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Sample records for scanning tunneling microscopic

  1. Femtosecond scanning tunneling microscope

    SciTech Connect

    Taylor, A.J.; Donati, G.P.; Rodriguez, G.; Gosnell, T.R.; Trugman, S.A.; Some, D.I.

    1998-11-01

    This is the final report of a three-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). By combining scanning tunneling microscopy with ultrafast optical techniques we have developed a novel tool to probe phenomena on atomic time and length scales. We have built and characterized an ultrafast scanning tunneling microscope in terms of temporal resolution, sensitivity and dynamic range. Using a novel photoconductive low-temperature-grown GaAs tip, we have achieved a temporal resolution of 1.5 picoseconds and a spatial resolution of 10 nanometers. This scanning tunneling microscope has both cryogenic and ultra-high vacuum capabilities, enabling the study of a wide range of important scientific problems.

  2. Scanning tunneling microscope nanoetching method

    DOEpatents

    Li, Yun-Zhong; Reifenberger, Ronald G.; Andres, Ronald P.

    1990-01-01

    A method is described for forming uniform nanometer sized depressions on the surface of a conducting substrate. A tunneling tip is used to apply tunneling current density sufficient to vaporize a localized area of the substrate surface. The resulting depressions or craters in the substrate surface can be formed in information encoding patterns readable with a scanning tunneling microscope.

  3. A Student-Built Scanning Tunneling Microscope

    ERIC Educational Resources Information Center

    Ekkens, Tom

    2015-01-01

    Many introductory and nanotechnology textbooks discuss the operation of various microscopes including atomic force (AFM), scanning tunneling (STM), and scanning electron microscopes (SEM). In a nanotechnology laboratory class, students frequently utilize microscopes to obtain data without a thought about the detailed operation of the tool itself.…

  4. A Student-Built Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Ekkens, Tom

    2015-12-01

    Many introductory and nanotechnology textbooks discuss the operation of various microscopes including atomic force (AFM), scanning tunneling (STM), and scanning electron microscopes (SEM). In a nanotechnology laboratory class, students frequently utilize microscopes to obtain data without a thought about the detailed operation of the tool itself. I wanted to give my students a deeper appreciation for the physics by having them build a simple scanning tunneling microscope. Initially, 15 hours of an upper-division laboratory class were devoted to building and operating the STM. As the build process was refined, the time commitment for this project has shrunk to nine hours. Using the method described in this paper, the project is now simple enough that it can be built and operated by students in the introductory class.

  5. Scanning tunneling microscope assembly, reactor, and system

    SciTech Connect

    Tao, Feng; Salmeron, Miquel; Somorjai, Gabor A

    2014-11-18

    An embodiment of a scanning tunneling microscope (STM) reactor includes a pressure vessel, an STM assembly, and three spring coupling objects. The pressure vessel includes a sealable port, an interior, and an exterior. An embodiment of an STM system includes a vacuum chamber, an STM reactor, and three springs. The three springs couple the STM reactor to the vacuum chamber and are operable to suspend the scanning tunneling microscope reactor within the interior of the vacuum chamber during operation of the STM reactor. An embodiment of an STM assembly includes a coarse displacement arrangement, a piezoelectric fine displacement scanning tube coupled to the coarse displacement arrangement, and a receiver. The piezoelectric fine displacement scanning tube is coupled to the coarse displacement arrangement. The receiver is coupled to the piezoelectric scanning tube and is operable to receive a tip holder, and the tip holder is operable to receive a tip.

  6. Atomistic constructions using a scanning tunneling microscope.

    NASA Astrophysics Data System (ADS)

    Deshpande, Aparna; Vaughn, Joel; Hla, Saw-Wai

    2007-03-01

    We demonstrate an atomic scale construction scheme, which is performed at an area as small as a few tens of nanometer square. In this atomic scale construction site, all the basic building blocks, single atoms, are extracted locally from the substrate using a scanning-tunneling-microscope tip. These extracted atoms are then precisely positioned on the surface to form desired structures. After the completion of the construction, the remaining debris are removed and the undesired holes near the construction site are filled with atoms/clusters to tidy up the area. This entire construction scheme closely resembles our real world construction process and can be considered as its atomic scale analog. This work is supported by NSF grant DMR-0304314 and US-DOE grant DE-FG02-02ER46012.

  7. A vertical coarse approach scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Drevniok, Benedict

    A Pan-style scanning tunneling microscope (STM), with a vertical coarse approach mechanism, was designed, built and tested. The microscope will be operated in ultra-high vacuum and also at cryogenic temperatures (8 K) inside a continuous flow cryostat. Fundamental differences in operating principle exist between the new microscope and the beetle-type inertial sliders [1] that have been the mainstay of the group for the last eight years. While Pan-style microscopes do already exist [2], they remain challenging to build, and an active area of research [3]. This system represents a bold departure from well-trodden paths, and will greatly expand the range of experiments that our group can perform. The operating principles of inertial piezoelectric motors are detailed. Design guidelines for a piezoelectric motor are given, and used in the design of the vertical coarse approach motor. A simple, inexpensive implementation for creating waveforms with an extremely fast fall time is discussed. Motor performance is tested, and a minimum step size of 20nm is found for frequencies ranging from 0 Hz to 3 kHz. The motor operates with high dynamic range: individual 20nm steps can be taken, as well as being able to move at a velocity of 0.4mm s-1. Little is known about the vibrational properties of Pan-style microscopes. Vibrational testing of the microscope revealed the expected scanner bending mode at 1.6 kHz (above the scanner bending mode of our beetles at 1.2 kHz), and a complicated response signal above this frequency. Custom extension springs for an eddy-current damping system are built and tested. A low resonant frequency of 1.8 Hz is found, which is ideal for the application. Initial testing of the STM in ambient conditions is performed on two different surfaces. A moire supermesh [4] with periodicity 3nm is observed on a highly-oriented pyrolytic graphite (HOPG) surface, and agrees well with previously published results. Using a flame-annealed Gold on mica surface, a low

  8. Manipulation of magnetic skyrmions with a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Wieser, R.; Shindou, R.; Xie, X. C.

    2017-02-01

    The dynamics of a single magnetic skyrmion in an atomic spin system under the influence of a scanning tunneling microscope is investigated by computer simulations solving the Landau-Lifshitz-Gilbert equation. Two possible scenarios are described: manipulation with aid of a spin-polarized tunneling current and by an electric field created by the scanning tunneling microscope. The dynamics during the creation and annihilation process is studied and the possibility to move single skyrmions is showed.

  9. Compact, single-tube scanning tunneling microscope with thermoelectric cooling

    NASA Astrophysics Data System (ADS)

    Jobbins, Matthew M.; Agostino, Christopher J.; Michel, Jolai D.; Gans, Ashley R.; Kandel, S. Alex

    2013-10-01

    We have designed and built a scanning tunneling microscope with a compact inertial-approach mechanism that fits inside the piezoelectric scanner tube. Rigid construction allows the microscope to be operated without the use of external vibration isolators or acoustic enclosures. Thermoelectric cooling and a water-ice bath are used to increase temperature stability when scanning under ambient conditions.

  10. Regular Scanning Tunneling Microscope Tips can be Intrinsically Chiral

    SciTech Connect

    Tierney, Heather L.; Murphy, Colin J.; Sykes, E. Charles H.

    2011-01-07

    We report our discovery that regular scanning tunneling microscope tips can themselves be chiral. This chirality leads to differences in electron tunneling efficiencies through left- and right-handed molecules, and, when using the tip to electrically excite molecular rotation, large differences in rotation rate were observed which correlated with molecular chirality. As scanning tunneling microscopy is a widely used technique, this result may have unforeseen consequences for the measurement of asymmetric surface phenomena in a variety of important fields.

  11. Design and calibration of a vacuum compatible scanning tunneling microscope

    NASA Technical Reports Server (NTRS)

    Abel, Phillip B.

    1990-01-01

    A vacuum compatible scanning tunneling microscope was designed and built, capable of imaging solid surfaces with atomic resolution. The single piezoelectric tube design is compact, and makes use of sample mounting stubs standard to a commercially available surface analysis system. Image collection and display is computer controlled, allowing storage of images for further analysis. Calibration results from atomic scale images are presented.

  12. Combined scanning tunneling and force microscope with fuzzy controlled feedback

    NASA Astrophysics Data System (ADS)

    Battiston, F. M.; Bammerlin, M.; Loppacher, Ch.; Guggisberg, M.; Lüthi, R.; Meyer, E.; Eggimann, F.; Güntherodt, H.-J.

    Decision-making logic based on fuzzy logic and an adaptive PI-controller was inserted into the feedback loop of a combined atomic force microscope/scanning tunneling microscope (AFM/STM), which is able to measure the frequency shift Δf of the cantilever-type spring and the mean tunneling current t simultanously. Depending on the conductivity of the surface the fuzzy logic controller decides whether it has to use the AFM feedback or the STM feedback. On conductive regions of the sample STM mode is used, whereas on poorly conducting regions the non-contact AFM mode is preferred. This allows one to scan over heterogenous surfaces avoiding a tip crash.

  13. Development of the tunneling junction simulation environment for scanning tunneling microscope evaluation

    NASA Astrophysics Data System (ADS)

    Gajewski, Krzysztof; Piasecki, Tomasz; Kopiec, Daniel; Gotszalk, Teodor

    2017-03-01

    Proper configuration of scanning tunneling microscope electronics plays an important role in the atomic scale resolution surface imaging. Device evaluation in the tunneling contact between scanning tip and sample may be prone to the surface quality or mechanical disturbances. Thus the use of tunneling junction simulator makes electronics testing more reliable and increases its repeatability. Here, we present the theoretical background enabling the proper selection of electronic components circuitry used as a tunneling junction simulator. We also show how to simulate mechanics related to the piezoelectric scanner, which is applied in real experiments. Practical use of the proposed simulator and its application in metrological characterization of the developed scanning tunneling microscope is also shown.

  14. Ultrahigh vacuum scanning electron microscope system combined with wide-movable scanning tunneling microscope

    SciTech Connect

    Kaneko, A.; Homma, Y.; Hibino, H.; Ogino, T.

    2005-08-15

    A surface analysis system has been newly developed with combination of ultrahigh vacuum scanning electron microscope (SEM) and wide-movable scanning tunneling microscope (STM). The basic performance is experimentally demonstrated. These SEM and STM images are clear enough to obtain details of surface structures. The STM unit moves horizontally over several millimeters by sliding motion of PZT actuators. The motion resolution is proved to be submicrometers. The STM tip mounted on another PZT scanner can be guided to a specific object on the sample surface during SEM observation. In the observation of a Si(111) surface rapidly cooled from high temperature, the STM tip was accurately guided to an isolated atomic step and slightly moved along it during SEM observation. The STM observation shows an asymmetry of the (7x7)-transformed region along the step between the upper and lower terraces. (7x7) bands continuously formed along the edge of terraces, while (7x7) domains distributed on the terraces slightly far from the step. These experiments show the wide-movable STM unit resolves a gap of observation area between SEM and STM and the system enables a specific object found in the SEM image to be observed easily by STM.

  15. Fabrication of metallic nanowires with a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Kramer, N.; Birk, H.; Jorritsma, J.; Schönenberger, C.

    1995-03-01

    A procedure to pattern thin metal films on a nanometer scale with a scanning tunneling microscope (STM) operating in air is reported. A 30 nm film of hydrogenated amorphous silicon (a-Si:H) is deposited on a 10 nm film of TaIr. Applying a negative voltage between the STM tip and the a-Si:H film causes the local oxidation of a-Si:H. The oxide which is formed is used as a mask to wet etch the not-oxidized a-Si:H and subsequently, the remaining pattern is transferred into the metal film by Ar ion milling. Metal wires as narrow as 40 nm have been fabricated. Since a-Si:H can be deposited in very thin layers on almost any substrate, the presented procedure can be applied to structure all kind of thin films on a nanometer scale.

  16. A high stability and repeatability electrochemical scanning tunneling microscope

    SciTech Connect

    Xia, Zhigang; Wang, Jihao; Lu, Qingyou; Hou, Yubin

    2014-12-15

    We present a home built electrochemical scanning tunneling microscope (ECSTM) with very high stability and repeatability. Its coarse approach is driven by a closely stacked piezo motor of GeckoDrive type with four rigid clamping points, which enhances the rigidity, compactness, and stability greatly. It can give high clarity atomic resolution images without sound and vibration isolations. Its drifting rates in XY and Z directions in solution are as low as 84 pm/min and 59 pm/min, respectively. In addition, repeatable coarse approaches in solution within 2 mm travel distance show a lateral deviation less than 50 nm. The gas environment can be well controlled to lower the evaporation rate of the cell, thus reducing the contamination and elongating the measurement time. Atomically resolved SO{sub 4}{sup 2−} image on Au (111) work electrode is demonstrated to show the performance of the ECSTM.

  17. Scanning tunneling microscope data acquisition and control in visual basic

    NASA Astrophysics Data System (ADS)

    Porter, T. L.

    1993-12-01

    A general purpose data acquisition and control system for scanning tunneling microscopy (STM) using Visual Basic is presented. This Windows hosted Visual Basic environment is highly desirable for use in STM image manipulation, storage, and printing, but in its standard form is not suitable for most data acquisition and display applications. Many of the inherent limitations in the Visual Basic language have been overcome by the use of direct calls to the Windows Application Program Interface. In this paper, we describe a general Visual Basic STM user interface and control system, and the extensions to the language using the Windows API needed to implement this system.

  18. Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip

    PubMed Central

    Ge, Jun-Yi; Gladilin, Vladimir N.; Tempere, Jacques; Xue, Cun; Devreese, Jozef T.; Van de Vondel, Joris; Zhou, Youhe; Moshchalkov, Victor V.

    2016-01-01

    Vortices play a crucial role in determining the properties of superconductors as well as their applications. Therefore, characterization and manipulation of vortices, especially at the single-vortex level, is of great importance. Among many techniques to study single vortices, scanning tunnelling microscopy (STM) stands out as a powerful tool, due to its ability to detect the local electronic states and high spatial resolution. However, local control of superconductivity as well as the manipulation of individual vortices with the STM tip is still lacking. Here we report a new function of the STM, namely to control the local pinning in a superconductor through the heating effect. Such effect allows us to quench the superconducting state at nanoscale, and leads to the growth of vortex clusters whose size can be controlled by the bias voltage. We also demonstrate the use of an STM tip to assemble single-quantum vortices into desired nanoscale configurations. PMID:27934960

  19. Nanoscale assembly of superconducting vortices with scanning tunnelling microscope tip.

    PubMed

    Ge, Jun-Yi; Gladilin, Vladimir N; Tempere, Jacques; Xue, Cun; Devreese, Jozef T; Van de Vondel, Joris; Zhou, Youhe; Moshchalkov, Victor V

    2016-12-09

    Vortices play a crucial role in determining the properties of superconductors as well as their applications. Therefore, characterization and manipulation of vortices, especially at the single-vortex level, is of great importance. Among many techniques to study single vortices, scanning tunnelling microscopy (STM) stands out as a powerful tool, due to its ability to detect the local electronic states and high spatial resolution. However, local control of superconductivity as well as the manipulation of individual vortices with the STM tip is still lacking. Here we report a new function of the STM, namely to control the local pinning in a superconductor through the heating effect. Such effect allows us to quench the superconducting state at nanoscale, and leads to the growth of vortex clusters whose size can be controlled by the bias voltage. We also demonstrate the use of an STM tip to assemble single-quantum vortices into desired nanoscale configurations.

  20. Note: Long-range scanning tunneling microscope for the study of nanostructures on insulating substrates

    SciTech Connect

    Molina-Mendoza, Aday J.; Rodrigo, José G.; Rubio-Bollinger, Gabino; Island, Joshua; Burzuri, Enrique; Zant, Herre S. J. van der; Agraït, Nicolás

    2014-02-15

    The scanning tunneling microscope (STM) is a powerful tool for studying the electronic properties at the atomic level, however, it is of relatively small scanning range and the fact that it can only operate on conducting samples prevents its application to study heterogeneous samples consisting of conducting and insulating regions. Here we present a long-range scanning tunneling microscope capable of detecting conducting micro and nanostructures on insulating substrates using a technique based on the capacitance between the tip and the sample and performing STM studies.

  1. Electronic Single Molecule Measurements with the Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Im, Jong One

    Richard Feynman said "There's plenty of room at the bottom". This inspired the techniques to improve the single molecule measurements. Since the first single molecule study was in 1961, it has been developed in various field and evolved into powerful tools to understand chemical and biological property of molecules. This thesis demonstrates electronic single molecule measurement with Scanning Tunneling Microscopy (STM) and two of applications of STM; Break Junction (BJ) and Recognition Tunneling (RT). First, the two series of carotenoid molecules with four different substituents were investigated to show how substituents relate to the conductance and molecular structure. The measured conductance by STM-BJ shows that Nitrogen induces molecular twist of phenyl distal substituents and conductivity increasing rather than Carbon. Also, the conductivity is adjustable by replacing the sort of residues at phenyl substituents. Next, amino acids and peptides were identified through STM-RT. The distribution of the intuitive features (such as amplitude or width) are mostly overlapped and gives only a little bit higher separation probability than random separation. By generating some features in frequency and cepstrum domain, the classification accuracy was dramatically increased. Because of large data size and many features, supporting vector machine (machine learning algorithm for big data) was used to identify the analyte from a data pool of all analytes RT data. The STM-RT opens a possibility of molecular sequencing in single molecule level. Similarly, carbohydrates were studied by STM-RT. Carbohydrates are difficult to read the sequence, due to their huge number of possible isomeric configurations. This study shows that STM-RT can identify not only isomers of mono-saccharides and disaccharides, but also various mono-saccharides from a data pool of eleven analytes. In addition, the binding affinity between recognition molecule and analyte was investigated by comparing with

  2. A cryogen-free variable temperature scanning tunneling microscope capable for inelastic electron tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhang, Shuai; Huang, Di; Wu, Shiwei

    While low temperature scanning tunneling microscope (STM) has become an indispensable research tool in surface science, its versatility is yet limited by the shortage or high cost of liquid helium. The makeshifts include the use of alternative cryogen (such as liquid nitrogen) at higher temperature or the development of helium liquefier system usually at departmental or campus wide. The ultimate solution would be the direct integration of a cryogen-free cryocooler based on GM or pulse tube closed cycle in the STM itself. However, the nasty mechanical vibration at low frequency intrinsic to cryocoolers has set the biggest obstacle because of the known challenges in vibration isolation required to high performance of STM. In this talk, we will present the design and performance of our home-built cryogen-free variable temperature STM at Fudan University. This system can obtain atomically sharp STM images and high resolution dI/dV spectra comparable to state-of-the-art low temperature STMs, but with no limitation on running hours. Moreover, we demonstrated the inelastic tunneling spectroscopy (STM-IETS) on a single CO molecule with a cryogen-free STM for the first time.

  3. Superconducting phonon spectroscopy using a low-temperature scanning tunneling microscope

    NASA Technical Reports Server (NTRS)

    Leduc, H. G.; Kaiser, W. J.; Hunt, B. D.; Bell, L. D.; Jaklevic, R. C.

    1989-01-01

    The low-temperature scanning tunneling microscope (STM) system described by LeDuc et al. (1987) was used to observe the phonon density of states effects in a superconductor. Using techniques based on those employed in macroscopic tunneling spectroscopy, electron tunneling current-voltage (I-V) spectra were measured for NbN and Pb, and dI/dV vs V spectra were measured using standard analog derivative techniques. I-V measurements on NbN and Pb samples under typical STM conditions showed no evidence for multiparticle tunneling effects.

  4. Partial sequencing of a single DNA molecule with a scanning tunnelling microscope

    NASA Astrophysics Data System (ADS)

    Tanaka, Hiroyuki; Kawai, Tomoji

    2009-08-01

    The scanning tunnelling microscope is capable of the real-space imaging and spectroscopy of molecules on an atomic scale. Numerous attempts have been made to use the scanning tunnelling microscope to sequence single DNA molecules, but difficulties in preparing samples of long-chain DNA molecules on surfaces, and problems in reproducing results have limited these experiments. Here, we report single-molecule DNA sequencing with a scanning tunnelling microscope by using an oblique pulse-injection method to deposit the molecules onto a copper surface. First, we show that guanine bases have a distinct electronic state that allows them to be distinguished from the other nucleic acid bases. Then, by comparing data on M13mp18, a single-stranded phage DNA, with a known base sequence, the `electronic fingerprint' of guanine bases in the DNA molecule is identified. These results show that it is possible to sequence individual guanine bases in real long-chain DNA molecules with high-resolution scanning tunnelling microscope imaging and spectroscopy.

  5. A cryogenic Quadraprobe scanning tunneling microscope system with fabrication capability for nanotransport research.

    PubMed

    Kim, Tae-Hwan; Wang, Zhouhang; Wendelken, John F; Weitering, Hanno H; Li, Wenzhi; Li, An-Ping

    2007-12-01

    We describe the development and the capabilities of an advanced system for nanoscale electrical transport studies. This system consists of a low temperature four-probe scanning tunneling microscope (STM) and a high-resolution scanning electron microscope coupled to a molecular-beam epitaxy sample preparation chamber. The four STM probes can be manipulated independently with subnanometer precision, enabling atomic resolution STM imaging and four-point electrical transport study of surface electronic systems and nanostructured materials at temperatures down to 10 K. Additionally, an integrated energy analyzer allows for scanning Auger microscopy to probe chemical species of nanostructures. Some testing results are presented.

  6. Correlation of scanning-tunneling-microscope image profiles and charge-density-wave amplitudes

    NASA Astrophysics Data System (ADS)

    Giambattista, B.; Johnson, A.; McNairy, W. W.; Slough, C. G.; Coleman, R. V.

    1988-08-01

    Scanning-tunneling-microscope (STM) studies of 4Hb-TaS2 and 4Hb-TaSe2 at 4.2 K show systematic correlation between the charge-density-wave (CDW) amplitude and the STM deflection. The 4Hb phases have both weak and strong CDW's in the trigonal prismatic and octahedral sandwiches, respectively. Scans on opposite faces of the same cleave allow a comparison of the STM response to the two types of CDW.

  7. Ionic channels in Langmuir-Blodgett films imaged by a scanning tunneling microscope.

    PubMed Central

    Kolomytkin, O V; Golubok, A O; Davydov, D N; Timofeev, V A; Vinogradova, S A; Tipisev SYa

    1991-01-01

    The molecular structure of channels formed by gramicidin A in a lipid membrane was imaged by a scanning tunneling microscope operating in air. The mono- and bimolecular films of lipid with gramicidin A were deposited onto a highly oriented pyrolitic graphite substrate by the Langmuir-Blodgett technique. It has been shown that under high concentration gramicidin A molecules can form in lipid films a quasi-regular, densely packed structure. Single gramicidin A molecules were imaged for the first time as well. The cavity of 0.4 +/- 0.05 nm in halfwidth was found on the scanning tunneling microscopy image of the gramicidin A molecule. The results of direct observation obtained by means of scanning tunneling microscope are in good agreement with the known molecular model of gramicidin A. It was shown that gramicidin A molecules can exist in a lipid monolayer as individual molecules or combined into clusters. The results demonstrate that scanning tunneling microscope can be used for high spatial resolution study of ionic channel structure. Images FIGURE 1 FIGURE 2 FIGURE 4 FIGURE 5 PMID:1712239

  8. Ferrimagnetic resonance excitation by light-wave mixing in a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Gutjahr-Löser, Th.; Krieger, W.; Walther, H.; Kirschner, J.

    1999-12-01

    Ferrimagnetic resonance is measured in a scanning tunneling microscope. The infrared light of two lasers is focused into the tunneling junction and a difference-frequency signal in the microwave region is generated. This microwave signal is used to excite spin waves in an yttrium-iron-garnet film with a thin Au capping. The coupling of the light to the tunneling junction is explained by an antenna mechanism. Characteristic antenna patterns of the angle-dependent receiving efficiency are obtained. The mixing of the two laser frequencies is due to the nonlinearity of the tunneling junction. The microwave signal obtained is absorbed in the ferromagnetic sample if the resonance condition is fulfilled. This method might allow the measurement of magnetic properties with a lateral resolution down to the nm scale.

  9. A variable-temperature nanostencil compatible with a low-temperature scanning tunneling microscope/atomic force microscope

    SciTech Connect

    Steurer, Wolfram Gross, Leo; Schlittler, Reto R.; Meyer, Gerhard

    2014-02-15

    We describe a nanostencil lithography tool capable of operating at variable temperatures down to 30 K. The setup is compatible with a combined low-temperature scanning tunneling microscope/atomic force microscope located within the same ultra-high-vacuum apparatus. The lateral movement capability of the mask allows the patterning of complex structures. To demonstrate operational functionality of the tool and estimate temperature drift and blurring, we fabricated LiF and NaCl nanostructures on Cu(111) at 77 K.

  10. Spectroscopy of Light Emission from a Scanning Tunneling Microscope in Air

    NASA Astrophysics Data System (ADS)

    Péchou, R.; Coratger, R.; Girardin, C.; Ajustron, F.; Beauvillain, J.

    1996-11-01

    Light emission has been detected at the tip-sample junction of a Scanning Tunneling Microscope (S.T.M.) in air on noble metallic surfaces. A spectroscopic study of emitted photons for Au-Au and PtIr-Au tunneling junctions is presented. The general aspect of the spectra depends on the materials used in the junctions; a study of the spectra as a function of tunneling current and surface bias voltage reveals similar and reproducible characteristics. Une émission de lumière a été détectée au niveau de la jonction pointe-surface d'un microscope à effet tunnel dans l'air sur des surfaces de métaux nobles. Une étude spectroscopique des photons émis par des jonctions tunnel Au-Au et PtIr-Au est présentée. L'aspect général des spectres dépend des matériaux utilisés ; une étude en fonction du courant tunnel et de la tension de polarisation de la jonction révéle des caractéristiques similaires et reproductibles.

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

    SciTech Connect

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

    2010-07-15

    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.

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

    SciTech Connect

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

    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.

  13. Design, operation, and housing of an ultrastable, low temperature, ultrahigh vacuum scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Ferris, J. H.; Kushmerick, J. G.; Johnson, J. A.; Yoshikawa Youngquist, M. G.; Kessinger, R. B.; Kingsbury, H. F.; Weiss, P. S.

    1998-07-01

    We have designed and constructed a low temperature, ultrahigh vacuum scanning tunneling microscope (STM), taking extreme measures to isolate the microscope from acoustic, vibrational, and electronic noise. We combined a 4 K STM with line-of-sight dosing to enable one to position the crystal surface in front of an impinging molecular beam as in scattering experiments. Due to the mechanical stability of the instrument and the minimal thermal drift associated with working at 4 K we are able to locate and to image repeatedly isolated adsorbates and atomic-scale structures, such as step edges, for extended periods days. The instrument has been designed for the topographic and spectroscopic characterization of atoms and molecules on metal and semiconductor surfaces, for the investigation of the mechanism by which the STM images adsorbates on surfaces, and for inelastic electron tunneling spectroscopy of single molecules.

  14. Microwave Frequency Comb from a Semiconductor in a Scanning Tunneling Microscope.

    PubMed

    Hagmann, Mark J; Yarotski, Dmitry A; Mousa, Marwan S

    2016-12-20

    Quasi-periodic excitation of the tunneling junction in a scanning tunneling microscope, by a mode-locked ultrafast laser, superimposes a regular sequence of 15 fs pulses on the DC tunneling current. In the frequency domain, this is a frequency comb with harmonics at integer multiples of the laser pulse repetition frequency. With a gold sample the 200th harmonic at 14.85 GHz has a signal-to-noise ratio of 25 dB, and the power at each harmonic varies inversely with the square of the frequency. Now we report the first measurements with a semiconductor where the laser photon energy must be less than the bandgap energy of the semiconductor; the microwave frequency comb must be measured within 200 μm of the tunneling junction; and the microwave power is 25 dB below that with a metal sample and falls off more rapidly at the higher harmonics. Our results suggest that the measured attenuation of the microwave harmonics is sensitive to the semiconductor spreading resistance within 1 nm of the tunneling junction. This approach may enable sub-nanometer carrier profiling of semiconductors without requiring the diamond nanoprobes in scanning spreading resistance microscopy.

  15. High frequency transmission to a junction of a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Hervé, M.; Peter, M.; Wulfhekel, W.

    2015-08-01

    We report on an easy method to calibrate the transmission of radio-frequency (rf) voltages to the tunneling junction of a scanning tunneling microscope. The transmission strongly depends on frequency, as the cabling shows frequency dependent damping and the impedance mismatch between the cable and the tunneling junction induces reflections. To first order, the current-voltage characteristic of the junction induces a rf tunneling current of the same frequency as the rf voltage. Omnipresent non-linearities of the current-voltage characteristic of the junction to second order, however, generate an additional rectified DC. A direct comparison between this current and the second derivative of the current-voltage curve allows to determine the rf transmission to the tunneling junction. The transmission data up to 2 GHz were used to compensate the rf damping such that at every frequency a constant amplitude at the tunneling junction could be realized expanding the bandwidth of the experiment from less then 100 MHz to 2 GHz.

  16. Plasmon-mediated circularly polarized luminescence of GaAs in a scanning tunneling microscope

    SciTech Connect

    Mühlenberend, Svenja; Gruyters, Markus; Berndt, Richard

    2015-12-14

    The electroluminescence from p-type GaAs(110) in a scanning tunneling microscope has been investigated at 6 K. Unexpectedly, high degrees of circular polarization have often been observed with ferromagnetic Ni tips and also with paramagnetic W and Ag tips. The data are interpreted in terms of two distinct excitation mechanisms. Electron injection generates intense luminescence with low polarization. Plasmon-mediated generation of electron-hole pairs leads to less intense emission, which, however, is highly polarized for many tips.

  17. Thickness determination of biological samples with a zeta-calibrated scanning tunneling microscope.

    PubMed Central

    Wang, Z H; Hartmann, T; Baumeister, W; Guckenberger, R

    1990-01-01

    A single-tube scanning tunneling microscope has been zeta-calibrated by using atomic steps of crystalline gold and was used for measuring the thickness of two biological samples, metal-coated as well as uncoated. The hexagonal surface layer of the bacterium Deinococcus radiodurans with an open network-type structure shows thickness values that are strongly influenced by the substrate and the preparation method. In contrast, the thickness of the purple membrane of Halobacterium halobium with its densely packed less-corrugated structure exhibits very little variation in thickness in coated preparations and the values obtained are in good agreement with x-ray data. Images PMID:2251276

  18. Tip-induced nanostructuring of alloy surfaces with an electrochemical scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Maupai, S.; Dakkouri, A. S.; Schmuki, P.

    2005-12-01

    Tip-induced nanostructuring with an electrochemical scanning tunneling microscope (EC-STM) was applied to alloy surfaces in order to resolve the reasons for the unusual stability of tip-induced metal clusters to anodic oxidation. Therefore Au thin films on glass and AuCu-alloy single crystals of different composition and surface orientation were used as substrates. The experiments give evidence that the three main factors for cluster formation and stability are the attractive interaction between tip and substrate, alloy formation during the cluster formation process as well as additional stabilization by adsorption of an underpotential deposition layer. Experimental results on the three aspects are presented and discussed.

  19. A low temperature scanning tunneling microscope for electronic and force spectroscopy.

    PubMed

    Smit, R H M; Grande, R; Lasanta, B; Riquelme, J J; Rubio-Bollinger, G; Agraït, N

    2007-11-01

    In this article, we describe and test a novel way to extend a low temperature scanning tunneling microscope with the capability to measure forces. The tuning fork that we use for this is optimized to have a high quality factor and frequency resolution. Moreover, as this technique is fully compatible with the use of bulk tips, it is possible to combine the force measurements with the use of superconductive or magnetic tips, advantageous for electronic spectroscopy. It also allows us to calibrate both the amplitude and the spring constant of the tuning fork easily, in situ and with high precision.

  20. Optical characterization of individual semiconductor nanostructures using a scanning tunneling microscope.

    PubMed

    Tsuruoka, Tohru; Ushioda, Sukekatsu

    2004-01-01

    By injecting low-energy minority carriers from the tip of a scanning tunneling microscope (STM) and analyzing the light emitted from the tip-sample gap of the STM, it is possible to study the optical and electronic properties of individual semiconductor nanostructures with an extremely high spatial resolution close to the atomic scale. This technique has been applied to investigate the transport properties of hot electrons injected into AlGaAs/GaAs quantum well structures and the optical properties of single self-assembled InAs/AlGaAs quantum dots. The physical principles, usefulness and future expectations of this novel technique are discussed.

  1. Current–Voltage Characterization of Individual As-Grown Nanowires Using a Scanning Tunneling Microscope

    PubMed Central

    2013-01-01

    Utilizing semiconductor nanowires for (opto)electronics requires exact knowledge of their current–voltage properties. We report accurate on-top imaging and I–V characterization of individual as-grown nanowires, using a subnanometer resolution scanning tunneling microscope with no need for additional microscopy tools, thus allowing versatile application. We form Ohmic contacts to InP and InAs nanowires without any sample processing, followed by quantitative measurements of diameter dependent I–V properties with a very small spread in measured values compared to standard techniques. PMID:24059470

  2. Note: long range and accurate measurement of deep trench microstructures by a specialized scanning tunneling microscope.

    PubMed

    Ju, Bing-Feng; Chen, Yuan-Liu; Zhang, Wei; Zhu, Wule; Jin, Chao; Fang, F Z

    2012-05-01

    A compact but practical scanning tunneling microscope (STM) with high aspect ratio and high depth capability has been specially developed. Long range scanning mechanism with tilt-adjustment stage is adopted for the purpose of adjusting the probe-sample relative angle to compensate the non-parallel effects. A periodical trench microstructure with a pitch of 10 μm has been successfully imaged with a long scanning range up to 2.0 mm. More innovatively, a deep trench with depth and step height of 23.0 μm has also been successfully measured, and slope angle of the sidewall can approximately achieve 67°. The probe can continuously climb the high step and exploring the trench bottom without tip crashing. The new STM could perform long range measurement for the deep trench and high step surfaces without image distortion. It enables accurate measurement and quality control of periodical trench microstructures.

  3. Haptic-STM: A human-in-the-loop interface to a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Perdigão, Luís M. A.; Saywell, Alex

    2011-07-01

    The operation of a haptic device interfaced with a scanning tunneling microscope (STM) is presented here. The user moves the STM tip in three dimensions by means of a stylus attached to the haptic instrument. The tunneling current measured by the STM is converted to a vertical force, applied to the stylus and felt by the user, with the user being incorporated into the feedback loop that controls the tip-surface distance. A haptic-STM interface of this nature allows the user to feel atomic features on the surface and facilitates the tactile manipulation of the adsorbate/substrate system. The operation of this device is demonstrated via the room temperature STM imaging of C60 molecules adsorbed on an Au(111) surface in ultra-high vacuum.

  4. Scanning tunneling microscope light emission: Effect of the strong dc field on junction plasmons

    NASA Astrophysics Data System (ADS)

    Kalathingal, Vijith; Dawson, Paul; Mitra, J.

    2016-07-01

    The observed energies of the localized surface plasmons (LSPs) excited at the tip-sample junction of a scanning tunneling microscope, as identified by spectral peaks in the light output, are very significantly redshifted with respect to calculations that use standard optical data for the tip and sample material, gold in this case. We argue that this anomaly depends on the extreme field in the sub-nm tunneling proximity of the tip and the sample, across which a dc bias (1-2 V) is applied. Finite element modeling analysis is presented of a gold nanosphere-plane (NS-P) combination in tunneling proximity and, crucially, in the presence of a high static electric field (˜109V /m ). It is argued that the strong dc field induces nonlinear corrections to the dielectric function of the gold via the effect of a large background polarizability through the nonlinear, χ(3 ) susceptibility contribution. When fed into the model system the modified optical data alters the LSP cavity modes of the NS-P system to indeed reveal a large redshift in energy compared to those of the virgin gold NS-P system. The net outcome may be regarded as equivalent to lowering the bulk plasmon energy, the physical interpretation being that the intense field of the tunneling environment leads to surface charge screening, effectively reducing the density of free electrons available to participate in the plasmon oscillations.

  5. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope

    NASA Astrophysics Data System (ADS)

    Burgess, Jacob A. J.; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-09-01

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface.

