the helicity dependence of the meson spectrum. We obtain general expressions for the conductivities, both in the gapped Minkowski embeddings and in the compressible black hole ones. These conductivities depend on the flux and contain a contribution from the dynamical flavors which can be regarded as an effect of intrinsic disorder due to quantum fluctuations of the fundamentals. We present an explicit, analytic family of supersymmetric solutions with nonzero charge density, electric, and magnetic fields.

Facility Effect Characterization Test of NASA's HERMeS Hall Thruster

Science.gov (United States)

Huang, Wensheng; Kamhawi, Hani; Haag, Thomas W.; Ortega, Alejandro Lopez; Mikellides, Ioannis G.

2016-01-01

A test to characterize the effect of varying background pressure on NASA's 12.5-kW Hall Effect Rocket with Magnetic Shielding had being completed. This thruster is the baseline propulsion system for the Solar Electric Propulsion Technology Demonstration Mission (SEP TDM). Potential differences in thruster performance and oscillation characteristics when in ground facilities versus on-orbit are considered a primary risk for the propulsion system of the Asteroid Redirect Robotic Mission, which is a candidate for SEP TDM. The first primary objective of this test was to demonstrate that the tools being developed to predict the zero-background-pressure behavior of the thruster can provide self-consistent results. The second primary objective of this test was to provide data for refining a physics-based model of the thruster plume that will be used in spacecraft interaction studies. Diagnostics deployed included a thrust stand, Faraday probe, Langmuir probe, retarding potential analyzer, Wien filter spectrometer, and high-speed camera. From the data, a physics-based plume model was refined. Comparisons of empirical data to modeling results are shown.

Energy dispersive X-ray analysis in the electron microscope

CERN Document Server

Bell, DC

2003-01-01

This book provides an in-depth description of x-ray microanalysis in the electron microscope. It is sufficiently detailed to ensure that novices will understand the nuances of high-quality EDX analysis. Includes information about hardware design as well as the physics of x-ray generation, absorption and detection, and most post-detection data processing. Details on electron optics and electron probe formation allow the novice to make sensible adjustments to the electron microscope in order to set up a system which optimises analysis. It also helps the reader determine which microanalytical me

Fundamental limits to frequency estimation: a comprehensive microscopic perspective

Science.gov (United States)

Haase, J. F.; Smirne, A.; Kołodyński, J.; Demkowicz-Dobrzański, R.; Huelga, S. F.

2018-05-01

We consider a metrology scenario in which qubit-like probes are used to sense an external field that affects their energy splitting in a linear fashion. Following the frequency estimation approach in which one optimizes the state and sensing time of the probes to maximize the sensitivity, we provide a systematic study of the attainable precision under the impact of noise originating from independent bosonic baths. Specifically, we invoke an explicit microscopic derivation of the probe dynamics using the spin-boson model with weak coupling of arbitrary geometry. We clarify how the secular approximation leads to a phase-covariant (PC) dynamics, where the noise terms commute with the field Hamiltonian, while the inclusion of non-secular contributions breaks the PC. Moreover, unless one restricts to a particular (i.e., Ohmic) spectral density of the bath modes, the noise terms may contain relevant information about the frequency to be estimated. Thus, by considering general evolutions of a single probe, we study regimes in which these two effects have a non-negligible impact on the achievable precision. We then consider baths of Ohmic spectral density yet fully accounting for the lack of PC, in order to characterize the ultimate attainable scaling of precision when N probes are used in parallel. Crucially, we show that beyond the semigroup (Lindbladian) regime the Zeno limit imposing the 1/N 3/2 scaling of the mean squared error, recently derived assuming PC, generalises to any dynamics of the probes, unless the latter are coupled to the baths in the direction perfectly transversal to the frequency encoding—when a novel scaling of 1/N 7/4 arises. As our microscopic approach covers all classes of dissipative dynamics, from semigroup to non-Markovian ones (each of them potentially non-phase-covariant), it provides an exhaustive picture, in which all the different asymptotic scalings of precision naturally emerge.

75 FR 22770 - Gary E. Hall and Rita Hall; Notice of Availability of Environmental Assessment

Science.gov (United States)

2010-04-30

... DEPARTMENT OF ENERGY Federal Energy Regulatory Commission [Project No. 13652-000-Montana] Gary E. Hall and Rita Hall; Notice of Availability of Environmental Assessment April 22, 2010. In accordance with the National Environmental Policy Act of 1969, as amended, and the Federal Energy Regulatory...

Charge carrier coherence and Hall effect in organic semiconductors

Science.gov (United States)

Yi, H. T.; Gartstein, Y. N.; Podzorov, V.

2016-01-01

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor. PMID:27025354

Charge carrier coherence and Hall effect in organic semiconductors.

Science.gov (United States)

Yi, H T; Gartstein, Y N; Podzorov, V

2016-03-30

Hall effect measurements are important for elucidating the fundamental charge transport mechanisms and intrinsic mobility in organic semiconductors. However, Hall effect studies frequently reveal an unconventional behavior that cannot be readily explained with the simple band-semiconductor Hall effect model. Here, we develop an analytical model of Hall effect in organic field-effect transistors in a regime of coexisting band and hopping carriers. The model, which is supported by the experiments, is based on a partial Hall voltage compensation effect, occurring because hopping carriers respond to the transverse Hall electric field and drift in the direction opposite to the Lorentz force acting on band carriers. We show that this can lead in particular to an underdeveloped Hall effect observed in organic semiconductors with substantial off-diagonal thermal disorder. Our model captures the main features of Hall effect in a variety of organic semiconductors and provides an analytical description of Hall mobility, carrier density and carrier coherence factor.

Guild Hall retrofit

Energy Technology Data Exchange (ETDEWEB)

1984-08-01

This report demonstrates the economic viability of an exterior rewrap retrofit performed on a public community facility for the performing arts. This facility originally consisted of two mess halls built by the American army. The exterior retrofit consisted of constructing a super-insulated passageway to link the two halls as well as completely wrapping the facility with six millimetre polyethylene to provide an airtight barrier. The roofs and walls were reinsulated and insulation levels were increased to RSI 10.5 in the ceilings and RSI 7.7 in the walls. The installation of a propane fuelled furnace was also included in the retrofit package. Prior to the renovations and retrofitting, the Guild Hall facility was almost unusable. The demonstration project transformed the cold, drafty buildings into an attractive, comfortable and functional centre for the performing arts. Heating requirements have been reduced to 500 MJ/m {sup 2} of floor space annually compared to a predicted 1,760 MJ/m{sup 2} of floor space based on HOTCAN analysis of the heating requirements without the energy conservation measures. 9 figs., 10 tabs.

Electron magnetic chiral dichroism in CrO2 thin films using monochromatic probe illumination in a transmission electron microscope

International Nuclear Information System (INIS)

Loukya, B.; Zhang, X.; Gupta, A.; Datta, R.

2012-01-01

Electron magnetic chiral dichroism (EMCD) has been studied in CrO 2 thin films (with (100) and (110) growth orientations on TiO 2 substrates) using a gun monochromator in an aberration corrected transmission electron microscope operating at 300 kV. Excellent signal-to-noise ratio is obtained at spatial resolution ∼10 nm using a monochromatic probe as compared to conventional parallel illumination, large area convergent beam electron diffraction and scanning transmission electron microscopy techniques of EMCD. Relatively rapid exposure using mono probe illumination enables collection of EMCD spectra in total of 8–9 min in energy filtered imaging mode for a given Cr L 2,3 energy scan (energy range ∼35 eV). We compared the EMCD signal obtained by extracting the Cr L 2,3 spectra under three beam diffraction geometry of two different reciprocal vectors (namely g=110 and 200) and found that the g=200 vector enables acquisition of excellent EMCD signal from relatively thicker specimen area due to the associated larger extinction distance. Orbital to spin moment ratio has been calculated using EMCD sum rules for 3d elements and dichroic spectral features associated with CrO 2 are compared and discussed with XMCD theoretical spectra. - Highlights: ► Electron magnetic circular dichroism (EMCD) of CrO 2 thin film with two different orientations. ► Improved EMCD signal with Gun monochromator illumination. ► Improved EMCD signal with higher g vector.

Laurance David Hall.

Science.gov (United States)

Coxon, Bruce

2011-01-01

An account is given of the life, scientific contributions, and passing of Laurance David Hall (1938-2009), including his early history and education at the University of Bristol, UK, and the synthesis and NMR spectroscopy of carbohydrates and other natural products during ∼20 years of research and teaching at the University of British Columbia in Vancouver, Canada. Lists of graduate students, post-doctoral fellows, and sabbatical visitors are provided for this period. Following a generous endowment by Dr. Herchel Smith, Professor Hall built a new Department of Medicinal Chemistry at Cambridge University, UK, and greatly expanded his researches into the technology and applications of magnetic resonance imaging (MRI) and zero quantum NMR. MRI technology was applied both to medical problems such as the characterization of cartilage degeneration in knee joints, the measurement of ventricular function, lipid localization in animal models of atherosclerosis, paramagnetic metal complexes of polysaccharides as contrast agents, and studies of many other anatomical features, but also to several aspects of materials analysis, including food analyses, process control, and the elucidation of such physical phenomena as the flow of liquids through porous media, defects in concrete, and the visualization of fungal damage to wood. Professor Hall's many publications, patents, lectures, and honors and awards are described, and also his successful effort to keep the Asilomar facility in Pacific Grove, California as the alternating venue for the annual Experimental NMR Conference. Two memorial services for Professor Hall are remembered. Copyright © 2011 Elsevier Inc. All rights reserved.

Pulsed-laser atom-probe field-ion microscopy

International Nuclear Information System (INIS)

Kellogg, G.L.; Tsong, T.T.

1980-01-01

A time-of-flight atom-probe field-ion microscope has been developed which uses nanosecond laser pulses to field evaporate surface species. The ability to operate an atom-probe without using high-voltage pulses is advantageous for several reasons. The spread in energy arising from the desorption of surface species prior to the voltage pulse attaining its maximum amplitude is eliminated, resulting in increased mass resolution. Semiconductor and insulator samples, for which the electrical resistivity is too high to transmit a short-duration voltage pulse, can be examined using pulsed-laser assisted field desorption. Since the electric field at the surface can be significantly smaller, the dissociation of molecular adsorbates by the field can be reduced or eliminated, permitting well-defined studies of surface chemical reactions. In addition to atom-probe operation, pulsed-laser heating of field emitters can be used to study surface diffusion of adatoms and vacancies over a wide range of temperatures. Examples demonstrating each of these advantages are presented, including the first pulsed-laser atom-probe (PLAP) mass spectra for both metals (W, Mo, Rh) and semiconductors (Si). Molecular hydrogen, which desorbs exclusively as atomic hydrogen in the conventional atom probe, is shown to desorb undissociatively in the PLAP. Field-ion microscope observations of the diffusion and dissociation of atomic clusters, the migration of adatoms, and the formation of vacancies resulting from heating with a 7-ns laser pulse are also presented

Study of defects, radiation damage and implanted gases in solids by field-ion and atom-probe microscopy

International Nuclear Information System (INIS)

Seidman, D.N.; Amano, J.; Wagner, A.

1980-10-01

The ability of the field-ion microscope to image individual atoms has been applied, at Cornell University, to the study of fundamental properties of point defects in irradiated or quenched metals. The capability of the atom probe field-ion microscope to determine the chemistry - that is, the mass-to-charge ratio - of a single ion has been used to investigate the behavior of different implanted species in metals. A brief review is presented of: (1) the basic physical principles of the field-ion and atom-probe microscopes; (2) the many applications of these instruments to the study of defects and radiation damage in solids; and (3) the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interests in detail

The Other Hall Effect: College Board Physics

Science.gov (United States)

Sheppard, Keith; Gunning, Amanda M.

2013-01-01

Edwin Herbert Hall (1855-1938), discoverer of the Hall effect, was one of the first winners of the AAPT Oersted Medal for his contributions to the teaching of physics. While Hall's role in establishing laboratory work in high schools is widely acknowledged, his position as chair of the physics section of the Committee on College Entrance…

Anomalous Hall effect in polycrystalline Ni films

KAUST Repository

Guo, Zaibing

2012-02-01

We systematically studied the anomalous Hall effect in a series of polycrystalline Ni films with thickness ranging from 4 to 200 nm. It is found that both the longitudinal and anomalous Hall resistivity increased greatly as film thickness decreased. This enhancement should be related to the surface scattering. In the ultrathin films (46 nm thick), weak localization corrections to anomalous Hall conductivity were studied. The granular model, taking into account the dominated intergranular tunneling, has been employed to explain this phenomenon, which can explain the weak dependence of anomalous Hall resistivity on longitudinal resistivity as well. © 2011 Elsevier Ltd. All rights reserved.

Design and operation of an inexpensive far-field laser scanning microscope suitable for use in an undergraduate laboratory course

Science.gov (United States)

Pallone, Arthur; Hawk, Eric

2013-03-01

Scanning microscope applications span the science disciplines yet their costs limit their use at educational institutions. The basic concepts of scanning microscopy are simple. The microscope probe - whether it produces a photon, electron or ion beam - moves relative to the surface of the sample object. The beam interacts with the sample to produce a detected signal that depends on the desired property to be measured at the probe location on the sample. The microscope transforms the signal for output in a form desired by the user. Undergraduate students can easily construct a far-field laser scanning microscope that illustrates each of these principles from parts available at local electronics and hardware stores and use the microscope to explore properties of devices such as light dependent resistors and biological samples such as leaves. Students can record, analyze and interpret results using a computer and free software.

Elementary theory of quantum Hall effect

Directory of Open Access Journals (Sweden)

Keshav N. Shrivastava

2008-04-01

Full Text Available The Hall effect is the generation of a current perpendicular to both the direction of the applied electric as well as magnetic field in a metal or in a semiconductor. It is used to determine the concentration of electrons. The quantum Hall effect with integer quantization was discovered by von Klitzing and fractionally charged states were found by Tsui, Stormer and Gossard. Robert Laughlin explained the quantization of Hall current by using “flux quantization” and introduced incompressibility to obtain the fractional charge. We have developed the theory of the quantum Hall effect by using the theory of angular momentum. Our predicted fractions are in accord with those measured. We emphasize our explanation of the observed phenomena. We use spin to explain the fractional charge and hence we discover spin-charge locking.

Coaxial atomic force microscope probes for dielectrophoresis of DNA under different buffer conditions

Science.gov (United States)

Tao, Yinglei; Kumar Wickramasinghe, H.

2017-02-01

We demonstrate a coaxial AFM nanoprobe device for dielectrophoretic (DEP) trapping of DNA molecules in Tris-EDTA (TE) and phosphate-buffered saline (PBS) buffers. The DEP properties of 20 nm polystyrene beads were studied with coaxial probes in media with different conductivities. Due to the special geometry of our DEP probe device, sufficiently high electric fields were generated at the probe end to focus DNA molecules with positive DEP. DEP trapping for both polystyrene beads and DNA molecules was quantitatively analyzed over the frequency range from 100 kHz to 50 MHz and compared with the Clausius-Mossotti theory. Finally, we discussed the negative effect of medium salinity during DEP trapping.

Temperature dependence of collapse of quantized hall resistance

International Nuclear Information System (INIS)

Tanaka, Hiroyasu; Kawashima, Hironori; Iizuka, Hisamitsu; Fukuda, Hideaki; Kawaji, Shinji

2006-01-01

Similarity is observed in the deviation of Hall resistance from the quantized value with the increase in the source-drain current I SD in our butterfly-type Hall bars and in the Hall bars used by Jeanneret et al., while changes in the diagonal resistivity ρ xx with I SD are significantly different between these Hall bars. The temperature dependence of the critical Hall electric field F cr (T) for the collapse of R H (4) measured in these Hall bars is approximated using F cr (T) = F cr (0)(1 - (T/T cr ) 2 ). Here, the critical Hall electric field at zero temperature depends on the magnetic field B as F cr (0) ∝ B 3/2 . Theoretical considerations are given on F cr (T) on the basis of a temperature-dependent mobility edge model and a schema of temperature-dependent inter-Landau level tunneling probability arising from the Fermi distribution function. The former does not fit in with the I SD dependence of activation energy in ρ xx . (author)

Prospect of quantum anomalous Hall and quantum spin Hall effect in doped kagome lattice Mott insulators.

Science.gov (United States)

Guterding, Daniel; Jeschke, Harald O; Valentí, Roser

2016-05-17

Electronic states with non-trivial topology host a number of novel phenomena with potential for revolutionizing information technology. The quantum anomalous Hall effect provides spin-polarized dissipation-free transport of electrons, while the quantum spin Hall effect in combination with superconductivity has been proposed as the basis for realizing decoherence-free quantum computing. We introduce a new strategy for realizing these effects, namely by hole and electron doping kagome lattice Mott insulators through, for instance, chemical substitution. As an example, we apply this new approach to the natural mineral herbertsmithite. We prove the feasibility of the proposed modifications by performing ab-initio density functional theory calculations and demonstrate the occurrence of the predicted effects using realistic models. Our results herald a new family of quantum anomalous Hall and quantum spin Hall insulators at affordable energy/temperature scales based on kagome lattices of transition metal ions.

The quantum hall effect

International Nuclear Information System (INIS)

El-Arabi, N. M.

1993-01-01

Transport phenomena in two dimensional semiconductors have revealed unusual properties. In this thesis these systems are considered and discussed. The theories explain the Integral Quantum Hall Effect (IQHE) and the Fractional Quantum Hall Effect (FQHE). The thesis is composed of five chapters. The first and the second chapters lay down the theory of the IQHE, the third and fourth consider the theory of the FQHE. Chapter five deals with the statistics of particles in two dimension. (author). Refs

Scanning tunneling microscope with two-dimensional translator.

Science.gov (United States)

Nichols, J; Ng, K-W

2011-01-01

Since the invention of the scanning tunneling microscope (STM), it has been a powerful tool for probing the electronic properties of materials. Typically STM designs capable of obtaining resolution on the atomic scale are limited to a small area which can be probed. We have built an STM capable of coarse motion in two dimensions, the z- and x-directions which are, respectively, parallel and perpendicular to the tip. This allows us to image samples with very high resolution at sites separated by macroscopic distances. This device is a single unit with a compact design making it very stable. It can operate in either a horizontal or vertical configuration and at cryogenic temperatures.

Paired Hall states

International Nuclear Information System (INIS)

Greiter, M.

1992-01-01

This dissertation contains a collection of individual articles on various topics. Their significance in the corresponding field as well as connections between them are emphasized in a general and comprehensive introduction. In the first article, the author explores the consequences for macroscopic effective Lagrangians of assuming that the momentum density is proportional to the flow of conserved current. The universal corrections obtained for the macroscopic Lagrangian of a superconductor describe the London Hall effect, and provide a fully consistent derivation of it. In the second article, a heuristic principle is proposed for quantized Hall states: the existence and incompressibility of fractionally quantized Hall states is explained by an argument based on an adiabatic localization of magnetic flux, the process of trading uniform flux for an equal amount of fictitious flux attached to the particles. This principle is exactly implemented in the third article. For a certain class of model Hamiltonians, the author obtains Laughlin's Jastrow type wave functions explicitly from a filled Landau level, by smooth extrapolation in quantum statistics. The generalization of this analysis to the torus geometry shows that theorems restricting the possibilities of quantum statistics on closed surfaces are circumvented in the presence of a magnetic field. In the last article, the existence is proposed of a novel incompressible quantum liquid, a paired Hall state, at a half filled Landau level. This state arises adiabatically from free fermions in zero magnetic field, and reduces to a state previously proposed by Halperin in the limit of tightly bound pairs. It supports unusual excitations, including neutral fermions and charge e/4 anyons with statistical parameter θ = π/8

Dr. Hall and the work cure.

Science.gov (United States)

Reed, Kathlyn L

2005-01-01

Herbert James Hall, MD (1870-1923), was a pioneer in the systematic and organized study of occupation as therapy for persons with nervous and mental disorders that he called the "work cure." He began his work in 1904 during the early years of the Arts and Crafts Movement in the United States. His primary interest was the disorder neurasthenia, a condition with many symptoms including chronic fatigue, stress, and inability to work or perform everyday tasks. The prevailing treatment of the day was absolute bed rest known as the "rest cure." Hall believed that neurasthenia was not caused by overwork but by faulty living habits that could be corrected through an ordered life schedule and selected occupations. He identified several principles of therapy that are still used today including graded activity and energy conservation. Dr. Adolph Meyer credits Hall for organizing the ideas on the therapeutic use of occupation (Meyer, 1922). Hall also provided the name American Occupational Therapy Association for the professional organization and served as the fourth president. For his many contributions to the profession Hall deserves to be recognized as a major contributor to the development and organization of occupational therapy.

Quantum Hall effects recent theoretical and experimental developments

CERN Document Server

Ezawa, Zyun Francis

2013-01-01

Enthusiasm for research on the quantum Hall effect (QHE) is unbounded. The QHE is one of the most fascinating and beautiful phenomena in all branches of physics. Tremendous theoretical and experimental developments are still being made in this sphere. Composite bosons, composite fermions and anyons were among distinguishing ideas in the original edition. In the 2nd edition, fantastic phenomena associated with the interlayer phase coherence in the bilayer system were extensively described. The microscopic theory of the QHE was formulated based on the noncommutative geometry. Furthermore, the unconventional QHE in graphene was reviewed, where the electron dynamics can be treated as relativistic Dirac fermions and even the supersymmetric quantum mechanics plays a key role. In this 3rd edition, all chapters are carefully reexamined and updated. A highlight is the new chapter on topological insulators. Indeed, the concept of topological insulator stems from the QHE. Other new topics are recent prominent experime...

Ted Hall and the science of biological microprobe X-ray analysis: a historical perspective of methodology and biological dividends.

Science.gov (United States)

Gupta, B L

1991-06-01

This review surveys the emergence of electron probe X-ray microanalysis as a quantitative method for measuring the chemical elements in situ. The extension of the method to the biological sciences under the influence of Ted Hall is reviewed. Some classical experiments by Hall and his colleagues in Cambridge, UK, previously unpublished, are described; as are some of the earliest quantitative results from the cryo-sections obtained in Cambridge and elsewhere. The progress of the methodology is critically evaluated from the earliest starts to the present state of the art. Particular attention has been focused on the application of the method in providing fresh insights into the role of ions in cell and tissue physiology and pathology. A comprehensive list of references is included for a further pursuit of the topics by the interested reader.

Four-point probe measurements using current probes with voltage feedback to measure electric potentials

Science.gov (United States)

Lüpke, Felix; Cuma, David; Korte, Stefan; Cherepanov, Vasily; Voigtländer, Bert

2018-02-01

We present a four-point probe resistance measurement technique which uses four equivalent current measuring units, resulting in minimal hardware requirements and corresponding sources of noise. Local sample potentials are measured by a software feedback loop which adjusts the corresponding tip voltage such that no current flows to the sample. The resulting tip voltage is then equivalent to the sample potential at the tip position. We implement this measurement method into a multi-tip scanning tunneling microscope setup such that potentials can also be measured in tunneling contact, allowing in principle truly non-invasive four-probe measurements. The resulting measurement capabilities are demonstrated for \

Development of a virtual probe tip with an application to high aspect ratio microscale features

International Nuclear Information System (INIS)

Bauza, Marcin B.; Hocken, Robert J.; Smith, Stuart T.; Woody, Shane C.

2005-01-01

Nondestructive measurement of microscale features remains a challenging metrology problem. For example, to assess a high aspect ratio small hole it is currently common to cut a cross section and measure the features of interest using an atomic force microscope, scanning probe microscope, or scanning electron microscope. Typically, these metrology tools may be suitable for surface finish measurement but often lack the capability for dimensional metrology. The aim of this article is to discuss the development of a high aspect-ratio microscale probe for measurement of microscale features. A 700:1 high aspect ratio probe shank is fabricated with a 7 μm diameter, and attached at one end to an oscillator. The oscillator produces a standing wave in the oscillating probe shank as opposed to conventional probes that use a microscale sphere on the end of a comparatively rigid shank. As a result of the standing wave formed in steady state vibration, the free end of the shank generates an amplitude of oscillation greater than the probe shank diameter. Thus, the probe does not require a spherical ball to serve as the contact point and simply uses the contact diameter of the free end of the vibrating shank. This methodology is referred to as a virtual probe tip. The virtual probe tip in conjunction with a nanopositioning scanner is used to measure surface profile measurements over traverse lengths of 130 μm. In this article, results from profiles of a 500 nm step height and a ruby sphere of diameter 1 mm are presented. Experiments in this article indicate the ability to repeatedly resolve surface features of less than 5 nm while maintaining bandwidths greater than 1 kHz. Furthermore, adhesion problems often encountered with micrometer scaled probes were not observed during profile measurements with this virtual probe

Probing the nanostructural evolution of age-hardenable Al alloys with atom-probe tomography

International Nuclear Information System (INIS)

Biswas, Aniruddha

2010-01-01

Atom Probe Tomographic (APT) Microscope is a lens-less point-projection 3-D analytical microscope that has the unique capability of (i) three-dimensional imaging at the atomic scale and (ii) compositional analysis with sub-nanometre spatial resolution and single-atom sensitivity. Modern 3-D APT microscope offers the highest the spatial resolution among all the available analytical techniques. It can simultaneously achieve a spatial resolution better than 0.3 nm in all three directions of a three-dimensional analysis-volume. As a result, 3-D APT microscopy, especially as practiced by the high speed, large field of view instruments is the most appropriate tool for studying nano-scale precipitates and their heterophase interfaces. This talk will introduce the technique, discuss its brief historical background and use examples from age-hardenable Al-alloys. The results include a detailed APT study of the compositional evolution of the nano-scale precipitates: θ and Q present in commercial age hardenable aluminium alloy, W319

Electromagnetic methods for measuring materials properties of cylindrical rods and array probes for rapid flaw inspection

Energy Technology Data Exchange (ETDEWEB)

Sun, Haiyan [Iowa State Univ., Ames, IA (United States)

2005-01-01

field in the presence of a finite a two-layer rod and a conductive tube. The results are in very good agreement with those obtained by using a 2D finite element code. In the third part, a new probe technology with enhanced flaw detection capability is described. The new probe can reduce inspection time through the use of multiple Hall sensors. A prototype Hall array probe has been built and tested with eight individual Hall sensor ICs and a racetrack coil. Electronic hardware was developed to interface the probes to an oscilloscope or an eddy current instrument. To achieve high spatial resolution and to limit the overall probe size, high-sensitivity Hall sensor arrays were fabricated directly on a wafer using photolithographic techniques and then mounted in their unencapsulated form. The electronic hardware was then updated to interface the new probes to a laptop computer.

Synthesis and characterization of p-type boron-doped IIb diamond large single crystals

International Nuclear Information System (INIS)

Li Shang-Sheng; Li Xiao-Lei; Su Tai-Chao; Jia Xiao-Peng; Ma Hong-An; Huang Guo-Feng; Li Yong

2011-01-01

High-quality p-type boron-doped IIb diamond large single crystals are successfully synthesized by the temperature gradient method in a china-type cubic anvil high-pressure apparatus at about 5.5 GPa and 1600 K. The morphologies and surface textures of the synthetic diamond crystals with different boron additive quantities are characterized by using an optical microscope and a scanning electron microscope respectively. The impurities of nitrogen and boron in diamonds are detected by micro Fourier transform infrared technique. The electrical properties including resistivities, Hall coefficients, Hall mobilities and carrier densities of the synthesized samples are measured by a four-point probe and the Hall effect method. The results show that large p-type boron-doped diamond single crystals with few nitrogen impurities have been synthesized. With the increase of quantity of additive boron, some high-index crystal faces such as {113} gradually disappear, and some stripes and triangle pits occur on the crystal surface. This work is helpful for the further research and application of boron-doped semiconductor diamond. (cross-disciplinary physics and related areas of science and technology)

In situ hybridization at the electron microscope level: hybrid detection by autoradiography and colloidal gold.

Science.gov (United States)

Hutchison, N J; Langer-Safer, P R; Ward, D C; Hamkalo, B A

1982-11-01

In situ hybridization has become a standard method for localizing DNA or RNA sequences in cytological preparations. We developed two methods to extend this technique to the transmission electron microscope level using mouse satellite DNA hybridization to whole mount metaphase chromosomes as the test system. The first method devised is a direct extension of standard light microscope level using mouse satellite DNA hybridization to whole mount metaphase chromosomes as the test system. The first method devised is a direct extension of standard light microscope in situ hybridization. Radioactively labeled complementary RNA (cRNA) is hybridized to metaphase chromosomes deposited on electron microscope grids and fixed in 70 percent ethanol vapor; hybridixation site are detected by autoradiography. Specific and intense labeling of chromosomal centromeric regions is observed even after relatively short exposure times. Inerphase nuclei present in some of the metaphase chromosome preparations also show defined paatterms of satellite DNA labeling which suggests that satellite-containing regions are associate with each other during interphase. The sensitivity of this method is estimated to at least as good as that at the light microscope level while the resolution is improved at least threefold. The second method, which circumvents the use of autoradiogrphic detection, uses biotin-labeled polynucleotide probes. After hybridization of these probes, either DNA or RNA, to fixed chromosomes on grids, hybrids are detected via reaction is improved at least threefold. The second method, which circumvents the use of autoradiographic detection, uses biotin-labeled polynucleotide probes. After hybridization of these probes, either DNA or RNA, to fixed chromosomes on grids, hybrids are detected via reaction with an antibody against biotin and secondary antibody adsorbed to the surface of over centromeric heterochromatin and along the associated peripheral fibers. Labeling is on average

Athermalization in atomic force microscope based force spectroscopy using matched microstructure coupling.

Science.gov (United States)

Torun, H; Finkler, O; Degertekin, F L

2009-07-01

The authors describe a method for athermalization in atomic force microscope (AFM) based force spectroscopy applications using microstructures that thermomechanically match the AFM probes. The method uses a setup where the AFM probe is coupled with the matched structure and the displacements of both structures are read out simultaneously. The matched structure displaces with the AFM probe as temperature changes, thus the force applied to the sample can be kept constant without the need for a separate feedback loop for thermal drift compensation, and the differential signal can be used to cancel the shift in zero-force level of the AFM.

Magnetoresistance in quantum Hall metals due to Pancharatnam ...

Indian Academy of Sciences (India)

Abstract. We derive the trial Hall resistance formula for the quantum Hall metals to address both the integer and fractional quantum Hall effects. Within the degenerate (and crossed) Landau levels, and in the presence of changing magnetic field strength, one can invoke two physical processes responsible for the electron ...

Microscopic Analysis of Corn Fiber Using Corn Starch- and Cellulose-Specific Molecular Probes

Energy Technology Data Exchange (ETDEWEB)

Porter, S. E.; Donohoe, B. S.; Beery, K. E.; Xu, Q.; Ding, S.-Y.; Vinzant, T. B.; Abbas, C. A.; Himmel, M. E.

2007-09-01

Ethanol is the primary liquid transportation fuel produced from renewable feedstocks in the United States today. The majority of corn grain, the primary feedstock for ethanol production, has been historically processed in wet mills yielding products such as gluten feed, gluten meal, starch, and germ. Starch extracted from the grain is used to produce ethanol in saccharification and fermentation steps; however the extraction of starch is not 100% efficient. To better understand starch extraction during the wet milling process, we have developed fluorescent probes that can be used to visually localize starch and cellulose in samples using confocal microscopy. These probes are based on the binding specificities of two types of carbohydrate binding modules (CBMs), which are small substrate-specific protein domains derived from carbohydrate degrading enzymes. CBMs were fused, using molecular cloning techniques, to a green fluorescent protein (GFP) or to the red fluorescent protein DsRed (RFP). Using these engineered probes, we found that the binding of the starch-specific probe correlates with starch content in corn fiber samples. We also demonstrate that there is starch internally localized in the endosperm that may contribute to the high starch content in corn fiber. We also surprisingly found that the cellulose-specific probe did not bind to most corn fiber samples, but only to corn fiber that had been hydrolyzed using a thermochemical process that removes the residual starch and much of the hemicellulose. Our findings should be of interest to those working to increase the efficiency of the corn grain to ethanol process.

Differential magnetic force microscope imaging.

Science.gov (United States)

Wang, Ying; Wang, Zuobin; Liu, Jinyun; Hou, Liwei

2015-01-01

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). © Wiley Periodicals, Inc.

Spin hall effect associated with SU(2) gauge field

Science.gov (United States)

Tao, Y.

2010-01-01

In this paper, we focus on the connection between spin Hall effect and spin force. Here we investigate that the spin force due to spin-orbit coupling, which, in two-dimensional system, is equivalent to forces of Hirsch and Chudnovsky besides constant factors 3 and frac{3}{2} respectively, is a part of classic Anandan force, and that the spin Hall effect is an anomalous Hall effect. Furthermore, we develop the method of AC phase to derive the expression for the spin force, and note that the most basic spin Hall effect indeed originate from the AC phase and is therefore an intrinsic quantum mechanical property of spin. This method differs from approach of Berry phase in the study of anomalous Hall effect , which is the intrinsic property of the perfect crystal. On the other hand, we use an elegant skill to show that the Chudnovsky-Drude model is reasonable. Here we have improved the theoretical values of spin Hall conductivity of Chudnovsky. Compared to the theoretical values of spin Hall conductivity in the Chudnovsky-Drude model, ours are in better agreement with experimentation. Finally, we discuss the relation between spin Hall effect and fractional statistics.

Probe Microscopic Studies of DNA Molecules on Carbon Nanotubes

Directory of Open Access Journals (Sweden)

Kazuo Umemura

2016-10-01

Full Text Available Hybrids of DNA and carbon nanotubes (CNTs are promising nanobioconjugates for nanobiosensors, carriers for drug delivery, and other biological applications. In this review, nanoscopic characterization of DNA-CNT hybrids, in particular, characterization by scanning probe microscopy (SPM, is summarized. In many studies, topographical imaging by atomic force microscopy has been performed. However, some researchers have demonstrated advanced SPM operations in order to maximize its unique and valuable functions. Such sophisticated approaches are attractive and will have a significant impact on future studies of DNA-CNT hybrids.

Hall Sensor Output Signal Fault-Detection & Safety Implementation Logic

Directory of Open Access Journals (Sweden)

Lee SangHun

2016-01-01

Full Text Available Recently BLDC motors have been popular in various industrial applications and electric mobility. Recently BLDC motors have been popular in various industrial applications and electric mobility. In most brushless direct current (BLDC motor drives, there are three hall sensors as a position reference. Low resolution hall effect sensor is popularly used to estimate the rotor position because of its good comprehensive performance such as low cost, high reliability and sufficient precision. Various possible faults may happen in a hall effect sensor. This paper presents a fault-tolerant operation method that allows the control of a BLDC motor with one faulty hall sensor and presents the hall sensor output fault-tolerant control strategy. The situations considered are when the output from a hall sensor stays continuously at low or high levels, or a short-time pulse appears on a hall sensor signal. For fault detection, identification of a faulty signal and generating a substitute signal, this method only needs the information from the hall sensors. There are a few research work on hall effect sensor failure of BLDC motor. The conventional fault diagnosis methods are signal analysis, model based analysis and knowledge based analysis. The proposed method is signal based analysis using a compensation signal for reconfiguration and therefore fault diagnosis can be fast. The proposed method is validated to execute the simulation using PSIM.

Imaging the p-n junction in a gallium nitride nanowire with a scanning microwave microscope

Energy Technology Data Exchange (ETDEWEB)

Imtiaz, Atif [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Department of Electrical, Computer, and Energy Engineering, University of Colorado, Boulder, Colorado 80309 (United States); Wallis, Thomas M.; Brubaker, Matt D.; Blanchard, Paul T.; Bertness, Kris A.; Sanford, Norman A.; Kabos, Pavel, E-mail: kabos@boulder.nist.gov [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Weber, Joel C. [Physical Measurement Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States); Department of Mechanical Engineering, University of Colorado, Boulder, Colorado 80309 (United States); Coakley, Kevin J. [Information Technology Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305 (United States)

2014-06-30

We used a broadband, atomic-force-microscope-based, scanning microwave microscope (SMM) to probe the axial dependence of the charge depletion in a p-n junction within a gallium nitride nanowire (NW). SMM enables the visualization of the p-n junction location without the need to make patterned electrical contacts to the NW. Spatially resolved measurements of S{sub 11}{sup ′}, which is the derivative of the RF reflection coefficient S{sub 11} with respect to voltage, varied strongly when probing axially along the NW and across the p-n junction. The axial variation in S{sub 11}{sup ′}  effectively mapped the asymmetric depletion arising from the doping concentrations on either side of the junction. Furthermore, variation of the probe tip voltage altered the apparent extent of features associated with the p-n junction in S{sub 11}{sup ′} images.

The quantized Hall effect

International Nuclear Information System (INIS)

Klitzing von, K.

1989-01-01

The quantized Hall effect is theoretically explained in detail as are its basic properties. The explanation is completed with the pertinent mathematical relations and illustrative figures. Experimental data are critically assessed obtained by quantum transport measurement in a magnetic field on two-dimensional systems. The results are reported for a MOSFET silicon transistor and for GaAs-Al x Ga 1-x As heterostructures. The application is discussed of the quantized Hall effect in determining the fine structure constant or in implementing the resistance standard. (M.D.). 27 figs., 57 refs

Valley-chiral quantum Hall state in graphene superlattice structure

Science.gov (United States)

Tian, H. Y.; Tao, W. W.; Wang, J.; Cui, Y. H.; Xu, N.; Huang, B. B.; Luo, G. X.; Hao, Y. H.

2016-05-01

We theoretically investigate the quantum Hall effect in a graphene superlattice (GS) system, in which the two valleys of graphene are coupled together. In the presence of a perpendicular magnetic field, an ordinary quantum Hall effect is found with the sequence σxy=ν e^2/h(ν=0,+/-1,+/-2,\\cdots) . At the zeroth Hall platform, a valley-chiral Hall state stemming from the single K or K' valley is found and it is localized only on one sample boundary contributing to the longitudinal conductance but not to the Hall conductivity. Our findings may shed light on the graphene-based valleytronics applications.

A Scanning Quantum Cryogenic Atom Microscope

Science.gov (United States)

Lev, Benjamin

Microscopic imaging of local magnetic fields provides a window into the organizing principles of complex and technologically relevant condensed matter materials. However, a wide variety of intriguing strongly correlated and topologically nontrivial materials exhibit poorly understood phenomena outside the detection capability of state-of-the-art high-sensitivity, high-resolution scanning probe magnetometers. We introduce a quantum-noise-limited scanning probe magnetometer that can operate from room-to-cryogenic temperatures with unprecedented DC-field sensitivity and micron-scale resolution. The Scanning Quantum Cryogenic Atom Microscope (SQCRAMscope) employs a magnetically levitated atomic Bose-Einstein condensate (BEC), thereby providing immunity to conductive and blackbody radiative heating. The SQCRAMscope has a field sensitivity of 1.4 nT per resolution-limited point (2 um), or 6 nT / Hz1 / 2 per point at its duty cycle. Compared to point-by-point sensors, the long length of the BEC provides a naturally parallel measurement, allowing one to measure nearly one-hundred points with an effective field sensitivity of 600 pT / Hz1 / 2 each point during the same time as a point-by-point scanner would measure these points sequentially. Moreover, it has a noise floor of 300 pT and provides nearly two orders of magnitude improvement in magnetic flux sensitivity (down to 10- 6 Phi0 / Hz1 / 2) over previous atomic probe magnetometers capable of scanning near samples. These capabilities are for the first time carefully benchmarked by imaging magnetic fields arising from microfabricated wire patterns and done so using samples that may be scanned, cryogenically cooled, and easily exchanged. We anticipate the SQCRAMscope will provide charge transport images at temperatures from room to \\x9D4K in unconventional superconductors and topologically nontrivial materials.

Air temperature gradient in large industrial hall

Science.gov (United States)

Karpuk, Michał; Pełech, Aleksander; Przydróżny, Edward; Walaszczyk, Juliusz; Szczęśniak, Sylwia

2017-11-01

In the rooms with dominant sensible heat load, volume airflow depends on many factors incl. pre-established temperature difference between exhaust and supply airflow. As the temperature difference is getting higher, airflow volume drops down, consequently, the cost of AHU is reduced. In high industrial halls with air exhaust grids located under the ceiling additional temperature gradient above working zone should be taken into consideration. In this regard, experimental research of the vertical air temperature gradient in high industrial halls were carried out for the case of mixing ventilation system The paper presents the results of air temperature distribution measurements in high technological hall (mechanically ventilated) under significant sensible heat load conditions. The supply airflow was delivered to the hall with the help of the swirl diffusers while exhaust grids were located under the hall ceiling. Basing on the air temperature distribution measurements performed on the seven pre-established levels, air temperature gradient in the area between 2.0 and 7.0 m above the floor was calculated and analysed.

A new CMOS Hall angular position sensor

Energy Technology Data Exchange (ETDEWEB)

Popovic, R.S.; Drljaca, P. [Swiss Federal Inst. of Tech., Lausanne (Switzerland); Schott, C.; Racz, R. [SENTRON AG, Zug (Switzerland)

2001-06-01

The new angular position sensor consists of a combination of a permanent magnet attached to a shaft and of a two-axis magnetic sensor. The permanent magnet produces a magnetic field parallel with the magnetic sensor plane. As the shaft rotates, the magnetic field also rotates. The magnetic sensor is an integrated combination of a CMOS Hall integrated circuit and a thin ferromagnetic disk. The CMOS part of the system contains two or more conventional Hall devices positioned under the periphery of the disk. The ferromagnetic disk converts locally a magnetic field parallel with the chip surface into a field perpendicular to the chip surface. Therefore, a conventional Hall element can detect an external magnetic field parallel with the chip surface. As the direction of the external magnetic field rotates in the chip plane, the output voltage of the Hall element varies as the cosine of the rotation angle. By placing the Hall elements at the appropriate places under the disk periphery, we may obtain the cosine signals shifted by 90 , 120 , or by any other angle. (orig.)