  6. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope

    PubMed Central

    Burgess, Jacob A.J.; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-01-01

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface. PMID:26359203

  7. Magnetic fingerprint of individual Fe4 molecular magnets under compression by a scanning tunnelling microscope.

    PubMed

    Burgess, Jacob A J; Malavolti, Luigi; Lanzilotto, Valeria; Mannini, Matteo; Yan, Shichao; Ninova, Silviya; Totti, Federico; Rolf-Pissarczyk, Steffen; Cornia, Andrea; Sessoli, Roberta; Loth, Sebastian

    2015-09-11

    Single-molecule magnets (SMMs) present a promising avenue to develop spintronic technologies. Addressing individual molecules with electrical leads in SMM-based spintronic devices remains a ubiquitous challenge: interactions with metallic electrodes can drastically modify the SMM's properties by charge transfer or through changes in the molecular structure. Here, we probe electrical transport through individual Fe4 SMMs using a scanning tunnelling microscope at 0.5 K. Correlation of topographic and spectroscopic information permits identification of the spin excitation fingerprint of intact Fe4 molecules. Building from this, we find that the exchange coupling strength within the molecule's magnetic core is significantly enhanced. First-principles calculations support the conclusion that this is the result of confinement of the molecule in the two-contact junction formed by the microscope tip and the sample surface.

  8. Scanning tunneling microscope design with a confocal small field permanent magnet.

    SciTech Connect

    Messina, P.; Pearson, J.; Vasserman, I.; Sasaki, S.; Moog, E.; Fradin, F.

    2008-09-01

    The field of ultra-sensitive measurements with scanning probes requires the design and construction of novel instruments. For example, the combination of radio frequency detection and scanning probe can be exploited to measure thermal properties and mechanical resonances at a very low scale. Very recent results by Komeda and Manassen (2008 Appl. Phys. Lett. 92 212506) on the detection of spin noise with the scanning tunneling microscopy (STM) have further expanded previous results reported by one of the authors of this manuscript (Messina et al 2007 J. Appl. Phys. 101 053916). In a previous publication, one of the authors used a new STM instrument (Messina et al J. Appl. Phys. 2007 101 053916 and Mannini et al 2007 Inorg. Chim. Acta 360 3837-42) to obtain the detection of electron spin noise (ESN) from individual paramagnetic adsorbates. The magnetic field homogeneity at the STM tip-sample region was limited. Furthermore, vacuum operation of the STM microscope was limited by the heat dissipation at the electromagnet and the radio frequency (RF) recovery electronics. We report here on a new STM head that incorporates a specially designed permanent magnet and in-built RF amplification system. The magnet provides both a better field homogeneity and freedom to operate the instrument in vacuum. The STM microscope is vacuum compatible, and vertical stability has been improved over the previous design (Messina et al 2007 J. Appl. Phys. 101 053916), despite the presence of a heat dissipative RF amplifier in the close vicinity of the STM tip.

  9. Calibration of tip and sample temperature of a scanning tunneling microscope using a superconductive sample

    SciTech Connect

    Stocker, Matthias; Pfeifer, Holger; Koslowski, Berndt

    2014-05-15

    The temperature of the electrodes is a crucial parameter in virtually all tunneling experiments. The temperature not only controls the thermodynamic state of the electrodes but also causes thermal broadening, which limits the energy resolution. Unfortunately, the construction of many scanning tunneling microscopes inherits a weak thermal link between tip and sample in order to make one side movable. Such, the temperature of that electrode is badly defined. Here, the authors present a procedure to calibrate the tip temperature by very simple means. The authors use a superconducting sample (Nb) and a standard tip made from W. Due to the asymmetry in the density of states of the superconductor (SC)—normal metal (NM) tunneling junction, the SC temperature controls predominantly the density of states while the NM controls the thermal smearing. By numerically simulating the I-V curves and numerically optimizing the tip temperature and the SC gap width, the tip temperature can be accurately deduced if the sample temperature is known or measureable. In our case, the temperature dependence of the SC gap may serve as a temperature sensor, leading to an accurate NM temperature even if the SC temperature is unknown.

  10. A scanning tunneling microscope capable of imaging specified micron-scale small samples

    NASA Astrophysics Data System (ADS)

    Tao, Wei; Cao, Yufei; Wang, Huafeng; Wang, Kaiyou; Lu, Qingyou

    2012-12-01

    We present a home-built scanning tunneling microscope (STM) which allows us to precisely position the tip on any specified small sample or sample feature of micron scale. The core structure is a stand-alone soft junction mechanical loop (SJML), in which a small piezoelectric tube scanner is mounted on a sliding piece and a "U"-like soft spring strip has its one end fixed to the sliding piece and its opposite end holding the tip pointing to the sample on the scanner. Here, the tip can be precisely aligned to a specified small sample of micron scale by adjusting the position of the spring-clamped sample on the scanner in the field of view of an optical microscope. The aligned SJML can be transferred to a piezoelectric inertial motor for coarse approach, during which the U-spring is pushed towards the sample, causing the tip to approach the pre-aligned small sample. We have successfully approached a hand cut tip that was made from 0.1 mm thin Pt/Ir wire to an isolated individual 32.5 × 32.5 μm2 graphite flake. Good atomic resolution images and high quality tunneling current spectra for that specified tiny flake are obtained in ambient conditions with high repeatability within one month showing high and long term stability of the new STM structure. In addition, frequency spectra of the tunneling current signals do not show outstanding tip mount related resonant frequency (low frequency), which further confirms the stability of the STM structure.

  11. A scanning tunneling microscope capable of imaging specified micron-scale small samples.

    PubMed

    Tao, Wei; Cao, Yufei; Wang, Huafeng; Wang, Kaiyou; Lu, Qingyou

    2012-12-01

    We present a home-built scanning tunneling microscope (STM) which allows us to precisely position the tip on any specified small sample or sample feature of micron scale. The core structure is a stand-alone soft junction mechanical loop (SJML), in which a small piezoelectric tube scanner is mounted on a sliding piece and a "U"-like soft spring strip has its one end fixed to the sliding piece and its opposite end holding the tip pointing to the sample on the scanner. Here, the tip can be precisely aligned to a specified small sample of micron scale by adjusting the position of the spring-clamped sample on the scanner in the field of view of an optical microscope. The aligned SJML can be transferred to a piezoelectric inertial motor for coarse approach, during which the U-spring is pushed towards the sample, causing the tip to approach the pre-aligned small sample. We have successfully approached a hand cut tip that was made from 0.1 mm thin Pt∕Ir wire to an isolated individual 32.5 × 32.5 μm(2) graphite flake. Good atomic resolution images and high quality tunneling current spectra for that specified tiny flake are obtained in ambient conditions with high repeatability within one month showing high and long term stability of the new STM structure. In addition, frequency spectra of the tunneling current signals do not show outstanding tip mount related resonant frequency (low frequency), which further confirms the stability of the STM structure.

  12. Invited Article: Autonomous assembly of atomically perfect nanostructures using a scanning tunneling microscope

    SciTech Connect

    Celotta, Robert J. E-mail: joseph.stroscio@nist.gov; Hess, Frank M.; Rutter, Gregory M.; Stroscio, Joseph A. E-mail: joseph.stroscio@nist.gov; Balakirsky, Stephen B.; Fein, Aaron P.

    2014-12-15

    A major goal of nanotechnology is to develop the capability to arrange matter at will by placing individual atoms at desired locations in a predetermined configuration to build a nanostructure with specific properties or function. The scanning tunneling microscope has demonstrated the ability to arrange the basic building blocks of matter, single atoms, in two-dimensional configurations. An array of various nanostructures has been assembled, which display the quantum mechanics of quantum confined geometries. The level of human interaction needed to physically locate the atom and bring it to the desired location limits this atom assembly technology. Here we report the use of autonomous atom assembly via path planning technology; this allows atomically perfect nanostructures to be assembled without the need for human intervention, resulting in precise constructions in shorter times. We demonstrate autonomous assembly by assembling various quantum confinement geometries using atoms and molecules and describe the benefits of this approach.

  13. Study on the Structure of C-Phycocyanin in Spirulina platensis with Scanning Tunneling Microscope.

    PubMed

    Zhang, Yu-Zhong; Shi, Dong-Xia; Zhou, Bai-Cheng; Zeng, Cheng-Kui; Pang, Shi-Jin

    1997-01-01

    The C-phycocyanin (C-PC) trimmer was isolated from the blue-green alga Spirulina platensis, and scanning tunneling microscope (STM) was used to investigate its structure. High resolution STM images of C-PC were obtained. From the STM images, it could be observed that the C-PC molecules were disk-like in shape and the subunits of C-PC arranged in ring-like pattern with a channel in the center. After filter treatment, the folding of the polypeptide chains could be seen clearly. This is the first time to observe directly the topography of phycobiliprotein, and the results showed STM to be a powerful tool for the structural study of phycobiliproteins.

  14. In situ scanning tunneling microscope tip treatment device for spin polarization imaging

    DOEpatents

    Li, An-Ping [Oak Ridge, TN; Jianxing, Ma [Oak Ridge, TN; Shen, Jian [Knoxville, TN

    2008-04-22

    A tip treatment device for use in an ultrahigh vacuum in situ scanning tunneling microscope (STM). The device provides spin polarization functionality to new or existing variable temperature STM systems. The tip treatment device readily converts a conventional STM to a spin-polarized tip, and thereby converts a standard STM system into a spin-polarized STM system. The tip treatment device also has functions of tip cleaning and tip flashing a STM tip to high temperature (>2000.degree. C.) in an extremely localized fashion. Tip coating functions can also be carried out, providing the tip sharp end with monolayers of coating materials including magnetic films. The device is also fully compatible with ultrahigh vacuum sample transfer setups.

  15. Low-temperature-compatible tunneling-current-assisted scanning microwave microscope utilizing a rigid coaxial resonator

    NASA Astrophysics Data System (ADS)

    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.

  16. Tip-geometry effects in circularly polarized light emission from a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Anisimovas, Egidijus; Johansson, Peter

    1999-02-01

    We present a calculation of the degree of circular polarization ρ, of the light emitted from a scanning tunneling microscope due to tip asymmetry. In order to take into account the essential geometrical features of an imperfect tip its shape is approximated by a tilted spheroid. We work in the nonretarded limit and use experimentally measured dielectric functions to describe the electromagnetic properties of the tip (W and Ir) and sample (noble metals) materials. The results show that the polarization can reach 20-30 % for what we think are moderately asymmetric tips. This result, as well as the strong dependence of ρ on the azimuthal observation angle, is in reasonable agreement with experimental findings [A. L. Vázquez de Parga and S. F. Alvarado, Europhys. Lett. 36, 577 (1996)].

  17. High-stability cryogenic scanning tunneling microscope based on a closed-cycle cryostat

    SciTech Connect

    Hackley, Jason D.; Kislitsyn, Dmitry A.; Beaman, Daniel K.; Nazin, George V.; Ulrich, Stefan

    2014-10-15

    We report on the design and operation of a cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Thermal drift analysis showed that under optimized conditions, the lateral stability of the STM scanner can be as low as 0.18 Å/h. Scanning Tunneling Spectroscopy measurements based on the lock-in technique were also carried out, and showed no detectable presence of noise from the closed-cycle cryostat. Using this cooling approach, temperatures as low as 16 K at the STM scanner have been achieved, with the complete cool-down of the system typically taking up to 12 h. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic scale.

  18. High-stability cryogenic scanning tunneling microscope based on a closed-cycle cryostat.

    PubMed

    Hackley, Jason D; Kislitsyn, Dmitry A; Beaman, Daniel K; Ulrich, Stefan; Nazin, George V

    2014-10-01

    We report on the design and operation of a cryogenic ultra-high vacuum (UHV) scanning tunneling microscope (STM) coupled to a closed-cycle cryostat (CCC). The STM is thermally linked to the CCC through helium exchange gas confined inside a volume enclosed by highly flexible rubber bellows. The STM is thus mechanically decoupled from the CCC, which results in a significant reduction of the mechanical noise transferred from the CCC to the STM. Noise analysis of the tunneling current shows current fluctuations up to 4% of the total current, which translates into tip-sample distance variations of up to 1.5 picometers. This noise level is sufficiently low for atomic-resolution imaging of a wide variety of surfaces. To demonstrate this, atomic-resolution images of Au(111) and NaCl(100)/Au(111) surfaces, as well as of carbon nanotubes deposited on Au(111), were obtained. Thermal drift analysis showed that under optimized conditions, the lateral stability of the STM scanner can be as low as 0.18 Å/h. Scanning Tunneling Spectroscopy measurements based on the lock-in technique were also carried out, and showed no detectable presence of noise from the closed-cycle cryostat. Using this cooling approach, temperatures as low as 16 K at the STM scanner have been achieved, with the complete cool-down of the system typically taking up to 12 h. These results demonstrate that the constructed CCC-coupled STM is a highly stable instrument capable of highly detailed spectroscopic investigations of materials and surfaces at the atomic scale.

  19. Refined tip preparation by electrochemical etching and ultrahigh vacuum treatment to obtain atomically sharp tips for scanning tunneling microscope and atomic force microscope.

    PubMed

    Hagedorn, Till; El Ouali, Mehdi; Paul, William; Oliver, David; Miyahara, Yoichi; Grütter, Peter

    2011-11-01

    A modification of the common electrochemical etching setup is presented. The described method reproducibly yields sharp tungsten tips for usage in the scanning tunneling microscope and tuning fork atomic force microscope. In situ treatment under ultrahigh vacuum (p ≤10(-10) mbar) conditions for cleaning and fine sharpening with minimal blunting is described. The structure of the microscopic apex of these tips is atomically resolved with field ion microscopy and cross checked with field emission.

  20. Refined tip preparation by electrochemical etching and ultrahigh vacuum treatment to obtain atomically sharp tips for scanning tunneling microscope and atomic force microscope

    SciTech Connect

    Hagedorn, Till; Ouali, Mehdi El; Paul, William; Oliver, David; Miyahara, Yoichi; Gruetter, Peter

    2011-11-15

    A modification of the common electrochemical etching setup is presented. The described method reproducibly yields sharp tungsten tips for usage in the scanning tunneling microscope and tuning fork atomic force microscope. In situ treatment under ultrahigh vacuum (p {<=}10{sup -10} mbar) conditions for cleaning and fine sharpening with minimal blunting is described. The structure of the microscopic apex of these tips is atomically resolved with field ion microscopy and cross checked with field emission.

  1. The mechanism of light emission from a scanning tunnelling microscope operating in air

    NASA Astrophysics Data System (ADS)

    Rogez, B.; Cao, S.; Dujardin, G.; Comtet, G.; Le Moal, E.; Mayne, A.; Boer-Duchemin, E.

    2016-11-01

    The scanning tunnelling microscope (STM) may be used as a low-energy, electrical nanosource of surface plasmon polaritons and light. In this article, we demonstrate that the optimum mode of operation of the STM for maximum photon emission is completely different in air than in vacuum. To this end, we investigate the emission of photons, the variation in the relative tip-sample distance and the measured current as a function of time for an STM operating in air. Contrary to the case of an STM operating in vacuum, the measured current between the tip and sample for an STM in air is very unstable (rapidly fluctuating in time) when the applied voltage between the tip and sample is in the ˜1.5-3 V range (i.e., in the energy range of visible photons). The photon emission occurs in short (50 μs) bursts when the STM tip is closest to the sample. The current instabilities are shown to be a key ingredient for producing intense light emission from an STM operating in air (photon emission rate several orders of magnitude higher than for stable current). These results are explained in terms of the interplay between the tunnel current and the electrochemical current in the ubiquitous thin water layer that exists when working in air.

  2. Modeling of Electronic Transport in Scanning Tunneling Microscope Tip-Carbon Nanotube Systems

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Kwak, Dochan (Technical Monitor)

    2000-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in a recent experiment with a scanning tunneling microscope tip and a carbon nanotube. We claim that there are two mechanical contact modes for a tip (metal) -nanotube (semiconductor) junction (1) with or (2) without a tiny vacuum gap (0.1 - 0.2 nm). With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube; the Schottky mechanism in (2) would result in I does not equal 0 only with V < 0 for an n-nanotube, and the bias polarities would be reversed for a p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type.

  3. A new variable temperature solution-solid interface scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Jahanbekam, Abdolreza; Mazur, Ursula; Hipps, K. W.

    2014-10-01

    We present a new solution-solid (SS) interface scanning tunneling microscope design that enables imaging at high temperatures with low thermal drift and with volatile solvents. In this new design, distinct from the conventional designs, the entire microscope is surrounded in a controlled-temperature and controlled-atmosphere chamber. This allows users to take measurements at high temperatures while minimizing thermal drift. By incorporating an open solution reservoir in the chamber, solvent evaporation from the sample is minimized; allowing users to use volatile solvents for temperature dependent studies at high temperatures. The new design enables the user to image at the SS interface with some volatile solvents for long periods of time (>24 h). An increase in the nonlinearity of the piezoelectric scanner in the lateral direction as a function of temperature is addressed. A temperature dependent study of cobalt(II) octaethylporphyrin (CoOEP) at the toluene/Au(111) interface has been performed with this instrument. It is demonstrated that the lattice parameters remain constant within experimental error from 24 °C to 75 °C. Similar quality images were obtained over the entire temperature range. We report the unit cell of CoOEP at the toluene/Au(111) interface (based on two molecules per unit cell) to be A = (1.36 ± 0.04) nm, B = (2.51 ± 0.04) nm, and α = 97° ± 2°.

  4. Systematic analyses of vibration noise of a vibration isolation system for high-resolution scanning tunneling microscopes.

    PubMed

    Iwaya, Katsuya; Shimizu, Ryota; Hashizume, Tomihiro; Hitosugi, Taro

    2011-08-01

    We designed and constructed an effective vibration isolation system for stable scanning tunneling microscopy measurements using a separate foundation and two vibration isolation stages (i.e., a combination of passive and active vibration isolation dampers). Systematic analyses of vibration data along the horizontal and vertical directions are present, including the vibration transfer functions of each stage and the overall vibration isolation system. To demonstrate the performance of the system, tunneling current noise measurements are conducted with and without the vibration isolation. Combining passive and active vibration isolation dampers successfully removes most of the vibration noise in the tunneling current up to 100 Hz. These comprehensive vibration noise data, along with details of the entire system, can be used to establish a clear guideline for building an effective vibration isolation system for various scanning probe microscopes and electron microscopes.

  5. Properties of Single Molecules: Manipulation, Dissociation and Synthesis with the Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Braun, Kai-Felix; Hla, Saw-Wai

    The fascinating advances in the manipulation of single atoms and molecules with the scanning tunneling microscope tip allow scientists to build atomic scale structures and to probe chemical and physical properties of matters at an atomic level. Due to these advances, the basic steps of a catalyzed chemical reaction such as dissociation, diffusion, adsorption, re-adsorption and bond formation processes can be performed by using the STM-tip. Here a short review of these steps and the techniques involved is presented. The lateral manipulation is used for the controlled positioning of atoms/molecules whereby only the tip- atom/molecule forces are employed. By measuring the tip-height signal during the manipulation, different modes of motion of the adparticle can be distinguished. Lower corrugated surfaces exhibit more complex motions than higher corrugated surfaces where the adparticle movement is confined to one dimension. Molecules have more degrees of freedom which allow a rotational motion or change in configuration. Even internal degrees of freedom can be detected and manipulated. The vertical manipulation not only allows the pick-up of adparticles and the subsequent transfer back to the surface, but also the manipulation of fragments of larger molecules. Effects due to the tunneling curent can be used for a controlled dissociation of chemical bonds as well as for the formation of new bonds. The combination of these manipulation techniques can induce chemical reactions at a single molecule level and construct new molecules. These achievements in STM manipulation of molecules open up new opportunities in nanochemistry and nanochemical technology. In this article, various STM manipulation techniques used for the single molecule reaction process are reviewed, and their impact on the future of nanoscience and nanotechnology is discussed.

  6. Nonlinearity, resonance, charging, and motion at the atomic scale studied with scanning tunneling microscopes

    NASA Astrophysics Data System (ADS)

    Tu, Xiuwen

    2008-10-01

    Several novel phenomena at the single-atom and single-molecule level occurring on the surfaces of single crystals were studied with home-built low temperature scanning tunneling microscopes. The results revealed intriguing properties of single atoms and single molecules, including nonlinearity, resonance, charging, and motion. First, negative differential resistance (NDR) was observed in the dI/dV spectra for single copper-phthalocyanine (CuPc) molecules adsorbed on one- and two-layer sodium bromide (NaBr), but not for single CuPc molecules adsorbed on three-layer NaBr, all grown on a NiAl(110) surface. This transition from NDR to the absence of NDR was explained as the result of competing effects in the double-barrier tunnel junction (DBTJ) and was reproduced in a calculation based on a resonant-tunneling model. Second, the nonlinearity of the STM junction due to a single manganese (Mn) atom or MnCO molecule adsorbed on a NiAl(110) surface was used to rectify microwave irradiation. The resulting rectification current was shown to be sensitive to the spin-splitting of the electronic states of the Mn atom and to the vibrations of the MnCO molecule. Next, the ordering of cesium (Cs) atoms adsorbed on a Au(111) surface and a NiAl(110) surface was imaged in real space. Because of charge transfer to the substrates, Cs adatoms were positively charged on both surfaces. Even at 12 K, Cs adatoms were able to move and adjust according to coverage. On Au(111), the Cs first layer had a quasi-hexagonal lattice and islands of the second Cs layer did not appear until the first was completed. On NiAl(110), a locally disordered Cs first layer was observed before a locally ordered layer appeared at higher coverages. The cation-pi interactions were then studied at the single molecular level. We were able to form cation-pi complexes such as Cs···DSB, Cs···DSB···Cs, Rb···DSB, and Rb···ZnEtiol controllably by manipulation with the STM tip. We could also separate these

  7. Electrochemical Nanolithography on Amorphous WO3 Thin Films Using Scanning Tunneling Microscope in Air

    NASA Astrophysics Data System (ADS)

    Qiu, Hong; Lu, Yong-Feng; Mai, Zhi-Hong

    2001-11-01

    Tungsten oxide (WO3) thin films have shown interesting properties as lithography resist materials. In this study, the scanning tunneling microscope (STM) was used in air for nanometer etching of α-WO3-x thin films, an n-type semiconductor. The current-voltage (I-V) curve was found to be affected by the water layer absorbed on the surface. For low voltage (< 3 V) with long duration (˜ 10 s) or high voltage pulse (> 3 V) with short pulsewidth (˜ 200 ms), holes were formed on the film surface at high humidity (> 70%) by applying a pulse voltage. A threshold voltage existed for hole formation. Higher pulse voltage and negative polarity corresponded to larger modified size. All the structures formed in STM images were topographical in nature by comparison with the AFM images. The hole formation was reasonably attributed to electrochemistry and high dissolution of WO3 in high pH solutions, which was co-manifested by links between the holes and eroded materials on the surface. Alkaline solutions instead of deionized water were chosen to act in the tip-surface gap. Alkaline ions being expelled from the tip due to electric polarity demonstrated the ion movement and their effect on etching. Lines of nanometer width were fabricated.

  8. Compact low temperature scanning tunneling microscope with in-situ sample preparation capability

    NASA Astrophysics Data System (ADS)

    Kim, Jungdae; Nam, Hyoungdo; Qin, Shengyong; Kim, Sang-ui; Schroeder, Allan; Eom, Daejin; Shih, Chih-Kang

    2015-09-01

    We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

  9. A 30 mK, 13.5 T scanning tunneling microscope with two independent tips

    SciTech Connect

    Roychowdhury, Anita; Gubrud, M. A.; Dana, R.; Dreyer, M.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2014-04-15

    We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated via spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of Cu{sub x}Bi{sub 2}Se{sub 3}. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.

  10. A 30 mK, 13.5 T scanning tunneling microscope with two independent tips

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Anita; Gubrud, M. A.; Dana, R.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.; Dreyer, M.

    2014-04-01

    We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated via spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of CuxBi2Se3. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.

  11. A 30 mK, 13.5 T scanning tunneling microscope with two independent tips.

    PubMed

    Roychowdhury, Anita; Gubrud, M A; Dana, R; Anderson, J R; Lobb, C J; Wellstood, F C; Dreyer, M

    2014-04-01

    We describe the design, construction, and performance of an ultra-low temperature, high-field scanning tunneling microscope (STM) with two independent tips. The STM is mounted on a dilution refrigerator and operates at a base temperature of 30 mK with magnetic fields of up to 13.5 T. We focus on the design of the two-tip STM head, as well as the sample transfer mechanism, which allows in situ transfer from an ultra high vacuum preparation chamber while the STM is at 1.5 K. Other design details such as the vibration isolation and rf-filtered wiring are also described. Their effectiveness is demonstrated via spectral current noise characteristics and the root mean square roughness of atomic resolution images. The high-field capability is shown by the magnetic field dependence of the superconducting gap of CuxBi2Se3. Finally, we present images and spectroscopy taken with superconducting Nb tips with the refrigerator at 35 mK that indicate that the effective temperature of our tips/sample is approximately 184 mK, corresponding to an energy resolution of 16 μeV.

  12. Compact low temperature scanning tunneling microscope with in-situ sample preparation capability

    SciTech Connect

    Kim, Jungdae; Nam, Hyoungdo; Schroeder, Allan; Shih, Chih-Kang; Qin, Shengyong; Kim, Sang-ui; Eom, Daejin

    2015-09-15

    We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

  13. Scanning tunneling microscope-quartz crystal microbalance study of temperature gradients at an asperity contact.

    PubMed

    Pan, L; Krim, J

    2013-01-01

    Investigations of atomic-scale friction frequently involve setups where a tip and substrate are initially at different temperatures. The temperature of the sliding interface upon contact has thus become a topic of interest. A method for detecting initial tip-sample temperature differences at an asperity contact is described, which consists of a scanning tunneling microscope (STM) tip in contact with the surface electrode of a quartz crystal microbalance (QCM). The technique makes use of the fact that a QCM is extremely sensitive to abrupt changes in temperature. In order to demonstrate the technique's capabilities, QCM frequency shifts were recorded for varying initial tip-substrate temperature differences as an STM tip was brought into and out of contact. The results are interpreted within the context of a recent model for thermal heat conduction at an asperity contact, and it is concluded that the transient frequency response is attributable to small changes in temperature close to the region of contact rather than a change in the overall temperature of the QCM itself. For the assumed model parameters, the results moreover reveal substantial temperature discontinuities at the boundary between the tip and the sample, for example, on the order of 10-15 °C for initial temperature differences of 20 °C.

  14. Compact low temperature scanning tunneling microscope with in-situ sample preparation capability.

    PubMed

    Kim, Jungdae; Nam, Hyoungdo; Qin, Shengyong; Kim, Sang-ui; Schroeder, Allan; Eom, Daejin; Shih, Chih-Kang

    2015-09-01

    We report on the design of a compact low temperature scanning tunneling microscope (STM) having in-situ sample preparation capability. The in-situ sample preparation chamber was designed to be compact allowing quick transfer of samples to the STM stage, which is ideal for preparing temperature sensitive samples such as ultra-thin metal films on semiconductor substrates. Conventional spring suspensions on the STM head often cause mechanical issues. To address this problem, we developed a simple vibration damper consisting of welded metal bellows and rubber pads. In addition, we developed a novel technique to ensure an ultra-high-vacuum (UHV) seal between the copper and stainless steel, which provides excellent reliability for cryostats operating in UHV. The performance of the STM was tested from 2 K to 77 K by using epitaxial thin Pb films on Si. Very high mechanical stability was achieved with clear atomic resolution even when using cryostats operating at 77 K. At 2 K, a clean superconducting gap was observed, and the spectrum was easily fit using the BCS density of states with negligible broadening.

  15. Nanosecond time-scale semiconductor photoexcitations probed by a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Gallagher, Mark J.; Ruskell, Todd G.; Chen, Dong; Sarid, Dror; Jenkinson, Howard

    1994-01-01

    The high-frequency response of scanning tunneling microscopy of a semiconductor is demonstrated by using the beat frequencies of the longitudinal modes of a HeNe laser at the tunneling junction. We present a comparison of the slow and fast optical response of photoexcited charge carriers in the layered structure semiconductors n-type MoS2 and p-type WSe2 using this method.

  16. Atomic force microscope-assisted scanning tunneling spectroscopy under ambient conditions.

    PubMed

    Vakhshouri, Amin; Hashimoto, Katsushi; Hirayama, Yoshiro

    2014-12-01

    We have developed a method of atomic force microscopy (AFM)-assisted scanning tunneling spectroscopy (STS) under ambient conditions. An AFM function is used for rapid access to a selected position prior to performing STS. The AFM feedback is further used to suppress vertical thermal drift of the tip-sample distance during spectroscopy, enabling flexible and stable spectroscopy measurements at room temperature.

  17. High vacuum tip-enhanced Raman spectroscope based on a scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Fang, Yurui; Zhang, Zhenglong; Sun, Mengtao

    2016-03-01

    In this paper, we present the construction of a high-vacuum tip-enhanced Raman spectroscopy (HV-TERS) system that allows in situ sample preparation and measurement. A detailed description of the prototype instrument is presented with experimental validation of its use and novel ex situ experimental results using the HV-TERS system. The HV-TERS system includes three chambers held under a 10-7 Pa vacuum. The three chambers are an analysis chamber, a sample preparation chamber, and a fast loading chamber. The analysis chamber is the core chamber and contains a scanning tunneling microscope (STM) and a Raman detector coupled with a 50 × 0.5 numerical aperture objective. The sample preparation chamber is used to produce single-crystalline metal and sub-monolayer molecular films by molecular beam epitaxy. The fast loading chamber allows ex situ preparation of samples for HV-TERS analysis. Atomic resolution can be achieved by the STM on highly ordered pyrolytic graphite. We demonstrate the measurement of localized temperature using the Stokes and anti-Stokes TERS signals from a monolayer of 1,2-benzenedithiol on a gold film using a gold tip. Additionally, plasmonic catalysis can be monitored label-free at the nanoscale using our device. Moreover, the HV-TERS experiments show simultaneously activated infrared and Raman vibrational modes, Fermi resonance, and some other non-linear effects that are not observed in atmospheric TERS experiments. The high spatial and spectral resolution and pure environment of high vacuum are beneficial for basic surface studies.

  18. Silicon-based molecular nanotechnology: Fabrication and characterization with the scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Hersam, Mark Christopher

    2000-10-01

    The importance of molecular nanotechnology has recently been underscored by increased media, public, and government awareness of the subject. This thesis examines several nanotechnology issues on the technologically significant Si(100) surface with the ultra-high vacuum scanning tunneling microscope (UHV-STM). Nanoscale studies have revealed that the in situ H-passivated Si(100) surface remains atomically pristine even after exposure to ambient conditions. The robustness of this surface suggests its use as a chemically inert resist layer. Using feedback-controlled lithography (FCL), individual hydrogen atoms can be removed from the Si(100)-2x1:H surface. The remaining dangling bond patterns serve as atomically precise templates upon which other materials can spontaneously self-assemble. By utilizing this selective chemistry in situ, several organic molecules (e.g., norbornadiene (NBE), copper phthalocyanine (CuPc), and C60) have been isolated. The mechanical, chemical, and electronic properties of these individual adsorbed species are then immediately detected with the STM. For CuPc, the spatial extent of charge transfer from the substrate to the adsorbate is measured as a function of binding orientation. When the CuPc is reduced with ammonia, single molecule rotation is observed. STM spectroscopic measurements on C 60 reveal intramolecular variations in the electronic density of states. For electronic applications, the application of lateral electrical fields to individual molecules is crucial. A fully compatible electrical contacting scheme based on p-n junctions will be presented. Efficient STM potentiometric location of these p-n junctions suggests their additional use as alignment markers. Beyond outlining advances in molecular nanoelectronics, this thesis will also draw connections between fundamental silicon research and current technology.

  19. An analysis of magnetization patterns measured using a magnetic force scanning tunneling microscope (abstract)

    NASA Astrophysics Data System (ADS)

    Burke, E. R.; Gomez, R. D.; Mayergoyz, I. D.

    1994-05-01

    In a previous paper, we made a complete analysis of the interaction between the probe tip of a magnetic force scanning tunneling microscope (MFSTM) and the magnetic fields emanating from a typical recorded pattern. In this paper we show how the magnetization distribution in the recorded media can be determined from the measurements by obtaining expressions for the magnetic fields from a Fourier series expansion for the recorded magnetizations. We have used these techniques to find the magnetic fields from many different distributions, including all those we could find in the literature. The probe tip displacement, which is the quantity measured using the MFSTM, can be calculated using these magnetic fields. The results can then be compared to the experimental data. For one set of experiments on high density recording we have found that the best fit is with a magnetization that has a modified arctan transition. The modification eliminates the discontinuity in the slope of the transitions as they are joined together, giving a more realistic representation of the magnetic distribution. The transition width can then be used as an adjustable parameter to find the best fit to the data. The MFSTM can, therefore, be used as a quantitative tool to find the magnetic recording transition widths. These theoretical techniques are not necessarily restricted to the use of a MFSTM, but can be applied to other problems in magnetic recording. For instance, we show how the probe tip displacement corresponds to the flux picked up by a conventional read head. The response of the head as a function of different magnetization patterns can then be studied and compared to experimental results. The measurable quantities are expressed in Fourier series but we show how these series can be easily evaluated with a PC and the appropriate software.

  20. Design and properties of a cryogenic dip-stick scanning tunneling microscope with capacitive coarse approach control.

    PubMed

    Schlegel, R; Hänke, T; Baumann, D; Kaiser, M; Nag, P K; Voigtländer, R; Lindackers, D; Büchner, B; Hess, C

    2014-01-01

    We present the design, setup, and operation of a new dip-stick scanning tunneling microscope. Its special design allows measurements in the temperature range from 4.7 K up to room temperature, where cryogenic vacuum conditions are maintained during the measurement. The system fits into every (4)He vessel with a bore of 50 mm, e.g., a transport dewar or a magnet bath cryostat. The microscope is equipped with a cleaving mechanism for cleaving single crystals in the whole temperature range and under cryogenic vacuum conditions. For the tip approach, a capacitive automated coarse approach is implemented. We present test measurements on the charge density wave system 2H-NbSe2 and the superconductor LiFeAs which demonstrate scanning tunneling microscopy and spectroscopy data acquisition with high stability, high spatial resolution at variable temperatures and in high magnetic fields.

  1. Development of Near-Field Microwave Microscope with the Functionality of Scanning Tunneling Spectroscopy

    NASA Astrophysics Data System (ADS)

    Machida, Tadashi; Gaifullin, Marat B.; Ooi, Shuuich; Kato, Takuya; Sakata, Hideaki; Hirata, Kazuto

    2010-11-01

    We describe the details of an original near-field scanning microwave microscope, developed for simultaneous measurements of local density-of-states (LDOS) and local ohmic losses (LOL). Improving microwave detection systems, we have succeeded in distinguishing the LDOS and LOL even between two low resistance materials; gold and highly orientated pyrolitic graphite. The experimental data indicate that our microscope holds a capability to investigate both LDOS and LOL in nanoscale.

  2. A compact sub-Kelvin ultrahigh vacuum scanning tunneling microscope with high energy resolution and high stability.

    PubMed

    Zhang, L; Miyamachi, T; Tomanić, T; Dehm, R; Wulfhekel, W

    2011-10-01

    We designed a scanning tunneling microscope working at sub-Kelvin temperatures in ultrahigh vacuum (UHV) in order to study the magnetic properties on the nanoscale. An entirely homebuilt three-stage cryostat is used to cool down the microscope head. The first stage is cooled with liquid nitrogen, the second stage with liquid (4)He. The third stage uses a closed-cycle Joule-Thomson refrigerator of a cooling power of 1 mW. A base temperature of 930 mK at the microscope head was achieved using expansion of (4)He, which can be reduced to ≈400 mK when using (3)He. The cryostat has a low liquid helium consumption of only 38 ml/h and standing times of up to 280 h. The fast cooling down of the samples (3 h) guarantees high sample throughput. Test experiments with a superconducting tip show a high energy resolution of 0.3 meV when performing scanning tunneling spectroscopy. The vertical stability of the tunnel junction is well below 1 pm (peak to peak) and the electric noise floor of tunneling current is about 6fA/√Hz. Atomic resolution with a tunneling current of 1 pA and 1 mV was achieved on Au(111). The lateral drift of the microscope at stable temperature is below 20 pm/h. A superconducting spilt-coil magnet allows to apply an out-of-plane magnetic field of up to 3 T at the sample surface. The flux vortices of a Nb(110) sample were clearly resolved in a map of differential conductance at 1.1 K and a magnetic field of 0.21 T. The setup is designed for in situ preparation of tip and samples under UHV condition.

  3. The Nanomanipulator: a Virtual-Reality Interface to a Scanning Tunneling Microscope.

    NASA Astrophysics Data System (ADS)

    Taylor, Russell Morton, II

    We have developed a virtual-reality interface to a scanning tunneling microscope (STM); the resulting system is called the Nanomanipulator. The user interface comprises a stereoscopic color head-mounted display, a force-feedback remote manipulator master station, and a high-performance graphics computer. It provides the illusion of a surface floating in space in front of the user. The user's hand gestures are translated into commands that are sent to the STM in real time; the returned video and haptic signals allow the user to see and feel the surface topography and to control the timing and location of voltage pulses applied between the tip of the STM probe and the sample under study. My thesis is that a virtual-reality interface is a powerful and effective user interface to an STM--allowing qualitatively different types of experiments to be performed. The success of our investigations using this system demonstrates the validity of the thesis. We have used the Nanomanipulator to examine various surfaces and to perform surface modification experiments. This investigation has led to new insight into the meaning of certain surface features and into the mechanisms by which voltage pulses change the tip and sample. These insights were the direct results of the real-time visualization and the more interactive nature of our system compared to standard methods. The key to the success of the Nanomanipulator system is that it provides an intuitive two-way interface to the instrument. Raw data from an STM is not in a format easily understood by a scientist, and the Etch-a-Sketch type of controls required for positioning an STM tip are neither natural nor familiar to a user. The Nanomanipulator system acts as a translator between the instrument and the scientist, allowing the scientist to concentrate on interacting with the surface under study rather than on the computer interface or the STM itself. This system seeks to put the scientists on the surface, in control, while the

  4. A Scanning Tunneling Microscope at the Milli-Kelvin, High Magnetic Field Frontier

    NASA Astrophysics Data System (ADS)

    Zhou, Brian B.

    The ability to access lower temperatures and higher magnetic fields has precipitated breakthroughs in our understanding of physical matter, revealing novel effects such as superconductivity, the integer and fractional quantum Hall effects, and single spin magnetism. Extending the scanning tunneling microscope (STM) to the extremity of the B-T phase space provides unique insight on these phenomena both at the atomic level and with spectroscopic power. In this thesis, I describe the design and operation of a full-featured, dilution refrigerator-based STM capable of sample preparation in ultra-high vacuum (UHV) and spectroscopic mapping with an electronic temperature of 240 mK in fields up to 14 T. I detail technical solutions to overcome the stringent requirements on vibration isolation, electronic noise, and mechanical design necessary to successfully integrate the triad of the STM, UHV, and dilution refrigeration. Measurements of the heavy fermion superconductor CeCoIn5 ( Tc = 2.3 K) directly leverage the resulting combination of ultra-low temperature and atomic resolution to identify its Cooper pairing to be of dx2-y2 symmetry. Spectroscopic and quasiparticle interference measurements isolate a Kondo-hybridized, heavy effective mass band near the Fermi level, from which nodal superconductivity emerges in CeCoIn5 in coexistence with an independent pseudogap. Secondly, the versatility of this instrument is demonstrated through measurements of the three-dimensional Dirac semimetal Cd3As2 up to the maximum magnetic field. Through high resolution Landau level spectroscopy, the dispersion of the conduction band is shown to be Dirac-like over an unexpectedly extended regime, and its two-fold degeneracy to be lifted in field through a combination of orbital and Zeeman effects. Indeed, these two experiments on CeCoIn5 and Cd3 As2 glimpse the new era of nano-scale materials research, spanning superconductivity, topological properties, and single spin phenomena, made

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

    SciTech Connect

    Ge, Jian-Feng; Liu, Zhi-Long; Gao, Chun-Lei; Qian, Dong; Liu, Canhua E-mail: jfjia@sjtu.edu.cn; Jia, Jin-Feng E-mail: jfjia@sjtu.edu.cn

    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.

  6. Ultrafast scanning tunneling microscopy

    SciTech Connect

    Botkin, D.A. |

    1995-09-01

    I have developed an ultrafast scanning tunneling microscope (USTM) based on uniting stroboscopic methods of ultrafast optics and scanned probe microscopy to obtain nanometer spatial resolution and sub-picosecond temporal resolution. USTM increases the achievable time resolution of a STM by more than 6 orders of magnitude; this should enable exploration of mesoscopic and nanometer size systems on time scales corresponding to the period or decay of fundamental excitations. USTM consists of a photoconductive switch with subpicosecond response time in series with the tip of a STM. An optical pulse from a modelocked laser activates the switch to create a gate for the tunneling current, while a second laser pulse on the sample initiates a dynamic process which affects the tunneling current. By sending a large sequence of identical pulse pairs and measuring the average tunnel current as a function of the relative time delay between the pulses in each pair, one can map the time evolution of the surface process. USTM was used to measure the broadband response of the STM`s atomic size tunnel barrier in frequencies from tens to hundreds of GHz. The USTM signal amplitude decays linearly with the tunnel junction conductance, so the spatial resolution of the time-resolved signal is comparable to that of a conventional STM. Geometrical capacitance of the junction does not appear to play an important role in the measurement, but a capacitive effect intimately related to tunneling contributes to the measured signals and may limit the ultimate resolution of the USTM.

  7. A high-stability scanning tunneling microscope achieved by an isolated tiny scanner with low voltage imaging capability

    SciTech Connect

    Wang, Qi; Wang, Junting; Lu, Qingyou; Hou, Yubin

    2013-11-15

    We present a novel homebuilt scanning tunneling microscope (STM) with high quality atomic resolution. It is equipped with a small but powerful GeckoDrive piezoelectric motor which drives a miniature and detachable scanning part to implement coarse approach. The scanning part is a tiny piezoelectric tube scanner (industry type: PZT-8, whose d{sub 31} coefficient is one of the lowest) housed in a slightly bigger polished sapphire tube, which is riding on and spring clamped against the knife edges of a tungsten slot. The STM so constructed shows low back-lashing and drifting and high repeatability and immunity to external vibrations. These are confirmed by its low imaging voltages, low distortions in the spiral scanned images, and high atomic resolution quality even when the STM is placed on the ground of the fifth floor without any external or internal vibration isolation devices.

  8. A high-stability scanning tunneling microscope achieved by an isolated tiny scanner with low voltage imaging capability

    NASA Astrophysics Data System (ADS)

    Wang, Qi; Hou, Yubin; Wang, Junting; Lu, Qingyou

    2013-11-01

    We present a novel homebuilt scanning tunneling microscope (STM) with high quality atomic resolution. It is equipped with a small but powerful GeckoDrive piezoelectric motor which drives a miniature and detachable scanning part to implement coarse approach. The scanning part is a tiny piezoelectric tube scanner (industry type: PZT-8, whose d31 coefficient is one of the lowest) housed in a slightly bigger polished sapphire tube, which is riding on and spring clamped against the knife edges of a tungsten slot. The STM so constructed shows low back-lashing and drifting and high repeatability and immunity to external vibrations. These are confirmed by its low imaging voltages, low distortions in the spiral scanned images, and high atomic resolution quality even when the STM is placed on the ground of the fifth floor without any external or internal vibration isolation devices.

  9. Control of the Residual Sub-Electronic Charge on a Mesoscopic Conductor by Means of a Scanning Tunneling Microscope Tip

    DTIC Science & Technology

    1994-03-07

    6] A. P. Fein, J . R. Kirtley, and R. M. Feenstra, Rev. Scient . Instrum . 58,1806 (1987). PUBLICATIONS P1. Z. Y. Rong, A. Chang, L. F. Cohen, and E. L...CHARGE ON A MESOSCOPIC CONDUCTOR BY MEANS OF A SCANNING TUNNELING MICROSCOPE TIP Final Technical Rep2ort. ONR Research Grant N00014-90- J -1845 Grant Title...Polytechnic University, Six Metrotech Center, Brooklyn, NY 11201 Prepared March 7, 1994 by E. L. Wolf V/ j - 06- 06- I. Introduction The topic of research

  10. Analysis of photon-scanning tunneling microscope images of inhomogeneous samples: determination of the local refractive index of channel waveguides

    NASA Astrophysics Data System (ADS)

    Bourillot, E.; de Fornel, F.; Goudonnet, J. P.; Persegol, D.; Kevorkian, A.; Delacourt, D.

    1995-01-01

    Channel waveguides are imaged by a photon-scanning tunneling microscope (PSTM). The polarization of the light and its orientation with respect to the guide axis are shown to be very important parameters in the analysis of the images of such samples. We simulated image formation for the plane of incidence parallel to the axis of the guide. Our theoretical results are qualitatively in agreement with our measurements. These results show the ability of the PSTM to give information about the local refractive-index variations of a sample.

  11. Development of a Millikelvin dual-tip Josephson scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Anita

    In this thesis, I first describe the design and construction of a dual-tip millikelvin STM system. The STM is mounted on a dilution refrigerator and the setup includes vibration isolation, rf-filtered wiring, an ultra high vacuum (UHV) sample preparation chamber and sample transfer mechanism. Next I describe a novel superconducting tip fabrication technique. My technique involves dry-etching sections of 250 mum diameter Nb wire with an SF6 plasma in a reactive ion etcher. I present data taken with these tips on various samples at temperatures ranging from 30 mK to 9 K. My results demonstrate that the tips are superconducting, achieve good spectroscopic energy resolution, are mechanically robust over long time periods, and are atomically sharp. I also show data characterizing the performance of our system. This data is in the form of atomic resolution images, spectroscopy, noise spectra and simultaneous scans taken with both tips of the STM. I used these to examine the tip-sample stability, cross talk between the two tips, and to extract the effective noise temperature (˜185 mK) of the sample by fitting the spectroscopy data to a voltage noise model. Finally, I present spectroscopy data taken with a Nb tip on a Nb(100) sample at 30 mK. The enhanced spectroscopic resolution at this temperature allowed me to resolve peaks in the fluctuation-dominated supercurrent at sub-gap voltages. My analysis indicates that these peaks are due to the incoherent tunneling of Cooper pairs at resonant frequencies of the STM's electromagnetic environment. By measuring the response of the STM junction to microwaves, I identified the charge carriers in this regime as Cooper pairs with charge 2e. The amplitude of the response current scales as the square of the Bessel functions, indicating that the pair tunneling originates from photon assisted tunneling in the incoherent regime, rather than the more conventionally observed Shapiro steps in the coherent regime.

  12. Theoretical Analysis of a Dual-Probe Scanning Tunneling Microscope Setup on Graphene

    NASA Astrophysics Data System (ADS)

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

    2014-03-01

    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 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.

  13. Scanning tunneling microscope observation of the phosphatidylserine domains in the phosphatidylcholine monolayer.

    PubMed

    Matsunaga, Soichiro; Yamada, Taro; Kobayashi, Toshihide; Kawai, Maki

    2015-05-19

    A mixed monolayer of 1,2-dihexanoyl-sn-glycero-3-phospho-l-serine (DHPS) and 1,2-dihexanoyl-sn-glycero-3-phosphocholine (DHPC) on an 1-octanethiol-modified gold substrate was visualized on the nanometer scale using in situ scanning tunneling microscopy (STM) in aqueous solution. DHPS clusters were evident as spotty domains. STM enabled us to distinguish DHPS molecules from DHPC molecules depending on their electronic structures. The signal of the DHPS domains was abolished by neutralization with Ca(2+). The addition of the PS + Ca(2+)-binding protein of annexin V to the Ca(2+)-treated monolayer gave a number of spots corresponding to a single annexin V molecule.

  14. An atomic resolution scanning tunneling microscope that applies external tensile stress and strain in an ultrahigh vacuum

    NASA Astrophysics Data System (ADS)

    Fujita, D.; Kitahara, M.; Onishi, K.; Sagisaka, K.

    2008-01-01

    We have developed an ultrahigh vacuum scanning tunneling microscope with an in situ external stress application capability in order to determine the effects of stress and strain on surface atomistic structures. It is necessary to understand these effects because controlling them will be a key technology that will very likely be used in future nanometer-scale fabrication processes. We used our microscope to demonstrate atomic resolution imaging under external tensile stress and strain on the surfaces of wafers of Si(111) and Si(001). We also successfully observed domain redistribution induced by applying uniaxial stress at an elevated temperature on the surface of a wafer of vicinal Si(100). We confirmed that domains for which an applied tensile stress is directed along the dimer bond become less stable and shrink. This suggests that it may be feasible to fabricate single domain surfaces in a process that controls surface stress and strain.

  15. Current-induced magnetization switching with a spin-polarized scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Krause, Stefan

    2008-03-01

    In present data storage applications magnetic nanostructures are switched by external magnetic fields. Due to their non-local character, however, cross-talk between adjacent nanomagnets may occur. An elegant method to circumvent this problem is magnetization switching by spin-polarized currents, as observed in GMR,1] as well as in TMR,2] studies. However, the layered structures of these devices do not provide any insight to the details of the spatial distribution of the switching processes. Spin-polarized scanning tunneling microscopy (SP-STM) is a well-established tool to reveal the magnetic structure of surfaces at spatial resolution down to the atomic scale. Besides, SP-STM takes advantage of a perfect TMR junction consisting of an isolating vacuum barrier separating two magnetic electrodes, which are represented by the foremost tip atom and the sample. Our experiments demonstrate that SP-STM serves as a tool to manipulate the switching behavior of uniaxial superparamagnetic nanoislands,3]. Furthermore, we show how SP-STM can be used to switch the magnetization of quasistable magnetic nanoislands at low temperature (T=31,). Besides its scientific relevance to investigate the details of current-induced magnetization switching (CIMS), this technique opens perspectives for future data storage technologies based on SP-STM. [1] J. A. Katine et al., Phys. Rev. Lett. 84, 3149 (2000). [2] Y. Liu et al., Appl. Phys. Lett. 82, 2871 (2003). [3] S. Krause et al., Science 317, 1537 (2007).

  16. Pattern Generation below 0.1 micron by Localized Chemical Vapor Deposition with the Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Lozanne, Alex

    1994-12-01

    Nowadays there are many techniques for nanofabrication, some of which are well established. The scanning tunneling microscope (STM) is the newest tool for making nanostructures, even down to the atomic scale, but it is not yet clear which applications will benefit from it. We have developed a technique that combines STM and chemical vapor deposition (CVD): the idea is to break CVD precursor gases with the electrons from the STM. This has the attractive feature of obtaining the highest resolution possible together with minimal damage to the substrate or existing structures. The gases that have been used with this technique include trimethylaluminum, dimethylcadmium, tungsten hexafluoride, nickel tetracarbonyl, and iron pentacarbonyl. Thus far this technique has produced metallic lines that are only 35 nm wide and dots that are 8 nm in diameter.

  17. Electrical conduction of organic ultrathin films evaluated by an independently driven double-tip scanning tunneling microscope.

    PubMed

    Takami, K; Tsuruta, S; Miyake, Y; Akai-Kasaya, M; Saito, A; Aono, M; Kuwahara, Y

    2011-11-02

    The electrical transport properties of organic thin films within the micrometer scale have been evaluated by a laboratory-built independently driven double-tip scanning tunneling microscope, operating under ambient conditions. The two tips were used as point contact electrodes, and current in the range from 0.1 pA to 100 nA flowing between the two tips through the material can be detected. We demonstrated two-dimensional contour mapping of the electrical resistance on a poly(3-octylthiophene) thin films as shown below. The obtained contour map clearly provided an image of two-dimensional electrical conductance between two point electrodes on the poly(3-octylthiophene) thin film. The conductivity of the thin film was estimated to be (1-8) × 10(-6) S cm(-1). Future prospects and the desired development of multiprobe STMs are also discussed.

  18. Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy.

    PubMed

    Albers, Boris J; Liebmann, Marcus; Schwendemann, Todd C; Baykara, Mehmet Z; Heyde, Markus; Salmeron, Miquel; Altman, Eric I; Schwarz, Udo D

    2008-03-01

    We present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.

  19. Combined low-temperature scanning tunneling/atomic force microscope for atomic resolution imaging and site-specific force spectroscopy

    SciTech Connect

    Schwarz, Udo; Albers, Boris J.; Liebmann, Marcus; Schwendemann, Todd C.; Baykara, Mehmet Z.; Heyde, Markus; Salmeron, Miquel; Altman, Eric I.; Schwarz, Udo D.

    2008-02-27

    The authors present the design and first results of a low-temperature, ultrahigh vacuum scanning probe microscope enabling atomic resolution imaging in both scanning tunneling microscopy (STM) and noncontact atomic force microscopy (NC-AFM) modes. A tuning-fork-based sensor provides flexibility in selecting probe tip materials, which can be either metallic or nonmetallic. When choosing a conducting tip and sample, simultaneous STM/NC-AFM data acquisition is possible. Noticeable characteristics that distinguish this setup from similar systems providing simultaneous STM/NC-AFM capabilities are its combination of relative compactness (on-top bath cryostat needs no pit), in situ exchange of tip and sample at low temperatures, short turnaround times, modest helium consumption, and unrestricted access from dedicated flanges. The latter permits not only the optical surveillance of the tip during approach but also the direct deposition of molecules or atoms on either tip or sample while they remain cold. Atomic corrugations as low as 1 pm could successfully be resolved. In addition, lateral drifts rates of below 15 pm/h allow long-term data acquisition series and the recording of site-specific spectroscopy maps. Results obtained on Cu(111) and graphite illustrate the microscope's performance.

  20. A 10 mK scanning tunneling microscope operating in ultra high vacuum and high magnetic fields.

    PubMed

    Assig, Maximilian; Etzkorn, Markus; Enders, Axel; Stiepany, Wolfgang; Ast, Christian R; Kern, Klaus

    2013-03-01

    We present design and performance of a scanning tunneling microscope (STM) that operates at temperatures down to 10 mK providing ultimate energy resolution on the atomic scale. The STM is attached to a dilution refrigerator with direct access to an ultra high vacuum chamber allowing in situ sample preparation. High magnetic fields of up to 14 T perpendicular and up to 0.5 T parallel to the sample surface can be applied. Temperature sensors mounted directly at the tip and sample position verified the base temperature within a small error margin. Using a superconducting Al tip and a metallic Cu(111) sample, we determined an effective temperature of 38 ± 1 mK from the thermal broadening observed in the tunneling spectra. This results in an upper limit for the energy resolution of ΔE = 3.5 kBT = 11.4 ± 0.3 μeV. The stability between tip and sample is 4 pm at a temperature of 15 mK as demonstrated by topography measurements on a Cu(111) surface.

  1. A 10Â mK scanning tunneling microscope operating in ultra high vacuum and high magnetic fields

    NASA Astrophysics Data System (ADS)

    Assig, Maximilian; Etzkorn, Markus; Enders, Axel; Stiepany, Wolfgang; Ast, Christian R.; Kern, Klaus

    2013-03-01

    We present design and performance of a scanning tunneling microscope (STM) that operates at temperatures down to 10 mK providing ultimate energy resolution on the atomic scale. The STM is attached to a dilution refrigerator with direct access to an ultra high vacuum chamber allowing in situ sample preparation. High magnetic fields of up to 14 T perpendicular and up to 0.5 T parallel to the sample surface can be applied. Temperature sensors mounted directly at the tip and sample position verified the base temperature within a small error margin. Using a superconducting Al tip and a metallic Cu(111) sample, we determined an effective temperature of 38 ± 1 mK from the thermal broadening observed in the tunneling spectra. This results in an upper limit for the energy resolution of ΔE = 3.5kBT = 11.4 ± 0.3 μeV. The stability between tip and sample is 4 pm at a temperature of 15 mK as demonstrated by topography measurements on a Cu(111) surface.

  2. Scanned probe microscope for biological applications

    NASA Astrophysics Data System (ADS)

    Baiburin, Vil B.; Konnov, Nikolai P.; Shcherbakov, Anatolyi A.; Malakhaeva, Alina N.; Zadnova, Svetlana P.; Volkov, Yuri P.

    1997-12-01

    In our biophysical laboratory has been developed a new scanned probe microscope (SPM) for biological application. The SPM allows to investigate a biological samples' surface by means of three different near field microscopes: scanning tunneling microscope (STM), atomic force microscope (AFM) and near field scanning optical microscope (NSOM). The SPM is very rigid and can be operated in ordinary laboratory without any vibration isolation. The scanning area of the microscope is about 10 by 10 micrometers. Some different biological objects were visualized by means of the SPM viz. bacteria (E. Coli, plague, cholera, staphylococcus), macromolecules (DNA, plague proteins) and phage (T2).

  3. Extending the Chemical and Optical Sensitivity of the Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Yu, Arthur

    This dissertation discusses the theoretical basis and experimental applications to improving the capability of the STM in chemical and optical sensitivity. Traditional STM methods have achieved unprecedented spatial resolution, but suffer from a lack of sensitivity to chemical structure and composition. A new method of imaging, based on inelastic electron tunneling spectroscopy (IETS) measurement of hydrogen molecules is developed. The interaction of plasmon excitations to electronic states of a metal nano-cluster is also studied, allowing for better understanding of the mechanisms involved in the plasmon -- electron coupling. Since its application at the single molecule level in the STM was realized, IETS has been used to identify different molecules through their vibrational signal. In recent experiments, rotational excitation of H2 was detected on metal and insulator surfaces. It was found that the energy of these excitations depend sensitively on the local chemical environment. By monitoring the rotational and vibrational IETS signal of the H2 across the molecule, a more chemically sensitive image can be constructed. When the method is applied to imaging magnesium porphyrin (MgP) on Au (110), different components of the molecule can be observed at different energies. These differences are indication of how the various components interact with the H2. Optical sensitivity of the STM manifests in the detection of photons emitted from the tunnel junction. Previous experiments have shown that we can map the excitation of molecular fluorescence with sub-Angstrom resolution. For applications in photochemistry and catalysis, understanding how plasmons interact with photons and electrons is crucial. Light emission from Au nanoclusters on oxide shows strong correlation with their electronic states. The interaction between plasmon mode in the junction and electronic states of the nano-clusters is further studied through clusters of different sizes and dimers. Emission of

  4. A novel technique for nano-scale lithography of cadmium selenide via a scanning tunneling microscope tip-induced reaction

    NASA Astrophysics Data System (ADS)

    Olson, Joel Andrew

    In the introductory chapter the physical and interfacial properties of cadmium selenide are presented, as well as a discussion of select surface properties of CdSe. Also, a brief review of scanning probe lithographic techniques currently under investigation is presented. As a portion of the project presented herein, a research-grade scanning tunneling microscope was constructed. The second chapter includes information specific to this instrument. Included are descriptions of the electrical components, descriptions of the mechanical components, and a description of the noise reduction and calibration of the instrument. When cleaved-in-air (112¯0) CdSe is imaged repeatedly under humidified conditions, small (˜20 nm wide and between 6 A and 12 A in height) features are observed to form. The features are similar in shape to one another, suggesting tip imaging. Under an atmosphere of dried nitrogen feature growth is not observed. The growth of the features shows a strong dependence on both the tunneling current and the bias voltage. The initial rate of feature growth increases with tunneling current. Feature growth as a function of bias voltage displays an onset at a sample bias of -1. 2 V to -1. 3 V and is no longer observed at sample biases more negative than -2.5 V. Two possible models are presented for feature growth. The smallest feature observed is ˜6 nm in width. The fourth chapter describes simple and inexpensive classroom demonstrations of nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI). The demonstrations comprise common orienteering compasses, whose needles represent magnetic dipoles, along with three collinear permanent magnets, and a magnetic stir plate or pulseable electromagnets. The trio of permanent magnets provides a laterally uniform magnetic field, whose strength decreases with distance from the magnets. Resonance can be observed by adjusting the frequency of the magnetic stirrer when it is in close proximity to the compasses

  5. Design and calibration of a scanning tunneling microscope for large machined surfaces

    SciTech Connect

    Grigg, D.A.; Russell, P.E.; Dow, T.A.

    1988-12-01

    During the last year the large sample STM has been designed, built and used for the observation of several different samples. Calibration of the scanner for prope dimensional interpretation of surface features has been a chief concern, as well as corrections for non-linear effects such as hysteresis during scans. Several procedures used in calibration and correction of piezoelectric scanners used in the laboratorys STMs are described.

  6. Design and performance of a cryogenic scanning tunneling microscope in high magnetic field for 2D layered materials study

    NASA Astrophysics Data System (ADS)

    Chuang, Tien-Ming; Chung, Pei-Fang; Guan, Syu-You; Yu, Shan-An; Liu, Che-An; Hsu, Chia-Sheng; Su, Chih-Chuan; Sankar, Raman; Chou, Fang-Cheng

    2015-03-01

    We will describe the design and performance of a cryogenic scanning tunneling microscope (STM) system in a high magnetic field. A Pan-type STM is mounted on a homemade low vibration 4He pot refrigerator, which can be operated in continuous flow mode at T ~ 1.6K and in a magnetic field of up to 9 Tesla. A cleavage device at T =4.2K stage is used to cleave the 2D layered materials before inserting into STM as well as functioning as the radiation shield. The liquid helium boil rate of 4.6 liters per day is achieved due to our careful design, which allows the measurement at base temperature up to 10 days. We will demonstrate its capability of measuring atomically registered energy resolved spectroscopic maps in both real space and momentum space by our recent results on Rashba BiTeI. This work is supported by Ministry of Science and Technology, Taiwan and Kenda Foundation, Taiwan.

  7. A new scanning tunneling microscope reactor used for high-pressure and high-temperature catalysis studies.

    PubMed

    Tao, Feng; Tang, David; Salmeron, Miquel; Somorjai, Gabor A

    2008-08-01

    We present the design and performance of a homebuilt high-pressure and high-temperature reactor equipped with a high-resolution scanning tunneling microscope (STM) for catalytic studies. In this design, the STM body, sample, and tip are placed in a small high pressure reactor ( approximately 19 cm(3)) located within an ultrahigh vacuum (UHV) chamber. A sealable port on the wall of the reactor separates the high pressure environment in the reactor from the vacuum environment of the STM chamber and permits sample transfer and tip change in UHV. A combination of a sample transfer arm, wobble stick, and sample load-lock system allows fast transfer of samples and tips between the preparation chamber, high pressure reactor, and ambient environment. This STM reactor can work as a batch or flowing reactor at a pressure range of 10(-13) to several bars and a temperature range of 300-700 K. Experiments performed on two samples both in vacuum and in high pressure conditions demonstrate the capability of in situ investigations of heterogeneous catalysis and surface chemistry at atomic resolution at a wide pressure range from UHV to a pressure higher than 1 atm.

  8. Real-space post-processing correction of thermal drift and piezoelectric actuator nonlinearities in scanning tunneling microscope images

    NASA Astrophysics Data System (ADS)

    Yothers, Mitchell P.; Browder, Aaron E.; Bumm, Lloyd A.

    2017-01-01

    We have developed a real-space method to correct distortion due to thermal drift and piezoelectric actuator nonlinearities on scanning tunneling microscope images using Matlab. The method uses the known structures typically present in high-resolution atomic and molecularly resolved images as an internal standard. Each image feature (atom or molecule) is first identified in the image. The locations of each feature's nearest neighbors are used to measure the local distortion at that location. The local distortion map across the image is simultaneously fit to our distortion model, which includes thermal drift in addition to piezoelectric actuator hysteresis and creep. The image coordinates of the features and image pixels are corrected using an inverse transform from the distortion model. We call this technique the thermal-drift, hysteresis, and creep transform. Performing the correction in real space allows defects, domain boundaries, and step edges to be excluded with a spatial mask. Additional real-space image analyses are now possible with these corrected images. Using graphite(0001) as a model system, we show lattice fitting to the corrected image, averaged unit cell images, and symmetry-averaged unit cell images. Statistical analysis of the distribution of the image features around their best-fit lattice sites measures the aggregate noise in the image, which can be expressed as feature confidence ellipsoids.

  9. Anisotropic Superconducting Gap Revealed by Angle Resolved Specific Heat, Point Contact Tunneling and Scanning Tunneling Microscope in Iron Pnictide Superconductors

    NASA Astrophysics Data System (ADS)

    Wen, Hai-Hu

    2011-03-01

    Angle resolved specific heat was measured in FeSe 0.55 Te 0.45 single crystals. A four-fold oscillation of C/T, with the minimum locating at the Fe-Fe bond direction, was observed when the sample was rotated at 9 T, which can be understood as due to the gap modulation on the electron pocket within the scheme of S +/- pairing. Accordingly, by measuring the point contact Andreev reflection spectrum on the BaFe 2-x Ni x As 2 single crystals in wide doping regimes, we found a crossover from nodeless to nodal feature of the superconducting gap. In K-doped BaFe 2 As 2 single crystals, we performed the low temperature STM measurements and observed a well ordered vortex lattice in local region. In addition, the statistics on over 3000 dI/dV spectra illustrate clear evidence of two gaps with magnitude of 7.6 meV and 3.3 meV, respectively. Detailed fitting to the tunneling spectrum shows an isotropic superconducting gap. Work collaborated with B. Zeng, C. Ren, L. Shan, Y. L. Wang, B. Shen, G. Mu, H. Q. Luo, T. Xiang, H. Yang, I. I. Mazin and P. C. Dai. This work was supported by the Natural Science Foundation of China, the Ministry of Science and Technology of China (2011CB605900, No. 2006CB921802), and Chinese Academy of Sciences. IIM was supported by the Office of the Naval Research.

  10. Compact device for cleaning scanner-mounted scanning tunneling microscope tips using electron bombardment

    NASA Astrophysics Data System (ADS)

    Hellmann, D.; Worbes, L.; Kittel, A.

    2011-08-01

    Most scanning probe techniques rely on the assumption that both sample and tip are free from adsorbates, residues, and oxide not deposited intentionally. Getting a clean sample surface can be readily accomplished by applying ion sputtering and subsequent annealing, whereas finding an adequate treatment for tips is much more complicated. The method of choice would effectively desorb undesired compounds without reducing the sharpness or the general geometry of the tip. Several devices which employ accelerated electrons to achieve this are described in the literature. To minimize both the effort to implement this technique in a UHV chamber and the overall duration of the cleaning procedure, we constructed a compact electron source fitted into a sample holder, which can be operated in a standard Omicron variable-temperature (VT)-STM while the tip stays in place. This way a maximum of compatibility with existing systems is achieved and short turnaround times are possible for tip cleaning.

  11. Joule heating and spin-transfer torque investigated on the atomic scale using a spin-polarized scanning tunneling microscope.

    PubMed

    Krause, S; Herzog, G; Schlenhoff, A; Sonntag, A; Wiesendanger, R

    2011-10-28

    The influence of a high spin-polarized tunnel current onto the switching behavior of a superparamagnetic nanoisland on a nonmagnetic substrate is investigated by means of spin-polarized scanning tunneling microscopy. A detailed lifetime analysis allows for a quantification of the effective temperature rise of the nanoisland and the modification of the activation energy barrier for magnetization reversal, thereby using the nanoisland as a local thermometer and spin-transfer torque analyzer. Both the Joule heating and spin-transfer torque are found to scale linearly with the tunnel current. The results are compared to experiments performed on lithographically fabricated magneto-tunnel junctions, revealing a very high spin-transfer torque switching efficiency in our experiments.

  12. Manipulation of subsurface carbon nanoparticles in Bi2Sr2CaCu2O8+δ using a scanning tunneling microscope

    DOE PAGES

    Stollenwerk, A. J.; Hurley, N.; Beck, B.; ...

    2015-03-19

    In this study, we present evidence that subsurface carbon nanoparticles in Bi₂Sr₂CaCu₂O8+δ can be manipulated with nanometer precision using a scanning tunneling microscope. High resolution images indicate that most of the carbon particles remain subsurface after transport observable as a local increase in height as the particle pushes up on the surface. Tunneling spectra in the vicinity of these protrusions exhibit semiconducting characteristics with a band gap of approximately 1.8 eV, indicating that the incorporation of carbon locally alters the electronic properties near the surface.

  13. Quantitative impedance characterization of sub-10 nm scale capacitors and tunnel junctions with an interferometric scanning microwave microscope.

    PubMed

    Wang, Fei; Clément, Nicolas; Ducatteau, Damien; Troadec, David; Tanbakuchi, Hassan; Legrand, Bernard; Dambrine, Gilles; Théron, Didier

    2014-10-10

    We present a method to characterize sub-10 nm capacitors and tunnel junctions by interferometric scanning microwave microscopy (iSMM) at 7.8 GHz. At such device scaling, the small water meniscus surrounding the iSMM tip should be reduced by proper tip tuning. Quantitative impedance characterization of attofarad range capacitors is achieved using an 'on-chip' calibration kit facing thousands of nanodevices. Nanoscale capacitors and tunnel barriers were detected through variations in the amplitude and phase of the reflected microwave signal, respectively. This study promises quantitative impedance characterization of a wide range of emerging functional nanoscale devices.

  14. The effects of two-dimensional bifurcations and quantum beats in a system of combined atomic force and scanning tunneling microscopes with quantum dots

    NASA Astrophysics Data System (ADS)

    Zhukovsky, V. Ch.; Krevchik, V. D.; Semenov, M. B.; Krevchik, P. V.; Zaytsev, R. V.; Egorov, I. A.

    2016-11-01

    The field and temperature dependence of the probability of two-dimensional dissipative tunneling is studied in the framework of one-instanton approximation for a model double-well oscillator potential in an external electric field at finite temperature with account for the influence of two local phonon modes for quantum dots in a system of a combined atomic force and a scanning tunneling microscope. It is demonstrated that in the mode of synchronous parallel transfer of tunneling particles from the cantilever tip to the quantum dot the two local phonon modes result in the occurrence of two stable peaks in the curve of the 2D dissipative tunneling probability as a function of the field. Qualitative comparison of the theoretical curve in the limit of weak dissociation and the experimental current-voltage characteristic for quantum dots that grow from colloidal gold under a cantilever tip at the initial stage of quantum-dot formation when the quantum dot size does not exceed 10 nm is performed. It is established that one of the two stable peaks that correspond to interaction of tunneling particles with two local phonon modes in the temperature dependence of the 2D dissipative tunneling probability can be split in two, which corresponds to the tunneling channel interference mechanism. It is found that the theoretically predicted and experimentally observed mode of quantum beats occurs near the bifurcation point.

  15. The design and building of an alternating current scanning tunneling microscope for nanometer scale imaging of insulating surfaces

    NASA Astrophysics Data System (ADS)

    Schafer, Adam Jay David

    An alternating current scanning tunneling microscope (ACSTM) has been designed and built for the study of insulating surfaces on the nanometer scale. The instrument consists of an STM built within a microwave resonant cavity. This design allows for simultaneous operation for both DC and ACSTM. The instrument is housed in a nitrogen atmosphere glovebox for the observation and handling of air-sensitive samples. In order to achieve the detailed resolution of STM on insulating surfaces the ACSTM uses the application of a high frequency alternating current bias voltage across a tip-sample junction, the resulting alternating current can be measured. Specifically, the non-linearilty of the STM junction allows the third harmonic (TH) of the driving frequency to be used as the measured quantity for imaging and control. By using the third harmonic of the fundamental driving voltage as the measured quantity to control the tip-sample distance, STM quality images have been produced without the reliance on a conductive surface. The atomic scale resolution of a silicon dioxide surface and the growth of such layers appeared to provide an ideal system for imaging with the ACSTM. Through the use of DC STM we have shown how the H-Si(111) surface morphology is effected by the length of etch time and the kinetic effect of stirring the etchant solution. Several experimental results make use of the ACSTM employing the TH signal for measurement under both DC feedback control and under AC feedback control. We will address the experimental procedure, signal generation and sample dependence upon ACSTM image resolution. By comparing three sulfides (CuS, MoS2. and PbS) and H-Si(111), the TH signal generation and ultimate ACSTM resolution is explored. A more in depth analysis covers the application of the ACSTM to investigate the probe induced surface oxidation of natural PbS. With the ACSTM, the complete transformation from a semiconductive to an insulating surface is imaged in real-time for

  16. Forensic Scanning Electron Microscope

    NASA Astrophysics Data System (ADS)

    Keeley, R. H.

    1983-03-01

    The scanning electron microscope equipped with an x-ray spectrometer is a versatile instrument which has many uses in the investigation of crime and preparation of scientific evidence for the courts. Major applications include microscopy and analysis of very small fragments of paint, glass and other materials which may link an individual with a scene of crime, identification of firearms residues and examination of questioned documents. Although simultaneous observation and chemical analysis of the sample is the most important feature of the instrument, other modes of operation such as cathodoluminescence spectrometry, backscattered electron imaging and direct x-ray excitation are also exploited. Marks on two bullets or cartridge cases can be compared directly by sequential scanning with a single beam or electronic linkage of two instruments. Particles of primer residue deposited on the skin and clothing when a gun is fired can be collected on adhesive tape and identified by their morphology and elemental composition. It is also possible to differentiate between the primer residues of different types of ammunition. Bullets may be identified from the small fragments left behind as they pass through the body tissues. In the examination of questioned documents the scanning electron microscope is used to establish the order in which two intersecting ink lines were written and to detect traces of chemical markers added to the security inks on official documents.