Scanning probe microscopy with vertically oriented cantilevers made easy

International Nuclear Information System (INIS)

Valdrè, G; Moro, D; Ulian, G

2012-01-01

Non-contact imaging in scanning probe microscopy (SPM) is becoming of great importance in particular for imaging biological matter and in general soft materials. Transverse dynamic force microscopy (TDFM) is an SPM-based methodology that exploiting a cantilever oriented in a vertical configuration with respect to the sample surface may work with very low tip to sample interaction forces. The probe is oscillated parallel to the sample surface, usually by a piezoelectric element. However, this methodology often requires complex microscope setups and detection systems, so it is usually developed in specific laboratories as a prototype microscope. Here, we present a very simple device that easily enables a commercial SPM head to be oriented in such a way to have the cantilever long axis perpendicular to the sample surface. No modifications of the SPM hardware and software are required and commercial available cantilevers can be used as probes. Performance tests using polystyrene spheres, muscovite crystallographic steps and DNA single molecules were successful and all resulted in agreement with other TDFM and SPM observations demonstrating the reliability of the device. (paper)

Time-of-flight atom-probe field-ion microscope for the study of defects in metals. Report No. 2357

International Nuclear Information System (INIS)

Hall, T.M.; Wagner, A.; Berger, A.S.; Seidman, D.N.

1975-06-01

An ultra-high vacuum time-of-flight (TOF) atom-probe field ion microscope (FIM) specifically designed for the study of defects in metals is described. The variable magnification FIM image is viewed with the aid of an internal image intensification system based on a channel electron-multiplier array. The specimen is held in a liquid-helium-cooled goniometer stage, and the specimen is exchanged by means of a high-vacuum (less than 10 -6 torr) specimen exchange device. This stage allows the specimen to be maintained at a tip temperature anywhere in the range from 13 to 450 0 K. Specimens can also be irradiated in-situ with any low-energy (less than 1 keV) gas ion employing a specially constructed ion gun. The pulse-field evaporated ions are detected by a Chevron ion-detector located 2.22 m from the FIM specimen. The TOF of the ions are measured by a specially constructed eight-channel digital timer with a resolution of +-10 ns. The entire process of applying the evaporation pulse to the specimen, measuring the dc and pulse voltages, and analyzing the TOF data is controlled by a NOVA 1220 computer. The computer is also interfaced to a Tektronix graphics terminal which displays the data in the form of a histogram of the number of events versus the mass-to-charge ratio. An extensive set of computer programs to test and operate the atom-probe FIM have been developed. With this automated system we can presently record and analyze 10 TOF s -1 . In the performance tests reported here the instrument has resolved the seven stable isotopes of molybdenum, the five stable isotopes of tungsten, and the two stable isotopes of rhenium in a tungsten--25 at. percent rhenium alloy

The quantum Hall effects: Philosophical approach

Science.gov (United States)

Lederer, P.

2015-05-01

The Quantum Hall Effects offer a rich variety of theoretical and experimental advances. They provide interesting insights on such topics as gauge invariance, strong interactions in Condensed Matter physics, emergence of new paradigms. This paper focuses on some related philosophical questions. Various brands of positivism or agnosticism are confronted with the physics of the Quantum Hall Effects. Hacking's views on Scientific Realism, Chalmers' on Non-Figurative Realism are discussed. It is argued that the difficulties with those versions of realism may be resolved within a dialectical materialist approach. The latter is argued to provide a rational approach to the phenomena, theory and ontology of the Quantum Hall Effects.

Quantum critical Hall exponents

CERN Document Server

Lütken, C A

2014-01-01

We investigate a finite size "double scaling" hypothesis using data from an experiment on a quantum Hall system with short range disorder [1-3]. For Hall bars of width w at temperature T the scaling form is w(-mu)T(-kappa), where the critical exponent mu approximate to 0.23 we extract from the data is comparable to the multi-fractal exponent alpha(0) - 2 obtained from the Chalker-Coddington (CC) model [4]. We also use the data to find the approximate location (in the resistivity plane) of seven quantum critical points, all of which closely agree with the predictions derived long ago from the modular symmetry of a toroidal sigma-model with m matter fields [5]. The value nu(8) = 2.60513 ... of the localisation exponent obtained from the m = 8 model is in excellent agreement with the best available numerical value nu(num) = 2.607 +/- 0.004 derived from the CC-model [6]. Existing experimental data appear to favour the m = 9 model, suggesting that the quantum Hall system is not in the same universality class as th...

Hall devices improve electric motor efficiency

Science.gov (United States)

Haeussermann, W.

1979-01-01

Efficiency of electric motors and generators is reduced by radial magnetic forces created by symmetric fields within device. Forces are sensed and counteracted by Hall devices on excitation or control windings. Hall generators directly measure and provide compensating control of anu asymmetry, eliminating additional measurements needed for calibration feedback control loop.

Analytical scanning evanescent microwave microscope and control stage

Science.gov (United States)

Xiang, Xiao-Dong; Gao, Chen; Duewer, Fred; Yang, Hai Tao; Lu, Yalin

2009-06-23

A scanning evanescent microwave microscope (SEMM) that uses near-field evanescent electromagnetic waves to probe sample properties is disclosed. The SEMM is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The SEMM has the ability to map dielectric constant, loss tangent, conductivity, electrical impedance, and other electrical parameters of materials. Such properties are then used to provide distance control over a wide range, from to microns to nanometers, over dielectric and conductive samples for a scanned evanescent microwave probe, which enable quantitative non-contact and submicron spatial resolution topographic and electrical impedance profiling of dielectric, nonlinear dielectric and conductive materials. The invention also allows quantitative estimation of microwave impedance using signals obtained by the scanned evanescent microwave probe and quasistatic approximation modeling. The SEMM can be used to measure electrical properties of both dielectric and electrically conducting materials.

Graphene and the universality of the quantum Hall effect

DEFF Research Database (Denmark)

Tzalenchuk, A.; Janssen, T. J.B.M.; Kazakova, O.

2013-01-01

The quantum Hall effect allows the standard for resistance to be defined in terms of the elementary charge and Planck's constant alone. The effect comprises the quantization of the Hall resistance in two-dimensional electron systems in rational fractions of RK=h/e2=25812.8074434(84) Ω (Mohr P. J....... the unconventional quantum Hall effect and then present in detail the route, which led to the most precise quantum Hall resistance universality test ever performed.......The quantum Hall effect allows the standard for resistance to be defined in terms of the elementary charge and Planck's constant alone. The effect comprises the quantization of the Hall resistance in two-dimensional electron systems in rational fractions of RK=h/e2=25812.8074434(84) Ω (Mohr P. J....... et al., Rev. Mod. Phys., 84 (2012) 1527), the resistance quantum. Despite 30 years of research into the quantum Hall effect, the level of precision necessary for metrology, a few parts per billion, has been achieved only in silicon and III-V heterostructure devices. In this lecture we show...

A cavity ring-down spectroscopy sensor for real-time Hall thruster erosion measurements

International Nuclear Information System (INIS)

Lee, B. C.; Huang, W.; Tao, L.; Yamamoto, N.; Yalin, A. P.; Gallimore, A. D.

2014-01-01

A continuous-wave cavity ring-down spectroscopy sensor for real-time measurements of sputtered boron from Hall thrusters has been developed. The sensor uses a continuous-wave frequency-quadrupled diode laser at 250 nm to probe ground state atomic boron sputtered from the boron nitride insulating channel. Validation results from a controlled setup using an ion beam and target showed good agreement with a simple finite-element model. Application of the sensor for measurements of two Hall thrusters, the H6 and SPT-70, is described. The H6 was tested at power levels ranging from 1.5 to 10 kW. Peak boron densities of 10 ± 2 × 10 14 m −3 were measured in the thruster plume, and the estimated eroded channel volume agreed within a factor of 2 of profilometry. The SPT-70 was tested at 600 and 660 W, yielding peak boron densities of 7.2 ± 1.1 × 10 14 m −3 , and the estimated erosion rate agreed within ∼20% of profilometry. Technical challenges associated with operating a high-finesse cavity in the presence of energetic plasma are also discussed

Unconventional quantum Hall effect in Floquet topological insulators

KAUST Repository

Tahir, M.

2016-07-27

We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the lights polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity αyx = 0 at zero Fermi energy, to a Hall insulator state with αyx = e2/2h. These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at (±1/2,±3/2,±5/2, ...)e2/h. © 2016 IOP Publishing Ltd Printed in the UK.

Unconventional quantum Hall effect in Floquet topological insulators

KAUST Repository

Tahir, M.; Vasilopoulos, P.; Schwingenschlö gl, Udo

2016-01-01

We study an unconventional quantum Hall effect for the surface states of ultrathin Floquet topological insulators in a perpendicular magnetic field. The resulting band structure is modified by photon dressing and the topological property is governed by the low-energy dynamics of a single surface. An exchange of symmetric and antisymmetric surface states occurs by reversing the lights polarization. We find a novel quantum Hall state in which the zeroth Landau level undergoes a phase transition from a trivial insulator state, with Hall conductivity αyx = 0 at zero Fermi energy, to a Hall insulator state with αyx = e2/2h. These findings open new possibilities for experimentally realizing nontrivial quantum states and unusual quantum Hall plateaus at (±1/2,±3/2,±5/2, ...)e2/h. © 2016 IOP Publishing Ltd Printed in the UK.

Extrinsic spin Hall effect in graphene

Science.gov (United States)

Rappoport, Tatiana

The intrinsic spin-orbit coupling in graphene is extremely weak, making it a promising spin conductor for spintronic devices. In addition, many applications also require the generation of spin currents in graphene. Theoretical predictions and recent experimental results suggest one can engineer the spin Hall effect in graphene by greatly enhancing the spin-orbit coupling in the vicinity of an impurity. The extrinsic spin Hall effect then results from the spin-dependent skew scattering of electrons by impurities in the presence of spin-orbit interaction. This effect can be used to efficiently convert charge currents into spin-polarized currents. I will discuss recent experimental results on spin Hall effect in graphene decorated with adatoms and metallic cluster and show that a large spin Hall effect can appear due to skew scattering. While this spin-orbit coupling is small if compared with what it is found in metals, the effect is strongly enhanced in the presence of resonant scattering, giving rise to robust spin Hall angles. I will present our single impurity scattering calculations done with exact partial-wave expansions and complement the analysis with numerical results from a novel real-space implementation of the Kubo formalism for tight-binding Hamiltonians. The author acknowledges the Brazilian agencies CNPq, CAPES, FAPERJ and INCT de Nanoestruturas de Carbono for financial support.

Hall current effects in dynamic magnetic reconnection solutions

International Nuclear Information System (INIS)

Craig, I.J.D.; Heerikhuisen, J.; Watson, P.G.

2003-01-01

The impact of Hall current contributions on flow driven planar magnetic merging solutions is discussed. The Hall current is important if the dimensionless Hall parameter (or normalized ion skin depth) satisfies c H >η, where η is the inverse Lundquist number for the plasma. A dynamic analysis of the problem shows, however, that the Hall current initially manifests itself, not by modifying the planar reconnection field, but by inducing a non-reconnecting perpendicular 'separator' component in the magnetic field. Only if the stronger condition c H 2 >η is satisfied can Hall currents be expected to affect the planar merging. These analytic predictions are then tested by performing a series of numerical experiments in periodic geometry, using the full system of planar magnetohydrodynamic (MHD) equations. The numerical results confirm that the nature of the merging changes dramatically when the Hall coupling satisfies c H 2 >η. In line with the analytic treatment of sheared reconnection, the coupling provided by the Hall term leads to the emergence of multiple current layers that can enhance the global Ohmic dissipation at the expense of the reconnection rate. However, the details of the dissipation depend critically on the symmetries of the simulation, and when the merging is 'head-on' (i.e., comprises fourfold symmetry) the reconnection rate can be enhanced

How can we probe the atom mass currents induced by synthetic gauge fields?

Science.gov (United States)

Paramekanti, Arun; Killi, Matthew; Trotzky, Stefan

2013-05-01

Ultracold atomic fermions and bosons in an optical lattice can have quantum ground states which support equilibrium currents in the presence of synthetic magnetic fields or spin orbit coupling. As a tool to uncover these mass currents, we propose using an anisotropic quantum quench of the optical lattice which dynamically converts the current patterns into measurable density patterns. Using analytical calculations and numerical simulations, we show that this scheme can probe diverse equilibrium bulk current patterns in Bose superfluids and Fermi fluids induced by synthetic magnetic fields, as well as detect the chiral edge currents in topological states of atomic matter such as quantum Hall and quantum spin Hall insulators. This work is supported by NSERC of Canada and the Canadian Institute for Advanced Research.

Electronic transport at semiconductor surfaces - from point-contact transistor to micro-four-point probes

DEFF Research Database (Denmark)

Hasegawa, S.; Grey, Francois

2002-01-01

show that this type of conduction is measurable using new types of experimental probes, such as the multi-tip scanning tunnelling microscope and the micro-four-point probe. The resulting electronic transport properties are intriguing, and suggest that semiconductor surfaces should be considered...

Wave Optical Calculation of Probe Size in Low Energy Scanning Electron Microscope

Czech Academy of Sciences Publication Activity Database

Radlička, Tomáš

2015-01-01

Roč. 21, S4 (2015), s. 212-217 ISSN 1431-9276 R&D Projects: GA MŠk(CZ) LO1212 Institutional support: RVO:68081731 Keywords : scanning electron microscope * optical calculation Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering Impact factor: 1.730, year: 2015

Optimization of Cylindrical Hall Thrusters

International Nuclear Information System (INIS)

Raitses, Yevgeny; Smirnov, Artem; Granstedt, Erik; Fisch, Nathaniel J.

2007-01-01

The cylindrical Hall thruster features high ionization efficiency, quiet operation, and ion acceleration in a large volume-to-surface ratio channel with performance comparable with the state-of-the-art annular Hall thrusters. These characteristics were demonstrated in low and medium power ranges. Optimization of miniaturized cylindrical thrusters led to performance improvements in the 50-200W input power range, including plume narrowing, increased thruster efficiency, reliable discharge initiation, and stable operation.

Optimization of Cylindrical Hall Thrusters

International Nuclear Information System (INIS)

Raitses, Yevgeny; Smirnov, Artem; Granstedt, Erik; Fi, Nathaniel J.

2007-01-01

The cylindrical Hall thruster features high ionization efficiency, quiet operation, and ion acceleration in a large volume-to-surface ratio channel with performance comparable with the state-of-the-art annular Hall thrusters. These characteristics were demonstrated in low and medium power ranges. Optimization of miniaturized cylindrical thrusters led to performance improvements in the 50-200W input power range, including plume narrowing, increased thruster efficiency, reliable discharge initiation, and stable operation

Mesoscopic spin Hall effect in semiconductor nanostructures

Science.gov (United States)

Zarbo, Liviu

The spin Hall effect (SHE) is a name given to a collection of diverse phenomena which share two principal features: (i) longitudinal electric current flowing through a paramagnetic semiconductor or metallic sample leads to transverse spin current and spin accumulation of opposite sign at opposing lateral edges; (ii) SHE does not require externally applied magnetic field or magnetic ordering in the equilibrium state of the sample, instead it relies on the presence of spin-orbit (SO) couplings within the sample. This thesis elaborates on a new type of phenomenon within the SHE family, predicted in our recent studies [Phys. Rev. B 72, 075361 (2005); Phys. Rev. Lett. 95, 046601 (2005); Phys. Rev. B 72, 075335 (2005); Phys. Rev. B 73 , 075303 (2006); and Europhys. Lett. 77, 47004 (2007)], where pure spin current flows through the transverse electrodes attached to a clean finitesize two-dimensional electron gas (2DEG) due to unpolarized charge current injected through its longitudinal leads. If transverse leads are removed, the effect manifests as nonequilibrium spin Hall accumulation at the lateral edges of 2DEG wires. The SO coupling driving this SHE effect is of the Rashba type, which arises due to structural inversion asymmetry of semiconductor heterostructure hosting the 2DEG. We term the effect "mesoscopic" because the spin Hall currents and accumulations reach optimal value in samples of the size of the spin precession length---the distance over which the spin of an electron precesses by an angle pi. In strongly SO-coupled structures this scale is of the order of ˜100 nm, and, therefore, mesoscopic in the sense of being much larger than the characteristic microscopic scales (such as the Fermi wavelength, screening length, or the mean free path in disordered systems), but still much smaller than the macroscopic ones. Although the first theoretical proposal for SHE, driven by asymmetry in SO-dependent scattering of spin-up and spin-down electrons off impurities

Spin-singlet hierarchy in the fractional quantum Hall effect

OpenAIRE

Ino, Kazusumi

1999-01-01

We show that the so-called permanent quantum Hall states are formed by the integer quantum Hall effects on the Haldane-Rezayi quantum Hall state. Novel conformal field theory description along with this picture is deduced. The odd denominator plateaux observed around $\

Anisotropic intrinsic spin Hall effect in quantum wires

International Nuclear Information System (INIS)

Cummings, A W; Akis, R; Ferry, D K

2011-01-01

We use numerical simulations to investigate the spin Hall effect in quantum wires in the presence of both Rashba and Dresselhaus spin-orbit coupling. We find that the intrinsic spin Hall effect is highly anisotropic with respect to the orientation of the wire, and that the nature of this anisotropy depends strongly on the electron density and the relative strengths of the Rashba and Dresselhaus spin-orbit couplings. In particular, at low densities, when only one subband of the quantum wire is occupied, the spin Hall effect is strongest for electron momentum along the [1-bar 10] axis, which is the opposite of what is expected for the purely 2D case. In addition, when more than one subband is occupied, the strength and anisotropy of the spin Hall effect can vary greatly over relatively small changes in electron density, which makes it difficult to predict which wire orientation will maximize the strength of the spin Hall effect. These results help to illuminate the role of quantum confinement in spin-orbit-coupled systems, and can serve as a guide for future experimental work on the use of quantum wires for spin-Hall-based spintronic applications. (paper)

Atomic Force Microscope for Imaging and Spectroscopy

Science.gov (United States)

Pike, W. T.; Hecht, M. H.; Anderson, M. S.; Akiyama, T.; Gautsch, S.; deRooij, N. F.; Staufer, U.; Niedermann, Ph.; Howald, L.; Mueller, D.

2000-01-01

We have developed, built, and tested an atomic force microscope (AFM) for extraterrestrial applications incorporating a micromachined tip array to allow for probe replacement. It is part of a microscopy station originally intended for NASA's 2001 Mars lander to identify the size, distribution, and shape of Martian dust and soil particles. As well as imaging topographically down to nanometer resolution, this instrument can be used to reveal chemical information and perform infrared and Raman spectroscopy at unprecedented resolution.

The Hall module of an exact category with duality

OpenAIRE

Young, Matthew B.

2012-01-01

We construct from a finitary exact category with duality a module over its Hall algebra, called the Hall module, encoding the first order self-dual extension structure of the category. We study in detail Hall modules arising from the representation theory of a quiver with involution. In this case we show that the Hall module is naturally a module over the specialized reduced sigma-analogue of the quantum Kac-Moody algebra attached to the quiver. For finite type quivers, we explicitly determin...

Theory of spin Hall effect

OpenAIRE

Chudnovsky, Eugene M.

2007-01-01

An extension of Drude model is proposed that accounts for spin and spin-orbit interaction of charge carriers. Spin currents appear due to combined action of the external electric field, crystal field and scattering of charge carriers. The expression for spin Hall conductivity is derived for metals and semiconductors that is independent of the scattering mechanism. In cubic metals, spin Hall conductivity $\\sigma_s$ and charge conductivity $\\sigma_c$ are related through $\\sigma_s = [2 \\pi \\hbar...

Anode sheath in Hall thrusters

International Nuclear Information System (INIS)

Dorf, L.; Semenov, V.; Raitses, Y.

2003-01-01

A set of hydrodynamic equations is used to describe quasineutral plasma in ionization and acceleration regions of a Hall thruster. The electron distribution function and Poisson equation are invoked for description of a near-anode region. Numerical solutions suggest that steady-state operation of a Hall thruster can be achieved at different anode sheath regimes. It is shown that the anode sheath depends on the thruster operating conditions, namely the discharge voltage and the mass flow rate

Quantum Hall effect in quantum electrodynamics

International Nuclear Information System (INIS)

Penin, Alexander A.

2009-01-01

We consider the quantum Hall effect in quantum electrodynamics and find a deviation from the quantum-mechanical prediction for the Hall conductivity due to radiative antiscreening of electric charge in an external magnetic field. A weak dependence of the universal von Klitzing constant on the magnetic field strength, which can possibly be observed in a dedicated experiment, is predicted

Quantized Hall conductance as a topological invariant

International Nuclear Information System (INIS)

Niu, Q.; Thouless, Ds.J.; Wu, Y.S.

1984-10-01

Whenever the Fermi level lies in a gap (or mobility gap) the bulk Hall conductance can be expressed in a topologically invariant form showing the quantization explicitly. The new formulation generalizes the earlier result by TKNN to the situation where many body interaction and substrate disorder are also present. When applying to the fractional quantized Hall effect we draw the conclusion that there must be a symmetry breaking in the many body ground state. The possibility of writing the fractionally quantized Hall conductance as a topological invariant is also carefully discussed. 19 references

Commemorative Symposium on the Hall Effect and its Applications

CERN Document Server

Westgate, C

1980-01-01

In 1879, while a graduate student under Henry Rowland at the Physics Department of The Johns Hopkins University, Edwin Herbert Hall discovered what is now universally known as the Hall effect. A symposium was held at The Johns Hopkins University on November 13, 1979 to commemorate the lOOth anniversary of the discovery. Over 170 participants attended the symposium which included eleven in­ vited lectures and three speeches during the luncheon. During the past one hundred years, we have witnessed ever ex­ panding activities in the field of the Hall effect. The Hall effect is now an indispensable tool in the studies of many branches of condensed matter physics, especially in metals, semiconductors, and magnetic solids. Various components (over 200 million!) that utilize the Hall effect have been successfully incorporated into such devices as keyboards, automobile ignitions, gaussmeters, and satellites. This volume attempts to capture the important aspects of the Hall effect and its applications. It includes t...

Study of defects and radiation damage in solids by field-ion and atom-probe microscopy

International Nuclear Information System (INIS)

Seidman, D.N.

1982-01-01

An attempt is made to introduce the reader to the basic physical ideas involved in the field-ion and atom-probe field-ion microscope techniques, and to the applications of these techniques to the study of defects and radiation damage in solids. The final section discusses, in precise form, the application of the atom-probe field-ion microscope to the study of the behavior of implanted 3 He and 4 He atoms in tungsten. The paper is heavily referenced so that the reader can pursue his specific research interest in detail

Nanoscale microwave microscopy using shielded cantilever probes

KAUST Repository

Lai, Keji; Kundhikanjana, Worasom; Kelly, Michael A.; Shen, Zhi-Xun

2011-01-01

Quantitative dielectric and conductivity mapping in the nanoscale is highly desirable for many research disciplines, but difficult to achieve through conventional transport or established microscopy techniques. Taking advantage of the micro-fabrication technology, we have developed cantilever-based near-field microwave probes with shielded structures. Sensitive microwave electronics and finite-element analysis modeling are also utilized for quantitative electrical imaging. The system is fully compatible with atomic force microscope platforms for convenient operation and easy integration of other modes and functions. The microscope is ideal for interdisciplinary research, with demonstrated examples in nano electronics, physics, material science, and biology.

Nanoscale microwave microscopy using shielded cantilever probes

KAUST Repository

Lai, Keji

2011-04-21

Quantitative dielectric and conductivity mapping in the nanoscale is highly desirable for many research disciplines, but difficult to achieve through conventional transport or established microscopy techniques. Taking advantage of the micro-fabrication technology, we have developed cantilever-based near-field microwave probes with shielded structures. Sensitive microwave electronics and finite-element analysis modeling are also utilized for quantitative electrical imaging. The system is fully compatible with atomic force microscope platforms for convenient operation and easy integration of other modes and functions. The microscope is ideal for interdisciplinary research, with demonstrated examples in nano electronics, physics, material science, and biology.

Halls Lake 1990

Data.gov (United States)

National Oceanic and Atmospheric Administration, Department of Commerce — Salt marsh habitats along the shoreline of Halls Lake are threatened by wave erosion, but the reconstruction of barrier islands to reduce this erosion will modify or...

Nobel Prize in physics 1985: Quantum Hall effect

International Nuclear Information System (INIS)

Herrmann, R.

1986-01-01

The conditions (like very strong magnetic fields, ultralow temperatures, and occurrence of a two-dimensional electron gas in microelectronic structures) for the measurement of the quantum Hall effect are explained. Two possible measuring methods are described. Measuring results for p-Si-MOSFET, GaAs/AlGaAs heterojuntions and grain boundaries in InSb crystals are reported. Differences between normal (integer) and fractional quantum Hall effect are discussed. One of the important consequences is that by means of the quantum Hall effect the value h/e 2 can be determined with very high accuracy. In 1985 Klaus von Klitzing was awarded the Nobel Prize for his work on the quantum Hall effect

RTSPM: real-time Linux control software for scanning probe microscopy.

Science.gov (United States)

Chandrasekhar, V; Mehta, M M

2013-01-01

Real time computer control is an essential feature of scanning probe microscopes, which have become important tools for the characterization and investigation of nanometer scale samples. Most commercial (and some open-source) scanning probe data acquisition software uses digital signal processors to handle the real time data processing and control, which adds to the expense and complexity of the control software. We describe here scan control software that uses a single computer and a data acquisition card to acquire scan data. The computer runs an open-source real time Linux kernel, which permits fast acquisition and control while maintaining a responsive graphical user interface. Images from a simulated tuning-fork based microscope as well as a standard topographical sample are also presented, showing some of the capabilities of the software.

Optical Diagnostic Characterization of High-Power Hall Thruster Wear and Operation

Science.gov (United States)

Williams, George J., Jr.; Soulas, George C.; Kamhawi, Hani

2012-01-01

Optical emission spectroscopy is employed to correlate BN insulator erosion with high-power Hall thruster operation. Specifically, actinometry leveraging excited xenon states is used to normalize the emission spectra of ground state boron as a function of thruster operating condition. Trends in the strength of the boron signal are correlated with thruster power, discharge voltage, and discharge current. In addition, the technique is demonstrated on metallic coupons embedded in the walls of the HiVHAc EM thruster. The OES technique captured the overall trend in the erosion of the coupons which boosts credibility in the method since there are no data to which to calibrate the erosion rates of high-power Hall thrusters. The boron signals are shown to trend linearly with discharge voltage for a fixed discharge current as expected. However, the boron signals of the higher-power NASA 300M and NASA 457Mv2 trend with discharge current and show an unexpectedly weak to inverse dependence on discharge voltage. Electron temperatures measured optically in the near-field plume of the thruster agree well with Langmuir probe data. However, the optical technique used to determine Te showed unacceptable sensitivity to the emission intensities. Near-field, single-frequency imaging of the xenon neutrals is also presented as a function of operating condition for the NASA 457 Mv2.

AC conductivity of a quantum Hall line junction

International Nuclear Information System (INIS)

Agarwal, Amit; Sen, Diptiman

2009-01-01

We present a microscopic model for calculating the AC conductivity of a finite length line junction made up of two counter- or co-propagating single mode quantum Hall edges with possibly different filling fractions. The effect of density-density interactions and a local tunneling conductance (σ) between the two edges is considered. Assuming that σ is independent of the frequency ω, we derive expressions for the AC conductivity as a function of ω, the length of the line junction and other parameters of the system. We reproduce the results of Sen and Agarwal (2008 Phys. Rev. B 78 085430) in the DC limit (ω→0), and generalize those results for an interacting system. As a function of ω, the AC conductivity shows significant oscillations if σ is small; the oscillations become less prominent as σ increases. A renormalization group analysis shows that the system may be in a metallic or an insulating phase depending on the strength of the interactions. We discuss the experimental implications of this for the behavior of the AC conductivity at low temperatures.

Sensitivity of resistive and Hall measurements to local inhomogeneities

DEFF Research Database (Denmark)

Koon, Daniel W.; Wang, Fei; Petersen, Dirch Hjorth

2013-01-01

We derive exact, analytic expressions for the sensitivity of resistive and Hall measurements to local inhomogeneities in a specimen's material properties in the combined linear limit of a weak perturbation over an infinitesimal area in a small magnetic field. We apply these expressions both to four-point...... probe measurements on an infinite plane and to symmetric, circular van der Pauw discs, obtaining functions consistent with published results. These new expressions speed up calculation of the sensitivity for a specimen of arbitrary shape to little more than the solution of two Laplace equation boundary......-value problems of the order of N3 calculations, rather than N2 problems of total order N5, and in a few cases produces an analytic expression for the sensitivity. These functions provide an intuitive, visual explanation of how, for example, measurements can predict the wrong carrier type in n-type ZnO....

Intrinsic superspin Hall current

Science.gov (United States)

Linder, Jacob; Amundsen, Morten; Risinggârd, Vetle

2017-09-01

We discover an intrinsic superspin Hall current: an injected charge supercurrent in a Josephson junction containing heavy normal metals and a ferromagnet generates a transverse spin supercurrent. There is no accompanying dissipation of energy, in contrast to the conventional spin Hall effect. The physical origin of the effect is an antisymmetric spin density induced among transverse modes ky near the interface of the superconductor arising due to the coexistence of p -wave and conventional s -wave superconducting correlations with a belonging phase mismatch. Our predictions can be tested in hybrid structures including thin heavy metal layers combined with strong ferromagnets and ordinary s -wave superconductors.

Time and angle resolved phonon absorption in the fractional quantum hall regime

International Nuclear Information System (INIS)

Devitt, A.M.

2000-09-01

The work described in this thesis is a study of the phonon absorption by a two-dimensional electron system (2DES) in the fractional quantum Hall regime and also at ν = 1/2. The fractional quantum Hall effect arises in 2DES's in high magnetic fields and is characterised by the quantisation of the transverse or Hall resistance and the vanishing longitudinal conductivity. The filling factor denotes the number of filled Landau levels and the quantum Hall effect occurs when this ratio is at certain rational odd denominator filling factors. The phenomenology of the effect arises due to the existence of an energy gap between the ground state and the lowest excited state. This energy gap is characterised by a deep minimum, or minima, at finite in-plane wavevector. Acoustic phonon absorption is expected to probe the energy gap at wavevectors close to or at the minimum in the dispersion curve. The experiments reported here incorporate the use of a thin film heater to produce a pulse of phonons of which a fraction are absorbed by the 2DES. A fast amplifier and signal averaging board enable detection of small signals due to absorption of phonons. The technique used allows time resolution of the phonon signal which typically takes place over a period of 10 μs or so. The time resolution enables different phonon modes to be studied. By altering the position of the heater relative to the 2DES angular resolution is also possible. The phonon absorption at several different filling factors has been investigated and the energy gaps found are in reasonable agreement with theoretical predictions. The absorption at ν 1/2 has also been investigated. Here the composite fermions are expected to have a well defined Fermi wavevector. The absorption at ν = 1/2 and the fractional quantum Hall states is found to be qualitatively and quantitatively different. We see that the change in electron temperature atν = 1/2 is much less than at ν = 1/3 due to the larger heat capacity. At ν = 1

The quantum Hall's effect: A quantum electrodynamic phenomenon

International Nuclear Information System (INIS)

Arbab, A. I.

2012-01-01

We have applied Maxwell's equations to study the physics of quantum Hall's effect. The electromagnetic properties of this system are obtained. The Hall's voltage, V H = 2πħ 2 n s /em, where n s is the electron number density, for a 2-dimensional system, and h = 2πħ is the Planck's constant, is found to coincide with the voltage drop across the quantum capacitor. Consideration of the cyclotronic motion of electrons is found to give rise to Hall's resistance. Ohmic resistances in the horizontal and vertical directions have been found to exist before equilibrium state is reached. At a fundamental level, the Hall's effect is found to be equivalent to a resonant LCR circuit with L H = 2π m/e 2 n s and C H = me 2 /2πħ 2 n s satisfying the resonance condition with resonant frequency equal to the inverse of the scattering (relaxation) time, τ s . The Hall's resistance is found to be R H = √L H /C H . The Hall's resistance may be connected with the impedance that the electron wave experiences when it propagates in the 2-dimensional gas. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Thermal diffusivity imaging with the thermal lens microscope.

Science.gov (United States)

Dada, Oluwatosin O; Feist, Peter E; Dovichi, Norman J

2011-12-01

A coaxial thermal lens microscope was used to generate images based on both the absorbance and thermal diffusivity of histological samples. A pump beam was modulated at frequencies ranging from 50 kHz to 5 MHz using an acousto-optic modulator. The pump and a CW probe beam were combined with a dichroic mirror, directed into an inverted microscope, and focused onto the specimen. The change in the transmitted probe beam's center intensity was detected with a photodiode. The photodiode's signal and a reference signal from the modulator were sent to a high-speed lock-in amplifier. The in-phase and quadrature signals were recorded as a sample was translated through the focused beams and used to generate images based on the amplitude and phase of the lock-in amplifier's signal. The amplitude is related to the absorbance and the phase is related to the thermal diffusivity of the sample. Thin sections of stained liver and bone tissues were imaged; the contrast and signal-to-noise ratio of the phase image was highest at frequencies from 0.1-1 MHz and dropped at higher frequencies. The spatial resolution was 2.5 μm for both amplitude and phase images, limited by the pump beam spot size. © 2011 Optical Society of America

Path-separated electron interferometry in a scanning transmission electron microscope

Science.gov (United States)

Yasin, Fehmi S.; Harvey, Tyler R.; Chess, Jordan J.; Pierce, Jordan S.; McMorran, Benjamin J.

2018-05-01

We report a path-separated electron interferometer within a scanning transmission electron microscope. In this setup, we use a nanofabricated grating as an amplitude-division beamsplitter to prepare multiple spatially separated, coherent electron probe beams. We achieve path separations of 30 nm. We pass the  +1 diffraction order probe through amorphous carbon while passing the 0th and  ‑1 orders through vacuum. The probes are then made to interfere via imaging optics, and we observe an interference pattern at the CCD detector with up to 39.7% fringe visibility. We show preliminary experimental results in which the interference pattern was recorded during a 1D scan of the diffracted probes across a test phase object. These results qualitatively agree with a modeled interference predicted by an independent measurement of the specimen thickness. This experimental design can potentially be applied to phase contrast imaging and fundamental physics experiments, such as an exploration of electron wave packet coherence length.

Effects of facility backpressure on the performance and plume of a Hall thruster

Science.gov (United States)

Walker, Mitchell Louis Ronald

2005-07-01

This dissertation presents research aimed at understanding the relationship between facility background pressure, Hall thruster performance, and plume characteristics. Due to the wide range of facilities used in Hall thruster testing, it is difficult for researchers to make adequate comparisons between data sets because of both dissimilar instrumentation and backpressures. The differences in the data sets are due to the ingestion of background gas into the Hall thruster discharge channel and charge-exchange collisions in the plume. Thus, this research aims to understand facility effects and to develop the tools needed to allow researchers to obtain relevant plume and performance data for a variety of chambers and backpressures. The first portion of this work develops a technique for calibrating a vacuum chamber in terms of pressure to account for elevated backpressures while testing Hall thrusters. Neutral gas background pressure maps of the Large Vacuum Test Facility are created at a series of cold anode flow rates and one hot flow rate at two UM/AFRL P5 5 kW Hall thruster operating conditions. These data show that a cold flow pressure map can be used to approximate the neutral background pressure in the chamber with the thruster in operation. In addition, the data are used to calibrate a numerical model that accurately predicts facility backpressure within a vacuum chamber of specified geometry and pumping speed. The second portion of this work investigates how facility backpressure influences the plume, plume diagnostics, and performance of the P5 Hall thruster. Measurements of the plume and performance characteristics over a wide range of pressures show that ingestion, a decrease in the downstream plasma potential, and broadening of the ion energy distribution function cause the increase in thrust with backpressure. Furthermore, a magnetically-filtered Faraday probe accurately measures ion current density at elevated operating pressures. The third portion of

Spontaneous Hall effect in a chiral p-wave superconductor

Science.gov (United States)

Furusaki, Akira; Matsumoto, Masashige; Sigrist, Manfred

2001-08-01

In a chiral superconductor with broken time-reversal symmetry a ``spontaneous Hall effect'' may be observed. We analyze this phenomenon by taking into account the surface properties of a chiral superconductor. We identify two main contributions to the spontaneous Hall effect. One contribution originates from the Bernoulli (or Lorentz) force due to spontaneous currents running along the surfaces of the superconductor. The other contribution has a topological origin and is related to the intrinsic angular momentum of Cooper pairs. The latter can be described in terms of a Chern-Simons-like term in the low-energy field theory of the superconductor and has some similarities with the quantum Hall effect. The spontaneous Hall effect in a chiral superconductor is, however, nonuniversal. Our analysis is based on three approaches to the problem: a self-consistent solution of the Bogoliubov-de Gennes equation, a generalized Ginzburg-Landau theory, and a hydrodynamic formulation. All three methods consistently lead to the same conclusion that the spontaneous Hall resistance of a two-dimensional superconducting Hall bar is of order h/(ekFλ)2, where kF is the Fermi wave vector and λ is the London penetration depth; the Hall resistance is substantially suppressed from a quantum unit of resistance. Experimental issues in measuring this effect are briefly discussed.

The magnetic flux leakage measurement by the hall sensor in the longitudinal magnetic field

International Nuclear Information System (INIS)

Joo, Gwang Tae; Son, Dae Rok; Han, Jung Hee; Park, Jae Hyung

1998-01-01

This paper is concerned with magnetic leakage flux measurement using by the hall sensor in the longitudinal magnetic field of the feromagnetic specimen. For detection sensitivity by the hall probe according to various depth of the subsurface defects, the specimen are prepared by six drilled holes of 0.5 mm φ from 1 mm depth to 4 mm depth in the carbon steel plate(10 x 35 x 265 mm). When the specimen applied by various frequency(2 - 9 Hz) of the AC through synthesizer and power amplifier in the yoke, the signals of the magnetic flux leakage using lack-in amplifier and synthesizer are decreased linearly with defect depth at 2 Hz, but these signals are decreased suddenly with defect depth from the surface and obscured with increasing frequency. And, when the specimen applied range of 1 Amp. to 5 Amp. by DC power supply in the yoke, the signals of the magnetic flux leakage through DVM decreased linearly with defect depth up to 2.5 mm depth and change slightly defect depth above 2.5 mm depth from the surface, but its signals appeared predominately.

Fabrication and buckling dynamics of nanoneedle AFM probes

Energy Technology Data Exchange (ETDEWEB)

Beard, J D; Gordeev, S N, E-mail: jdb28@bath.ac.uk [Department of Physics, University of Bath, Claverton Down, Bath BA2 7AY (United Kingdom)

2011-04-29

A new method for the fabrication of high-aspect-ratio probes by electron beam induced deposition is described. This technique allows the fabrication of cylindrical 'nanoneedle' structures on the atomic force microscope (AFM) probe tip which can be used for accurate imaging of surfaces with high steep features. Scanning electron microscope (SEM) imaging showed that needles with diameters in the range of 18-100 nm could be obtained by this technique. The needles were shown to undergo buckling deformation under large tip-sample forces. The deformation was observed to recover elastically under vertical deformations of up to {approx} 60% of the needle length, preventing damage to the needle. A technique of stabilizing the needle against buckling by coating it with additional electron beam deposited carbon was also investigated; it was shown that coated needles of 75 nm or greater total diameter did not buckle even under tip-sample forces of {approx} 1.5 {mu}N.

Anomalous Hall effect in Fe/Gd bilayers

KAUST Repository

Xu, W. J.; Zhang, Bei; Liu, Z. X.; Wang, Z.; Li, W.; Wu, Z. B.; Yu, R. H.; Zhang, Xixiang

2010-01-01

Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010

Anomalous Hall effect in Fe/Gd bilayers

KAUST Repository

Xu, W. J.

2010-04-01

Non-monotonic dependence of anomalous Hall resistivity on temperature and magnetization, including a sign change, was observed in Fe/Gd bilayers. To understand the intriguing observations, we fabricated the Fe/Gd bilayers and single layers of Fe and Gd simultaneously. The temperature and field dependences of longitudinal resistivity, Hall resistivity and magnetization in these films have also been carefully measured. The analysis of these data reveals that these intriguing features are due to the opposite signs of Hall resistivity/or spin polarization and different Curie temperatures of Fe and Gd single-layer films. Copyright (C) EPLA, 2010

Anomalous Hall effect

Czech Academy of Sciences Publication Activity Database

Nagaosa, N.; Sinova, Jairo; Onoda, S.; MacDonald, A. H.; Ong, N. P.

2010-01-01

Roč. 82, č. 2 (2010), s. 1539-1592 ISSN 0034-6861 Institutional research plan: CEZ:AV0Z10100521 Keywords : anomalous Hall effect * spintronics Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 51.695, year: 2010

Hall effect in a strong magnetic field: Direct comparisons of compressible magnetohydrodynamics and the reduced Hall magnetohydrodynamic equations

International Nuclear Information System (INIS)

Martin, L. N.; Dmitruk, P.; Gomez, D. O.

2010-01-01

In this work we numerically test a model of Hall magnetohydrodynamics in the presence of a strong mean magnetic field: the reduced Hall magnetohydrodynamic model (RHMHD) derived by [Gomez et al., Phys. Plasmas 15, 102303 (2008)] with the addition of weak compressible effects. The main advantage of this model lies in the reduction of computational cost. Nevertheless, up until now the degree of agreement with the original Hall MHD system and the range of validity in a regime of turbulence were not established. In this work direct numerical simulations of three-dimensional Hall MHD turbulence in the presence of a strong mean magnetic field are compared with simulations of the weak compressible RHMHD model. The results show that the degree of agreement is very high (when the different assumptions of RHMHD, such as spectral anisotropy, are satisfied). Nevertheless, when the initial conditions are isotropic but the mean magnetic field is maintained strong, the results differ at the beginning but asymptotically reach a good agreement at relatively short times. We also found evidence that the compressibility still plays a role in the dynamics of these systems, and the weak compressible RHMHD model is able to capture these effects. In conclusion the weak compressible RHMHD model is a valid approximation of the Hall MHD turbulence in the relevant physical context.