  17. Design and performance of an ultra-high vacuum scanning tunneling microscope operating at dilution refrigerator temperatures and high magnetic fields.

    PubMed

    Misra, S; Zhou, B B; Drozdov, I K; Seo, J; Urban, L; Gyenis, A; Kingsley, S C J; Jones, H; Yazdani, A

    2013-10-01

    We describe the construction and performance of a scanning tunneling microscope capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful thermal anchoring of the microscope, described in detail, is confirmed through a base temperature reading of 20 mK, along with a measured electron temperature of 250 mK. Atomically resolved images, along with complementary vibration measurements, are presented to confirm the effectiveness of the vibration isolation scheme in this instrument. Finally, we demonstrate that the microscope is capable of the same level of performance as typical machines with more modest refrigeration by measuring spectroscopic maps at base temperature both at zero field and in an applied magnetic field.

  18. Design and performance of an ultra-high vacuum scanning tunneling microscope operating at dilution refrigerator temperatures and high magnetic fields

    NASA Astrophysics Data System (ADS)

    Misra, S.; Zhou, B. B.; Drozdov, I. K.; Seo, J.; Urban, L.; Gyenis, A.; Kingsley, S. C. J.; Jones, H.; Yazdani, A.

    2013-10-01

    We describe the construction and performance of a scanning tunneling microscope capable of taking maps of the tunneling density of states with sub-atomic spatial resolution at dilution refrigerator temperatures and high (14 T) magnetic fields. The fully ultra-high vacuum system features visual access to a two-sample microscope stage at the end of a bottom-loading dilution refrigerator, which facilitates the transfer of in situ prepared tips and samples. The two-sample stage enables location of the best area of the sample under study and extends the experiment lifetime. The successful thermal anchoring of the microscope, described in detail, is confirmed through a base temperature reading of 20 mK, along with a measured electron temperature of 250 mK. Atomically resolved images, along with complementary vibration measurements, are presented to confirm the effectiveness of the vibration isolation scheme in this instrument. Finally, we demonstrate that the microscope is capable of the same level of performance as typical machines with more modest refrigeration by measuring spectroscopic maps at base temperature both at zero field and in an applied magnetic field.

  19. Probing the limits of Si:P δ-doped devices patterned by a scanning tunneling microscope in a field-emission mode

    SciTech Connect

    Rudolph, M.; Carr, S. M.; Ten Eyck, G.; Dominguez, J.; Carroll, M. S.; Bussmann, E.; Subramania, G.; Lilly, M. P.; Pluym, T.

    2014-10-20

    Recently, a single atom transistor was deterministically fabricated using phosphorus in Si by H-desorption lithography with a scanning tunneling microscope (STM). This milestone in precision, achieved by operating the STM in the conventional tunneling mode, typically utilizes slow (∼10{sup 2} nm{sup 2}/s) patterning speeds. By contrast, using the STM in a high-voltage (>10 V) field-emission mode, patterning speeds can be increased by orders of magnitude to ≳10{sup 4} nm{sup 2}/s. We show that the rapid patterning negligibly affects the functionality of relatively large micron-sized features, which act as contacting pads for these devices. For nanoscale structures, we show that the resulting electrical transport is consistent with the donor incorporation chemistry constraining the electrical dimensions to a scale of 10 nm even though the pattering spot size is 40 nm.

  20. Mirror buckling of freestanding graphene membranes induced by local heating due to a scanning tunneling microscope tip

    NASA Astrophysics Data System (ADS)

    Schoelz, J. K.; Neek Amal, M.; Xu, P.; Barber, S. D.; Ackerman, M. L.; Thibado, P. M.; Sadeghi, A.; Peeters, F. M.

    2014-03-01

    Scanning tunneling microscopy has been an invaluable tool in the study of graphene at the atomic scale. Several STM groups have managed to obtain atomic scale images of freestanding graphene membranes providing insight into the behavior of the stabilized ripple geometry. However, we found that the interaction between the STM tip and the freestanding graphene sample may induce additional effects. By varying the tunneling parameters, we can tune the position of the sample, in either a smooth or step like fashion. These phenomena were investigated by STM experiments, continuum elasticity theory and large scale molecular dynamics simulations. These results confirm that by increasing the tip bias, the electrostatic attraction between the tip and sample increases. When applied on a concave surface, this can result in mirror buckling which leads to a large scale movement of the sample. Interestingly, due in part to the negative coefficient of thermal expansion of graphene, buckling transitions can also be induced through local heating of the surface using the STM tip. Financial support by O.N.R. grant N00014-10-1-0181, N.S.F grant DMR-0855358, EU-Marie Curie IIF postdoc Fellowship/299855 (for M. N. A.), ESF-EuroGRAPHENE project CONGRAN, F.S.F (FWO-Vl), and Methusalem Foundation of the Flemish Government.

  1. Probing Dirac fermion dynamics in topological insulator Bi2Se3 films with a scanning tunneling microscope.

    PubMed

    Song, Can-Li; Wang, Lili; He, Ke; Ji, Shuai-Hua; Chen, Xi; Ma, Xu-Cun; Xue, Qi-Kun

    2015-05-01

    Scanning tunneling microscopy and spectroscopy have been used to investigate the femtosecond dynamics of Dirac fermions in the topological insulator Bi2Se3 ultrathin films. At the two-dimensional limit, bulk electrons become quantized and the quantization can be controlled by the film thickness at a single quintuple layer level. By studying the spatial decay of standing waves (quasiparticle interference patterns) off steps, we measure directly the energy and film thickness dependence of the phase relaxation length lϕ and inelastic scattering lifetime τ of topological surface-state electrons. We find that τ exhibits a remarkable (E - EF)(-2) energy dependence and increases with film thickness. We show that the features revealed are typical for electron-electron scattering between surface and bulk states.

  2. Scanning tunneling microscope investigations of organic heterostructures prepared by a combination of self-assembly and molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Staub, R.; Toerker, M.; Fritz, T.; Schmitz-Hübsch, T.; Sellam, F.; Leo, K.

    2000-01-01

    We report the realization of organic-organic heteroepitaxy by combining liquid-phase self-assembly with ultrahigh vacuum (UHV) gas-phase molecular beam epitaxy. As a model system, we have used self-assembled monolayers (SAMs) prepared by exposing an Au(111)-mica substrate to a dilute solution of decanethiol in ethanol, with subsequent evaporation of 3,4,9,10-perylene-tetracarboxylic-dianhydride (PTCDA) dye molecules. The well-known (3×3)R30° superstructure of almost upright standing molecules after chemisorption is replaced by the 11.5×3 (33.2 Å) pin-stripe phase with flat lying molecules when the samples are annealed in UHV and coverage decreases. The deposition of PTCDA induces reordering and displacement in the decanethiol SAM. Additional to the 33.2 Å periodicity, the previously reported 22 Å thiol stripe phase can be observed by scanning tunneling microscopy. Several PTCDA structures are observed: single and double rows of PTCDA that grow along decanethiol stripes on top of the flat-lying alkane chain groups, as well as densely packed PTCDA monolayer domains embedded into the thiol layer. These exhibit the well-known herringbone structure or a novel square lattice structure. We have also investigated thicker PTCDA islands and observed molecular resolution for a thickness of several monolayers. The structure of the three-dimensional islands can be identified as the α bulk modification.

  3. The near-field scanning thermal microscope

    NASA Astrophysics Data System (ADS)

    Wischnath, Uli F.; Welker, Joachim; Munzel, Marco; Kittel, Achim

    2008-07-01

    We report on the design, characterization, and performance of a near-field scanning thermal microscope capable to detect thermal heat currents mediated by evanescent thermal electromagnetic fields close to the surface of a sample. The instrument operates in ultrahigh vacuum and retains its scanning tunneling microscope functionality, so that its miniature, micropipette-based thermocouple sensor can be positioned with high accuracy. Heat currents on the order of 10-7W are registered in z spectroscopy at distances from the sample ranging from 1 to about 30nm. In addition, the device provides detailed thermographic images of a sample's surface.

  4. "We Actually Saw Atoms with Our Own Eyes": Conceptions and Convictions in Using the Scanning Tunneling Microscope in Junior High School

    ERIC Educational Resources Information Center

    Margel, Hannah; Eylon, Bat-Sheva; Scherz, Zahava

    2004-01-01

    The feasibility and the potential contribution of the scanning tunneling microscopy (STM) in junior high school (JHS) as an instructional tool for learning the particulate nature of matter is described. The use and power of new technologies can probably be demonstrated by the scanning tunneling microscopy (STM).

  5. A 350 mK, 9 T scanning tunneling microscope for the study of superconducting thin films on insulating substrates and single crystals

    SciTech Connect

    Kamlapure, Anand; Saraswat, Garima; Ganguli, Somesh Chandra; Bagwe, Vivas; Raychaudhuri, Pratap; Pai, Subash P.

    2013-12-15

    We report the construction and performance of a low temperature, high field scanning tunneling microscope (STM) operating down to 350 mK and in magnetic fields up to 9 T, with thin film deposition and in situ single crystal cleaving capabilities. The main focus lies on the simple design of STM head and a sample holder design that allows us to get spectroscopic data on superconducting thin films grown in situ on insulating substrates. Other design details on sample transport, sample preparation chamber, and vibration isolation schemes are also described. We demonstrate the capability of our instrument through the atomic resolution imaging and spectroscopy on NbSe{sub 2} single crystal and spectroscopic maps obtained on homogeneously disordered NbN thin film.

  6. A scanning cavity microscope

    PubMed Central

    Mader, Matthias; Reichel, Jakob; Hänsch, Theodor W.; Hunger, David

    2015-01-01

    Imaging the optical properties of individual nanosystems beyond fluorescence can provide a wealth of information. However, the minute signals for absorption and dispersion are challenging to observe, and only specialized techniques requiring sophisticated noise rejection are available. Here we use signal enhancement in a high-finesse scanning optical microcavity to demonstrate ultra-sensitive imaging. Harnessing multiple interactions of probe light with a sample within an optical resonator, we achieve a 1,700-fold signal enhancement compared with diffraction-limited microscopy. We demonstrate quantitative imaging of the extinction cross-section of gold nanoparticles with a sensitivity less than 1 nm2; we show a method to improve the spatial resolution potentially below the diffraction limit by using higher order cavity modes, and we present measurements of the birefringence and extinction contrast of gold nanorods. The demonstrated simultaneous enhancement of absorptive and dispersive signals promises intriguing potential for optical studies of nanomaterials, molecules and biological nanosystems. PMID:26105690

  7. High Pressure Scanning Tunneling Microscopy Studies of AdsorbateStructure and Mobility during Catalytic Reactions: Novel Design of anUltra High Pressure, High Temperature Scanning Tunneling MicroscopeSystem for Probing Catalytic Conversions

    SciTech Connect

    Tang, David Chi-Wai

    2005-05-16

    The aim of the work presented therein is to take advantage of scanning tunneling microscope’s (STM) capability for operation under a variety of environments under real time and at atomic resolution to monitor adsorbate structures and mobility under high pressures, as well as to design a new generation of STM systems that allow imaging in situ at both higher pressures (35 atm) and temperatures (350 °C).

  8. Line-scanning, stage scanning confocal microscope

    NASA Astrophysics Data System (ADS)

    Carucci, John A.; Stevenson, Mary; Gareau, Daniel

    2016-03-01

    We created a line-scanning, stage scanning confocal microscope as part of a new procedure: video assisted micrographic surgery (VAMS). The need for rapid pathological assessment of the tissue on the surface of skin excisions very large since there are 3.5 million new skin cancers diagnosed annually in the United States. The new design presented here is a confocal microscope without any scanning optics. Instead, a line is focused in space and the sample, which is flattened, is physically translated such that the line scans across its face in a direction perpendicular to the line its self. The line is 6mm long and the stage is capable of scanning 50 mm, hence the field of view is quite large. The theoretical diffraction-limited resolution is 0.7um lateral and 3.7um axial. However, in this preliminary report, we present initial results that are a factor of 5-7 poorer in resolution. The results are encouraging because they demonstrate that the linear array detector measures sufficient signal from fluorescently labeled tissue and also demonstrate the large field of view achievable with VAMS.

  9. Scanning tunneling spectroscopic evidence for a magnetic field-revealed microscopic order in the high-TC superconductor YBa2Cu3O7-δ

    NASA Astrophysics Data System (ADS)

    Beyer, A. D.; Grinolds, M. S.; Teague, M. L.; Yeh, N.-C.; Tajima, S.

    2009-03-01

    We present spatially resolved scanning tunneling spectroscopic measurements of YBa2Cu3O7-δ as a function of magnetic field and at T<microscopic order. Ref.: Beyer, et.al. [arxiv:0808.3016].

  10. Atomically resolved studies of reactions at industrial settings - novel design of an ultra high pressure, high temperature scanning tunneling microscope system for probing catalytic conversions

    NASA Astrophysics Data System (ADS)

    Tang, David; Somorjai, Gabor

    2005-03-01

    In order to observe heterogeneous catalytic reactions that occur well above ambient pressure and temperature, a modified version of the Pan-style STM motor has been designed and constructed in-house. The new design features a much reduced size and a rigid coupling to the sample, and has been tested to show much higher resonant frequency than conventional Beetle-style STM designs, providing the ability to image faster and yielding lower susceptibility to noise. A small flow reactor cell (˜10 mL) has been constructed to house the new STM, whose samples and tips are accessible through a bayonet-sealed access port by the use of a wobble stick and a transfer arm. The reactor cell can be placed inside an UHV system to allow cleaning and characterization of sample before and after experiments, as well as continuous monitoring by mass spectrometry or gas chromatography through a leak valve. The new system also allows in vacuo sample and tip exchange without exposing the system to impurities in air. As such, the new ultrahigh pressure scanning tunneling microscope is designed to allow successive STM experiments performed with precise control of temperatures between 300 K and 600 K and pressures between <10-9 torr and 30 bars.

  11. Scanning Miniature Microscopes without Lenses

    NASA Technical Reports Server (NTRS)

    Wang, Yu

    2009-01-01

    The figure schematically depicts some alternative designs of proposed compact, lightweight optoelectronic microscopes that would contain no lenses and would generate magnified video images of specimens. Microscopes of this type were described previously in Miniature Microscope Without Lenses (NPO - 20218), NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 43 and Reflective Variants of Miniature Microscope Without Lenses (NPO 20610), NASA Tech Briefs, Vol. 26, No. 9 (September 1999), page 6a. To recapitulate: In the design and construction of a microscope of this type, the focusing optics of a conventional microscope are replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. Elimination of focusing optics reduces the size and weight of the instrument and eliminates the need for the time-consuming focusing operation. The microscopes described in the cited prior articles contained two-dimensional CCDs registered with two-dimensional arrays of microchannels and, as such, were designed to produce full two-dimensional images, without need for scanning. The microscopes of the present proposal would contain one-dimensional (line image) CCDs registered with linear arrays of microchannels. In the operation of such a microscope, one would scan a specimen along a line perpendicular to the array axis (in other words, one would scan in pushbroom fashion). One could then synthesize a full two-dimensional image of the specimen from the line-image data acquired at one-pixel increments of position along the scan. In one of the proposed microscopes, a beam of unpolarized light for illuminating the specimen would enter from the side. This light would be reflected down onto the specimen by a nonpolarizing beam splitter attached to the microchannels at their lower ends. A portion of the light incident on the specimen would be reflected upward, through the beam splitter and along the microchannels, to form an image on the CCD. If the

  12. Energy-gap spectroscopy of superconductors using a tunneling microscope

    NASA Technical Reports Server (NTRS)

    Le Duc, H. G.; Kaiser, W. J.; Stern, J. A.

    1987-01-01

    A unique scanning tunneling microscope (STM) system has been developed for spectroscopy of the superconducting energy gap. High-resolution control of tunnel current and voltage allows for measurement of superconducting properties at tunnel resistance levels 100-1000 greater than that achieved in prior work. The previously used STM methods for superconductor spectroscopy are compared to those developed for the work reported here. Superconducting energy-gap spectra are reported for three superconductors, Pb, PbBi, and NbN, over a range of tunnel resistance. The measured spectra are compared directly to theory.

  13. Radio-frequency scanning tunnelling microscopy.

    PubMed

    Kemiktarak, U; Ndukum, T; Schwab, K C; Ekinci, K L

    2007-11-01

    The scanning tunnelling microscope (STM) relies on localized electron tunnelling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. In the 25-year period since its invention, the STM has helped uncover a wealth of phenomena in diverse physical systems--ranging from semiconductors to superconductors to atomic and molecular nanosystems. A severe limitation in scanning tunnelling microscopy is the low temporal resolution, originating from the diminished high-frequency response of the tunnel current readout circuitry. Here we overcome this limitation by measuring the reflection from a resonant inductor-capacitor circuit in which the tunnel junction is embedded, and demonstrate electronic bandwidths as high as 10 MHz. This approximately 100-fold bandwidth improvement on the state of the art translates into fast surface topography as well as delicate measurements in mesoscopic electronics and mechanics. Broadband noise measurements across the tunnel junction using this radio-frequency STM have allowed us to perform thermometry at the nanometre scale. Furthermore, we have detected high-frequency mechanical motion with a sensitivity approaching approximately 15 fm Hz(-1/2). This sensitivity is on par with the highest available from nanoscale optical and electrical displacement detection techniques, and the radio-frequency STM is expected to be capable of quantum-limited position measurements.

  14. PREFACE: Time-resolved scanning tunnelling microscopy Time-resolved scanning tunnelling microscopy

    NASA Astrophysics Data System (ADS)

    Zandvliet, Harold J. W.; Lin, Nian

    2010-07-01

    Scanning tunnelling microscopy has revolutionized our ability to image, manipulate, and investigate solid surfaces on the length scale of individual atoms and molecules. The strength of this technique lies in its imaging capabilities, since for many scientists 'seeing is believing'. However, scanning tunnelling microscopy also suffers from a severe limitation, namely its poor time resolution. Recording a scanning tunnelling microscopy image typically requires a few tens of seconds for a conventional scanning tunnelling microscope to a fraction of a second for a specially designed fast scanning tunnelling microscope. Designing and building such a fast scanning tunnelling microscope is a formidable task in itself and therefore, only a limited number of these microscopes have been built [1]. There is, however, another alternative route to significantly enhance the time resolution of a scanning tunnelling microscope. In this alternative method, the tunnelling current is measured as a function of time with the feedback loop switched off. The time resolution is determined by the bandwidth of the IV converter rather than the cut-off frequency of the feedback electronics. Such an approach requires a stable microscope and goes, of course, at the expense of spatial information. In this issue, we have collected a set of papers that gives an impression of the current status of this rapidly emerging field [2]. One of the very first attempts to extract information from tunnel current fluctuations was reported by Tringides' group in the mid-1990s [3]. They showed that the collective diffusion coefficient can be extracted from the autocorrelation of the time-dependent tunnelling current fluctuations produced by atom motion in and out of the tunnelling junction. In general, current-time traces provide direct information on switching/conformation rates and distributions of residence times. In the case where these processes are thermally induced it is rather straightforward to map

  15. Observation of a vacuum tunnel gap in a transmission electron microscope using a micromechanical tunneling microscope

    NASA Astrophysics Data System (ADS)

    Lutwyche, M. I.; Wada, Y.

    1995-05-01

    This letter reports the observation of the vacuum tunnel gap between two conductors using a high resolution transmission electron microscope. A 2.5 mm square micromachined tunneling microscope chip has been fabricated with a minimum feature size of 0.4 μm. The chip fits into a modified side-entry type transmission electron microscope holder. The tunnel gap is controlled by a purpose-built feedback controller. The micromachines work reliably during observation of the tip apex in a transmission electron microscope, allowing the voltage and current to be changed while the tunnel gap is observed.

  16. Scanning Tunneling Optical Resonance Microscopy

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically < 10 Hz) that the

  17. Versatile scanned probe microscope: technical and biological applications

    NASA Astrophysics Data System (ADS)

    Baiburin, Vil B.; Konnov, Nikolai P.; Volkov, Uryi P.

    1999-03-01

    In our biophysical laboratory a new scanned probe microscope (SPM) for technical and biological application has been developed. The SPM allows to investigate sample surface by means of three different near field microscopes: scanning tunneling microscope, atomic force microscope and near field scanning optical microscope. The SPM is very rigid and can be operated in ordinary laboratory without any vibration isolation. The scanning area of the microscope is about 10 X 10 micrometers . Different technical and biological applications of the SPM are demonstrated. Results of the SPM investigations of different carbon, metal and dielectric films are described. The SPM comparison study of electrical breakdown and the conduction bistable switching effect in thin dielectric films of oxides and fluorides of some rare earth metals has been discussed. Some biological applications of the SPM viz. visualization of different bacteria (E.Coli, plague, cholera, staphylococcus), bacteria thin sections, macromolecules (plague proteins) and plague phage has been described.

  18. Multi-Functional Scanning Probe Microscope for Imaging of Soft Surfaces and Interfaces

    DTIC Science & Technology

    2014-10-31

    SECURITY CLASSIFICATION OF: This proposal requests the purchase of a RHK Technology ATM 300 Ambient Environment Scanning Tunneling Microscope (STM...ES) U.S. Army Research Office P.O. Box 12211 Research Triangle Park, NC 27709-2211 Scanning Tunneling Microscopy, soft materials, bio/abio...proposal requests the purchase of a RHK Technology ATM 300 Ambient Environment Scanning Tunneling Microscope (STM) for atomic- and molecular-resolution

  19. Nanoscale Proximity Effect in the High-Temperature Superconductor Bi2Sr2CaCu2O8+δ Using a Scanning Tunneling Microscope

    SciTech Connect

    Parker, C.V.; Gu, G.; Pushp, A.; Pasupathy, A.N.; Gomes, K.K.; Wen, J.; Xu, Z.; Ono, S.; Yazdani, A.

    2010-03-15

    High-temperature cuprate superconductors exhibit extremely local nanoscale phenomena and strong sensitivity to doping. While other experiments have looked at nanoscale interfaces between layers of different dopings, we focus on the interplay between naturally inhomogeneous nanoscale regions. Using scanning tunneling microscopy to carefully track the same region of the sample as a function of temperature, we show that regions with weak superconductivity can persist to elevated temperatures if bordered by regions of strong superconductivity. This suggests that it may be possible to increase the maximum possible transition temperature by controlling the distribution of dopants.

  20. The Scanning TMR Microscope for Biosensor Applications

    PubMed Central

    Vyas, Kunal N.; Love, David M.; Ionescu, Adrian; Llandro, Justin; Kollu, Pratap; Mitrelias, Thanos; Holmes, Stuart; Barnes, Crispin H. W.

    2015-01-01

    We present a novel tunnel magnetoresistance (TMR) scanning microscope set-up capable of quantitatively imaging the magnetic stray field patterns of micron-sized elements in 3D. By incorporating an Anderson loop measurement circuit for impedance matching, we are able to detect magnetoresistance changes of as little as 0.006%/Oe. By 3D rastering a mounted TMR sensor over our magnetic barcodes, we are able to characterise the complex domain structures by displaying the real component, the amplitude and the phase of the sensor’s impedance. The modular design, incorporating a TMR sensor with an optical microscope, renders this set-up a versatile platform for studying and imaging immobilised magnetic carriers and barcodes currently employed in biosensor platforms, magnetotactic bacteria and other complex magnetic domain structures of micron-sized entities. The quantitative nature of the instrument and its ability to produce vector maps of magnetic stray fields has the potential to provide significant advantages over other commonly used scanning magnetometry techniques. PMID:25849347

  1. Scanning Tunneling Optical Resonance Microscopy Developed

    NASA Technical Reports Server (NTRS)

    Bailey, Sheila G.; Raffaelle, Ryne P.; Lau, Janis E.; Jenkins, Phillip P.; Castro, Stephanie L.; Tin, Padetha; Wilt, David M.; Pal, Anna Maria; Fahey, Stephen D.

    2004-01-01

    The ability to determine the in situ optoelectronic properties of semiconductor materials has become especially important as the size of device architectures has decreased and the development of complex microsystems has increased. Scanning Tunneling Optical Resonance Microscopy, or STORM, can interrogate the optical bandgap as a function of its position within a semiconductor micro-structure. This technique uses a tunable solidstate titanium-sapphire laser whose output is "chopped" using a spatial light modulator and is coupled by a fiber-optic connector to a scanning tunneling microscope in order to illuminate the tip-sample junction. The photoenhanced portion of the tunneling current is spectroscopically measured using a lock-in technique. The capabilities of this technique were verified using semiconductor microstructure calibration standards that were grown by organometallic vapor-phase epitaxy. Bandgaps characterized by STORM measurements were found to be in good agreement with the bulk values determined by transmission spectroscopy and photoluminescence and with the theoretical values that were based on x-ray diffraction results.

  2. Sensing the quantum limit in scanning tunnelling spectroscopy

    PubMed Central

    Ast, Christian R.; Jäck, Berthold; Senkpiel, Jacob; Eltschka, Matthias; Etzkorn, Markus; Ankerhold, Joachim; Kern, Klaus

    2016-01-01

    The tunnelling current in scanning tunnelling spectroscopy (STS) is typically and often implicitly modelled by a continuous and homogeneous charge flow. If the charging energy of a single-charge quantum sufficiently exceeds the thermal energy, however, the granularity of the current becomes non-negligible. In this quantum limit, the capacitance of the tunnel junction mediates an interaction of the tunnelling electrons with the surrounding electromagnetic environment and becomes a source of noise itself, which cannot be neglected in STS. Using a scanning tunnelling microscope operating at 15 mK, we show that we operate in this quantum limit, which determines the ultimate energy resolution in STS. The P(E)-theory describes the probability for a tunnelling electron to exchange energy with the environment and can be regarded as the energy resolution function. We experimentally demonstrate this effect with a superconducting aluminium tip and a superconducting aluminium sample, where it is most pronounced. PMID:27708282

  3. Scanning tunneling microscopic and spectroscopic studies on a crystalline silica monolayer epitaxially formed on hexagonal SiC(0001{sup ¯}) surfaces

    SciTech Connect

    Tochihara, Hiroshi E-mail: tochihara.hiroshi.146@m.kyushu-u.ac.jp; Suzuki, Takayuki; Yagyu, Kazuma; Shirasawa, Tetsuroh; Takahashi, Toshio; Miyamachi, Toshio; Yoshizawa, Shunsuke; Komori, Fumio; Kajiwara, Takashi; Tanaka, Satoru

    2014-02-03

    An epitaxial silicon-oxide monolayer of chemical composition of Si{sub 2}O{sub 3} (the Si{sub 2}O{sub 3} layer) formed on hexagonal SiC(0001{sup ¯}) surfaces has been observed by scanning tunneling microscopy (STM). Filled- and empty-state STM images with atomic resolution support the previously reported model. Typical structural defects in the Si{sub 2}O{sub 3} layer are found to be missing SiO{sub n} (n = 1, 2, 3) molecules. The band gap of the Si{sub 2}O{sub 3} layer obtained by point tunneling spectroscopy is 5.5±0.5 eV, exhibiting considerable narrowing from that of bulk SiO{sub 2}, 8.9 eV. It is proposed that the Si{sub 2}O{sub 3} layer is suitable as a relevant interface material for formation of SiC-based metal-oxide-semiconductor devices.

  4. Scanning Tunneling Microscopy Studies of Quasicrystals

    NASA Astrophysics Data System (ADS)

    Becker, Russell S.; Kortan, A. Refik

    The following sections are included: * INTRODUCTION * EXPERIMENTAL * X-RAY DIFFRACTION * SCANNING TUNNELING MICROSCOPY * STRUCTURE MODELLING BASED ON STM * COMPARISON WITH MODELS BASED ON BULK STUDIES * CONCLUSION * REFERENCES

  5. Pre-microscope tunnelling — Inspiration or constraint?

    NASA Astrophysics Data System (ADS)

    Walmsley, D. G.

    1987-03-01

    Before the microscope burst upon the scene, tunnelling had established for itself a substantial niche in the repertoire of the solid state physicist. Over a period of 20 years it has contributed importantly to our understanding of many systems. It elucidated the superconducting state, first by a direct display of the energy gap then by providing detailed information on the phonon spectra and electron-phonon coupling strength in junction electrodes. Its use as a phonon spectrometer was subsequently extended to semiconductors and to the oxides of insulating barriers. Eventually the vibrational spectra of monolayer organic and inorganic adsorbates became amenable with rich scientific rewards. In a few cases electronic transitions have been observed. Plasmon excitation by tunnelling electrons led to insights on the electron loss function in metals at visible frequencies and provided along the way an intriguing light emitting device. With the advent of the microscope it is now appropriate to enquire how much of this experience can profitably be carried over to the new environment. Are we constrained just to repeat the experiments in a new configuration? Happily no. The microscope offers us topographical and spectroscopic information of a new order. One might next ask how great is the contact between the two disciplines? We explore this question and seek to establish where the pre-microscope experience can be helpful in inspiring our use of this marvellous new facility that we know as the scanning tunnelling microscope.

  6. Scanning thermal-conductivity microscope

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; McCarthy, Brendan; Grover, Ranjan

    2006-02-01

    This article describes a novel implementation of an atomic force microscope that can map thermal-conductivity features across a sample with a high spatial resolution. The microscope employs a single-sided, metal-coated cantilever, which acts as a bimetallic strip together with a heating laser whose beam is focused on the cantilever's free end, on the opposite side of its tip. Subtracting the topography obtained by the unheated and heated cantilevers yields a map of thermal conductivity across the surface of a sample. The article presents (a) the theory of operation of the microscope and (b) the experimental results obtained on a silicon sample with oxide features, showing good agreement between the two.

  7. Fast scanning mode and its realization in a scanning acoustic microscope

    SciTech Connect

    Ju Bingfeng; Bai Xiaolong; Chen Jian

    2012-03-15

    The scanning speed of the two-dimensional stage dominates the efficiency of mechanical scanning measurement systems. This paper focused on a detailed scanning time analysis of conventional raster and spiral scan modes and then proposed two fast alternative scanning modes. Performed on a self-developed scanning acoustic microscope (SAM), the measured images obtained by using the conventional scan mode and fast scan modes are compared. The total scanning time is reduced by 29% of the two proposed fast scan modes. It will offer a better solution for high speed scanning without sacrificing the system stability, and will not introduce additional difficulties to the configuration of scanning measurement systems. They can be easily applied to the mechanical scanning measuring systems with different driving actuators such as piezoelectric, linear motor, dc motor, and so on. The proposed fast raster and square spiral scan modes are realized in SAM, but not specially designed for it. Therefore, they have universal adaptability and can be applied to other scanning measurement systems with two-dimensional mechanical scanning stages, such as atomic force microscope or scanning tunneling microscope.

  8. Fast scanning mode and its realization in a scanning acoustic microscope.

    PubMed

    Ju, Bing-Feng; Bai, Xiaolong; Chen, Jian

    2012-03-01

    The scanning speed of the two-dimensional stage dominates the efficiency of mechanical scanning measurement systems. This paper focused on a detailed scanning time analysis of conventional raster and spiral scan modes and then proposed two fast alternative scanning modes. Performed on a self-developed scanning acoustic microscope (SAM), the measured images obtained by using the conventional scan mode and fast scan modes are compared. The total scanning time is reduced by 29% of the two proposed fast scan modes. It will offer a better solution for high speed scanning without sacrificing the system stability, and will not introduce additional difficulties to the configuration of scanning measurement systems. They can be easily applied to the mechanical scanning measuring systems with different driving actuators such as piezoelectric, linear motor, dc motor, and so on. The proposed fast raster and square spiral scan modes are realized in SAM, but not specially designed for it. Therefore, they have universal adaptability and can be applied to other scanning measurement systems with two-dimensional mechanical scanning stages, such as atomic force microscope or scanning tunneling microscope.

  9. Scanning evanescent electro-magnetic microscope

    DOEpatents

    Xiang, Xiao-Dong; Gao, Chen

    2001-01-01

    A novel scanning microscope is described that uses near-field evanescent electromagnetic waves to probe sample properties. The novel microscope is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The inventive scanning evanescent wave electromagnetic microscope (SEMM) can map dielectric constant, tangent loss, conductivity, complex electrical impedance, and other electrical parameters of materials. The quantitative map corresponds to the imaged detail. The novel microscope can be used to measure electrical properties of both dielectric and electrically conducting materials.

  10. Scanning evanescent electro-magnetic microscope

    DOEpatents

    Xiang, Xiao-Dong; Gao, Chen; Schultz, Peter G.; Wei, Tao

    2003-01-01

    A novel scanning microscope is described that uses near-field evanescent electromagnetic waves to probe sample properties. The novel microscope is capable of high resolution imaging and quantitative measurements of the electrical properties of the sample. The inventive scanning evanescent wave electromagnetic microscope (SEMM) can map dielectric constant, tangent loss, conductivity, complex electrical impedance, and other electrical parameters of materials. The quantitative map corresponds to the imaged detail. The novel microscope can be used to measure electrical properties of both dielectric and electrically conducting materials.

  11. Scanning Tunneling Microscopy of Multilayer Thin Film Solar Cell Materials^*

    NASA Astrophysics Data System (ADS)

    Mantovani, J. G.; Friedfeld, R.; Raffaelle, R. P.

    1996-03-01

    We have been investigating electrochemically deposited multilayer structures based on the Cu_xIn_2-xSe2 system for use in thin film solar cells. The interest in multilayer structures is due to their proposed use in increasing thin film solar cell efficiency. We have imaged the artificially imposed superstructure of our nanoscale multilayers using a scanning tunneling microscope. A comparison is made between the theoretically calculated modulation wavelengths and those generated by Fourier analysis of the scanning tunneling microscope images. A discussion of the use of photo-assisted tunneling spectroscopy in a modified STM is presented. * This work was supported by the Southeastern University Research Association in collaboration with Oak Ridge National Laboratory and the Florida Solar Energy Center.

  12. The Scanning Optical Microscope: An Overview

    NASA Astrophysics Data System (ADS)

    Kino, G. S.; Corte, T. R.; Xiao, G. Q.

    1988-07-01

    In the last few years there has been a resurgence in research on optical microscopes. One reason stems from the invention of the acoustic microscope by Quate and Lemons,1 and the realization that some of the same principles could be applied to the optical microscope. The acoustic microscope has better transverse definition for the same wavelength than the standard optical microscope and at the same time has far better range definition. Consequently, Kompfner, who was involved with the work on the early acoustic microscope, decided to try out similar scanning microscope principles with optics, and started a group with Wilson and Sheppard to carry out such research at Oxford.2 Sometime earlier, Petran et a13 had invented the tandem scanning microscope which used many of the same principles. Now, in our laboratory at Stanford, these ideas on the tandem scanning microscope and the scanning optical microscope are converging. Another aspect of this work, which stems from the earlier experience with the acoustic microscope, involves measurement of both phase and amplitude of the optical beam. It is also possible to use scanned optical microscopy for other purposes. For instance, an optical beam can be used to excite electrons and holes in semiconductors, and the generated current can be measured. By scanning the optical beam over the semiconductor, an image can be obtained of the regions where there is strong or weak electron hole generation. This type of microscope is called OBIC (Optical Beam Induced Current). A second application involves fluorescent imaging of biological materials. Here we have the excellent range definition of a scanning optical microscope which eliminates unwanted glare from regions of the material where the beam is unfocused.3 A third application is focused on the heating effect of the light beam. With such a system, images can be obtained which are associated with changes in the thermal properties of a material, changes in recombination rates in

  13. First results for custom-built low-temperature (4.2 K) scanning tunneling microscope/molecular beam epitaxy and pulsed laser epitaxy system designed for spin-polarized measurements

    NASA Astrophysics Data System (ADS)

    Foley, Andrew; Alam, Khan; Lin, Wenzhi; Wang, Kangkang; Chinchore, Abhijit; Corbett, Joseph; Savage, Alan; Chen, Tianjiao; Shi, Meng; Pak, Jeongihm; Smith, Arthur

    2014-03-01

    A custom low-temperature (4.2 K) scanning tunneling microscope system has been developed which is combined directly with a custom molecular beam epitaxy facility (and also including pulsed laser epitaxy) for the purpose of studying surface nanomagnetism of complex spintronic materials down to the atomic scale. For purposes of carrying out spin-polarized STM measurements, the microscope is built into a split-coil, 4.5 Tesla superconducting magnet system where the magnetic field can be applied normal to the sample surface; since, as a result, the microscope does not include eddy current damping, vibration isolation is achieved using a unique combination of two stages of pneumatic isolators along with an acoustical noise shield, in addition to the use of a highly stable as well as modular `Pan'-style STM design with a high Q factor. First 4.2 K results reveal, with clear atomic resolution, various reconstructions on wurtzite GaN c-plane surfaces grown by MBE, including the c(6x12) on N-polar GaN(0001). Details of the system design and functionality will be presented.