Measured Early Lateral Energy Fractions in Concert Halls and Opera Houses

Science.gov (United States)

BARRON, M.

2000-04-01

In the 30 years since early lateral reflections were first suggested as important for concert halls, spatial impression and source broadening have become almost universally accepted as essential characteristics of halls with good acoustics. Two objective measures of source broadening have been proposed. Measured values of the best defined of these measures, the early lateral energy fraction (LF), are considered here. Results from two independent measurement surveys are discussed. Comparisons of LF values by hall show a significant link between hall mean LF and hall width. There is however considerable overlap between measured LF values in different halls so the relevance of describing halls by their mean early lateral energy fraction values is questionable. The behaviour of LF values within auditoria is discussed for different concert hall plan forms and within opera houses. A measure of source broadening including sound level is proposed and results considered in the context of auditorium design.

Destruction of the fractional quantum Hall effect by disorder

International Nuclear Information System (INIS)

Laughlin, R.B.

1985-07-01

It is suggested that Hall steps in the fractional quantum Hall effect are physically similar to those in the ordinary quantum Hall effect. This proposition leads to a simple scaling diagram containing a new type of fixed point, which is identified with the destruction of the fractional states by disorder. 15 refs., 3 figs

Intrinsic quantum spin Hall and anomalous Hall effects in h-Sb/Bi epitaxial growth on a ferromagnetic MnO2 thin film.

Science.gov (United States)

Zhou, Jian; Sun, Qiang; Wang, Qian; Kawazoe, Yoshiyuki; Jena, Puru

2016-06-07

Exploring a two-dimensional intrinsic quantum spin Hall state with a large band gap as well as an anomalous Hall state in realizable materials is one of the most fundamental and important goals for future applications in spintronics, valleytronics, and quantum computing. Here, by combining first-principles calculations with a tight-binding model, we predict that Sb or Bi can epitaxially grow on a stable and ferromagnetic MnO2 thin film substrate, forming a flat honeycomb sheet. The flatness of Sb or Bi provides an opportunity for the existence of Dirac points in the Brillouin zone, with its position effectively tuned by surface hydrogenation. The Dirac points in spin up and spin down channels split due to the proximity effects induced by MnO2. In the presence of both intrinsic and Rashba spin-orbit coupling, we find two band gaps exhibiting a large band gap quantum spin Hall state and a nearly quantized anomalous Hall state which can be tuned by adjusting the Fermi level. Our findings provide an efficient way to realize both quantized intrinsic spin Hall conductivity and anomalous Hall conductivity in a single material.

Semi-inclusive DIS Experiments Using Transversely Polarized Targets in Hall-A: Current Results and Future Plans

Directory of Open Access Journals (Sweden)

Allada Kalyan

2012-12-01

Full Text Available Measurement of single (SSA and double spin asymmetries (DSA in semiinclusive DIS reactions using polarized targets provide a powerful method to probe transverse momentum dependent parton distribution functions (TMDs. In particular, the experimentally measured SSA on nucleon targets can help in extracting the transversity and Sivers distribution functions of u and d-quarks. Similarly, the measured DSA are sensitive to the quark spin-orbital correlations, and provide an access to the TMD parton distribution function (g1T. A recent experiment conducted in Hall-A Jefferson Lab using transversely polarized 3He provide first such measurements on “effective” neutron target. The measurement was performed using 5.9 GeV beam from CEBAF and measured the target SSA/DSA in the SIDIS reaction 3He↑(e, e′π±X. The kinematical range, x = 0.19 ~ 0.34, at Q2 = 1.77 ~ 2.73 (GeV/c2, was focused on the valence quark region. The results from this measurement along with our plans for future high precision measurements in Hall-A are presented.

Signal conditioning and processing for metallic Hall sensors.

Czech Academy of Sciences Publication Activity Database

Entler, Slavomír; Ďuran, Ivan; Sládek, P.; Vayakis, G.; Kočan, M.

2017-01-01

Roč. 123, November (2017), s. 783-786 ISSN 0920-3796. [SOFT 2016: Symposium on Fusion Technology /29./. Prague, 05.09.2016-09.09.2016] R&D Projects: GA MŠk LG14002 Institutional support: RVO:61389021 Keywords : Hall sensor * Lock-in * Synchronous detection * Current spinning * Hall effect * Planar hall effect suppression Subject RIV: JF - Nuclear Energetics OBOR OECD: Nuclear related engineering Impact factor: 1.319, year: 2016 http://www.sciencedirect.com/science/article/pii/S0920379617305070

Use of XPS to clarify the Hall coefficient sign variation in thin niobium layers buried in silicon

Energy Technology Data Exchange (ETDEWEB)

Demchenko, Iraida N., E-mail: demch@ifpan.edu.pl [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw (Poland); Lisowski, Wojciech [Institute of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw (Poland); Syryanyy, Yevgen [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw (Poland); Melikhov, Yevgen [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw (Poland); School of Engineering, Cardiff University, Newport Rd., Cardiff, CF24 3AA (United Kingdom); Zaytseva, Iryna; Konstantynov, Pavlo [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw (Poland); Chernyshova, Maryna [Institute of Plasma Physics and Laser Microfusion, Hery Street 23, 01-497 Warsaw (Poland); Cieplak, Marta Z. [Institute of Physics, Polish Academy of Sciences, Aleja Lotnikow 32/46, PL-02668 Warsaw (Poland)

2017-03-31

Highlights: • HR XPS spectra of Nb 3d, Si 2p, O 1s were probed for Si/Nb/Si trilayers prepared by magnetron sputtering to clarify the Hall coefficient variation as a function of Nb layer thickness. • Strong boundary scattering, enhanced by the presence of silicon ions in the layer close to the interface/s is a main factor leading to sign change of the Hall coefficient. • Theoretical concentration/depth profile as a function of sputtering determined by SESSA after optimization of the model system gives good agreement with experiment. - Abstract: Si/Nb/Si trilayers formed with 9.5 and 1.3 nm thick niobium layer buried in amorphous silicon were prepared by magnetron sputtering and studied using XPS depth-profile techniques in order to investigate the change of Hall coefficient sign with thickness. The analysis of high-resolution (HR) XPS spectra revealed that the thicker layer sample has sharp top interface and metallic phase of niobium, thus holes dominate the transport. In contrast, the analysis indicates that the thinner layer sample has a Nb-rich mixed alloy formation at the top interface. The authors suggest that the main effect leading to a change of sign of the Hall coefficient for the thinner layer sample (which is negative contrary to the positive sign for the thicker layer sample) may be related to strong boundary scattering enhanced by the presence of silicon ions in the layer close to the interface/s. The depth-profile reconstruction was performed by SESSA software tool confirming that it can be reliably used for quantitative analysis/interpretation of experimental XPS data.

Energy spectrum, dissipation, and spatial structures in reduced Hall magnetohydrodynamic

Energy Technology Data Exchange (ETDEWEB)

Martin, L. N.; Dmitruk, P. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Gomez, D. O. [Departamento de Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and IFIBA, CONICET, Ciudad Universitaria, 1428 Buenos Aires (Argentina); Instituto de Astronomia y Fisica del Espacio, CONICET, Buenos Aires (Argentina)

2012-05-15

We analyze the effect of the Hall term in the magnetohydrodynamic turbulence under a strong externally supported magnetic field, seeing how this changes the energy cascade, the characteristic scales of the flow, and the dynamics of global magnitudes, with particular interest in the dissipation. Numerical simulations of freely evolving three-dimensional reduced magnetohydrodynamics are performed, for different values of the Hall parameter (the ratio of the ion skin depth to the macroscopic scale of the turbulence) controlling the impact of the Hall term. The Hall effect modifies the transfer of energy across scales, slowing down the transfer of energy from the large scales up to the Hall scale (ion skin depth) and carrying faster the energy from the Hall scale to smaller scales. The final outcome is an effective shift of the dissipation scale to larger scales but also a development of smaller scales. Current sheets (fundamental structures for energy dissipation) are affected in two ways by increasing the Hall effect, with a widening but at the same time generating an internal structure within them. In the case where the Hall term is sufficiently intense, the current sheet is fully delocalized. The effect appears to reduce impulsive effects in the flow, making it less intermittent.

Spin disorder effect in anomalous Hall effect in MnGa

Science.gov (United States)

Mendonça, A. P. A.; Varalda, J.; Schreiner, W. H.; Mosca, D. H.

2017-12-01

We report on resistivity and Hall effect in MnGa thin films grown by molecular beam epitaxy on GaAs substrates. Highly (1 1 1)-textured MnGa film with L10 structure exhibits hard magnetic properties with coercivities as high as 20 kOe and spin disorder mechanisms contributing to the Hall conductivity at room temperature. Density functional theory calculations were performed to determine the intrinsic Berry curvature in the momentum space with chiral spin structure that results in an anomalous Hall conductivity of 127 (Ωcm)-1 comparable to that measured at low temperature. In addition to residual and side-jump contributions, which are enhanced by thermal activation, both anomalous Hall conductivity and Hall angle increase between 100 K and room temperature. The present results reinforce the potential of Mn-Ga system for developing Hall effect-based spintronic devices.

L'effet Hall Quantique

Science.gov (United States)

Samson, Thomas

Nous proposons une methode permettant d'obtenir une expression pour la conductivite de Hall de structures electroniques bidimensionnelles et nous examinons celle -ci a la limite d'une temperature nulle dans le but de verifier l'effet Hall quantique. Nous allons nous interesser essentiellement a l'effet Hall quantique entier et aux effets fractionnaires inferieurs a un. Le systeme considere est forme d'un gaz d'electrons en interaction faible avec les impuretes de l'echantillon. Le modele du gaz d'electrons consiste en un gaz bidimensionnel d'electrons sans spin expose perpendiculairement a un champ magnetique uniforme. Ce dernier est decrit par le potentiel vecteur vec{rm A} defini dans la jauge de Dingle ou jauge symetrique. Conformement au formalisme de la seconde quantification, l'hamiltonien de ce gaz est represente dans la base des etats a un-corps de Dingle |n,m> et exprime ainsi en terme des operateurs de creation et d'annihilation correspondants a_sp{ rm n m}{dag} et a _{rm n m}. Nous supposons de plus que les electrons du niveau fondamental de Dingle interagissent entre eux via le potentiel coulombien. La methode utilisee fait appel a une equation mai tresse a N-corps, de nature quantique et statistique, et verifiant le second principe de la thermodynamique. A partir de celle-ci, nous obtenons un systeme d'equations differentielles appele hierarchie d'equations quantique dont la resolution nous permet de determiner une equation a un-corps, dite de Boltzmann quantique, et dictant l'evolution de la moyenne statistique de l'operateur non-diagonal a _sp{rm n m}{dag } a_{rm n}, _{rm m}, sous l'action du champ electrique applique vec{rm E}(t). C'est sa solution Tr(p(t) a _sp{rm n m}{dag} a_{rm n},_ {rm m}), qui definit la relation de convolution entre la densite courant de Hall vec{rm J}_{rm H }(t) et le champ electrique vec {rm E}(t) dont la transformee de Laplace-Fourier du noyau nous fournit l'expression de la conductivite de Hall desiree. Pour une valeur de

Improved analysis techniques for cylindrical and spherical double probes

Energy Technology Data Exchange (ETDEWEB)

Beal, Brian; Brown, Daniel; Bromaghim, Daron [Air Force Research Laboratory, 1 Ara Rd., Edwards Air Force Base, California 93524 (United States); Johnson, Lee [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, California 91109 (United States); Blakely, Joseph [ERC Inc., 1 Ara Rd., Edwards Air Force Base, California 93524 (United States)

2012-07-15

A versatile double Langmuir probe technique has been developed by incorporating analytical fits to Laframboise's numerical results for ion current collection by biased electrodes of various sizes relative to the local electron Debye length. Application of these fits to the double probe circuit has produced a set of coupled equations that express the potential of each electrode relative to the plasma potential as well as the resulting probe current as a function of applied probe voltage. These equations can be readily solved via standard numerical techniques in order to determine electron temperature and plasma density from probe current and voltage measurements. Because this method self-consistently accounts for the effects of sheath expansion, it can be readily applied to plasmas with a wide range of densities and low ion temperature (T{sub i}/T{sub e} Much-Less-Than 1) without requiring probe dimensions to be asymptotically large or small with respect to the electron Debye length. The presented approach has been successfully applied to experimental measurements obtained in the plume of a low-power Hall thruster, which produced a quasineutral, flowing xenon plasma during operation at 200 W on xenon. The measured plasma densities and electron temperatures were in the range of 1 Multiplication-Sign 10{sup 12}-1 Multiplication-Sign 10{sup 17} m{sup -3} and 0.5-5.0 eV, respectively. The estimated measurement uncertainty is +6%/-34% in density and +/-30% in electron temperature.

Piezo Voltage Controlled Planar Hall Effect Devices.

Science.gov (United States)

Zhang, Bao; Meng, Kang-Kang; Yang, Mei-Yin; Edmonds, K W; Zhang, Hao; Cai, Kai-Ming; Sheng, Yu; Zhang, Nan; Ji, Yang; Zhao, Jian-Hua; Zheng, Hou-Zhi; Wang, Kai-You

2016-06-22

The electrical control of the magnetization switching in ferromagnets is highly desired for future spintronic applications. Here we report on hybrid piezoelectric (PZT)/ferromagnetic (Co2FeAl) devices in which the planar Hall voltage in the ferromagnetic layer is tuned solely by piezo voltages. The change of planar Hall voltage is associated with magnetization switching through 90° in the plane under piezo voltages. Room temperature magnetic NOT and NOR gates are demonstrated based on the piezo voltage controlled Co2FeAl planar Hall effect devices without the external magnetic field. Our demonstration may lead to the realization of both information storage and processing using ferromagnetic materials.

Higher fractions theory of fractional hall effect

International Nuclear Information System (INIS)

Kostadinov, I.Z.; Popov, V.N.

1985-07-01

A theory of fractional quantum Hall effect is generalized to higher fractions. N-particle model interaction is used and the gap is expressed through n-particles wave function. The excitation spectrum in general and the mean field critical behaviour are determined. The Hall conductivity is calculated from first principles. (author)

Experimental test of 200 W Hall thruster with titanium wall

Science.gov (United States)

Ding, Yongjie; Sun, Hezhi; Peng, Wuji; Xu, Yu; Wei, Liqiu; Li, Hong; Li, Peng; Su, Hongbo; Yu, Daren

2017-05-01

We designed a 200 W Hall thruster based on the technology of pushing down a magnetic field with two permanent magnetic rings. Boron nitride (BN) is an important insulating wall material for Hall thrusters. The discharge characteristics of the designed Hall thruster were studied by replacing BN with titanium (Ti). Experimental results show that the designed Hall thruster can discharge stably for a long time under a Ti channel. Experiments were performed to determine whether the channel and cathode are electrically connected. When the channel wall and cathode are insulated, the divergence angle of the plume increases, but the performance of the Hall thruster is improved in terms of thrust, specific impulse, anode efficiency, and thrust-to-power ratio. Ti exhibits a powerful antisputtering capability, a low emanation rate of gas, and a large structural strength, making it a potential candidate wall material in the design of low-power Hall thrusters.

Composite fermions in the quantum Hall effect

International Nuclear Information System (INIS)

Johnson, B.L.; Kirczenow, G.

1997-01-01

The quantum Hall effect and associated quantum transport phenomena in low-dimensional systems have been the focus of much attention for more than a decade. Recent theoretical development of interesting quasiparticles - 'composite fermions' - has led to significant advances in understanding and predicting the behaviour of two-dimensional electron systems under high transverse magnetic fields. Composite fermions may be viewed as fermions carrying attached (fictitious) magnetic flux. Here we review models of the integer and fractional quantum Hall effects, including the development of a unified picture of the integer and fractional effects based upon composite fermions. The composite fermion picture predicts remarkable new physics: the formation of a Fermi surface at high magnetic fields, and anomalous ballistic transport, thermopower, and surface acoustic wave behaviour. The specific theoretical predictions of the model, as well as the body of experimental evidence for these phenomena are reviewed. We also review recent edge-state models for magnetotransport in low-dimensional devices based on the composite fermion picture. These models explain the fractional quantum Hall effect and transport phenomena in nanoscale devices in a unified framework that also includes edge state models of the integer quantum Hall effect. The features of the composite fermion edge-state model are compared and contrasted with those of other recent edge-state models of the fractional quantum Hall effect. (author)

Magnetic Measurements of the Background Field in the Undulator Hall

International Nuclear Information System (INIS)

Fisher, Andrew

2010-01-01

The steel present in the construction of the undulator hall facility has the potential for changing the ambient fields present in the undulator hall. This note describes a measurement done to make a comparison between the fields in the hall and in the Magnetic Measurement Facility. In order for the undulators to have the proper tuning, the background magnetic field in the Undulator Hall should agree with the background field in the Magnetic Measurements Facility within .5 gauss. In order to verify that this was the case measurements were taken along the length of the undulator hall, and the point measurements were compared to the mean field which was measured on the MMF test bench.

Modulated microwave microscopy and probes used therewith

Science.gov (United States)

Lai, Keji; Kelly, Michael; Shen, Zhi-Xun

2012-09-11

A microwave microscope including a probe tip electrode vertically positionable over a sample and projecting downwardly from the end of a cantilever. A transmission line connecting the tip electrode to the electronic control system extends along the cantilever and is separated from a ground plane at the bottom of the cantilever by a dielectric layer. The probe tip may be vertically tapped near or at the sample surface at a low frequency and the microwave signal reflected from the tip/sample interaction is demodulated at the low frequency. Alternatively, a low-frequency electrical signal is also a non-linear electrical element associated with the probe tip to non-linearly interact with the applied microwave signal and the reflected non-linear microwave signal is detected at the low frequency. The non-linear element may be semiconductor junction formed near the apex of the probe tip or be an FET formed at the base of a semiconducting tip.

Triple Giant Resonance Excitations: A Microscopic Approach

International Nuclear Information System (INIS)

Lanza, E.G.; Andres, M.V.; Catara, F.; Chomaz, Ph.; Fallot, M.; Scarpaci, J.A.

2007-01-01

We present, for the first time, microscopic calculations of inelastic cross sections of the triple excitation of giant resonances induced by heavy ion probes. We start from a microscopic approach based on RPA. The mixing of three-phonon states among themselves and with two- and one-phonon states is considered within a boson expansion with Pauli corrections. In this way we go beyond the standard harmonic approximations and get anharmonic excitation spectra. At the same time we also introduce non-linearities in the external field. The calculations are done by solving semiclassical coupled channel equations, the channels being superpositions of one-, two- and three-phonon states. Previous calculations for the Double Giant Resonance excitation show good agreement with experimental cross sections. The inclusion of the three phonon components confirms the previous results for the DGR and produces a strong increase in the Triple GR energy region

Magnesium Hall Thruster

Science.gov (United States)

Szabo, James J.

2015-01-01

This Phase II project is developing a magnesium (Mg) Hall effect thruster system that would open the door for in situ resource utilization (ISRU)-based solar system exploration. Magnesium is light and easy to ionize. For a Mars- Earth transfer, the propellant mass savings with respect to a xenon Hall effect thruster (HET) system are enormous. Magnesium also can be combusted in a rocket with carbon dioxide (CO2) or water (H2O), enabling a multimode propulsion system with propellant sharing and ISRU. In the near term, CO2 and H2O would be collected in situ on Mars or the moon. In the far term, Mg itself would be collected from Martian and lunar regolith. In Phase I, an integrated, medium-power (1- to 3-kW) Mg HET system was developed and tested. Controlled, steady operation at constant voltage and power was demonstrated. Preliminary measurements indicate a specific impulse (Isp) greater than 4,000 s was achieved at a discharge potential of 400 V. The feasibility of delivering fluidized Mg powder to a medium- or high-power thruster also was demonstrated. Phase II of the project evaluated the performance of an integrated, highpower Mg Hall thruster system in a relevant space environment. Researchers improved the medium power thruster system and characterized it in detail. Researchers also designed and built a high-power (8- to 20-kW) Mg HET. A fluidized powder feed system supporting the high-power thruster was built and delivered to Busek Company, Inc.

Scanning probe microscope simulator for the assessment of noise in scanning probe microscopy controllers

International Nuclear Information System (INIS)

Wutscher, T.; Niebauer, J.; Giessibl, F. J.