  14. Scanning Microscopes Using X Rays and Microchannels

    NASA Technical Reports Server (NTRS)

    Wang, Yu

    2003-01-01

    Scanning microscopes that would be based on microchannel filters and advanced electronic image sensors and that utilize x-ray illumination have been proposed. Because the finest resolution attainable in a microscope is determined by the wavelength of the illumination, the xray illumination in the proposed microscopes would make it possible, in principle, to achieve resolutions of the order of nanometers about a thousand times as fine as the resolution of a visible-light microscope. Heretofore, it has been necessary to use scanning electron microscopes to obtain such fine resolution. In comparison with scanning electron microscopes, the proposed microscopes would likely be smaller, less massive, and less expensive. Moreover, unlike in scanning electron microscopes, it would not be necessary to place specimens under vacuum. The proposed microscopes are closely related to the ones described in several prior NASA Tech Briefs articles; namely, Miniature Microscope Without Lenses (NPO-20218), NASA Tech Briefs, Vol. 22, No. 8 (August 1998), page 43; and Reflective Variants of Miniature Microscope Without Lenses (NPO-20610), NASA Tech Briefs, Vol. 26, No. 9 (September 2002) page 6a. In all of these microscopes, the basic principle of design and operation is the same: The focusing optics of a conventional visible-light microscope are replaced by a combination of a microchannel filter and a charge-coupled-device (CCD) image detector. A microchannel plate containing parallel, microscopic-cross-section holes much longer than they are wide is placed between a specimen and an image sensor, which is typically the CCD. The microchannel plate must be made of a material that absorbs the illuminating radiation reflected or scattered from the specimen. The microchannels must be positioned and dimensioned so that each one is registered with a pixel on the image sensor. Because most of the radiation incident on the microchannel walls becomes absorbed, the radiation that reaches the

  15. Energy gaps measured by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Chen; Giambattista, B.; Slough, C. G.; Coleman, R. V.; Subramanian, M. A.

    1990-11-01

    A scanning tunneling microscope (STM) has been used to measure energy gaps in the charge-density-wave (CDW) phases of the layer-structure dichalcogenides and in the high-temperature superconductor Bi2Sr2CaCu2O8. Measured values of ΔCDW at 4.2 K for 2H-TaSe2, 2H-TaS2, and 2H-NbSe2 are 80, 50, and 34 meV giving values of 2ΔCDW/kBTc equal to 15.2, 15.4, and 23.9, indicating strong coupling in these CDW systems. Measured values of ΔCDW at 4.2 K in 1T-TaSe2 and 1T-TaS2 are ~150 meV for both materials giving 2ΔCDW/kBTc~=5.8. STM scans of Bi2Sr2CaCu2O8 at 4.2 K resolve atoms on the BiOx layer and show possible variations in electronic structure. The energy gap determined from I versus V and dI/dV versus V curves is in the range 30-35 meV giving values of 2Δ/kBTc~=8. Spectroscopy measurements with the STM can exhibit large zero-bias anomalies which complicate the analysis of the energy-gap structure, but adequate separation has been accomplished.

  16. Three-dimensional scanning confocal laser microscope

    DOEpatents

    Anderson, R. Rox; Webb, Robert H.; Rajadhyaksha, Milind

    1999-01-01

    A confocal microscope for generating an image of a sample includes a first scanning element for scanning a light beam along a first axis, and a second scanning element for scanning the light beam at a predetermined amplitude along a second axis perpendicular to the first axis. A third scanning element scans the light beam at a predetermined amplitude along a third axis perpendicular to an imaging plane defined by the first and second axes. The second and third scanning element are synchronized to scan at the same frequency. The second and third predetermined amplitudes are percentages of their maximum amplitudes. A selector determines the second and third predetermined amplitudes such that the sum of the percentages is equal to one-hundred percent.

  17. Scanning scene tunnel for city traversing.

    PubMed

    Zheng, Jiang Yu; Zhou, Yu; Milli, Panayiotis

    2006-01-01

    This paper proposes a visual representation named scene tunnel for capturing urban scenes along routes and visualizing them on the Internet. We scan scenes with multiple cameras or a fish-eye camera on a moving vehicle, which generates a real scene archive along streets that is more complete than previously proposed route panoramas. Using a translating spherical eye, properly set planes of scanning, and unique parallel-central projection, we explore the image acquisition of the scene tunnel from camera selection and alignment, slit calculation, scene scanning, to image integration. The scene tunnels cover high buildings, ground, and various viewing directions and have uniformed resolutions along the street. The sequentially organized scene tunnel benefits texture mapping onto the urban models. We analyze the shape characteristics in the scene tunnels for designing visualization algorithms. After combining this with a global panorama and forward image caps, the capped scene tunnels can provide continuous views directly for virtual or real navigation in a city. We render scene tunnel dynamically by view warping, fast transmission, and flexible interaction. The compact and continuous scene tunnel facilitates model construction, data streaming, and seamless route traversing on the Internet and mobile devices.

  18. Excitation-scanning hyperspectral imaging microscope

    PubMed Central

    Favreau, Peter F.; Hernandez, Clarissa; Heaster, Tiffany; Alvarez, Diego F.; Rich, Thomas C.; Prabhat, Prashant; Leavesley, Silas J.

    2014-01-01

    Abstract. Hyperspectral imaging is a versatile tool that has recently been applied to a variety of biomedical applications, notably live-cell and whole-tissue signaling. Traditional hyperspectral imaging approaches filter the fluorescence emission over a broad wavelength range while exciting at a single band. However, these emission-scanning approaches have shown reduced sensitivity due to light attenuation from spectral filtering. Consequently, emission scanning has limited applicability for time-sensitive studies and photosensitive applications. In this work, we have developed an excitation-scanning hyperspectral imaging microscope that overcomes these limitations by providing high transmission with short acquisition times. This is achieved by filtering the fluorescence excitation rather than the emission. We tested the efficacy of the excitation-scanning microscope in a side-by-side comparison with emission scanning for detection of green fluorescent protein (GFP)-expressing endothelial cells in highly autofluorescent lung tissue. Excitation scanning provided higher signal-to-noise characteristics, as well as shorter acquisition times (300  ms/wavelength band with excitation scanning versus 3  s/wavelength band with emission scanning). Excitation scanning also provided higher delineation of nuclear and cell borders, and increased identification of GFP regions in highly autofluorescent tissue. These results demonstrate excitation scanning has utility in a wide range of time-dependent and photosensitive applications. PMID:24727909

  19. Excitation-scanning hyperspectral imaging microscope.

    PubMed

    Favreau, Peter F; Hernandez, Clarissa; Heaster, Tiffany; Alvarez, Diego F; Rich, Thomas C; Prabhat, Prashant; Leavesley, Silas J

    2014-04-01

    Hyperspectral imaging is a versatile tool that has recently been applied to a variety of biomedical applications, notably live-cell and whole-tissue signaling. Traditional hyperspectral imaging approaches filter the fluorescence emission over a broad wavelength range while exciting at a single band. However, these emission-scanning approaches have shown reduced sensitivity due to light attenuation from spectral filtering. Consequently, emission scanning has limited applicability for time-sensitive studies and photosensitive applications. In this work, we have developed an excitation-scanning hyperspectral imaging microscope that overcomes these limitations by providing high transmission with short acquisition times. This is achieved by filtering the fluorescence excitation rather than the emission. We tested the efficacy of the excitation-scanning microscope in a side-by-side comparison with emission scanning for detection of green fluorescent protein (GFP)-expressing endothelial cells in highly autofluorescent lung tissue. Excitation scanning provided higher signal-to-noise characteristics, as well as shorter acquisition times (300  ms/wavelength band with excitation scanning versus 3  s/wavelength band with emission scanning). Excitation scanning also provided higher delineation of nuclear and cell borders, and increased identification of GFP regions in highly autofluorescent tissue. These results demonstrate excitation scanning has utility in a wide range of time-dependent and photosensitive applications.

  20. An interchangeable scanning Hall probe/scanning SQUID microscope

    SciTech Connect

    Tang, Chiu-Chun; Lin, Hui-Ting; Wu, Sing-Lin; Chen, Tse-Jun; Wang, M. J.; Ling, D. C.; Chi, C. C.; Chen, Jeng-Chung

    2014-08-15

    We have constructed a scanning probe microscope for magnetic imaging, which can function as a scanning Hall probe microscope (SHPM) and as a scanning SQUID microscope (SSM). The scanning scheme, applicable to SHPM and SSM, consists of a mechanical positioning (sub) micron-XY stage and a flexible direct contact to the sample without a feedback control system for the Z-axis. With the interchangeable capability of operating two distinct scanning modes, our microscope can incorporate the advantageous functionalities of the SHPM and SSM with large scan range up to millimeter, high spatial resolution (⩽4 μm), and high field sensitivity in a wide range of temperature (4.2 K-300 K) and magnetic field (10{sup −7} T-1 T). To demonstrate the capabilities of the system, we present magnetic images scanned with SHPM and SSM, including a RbFeB magnet and a nickel grid pattern at room temperature, surface magnetic domain structures of a La{sub 2/3}Ca{sub 1/3}MnO{sub 3} thin film at 77 K, and superconducting vortices in a striped niobium film at 4.2 K.

  1. Photon emission from gold surfaces in air using scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Gallagher, Mark J.; Howells, Sam; Yi, Leon; Chen, Ting; Sarid, Dror

    1992-11-01

    Photon emission was observed at the tunnel junction of a scanning tunneling microscope while scanning Au structures in air. Emission levels of about 4000 counts per second (cps) were routinely achieved with Au tips, allowing photon maps to be produced. The similarity between these photon maps and the topographic images of the Au samples are discussed.

  2. A nanoscale gigahertz source realized with Josephson scanning tunneling microscopy

    SciTech Connect

    Jäck, Berthold Eltschka, Matthias; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R.; Hardock, Andreas; Kern, Klaus

    2015-01-05

    Using the AC Josephson effect in the superconductor-vacuum-superconductor tunnel junction of a scanning tunneling microscope (STM), we demonstrate the generation of GHz radiation. With the macroscopic STM tip acting as a λ/4-monopole antenna, we first show that the atomic scale Josephson junction in the STM is sensitive to its frequency-dependent environmental impedance in the GHz regime. Further, enhancing Cooper pair tunneling via excitations of the tip eigenmodes, we are able to generate high-frequency radiation. We find that for vanadium junctions, the enhanced photon emission can be tuned from about 25 GHz to 200 GHz and that large photon flux in excess of 10{sup 20 }cm{sup −2} s{sup −1} is reached in the tunnel junction. These findings demonstrate that the atomic scale Josephson junction in an STM can be employed as a full spectroscopic tool for GHz frequencies on the atomic scale.

  3. Vertically aligned nanostructure scanning probe microscope tips

    DOEpatents

    Guillorn, Michael A.; Ilic, Bojan; Melechko, Anatoli V.; Merkulov, Vladimir I.; Lowndes, Douglas H.; Simpson, Michael L.

    2006-12-19

    Methods and apparatus are described for cantilever structures that include a vertically aligned nanostructure, especially vertically aligned carbon nanofiber scanning probe microscope tips. An apparatus includes a cantilever structure including a substrate including a cantilever body, that optionally includes a doped layer, and a vertically aligned nanostructure coupled to the cantilever body.

  4. Nonlinear femtosecond laser induced scanning tunneling microscopy.

    PubMed

    Dey, Shirshendu; Mirell, Daniel; Perez, Alejandro Rodriguez; Lee, Joonhee; Apkarian, V Ara

    2013-04-21

    We demonstrate ultrafast laser driven nonlinear scanning tunneling microscopy (STM), under ambient conditions. The design is an adaptation of the recently introduced cross-polarized double beat method, whereby z-polarized phase modulated fields are tightly focused at a tunneling junction consisting of a sharp tungsten tip and an optically transparent gold film as substrate. We demonstrate the prerequisites for ultrafast time-resolved STM through an operative mechanism of nonlinear laser field-driven tunneling. The spatial resolution of the nonlinear laser driven STM is determined by the local field intensity. Resolution of 0.3 nm-10 nm is demonstrated for the intensity dependent, exponential tunneling range. The demonstration is carried out on a junction consisting of tungsten tip and gold substrate. Nano-structured gold is used for imaging purposes, to highlight junction plasmon controlled tunneling in the conductivity limit.

  5. Macroscopic model of scanning force microscope

    DOEpatents

    Guerra-Vela, Claudio; Zypman, Fredy R.

    2004-10-05

    A macroscopic version of the Scanning Force Microscope is described. It consists of a cantilever under the influence of external forces, which mimic the tip-sample interactions. The use of this piece of equipment is threefold. First, it serves as direct way to understand the parts and functions of the Scanning Force Microscope, and thus it is effectively used as an instructional tool. Second, due to its large size, it allows for simple measurements of applied forces and parameters that define the state of motion of the system. This information, in turn, serves to compare the interaction forces with the reconstructed ones, which cannot be done directly with the standard microscopic set up. Third, it provides a kinematics method to non-destructively measure elastic constants of materials, such as Young's and shear modules, with special application for brittle materials.

  6. Molecular structure of DNA by scanning tunneling microscopy.

    PubMed

    Cricenti, A; Selci, S; Felici, A C; Generosi, R; Gori, E; Djaczenko, W; Chiarotti, G

    1989-09-15

    Uncoated DNA molecules marked with an activated tris(l-aziridinyl) phosphine oxide (TAPO) solution were deposited on gold substrates and imaged in air with the use of a high-resolution scanning tunneling microscope (STM). Constant-current and gap-modulated STM images show clear evidence of the helicity of the DNA structure: pitch periodicity ranges from 25 to 35 angstroms, whereas the average diameter is 20 angstroms. Molecular structure within a single helix turn was also observed.

  7. Molecular Structure of DNA by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Cricenti, A.; Selci, S.; Felici, A. C.; Generosi, R.; Gori, E.; Djaczenko, W.; Chiarotti, G.

    1989-09-01

    Uncoated DNA molecules marked with an activated tris(1-aziridinyl) phosphine oxide (TAPO) solution were deposited on gold substrates and imaged in air with the use of a high-resolution scanning tunneling microscope (STM). Constant-current and gap-modulated STM images show clear evidence of the helicity of the DNA structure: pitch periodicity ranges from 25 and 35 angstroms, whereas the average diameter is 20 angstroms. Molecular structure within a single helix turn was also observed.

  8. Development of Scanning Ultrafast Electron Microscope Capability.

    SciTech Connect

    Collins, Kimberlee Chiyoko; Talin, Albert Alec; Chandler, David W.; Michael, Joseph R.

    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.

  9. Scanning electron microscope view of iron crystal

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A scanning electron microscope photograph of iron crystals which grow in a small vug or cavity in a recrystallized breccia (fragmented rock) from the Apollo 15 Hadley-Apennino lunar landing site. The largest crystal is three microns across. Perfectly developed crystals such as these indicate slow formation from a hot vapor as the rock was cooling. The crystals are resting on an interlocking lattice of pyroxene (calsium-magnesium-iron silicate).

  10. Nanofabrication with the Scanning Tunneling Microscope

    SciTech Connect

    Shedd, G.M.; Russell, P.E.

    1988-12-01

    The Precision Engineering Center has recently begun a research program into applications of STM to Nanotechnology. Few tools permit humans to control events and processes at the manometer level, and of those, the STM is the most well-suited to the task. A versatile new ultra-high-vacuum (UHV) STM is being built to study the use of STM for the manipulation of nanometer-scale particles. Part of the STM`s usefulness will be due to its being positioned directly beneath the focused ion beam (FIB). The interface of the STM with the FIB will allow the STM to take advantage of the FIB for long-range imaging and as a particle source; the FIB can in turn use the STM for in situ, high-resolution imaging of micromachined features.

  11. Manipulation of subsurface carbon nanoparticles in Bi2Sr2CaCu2O8+δ using a scanning tunneling microscope

    SciTech Connect

    Stollenwerk, A. J.; Hurley, N.; Beck, B.; Spurgeon, K.; Kidd, T. E.; Gu, G.

    2015-03-19

    In this study, we present evidence that subsurface carbon nanoparticles in Bi₂Sr₂CaCu₂O8+δ can be manipulated with nanometer precision using a scanning tunneling microscope. High resolution images indicate that most of the carbon particles remain subsurface after transport observable as a local increase in height as the particle pushes up on the surface. Tunneling spectra in the vicinity of these protrusions exhibit semiconducting characteristics with a band gap of approximately 1.8 eV, indicating that the incorporation of carbon locally alters the electronic properties near the surface.

  12. Observation of Superlubricity by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Hirano, Motohisa; Shinjo, Kazumasa; Kaneko, Reizo; Murata, Yoshitada

    1997-02-01

    Experimental evidence of superlubricity, the state of vanishing friction, is obtained by examining systems of sliding atomically clean surfaces by using ultrahigh vacuum scanning tunneling microscopy. The experimental results agree with theoretical predictions: Friction is not observed in the superlubricity regime in measurements capable of resolving a friction force of 3×10-9 N, whereas friction of 8×10-8 N, which is comparable to theoretical values, is observed in the friction regime.

  13. Sensitivity Improvement and Cryogenic Application of Scanning Microwave Microscope

    NASA Astrophysics Data System (ADS)

    Takahashi, Hideyuki; Imai, Yoshinori; Maeda, Atsutaka

    2015-03-01

    The technique to probe the spatial distribution of electric properties has been more important in modern material science. Scanning near-field microwave microscope (SMM) can be a powerful tool to study inhomogeneous materials. Recently we have developed scanning tunneling/microwave microscope (STM/SMM) with high sensitivity. The SMM probe is a modified coaxial resonator whose resonant frequency is 10.7 GHz and Q-factor is 1200-1300 at room temperature. It is applicable to measurements at cryogenic environment. By downsizing the resonator probe, we achieved stable operation down to liquid helium temperature. Q-factor is enhanced to 2000-3000 below 77 K. As an example of application of our STM-SMM, we present the study on inhomogeneous iron-based superconductor KxFeySe2. We successfully observed the characteristic mesoscopic phase separation of the metallic phase and the semiconducting phase by two different scanning modes; constant current mode and constant Q-factor mode. The spatial resolution is no worse than 200nm, which is comparable to curvature radius of a probe tip.

  14. Observation of diamond turned OFHC copper using Scanning Tunneling Microscopy

    SciTech Connect

    Grigg, D.A.; Russell, P.E.; Dow, T.A.

    1988-12-01

    Diamond turned OFHC copper samples have been observed within the past few months using the Scanning Tunneling Microscope. Initial results have shown evidence of artifacts which may be used to better understand the diamond turning process. The STM`s high resolution capability and three dimensional data representation allows observation and study of surface features unobtainable with conventional profilometry systems. Also, the STM offers a better quantitative means by which to analyze surface structures than the SEM. This paper discusses findings on several diamond turned OFHC copper samples having different cutting conditions. Each sample has been cross referenced using STM and SEM.

  15. Conductivity map from scanning tunneling potentiometry

    NASA Astrophysics Data System (ADS)

    Zhang, Hao; Li, Xianqi; Chen, Yunmei; Durand, Corentin; Li, An-Ping; Zhang, X.-G.

    2016-08-01

    We present a novel method for extracting two-dimensional (2D) conductivity profiles from large electrochemical potential datasets acquired by scanning tunneling potentiometry of a 2D conductor. The method consists of a data preprocessing procedure to reduce/eliminate noise and a numerical conductivity reconstruction. The preprocessing procedure employs an inverse consistent image registration method to align the forward and backward scans of the same line for each image line followed by a total variation (TV) based image restoration method to obtain a (nearly) noise-free potential from the aligned scans. The preprocessed potential is then used for numerical conductivity reconstruction, based on a TV model solved by accelerated alternating direction method of multiplier. The method is demonstrated on a measurement of the grain boundary of a monolayer graphene, yielding a nearly 10:1 ratio for the grain boundary resistivity over bulk resistivity.

  16. Shear-mode scanning capacitance microscope

    NASA Astrophysics Data System (ADS)

    Naitou, Yuichi; Ookubo, Norio

    2001-05-01

    Scanning capacitance microscope (SCM) is developed using an all-metallic probe, whose distance from the sample is controlled by detecting the shear-force drag on the laterally oscillating probe. The oscillatory motion of the probe is electromechanically excited and detected. Using this SCM, a set of images of topography, dC/dV, and dC/dX is simultaneously obtained, where C and V are, respectively, capacitance and applied voltage between the probe and the sample, and X is the coordinate along probe tip oscillation. The SCM developed shows sensitivity for dC/dV higher than the conventional SCM. The dC/dX image clearly indicates the built-in depletion region due to the p-n junction.

  17. Subsurface Imaging with the Scanning Microwave Microscope

    NASA Astrophysics Data System (ADS)

    Kopanski, Joseph; You, Lin; Michelson, Jonathan; Hitz, Emily; Obeng, Yaw; Back End of the Line Reliability; Metrology Project Team

    2015-03-01

    The scanning microwave microscope (SMM) forms images from the reflected amplitude and phase of an incident RF (~ 2.3 GHz) signal. The reflected signal is a function of the properties of the tip-sample contact, but can also be influenced by buried interfaces and subsurface variations of the sample permittivity. This mechanism allows limited imaging of conductors buried within dielectrics, voids within metal, or multiple metal layers with different permittivity. Subsurface SMM data acquisition modes include passive and various active data acquisition modes. The theory of sub-surface imaging with SMM and COMSOL multi-physics simulations of specific situations will be presented. Measurements of specifically designed test structures and correlation with simulations show the sensitivity and resolution of the technique applied to imaging subsurface metal lines embedded in dielectric. Applications include metrology for back end of the line (BEOL) multi-level metallization and three-dimensional integrated circuits (3D-ICs).

  18. Scanning Tunneling Microscopy Observation of Phonon Condensate.

    PubMed

    Altfeder, Igor; Voevodin, Andrey A; Check, Michael H; Eichfeld, Sarah M; Robinson, Joshua A; Balatsky, Alexander V

    2017-02-22

    Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature.

  19. Scanning Tunneling Microscopy Observation of Phonon Condensate

    PubMed Central

    Altfeder, Igor; Voevodin, Andrey A.; Check, Michael H.; Eichfeld, Sarah M.; Robinson, Joshua A.; Balatsky, Alexander V.

    2017-01-01

    Using quantum tunneling of electrons into vibrating surface atoms, phonon oscillations can be observed on the atomic scale. Phonon interference patterns with unusually large signal amplitudes have been revealed by scanning tunneling microscopy in intercalated van der Waals heterostructures. Our results show that the effective radius of these phonon quasi-bound states, the real-space distribution of phonon standing wave amplitudes, the scattering phase shifts, and the nonlinear intermode coupling strongly depend on the presence of defect-induced scattering resonance. The observed coherence of these quasi-bound states most likely arises from phase- and frequency-synchronized dynamics of all phonon modes, and indicates the formation of many-body condensate of optical phonons around resonant defects. We found that increasing the strength of the scattering resonance causes the increase of the condensate droplet radius without affecting the condensate fraction inside it. The condensate can be observed at room temperature. PMID:28225066

  20. Scanning tunneling microscopy studies of diamond films and optoelectronic materials

    NASA Technical Reports Server (NTRS)

    Perez, Jose M.

    1993-01-01

    In this report, we report on progress achieved from 12/1/92 to 10/1/93 under the grant entitled 'Scanning Tunneling Microscopy Studies of Diamond Films and Optoelectronic Materials'. We have set-up a chemical vapor deposition (CVD) diamond film growth system and a Raman spectroscopy system to study the nucleation and growth of diamond films with atomic resolution using scanning tunneling microscopy (STM). A unique feature of the diamond film growth system is that diamond films can be transferred directly to the ultrahigh vacuum (UHV) chamber of a scanning tunneling microscope without contaminating the films by exposure to air. The University of North Texas (UNT) provided $20,000 this year as matching funds for the NASA grant to purchase the diamond growth system. In addition, UNT provided a Coherent Innova 90S Argon ion laser, a Spex 1404 double spectrometer, and a Newport optical table costing $90,000 to set-up the Raman spectroscopy system. The CVD diamond growth system and Raman spectroscopy system will be used to grow and characterize diamond films with atomic resolution using STM as described in our proposal. One full-time graduate student and one full-time undergraduate student are supported under this grant. In addition, several graduate and undergraduate students were supported during the summer to assist in setting-up the diamond growth and Raman spectroscopy systems. We have obtained research results concerning STM of the structural and electronic properties of CVD grown diamond films, and STM and scanning tunneling spectroscopy of carbon nanotubes. In collaboration with the transmission electron microscopy (TEM) group at UNT, we have also obtained results concerning the optoelectronic material siloxene. These results were published in refereed scientific journals, submitted for publication, and presented as invited and contributed talks at scientific conferences.

  1. Charge-Density Waves Observed with a Tunneling Microscope.

    DTIC Science & Technology

    2014-09-26

    RD-R158 779 CHRGE-DENSITY UAVES OBSERVED WITH A TUNNELING / NICROSCOPE(U) CALIFORNIA UNIV SANTA BARBARA DEPT OF PHYSICS R V COLEMAN ET AL. 91 JUL 85...Physical review Letters, lyAg t195 IS, KEY WORDS (Continue On reverse aide of necessary md identify by block nimbe) Charge Density, waves, tunneling ...showe only atoms. The tunneling microscope was ooerated under licuid nitrogen with a Pt(O3 1 02 tp for both types of samples.. D OR",m3 1473 EDITION

  2. Development and application of multiple-probe scanning probe microscopes.

    PubMed

    Nakayama, Tomonobu; Kubo, Osamu; Shingaya, Yoshitaka; Higuchi, Seiji; Hasegawa, Tsuyoshi; Jiang, Chun-Sheng; Okuda, Taichi; Kuwahara, Yuji; Takami, Kazuhiro; Aono, Masakazu

    2012-04-03

    In the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequently modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.

  3. Development and Application of Multiple-Probe Scanning Probe Microscopes

    SciTech Connect

    Nakayama, T.; Kubo, O.; Shingaya, Y.; Higuchi, S.; Hasegawa, T.; Jiang, C. S.; Okuda, T.; Kuwahara, Y.; Takami, K.; Aono, M.

    2012-04-03

    the research of advanced materials based on nanoscience and nanotechnology, it is often desirable to measure nanoscale local electrical conductivity at a designated position of a given sample. For this purpose, multiple-probe scanning probe microscopes (MP-SPMs), in which two, three or four scanning tunneling microscope (STM) or atomic force microscope (AFM) probes are operated independently, have been developed. Each probe in an MP-SPM is used not only for observing high-resolution STM or AFM images but also for forming an electrical contact enabling nanoscale local electrical conductivity measurement. The world's first double-probe STM (DP-STM) developed by the authors, which was subsequently modified to a triple-probe STM (TP-STM), has been used to measure the conductivities of one-dimensional metal nanowires and carbon nanotubes and also two-dimensional molecular films. A quadruple-probe STM (QP-STM) has also been developed and used to measure the conductivity of two-dimensional molecular films without the ambiguity of contact resistance between the probe and sample. Moreover, a quadruple-probe AFM (QP-AFM) with four conductive tuning-fork-type self-detection force sensing probes has been developed to measure the conductivity of a nanostructure on an insulating substrate. A general-purpose computer software to control four probes at the same time has also been developed and used in the operation of the QP-AFM. These developments and applications of MP-SPMs are reviewed in this paper.

  4. Imaging of buried phosphorus nanostructures in silicon using scanning tunneling microscopy

    SciTech Connect

    Oberbeck, Lars; Reusch, Thilo C. G.; Hallam, Toby; Simmons, Michelle Y. E-mail: michelle.simmons@unsw.edu.au; Schofield, Steven R.; Curson, Neil J. E-mail: michelle.simmons@unsw.edu.au

    2014-06-23

    We demonstrate the locating and imaging of single phosphorus atoms and phosphorus dopant nanostructures, buried beneath the Si(001) surface using scanning tunneling microscopy. The buried dopant nanostructures have been fabricated in a bottom-up approach using scanning tunneling microscope lithography on Si(001). We find that current imaging tunneling spectroscopy is suited to locate and image buried nanostructures at room temperature and with residual surface roughness present. From these studies, we can place an upper limit on the lateral diffusion during encapsulation with low-temperature Si molecular beam epitaxy.

  5. Scanning Tunneling Microscopy of SILICON(100) 2 X 1

    NASA Astrophysics Data System (ADS)

    Hubacek, Jerome S.

    1992-01-01

    The Si(100) 2 x 1 surface, a technologically important surface in microelectronics and silicon molecular beam epitaxy (MBE), has been studied with the scanning tunneling microscope (STM) to attempt to clear up the controversy that surrounds previous studies of this surface. To this end, an ultra-high vacuum (UHV) STM/surface science system has been designed and constructed to study semiconductor surfaces. Clean Si(100) 2 x 1 surfaces have been prepared and imaged with the STM. Atomic resolution images probing both the filled states and empty states indicate that the surface consists of statically buckled dimer rows. With electronic device dimensions shrinking to smaller and smaller sizes, the Si-SiO_2 interface is becoming increasingly important and, although it is the most popular interface used in the microelectronics industry, little is known about the initial stages of oxidation of the Si(100) surface. Scanning tunneling microscopy has been employed to examine Si(100) 2 x 1 surfaces exposed to molecular oxygen in UHV. Ordered rows of bright and dark spots, rotated 45^circ from the silicon dimer rows, appear in the STM images, suggesting that the Si(100)-SiO_2 interface may be explained with a beta -cristobalite(100) structure rotated by 45^ circ on the Si(100) surface.

  6. Scanning Tunnelling Spectroscopy of Vortices with Normal and Superconducting tips

    NASA Astrophysics Data System (ADS)

    Rodrigo, J. G.; Suderow, H.; Vieira, S.

    Scanning tunnelling microscopy and spectroscopy (STM/S) has proved to be a powerful tool to study superconductivity down to atomic level. Vortex lattice studies require characterizing areas of enough size to contain a large number of vortices. On the other hand, it is necessary to combine this capability with high spectroscopic and microscopic resolution. This is a fundamental aspect to measure and detect the subtle changes appearing inside and around a single vortex. We report in this chapter our approach to the use of STM/S, using normal and superconducting tips, to observe the lattice of vortices in several compounds, and the information acquired inside these fascinating entities. The combination of superconducting tips and scanning tunneling spectroscopy, (ST)2S, presents advantages for the study of superconducting samples. It allows to distinguish relevant features of the sample density of states, which manifest itself as small changes in the Josephson coupling between sample and tip condensates, and it has also shown to be very efficient in the study of the ferromagnetic-superconductor transition in the re-entrant superconductor ErRh4B4.

  7. Simultaneous topographic and elemental chemical and magnetic contrast in scanning tunneling microscopy

    SciTech Connect

    Rose, Volker; Preissner, Curt A; Hla, Saw-Wai; Wang, Kangkang; Rosenmann, Daniel

    2014-09-30

    A method and system for performing simultaneous topographic and elemental chemical and magnetic contrast analysis in a scanning, tunneling microscope. The method and system also includes nanofabricated coaxial multilayer tips with a nanoscale conducting apex and a programmable in-situ nanomanipulator to fabricate these tips and also to rotate tips controllably.

  8. Investigating Intermolecular Interactions via Scanning Tunneling Microscopy: An Experiment for the Physical Chemistry Laboratory

    ERIC Educational Resources Information Center

    Pullman, David; Peterson, Karen I.

    2004-01-01

    A scanning tunneling microscope (STM) project designed as a module for the undergraduate physical chemistry laboratory is described. The effects of van der Waals interactions on the condensed-phase structure are examined by the analysis of the pattern of the monolayer structures.

  9. A scanning tunneling microscopy tip with a stable atomic structure

    NASA Astrophysics Data System (ADS)

    Kim, Yeong-Cheol; Seidman, David N.

    2004-02-01

    A single stable adatom on a {110}-type plane of a tungsten tip is created via field-evaporation in a field-ion microscope (FIM) operating at room temperature. This single adatom has sufficient surface mobility at room temperature and migrates, in one-dimension, along a <111>-type direction toward an edge of a {110}-type plane, due to the existence of an electric field gradient. The plane edge has a higher local electric field than its center, since it has a higher local geometric curvature. This result implies that the stable position of a single adatom during a scan of a scanning tunneling microscope (STM) tip on a surface is at the edge and not at the center of a {110}-type plane at room temperature. Therefore, the electron wave function of a tip is not symmetric and this fact should be taken into account in a careful analysis of STM images. Also a tip with a dislocation emerging at a {110}-type plane is suggested as an improved STM tip configuration, as the step at the surface, created by the intersection of the dislocation with it, is a perpetual source of single adatoms.

  10. Scanning probe microscopes go video rate and beyond

    NASA Astrophysics Data System (ADS)

    Rost, M. J.; Crama, L.; Schakel, P.; van Tol, E.; van Velzen-Williams, G. B. E. M.; Overgauw, C. F.; ter Horst, H.; Dekker, H.; Okhuijsen, B.; Seynen, M.; Vijftigschild, A.; Han, P.; Katan, A. J.; Schoots, K.; Schumm, R.; van Loo, W.; Oosterkamp, T. H.; Frenken, J. W. M.

    2005-05-01

    In this article we introduce a, video-rate, control system that can be used with any type of scanning probe microscope, and that allows frame rates up to 200images/s. These electronics are capable of measuring in a fast, completely analog mode as well as in the more conventional digital mode. The latter allows measurements at low speeds and options, such as, e.g., atom manipulation, current-voltage spectroscopy, or force-distance curves. For scanning tunneling microscope (STM) application we implemented a hybrid mode between the well-known constant-height and constant-current modes. This hybrid mode not only increases the maximum speed at which the surface can be imaged, but also improves the resolution at lower speeds. Acceptable image quality at high speeds could only be obtained by pushing the performance of each individual part of the electronics to its limit: we developed a preamplifier with a bandwidth of 600kHz, a feedback electronics with a bandwidth of 1MHz, a home-built bus structure for the fast data transfer, fast analog to digital converters, and low-noise drivers. Future improvements and extensions to the control electronics can be realized easily and quickly, because of its open architecture with its modular plug-in units. In the second part of this article we show our high-speed results. The ultrahigh vacuum application of these control electronics on our (UHV)-STM enabled imaging speeds up to 0.3mm/s, while still obtaining atomic step resolution. At high frame rates, the images suffered from noticeable distortions, which we have been able to analyze by virtue of the unique access to the error (dZ) signal. The distortions have all been associated with mechanical resonances in the scan head of the UHV-STM. In order to reduce such resonance effects, we have designed and built a scan head with high resonance frequencies (⩾64kHz), especially for the purpose of testing the fast electronics. Using this scanner we have reached video-rate imaging speeds

  11. Catalysis resolved using scanning tunnelling microscopy.

    PubMed

    Bowker, Michael

    2007-10-01

    The technique of scanning tunnelling microscopy has revolutionised our understanding of surface chemistry, due to its ability to image at the atomic and molecular scale, the very realm at which chemistry operates. This critical review focuses on its contribution to the resolution of various problems in heterogeneous catalysis, including surface structure, surface intermediates, active sites and spillover. In the article a number of images of surfaces are shown, many at atomic resolution, and the insights which these give into surface reactivity are invaluable. The article should be of interest to catalytic chemists, surface and materials scientists and those involved with nanotechnology/nanoscience. (129 references.)The graphical abstract shows the reaction between gas phase methanol and oxygen islands on Cu(110), courtesy of Philip Davies of Cardiff University. The added-row island is shown as silver-coloured spheres (copper) and red (oxygen) on the copper surface. Methanol preferentially reacts with the terminal oxygen atoms in the island forming adsorbed methoxy and OH groups. Only the terminal oxygen atoms in the island are active sites for the reaction.