2013-01-01

We present an electronic circuit that allows to calibrate and troubleshoot scanning probe microscopy (SPM) controllers with respect to their noise performance. The control signal in an SPM is typically highly nonlinear—the tunneling current in scanning tunneling microscopy (STM) varies exponentially with distance. The exponential current-versus-voltage characteristics of diodes allow to model the current dependence in STM. Additional inputs allow to simulate the effects of external perturbations and the reactions of the control electronics. We characterized the noise performance of the feedback controller using the apparent topography roughness of recorded images. For a comparison of different STM controllers, an optimal gain parameter was determined by exploring settling times through a rectangular perturbation signal. We used the circuit to directly compare the performance of two types of SPM controllers used in our laboratory

Anisotropic quantum quench in the presence of frustration or background gauge fields: A probe of bulk currents and topological chiral edge modes

Science.gov (United States)

Killi, Matthew; Trotzky, Stefan; Paramekanti, Arun

2012-12-01

Bosons and fermions, in the presence of frustration or background gauge fields, can form many-body ground states that support equilibrium charge or spin currents. Motivated by the experimental creation of frustration or synthetic gauge fields in ultracold atomic systems, we propose a general scheme by which making a sudden anisotropic quench of the atom tunneling across the lattice and tracking the ensuing density modulations provides a powerful and gauge-invariant route to probing diverse equilibrium current patterns. Using illustrative examples of trapped superfluid Bose and normal Fermi systems in the presence of artificial magnetic fluxes on square lattices, and frustrated bosons in a triangular lattice, we show that this scheme to probe equilibrium bulk current order works independent of particle statistics. We also show that such quenches can detect chiral edge modes in gapped topological states, such as quantum Hall or quantum spin Hall insulators.

Trends in preference, programming and design of concert halls for symphonic music

DEFF Research Database (Denmark)

Gade, Anders Christian

2008-01-01

This paper discusses the evolution in taste regarding concert hall acoustics and how this can be reflected in the new halls being built today. The clients' and listener's preferences are not only based on listening in existing halls; but also on listening to reproduced music recorded with microph......This paper discusses the evolution in taste regarding concert hall acoustics and how this can be reflected in the new halls being built today. The clients' and listener's preferences are not only based on listening in existing halls; but also on listening to reproduced music recorded...

Vibrational spectroscopy in the electron microscope.

Science.gov (United States)

Krivanek, Ondrej L; Lovejoy, Tracy C; Dellby, Niklas; Aoki, Toshihiro; Carpenter, R W; Rez, Peter; Soignard, Emmanuel; Zhu, Jiangtao; Batson, Philip E; Lagos, Maureen J; Egerton, Ray F; Crozier, Peter A

2014-10-09

Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.

Microscopic studies of the fate of charges in organic semiconductors: Scanning Kelvin probe measurements of charge trapping, transport, and electric fields in p- and n-type devices

Science.gov (United States)

Smieska, Louisa Marion

Organic semiconductors could have wide-ranging applications in lightweight, efficient electronic circuits. However, several fundamental questions regarding organic electronic device behavior have not yet been fully addressed, including the nature of chemical charge traps, and robust models for injection and transport. Many studies focus on engineering devices through bulk transport measurements, but it is not always possible to infer the microscopic behavior leading to the observed measurements. In this thesis, we present scanning-probe microscope studies of organic semiconductor devices in an effort to connect local properties with local device behavior. First, we study the chemistry of charge trapping in pentacene transistors. Working devices are doped with known pentacene impurities and the extent of charge trap formation is mapped across the transistor channel. Trap-clearing spectroscopy is employed to measure an excitation of the pentacene charge trap species, enabling identification of the degradationrelated chemical trap in pentacene. Second, we examine transport and trapping in peryelene diimide (PDI) transistors. Local mobilities are extracted from surface potential profiles across a transistor channel, and charge injection kinetics are found to be highly sensitive to electrode cleanliness. Trap-clearing spectra generally resemble PDI absorption spectra, but one derivative yields evidence indicating variation in trap-clearing mechanisms for different surface chemistries. Trap formation rates are measured and found to be independent of surface chemistry, contradicting a proposed silanol trapping mechanism. Finally, we develop a variation of scanning Kelvin probe microscopy that enables measurement of electric fields through a position modulation. This method avoids taking a numeric derivative of potential, which can introduce high-frequency noise into the electric field signal. Preliminary data is presented, and the theoretical basis for electric field

Hall effect in organic layered conductors

Directory of Open Access Journals (Sweden)

R.A.Hasan

2006-01-01

Full Text Available The Hall effect in organic layered conductors with a multisheeted Fermi surfaces was considered. It is shown that the experimental study of Hall effect and magnetoresistance anisotropy at different orientations of current and a quantizing magnetic field relative to the layers makes it possible to determine the contribution of various charge carriers groups to the conductivity, and to find out the character of Fermi surface anisotropy in the plane of layers.

Tunnelling anomalous and planar Hall effects (Conference Presentation)

Science.gov (United States)

Matos-Abiague, Alex; Scharf, Benedikt; Han, Jong E.; Hankiewicz, Ewelina M.; Zutic, Igor

2016-10-01

We theoretically show how the interplay between spin-orbit coupling (SOC) and magnetism can result in a finite tunneling Hall conductance, transverse to the applied bias. For two-dimensional tunnel junctions with a ferromagnetic lead and magnetization perpendicular to the current flow, the detected anomalous Hall voltage can be used to extract information not only about the spin polarization but also about the strength of the interfacial SOC. In contrast, a tunneling current across a ferromagnetic barrier on the surface of a three-dimensional topological insulator (TI) can induce a planar Hall response even when the magnetization is oriented along the current flow[1]. The tunneling nature of the states contributing to the planar Hall conductance can be switched from the ordinary to the Klein regimes by the electrostatic control of the barrier strength. This allows for an enhancement of the transverse response and a giant Hall angle, with the tunneling planar Hall conductance exceeding the longitudinal component. Despite the simplicity of a single ferromagnetic region, the TI/ferromagnet system exhibits a variety of functionalities. In addition to a spin-valve operation for magnetic sensing and storing information, positive, negative, and negative differential conductances can be tuned by properly adjusting the barrier potential and/or varying the magnetization direction. Such different resistive behaviors in the same system are attractive for potential applications in reconfigurable spintronic devices. [1] B. Scharf, A. Matos-Abiague, J. E. Han, E. M. Hankiewicz, and I. Zutic, arXiv:1601.01009 (2016).

Shielding consideration for the SSCL experimental halls

International Nuclear Information System (INIS)

Bull, J.; Coyne, J.; Mokhov, N.; Stapleton, G.

1994-03-01

The Superconducting Super Collider which is being designed and built in Waxahachie, Texas consists Of series of proton accelerators, culminating in a 20 Te proton on proton collider. The collider will be in a tunnel which will be 87 km in circumference and. on average about 30 meters underground. The present design calls for two large interaction halls on the east side of the ring. The shielding for these halls is being designed for an interaction rate of 10 9 Hz or 10 16 interactions per year, based on 10 7 seconds per operational year. SSC guidelines require that the shielding be designed to meet the criterion of 1mSv per year for open areas off site 2mSv per year for open areas on site, and 2mSv per year for controlled areas. Only radiation workers will be routinely allowed to work in controlled areas. It should be pointed that there is a potential for an accidental full beam loss in either of the experimental halls, and this event would consist of the loss of the full circulating beam up to 4 x 10 14 protons. With the present design. the calculated dose equivalent for this event is about 10% of the annual dose equivalent for the normal p-p interactions, so that die accident condition does not control the shielding. If, for instance, local shielding within the experimental hall is introduced into the calculations, this could change. The shielding requirements presented here are controlled by the normal p-p interactions. Three important questions were addressed in the present calculations. They are (1) the thickness of the roof over the experimental halls, (2) the configuration of the shafts and adits which give access to the halls, and (3) the problem of ground water and air activation

Localization in a quantum spin Hall system.

Science.gov (United States)

Onoda, Masaru; Avishai, Yshai; Nagaosa, Naoto

2007-02-16

The localization problem of electronic states in a two-dimensional quantum spin Hall system (that is, a symplectic ensemble with topological term) is studied by the transfer matrix method. The phase diagram in the plane of energy and disorder strength is exposed, and demonstrates "levitation" and "pair annihilation" of the domains of extended states analogous to that of the integer quantum Hall system. The critical exponent nu for the divergence of the localization length is estimated as nu congruent with 1.6, which is distinct from both exponents pertaining to the conventional symplectic and the unitary quantum Hall systems. Our analysis strongly suggests a different universality class related to the topology of the pertinent system.

Nanospot soldering polystyrene nanoparticles with an optical fiber probe laser irradiating a metallic AFM probe based on the near-field enhancement effect.

Science.gov (United States)

Cui, Jianlei; Yang, Lijun; Wang, Yang; Mei, Xuesong; Wang, Wenjun; Hou, Chaojian

2015-02-04

With the development of nanoscience and nanotechnology for the bottom-up nanofabrication of nanostructures formed from polystyrene nanoparticles, joining technology is an essential step in the manufacturing and assembly of nanodevices and nanostructures in order to provide mechanical integration and connection. To study the nanospot welding of polystyrene nanoparticles, we propose a new nanospot-soldering method using the near-field enhancement effect of a metallic atomic force microscope (AFM) probe tip that is irradiated by an optical fiber probe laser. On the basis of our theoretical analysis of the near-field enhancement effect, we set up an experimental system for nanospot soldering; this approach is carried out by using an optical fiber probe laser to irradiate the AFM probe tip to sinter the nanoparticles, providing a promising technical approach for the application of nanosoldering in nanoscience and nanotechnology.

Observation of the anomalous Hall effect in GaAs

International Nuclear Information System (INIS)

Miah, M Idrish

2007-01-01

Devices for the direct detection of the spin current, based on the anomalous Hall effect (AHE), are fabricated on n-type GaAs bulk semiconductor materials. The AHE is observed in the device when the photoinduced spin-polarized electrons are injected into it, and it is found that the effect depends on the applied electric field. The origin of the field-dependent observed Hall effect is discussed based on the D'yakonov-Perel' (DP) spin relaxation mechanism. The spin-dependent Hall effect is also found to be enhanced with increasing doping concentration. The present experimental results might have potential applications in semiconductor spintronic devices since the effect is closely related to the spin Hall effect

Observation of the anomalous Hall effect in GaAs

Energy Technology Data Exchange (ETDEWEB)

Miah, M Idrish [Nanoscale Science and Technology Centre, School of Science, Griffith University, Nathan, Brisbane, QLD 4111 (Australia); Department of Physics, University of Chittagong, Chittagong, Chittagong - 4331 (Bangladesh)

2007-03-21

Devices for the direct detection of the spin current, based on the anomalous Hall effect (AHE), are fabricated on n-type GaAs bulk semiconductor materials. The AHE is observed in the device when the photoinduced spin-polarized electrons are injected into it, and it is found that the effect depends on the applied electric field. The origin of the field-dependent observed Hall effect is discussed based on the D'yakonov-Perel' (DP) spin relaxation mechanism. The spin-dependent Hall effect is also found to be enhanced with increasing doping concentration. The present experimental results might have potential applications in semiconductor spintronic devices since the effect is closely related to the spin Hall effect.

Handheld magnetic probe with permanent magnet and Hall sensor for identifying sentinel lymph nodes in breast cancer patients.

Science.gov (United States)

Sekino, Masaki; Kuwahata, Akihiro; Ookubo, Tetsu; Shiozawa, Mikio; Ohashi, Kaichi; Kaneko, Miki; Saito, Itsuro; Inoue, Yusuke; Ohsaki, Hiroyuki; Takei, Hiroyuki; Kusakabe, Moriaki

2018-01-19

The newly developed radioisotope-free technique based on magnetic nanoparticle detection using a magnetic probe is a promising method for sentinel lymph node biopsy. In this study, a novel handheld magnetic probe with a permanent magnet and magnetic sensor is developed to detect the sentinel lymph nodes in breast cancer patients. An outstanding feature of the probe is the precise positioning of the sensor at the magnetic null point of the magnet, leading to highly sensitive measurements unaffected by the strong ambient magnetic fields of the magnet. Numerical and experimental results show that the longitudinal detection length is approximately 10 mm, for 140 μg of iron. Clinical tests were performed, for the first time, using magnetic and blue dye tracers-without radioisotopes-in breast cancer patients to demonstrate the performance of the probe. The nodes were identified through transcutaneous and ex-vivo measurements, and the iron accumulation in the nodes was quantitatively revealed. These results show that the handheld magnetic probe is useful in sentinel lymph node biopsy and that magnetic techniques are widely being accepted as future standard methods in medical institutions lacking nuclear medicine facilities.

A micromachined membrane-based active probe for biomolecular mechanics measurement

Science.gov (United States)

Torun, H.; Sutanto, J.; Sarangapani, K. K.; Joseph, P.; Degertekin, F. L.; Zhu, C.

2007-04-01

A novel micromachined, membrane-based probe has been developed and fabricated as assays to enable parallel measurements. Each probe in the array can be individually actuated, and the membrane displacement can be measured with high resolution using an integrated diffraction-based optical interferometer. To illustrate its application in single-molecule mechanics experiments, this membrane probe was used to measure unbinding forces between L-selectin reconstituted in a polymer-cushioned lipid bilayer on the probe membrane and an antibody adsorbed on an atomic force microscope cantilever. Piconewton range forces between single pairs of interacting molecules were measured from the cantilever bending while using the membrane probe as an actuator. The integrated diffraction-based optical interferometer of the probe was demonstrated to have floor for frequencies as low as 3 Hz with a differential readout scheme. With soft probe membranes, this low noise level would be suitable for direct force measurements without the need for a cantilever. Furthermore, the probe membranes were shown to have 0.5 µm actuation range with a flat response up to 100 kHz, enabling measurements at fast speeds.

Scanning probe lithography for fabrication of Ti metal nanodot arrays

International Nuclear Information System (INIS)

Jung, B.; Jo, W.; Gwon, M.J.; Lee, E.; Kim, D.-W.

2010-01-01

We report fabrication of Ti metal nanodot arrays by scanning probe microscopic indentation. A thin poly-methylmethacrylate (PMMA) layer was spin-coated on Si substrates with thickness of 70 nm. Nanometer-size pore arrays were formed by indenting the PMMA layer using a cantilever of a scanning probe microscope. Protuberances with irregular boundaries appeared during the indentation process. Control of approach and pulling-out speed during indentation was able to dispose of the protrusions. Ti metal films were deposited on the patterned PMMA layers by a radio-frequency sputtering method and subsequently lifted off to obtain metal nanodot arrays. The fabricated metal nanodot arrays have 200 nm of diameter and 500 nm of interdistance, which corresponds to a density of 4x10 8 /cm 2 . Scanning probe-based measurement of current-voltage (I-V) behaviors for a single Ti metal nanodot showed asymmetric characteristics. Applying external bias is likely to induce oxidation of Ti metal, since the conductance decreased and volume change of the dots was observed. I-V behaviors of Ti metal nanodots by conventional e-beam lithography were also characterized for comparison.

A holographic model for the fractional quantum Hall effect

Energy Technology Data Exchange (ETDEWEB)

Lippert, Matthew [Institute for Theoretical Physics, University of Amsterdam,Science Park 904, 1090GL Amsterdam (Netherlands); Meyer, René [Kavli Institute for the Physics and Mathematics of the Universe (WPI), The University of Tokyo,Kashiwa, Chiba 277-8568 (Japan); Taliotis, Anastasios [Theoretische Natuurkunde, Vrije Universiteit Brussel andThe International Solvay Institutes,Pleinlaan 2, B-1050 Brussels (Belgium)

2015-01-08

Experimental data for fractional quantum Hall systems can to a large extent be explained by assuming the existence of a Γ{sub 0}(2) modular symmetry group commuting with the renormalization group flow and hence mapping different phases of two-dimensional electron gases into each other. Based on this insight, we construct a phenomenological holographic model which captures many features of the fractional quantum Hall effect. Using an SL(2,ℤ)-invariant Einstein-Maxwell-axio-dilaton theory capturing the important modular transformation properties of quantum Hall physics, we find dyonic diatonic black hole solutions which are gapped and have a Hall conductivity equal to the filling fraction, as expected for quantum Hall states. We also provide several technical results on the general behavior of the gauge field fluctuations around these dyonic dilatonic black hole solutions: we specify a sufficient criterion for IR normalizability of the fluctuations, demonstrate the preservation of the gap under the SL(2,ℤ) action, and prove that the singularity of the fluctuation problem in the presence of a magnetic field is an accessory singularity. We finish with a preliminary investigation of the possible IR scaling solutions of our model and some speculations on how they could be important for the observed universality of quantum Hall transitions.

A holographic model for the fractional quantum Hall effect

Science.gov (United States)

Lippert, Matthew; Meyer, René; Taliotis, Anastasios

2015-01-01

Experimental data for fractional quantum Hall systems can to a large extent be explained by assuming the existence of a Γ0(2) modular symmetry group commuting with the renormalization group flow and hence mapping different phases of two-dimensional electron gases into each other. Based on this insight, we construct a phenomenological holographic model which captures many features of the fractional quantum Hall effect. Using an -invariant Einstein-Maxwell-axio-dilaton theory capturing the important modular transformation properties of quantum Hall physics, we find dyonic diatonic black hole solutions which are gapped and have a Hall conductivity equal to the filling fraction, as expected for quantum Hall states. We also provide several technical results on the general behavior of the gauge field fluctuations around these dyonic dilatonic black hole solutions: we specify a sufficient criterion for IR normalizability of the fluctuations, demonstrate the preservation of the gap under the action, and prove that the singularity of the fluctuation problem in the presence of a magnetic field is an accessory singularity. We finish with a preliminary investigation of the possible IR scaling solutions of our model and some speculations on how they could be important for the observed universality of quantum Hall transitions.

Development of X-ray excitable luminescent probes for scanning X-ray microscopy

International Nuclear Information System (INIS)

Moronne, M.M.

1999-01-01

Transmission soft X-ray microscopy is now capable of achieving resolutions that are typically 5 times better than the best-visible light microscopes. With expected improvements in zone plate optics, an additional factor of two may be realized within the next few years. Despite the high resolution now available with X-ray microscopes and the high X-ray contrast provided by biological molecules in the soft X-ray region (λ=2-5 nm), molecular probes for localizing specific biological targets have been lacking. To circumvent this problem, X-ray excitable molecular probes are needed that can target unique biological features. In this paper we report our initial results on the development of lanthanide-based fluorescent probes for biological labeling. Using scanning luminescence X-ray microscopy (SLXM, Jacobsen et al., J. Microscopy 172 (1993) 121-129), we show that lanthanide organo-polychelate complexes are sufficiently bright and radiation resistant to be the basis of a new class of X-ray excitable molecular probes capable of providing at least a fivefold improvement in resolution over visible light microscopy. Lanthanide probes, able to bind 80-100 metal ions per molecule, were found to give strong luminescent signals with X-ray doses exceeding 10 8 Gy, and were used to label actin stress fibers and in vitro preparations of polymerized tubulin. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)

Investigation of static and dynamic behavior of functionally graded piezoelectric actuated Poly-Si micro cantilever probe

Energy Technology Data Exchange (ETDEWEB)

Pandey, Vibhuti Bhushan; Parashar, Sandeep Kumar, E-mail: skparashar@rtu.ac.in [Department of Mechanical Engineering, Rajasthan Technical University, Kota (India)

2016-04-13

In the present paper a novel functionally graded piezoelectric (FGP) actuated Poly-Si micro cantilever probe is proposed for atomic force microscope. The shear piezoelectric coefficient d{sub 15} has much higher value than coupling coefficients d{sub 31} and d{sub 33}, hence in the present work the micro cantilever beam actuated by d{sub 15} effect is utilized. The material properties are graded in the thickness direction of actuator by a simple power law. A three dimensional finite element analysis has been performed using COMSOL Multiphysics® (version 4.2) software. Tip deflection and free vibration analysis for the micro cantilever probe has been done. The results presented in the paper shall be useful in the design of micro cantilever probe and their subsequent utilization in atomic force microscopes.

Quantum Hall Ferroelectrics and Nematics in Multivalley Systems

Science.gov (United States)

Sodemann, Inti; Zhu, Zheng; Fu, Liang

2017-10-01

We study broken symmetry states at integer Landau-level fillings in multivalley quantum Hall systems whose low-energy dispersions are anisotropic. When the Fermi surface of individual pockets lacks twofold rotational symmetry, like in bismuth (111) [Feldman et al. , Observation of a Nematic Quantum Hall Liquid on the Surface of Bismuth, Science 354, 316 (2016), 10.1126/science.aag1715] and in Sn1 -xPbxSe (001) [Dziawa et al., Topological Crystalline Insulator States in Pb1 -xSnxSe , Nat. Mater. 11, 1023 (2012), 10.1038/nmat3449] surfaces, interactions tend to drive the formation of quantum Hall ferroelectric states. We demonstrate that the dipole moment in these states has an intimate relation to the Fermi surface geometry of the parent metal. In quantum Hall nematic states, like those arising in AlAs quantum wells, we demonstrate the existence of unusually robust Skyrmion quasiparticles.

A Novel Hall Effect Sensor Using Elaborate Offset Cancellation Method

Directory of Open Access Journals (Sweden)

Vlassis N. Petoussis

2009-01-01

Full Text Available The Hall effect is caused by a traverse force that is formed in the electrons or holes of metal element or semiconductor when are polarized by current source and simultaneously all the system it is found vertical in external magnetic field. Result is finally the production of difference of potential (Hall voltage in address vertical in that of current and magnetic field directions. In the present work is presented a new Hall sensor exploiting the former operation. In combination with his pioneering form and using dynamic spinning current technique with an elaborate sequence, it leads to satisfactory results of produced Hall voltage with small noise in a presence of external magnetic field. Anyone can see both the spinning current and anti-Hall technique in the same sensor simultaneously.

Proposed measurement of tagged deep inelastic scattering in Hall A of Jefferson lab

Energy Technology Data Exchange (ETDEWEB)

Montgomery, Rachel [Univ. of Glasgow, Scotland (United Kingdom); Annand, John [Univ. of Glasgow, Scotland (United Kingdom); Dutta, Dipangkar [Mississippi State Univ., Mississippi State, MS (United States); Keppel, Cynthia E. [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); King, Paul [The Ohio State Univ., Columbus, OH (United States). Dept of Physics; Wojtsekhowski, Bogdan [Thomas Jefferson National Accelerator Facility (TJNAF), Newport News, VA (United States); Zhang, Jixie [Univ. of Virginia, Charlottesville, VA (United States)

2017-03-01

A tagged deep inelastic scattering (TDIS) experiment is planned for Hall A of Jefferson Lab, which will probe the mesonic content of the nucleon directly. Low momentum recoiling (and spectator) protons will be measured in coincidence with electrons scattered in a deep inelastic regime from hydrogen (and deuterium) targets, covering kinematics of 8 < W2 < 18 GeV2, 1 < Q2 < 3 (GeV/c)2 and 0:05 < x < 0:2. The tagging technique will help identify scattering from partons in the meson cloud and provide access to the pion structure function via the Sullivan process. The experiment will yield the first TDIS results in the valence regime, for both proton and neutron targets. We present here an overview of the experiment.

Digital technology impacts on the Arnhem transfer hall structural design

NARCIS (Netherlands)

Van de Straat, R.; Hofman, S.; Coenders, J.L.; Paul, J.C.

2015-01-01

The new Transfer Hall in Arnhem is one of the key projects to prepare the Dutch railways for the increased future demands for capacity. UNStudio developed a master plan in 1996 for the station area of which the completion of the Transfer Hall in 2015 will be a final milestone. The Transfer Hall is a

Isotope analysis in the transmission electron microscope.

Science.gov (United States)

Susi, Toma; Hofer, Christoph; Argentero, Giacomo; Leuthner, Gregor T; Pennycook, Timothy J; Mangler, Clemens; Meyer, Jannik C; Kotakoski, Jani

2016-10-10

The Ångström-sized probe of the scanning transmission electron microscope can visualize and collect spectra from single atoms. This can unambiguously resolve the chemical structure of materials, but not their isotopic composition. Here we differentiate between two isotopes of the same element by quantifying how likely the energetic imaging electrons are to eject atoms. First, we measure the displacement probability in graphene grown from either 12 C or 13 C and describe the process using a quantum mechanical model of lattice vibrations coupled with density functional theory simulations. We then test our spatial resolution in a mixed sample by ejecting individual atoms from nanoscale areas spanning an interface region that is far from atomically sharp, mapping the isotope concentration with a precision better than 20%. Although we use a scanning instrument, our method may be applicable to any atomic resolution transmission electron microscope and to other low-dimensional materials.

Acoustic investigations of concert halls for rock music

DEFF Research Database (Denmark)

Adelman-Larsen, Niels Werner; Thompson, Eric Robert; Gade, Anders Christian

2007-01-01

Objective measurement data and subjective evaluations have been collected from 20 small-/medium-sized halls in Denmark used for amplified rhythmic music concerts (pop, rock, jazz). The purpose of the study was to obtain knowledge about optimum acoustic conditions for this type of hall. The study...... is motivated by the fact that most concert tickets sold in Denmark relate to concerts within these genres in this kind of venue. The subjective evaluations were carried out by professional musicians and sound engineers who responded on the basis of their experiences working in these (and other) halls. From...

Laser Safety for the Experimental Halls at SLAC_s Linac Coherent Light Source (LCLS)

Energy Technology Data Exchange (ETDEWEB)

Woods, Michael; Anthony, Perry; /SLAC; Barat, Ken; /LBL, Berkeley; Gilevich, Sasha; Hays, Greg; White, William E.; /SLAC

2009-01-15

The LCLS at the SLAC National Accelerator Laboratory will be the world's first source of an intense hard x-ray laser beam, generating x-rays with wavelengths of 1nm and pulse durations less than 100fs. The ultrafast x-ray pulses will be used in pump-probe experiments to take stop-motion pictures of atoms and molecules in motion, with pulses powerful enough to take diffraction images of single molecules, enabling scientists to elucidate fundamental processes of chemistry and biology. Ultrafast conventional lasers will be used as the pump. In 2009, LCLS will deliver beam to the Atomic Molecular and Optical (AMO) Experiment, located in one of 3 x-ray Hutches in the Near Experimental Hall (NEH). The NEH includes a centralized Laser Hall, containing up to three Class 4 laser systems, three x-ray Hutches for experiments and vacuum transport tubes for delivering laser beams to the Hutches. The main components of the NEH laser systems are a Ti:sapphire oscillator, a regen amplifier, green pump lasers for the oscillator and regen, a pulse compressor and a harmonics conversion unit. Laser safety considerations and controls for the ultrafast laser beams, multiple laser controlled areas, and user facility issues are discussed.

Variable-temperature independently driven four-tip scanning tunneling microscope

International Nuclear Information System (INIS)

Hobara, Rei; Nagamura, Naoka; Hasegawa, Shuji; Matsuda, Iwao; Yamamoto, Yuko; Miyatake, Yutaka; Nagamura, Toshihiko

2007-01-01

The authors have developed an ultrahigh vacuum (UHV) variable-temperature four-tip scanning tunneling microscope (STM), operating from room temperature down to 7 K, combined with a scanning electron microscope (SEM). Four STM tips are mechanically and electrically independent and capable of positioning in arbitrary configurations in nanometer precision. An integrated controller system for both of the multitip STM and SEM with a single computer has also been developed, which enables the four tips to operate either for STM imaging independently and for four-point probe (4PP) conductivity measurements cooperatively. Atomic-resolution STM images of graphite were obtained simultaneously by the four tips. Conductivity measurements by 4PP method were also performed at various temperatures with the four tips in square arrangement with direct contact to the sample surface

Magnetohydrodynamic simulations of Gamble I POS with Hall effect

International Nuclear Information System (INIS)

Roderick, N.F.; Frese, M.H.; Peterkin, R.E.; Payne, S.S.

1989-01-01

Two dimensional single fluid magnetohydrodynamic simulations have been conducted to investigate the effects of the Hall electric field on magnetic field transport in plasma opening switches of the type used on Gamble I. The Hall terms were included in the magnetic field transport equation in the two dimensional simulation code MACH2 through the use of a generalized Ohm's law. Calculations show the Hall terms augment the field transport previously observed to occur through ion fluid motion and diffusion. For modest values of microturbulent collision frequency, board current channels were observed . Results also show the magnetic field transport to be affected by the cathode boundary conditions with the Hall terms included. In all cases center of mass motion was slight

Integrated microfluidic probe station.

Science.gov (United States)

Perrault, C M; Qasaimeh, M A; Brastaviceanu, T; Anderson, K; Kabakibo, Y; Juncker, D

2010-11-01

The microfluidic probe (MFP) consists of a flat, blunt tip with two apertures for the injection and reaspiration of a microjet into a solution--thus hydrodynamically confining the microjet--and is operated atop an inverted microscope that enables live imaging. By scanning across a surface, the microjet can be used for surface processing with the capability of both depositing and removing material; as it operates under immersed conditions, sensitive biological materials and living cells can be processed. During scanning, the MFP is kept immobile and centered over the objective of the inverted microscope, a few micrometers above a substrate that is displaced by moving the microscope stage and that is flushed continuously with the microjet. For consistent and reproducible surface processing, the gap between the MFP and the substrate, the MFP's alignment, the scanning speed, the injection and aspiration flow rates, and the image capture need all to be controlled and synchronized. Here, we present an automated MFP station that integrates all of these functionalities and automates the key operational parameters. A custom software program is used to control an independent motorized Z stage for adjusting the gap, a motorized microscope stage for scanning the substrate, up to 16 syringe pumps for injecting and aspirating fluids, and an inverted fluorescence microscope equipped with a charge-coupled device camera. The parallelism between the MFP and the substrate is adjusted using manual goniometer at the beginning of the experiment. The alignment of the injection and aspiration apertures along the scanning axis is performed using a newly designed MFP screw holder. We illustrate the integrated MFP station by the programmed, automated patterning of fluorescently labeled biotin on a streptavidin-coated surface.

Study and Developement of Compact Permanent Magnet Hall Thrusters for Future Brazillian Space Missions

Science.gov (United States)

Ferreira, Jose Leonardo; Martins, Alexandre; Cerda, Rodrigo

2016-07-01

maneuvering. A joint brazillian space mission on the solar system has also been consider for the coming years. ASTER project is a mission to a near earth asteroid that is planned to be carried on using Hall thrusters. The PHALL project consists on plasma source design, construction and characterization of plasma propulsion engines based on Hall current generated inside a cylindrical channel with an axial electric field produced by a ring anode and a radial magnetic field produced by permanent magnets. One of the main advantage of PHALL thruster is the production of a steady state magnetic field by permanent magnets providing electron trapping and Hall current generation within a significant decrease on the electric energy supply. This advantage turns PHALL thruster into a specially good option when it comes to space usage for longer and deep space missions, where solar panels and electric energy storage on batteries is a limiting factor. This work also describes the Hall Plasma Source construction and characteristics and the plasma diagnostics system used on BID, an Integrated Plasma Diagnostic System. This system contains Langmuir probes that are used for plasma density and temperature measurements. Faraday Cup, Ion probes and Spectrograph (Andor SR-750-B2, within 435nm to 700nm) line broadening measurements are used to measure ion temperature and transport from Hall current channel to the ejected plasma plume. In order to control argon fuel purity a mass spectrometer is also planned to be used. Thrust and Specific Impulse measurements will also be shown. Important to notice relevant plasma physics phenomena investigation that may significantly interfere on PHALL performance. It is the occurrence of instabilities that can happen inside and outside of the Hall current channel. In order to better understand the turbulence and plasma oscillations that occur during the thruster operation, we propose and test a wide frequency range instability detection system based on a RF

Application of a new MR Microscope using an Independent Console System (MRMICS) for biological tissues in vitro

International Nuclear Information System (INIS)

Yoshioka, Hiroshi; Anno, Izumi; Itai, Yuji; Haishi, Tomoyuki; Adachi, Naotaka; Kose, Katsumi

1999-01-01

We studied microscopic MR images of the normal appendix in vitro using a new MR microscope system: MR Microscope using an Independent Console System (MRMICS). The MRMICS was placed in the clinical MR room, and the probe box was fixed on the bed of the 1.5 T clinical MR machine. T1-, T2-, and proton density-weighted images were obtained using spin echo sequences with an in-plane pixel size of 100 x 100 μm. Zonal structures of the appendix were clearly demonstrated with different contrast by different sequences. Therefore, the MRMICS is a useful add-on system for investigating microscopic MR images of biological tissues in vitro. (author)

Application of a new MR Microscope using an Independent Console System (MRMICS) for biological tissues in vitro

Energy Technology Data Exchange (ETDEWEB)

Yoshioka, Hiroshi; Anno, Izumi; Itai, Yuji [Tsukuba Univ., Ibaraki (Japan). Inst. of Clinical Medicine; Haishi, Tomoyuki; Adachi, Naotaka; Kose, Katsumi

1999-02-01

We studied microscopic MR images of the normal appendix in vitro using a new MR microscope system: MR Microscope using an Independent Console System (MRMICS). The MRMICS was placed in the clinical MR room, and the probe box was fixed on the bed of the 1.5 T clinical MR machine. T1-, T2-, and proton density-weighted images were obtained using spin echo sequences with an in-plane pixel size of 100 x 100 {mu}m. Zonal structures of the appendix were clearly demonstrated with different contrast by different sequences. Therefore, the MRMICS is a useful add-on system for investigating microscopic MR images of biological tissues in vitro. (author)

Spin Hall effect on a noncommutative space

International Nuclear Information System (INIS)

Ma Kai; Dulat, Sayipjamal

2011-01-01

We study the spin-orbital interaction and the spin Hall effect of an electron moving on a noncommutative space under the influence of a vector potential A(vector sign). On a noncommutative space, we find that the commutator between the vector potential A(vector sign) and the electric potential V 1 (r(vector sign)) of the lattice induces a new term, which can be treated as an effective electric field, and the spin Hall conductivity obtains some correction. On a noncommutative space, the spin current and spin Hall conductivity have distinct values in different directions, and depend explicitly on the noncommutative parameter. Once this spin Hall conductivity in different directions can be measured experimentally with a high level of accuracy, the data can then be used to impose bounds on the value of the space noncommutativity parameter. We have also defined a new parameter, σ=ρθ (ρ is the electron concentration, θ is the noncommutativity parameter), which can be measured experimentally. Our approach is based on the Foldy-Wouthuysen transformation, which gives a general Hamiltonian of a nonrelativistic electron moving on a noncommutative space.

Diagnostics Systems for Permanent Hall Thrusters Development

Science.gov (United States)

Ferreira, Jose Leonardo; Soares Ferreira, Ivan; Santos, Jean; Miranda, Rodrigo; Possa, M. Gabriela

This work describes the development of Permanent Magnet Hall Effect Plasma Thruster (PHALL) and its diagnostic systems at The Plasma Physics Laboratory of University of Brasilia. The project consists on the construction and characterization of plasma propulsion engines based on the Hall Effect. Electric thrusters have been employed in over 220 successful space missions. Two types stand out: the Hall-Effect Thruster (HET) and the Gridded Ion Engine (GIE). The first, which we deal with in this project, has the advantage of greater simplicity of operation, a smaller weight for the propulsion subsystem and a longer shelf life. It can operate in two configurations: magnetic layer and anode layer, the difference between the two lying in the positioning of the anode inside the plasma channel. A Hall-Effect Thruster-HET is a type of plasma thruster in which the propellant gas is ionized and accelerated by a magneto hydrodynamic effect combined with electrostatic ion acceleration. So the essential operating principle of the HET is that it uses a J x B force and an electrostatic potential to accelerate ions up to high speeds. In a HET, the attractive negative charge is provided by electrons at the open end of the Thruster instead of a grid, as in the case of the electrostatic ion thrusters. A strong radial magnetic field is used to hold the electrons in place, with the combination of the magnetic field and the electrostatic potential force generating a fast circulating electron current, the Hall current, around the axis of the Thruster, mainly composed by drifting electrons in an ion plasma background. Only a slow axial drift towards the anode occurs. The main attractive features of the Hall-Effect Thruster are its simple design and operating principles. Most of the Hall-Effect Thrusters use electromagnet coils to produce the main magnetic field responsible for plasma generation and acceleration. In this paper we present a different new concept, a Permanent Magnet Hall

Instrumental Developments for In-situ Breakdown Experiments inside a Scanning Electron Microscope

CERN Document Server

Muranaka, T; Leifer, K; Ziemann, V

2011-01-01

Electrical discharges in accelerating structures are one of the key issues limiting the performance of future high energy accelerators such as the Compact Linear Collider (CLIC). Fundamental understanding of breakdown phenomena is an indispensable part of the CLIC feasibility study. The present work concerns the experimental study of breakdown using Scanning Electron Microscopes (SEMs). A SEM gives us the opportunity to achieve high electrical gradients of 1\\,kV/$\\mu$m which corresponds to 1\\,GV/m by exciting a probe needle with a high voltage power supply and controlling the positioning of the needle with a linear piezo motor. The gap between the needle tip and the surface is controlled with sub-micron precision. A second electron microscope equipped with a Focused Ion Beam (FIB) is used to create surface corrugations and to sharpen the probe needle to a tip radius of about 50\\,nm. Moreover it is used to prepare cross sections of a voltage breakdown area in order to study the geometrical surface damages as w...

Simulation-aided design and fabrication of nanoprobes for scanning probe microscopy

International Nuclear Information System (INIS)

Liu, Bernard Haochih; Chang, Day-Bin

2011-01-01

We proposed and demonstrated a flexible and effective method to design and fabricate scanning probes for atomic force microscopy applications. Computer simulations were adopted to evaluate design specifications and desired performance of atomic force microscope (AFM) probes; the fabrication processes were guided by feedback from simulation results. Through design-simulation-fabrication iterations, tipless cantilevers and tapping mode probes were successfully made with errors as low as 2% in designed resonant frequencies. For tapping mode probes, the probe tip apex achieved a 10 nm radius of curvature without additional sharpening steps; tilt-compensated probes were also fabricated for better scanning performance. This method provides AFM users improved probe quality and practical guidelines for customized probes, which can support the development of novel scanning probe microscopy (SPM) applications. -- Research highlights: → We developed a design-simulation-fabrication strategy for customized AFM/SPM probes and demonstrated the results of tipless cantilever, sharpened probe tip, and tilt-compensated probe. → This simulation-aided method improved the geometry control and performance prediction of AFM probes; the error in resonant frequency was reduced to ∼2%. → Integration of simulation in design and fabrication of AFM probes expedites development of new probes and consequently promotes novel SPM applications.

Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator.

Science.gov (United States)

Takahashi, Hideyuki; Imai, Yoshinori; Maeda, Atsutaka

2016-06-01

We present a design for a tunneling-current-assisted scanning near-field microwave microscope. For stable operation at cryogenic temperatures, making a small and rigid microwave probe is important. Our coaxial resonator probe has a length of approximately 30 mm and can fit inside the 2-in. bore of a superconducting magnet. The probe design includes an insulating joint, which separates DC and microwave signals without degrading the quality factor. By applying the SMM to the imaging of an electrically inhomogeneous superconductor, we obtain the spatial distribution of the microwave response with a spatial resolution of approximately 200 nm. Furthermore, we present an analysis of our SMM probe based on a simple lumped-element circuit model along with the near-field microwave measurements of silicon wafers having different conductivities.

Hole mobilities and the effective Hall factor in p-type GaAs

Science.gov (United States)

Wenzel, M.; Irmer, G.; Monecke, J.; Siegel, W.

1997-06-01

We prove the effective Hall factor in p-GaAs to be larger than values discussed in the literature up to now. The scattering rates for the relevant scattering mechanisms in p-GaAs have been recalculated after critical testing the existing models. These calculations allow to deduce theoretical drift and theoretical Hall mobilities as functions of temperature which can be compared with measured data. Theoretical Hall factors in the heavy and light hole bands and an effective Hall factor result. The calculated room temperature values of the drift mobility and of the effective Hall factor are 118 cm2/V s and 3.6, respectively. The fitted acoustic deformation potential E1=7.9 eV and the fitted optical coupling constant DK=1.24×1011 eV/m are close to values published before. It is shown that the measured strong dependence of the Hall mobility on the Hall concentration is not mainly caused by scattering by ionized impurities but by the dependence of the effective Hall factor on the hole concentration.

Field theory approach to quantum hall effect

International Nuclear Information System (INIS)

Cabo, A.; Chaichian, M.

1990-07-01

The Fradkin's formulation of statistical field theory is applied to the Coulomb interacting electron gas in a magnetic field. The electrons are confined to a plane in normal 3D-space and also interact with the physical 3D-electromagnetic field. The magnetic translation group (MTG) Ward identities are derived. Using them it is shown that the exact electron propagator is diagonalized in the basis of the wave functions of the free electron in a magnetic field whenever the MTG is unbroken. The general tensor structure of the polarization operator is obtained and used to show that the Chern-Simons action always describes the Hall effect properties of the system. A general proof of the Streda formula for the Hall conductivity is presented. It follows that the coefficient of the Chern-Simons terms in the long-wavelength approximation is exactly given by this relation. Such a formula, expressing the Hall conductivity as a simple derivative, in combination with diagonal form of the full propagator allows to obtain a simple expressions for the filling factor and the Hall conductivity. Indeed, these results, after assuming that the chemical potential lies in a gap of the density of states, lead to the conclusion that the Hall conductivity is given without corrections by σ xy = νe 2 /h where ν is the filling factor. In addition it follows that the filling factor is independent of the magnetic field if the chemical potential remains in the gap. (author). 21 ref, 1 fig

Scanning probe microscopy experiments in microgravity

International Nuclear Information System (INIS)

Drobek, Tanja; Reiter, Michael; Heckl, Wolfgang M.

2004-01-01

The scanning probe microscopy setups are small, lightweight and do not require vacuum or high voltage supply. In addition, samples can be investigated directly without further preparation. Therefore, these techniques are well-suited for applications in space, in particular, for operation on the International Space Station (ISS) or for high resolution microscopy on planetary missions. A feasibility study for a scanning tunneling microscopy setup was carried out on a parabolic flight campaign in November 2001 in order to test the technical setup for microgravity applications. With a pocket-size design microscope, a graphite surface was imaged under ambient conditions. Atomic resolution was achieved although the quality of the images was inferior in comparison to laboratory conditions. Improvements for future scanning probe microscopy experiments in microgravity are suggested

Generation and spectroscopic signatures of a fractional quantum Hall liquid of photons in an incoherently pumped optical cavity

Science.gov (United States)

Umucalılar, R. O.; Carusotto, I.