  12. Edge scattering of surface plasmons excited by scanning tunneling microscopy.

    PubMed

    Zhang, Yang; Boer-Duchemin, Elizabeth; Wang, Tao; Rogez, Benoit; Comtet, Geneviève; Le Moal, Eric; Dujardin, Gérald; Hohenau, Andreas; Gruber, Christian; Krenn, Joachim R

    2013-06-17

    The scattering of electrically excited surface plasmon polaritons (SPPs) into photons at the edges of gold metal stripes is investigated. The SPPs are locally generated by the inelastic tunneling current of a scanning tunneling microscope (STM). The majority of the collected light arising from the scattering of SPPs at the stripe edges is emitted in the forward direction and is collected at large angle (close to the air-glass critical angle, θ(c)). A much weaker isotropic component of the scattered light gives rise to an interference pattern in the Fourier plane images, demonstrating that plasmons may be scattered coherently. An analysis of the interference pattern as a function of excitation position on the stripe is used to determine a value of 1.42 ± 0.18 for the relative plasmon wave vector (kSPP/k0) of the corresponding SPPs. From these results, we interpret the directional, large angle (θ~θ(c)) scattering to be mainly from plasmons on the air-gold interface, and the diffuse scattering forming interference fringes to be dominantly from plasmons on the gold-substrate interface.

  13. Spin excitations and correlations in scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Ternes, Markus

    2015-06-01

    In recent years inelastic spin-flip spectroscopy using a low-temperature scanning tunneling microscope has been a very successful tool for studying not only individual spins but also complex coupled systems. When these systems interact with the electrons of the supporting substrate correlated many-particle states can emerge, making them ideal prototypical quantum systems. The spin systems, which can be constructed by arranging individual atoms on appropriate surfaces or embedded in synthesized molecular structures, can reveal very rich spectral features. Up to now the spectral complexity has only been partly described. This manuscript shows that perturbation theory enables one to describe the tunneling transport, reproducing the differential conductance with surprisingly high accuracy. Well established scattering models, which include Kondo-like spin-spin and potential interactions, are expanded to enable calculation of arbitrary complex spin systems in reasonable time scale and the extraction of important physical properties. The emergence of correlations between spins and, in particular, between the localized spins and the supporting bath electrons are discussed and related to experimentally tunable parameters. These results might stimulate new experiments by providing experimentalists with an easily applicable modeling tool.

  14. Scanning tunneling microscopy of self-assembled viral nanostructures

    NASA Astrophysics Data System (ADS)

    Anacleto, Benjamin; Steinsultz, Nat; Sharma, Prashant

    2010-03-01

    We use scanning tunneling microscopy to investigate self-assembled monolayers of M13 bacteriophages on graphite surface. The bacteriophages we use have gold binding peptide motifs on their outer protein coat (˜1μm long, ˜10 nm diameter) allowing us to self-assemble gold nanoparticles on graphite. Using scanning tunneling microscopy we are able to resolve sub-molecular structure of the protein coat of M13 bacteriophage. Scanning tunneling spectroscopy allows us to study the binding of gold nanoparticles to the peptide motif on the bacteriophage.

  15. Study of dynamic processes on semiconductor surfaces using time-resolved scanning tunneling microscopy.

    PubMed

    Saedi, Amirmehdi; Poelsema, Bene; Zandvliet, Harold J W

    2010-07-07

    The time resolution of a conventional scanning tunneling microscope can be improved by many orders of magnitude by recording open feedback loop current-time traces. The enhanced time resolution comes, however, at the expense of the ability to obtain spatial information. In this paper, we first consider the Ge(111)-c(2 × 8) surface as an example of how surface dynamics can show up in conventional STM images. After a brief introduction to the time-resolved scanning tunneling microscopy technique, its capabilities will be demonstrated by addressing the dynamics of a dimer pair of a Pt modified Ge(001).

  16. The Scanning Electron Microscope and the Archaeologist

    ERIC Educational Resources Information Center

    Ponting, Matthew

    2004-01-01

    Images from scanning electron microscopy are now quite common and they can be of great value in archaeology. Techniques such as secondary electron imaging, backscattered electron imaging and energy-dispersive x-ray analysis can reveal information such as the presence of weevils in grain in Roman Britain, the composition of Roman coins and the…

  17. Confocal scanning beam laser microscope/macroscope: applications in fluorescence

    NASA Astrophysics Data System (ADS)

    Dixon, Arthur E.; Damaskinos, Savvas; Ribes, Alfonso

    1996-03-01

    A new confocal scanning beam laser microscope/macroscope is described that combines the rapid scan of a scanning beam laser microscope with the large specimen capability of a scanning stage microscope. This instrument combines an infinity-corrected confocal scanning laser microscope with a scanning laser macroscope that uses a telecentric f*(Theta) laser scan lens to produce a confocal imaging system with a resolution of 0.25 microns at a field of view of 25 microns and 5 microns at a field of view of 75,000 microns. The frame rate is 5 seconds per frame for a 512 by 512 pixel image, and 25 seconds for a 2048 by 2048 pixel image. Applications in fluorescence are discussed that focus on two important advantages of the instrument over a confocal scanning laser microscope: an extremely wide range of magnification, and the ability to image very large specimens. Examples are presented of fluorescence and reflected-light images of high quality printing, fluorescence images of latent fingerprints, packaging foam, and confocal autofluorescence images of a cricket.

  18. Scanning tip microwave near field microscope

    DOEpatents

    Xiang, Xiao-Dong; Schultz, Peter G.; Wei, Tao

    1998-01-01

    A microwave near field microscope has a novel microwave probe structure wherein the probing field of evanescent radiation is emitted from a sharpened metal tip instead of an aperture or gap. This sharpened tip, which is electrically and mechanically connected to a central electrode, extends through and beyond an aperture in an endwall of a microwave resonating device such as a microwave cavity resonator or a microwave stripline resonator. Since the field intensity at the tip increases as the tip sharpens, the total energy which is radiated from the tip and absorbed by the sample increases as the tip sharpens. The result is improved spatial resolution without sacrificing sensitivity.

  19. Scanning tip microwave near field microscope

    DOEpatents

    Xiang, X.D.; Schultz, P.G.; Wei, T.

    1998-10-13

    A microwave near field microscope has a novel microwave probe structure wherein the probing field of evanescent radiation is emitted from a sharpened metal tip instead of an aperture or gap. This sharpened tip, which is electrically and mechanically connected to a central electrode, extends through and beyond an aperture in an end wall of a microwave resonating device such as a microwave cavity resonator or a microwave stripline resonator. Since the field intensity at the tip increases as the tip sharpens, the total energy which is radiated from the tip and absorbed by the sample increases as the tip sharpens. The result is improved spatial resolution without sacrificing sensitivity. 17 figs.

  20. Flexible and modular virtual scanning probe microscope

    NASA Astrophysics Data System (ADS)

    Tracey, John; Federici Canova, Filippo; Keisanen, Olli; Gao, David Z.; Spijker, Peter; Reischl, Bernhard; Foster, Adam S.

    2015-11-01

    Non-contact Atomic Force Microscopy (NC-AFM) is an experimental technique capable of imaging almost any surface with atomic resolution, in a wide variety of environments. Linking measured images to real understanding of system properties is often difficult, and many studies combine experiments with detailed modelling, in particular using virtual simulators to directly mimic experimental operation. In this work we present the PyVAFM, a flexible and modular based virtual atomic force microscope capable of simulating any operational mode or set-up. Furthermore, the PyVAFM is fully expandable to allow novel and unique set-ups to be simulated, finally the PyVAFM ships with fully developed documentation and tutorial to increase usability.

  1. Dental Wear: A Scanning Electron Microscope Study

    PubMed Central

    Levrini, Luca; Di Benedetto, Giulia

    2014-01-01

    Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction. PMID:25548769

  2. Dental wear: a scanning electron microscope study.

    PubMed

    Levrini, Luca; Di Benedetto, Giulia; Raspanti, Mario

    2014-01-01

    Dental wear can be differentiated into different types on the basis of morphological and etiological factors. The present research was carried out on twelve extracted human teeth with dental wear (three teeth showing each type of wear: erosion, attrition, abrasion, and abfraction) studied by scanning electron microscopy (SEM). The study aimed, through analysis of the macro- and micromorphological features of the lesions (considering the enamel, dentin, enamel prisms, dentinal tubules, and pulp), to clarify the different clinical and diagnostic presentations of dental wear and their possible significance. Our results, which confirm current knowledge, provide a complete overview of the distinctive morphology of each lesion type. It is important to identify the type of dental wear lesion in order to recognize the contributing etiological factors and, consequently, identify other more complex, nondental disorders (such as gastroesophageal reflux, eating disorders). It is clear that each type of lesion has a specific morphology and mechanism, and further clinical studies are needed to clarify the etiological processes, particularly those underlying the onset of abfraction.

  3. Influence of mechanical noise inside a scanning electron microscope.

    PubMed

    de Faria, Marcelo Gaudenzi; Haddab, Yassine; Le Gorrec, Yann; Lutz, Philippe

    2015-04-01

    The scanning electron microscope is becoming a popular tool to perform tasks that require positioning, manipulation, characterization, and assembly of micro-components. However, some of these applications require a higher level of performance with respect to dynamics and precision of positioning. One limiting factor is the presence of unidentified noises and disturbances. This work aims to study the influence of mechanical disturbances generated by the environment and by the microscope, identifying how these can affect elements in the vacuum chamber. To achieve this objective, a dedicated setup, including a high-resolution vibrometer, was built inside the microscope. This work led to the identification and quantification of main disturbances and noise sources acting on a scanning electron microscope. Furthermore, the effects of external acoustic excitations were analysed. Potential applications of these results include noise compensation and real-time control for high accuracy tasks.

  4. Influence of mechanical noise inside a scanning electron microscope

    SciTech Connect

    Gaudenzi de Faria, Marcelo; Haddab, Yassine Le Gorrec, Yann; Lutz, Philippe

    2015-04-15

    The scanning electron microscope is becoming a popular tool to perform tasks that require positioning, manipulation, characterization, and assembly of micro-components. However, some of these applications require a higher level of performance with respect to dynamics and precision of positioning. One limiting factor is the presence of unidentified noises and disturbances. This work aims to study the influence of mechanical disturbances generated by the environment and by the microscope, identifying how these can affect elements in the vacuum chamber. To achieve this objective, a dedicated setup, including a high-resolution vibrometer, was built inside the microscope. This work led to the identification and quantification of main disturbances and noise sources acting on a scanning electron microscope. Furthermore, the effects of external acoustic excitations were analysed. Potential applications of these results include noise compensation and real-time control for high accuracy tasks.

  5. Note: Symmetric modulation methodology applied in improving the performance of scanning tunneling microscopy.

    PubMed

    Ju, Bing-Feng; Zhu, Wu-Le; Zhang, Wei

    2013-12-01

    A symmetric modulation methodology is proposed to combine robust control of external disturbance, rapid response to steep sidewalls with the high speed of a traditional scanning tunneling microscopy. The 1400 × 200 μm(2) topography of a comb-like steep sidewalls micro-structure with the depth of 23 μm was acquired at a high scanning speed of 120 μms(-1) and the detectable slope angle is up to 85°. The total measuring time was only 17 min. In addition, a 4 × 4 mm(2) aluminum dual-sinusoidal array has been successfully measured with a scanning speed up to 500 μms(-1). It improved the performance of the normal scanning tunneling microscope and enables efficient and stable measurement of large-area complex micro-structures, and thus can be introduced to engineering applications.

  6. Performance of automatic scanning microscope for nuclear emulsion experiments

    NASA Astrophysics Data System (ADS)

    Güler, A. Murat; Altınok, Özgür

    2015-12-01

    The impressive improvements in scanning technology and methods let nuclear emulsion to be used as a target in recent large experiments. We report the performance of an automatic scanning microscope for nuclear emulsion experiments. After successful calibration and alignment of the system, we have reached 99% tracking efficiency for the minimum ionizing tracks that penetrating through the emulsions films. The automatic scanning system is successfully used for the scanning of emulsion films in the OPERA experiment and plan to use for the next generation of nuclear emulsion experiments.

  7. Performance of automatic scanning microscope for nuclear emulsion experiments

    SciTech Connect

    Güler, A. Murat; Altınok, Özgür

    2015-12-31

    The impressive improvements in scanning technology and methods let nuclear emulsion to be used as a target in recent large experiments. We report the performance of an automatic scanning microscope for nuclear emulsion experiments. After successful calibration and alignment of the system, we have reached 99% tracking efficiency for the minimum ionizing tracks that penetrating through the emulsions films. The automatic scanning system is successfully used for the scanning of emulsion films in the OPERA experiment and plan to use for the next generation of nuclear emulsion experiments.

  8. Infrared spectroscopy of molecular submonolayers on surfaces by infrared scanning tunneling microscopy: tetramantane on Au111.

    PubMed

    Pechenezhskiy, Ivan V; Hong, Xiaoping; Nguyen, Giang D; Dahl, Jeremy E P; Carlson, Robert M K; Wang, Feng; Crommie, Michael F

    2013-09-20

    We have developed a new scanning-tunneling-microscopy-based spectroscopy technique to characterize infrared (IR) absorption of submonolayers of molecules on conducting crystals. The technique employs a scanning tunneling microscope as a precise detector to measure the expansion of a molecule-decorated crystal that is irradiated by IR light from a tunable laser source. Using this technique, we obtain the IR absorption spectra of [121]tetramantane and [123]tetramantane on Au(111). Significant differences between the IR spectra for these two isomers show the power of this new technique to differentiate chemical structures even when single-molecule-resolved scanning tunneling microscopy (STM) images look quite similar. Furthermore, the new technique was found to yield significantly better spectral resolution than STM-based inelastic electron tunneling spectroscopy, and to allow determination of optical absorption cross sections. Compared to IR spectroscopy of bulk tetramantane powders, infrared scanning tunneling microscopy (IRSTM) spectra reveal narrower and blueshifted vibrational peaks for an ordered tetramantane adlayer. Differences between bulk and surface tetramantane vibrational spectra are explained via molecule-molecule interactions.

  9. [Application of confocal laser scanning microscope in forensic pathology].

    PubMed

    Zhuo, Luo; Hu, Le-Sheng; Zhou, Lan; Zheng, Na; Liang, Man; Yang, Fan; Liu, Liang

    2009-12-01

    Confocal laser scanning microscopy(CLSM) is a new technique for microscopic imaging, which can collect the transverse section image of the samples and produce three-dimensional reconstruction and present higher spatial resolution than the conventional light microscope. As a precision instrument for the microscopic image, it plays an important role in forensic pathology. The article reviews the recent research achievements from sudden cardiac death, bullet wound and nervous system damage, etc, and explores the potential applications of the forensic pathology research and forensic practice.

  10. Light and scanning electron microscopic report of four fractured implants.

    PubMed

    Piattelli, A; Piattelli, M; Scarano, A; Montesani, L

    1998-01-01

    Although they are fortunately rare, implant fractures can cause significant problems for both clinicians and patients. The authors present a light and scanning electron microscopic study of four fractured implants in two patients. Both patients had parafunctional habits (bruxism), hypertrophic masticatory muscles, and wear of occlusal surfaces. The scanning electron microscopic study of the fractured surfaces of all four implants showed the presence of fatigue striations. Bending overload was probably created by a combination of parafunctional forces, bone resorption, posterior location of the implants, and implant diameter.

  11. Smart align -- A new tool for robust non-rigid registration of scanning microscope data

    DOE PAGES

    Jones, Lewys; Yang, Hao; Pennycook, Timothy J.; ...

    2015-07-10

    Many microscopic investigations of materials may benefit from the recording of multiple successive images. This can include techniques common to several types of microscopy such as frame averaging to improve signal-to-noise ratios (SNR) or time series to study dynamic processes or more specific applications. In the scanning transmission electron microscope, this might include focal series for optical sectioning or aberration measurement, beam damage studies or camera-length series to study the effects of strain; whilst in the scanning tunnelling microscope, this might include bias voltage series to probe local electronic structure. Whatever the application, such investigations must begin with the carefulmore » alignment of these data stacks, an operation that is not always trivial. In addition, the presence of low-frequency scanning distortions can introduce intra-image shifts to the data. Here, we describe an improved automated method of performing non-rigid registration customised for the challenges unique to scanned microscope data specifically addressing the issues of low-SNR data, images containing a large proportion of crystalline material and/or local features of interest such as dislocations or edges. Careful attention has been paid to artefact testing of the non-rigid registration method used, and the importance of this registration for the quantitative interpretation of feature intensities and positions is evaluated.« less

  12. Smart align -- A new tool for robust non-rigid registration of scanning microscope data

    SciTech Connect

    Jones, Lewys; Yang, Hao; Pennycook, Timothy J.; Marshall, Matthew S. J.; Van Aert, Sandra; Browning, Nigel D.; Castell, Martin R.; Nellist, Peter D.

    2015-07-10

    Many microscopic investigations of materials may benefit from the recording of multiple successive images. This can include techniques common to several types of microscopy such as frame averaging to improve signal-to-noise ratios (SNR) or time series to study dynamic processes or more specific applications. In the scanning transmission electron microscope, this might include focal series for optical sectioning or aberration measurement, beam damage studies or camera-length series to study the effects of strain; whilst in the scanning tunnelling microscope, this might include bias voltage series to probe local electronic structure. Whatever the application, such investigations must begin with the careful alignment of these data stacks, an operation that is not always trivial. In addition, the presence of low-frequency scanning distortions can introduce intra-image shifts to the data. Here, we describe an improved automated method of performing non-rigid registration customised for the challenges unique to scanned microscope data specifically addressing the issues of low-SNR data, images containing a large proportion of crystalline material and/or local features of interest such as dislocations or edges. Careful attention has been paid to artefact testing of the non-rigid registration method used, and the importance of this registration for the quantitative interpretation of feature intensities and positions is evaluated.

  13. Scanning electron microscope facility for examination of radioactive materials

    SciTech Connect

    Gibson, J.R.; Braski, D.N.

    1985-02-01

    An AMRAY model 1200B scanning electron microscope was modified to permit remote examination of radioactive specimens. Features of the modification include pneumatic vibration isolation of the column, motorized stage controls, improvements for monitoring vacuum, and a system for changing filaments without entering the hot cell.

  14. Focal depth measurement of scanning helium ion microscope

    SciTech Connect

    Guo, Hongxuan; Itoh, Hiroshi; Wang, Chunmei; Zhang, Han; Fujita, Daisuke

    2014-07-14

    When facing the challenges of critical dimension measurement of complicated nanostructures, such as of the three dimension integrated circuit, characterization of the focal depth of microscopes is important. In this Letter, we developed a method for characterizing the focal depth of a scanning helium ion microscope (HIM) by using an atomic force microscope tip characterizer (ATC). The ATC was tilted in a sample chamber at an angle to the scanning plan. Secondary electron images (SEIs) were obtained at different positions of the ATC. The edge resolution of the SEIs shows the nominal diameters of the helium ion beam at different focal levels. With this method, the nominal shapes of the helium ion beams were obtained with different apertures. Our results show that a small aperture is necessary to get a high spatial resolution and high depth of field images with HIM. This work provides a method for characterizing and improving the performance of HIM.

  15. Modular Scanning Confocal Microscope with Digital Image Processing.

    PubMed

    Ye, Xianjun; McCluskey, Matthew D

    2016-01-01

    In conventional confocal microscopy, a physical pinhole is placed at the image plane prior to the detector to limit the observation volume. In this work, we present a modular design of a scanning confocal microscope which uses a CCD camera to replace the physical pinhole for materials science applications. Experimental scans were performed on a microscope resolution target, a semiconductor chip carrier, and a piece of etched silicon wafer. The data collected by the CCD were processed to yield images of the specimen. By selecting effective pixels in the recorded CCD images, a virtual pinhole is created. By analyzing the image moments of the imaging data, a lateral resolution enhancement is achieved by using a 20 × / NA = 0.4 microscope objective at 532 nm laser wavelength.

  16. Modular Scanning Confocal Microscope with Digital Image Processing

    PubMed Central

    McCluskey, Matthew D.

    2016-01-01

    In conventional confocal microscopy, a physical pinhole is placed at the image plane prior to the detector to limit the observation volume. In this work, we present a modular design of a scanning confocal microscope which uses a CCD camera to replace the physical pinhole for materials science applications. Experimental scans were performed on a microscope resolution target, a semiconductor chip carrier, and a piece of etched silicon wafer. The data collected by the CCD were processed to yield images of the specimen. By selecting effective pixels in the recorded CCD images, a virtual pinhole is created. By analyzing the image moments of the imaging data, a lateral resolution enhancement is achieved by using a 20 × / NA = 0.4 microscope objective at 532 nm laser wavelength. PMID:27829052

  17. Development of scanning electron and x-ray microscope

    SciTech Connect

    Matsumura, Tomokazu Hirano, Tomohiko Suyama, Motohiro

    2016-01-28

    We have developed a new type of microscope possessing a unique feature of observing both scanning electron and X-ray images under one unit. Unlike former X-ray microscopes using SEM [1, 2], this scanning electron and X-ray (SELX) microscope has a sample in vacuum, thus it enables one to observe a surface structure of a sample by SEM mode, to search the region of interest, and to observe an X-ray image which transmits the region. For the X-ray observation, we have been focusing on the soft X-ray region from 280 eV to 3 keV to observe some bio samples and soft materials. The resolutions of SEM and X-ray modes are 50 nm and 100 nm, respectively, at the electron energy of 7 keV.

  18. Chemical imaging of surfaces with the scanning electrochemical microscope

    NASA Astrophysics Data System (ADS)

    Bard, Allen J.; Fan, Fu-Ren F.; Pierce, David T.; Unwin, Patrick R.; Wipf, David O.; Zhou, Feimeng

    1991-10-01

    Scanning electrochemical microscopy is a scanning probe technique that is based on faradaic current changes as a small electrode is moved across the surface of a sample. The images obtained depend on the sample topography and surface reactivity. The response of the scanning electrochemical microscope is sensitive to the presence of conducting and electroactive species, which makes it useful for imaging hetrogeneous surfaces. The principles and instrumentation used to obtain images and surface reaction-kinetic information are discussed, and examples of applications to the study of electrodes, minerals, and biological samples are given.

  19. The scanning ion conductance microscope for cellular physiology.

    PubMed

    Lab, Max J; Bhargava, Anamika; Wright, Peter T; Gorelik, Julia

    2013-01-01

    The quest for nonoptical imaging methods that can surmount light diffraction limits resulted in the development of scanning probe microscopes. However, most of the existing methods are not quite suitable for studying biological samples. The scanning ion conductance microscope (SICM) bridges the gap between the resolution capabilities of atomic force microscope and scanning electron microscope and functional capabilities of conventional light microscope. A nanopipette mounted on a three-axis piezo-actuator, scans a sample of interest and ion current is measured between the pipette tip and the sample. The feedback control system always keeps a certain distance between the sample and the pipette so the pipette never touches the sample. At the same time pipette movement is recorded and this generates a three-dimensional topographical image of the sample surface. SICM represents an alternative to conventional high-resolution microscopy, especially in imaging topography of live biological samples. In addition, the nanopipette probe provides a host of added modalities, for example using the same pipette and feedback control for efficient approach and seal with the cell membrane for ion channel recording. SICM can be combined in one instrument with optical and fluorescent methods and allows drawing structure-function correlations. It can also be used for precise mechanical force measurements as well as vehicle to apply pressure with precision. This can be done on living cells and tissues for prolonged periods of time without them loosing viability. The SICM is a multifunctional instrument, and it is maturing rapidly and will open even more possibilities in the near future.

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

    ERIC Educational Resources Information Center

    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…

  1. Topography and transport properties of oligo(phenylene ethynylene) molecular wires studied by scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Dholakia, Geetha R.; Fan, Wendy; Koehne, Jessica; Han, Jie; Meyyappan, M.

    2003-01-01

    Conjugated phenylene(ethynylene) molecular wires are of interest as potential candidates for molecular electronic devices. Scanning tunneling microscopic study of the topography and current-voltage (I-V) characteristics of self-assembled monolayers of two types of molecular wires are presented here. The study shows that the topography and I-Vs, for small scan voltages, of the two wires are quite similar and that the electronic and structural changes introduced by the substitution of an electronegative N atom in the central phenyl ring of these wires does not significantly alter the self-assembly or the transport properties.

  2. 'Oxide-free' tip for scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Colton, R. J.; Baker, S. M.; Baldeschwieler, J. D.; Kaiser, W. J.

    1987-01-01

    A new tip for scanning tunneling microscopy and a tip repair procedure that allows one to reproducibly obtain atomic images of highly oriented pyrolytic graphite with previously inoperable tips are reported. The tips are shown to be relatively oxide-free and highly resistant to oxidation. The tips are fabricated with graphite by two distinct methods.

  3. Highly stable atom-tracking scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Rerkkumsup, Pongpun; Aketagawa, Masato; Takada, Koji; Togawa, Yoichi; Thinh, Nguyen Tien; Kozuma, Yosuke

    2004-04-01

    In this article, we propose a technique for highly stabilized atom-tracking control of a scanning tunneling microscope (STM) tip by referring to an atomic point on a regular crystalline surface. Our aim is to prevent jumping of the STM tip to neighboring atoms and to use it even in a noisy environment. Graphite crystal, whose lattice spacing is approximately 0.25 nm, was utilized as the reference. To improve the performance of the tracking controller against external disturbances, the influence of a disturbance on the STM under various environmental conditions was compared experimentally with the frequency response of the open-loop tracking system. The atom-tracking conditions required to avoid jumping of the STM tip are proposed and applied to the design of the tracking controller by referring to the results of the comparison. The new tracking controller consists of integrator, tracer, and limiter units. The integrator unit is designed to eliminate the steady-state error due to thermal drift. A phase-lag low-pass filter is utilized as the tracer unit to compensate for the dominant disturbance due to vibration/acoustic noise with a frequency lower than the cutoff frequency, fco, of the open-loop tracking system. To improve the phase margin condition of the controller at fco and to suppress the disturbance with a frequency higher than fco, the limiter is designed to include a phase-lead high-pass filter and a saturator whose output is less than one-half of the lattice spacing. The performance of the stabilizing technique, which is to combine the new tracking controller with enhanced STM stiffness, was evaluated using internal/external artificial disturbance generators. The experimental results show that the proposed method has a high capability for maintaining atom-tracking control without any jumping of the STM tip, even in a noisy environment.

  4. Application of in vivo laser scanning microscope in dermatology

    NASA Astrophysics Data System (ADS)

    Lademann, Juergen; Richter, H.; Otberg, N.; Lawrenz, F.; Blume-Peytavi, U.; Sterry, W.

    2003-10-01

    The state of the art of in-vivo and in-vitro penetration measurements of topically applied substances is described. Only optical techniques represent online measuring methods based on the absorption or scattering properties of the topically applied substances. Laser scanning microscopy (LSM) has become a promising method for investigations in dermatology and skin physiology, after it was possible to analyze the skin surface on any body side in-vivo. In the present paper the application of a dermatological laser scanning microscope for penetration and distribution measurements of topically applied substances is described. The intercellular and follicular penetration pathways were studied.

  5. Developments on the NMi-VSL traceable scanning probe microscope

    NASA Astrophysics Data System (ADS)

    Dirscherl, Kai; Koops, K. R.

    2003-11-01

    We will report on the progress of our project to realize a traceable Scanning Probe Microscope at the Van Swinden Laboratorium of the Nederlands Meetinstituut in the Netherlands. The traceable Atomic Force Microscope (AFM) is constructed from a separate AFM head, a 3D translation stage and an accurate 3D laser interferometer system. Nanometer uncertainty can be maintained in the entire scanning volume of 100 μm × 100 μm × 20 μm. Apart from providing direct traceability to the SI unit of length, the coordinates provided by the laser interferometer are also used in a closed loop position feedback controller to realize accurate positioning at arbitrary locations within the volume provided by the translation stage. In this paper we will emphasize the development of the control system.

  6. Multiple-probe scanning probe microscopes for nanoarchitectonic materials science

    NASA Astrophysics Data System (ADS)

    Nakayama, Tomonobu; Shingaya, Yoshitaka; Aono, Masakazu

    2016-11-01

    Nanoarchitectonic systems are of interest for utilizing a vast range of nanoscale materials for future applications requiring a huge number of elemental nanocomponents. To explore the science and technology of nanoarchitectonics, advanced characterization tools that can deal with both nanoscale objects and macroscopically extended nanosystems are demanded. Multiple-probe scanning probe microscopes (MP-SPMs) are powerful tools that meet this demand because they take the advantages of conventional scanning probe microscopes and realize atomically precise electrical measurements, which cannot be done with conventional microprobing systems widely used in characterizing materials and devices. Furthermore, an MP-SPM can be used to operate some nanoarchitectonic systems. In this review, we overview the indispensable features of MP-SPMs together with the past, present and future of MP-SPM technology.

  7. Theoretical Evaluation of Compositional Contrast of Scanning Electron Microscope Images

    NASA Astrophysics Data System (ADS)

    Kotera, Masatoshi; Yamaguchi, Satoru; Fujiwara, Takafumi; Suga, Hiroshi

    1992-12-01

    The compositional contrast in the scanning electron microscope image is calculated for Al-Cu, Si-Cu and Al-Si contacts. An electron scattering phenomenon in the specimen is simulated in a direct manner. Electron refraction at the boundary, because of the agreement of each Fermi energy at the boundary, is precisely taken into account. The backscattered electron image shows better resolution than the secondary electron image in terms of the boundary contrast when the primary electron energy is 1 keV. The signal intensity varies depending on materials adjacent to the location observed. The ultimate resolution of the compositional contrast of the scanning electron microscope can be below 1 nm.

  8. Simple high-speed confocal line-scanning microscope.

    PubMed

    Im, Kang-Bin; Han, Sumin; Park, Hwajoon; Kim, Dongsun; Kim, Beop-Min

    2005-06-27

    Using a line scan camera and an acousto-optic deflector (AOD), we constructed a high-speed confocal laser line-scanning microscope that can generate confocal images (512 x 512 pixels) with up to 191 frames/s without any mechanically moving parts. The line scanner consists of an AOD and a cylindrical lens, which creates a line focus sweeping over the sample. The measured resolutions in z (depth), x (perpendicular to line focus), and y (direction of line focus) directions are 3.3 mum, 0.7 mum and 0.9 mum, respectively, with a 50x objective lens. This confocal microscope may be useful for analyzing fast phenomena during biological and chemical interactions and for fast 3D image reconstruction.

  9. Compact scanning-force microscope using a laser diode

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; Iams, Doug; Weissenberger, Volker; Bell, L. Stephen

    1988-12-01

    The paper describes the operation of a compact scanning-force microscope in which the gradient of force acting on a vibrating tip is monitored by a diode laser and its integrated photodiode. The system does not require reflecting or focusing elements or complicated electronics. Experimental results using this system with magnetic domains on a magnetooptic storage medium attest to the feasibility of this concept.

  10. A New Multichannel Spectral Imaging Laser Scanning Confocal Microscope

    PubMed Central

    Zhang, Yunhai; Hu, Bian; Dai, Yakang; Yang, Haomin; Huang, Wei; Xue, Xiaojun; Li, Fazhi; Zhang, Xin; Jiang, Chenyu; Gao, Fei; Chang, Jian

    2013-01-01

    We have developed a new multichannel spectral imaging laser scanning confocal microscope for effective detection of multiple fluorescent labeling in the research of biological tissues. In this paper, the design and key technologies of the system are introduced. Representative results on confocal imaging, 3-dimensional sectioning imaging, and spectral imaging are demonstrated. The results indicated that the system is applicable to multiple fluorescent labeling in biological experiments. PMID:23585775

  11. Superconducting Magnet System for a Low Temperature Laser Scanning Microscope

    DTIC Science & Technology

    2006-09-22

    Our initial studies with the LTLSM bought with this equipment grant show that the intragrain critical current density crosses over with the...SUBTITLE 5a. CONTRACT NUMBER Superconducting Magnet System for a Low Temperature Laser Scanning Microscope 5b. GRANT NUMBER FA9550-05-1-0425 5c...ADDRESS(ES) 8. PERFORMING ORGANIZATION REPORT NUMBER Applied Superconductivity Center 1500 Engineering Drive University of Wisconsin -Madison Room 909

  12. Experiments on terahertz 3D scanning microscopic imaging

    NASA Astrophysics Data System (ADS)

    Zhou, Yi; Li, Qi

    2016-10-01

    Compared with the visible light and infrared, terahertz (THz) radiation can penetrate nonpolar and nonmetallic materials. There are many studies on the THz coaxial transmission confocal microscopy currently. But few researches on the THz dual-axis reflective confocal microscopy were reported. In this paper, we utilized a dual-axis reflective confocal scanning microscope working at 2.52 THz. In contrast with the THz coaxial transmission confocal microscope, the microscope adopted in this paper can attain higher axial resolution at the expense of reduced lateral resolution, revealing more satisfying 3D imaging capability. Objects such as Chinese characters "Zhong-Hua" written in paper with a pencil and a combined sheet metal which has three layers were scanned. The experimental results indicate that the system can extract two Chinese characters "Zhong," "Hua" or three layers of the combined sheet metal. It can be predicted that the microscope can be applied to biology, medicine and other fields in the future due to its favorable 3D imaging capability.

  13. Scanning Tunneling Microscopy methods for spectroscopic imaging of subsurface interfaces

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.

    1988-01-01

    A new method for spatially-resolved, spectroscopic investigation of subsurface interface structure has been developed. The method, Ballistic Electron Emission Microscopy (BEEM), is based on Scanning Tunneling Microscopy (STM) techniques. BEEM combines STM vacuum tunneling with unique ballistic electron spectroscopy capabilities. BEEM enables, for the first time, direct imaging of subsurface interface electronic properties with nanometer spatial resolution. STM topographic images of surface structure and BEEM images of subsurface properties are obtained simultaneously. BEEM capabilities are demonstrated by investigation of important metal-semiconductor interfaces.

  14. Automatic analysis for neuron by confocal laser scanning microscope

    NASA Astrophysics Data System (ADS)

    Satou, Kouhei; Aoki, Yoshimitsu; Mataga, Nobuko; Hensh, Takao K.; Taki, Katuhiko

    2005-12-01

    The aim of this study is to develop a system that recognizes both the macro- and microscopic configurations of nerve cells and automatically performs the necessary 3-D measurements and functional classification of spines. The acquisition of 3-D images of cranial nerves has been enabled by the use of a confocal laser scanning microscope, although the highly accurate 3-D measurements of the microscopic structures of cranial nerves and their classification based on their configurations have not yet been accomplished. In this study, in order to obtain highly accurate measurements of the microscopic structures of cranial nerves, existing positions of spines were predicted by the 2-D image processing of tomographic images. Next, based on the positions that were predicted on the 2-D images, the positions and configurations of the spines were determined more accurately by 3-D image processing of the volume data. We report the successful construction of an automatic analysis system that uses a coarse-to-fine technique to analyze the microscopic structures of cranial nerves with high speed and accuracy by combining 2-D and 3-D image analyses.

  15. Scanning Tunneling Microscopy Study of Atomic and Electronic Structures of PbTaSe2

    NASA Astrophysics Data System (ADS)

    Chuang, Tien-Ming; Guan, Syu-You; Chen, Peng-Jen; Chang, Tay-Rong; Sankar, Raman; Chou, Fang-Cheng; Jeng, Horng-Tay; Chang, Chia-Seng

    The non-centrosymmetric PbTaSe2 becomes superconducting at Tc = 3.7K and is proposed to have a 3D massive Dirac fermions by large spin orbital coupling. The observation of topological nodal line states has been reported by recent ARPES measurements, making this material a great candidate to investigate the coupling between topological states and superconductivity. Here we conduct detail studies on cleaved PbTaSe2 surfaces by spectroscopic imaging-scanning tunneling microscope. Our results reveal several types of cleaved surfaces, within which each exhibits distinct different LDOS from scanning tunneling spectroscopy measurements. We identify different surface terminations from their atomic structures and their corresponding electronic properties both above and below Tc. We will report the impact on superconducting properties of different surfaces, and also discuss the relation between the surface state and superconductivity.

  16. A new clustering algorithm for scanning electron microscope images

    NASA Astrophysics Data System (ADS)

    Yousef, Amr; Duraisamy, Prakash; Karim, Mohammad

    2016-04-01

    A scanning electron microscope (SEM) is a type of electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with the sample atoms, producing various signals that are collected by detectors. The gathered signals contain information about the sample's surface topography and composition. The electron beam is generally scanned in a raster scan pattern, and the beam's position is combined with the detected signal to produce an image. The most common configuration for an SEM produces a single value per pixel, with the results usually rendered as grayscale images. The captured images may be produced with insufficient brightness, anomalous contrast, jagged edges, and poor quality due to low signal-to-noise ratio, grained topography and poor surface details. The segmentation of the SEM images is a tackling problems in the presence of the previously mentioned distortions. In this paper, we are stressing on the clustering of these type of images. In that sense, we evaluate the performance of the well-known unsupervised clustering and classification techniques such as connectivity based clustering (hierarchical clustering), centroid-based clustering, distribution-based clustering and density-based clustering. Furthermore, we propose a new spatial fuzzy clustering technique that works efficiently on this type of images and compare its results against these regular techniques in terms of clustering validation metrics.

  17. Analytical scanning evanescent microwave microscope and control stage

    DOEpatents

    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.

  18. Analytical scanning evanescent microwave microscope and control stage

    DOEpatents

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

    2013-01-22

    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.

  19. Scanning optical microscope with long working distance objective

    DOEpatents

    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.

  20. Pupil engineering for a confocal reflectance line-scanning microscope

    NASA Astrophysics Data System (ADS)

    Patel, Yogesh G.; Rajadhyaksha, Milind; DiMarzio, Charles A.

    2011-03-01

    Confocal reflectance microscopy may enable screening and diagnosis of skin cancers noninvasively and in real-time, as an adjunct to biopsy and pathology. Current confocal point-scanning systems are large, complex, and expensive. A confocal line-scanning microscope, utilizing a of linear array detector can be simpler, smaller, less expensive, and may accelerate the translation of confocal microscopy in clinical and surgical dermatology. A line scanner may be implemented with a divided-pupil, half used for transmission and half for detection, or with a full-pupil using a beamsplitter. The premise is that a confocal line-scanner with either a divided-pupil or a full-pupil will provide high resolution and optical sectioning that would be competitive to that of the standard confocal point-scanner. We have developed a confocal line-scanner that combines both divided-pupil and full-pupil configurations. This combined-pupil prototype is being evaluated to determine the advantages and limitations of each configuration for imaging skin, and comparison of performance to that of commercially available standard confocal point-scanning microscopes. With the combined configuration, experimental evaluation of line spread functions (LSFs), contrast, signal-to-noise ratio, and imaging performance is in progress under identical optical and skin conditions. Experimental comparisons between divided-pupil and full-pupil LSFs will be used to determine imaging performance. Both results will be compared to theoretical calculations using our previously reported Fourier analysis model and to the confocal point spread function (PSF). These results may lead to a simpler class of confocal reflectance scanning microscopes for clinical and surgical dermatology.

  1. EDITORIAL: Three decades of scanning tunnelling microscopy that changed the course of surface science Three decades of scanning tunnelling microscopy that changed the course of surface science

    NASA Astrophysics Data System (ADS)

    Ramachandra Rao, M. S.; Margaritondo, Giorgio

    2011-11-01

    Three decades ago, with a tiny tip of platinum, the scientific world saw the real space imaging of single atoms with unprecedented spatial resolution. This signalled the birth of one of the most versatile surface probes, based on the physics of quantum mechanical tunnelling: the scanning tunnelling microscope (STM). Invented in 1981 by Gerd Binnig and Heinrich Rohrer of IBM, Zurich, it led to their award of the 1986 Nobel Prize. Atoms, once speculated to be abstract entities used by theoreticians for mere calculations, can be seen to exist for real with the nano-eye of an STM tip that also gives real-space images of molecules and adsorbed complexes on surfaces. From a very fundamental perspective, the STM changed the course of surface science and engineering. STM also emerged as a powerful tool to study various fundamental phenomena relevant to the properties of surfaces in technological applications such as tribology, medical implants, catalysis, sensors and biology—besides elucidating the importance of local bonding geometries and defects, non-periodic structures and the co-existence of nano-scale phases. Atom-level probing, once considered a dream, has seen the light with the evolution of STM. An important off-shoot of STM was the atomic force microscope (AFM) for surface mapping of insulating samples. Then followed the development of a flurry of techniques under the general name of scanning probe microscopy (SPM). These techniques (STM, AFM, MFM, PFM etc) designed for atomic-scale-resolution imaging and spectroscopy, have led to brand new developments in surface analysis. All of these novel methods enabled researchers in recent years to image and analyse complex surfaces on microscopic and nanoscopic scales. All of them utilize a small probe for sensing the surface. The invention of AFM by Gerd Binnig, Calvin Quate and Christopher Gerber opened up new opportunities for characterization of a variety of materials, and various industrial applications could be

  2. Scanning Nanospin Ensemble Microscope for Nanoscale Magnetic and Thermal Imaging.

    PubMed

    Tetienne, Jean-Philippe; Lombard, Alain; Simpson, David A; Ritchie, Cameron; Lu, Jianing; Mulvaney, Paul; Hollenberg, Lloyd C L

    2016-01-13

    Quantum sensors based on solid-state spins provide tremendous opportunities in a wide range of fields from basic physics and chemistry to biomedical imaging. However, integrating them into a scanning probe microscope to enable practical, nanoscale quantum imaging is a highly challenging task. Recently, the use of single spins in diamond in conjunction with atomic force microscopy techniques has allowed significant progress toward this goal, but generalization of this approach has so far been impeded by long acquisition times or by the absence of simultaneous topographic information. Here, we report on a scanning quantum probe microscope which solves both issues by employing a nanospin ensemble hosted in a nanodiamond. This approach provides up to an order of magnitude gain in acquisition time while preserving sub-100 nm spatial resolution both for the quantum sensor and topographic images. We demonstrate two applications of this microscope. We first image nanoscale clusters of maghemite particles through both spin resonance spectroscopy and spin relaxometry, under ambient conditions. Our images reveal fast magnetic field fluctuations in addition to a static component, indicating the presence of both superparamagnetic and ferromagnetic particles. We next demonstrate a new imaging modality where the nanospin ensemble is used as a thermometer. We use this technique to map the photoinduced heating generated by laser irradiation of a single gold nanoparticle in a fluid environment. This work paves the way toward new applications of quantum probe microscopy such as thermal/magnetic imaging of operating microelectronic devices and magnetic detection of ion channels in cell membranes.

  3. Theoretical study of carbon-based tips for scanning tunnelling microscopy.

    PubMed

    González, C; Abad, E; Dappe, Y J; Cuevas, J C

    2016-03-11

    Motivated by recent experiments, we present here a detailed theoretical analysis of the use of carbon-based conductive tips in scanning tunnelling microscopy. In particular, we employ ab initio methods based on density functional theory to explore a graphitic, an amorphous carbon and two diamond-like tips for imaging with a scanning tunnelling microscope (STM), and we compare them with standard metallic tips made of gold and tungsten. We investigate the performance of these tips in terms of the corrugation of the STM images acquired when scanning a single graphene sheet. Moreover, we analyse the impact of the tip-sample distance and show that it plays a fundamental role in the resolution and symmetry of the STM images. We also explore in depth how the adsorption of single atoms and molecules in the tip apexes modifies the STM images and demonstrate that, in general, it leads to an improved image resolution. The ensemble of our results provides strong evidence that carbon-based tips can significantly improve the resolution of STM images, as compared to more standard metallic tips, which may open a new line of research in scanning tunnelling microscopy.

  4. Plasma etching of superconducting Niobium tips for scanning tunneling microscopy

    SciTech Connect

    Roychowdhury, A.; Dana, R.; Dreyer, M.; Anderson, J. R.; Lobb, C. J.; Wellstood, F. C.

    2014-07-07

    We have developed a reproducible technique for the fabrication of sharp superconducting Nb tips for scanning tunneling microscopy (STM) and scanning tunneling spectroscopy. Sections of Nb wire with 250 μm diameter are dry etched in an SF₆ plasma in a Reactive Ion Etcher. The gas pressure, etching time, and applied power are chosen to control the ratio of isotropic to anisotropic etch rates and produce the desired tip shape. The resulting tips are atomically sharp, with radii of less than 100 nm, mechanically stable, and superconducting. They generate good STM images and spectroscopy on single crystal samples of Au(111), Au(100), and Nb(100), as well as a doped topological insulator Bi₂Se₃ at temperatures ranging from 30 mK to 9 K.

  5. Possible Laminographic and Tomosynthesis Applications for Wolter Microscope Scan Geometries

    SciTech Connect

    Schneberk, D; Jackson, J; Martz, H

    2004-10-05

    The Wolter microscope includes a number of attractive features for x-ray imaging, and possible connections to laminographic and tomosynthesis 3D object recovery algorithms. This type of instrument employs x-ray optics to sift out single energy x-rays from a broader spectral energy source, and direct those x-rays to a ''focus plane'' similar to the operation of a optical microscope (see Figure 1 for schematic of a Wolter instrument). Unlike optical microscopes the 3D object can be thick in the direction of the x-rays and in this case more of the intensity of the image is affected by the out-of-focus planes, since the ray-paths span the entire depth of the object. It is clear that the ''in-focus'' plane of a Wolter contain more 3D information than a simple ''point-projection'' radiograph. However, it is not clear just how the impact of the out-of-focus planes obscures or distorts features of interest for the in-focus planes. Further, it is not clear just how object positioning can be combined with multiple acquisitions to enable recovery of other planes within the object function or the entire object function. Of particular interest here are Wolter microscopes configured for mesoscale objects (mm extent with um features). Laminographic and tomosynthesis scanning methods can be strategic for this type of inspection instrument. First, photon output for inspection purposes can be meager in this type of ''small field of view'' system. With laboratory x-ray sources a single image can require up to 10 minutes to accumulate adequate signal. Techniques that can obtain 3D object information from small numbers of views, rotational or translational, are consequently at a premium. Laminographic and tomosynthesis scanning methods require relatively small numbers of views (2-30). Secondly, the Wolter microscope scan geometry in a single view is a fit with the type of source-detector geometry achieved through source-object-detector re-positioning in laminographic and tomosynthesis

  6. Scanning probe microscope simulator for the assessment of noise in scanning probe microscopy controllers

    SciTech Connect

    Wutscher, T.; Niebauer, J.; Giessibl, F. J.

    2013-07-15

    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.

  7. Scanning probe microscope simulator for the assessment of noise in scanning probe microscopy controllers

    NASA Astrophysics Data System (ADS)

    Wutscher, T.; Niebauer, J.; Giessibl, F. J.

    2013-07-01

    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.

  8. Comparison of line-scanned and point-scanned dual-axis confocal microscope performance.

    PubMed

    Wang, D; Chen, Y; Wang, Y; Liu, J T C

    2013-12-15

    The point-scanned dual-axis confocal (PS-DAC) microscope has been shown to exhibit superior capability to reject out-of-focus and multiply scattered light in comparison to its conventional single-axis counterpart. However, the slow frame rate (typically <5 Hz) resulting from point-by-point data collection makes these systems vulnerable to motion artifacts. While video-rate point-scanned confocal microscopy is possible, a line-scanned dual-axis confocal (LS-DAC) microscope provides a simpler means of achieving high-speed imaging through line-by-line data collection, but sacrifices contrast due to loss of confocality along one dimension. Here we evaluate the performance trade-offs between an LS-DAC and PS-DAC microscope with identical spatial resolutions. Characterization experiments of the LS-DAC and PS-DAC microscopes with tissue phantoms, in reflectance mode, are shown to match results from Monte Carlo scattering simulations of the systems. Fluorescence images of mouse brain vasculature, obtained using resolution-matched LS-DAC and PS-DAC microscopes, demonstrate the comparable performance of LS-DAC and PS-DAC microscopy at shallow depths.

  9. A scanning probe microscope for magnetoresistive cantilevers utilizing a nested scanner design for large-area scans

    PubMed Central

    Förste, Alexander; Tavassolizadeh, Ali; Rott, Karsten; Meyners, Dirk; Gröger, Roland; Reiss, Günter; Quandt, Eckhard; Schimmel, Thomas; Hölscher, Hendrik

    2015-01-01

    Summary We describe an atomic force microscope (AFM) for the characterization of self-sensing tunneling magnetoresistive (TMR) cantilevers. Furthermore, we achieve a large scan-range with a nested scanner design of two independent piezo scanners: a small high resolution scanner with a scan range of 5 × 5 × 5 μm3 is mounted on a large-area scanner with a scan range of 800 × 800 × 35 μm3. In order to characterize TMR sensors on AFM cantilevers as deflection sensors, the AFM is equipped with a laser beam deflection setup to measure the deflection of the cantilevers independently. The instrument is based on a commercial AFM controller and capable to perform large-area scanning directly without stitching of images. Images obtained on different samples such as calibration standard, optical grating, EPROM chip, self-assembled monolayers and atomic step-edges of gold demonstrate the high stability of the nested scanner design and the performance of self-sensing TMR cantilevers. PMID:25821686

  10. A scanning probe microscope for magnetoresistive cantilevers utilizing a nested scanner design for large-area scans.

    PubMed

    Meier, Tobias; Förste, Alexander; Tavassolizadeh, Ali; Rott, Karsten; Meyners, Dirk; Gröger, Roland; Reiss, Günter; Quandt, Eckhard; Schimmel, Thomas; Hölscher, Hendrik

    2015-01-01

    We describe an atomic force microscope (AFM) for the characterization of self-sensing tunneling magnetoresistive (TMR) cantilevers. Furthermore, we achieve a large scan-range with a nested scanner design of two independent piezo scanners: a small high resolution scanner with a scan range of 5 × 5 × 5 μm(3) is mounted on a large-area scanner with a scan range of 800 × 800 × 35 μm(3). In order to characterize TMR sensors on AFM cantilevers as deflection sensors, the AFM is equipped with a laser beam deflection setup to measure the deflection of the cantilevers independently. The instrument is based on a commercial AFM controller and capable to perform large-area scanning directly without stitching of images. Images obtained on different samples such as calibration standard, optical grating, EPROM chip, self-assembled monolayers and atomic step-edges of gold demonstrate the high stability of the nested scanner design and the performance of self-sensing TMR cantilevers.

  11. Note: A scanning thermal probe microscope that operates in liquids

    NASA Astrophysics Data System (ADS)

    Aigouy, Lionel; Lalouat, Loïc; Mortier, Michel; Löw, Peter; Bergaud, Christian

    2011-03-01

    We have developed a scanning thermal probe microscope that operates in liquid environments. The thermal sensor is a fluorescent particle glued at the end of a sharp tungsten tip. Since light emission is a strongly thermally sensitive effect, the measurement of the particle fluorescence variations allows the determination of the temperature. No electrical wiring of the probe is needed. As a demonstrative example, we have measured the temperature map of a Joule-heated microheater immersed in a water/glycerol solution. Both topographical and thermal images are obtained with a good sensitivity.

  12. Adaptive noise Wiener filter for scanning electron microscope imaging system.

    PubMed

    Sim, K S; Teh, V; Nia, M E

    2016-01-01

    Noise on scanning electron microscope (SEM) images is studied. Gaussian noise is the most common type of noise in SEM image. We developed a new noise reduction filter based on the Wiener filter. We compared the performance of this new filter namely adaptive noise Wiener (ANW) filter, with four common existing filters as well as average filter, median filter, Gaussian smoothing filter and the Wiener filter. Based on the experiments results the proposed new filter has better performance on different noise variance comparing to the other existing noise removal filters in the experiments.

  13. Characteristics of different frequency ranges in scanning electron microscope images

    SciTech Connect

    Sim, K. S. Nia, M. E.; Tan, T. L.; Tso, C. P.; Ee, C. S.

    2015-07-22

    We demonstrate a new approach to characterize the frequency range in general scanning electron microscope (SEM) images. First, pure frequency images are generated from low frequency to high frequency, and then, the magnification of each type of frequency image is implemented. By comparing the edge percentage of the SEM image to the self-generated frequency images, we can define the frequency ranges of the SEM images. Characterization of frequency ranges of SEM images benefits further processing and analysis of those SEM images, such as in noise filtering and contrast enhancement.

  14. Charge ordering in stoichiometric FeTe: Scanning tunneling microscopy and spectroscopy

    DOE PAGES

    Li, Wei; Yin, Wei -Guo; Wang, Lili; ...

    2016-01-04

    In this study, we use scanning tunneling microscopy and spectroscopy to reveal a unique stripy charge order in a parent phase of iron-based superconductors in stoichiometric FeTe epitaxy films. The charge order has unusually the same—usually half—period as the spin order. We also found highly anisotropic electron band dispersions being large and little along the ferromagnetic (crystallographic b) and antiferromagnetic (a) directions, respectively. Our data suggest that the microscopic mechanism is likely of the Stoner type driven by interatomic Coulomb repulsion Vij, and that Vij and charge fluctuations, so far much neglected, are important to the understanding of iron-based superconductors.

  15. Controlled manipulation of gadolinium-coordinated supramolecules by low-temperature scanning tunneling microscopy.

    PubMed

    Urgel, José I; Ecija, David; Auwärter, Willi; Barth, Johannes V

    2014-03-12

    Coordination bonding between para-quarterphenyl-dicarbonitrile linkers and gadolinium on Ag(111) has been exploited to construct pentameric mononuclear supramolecules, consisting of a rare-earth center surrounded by five molecular linkers. By employing a scanning tunneling microscope tip, a manipulation protocol was developed to position individual pentamers on the surface. In addition, the tip was used to extract and replace individual linkers yielding tetrameric, pentameric, nonameric, and dodecameric metallosupramolecular arrangements. These results open new avenues toward advanced nanofabrication methods and rare-earth nanochemistry by combining the versatility of metal-ligand interactions and atomistic manipulation capabilities.

  16. Sensing dipole fields at atomic steps with combined scanning tunneling and force microscopy.

    PubMed

    Park, Jeong Young; Sacha, G M; Enachescu, M; Ogletree, D F; Ribeiro, R A; Canfield, P C; Jenks, C J; Thiel, P A; Sáenz, J J; Salmeron, M

    2005-09-23

    The electric field of dipoles localized at the atomic steps of metal surfaces due to the Smoluchowski effect were measured from the electrostatic force exerted on the biased tip of a scanning tunneling microscope. By varying the tip-sample bias the contribution of the step dipole was separated from changes in the force due to van der Waals and polarization forces. Combined with electrostatic calculations, the method was used to determine the local dipole moment in steps of different heights on Au(111) and on the twofold surface of an Al-Ni-Co decagonal quasicrystal.

  17. Charge-density waves observed at 4.2 K by scanning-tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Giambattista, B.; Johnson, A.; Coleman, R. V.; Drake, B.; Hansma, P. K.

    1988-02-01

    Scanning-tunneling-microscope images of layer structure dichalcogenides exhibiting charge-density-waves (CDW's) have been studied at 4.2 K. CDW amplitudes in the 2H, 1T, and 4Hb phases of TaSe2 have been measured with the strongest CDW phase showing only the superlattice modulation while the weaker CDW phases show simultaneous CDW and surface-atom modulations. In 2H-NbSe2 a well-resolved hexagonal CDW superlattice superimposed on the dominant surface-atom pattern is observed.

  18. Scanning Acoustic Microscope of 3D-Interconnect

    NASA Astrophysics Data System (ADS)

    Wai Kong, Lay; Diebold, A. C.; Rudack, A.; Arkalgud, S.

    2009-09-01

    The College of Nanoscale Science and Engineering of the University at Albany in collaboration with International SEMATECH is investigating the use of Scanning Acoustic Microscope (SAM) for analyzing 3D Interconnects. SAM is a non-destructive metrology technique which utilizes high frequency ultrasound to generate a microscopic image of the internal parts of a specimen. The goal of this project is to develop microscopic techniques for evaluating Through-Silicon Vias (TSVs) for 3D-Interconnects. Preliminary data shows voids and other defects in the interface between bonded wafers as shown in Figure 1. Our SAM laboratory system operates at 230 MHz and has a spatial resolution of 5-10 μm and focal length of 5.9 mm on a silicon wafer. The spatial resolution and sampling depth depend on the ultrasonic frequency, sound velocity, focal length and diameter of piezoelectric crystal. Typically, the silicon wafers have a thickness of 775 μm before they are bonded. Our initial work is focused on blanket wafers in order to develop the bonding process. The next step is to bond wafers with test die where the patterning obscures the interface. This paper will discuss the limitations of SAM and compare it to infrared microscopy which is another important imaging capability for 3D Interconnect. We also discuss the current status of research into more advanced acoustic microscopy methods and how this might impact 3D Interconnect imaging.

  19. Spin-polarized scanning tunneling microscopy: breakthroughs and highlights.

    PubMed

    Bode, Matthias

    2012-01-01

    The principle of scanning tunneling microscopy, an imaging method with atomic resolution capability invented by Binnig and Rohrer in 1982, can be adapted for surface magnetism studies by using magnetic probe tips. The contrast mechanism of this so-called spin-polarized scanning tunneling microscopy, or SP-STM, relies on the tunneling magneto-resistance effect, i.e. the tip-sample distance as well as the differential conductance depend on the relative magnetic orientation of tip and sample. To illustrate the working principle and the unique capabilities of SP-STM, this compilation presents some key experiments which have been performed on various magnetic surfaces, such as the topological antiferromagnet Cr(001), a double-layer of Fe which exhibits a stripe- domain pattern with about 50 nm periodicity, and the Mn monolayer on W(110), where the combination of experiment and theory reveal an antiferromagnetic spin cycloid. Recent experimental results also demonstrate the suitability of SP-STM for studies of dynamic properties, such as the spin relaxation time of single magnetic nanostructures.

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

    PubMed

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

    2011-07-15

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    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.

  2. Orbital Selectivity in Scanning Tunneling Microscopy: Distance-Dependent Tunneling Process Observed in Iron Nitride.

    PubMed

    Takahashi, Y; Miyamachi, T; Ienaga, K; Kawamura, N; Ernst, A; Komori, F

    2016-02-05

    In scanning tunneling microscopy, orbital selectivity of the tunneling process can make the topographic image dependent on a tip-surface distance. We have found reproducible dependence of the images on the distance for a monatomic layer of iron nitride formed on a Cu(001) surface. Observed atomic images systematically change between a regular dot array and a dimerized structure depending on the tip-surface distance, which turns out to be the only relevant parameter in the image variation. An accompanied change in the weight of Fe-3d local density of states to a tunneling background was detected in dI/dV spectra. These have been attributed to a shift in surface orbitals detected by the tip from the d states to the s/p states with increasing the tip-surface distance, consistent with an orbital assignment from first-principles calculations.

  3. Ultra-Compact Multitip Scanning Probe Microscope with an Outer Diameter of 50 mm

    NASA Astrophysics Data System (ADS)

    Cherepanov, Vasily; Zubkov, Evgeny; Junker, Hubertus; Korte, Stefan; Blab, Marcus; Coenen, Peter; Voigtländer, Bert

    We present a multitip scanning tunneling microscope (STM) where four independent STM units are integrated on a diameter of 50 mm. The coarse positioning of the tips is done under the control of an optical microscope or an SEM in vacuum. The heart of this STM is a new type of piezoelectric coarse approach called Koala Drive which can have a diameter greater than 2.5 mm and a length smaller than 10 mm. Alternating movements of springs move a central tube which holds the STM tip or AFM sensor. This new operating principle provides a smooth travel sequence and avoids shaking which is intrinsically present for nanopositioners based on inertial motion with saw tooth driving signals. Inserting the Koala Drive in a piezo tube for xyz-scanning integrates a complete STM inside a 4 mm outer diameter piezo tube of <10 mm length. The use of the Koala Drive makes the scanning probe microscopy design ultra-compact and accordingly leads to a high mechanical stability. The drive is UHV, low temperature, and magnetic field compatible. The compactness of the Koala Drive allows building a four-tip STM as small as a single-tip STM with a drift of <0.2 nm/min and lowest resonance frequencies of 2.5 (xy) and 5.5 kHz (z). We present examples of the performance of the multitip STM designed using the Koala Drive.

  4. Field-Induced Reversible Phase Manipulation in Metal-Insulator Transition using Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Park, Se Jun

    2005-03-01

    Reversible electronic switching between insulating and metallic phases is a novel idea that may allow new types of field effect devices feasible.^1 Here we demonstrate the reversible manipulation between metallic and insulating phases in two-dimensional In nanowire arrays on Si(111) surface near the metal-insulator transition temperature (Tc). The electronic switching of phases was induced by local electric field applied by the probe tip of a scanning tunneling microscope. The field-dependent hysteresis behavior was also observed in tip height measurements as a function of the sample bias, under the constraint of constant tunneling current. A model including the intrinsic bi-stability of the nanometer-scale domains of In nanowire arrays will be discussed. ^1C. Ahn, J. Triscone, J. Mannhart, Nature 6952, 1015 (2003)

  5. Microscopic imaging of residual stress using a scanning phase-measuring acoustic microscope

    NASA Astrophysics Data System (ADS)

    Meeks, Steven W.; Peter, D.; Horne, D.; Young, K.; Novotny, V.

    1989-10-01

    A high-resolution scanning phase-measuring acoustic microscope (SPAM) has been developed and used to image the near-surface residual stress field around features etched in sputtered alumina via the acoustoelastic effect. This microscope operates at 670 MHz and has a resolution of 5-10 microns, depending upon the amount of defocus. Relative velocity changes of sample surface waves as small as 50 ppm are resolved. Images of the stress field at the tip of a 400-micron-wide slot etched in alumina are presented and compared with a finite element simulation. The SPAM uses an unconventional acoustic lens with an anisotropic illumination pattern which can measure anisotropic effects and map residual stress fields with several-micron resolution and a stress sensitivity of 1/3 MPa in an alumina film.

  6. Radio-frequency scanning tunneling microscopy: Instrumentation and applications to physical measurements

    NASA Astrophysics Data System (ADS)

    Kemiktarak, Utku

    The scanning tunneling microscope (STM) relies upon localized electron tunneling between a sharp probe tip and a conducting sample to attain atomic-scale spatial resolution. Perhaps the most serious obstacle in front of realizing the full potential of the STM is its inadequate temporal resolution, limited by the bandwidth of STM current detectors (˜1 kHz). To overcome this limitation, we developed a radically new approach: we embedded the tunnel junction into an inductor-capacitor resonant circuit and measured the reflection of radio-frequency waves from this circuit. Our new apparatus, which we call a radio-frequency scanning tunneling microscope (Rf-STM), allowed us to achieve 100-fold bandwidth increase upon the state-of-the-art. The bandwidth increase resulted in a number of ultrafast and sensitive measurements in nanoscale systems. First, the large bandwidth of the Rf-STM allowed acquisition of surface topography images at high speeds. In a conventional STM scan, it takes from minutes to hours to create a typical image. As the circuit bandwidth increases, one can shorten this time considerably. We showed that the Rf-STM images, collected at a rate of 100 line/s, had comparable resolution to conventional STM images taken at a rate of 1 line/s. Second, we used the Rf-STM to perform broadband electronic noise measurements. Intrinsic current fluctuations in a tunnel junction, called shot noise, gives important in formation about electron transport mechanisms. We used shot noise measurements as an absolute calibration tool for Rf-STM. Conversely, we also demonstrated how the Rf-STM could be used as a local primary thermometer. Finally, using the Rf-STM, we established the very high displacement sensitivity of a tunnel displacement detector. On a driven micro-mechanical membrane, we detected the first ten mechanical resonances, ranging in frequency from 1 MHz to 3 MHz. We also measured the displacements of a Au surface shaken by a calibrated piezoelectric actuator

  7. Scanning Tunneling Microscopic Characterization of an Engineered Organic Molecule

    DTIC Science & Technology

    2011-08-01

    attachment and wide -band MCT detector, was used. Figure 3 shows the spectra obtained for SAM of PMNBT (top), which was compared to raw crystal PMNBT...Graphite Covered with Phthalocyanine Molecules. Science , 1992, 255, 1115– 1118. 10. Stabel, A.; Herwig, P.; Mullen, K.; Rabe, J. P. Diode Like...J. J.; Dunbar, T. D.; Allara, D. L.; Weiss, P. S. Electron Transfer through Organic Molecules. J. Phys. Chem. B 1999, 103, 8122–8127. 16. Wold , D

  8. Scanning Tunneling Microscopy analysis of space-exposed polymer films

    NASA Technical Reports Server (NTRS)

    Kalil, Carol R.; Young, Philip R.

    1993-01-01

    The characterization of the surface of selected space-exposed polymer films by Scanning Tunneling Microscopy (STM) is reported. Principles of STM, an emerging new technique for materials analysis, are reviewed. The analysis of several films which received up to 5.8 years of low Earth orbital (LEO) exposure onboard the NASA Long Duration Exposure Facility (LDEF) is discussed. Specimens included FEP Teflon thermal blanket material, Kapton film, and several experimental polymer films. Ultraviolet and atomic oxygen-induced crazing and erosion are described. The intent of this paper is to demonstrate how STM is enhancing the understanding of LEO space environmental effects on polymer films.

  9. Scanning tunneling luminescence of individual CdSe nanowires.

    PubMed

    Lutz, Theresa; Kabakchiev, Alexander; Dufaux, Thomas; Wolpert, Christian; Wang, Zhe; Burghard, Marko; Kuhnke, Klaus; Kern, Klaus

    2011-08-22

    The local luminescence properties of individual CdSe nanowires composed of segments of zinc blende and wurtzite crystal structures are investigated by low-temperature scanning tunneling luminescence spectroscopy. Light emission from the wires is achieved by the direct injection of holes and electrons, without the need for coupling to tip-induced plasmons in the underlying metal substrate. The photon energy is found to increase with decreasing wire diameter due to exciton confinement. The bulk bandgap extrapolated from the energy versus diameter dependence is consistent with photon emission from the zinc blende-type CdSe sections.

  10. Scanning electron microscopic observations of Anopheles albimanus (Diptera: Culicidae) eggs.

    PubMed

    Rodriguez, M H; Chavez, B; Orozco, A; Loyola, E G; Martinez-Palomo, A

    1992-05-01

    To investigate the existence of subspecies of Anopheles albimanus Wiedeman in southern Mexico, the egg morphology of specimens obtained from several field populations and from insectary-adapted colonies of uniform pupal phenotype was examined. Scanning electron microscopic observations have shown that the eggs of An. albimanus are polymorphic in respect to the size and shape of their floats, but not in their ornamentation. Four types of eggs were found. Differences in the proportion of the various morphological types were statistically significant, although proportions of egg types were variable among individuals within the same population. These observations are suggestive of distinctive populations and warrant further studies using more sensitive methods to investigate sibling species in An. albimanus sensu lato.

  11. An improved visual tracking method in scanning electron microscope.

    PubMed

    Ru, Changhai; Zhang, Yong; Huang, Haibo; Chen, Tao

    2012-06-01

    Since their invention, nanomanipulation systems in scanning electron microscopes (SEMs) have provided researchers with an increasing ability to interact with objects at the nanoscale. However, most nanomanipulators that are capable of generating nanometer displacement operate in an open-loop without suitable feedback mechanisms. In this article, a robust and effective tracking framework for visual servoing applications is presented inside an SEM to achieve more precise tracking manipulation and measurement. A subpixel template matching tracking algorithm based on contour models in the SEM has been developed to improve the tracking accuracy. A feed-forward controller is integrated into the control system to improve the response time. Experimental results demonstrate that a subpixel tracking accuracy is realized. Furthermore, the robustness against clutter can be achieved even in a challenging tracking environment.

  12. Design and manufacturing of scanning probe acoustic microscope test phantom

    NASA Astrophysics Data System (ADS)

    Chen, Xiaohui; Fang, Xiaoyue; Song, Jitao; Ding, Mingyue

    2015-03-01

    Acquiring nondestructive internal structures acoustic image as well as the morphology images using scanning probe acoustic microscope (SPAM) is a challenge and no known metrology tools to identify the ultrasonic internal resolution and detectable depth of SPAM in a nondestructive way. Monitoring these defects necessitates the identification of their technical parameters of SPAM. In this paper, the specific materials (test phantoms) were designed and processed so that the ultrasound internal resolution of SPAM in nondestructive imaging of the embedded or buried substructures as well as the morphology images were measured. Experimental results demonstrated the successful identification of embedded or buried defects under the test phantom with the resolution of 50nm for SPAM as well as the detectable depth of more than 100μm.

  13. High-voltage scanning ion microscope: Beam optics and design

    NASA Astrophysics Data System (ADS)

    Magilin, D.; Ponomarev, A.; Rebrov, V.; Ponomarov, A.

    2015-05-01

    This article is devoted to the conceptual design of a compact high-voltage scanning ion microscope (HVSIM). In an HVSIM design, the ion optical system is based on a high-brightness ion source. Specifically, the ion optical system is divided into two components: an ion injector and a probe-forming system (PFS) that consists of an accelerating tube and a multiplet of quadrupole lenses. The crossover is formed and controlled by the injector, which acts as an object collimator, and is focused on the image plane by the PFS. The ion microprobe has a size of 0.1 μm and an energy of 2 MeV. When the influence of the chromatic and third-order aberrations is theoretically taken into account, the HVSIM forms an ion microprobe.

  14. In situ laser processing in a scanning electron microscope

    SciTech Connect

    Roberts, Nicholas; Fowlkes, Jason Davidson; Rack, Prof. Philip; Moore, Tom; Magel, Greg; Hartfield, Cheryl

    2012-01-01

    Laser delivery probes using multimode fiber optic delivery and bulk focusing optics have been constructed and used for performing materials processing experiments within scanning electron microscope/focused ion beam instruments. Controlling the current driving a 915-nm semiconductor diode laser module enables continuous or pulsed operation down to sub-microsecond durations, and with spot sizes on the order of 50 {micro}m diameter, achieving irradiances at a sample surface exceeding 1 MW/cm{sup 2}. Localized laser heating has been used to demonstrate laser chemical vapor deposition of Pt, surface melting of silicon, enhanced purity, and resistivity via laser annealing of Au deposits formed by electron beam induced deposition, and in situ secondary electron imaging of laser induced dewetting of Au metal films on SiO{sub x}.

  15. In situ laser processing in a scanning electron microscope

    SciTech Connect

    Roberts, Nicholas A.; Magel, Gregory A.; Hartfield, Cheryl D.; Moore, Thomas M.; Fowlkes, Jason D.; Rack, Philip D.

    2012-07-15

    Laser delivery probes using multimode fiber optic delivery and bulk focusing optics have been constructed and used for performing materials processing experiments within scanning electron microscope/focused ion beam instruments. Controlling the current driving a 915-nm semiconductor diode laser module enables continuous or pulsed operation down to sub-microsecond durations, and with spot sizes on the order of 50 {mu}m diameter, achieving irradiances at a sample surface exceeding 1 MW/cm{sup 2}. Localized laser heating has been used to demonstrate laser chemical vapor deposition of Pt, surface melting of silicon, enhanced purity, and resistivity via laser annealing of Au deposits formed by electron beam induced deposition, and in situ secondary electron imaging of laser induced dewetting of Au metal films on SiO{sub x}.

  16. A scanning acoustic microscope based on picosecond ultrasonics.

    PubMed

    Che, S; Guduru, P R; Nurmikko, A V; Maris, H J

    2015-02-01

    We report on the development of a new type of scanning acoustic microscope. We use a femtosecond light pulse to generate a short sound pulse, and then focus this sound onto the sample by means of a specially designed and microfabricated acoustic lens of radius a few microns. The sound travels to the sample through a thin layer of water. The sound reflected from the sample is collected by the lens and then passes through a monolithically integrated optical resonant cavity. The induced change in the properties of this cavity are measured using a time-delayed probe light pulse. We describe some of the challenges involved in the construction and operation of this high-precision metrology apparatus and present some preliminary results.

  17. High-speed line scanning confocal microscope for biological imaging

    NASA Astrophysics Data System (ADS)

    Jung, Seung-Hwan; Kim, Chang-Keun; Ju, Sung-Bin; Cho, Yong-Jin; Jeong, Hyun-Woo; Kim, Beop-Min

    2007-02-01

    We constructed a high-speed laser line-scanning confocal microscope (LSCM) using He-Ne laser (633 nm), a line CCD camera, and an acousto-optic deflector (AOD). The line scanner consists of an AOD and a cylindrical lens, which create a line focus sweeping over the sample. The line scanner generates two-dimensional confocal images (512× 512 pixel image) up to 191 frames per second with no mechanically-moving parts. This system is configured as an inverted microscope for imaging biological organisms or tissues. Images of various biological samples were obtained including rabbit cornea, onion cells, mouse melanoma tumor cells (B16BL6), and human breast tumor cells (BT-20). The frame rate may be further improved up to over 700 frames per second when the image size is reduced (512×128 pixel image). This system may be useful for analyzing fast phenomena during biological and chemical interactions and for imaging 3D structures rapidly.

  18. Differentiating amino acid residues and side chain orientations in peptides using scanning tunneling microscopy.

    PubMed

    Claridge, Shelley A; Thomas, John C; Silverman, Miles A; Schwartz, Jeffrey J; Yang, Yanlian; Wang, Chen; Weiss, Paul S

    2013-12-11

    Single-molecule measurements of complex biological structures such as proteins are an attractive route for determining structures of the large number of important biomolecules that have proved refractory to analysis through standard techniques such as X-ray crystallography and nuclear magnetic resonance. We use a custom-built low-current scanning tunneling microscope to image peptide structures at the single-molecule scale in a model peptide that forms β sheets, a structural motif common in protein misfolding diseases. We successfully differentiate between histidine and alanine amino acid residues, and further differentiate side chain orientations in individual histidine residues, by correlating features in scanning tunneling microscope images with those in energy-optimized models. Beta sheets containing histidine residues are used as a model system due to the role histidine plays in transition metal binding associated with amyloid oligomerization in Alzheimer's and other diseases. Such measurements are a first step toward analyzing peptide and protein structures at the single-molecule level.