2017-11-01

We investigate theoretically a driven dissipative model of strongly interacting photons in a nonlinear optical cavity in the presence of a synthetic magnetic field. We show the possibility of using a frequency-dependent incoherent pump to create a strongly correlated ν =1 /2 bosonic Laughlin state of light: Due to the incompressibility of the Laughlin state, fluctuations in the total particle number and excitation of edge modes can be tamed by imposing a suitable external potential profile for photons. We further propose angular-momentum-selective spectroscopy of the emitted light as a tool to obtain unambiguous signatures of the microscopic physics of the quantum Hall liquid of light.

Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

Science.gov (United States)

Mani, Arjun; Benjamin, Colin

2016-04-13

On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin-orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible--the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case.

Are quantum spin Hall edge modes more resilient to disorder, sample geometry and inelastic scattering than quantum Hall edge modes?

International Nuclear Information System (INIS)

Mani, Arjun; Benjamin, Colin

2016-01-01

On the surface of 2D topological insulators, 1D quantum spin Hall (QSH) edge modes occur with Dirac-like dispersion. Unlike quantum Hall (QH) edge modes, which occur at high magnetic fields in 2D electron gases, the occurrence of QSH edge modes is due to spin–orbit scattering in the bulk of the material. These QSH edge modes are spin-dependent, and chiral-opposite spins move in opposing directions. Electronic spin has a larger decoherence and relaxation time than charge. In view of this, it is expected that QSH edge modes will be more robust to disorder and inelastic scattering than QH edge modes, which are charge-dependent and spin-unpolarized. However, we notice no such advantage accrues in QSH edge modes when subjected to the same degree of contact disorder and/or inelastic scattering in similar setups as QH edge modes. In fact we observe that QSH edge modes are more susceptible to inelastic scattering and contact disorder than QH edge modes. Furthermore, while a single disordered contact has no effect on QH edge modes, it leads to a finite charge Hall current in the case of QSH edge modes, and thus a vanishing of the pure QSH effect. For more than a single disordered contact while QH states continue to remain immune to disorder, QSH edge modes become more susceptible—the Hall resistance for the QSH effect changes sign with increasing disorder. In the case of many disordered contacts with inelastic scattering included, while quantization of Hall edge modes holds, for QSH edge modes a finite charge Hall current still flows. For QSH edge modes in the inelastic scattering regime we distinguish between two cases: with spin-flip and without spin-flip scattering. Finally, while asymmetry in sample geometry can have a deleterious effect in the QSH case, it has no impact in the QH case. (paper)

Performance Comparison of Cross-Like Hall Plates with Different Covering Layers

Directory of Open Access Journals (Sweden)

Fei Lyu

2014-12-01

Full Text Available This paper studies the effects of the covering layers on the performance of a cross-like Hall plate. Three different structures of a cross-like Hall plate in various sizes are designed and analyzed. The Hall plate sensitivity and offset are characterized using a self-built measurement system. The effect of the P-type region over the active area on the current-related sensitivity is studied for different Hall plate designs. In addition, the correlation between the P-type covering layer and offset is analyzed. The best structure out of three designs is determined. Besides, a modified eight-resistor circuit model for the Hall plate is presented with improved accuracy by taking the offset into account.

Enhanced Performance of Cylindrical Hall Thrusters

International Nuclear Information System (INIS)

Raitses, Y.; Smirnov, A.; Fisch, N.J.

2007-01-01

The cylindrical thruster differs significantly in its underlying physical mechanisms from the conventional annular Hall thruster. It features high ionization efficiency, quiet operation, ion acceleration in a large volume-to-surface ratio channel, and performance comparable with the state-of-the-art conventional Hall thrusters. Very significant plume narrowing, accompanied by the increase of the energetic ion fraction and improvement of ion focusing, led to 50-60% increase of the thruster anode efficiency. These improvements were achieved by overrunning the discharge current in the magnetized thruster plasma

Theory of fractional quantum Hall effect

International Nuclear Information System (INIS)

Kostadinov, I.Z.

1984-09-01

A theory of the fractional quantum Hall effect is constructed by introducing 3-particle interactions breaking the symmetry for ν=1/3 according to a degeneracy theorem proved here. An order parameter is introduced and a gap in the single particle spectrum is found. The critical temperature, critical filling number and critical behaviour are determined as well as the Ginzburg-Landau equation coefficients. A first principle calculation of the Hall current is given. 3, 5, 7 electron tunneling and Josephson interference effects are predicted. (author)

21 CFR 884.6190 - Assisted reproductive microscopes and microscope accessories.

Science.gov (United States)

2010-04-01

... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Assisted reproductive microscopes and microscope... Devices § 884.6190 Assisted reproductive microscopes and microscope accessories. (a) Identification. Assisted reproduction microscopes and microscope accessories (excluding microscope stage warmers, which are...

ε-iron nitrides: Intrinsic anomalous Hall ferromagnets

Directory of Open Access Journals (Sweden)

Guo-Ke Li

2015-02-01

Full Text Available The anomalous Hall effect in ε-iron nitrides (ε-Fe3-xN, 0 ≤ x ≤ 1 has been systematically investigated taking advantage of the fact that the exchange splitting of ε-Fe3-xN can be continuously tuned through the nitrogen concentration. It has been found that the anomalous Hall conductivity, σ x y A H , is proportional to the saturation magnetization MS, i.e., σ x y A H = S H M S , across significant variations in the saturation magnetization (96–1146 emu/cc. This relationship is in excellent agreement with the intrinsic mechanism as well as with the unified theory of AHE. Our results also demonstrate that the anomalous Hall conductivity is sensitive to the exchange splitting of the band structure.

Signatures of lattice geometry in quantum and topological Hall effect

International Nuclear Information System (INIS)

Göbel, Börge; Mook, Alexander; Mertig, Ingrid; Henk, Jürgen

2017-01-01

The topological Hall effect (THE) of electrons in skyrmion crystals (SkXs) is strongly related to the quantum Hall effect (QHE) on lattices. This relation suggests to revisit the QHE because its Hall conductivity can be unconventionally quantized. It exhibits a jump and changes sign abruptly if the Fermi level crosses a van Hove singularity. In this Paper, we investigate the unconventional QHE features by discussing band structures, Hall conductivities, and topological edge states for square and triangular lattices; their origin are Chern numbers of bands in the SkX (THE) or of the corresponding Landau levels (QHE). Striking features in the energy dependence of the Hall conductivities are traced back to the band structure without magnetic field whose properties are dictated by the lattice geometry. Based on these findings, we derive an approximation that allows us to determine the energy dependence of the topological Hall conductivity on any two-dimensional lattice. The validity of this approximation is proven for the honeycomb lattice. We conclude that SkXs lend themselves for experiments to validate our findings for the THE and—indirectly—the QHE. (paper)

Hall conductance and topological invariant for open systems.

Science.gov (United States)

Shen, H Z; Wang, W; Yi, X X

2014-09-24

The Hall conductivity given by the Kubo formula is a linear response of quantum transverse transport to a weak electric field. It has been intensively studied for quantum systems without decoherence, but it is barely explored for systems subject to decoherence. In this paper, we develop a formulism to deal with this issue for topological insulators. The Hall conductance of a topological insulator coupled to an environment is derived, the derivation is based on a linear response theory developed for open systems in this paper. As an application, the Hall conductance of a two-band topological insulator and a two-dimensional lattice is presented and discussed.

Determination of intrinsic spin Hall angle in Pt

Energy Technology Data Exchange (ETDEWEB)

Wang, Yi; Deorani, Praveen; Qiu, Xuepeng; Kwon, Jae Hyun; Yang, Hyunsoo, E-mail: eleyang@nus.edu.sg [Department of Electrical and Computer Engineering, National University of Singapore, 117576 (Singapore)

2014-10-13

The spin Hall angle in Pt is evaluated in Pt/NiFe bilayers by spin torque ferromagnetic resonance measurements and is found to increase with increasing the NiFe thickness. To extract the intrinsic spin Hall angle in Pt by estimating the total spin current injected into NiFe from Pt, the NiFe thickness dependent measurements are performed and the spin diffusion in the NiFe layer is taken into account. The intrinsic spin Hall angle of Pt is determined to be 0.068 at room temperature and is found to be almost constant in the temperature range of 13–300 K.

Determination of intrinsic spin Hall angle in Pt

International Nuclear Information System (INIS)

Wang, Yi; Deorani, Praveen; Qiu, Xuepeng; Kwon, Jae Hyun; Yang, Hyunsoo

2014-01-01

The spin Hall angle in Pt is evaluated in Pt/NiFe bilayers by spin torque ferromagnetic resonance measurements and is found to increase with increasing the NiFe thickness. To extract the intrinsic spin Hall angle in Pt by estimating the total spin current injected into NiFe from Pt, the NiFe thickness dependent measurements are performed and the spin diffusion in the NiFe layer is taken into account. The intrinsic spin Hall angle of Pt is determined to be 0.068 at room temperature and is found to be almost constant in the temperature range of 13–300 K.

Fast surface waves in an ideal Hall-magnetohydrodynamic plasma slab

International Nuclear Information System (INIS)

Zhelyazkov, I.; Debosscher, A.; Goossens, M.

1996-01-01

The propagation of fast sausage and kink magnetohydrodynamic (MHD) surface waves in an ideal magnetized plasma slab is studied taking into account the Hall term in the generalized Ohm close-quote s law. It is found that the Hall effect modifies the dispersion characteristics of MHD surface modes when the Hall term scaling length is not negligible (less than, but comparable to the slab thickness). The dispersion relations for both modes have been derived for parallel propagation (along the ambient equilibrium magnetic field lines).The Hall term imposes some limits on the possible wave number range. It turns out that the space distribution of almost all perturbed quantities in sausage and kink surface waves with Hall effect is rather complicated as compared to that of usual fast MHD surface waves. The applicability to solar wind aspects of the results obtained, is briefly discussed. copyright 1996 American Institute of Physics

Migrants and Their Experiences of Time: Edward T. Hall Revisited

Directory of Open Access Journals (Sweden)

Elisabeth Schilling

2009-01-01

Full Text Available In this paper we reassess the scientific heritage of Edward T. HALL and his contribution to the area of intercultural communication. The key objectives of our study are to demonstrate the applicability of HALL's theory of culture to empirical research and to establish its compatibility with other methods. Specifically, we propose that Alfred SCHÜTZ's phenomenology of sociality be taken as an extension to HALL. The connection between HALL and SCHÜTZ is made possible by the mutual emphases on the temporal dimension of culture and the temporal aspects of migration. With these foci we analyze six narratives by two groups of migrants: German and Russian. By combining HALL's theory of the cultural time with SCHÜTZ's phenomenological perspective on time and the Other and then applying them to empirical data, we show the terms in which different cultures experience time. URN: urn:nbn:de:0114-fqs0901357

Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system

International Nuclear Information System (INIS)

Yoshimura, Koji; Nakamura, Isamu

2012-01-01

We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to ∼2μm diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.

Multi-wavelength study of PPDs using an OPO tunable pulse laser microscope system

Energy Technology Data Exchange (ETDEWEB)

Yoshimura, Koji, E-mail: koji.yoshimura@kek.jp [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan); Nakamura, Isamu [High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 (Japan)

2012-12-11

We have developed a new pulsed laser microscope system whose wavelength is continuously tunable from 410 nm to 2200 nm by using an optical parametric oscillator (OPO) laser system. The laser spot can be focused to {approx}2{mu}m diameter, small enough to measure pixel-by-pixel performance of PPDs (pixelated photon detectors). Using multi-wavelength laser light, we plan to probe PPDs at various depths, thanks to their different penetration lengths in the silicon layer. In this paper, details of the commissioning of the laser microscope system and pilot measurements on a PPD at several wavelengths will be presented.

Aspects of scanning force microscope probes and their effects on dimensional measurement

Energy Technology Data Exchange (ETDEWEB)

Yacoot, Andrew [National Physical Laboratory, Teddington, Middlesex TW11 0LW (United Kingdom); Koenders, Ludger [Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig (Germany)], E-mail: andrew.yacoot@npl.co.uk

2008-05-21

The review will describe the various scanning probe microscopy tips and cantilevers used today for scanning force microscopy and magnetic force microscopy. Work undertaken to quantify the properties of cantilevers and tips, e.g. shape and radius, is reviewed together with an overview of the various tip-sample interactions that affect dimensional measurements. (topical review)

Aspects of scanning force microscope probes and their effects on dimensional measurement

International Nuclear Information System (INIS)

Yacoot, Andrew; Koenders, Ludger

2008-01-01

The review will describe the various scanning probe microscopy tips and cantilevers used today for scanning force microscopy and magnetic force microscopy. Work undertaken to quantify the properties of cantilevers and tips, e.g. shape and radius, is reviewed together with an overview of the various tip-sample interactions that affect dimensional measurements. (topical review)

Critical current in the Integral Quantum Hall Effect

International Nuclear Information System (INIS)

Kostadinov, I.Z.

1985-11-01

A multiparticle theory of the Integral Quantum Hall Effect (IQHE) was constructed operating with pairs wave function as an order parameter. The IQHE is described with bosonic macroscopic states while the fractional QHE with fermionic ones. The calculation of the critical current and Hall conductivity temperature dependence is presented. (author)

Microscopic optoelectronic defectoscopy of solar cells

Directory of Open Access Journals (Sweden)

Dallaeva D.

2013-05-01

Full Text Available Scanning probe microscopes are powerful tool for micro- or nanoscale diagnostics of defects in crystalline silicon solar cells. Solar cell is a large p-n junction semiconductor device. Its quality is strongly damaged by the presence of defects. If the cell works under low reverse-biased voltage, defects emit a light in visible range. The suggested method combines three different measurements: electric noise measurement, local topography and near-field optical beam induced current and thus provides more complex information. To prove its feasibility, we have selected one defect (truncated pyramid in the sample, which emitted light under low reverse-biased voltage.

Visualizing tributyltin (TBT) in bacterial aggregates by specific rhodamine-based fluorescent probes.

Science.gov (United States)

Jin, Xilang; Hao, Likai; She, Mengyao; Obst, Martin; Kappler, Andreas; Yin, Bing; Liu, Ping; Li, Jianli; Wang, Lanying; Shi, Zhen

2015-01-01

Here we present the first examples of fluorescent and colorimetric probes for microscopic TBT imaging. The fluorescent probes are highly selective and sensitive to TBT and have successfully been applied for imaging of TBT in bacterial Rhodobacter ferrooxidans sp. strain SW2 cell-EPS-mineral aggregates and in cell suspensions of the marine cyanobacterium Synechococcus PCC 7002 by using confocal laser scanning microscopy. Copyright © 2014 Elsevier B.V. All rights reserved.

Preparation and quality test of superparamagnetic iron oxide labeled antisense oligodeoxynucleotide probe: a preliminary study.

Science.gov (United States)

Wen, Ming; Li, Bibo; Ouyang, Yu; Luo, Yi; Li, Shaolin

2009-06-01

Molecular imaging of tumor antisense gene techniques have been applied to the study of magnetic resonance (MR) gene imaging associated with malignant tumors. In this study, we designed, synthesized, and tested a novel molecular probe, in which the antisense oligodeoxynucleotide (ASODN) was labeled with superparamagnetic iron oxide (SPIO), and its efficiency was examined by in vitro MR imaging after SK-Br-3 mammary carcinoma cell lines (oncocytes) transfection. The SPIO-labeled ASODN probe was prepared through SPIO conjugated to ASODN using a chemical cross linking method. Its morphology and size were detected by atomic force microscope, size distribution were detected by laser granulometer, the conjugating rate and biological activity were determined by high performance liquid chromatography, and the stability was determined by polyacrylamide gel electrophoresis. After that, the probes were transfected into the SK-Br-3 oncocytes, cellular iron uptake was analyzed qualitatively at light and electron microscopy and was quantified at atomic absorption spectrometry, and the signal change of the transfected cells was observed and measured using MR imaging. The morphology of the SPIO-labeled ASODN probe was mostly spherical with well-distributed scattering, and the diameters were between 25 and 40 nm (95%) by atomic force microscope and laser granulometer, the conjugating rate of the probe was 99%. Moreover, this probe kept its activity under physiological conditions and could conjugate with antisense oligodeoxynucleotide. In addition, light microscopy revealed an intracellular uptake of iron oxides in the cytosol and electron microscopic studies revealed a lysosomal deposition of iron oxides in the transfected SK-Br-3 oncocytes by antisense probes, some of them gathered stacks, and the iron content of the group of transfected SK-Br-3 oncocytes by antisense probe is significantly higher (18.37 +/- 0.42 pg) than other contrast groups, the MR imaging showed that

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics.

Science.gov (United States)

Huang, Haiyun; Wang, Dejun; Xu, Yue

2015-10-27

This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS) technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW.

A Monolithic CMOS Magnetic Hall Sensor with High Sensitivity and Linearity Characteristics

Directory of Open Access Journals (Sweden)

Haiyun Huang

2015-10-01

Full Text Available This paper presents a fully integrated linear Hall sensor by means of 0.8 μm high voltage complementary metal-oxide semiconductor (CMOS technology. This monolithic Hall sensor chip features a highly sensitive horizontal switched Hall plate and an efficient signal conditioner using dynamic offset cancellation technique. An improved cross-like Hall plate achieves high magnetic sensitivity and low offset. A new spinning current modulator stabilizes the quiescent output voltage and improves the reliability of the signal conditioner. The tested results show that at the 5 V supply voltage, the maximum Hall output voltage of the monolithic Hall sensor microsystem, is up to ±2.1 V and the linearity of Hall output voltage is higher than 99% in the magnetic flux density range from ±5 mT to ±175 mT. The output equivalent residual offset is 0.48 mT and the static power consumption is 20 mW.

The ISOLDE hall

CERN Multimedia

Maximilien Brice

2002-01-01

Since 1992, after its move from the 600 MeV SC, ISOLDE is a customer of the Booster (then 1 GeV, now 1.4 GeV). The intense Booster beam (some 3E13 protons per pulse) is directed onto a target, from which a mixture of isotopes emanates. After ionization and electrostatic acceleration to 60 keV, they enter one of the 2 spectrometers (General Purpose Separator: GPS, and High Resolution Separator: HRS) from which the selected ions are directed to the experiments. The photos show: the REX-ISOLDE post accelerator; the mini-ball experiment; an overview of the ISOLDE hall. In the picture (_12) of the hall, the separators are behind the wall. From either of them, beams can be directed into any of the many beamlines towards the experiments, some of which are visible in the foreground. The elevated cubicle at the left is EBIS (Electron Beam Ion Source), which acts as a charge-state multiplier for the REX facility. The ions are further mass analzyzed and passed on to the linac which accelerates them to higher energies. T...

Simulation of Probe Position-Dependent Electron Energy-Loss Fine Structure

Energy Technology Data Exchange (ETDEWEB)

Oxley, M. P.; Kapetanakis, M. D.; Prange, Micah P.; Varela, M.; Pennycook, Stephen J.; Pantelides, Sokrates T.

2014-03-31

We present a theoretical framework for calculating probe-position-dependent electron energy-loss near-edge structure for the scanning transmission electron microscope by combining density functional theory with dynamical scattering theory. We show how simpler approaches to calculating near-edge structure fail to include the fundamental physics needed to understand the evolution of near-edge structure as a function of probe position and investigate the dependence of near-edge structure on probe size. It is within this framework that density functional theory should be presented, in order to ensure that variations of near-edge structure are truly due to local electronic structure and how much from the diffraction and focusing of the electron beam.

Prototype dining hall energy efficiency study

Energy Technology Data Exchange (ETDEWEB)

Mazzucchi, R.P.; Bailey, S.A.; Zimmerman, P.W.

1988-06-01

The energy consumption of food service facilities is among the highest of any commercial building type, owing to the special requirements for food preparation, sanitation, and ventilation. Consequently, the US Air Force Engineering and Services Center (AFESC) contracted with Pacific Northwest Laboratory (PNL) to collect and analyze end-use energy consumption data for a prototypical dining hall and make specific recommendations on cost-effective energy conservation options. This information will be used to establish or update criteria for dining hall designs and retrofits as appropriate. 6 refs., 21 figs., 23 tabs.

Proton knock-out in Hall A

International Nuclear Information System (INIS)

Jager, K. de

2003-01-01

Proton knock-out is studied in a broad program in Hall A at Jefferson Lab. The first experiment performed in Hall A studied the 16 O(e,e'p) reaction. Since then proton knock-out experiments have studied a variety of aspects of that reaction, from single-nucleon properties to its mechanism, such as final-state interactions and two-body currents, in nuclei from 2 H to 16 O. In this review the accomplishments of this program will be summarized and an outlook given of expected future results. (orig.)

Attainment of 40.5 pm spatial resolution using 300 kV scanning transmission electron microscope equipped with fifth-order aberration corrector.