  19. Characterization of thin film semiconductors by scanning probe microscopy and tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Gichuhi, Anthony

    We have used scanning tunneling microscopy, atomic force microscopy, tunneling spectroscopy, resonance Raman spectroscopy and electrochemistry to study the electrosynthesis of II-VI compound semiconductors with special emphasis on ZnS, CdS, and HgS. This dissertation will focus mainly on the electrochemical and scanning probe (STM and AFM) applications to these compounds, in addition to novel materials such as CoSb. We hope to understand the structural, as well optical properties of these materials. Finally, we hope to develop a recipe for the electrosynthesis of high quality semiconductor films. In Chapter 2, we report an electrochemical, scanning probe microscopic and Raman spectroscopic investigation of thin US films grown by electrochemical atomic layer epitaxy (EC-ALE) aimed at understanding the role played by the order of deposition on film quality. In Chapter 3, we report a study of electrosynthesized CdS-HgS heterojunctions using scanning tunneling microscopy (STM), photoluminescence spectroscopy (PL), and electrochemistry. US thin films were grown by electrochemical atomic layer epitaxy onto Au(111) substrates and were terminated with a single HgS monolayer. In Chapter 4, the structure and chemical composition of electrosynthesized ZnS thin films on Au(111) substrates grown by alternating underpotential deposition and oxidative adsorption cycles of S and Zn from solution precursors was studied by scanning tunneling microscopy (STM) and X-ray photoelectron spectroscopy (XPS). In Chapter 5, conditions for the growth of. stable mercury sulfide (HgS) monolayers on Au(111) surfaces using electrochemical atomic layer epitaxy have been investigated. HgS thin films were characterized by X-ray photoelectron spectroscopy (XPS) and scanning tunneling microscopy (STM). Chapter 6: This chapter describes the use of resonance Raman spectroscopy to characterize thin films of the II-VI compound semiconductors electrosynthesized on metal surfaces. We describe how resonance

  20. Principles and Application of Heterodyne Scanning Tunnelling Spectroscopy

    PubMed Central

    Matsuyama, Eiji; Kondo, Takahiro; Oigawa, Haruhiro; Guo, Donghui; Nemoto, Shojiro; Nakamura, Junji

    2014-01-01

    Detection of the extremely weak signals in spectroscopy over an extremely wide frequency region is central to diverse sciences, including materials science, biology, astronomy and chemistry. Here we show a new type of atomic-scale spectroscopy, heterodyne scanning tunnelling spectroscopy (HSTS), which is based on the innovative application of the nonlinear heterodyne-mixing detection at the metal-insulator-metal (MIM) heterojunction of STM tip–vacuum–sample. The principle of HSTS is identical to that of the Atacama Large Millimeter Array (ALMA) space telescope in terms of using heterojunction for detecting extremely weak signals by converting from terahertz region to lower frequency regions. The MIM detector of ALMA, which is composed of niobium–titanium–nitride (NbTiN) tip-insulator-NbTiN, is very similar in shape and size to that of HSTS. We successfully detect a heterodyne beat signal f3 (= |f2 − f1|) and intermodulation distortion via tunnelling current by superimposing two different AC signals, f1 and f2, onto the DC tunnelling current at a highly oriented pyrolytic graphite (HOPG) surface. We then obtain spectra of the localized electronic states of HOPG by using f3. HSTS can be performed with a high resolution and over a wide energy range, including the terahertz range. PMID:25342108

  1. Correlation-steered scanning for scanning probe microscopes to overcome thermal drift for ultra-long time scanning.

    PubMed

    Zhang, Liansheng; Long, Qian; Liu, Yongbin; Zhang, Jie; Feng, Zhihua

    2016-07-01

    The thermal effect is one of the most important factors that influence the accuracy of nanoscale measurement and the surface topography of samples in scanning probe microscopes (SPMs). We propose a method called correlation-steered scanning, which is capable of overcoming three-dimensional thermal drifts in real time for ultra-long time scanned images. The image is scanned band by band with overlapping parts between adjacent bands. The vertical drift can be considered as linear and can thus be eliminated together with the tilt of the sample by applying the flattening method. Each band is artificially divided into several blocks for conveniently calculating lateral drifts on the basis of the overlapping area of adjacent bands through digital image correlation. The calculated lateral drifts are compensated to steer the scanning of the subsequent blocks, thus ensuring that all bands are parallel to one another. Experimental results proved that images scanned by the proposed method exhibited less distortions than those obtained from the traditional raster scanning method. The nanoscale measurement results based on the image obtained by the proposed method also showed high accuracy, with an error of less than 1.5%. By scanning as many bands as needed, the correlation-steered scanning method can obtain a highly precise SPM image of an ultra-large area.

  2. Scanning Photoelectron Microscope (SPEM) with a zone plate generated microprobe

    SciTech Connect

    Ade, H.; Kirz, J.; Hulbert, S.; Johnson, E.; Anderson, E.; Kern, D. . Dept. of Physics; Brookhaven National Lab., Upton, NY; Lawrence Berkeley Lab., CA . Center for X-Ray Optics; International Business Machines Corp., Yorktown Heights, NY . Thomas J. Watson Research Center)

    1989-01-01

    We describe instrumentation of a scanning photoelectron microscope (SPEM), which we are presently developing and commissioning at the X1A beamline of the National Synchrotron Light Source (NSLS). This instrument is designed to use the Soft X-ray Undulator (SXU) at the NSLS as a high brightness source to illuminate a Fresnel zone plate, thus forming a finely focused probe, {le} 0.2{mu}m in size, on the specimen surface. A grating monochromator selects the photon energy in the 400-800 eV range with an energy resolution better than 1 eV. The expected flux in the focus is in the 5 {times} 10{sup 7} {minus} 10{sup 9} photons/s range. A single pass Cylindrical Mirror Analyzer (CMA) is used to record photoemission spectra, or to form an image within a fixed electron energy bandwidth as the specimen is mechanically scanned. As a first test, a 1000 mesh Au grid was successfully imaged with Au 4 f primary photoelectrons, achieving a resolution of about 1{mu}m. 10 refs., 5 figs., 1 tab.

  3. Simulation and Characterization of a Miniaturized Scanning Electron Microscope

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica A.; Jerman, Gregory A.; Medley, Stephanie; Gregory, Don; Abbott, Terry O.; Sampson, Allen R.

    2011-01-01

    A miniaturized Scanning Electron Microscope (mSEM) for in-situ lunar investigations is being developed at NASA Marshall Space Flight Center with colleagues from the University of Alabama in Huntsville (UAH), Advanced Research Systems (ARS), the University of Tennessee in Knoxville (UTK) and Case Western Reserve University (CWRU). This effort focuses on the characterization of individual components of the mSEM and simulation of the complete system. SEMs can provide information on the size, shape, morphology and chemical composition of lunar regolith. Understanding these basic properties will allow us to better estimate the challenges associated with In-Situ Resource Utilization and to improve our basic science knowledge of the lunar surface (either precluding the need for sample return or allowing differentiation of unique samples to be returned to Earth.) The main components of the mSEM prototype includes: a cold field emission electron gun (CFEG), focusing lens, deflection/scanning system and backscatter electron detector. Of these, the electron gun development is of particular importance as it dictates much of the design of the remaining components. A CFEG was chosen for use with the lunar mSEM as its emission does not depend on heating of the tungsten emitter (lower power), it offers a long operation lifetime, is orders of magnitude brighter than tungsten hairpin guns, has a small source size and exhibits low beam energy spread.

  4. Miniaturized Environmental Scanning Electron Microscope for In Situ Planetary Studies

    NASA Technical Reports Server (NTRS)

    Gaskin, Jessica; Abbott, Terry; Medley, Stephanie; Gregory, Don; Thaisen, Kevin; Taylor , Lawrence; Ramsey, Brian; Jerman, Gregory; Sampson, Allen; Harvey, Ralph

    2010-01-01

    The exploration of remote planetary surfaces calls for the advancement of low power, highly-miniaturized instrumentation. Instruments of this nature that are capable of multiple types of analyses will prove to be particularly useful as we prepare for human return to the moon, and as we continue to explore increasingly remote locations in our Solar System. To this end, our group has been developing a miniaturized Environmental-Scanning Electron Microscope (mESEM) capable of remote investigations of mineralogical samples through in-situ topographical and chemical analysis on a fine scale. The functioning of an SEM is well known: an electron beam is focused to nanometer-scale onto a given sample where resulting emissions such as backscattered and secondary electrons, X-rays, and visible light are registered. Raster scanning the primary electron beam across the sample then gives a fine-scale image of the surface topography (texture), crystalline structure and orientation, with accompanying elemental composition. The flexibility in the types of measurements the mESEM is capable of, makes it ideally suited for a variety of applications. The mESEM is appropriate for use on multiple planetary surfaces, and for a variety of mission goals (from science to non-destructive analysis to ISRU). We will identify potential applications and range of potential uses related to planetary exploration. Over the past few of years we have initiated fabrication and testing of a proof-of-concept assembly, consisting of a cold-field-emission electron gun and custom high-voltage power supply, electrostatic electron-beam focusing column, and scanning-imaging electronics plus backscatter detector. Current project status will be discussed. This effort is funded through the NASA Research Opportunities in Space and Earth Sciences - Planetary Instrument Definition and Development Program.

  5. Scanning tunneling microscopy of the atomically smooth (001) surface of vanadium pentoxide V2O5 crystals

    NASA Astrophysics Data System (ADS)

    Muslimov, A. E.; Butashin, A. V.; Kanevsky, V. M.

    2017-01-01

    The (001) cleavage surface of vanadium pentoxide (V2O5) crystal has been studied by scanning tunneling spectroscopy (STM). It is shown that the surface is not reconstructed; the STM image allows geometric lattice parameters to be determined with high accuracy. The nanostructure formed on the (001) cleavage surface of crystal consists of atomically smooth steps with a height multiple of unit-cell parameter c = 4.37 Å. The V2O5 crystal cleavages can be used as references in calibration of a scanning tunneling microscope under atmospheric conditions both along the ( x, y) surface and normally to the sample surface (along the z axis). It is found that the terrace surface is not perfectly atomically smooth; its roughness is estimated to be 0.5 Å. This circumstance may introduce an additional error into the microscope calibration along the z coordinate.

  6. Method and apparatus for differential spectroscopic atomic-imaging using scanning tunneling microscopy

    DOEpatents

    Kazmerski, Lawrence L.

    1990-01-01

    A Method and apparatus for differential spectroscopic atomic-imaging is disclosed for spatial resolution and imaging for display not only individual atoms on a sample surface, but also bonding and the specific atomic species in such bond. The apparatus includes a scanning tunneling microscope (STM) that is modified to include photon biasing, preferably a tuneable laser, modulating electronic surface biasing for the sample, and temperature biasing, preferably a vibration-free refrigerated sample mounting stage. Computer control and data processing and visual display components are also included. The method includes modulating the electronic bias voltage with and without selected photon wavelengths and frequency biasing under a stabilizing (usually cold) bias temperature to detect bonding and specific atomic species in the bonds as the STM rasters the sample. This data is processed along with atomic spatial topography data obtained from the STM raster scan to create a real-time visual image of the atoms on the sample surface.

  7. A Tunneling Microscope for Operation in Air or Fluids.

    DTIC Science & Technology

    1985-10-01

    between IBM Zurich designs and squeezable tunnel junctions has been operated in air, oil, and liquid nitro - gen. Key design goals were 1) maximum...from 10 Hz to 20kHz. The inner shield (a coffee can) provides electrical screening and shuts out light. Not shown is approximately 150kg of lead that was...image individual atoms in a close-packed, unreconstructed layer is obtainable with submersion in liquid nitro - o gen. This implies lateral resolution

  8. Semiautomatic classification of cementitious materials using scanning electron microscope images

    NASA Astrophysics Data System (ADS)

    Drumetz, Lucas; Mura, Mauro Dalla; Meulenyzer, Samuel; Lombard, Sébastien; Chanussot, Jocelyn

    2015-11-01

    Segmentation and classification are prolific research topics in the image processing community. These topics have been increasingly used in the context of analysis of cementitious materials on images acquired with a scanning electron microscope. Indeed, there is a need to be able to detect and to quantify the materials present in a cement paste in order to follow the chemical reactions occurring in the material even days after the solidification. We propose a new approach for segmentation and classification of cementitious materials based on the denoising of the data with a block-matching three-dimensional (3-D) algorithm, binary partition tree (BPT) segmentation, support vector machines (SVM) classification, and interactivity with the user. The BPT provides a hierarchical representation of the spatial regions of the data, allowing a segmentation to be selected among the admissible partitions of the image. SVMs are used to obtain a classification map of the image. This approach combines state-of-the-art image processing tools with user interactivity to allow a better segmentation to be performed, or to help the classifier discriminate the classes better. We show that the proposed approach outperforms a previous method when applied to synthetic data and several real datasets coming from cement samples, both qualitatively with visual examination and quantitatively with the comparison of experimental results with theoretical ones.

  9. Smart flexible microrobots for scanning electron microscope (SEM) applications

    NASA Astrophysics Data System (ADS)

    Schmoeckel, Ferdinand; Fatikow, Sergej

    2000-06-01

    In the scanning electron microscope (SEM), specially designed microrobots can act as a flexible assembly facility for hybrid microsystems, as probing devices for in-situ tests on IC structures or just as a helpful teleoperated tool for the SEM operator when examining samples. Several flexible microrobots of this kind have been developed and tested. Driven by piezoactuators, these few cubic centimeters small mobile robots perform manipulations with a precision of up to 10 nm and transport the gripped objects at speeds of up to 3 cm/s. In accuracy, flexibility and price they are superior to conventional precision robots. A new SEM-suited microrobot prototype is described in this paper. The SEM's vacuum chamber has been equipped with various elements like flanges and CCD cameras to enable the robot to operate. In order to use the SEM image for the automatic real-time control of the robots, the SEM's electron beam is actively controlled by a PC. The latter submits the images to the robots' control computer system. For obtaining three-dimensional information in real time, especially for the closed-loop control of a robot endeffector, e.g. microgripper, a triangulation method with the luminescent spot of the SEM's electron beam is being investigated.

  10. A scanning acoustic microscope discriminates cancer cells in fluid

    NASA Astrophysics Data System (ADS)

    Miura, Katsutoshi; Yamamoto, Seiji

    2015-10-01

    Scanning acoustic microscopy (SAM) discriminates lesions in sections by assessing the speed of sound (SOS) or attenuation of sound (AOS) through tissues within a few minutes without staining; however, its clinical use in cytological diagnosis is unknown. We applied a thin layer preparation method to observe benign and malignant effusions using SAM. Although SAM is inferior in detecting nuclear features than light microscopy, it can differentiate malignant from benign cells using the higher SOS and AOS values and large irregular cell clusters that are typical features of carcinomas. Moreover, each single malignant cell exhibits characteristic cytoplasmic features such as a large size, irregular borders and secretory or cytoskeletal content. By adjusting the observation range, malignant cells are differentiated from benign cells easily using SAM. Subtle changes in the functional and structural heterogeneity of tumour cells were pursuable with a different digital data of SAM. SAM can be a useful tool for screening malignant cells in effusions before light microscopic observation. Higher AOS values in malignant cells compared with those of benign cells support the feasibility of a novel sonodynamic therapy for malignant effusions.

  11. Scanning electron microscopic and profilometric study of different sharpening stones.

    PubMed

    Andrade Acevedo, Roberto Antonio; Cardozo, Ana Karina Veloso; Sampaio, José Eduardo César

    2006-01-01

    Scaling and root planing contribute to the recovery of periodontal health. All periodontal instruments loose their fine cutting angle after use. To maintain this angle, correct sharpening is required using specifically designed stones. The characteristics of sharpening stones can be compared to the blade of the instruments and also transported to root surface during instrumentation. Root smoothness is related to the quality of the blade. Therefore, the purpose of this study was to evaluate the characteristics of 9 sharpening stones by scanning electron microscopic and profilometric analyses. Ceramic and Neumar stones were very fine and both may be recommended to maintain the sharpness of the instruments. Arkansas, Thompson and CE stones presented greater roughness with very regular and round particles, and are suitable for maintenance of the cutting angle. In addition, these stones may be indicated for the routine sharpening of the instruments that are partly dull. Oxide Aluminum, Carborundum and JON stones were the coarsest with large irregular particles and may be indicated for initial sharpening of totally dull instruments with completion of sharpening with finer stones.

  12. A scanning SQUID microscope with 200 MHz bandwidth

    NASA Astrophysics Data System (ADS)

    Talanov, Vladimir V.; Lettsome, Nesco M., Jr.; Borzenets, Valery; Gagliolo, Nicolas; Cawthorne, Alfred B.; Orozco, Antonio

    2014-04-01

    We developed a scanning DC SQUID microscope with novel readout electronics capable of wideband sensing of RF magnetic fields from 50 to 200 MHz and simultaneously providing closed-loop response at kHz frequencies. To overcome the 20 MHz bandwidth limitation of traditional closed-loop SQUIDs, a flux-modulated closed-loop simultaneously locks the SQUID quasi-static flux and flux-biases the SQUID for amplification of the RF flux up to Φ0/4 in amplitude. Demodulating the SQUID voltage with a double lock-in technique yields a signal representative of both the amplitude and phase of the RF flux. This provides 80 dB of a linear dynamic range with a flux noise density of 4 μΦ0 Hz-1/2 at 200 MHz for a Y Ba2Cu3O7 bi-crystal SQUID at 77 K. We describe the electronics’ performance and present images for RF magnetic field of the travelling wave in a coplanar waveguide, the standing wave in an open-circuited microstrip, and a surface mounted device antenna.

  13. MicroDiffraction in the Scanning Electron Microscope (SEM)

    SciTech Connect

    Goehner, R.P.; Michael, J.R.; Schlienger, M.E.

    1997-12-31

    The identification of crystallographic phases in the scanning electron microscope (SEM) has been limited by the lack of a simple way to obtain electron diffraction data of an unknown while observing the micro structure of the specimen. With the development of Charge Coupled Device (CCD) based detectors, backscattered electron Kikuchi patterns (BEKP), alternately referred to as electron backscattered diffraction patterns (EBSP), can be easily collected. Previously, BEKP has been limited to crystallographic orientation studies due to the poor pattern quality collected with video rate detector systems. With CCD detectors, a typical BEKP can now be acquired from a micron or sub-micron-sized crystal using an exposure time of 1-10 seconds with an accelerating voltage of 10-40 kV and a beam current as low as 0.1 nA. Crystallographic phase analysis using BEKP is unique in that the properly equipped SEM permits high magnification images, BEKP`s, and elemental information to be collected from bulk specimens. BEKP in the SEM has numerous advantages over other electron microscopy crystallographic techniques. The large angular view ( 70 degrees) provided by BEKP and the lack of difficult specimen preparation are distinct advantages of the technique. No sample preparation beyond what is commonly used for SEM specimens is required for BEKP.

  14. Organic Multilayer Films Studied by Scanning Tunneling Microscopy.

    PubMed

    He, Yang; Kröger, Jörg; Wang, Yongfeng

    2017-03-03

    This Minireview focuses exclusively on work with scanning tunneling microscopy to study the self-assembled multilayer films (SAMTs) of organic molecules. The π-conjugated organic molecules form different structures within different monolayers on various substrates. The interplay between molecule-substrate and intermolecular interactions plays a key role in determining the stacking mode of organic multilayer films. Different substrates strongly influence the organic-film growth and electronic properties of the organic molecules. Geometric and electronic structures of SAMTs are important factors that may determine device performance. In addition to the inorganic interface, this Minireview addresses the organic-organic interface. Homo- and hetero-SAMTs of organic molecules are also considered. The subtle interplay between structural and electronic characteristics, on one hand, and functionality and reactivity, on the other hand, are highlighted.

  15. Microbial Nanowire Electronic Structure Probed by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Veazey, Joshua P.; Lampa-Pastirk, Sanela; Reguera, Gemma; Tessmer, Stuart H.

    2010-03-01

    Complex molecules produced by living organisms provide laboratories for interesting physical properties. The study of such interesting physics, likewise, gives new insight into intriguing biological processes. We have studied the pilus nanowires expressed by the bacterium, Geobacter sulfurreducens, using high resolution scanning tunneling microscopy (STM). G. sulfurreducens is a metal reducing bacterium that has evolved electrically conductive pili to efficiently transfer electrons across large distances.footnotetextG. Reguera, K.D. McCarthy, T. Mehta, J.S. Nicoll, M.T. Tuominen, and D.R. Lovley, Nature 435, 1098 (2005) Here we employ the electronic sensitivity of STM to resolve the molecular substructure and the local electronic density of states (LDOS) along the nanowire, in an effort to elucidate the mechanism of conduction. We observe LDOS dependent upon the location of the tip above the nanowire.

  16. Scanning tunneling microscopy of graphene on Ru(0001)

    NASA Astrophysics Data System (ADS)

    Marchini, S.; Günther, S.; Wintterlin, J.

    2007-08-01

    After prolonged annealing of a Ru(0001) sample in ultrahigh vacuum a superstructure with a periodicity of ˜30Å was observed by scanning tunneling microscopy (STM). Using x-ray photoelectron spectroscopy it was found that the surface is covered by graphitic carbon. Auger electron spectroscopy shows that between 1000 and 1400K carbon segregates to the surface. STM images recorded after annealing to increasing temperatures display islands of the superstructure, until, after annealing to T⩾1400K , it covers the entire surface. The morphology of the superstructure shows that it consists of a single graphene layer. Atomically resolved STM images and low-energy electron diffraction reveal an (11×11) structure or incommensurate structure close to this periodicity superimposed by 12×12 graphene cells. The lattice mismatch causes a moiré pattern. Unlike the common orientational disorder of adsorbed graphene, the graphene layer on Ru(0001) shows a single phase and very good rotational alignment. Misorientations near defects in the overlayer only amount to ˜1° , and the periodicity of ˜30Å is unaffected. In contrast to bulk graphite both carbon atoms in the graphene unit cell were resolved by STM, with varying contrast depending on the position above the Ru atoms. The filled and empty state images of the moiré structure differ massively, and electronic states at -0.4 and +0.2V were detected by scanning tunneling spectroscopy. The data indicate a significantly stronger chemical interaction between graphene and the metal surface than between neighboring layers in bulk graphite. The uniformity of the structure and its stability at high temperatures and in air suggest an application as template for nanostructures.

  17. Laser-induced scanning tunneling microscopy: Linear excitation of the junction plasmon.

    PubMed

    Lee, Joonhee; Perdue, Shawn M; Whitmore, Desiré; Apkarian, V Ara

    2010-09-14

    We introduce the cross-polarized double-beat method for localized excitation of the junction plasmon of a scanning tunneling microscope with femtosecond laser pulses. We use two pulse trains derived from a Ti:sapphire laser operating at a repetition frequency of f(s)=76 MHz, with a relative shift between their carrier frequencies ω(a)/2π=f(s)+f(b) controlled with an acousto-optic modulator. The trains are cross-polarized and collinearly focused on the junction, ensuring constant radiation flux. The anisotropic susceptibility of the junction plasmon mixes the fields, which modulate the tunneling current at f(b) (the difference between carrier beat and repetition frequency) at base-band frequencies that can be used for direct detection of the tunneling current. The interferometric cross-correlation of the pulses and the polarization dependence of the mixing identify the coupling to the radiation to be through the coherent z-displacement of the tip plasmon. Single Ag atoms are used to demonstrate microscopy under irradiation. In the linear coupling regime, the laser-induced displacement of the plasmon is operationally indistinguishable from the mechanical displacement of the junction gap.

  18. Bistability in Scanning Tunneling Spectroscopy of Ga-terminated Si(111)

    NASA Astrophysics Data System (ADS)

    Chen, Dongmin; Altfeder, Igor

    2000-03-01

    The bistable transport characteristics have been the basis of modern power and high speed switching devices. All these devices share a common and essential double barrier structure. Here we report on a surprising observation of the bistable tunneling characteristics in an apparent single barrier tunnel junction consisted of a Ga-terminated Si(111) surface and a W-tip of a scanning tunneling microscope (STM) operating at 77K. Under a negative tip bias condition, a switching from an initially high-impedance, low-current OFF state to a low-impedance, high-current ON state occurs at a bias higher than that for the subsequent reversal transition, giving rise to a large hysteresis loops. The turn-on bias varies from 3.1V to 4.0V,showing a large inverse dependence on the tip-sample distances, indicating strong field effect. On contrary, the turn-off bias is essentially pined at 2.7V, suggesting the existence of a conductance threshold. This opens the possioblity to engineer a new type of swithching device using only single layer atomic dopping in place of a more complex double barrier structure.

  19. Improved specimen coating technique for scanning electron microscope observation of decomposer microorganisms.

    PubMed

    Draggan, S

    1976-02-01

    Sputter coating of leaf litter microbe samples provides scanning electron microscope images with greater information content than either vacuum evaporation of thin metal coatings or tissue conductance.

  20. Visualizing bone porosities using a tabletop scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Krishnamoorthy, D.; DaPonte, J.; Broadbridge, C. C.; Daniel, D.; Alter, L.

    2010-04-01

    Pores are naturally occurring entities in bone. Changes in pore size and number are often associated with diseases such as Osteoporosis and even microgravity during spaceflight. Studying bone perforations may yield great insight into bone's material properties, including bone density and may contribute to identifying therapies to halt or potentially reverse bone loss. Current technologies used in this field include nuclear magnetic resonance, micro-computed tomography and the field emission scanning electron microscope (FE-SEM) 2, 5. However, limitations in each method limit further advancement. The objective of this study was to assess the effectiveness of using a new generation of analytical instruments, the TM-1000 tabletop, SEM with back-scatter electron (BSE) detector, to analyze cortical bone porosities. Hind limb unloaded and age-based controlled mouse femurs were extracted and tested in vitro for changes in pores on the periosteal surface. An important advantage of using the tabletop is the simplified sample preparation that excludes extra coatings, dehydration and fixation steps that are otherwise required for conventional SEM. For quantitative data, pores were treated as particles in order to use an analyze particles feature in the NIH ImageJ software. Several image-processing techniques for background smoothing, thresholding and filtering were employed to produce a binary image suitable for particle analysis. It was hypothesized that the unloaded bones would show an increase in pore area, as the lack of mechanical loading would affect bone-remodeling processes taking place in and around pores. Preliminary results suggest only a slight different in frequency but not in size of pores between unloaded and control femurs.

  1. Structural changes in a Schiff base molecular assembly initiated by scanning tunneling microscopy tip.

    PubMed

    Tomak, A; Bacaksiz, C; Mendirek, G; Sahin, H; Hur, D; Görgün, K; Senger, R T; Birer, Ö; Peeters, F M; Zareie, H M

    2016-08-19

    We report the controlled self-organization and switching of newly designed Schiff base (E)-4-((4-(phenylethynyl) benzylidene) amino) benzenethiol (EPBB) molecules on a Au (111) surface at room temperature. Scanning tunneling microscopy and spectroscopy (STM/STS) were used to image and analyze the conformational changes of the EPBB molecules. The conformational change of the molecules was induced by using the STM tip while increasing the tunneling current. The switching of a domain or island of molecules was shown to be induced by the STM tip during scanning. Unambiguous fingerprints of the switching mechanism were observed via STM/STS measurements. Surface-enhanced Raman scattering was employed, to control and identify quantitatively the switching mechanism of molecules in a monolayer. Density functional theory calculations were also performed in order to understand the microscopic details of the switching mechanism. These calculations revealed that the molecular switching behavior stemmed from the strong interaction of the EPBB molecules with the STM tip. Our approach to controlling intermolecular mechanics provides a path towards the bottom-up assembly of more sophisticated molecular machines.

  2. Interfacial scanning tunneling spectroscopy (STS) of chalcogenide/metal hybrid nanostructure

    NASA Astrophysics Data System (ADS)

    Saad, Mahmoud M.; Abdallah, Tamer; Easawi, Khalid; Negm, Sohair; Talaat, Hassan

    2015-05-01

    The electronic structure at the interface of chalcogenide/metal hybrid nanostructure (CdSe-Au tipped) had been studied by UHV scanning tunneling spectroscopy (STS) technique at room temperature. This nanostructure was synthesized by a phase transfer chemical method. The optical absorption of this hybrid nanostructure was recorded, and the application of the effective mass approximation (EMA) model gave dimensions that were confirmed by the direct measurements using the scanning tunneling microscopy (STM) as well as the high-resolution transmission electron microscope (HRTEM). The energy band gap obtained by STS agrees with the values obtained from the optical absorption. Moreover, the STS at the interface of CdSe-Au tipped hybrid nanostructure between CdSe of size about 4.1 ± 0.19 nm and Au tip of size about 3.5 ± 0.29 nm shows a band bending about 0.18 ± 0.03 eV in CdSe down in the direction of the interface. Such a result gives a direct observation of the electron accumulation at the interface of CdSe-Au tipped hybrid nanostructure, consistent with its energy band diagram. The presence of the electron accumulation at the interface of chalcogenides with metals has an important implication for hybrid nanoelectronic devices and the newly developed plasmon/chalcogenide photovoltaic solar energy conversion.

  3. Scanning Tunneling Spectroscopy on InAs-GaSb Esaki Diode Nanowire Devices during Operation.

    PubMed

    Persson, Olof; Webb, James L; Dick, Kimberly A; Thelander, Claes; Mikkelsen, Anders; Timm, Rainer

    2015-06-10

    Using a scanning tunneling and atomic force microscope combined with in-vacuum atomic hydrogen cleaning we demonstrate stable scanning tunneling spectroscopy (STS) with nanoscale resolution on electrically active nanowire devices in the common lateral configuration. We use this method to map out the surface density of states on both the GaSb and InAs segments of GaSb-InAs Esaki diodes as well as the transition region between the two segments. Generally the surface shows small bandgaps centered around the Fermi level, which is attributed to a thin multielement surface layer, except in the diode transition region where we observe a sudden broadening of the bandgap. By applying a bias to the nanowire we find that the STS spectra shift according to the local nanoscale potential drop inside the wire. Importantly, this shows that we have a nanoscale probe with which we can infer both surface electronic structure and the local potential inside the nanowire and we can connect this information directly to the performance of the imaged device.

  4. Scanning Tunneling Spectroscopy on InAs–GaSb Esaki Diode Nanowire Devices during Operation

    PubMed Central

    2015-01-01

    Using a scanning tunneling and atomic force microscope combined with in-vacuum atomic hydrogen cleaning we demonstrate stable scanning tunneling spectroscopy (STS) with nanoscale resolution on electrically active nanowire devices in the common lateral configuration. We use this method to map out the surface density of states on both the GaSb and InAs segments of GaSb–InAs Esaki diodes as well as the transition region between the two segments. Generally the surface shows small bandgaps centered around the Fermi level, which is attributed to a thin multielement surface layer, except in the diode transition region where we observe a sudden broadening of the bandgap. By applying a bias to the nanowire we find that the STS spectra shift according to the local nanoscale potential drop inside the wire. Importantly, this shows that we have a nanoscale probe with which we can infer both surface electronic structure and the local potential inside the nanowire and we can connect this information directly to the performance of the imaged device. PMID:25927249

  5. Direct control and characterization of a Schottky barrier by scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Bell, L. D.; Kaiser, W. J.; Hecht, M. H.; Grunthaner, F. J.

    1988-01-01

    Scanning tunneling microscopy (STM) methods are used to directly control the barrier height of a metal tunnel tip-semiconductor tunnel junction. Barrier behavior is measured by tunnel current-voltage spectroscopy and compared to theory. A unique surface preparation method is used to prepare a low surface state density Si surface. Control of band bending with this method enables STM investigation of semiconductor subsurface properties.

  6. 3D scanning of internal structure in gel engineering materials with visual scanning microscopic light scattering

    NASA Astrophysics Data System (ADS)

    Watanabe, Yosuke; Gong, Jing; Masato, Makino; Kabir, M. Hasnat; Furukawa, Hidemitsu

    2014-04-01

    The 3D printing technology, causing much attention from the beginning of 2013, will be possibly an alternative method to fabricate the biological soft tissues. Recently our group of Yamagata University has developed the world-first 3D Gel Printer to fabricate the complicated gel-materials with high-strength and biocompatibility. However, there are no 3D scanners that collect the data from the internal structure of complicated gel objects such as eye lens. It means that a new system for scanning the internal structure is needed now. In this study, firstly, we have tried to investigate the gel network of synthetic and biological gel with scanning microscopic light scattering (SMILS). We calculated the Young's modulus of synthetic gels with the SMILS and with the tensile test, and precisely compared the results between them. The temperature dependences of the inside structure and the transparency are observed in the pig crystalline lens. The quantitative analysis indicates the importance of the internal structure of real object. Secondary, we show the new system named Gel-scanner that can provide the 2-dimentional data of the internal structure. From examining our findings, the scanning of internal structure will enable us to expect physical properties of the real object. We convince that the gelscanner will play major role in the various fields.

  7. Charge ordering in stoichiometric FeTe: Scanning tunneling microscopy and spectroscopy

    SciTech Connect

    Li, Wei; Yin, Wei -Guo; Wang, Lili; He, Ke; Ma, Xucun; Xue, Qi -Kun; Chen, Xi

    2016-01-04

    In this study, we use scanning tunneling microscopy and spectroscopy to reveal a unique stripy charge order in a parent phase of iron-based superconductors in stoichiometric FeTe epitaxy films. The charge order has unusually the same—usually half—period as the spin order. We also found highly anisotropic electron band dispersions being large and little along the ferromagnetic (crystallographic b) and antiferromagnetic (a) directions, respectively. Our data suggest that the microscopic mechanism is likely of the Stoner type driven by interatomic Coulomb repulsion Vij, and that Vij and charge fluctuations, so far much neglected, are important to the understanding of iron-based superconductors.

  8. Observation of small metal clusters on graphite surface with scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Shen, Jian; Zhu, Changxin; Ma, Zili; Pang, Shijin; Xue, Zengquan

    The motivation for studying the dynamic behavior and morphology of small metal clusters on solid single crystal surface is the desire to understand the physical mechanisms evolving in the initial stages of thin-film growth. In the experiments we have used a scanning tunneling microscope to study the static morphology of small Pt and Ni clusters supported on clean graphite surfaces, as well as the dynamic behaviors of small Pt clusters in an ultrahigh vacuum chamber. The metal deposition was fulfilled by controllable evaporation from ultra-pure superfine metal wires at room temperature in UHV. The STM images of small Pt and Ni clusters on graphite substrates with atomic resolution, as well as a series of STM images reveal some transformation processes of small metal clusters on the solid crystal surfaces, which provide us a better understanding on the procedure of atomic diffusion of metal clusters. All the STM images have been performed at room temperature.

  9. Simultaneous scanning tunneling microscopy and stress measurements to elucidate the origins of surface forces.

    PubMed

    Narushima, Tetsuya; Kinahan, Niall T; Boland, John J

    2007-05-01

    We have developed a new combined measurement system to investigate the underlying origins of forces on solid state surfaces from the viewpoint of atomic surface morphology. This system consists of two main parts: the measurements of force based on displacements and detailed atomic resolution observations of the surface morphology. The former involves a large sample cantilever and a capacitive detection method that provide sufficient resolution to detect changes of a few meV/atom or pN/atom at surfaces. For the latter, a scanning tunneling microscope was incorporated to observe structural changes occurring on the surface of the cantilever sample. Although this combined observation is not trivial, it was accomplished by carefully designing sample dimensions while suppressing the self-oscillation of the cantilever. To demonstrate the performance of this system a preliminary study of the room temperature adsorption of Br(2) on the clean Si(111)-7x7 surface is presented.

  10. Atomic Structure and Charge Density Waves of Blue Bronze by Variable Temperature Scanning Tunneling Microscopy

    SciTech Connect

    Nikiforov,M.; Isakovic, A.; Bonnell, D.

    2007-01-01

    Blue bronze (K{sub 0.3}MoO{sub 3}) has been the focus of a number of scattering, transport, scanning tunneling microscopy (STM), and theoretical studies that have provided insight into the relation between atomic structure and charge-density wave (CDW) formation. However, the full extent of a relation of the CDWs to the atomic lattice and the microscopic origin of CDW pinning are still not completely resolved. In this study STM is used to distinguish the atomic structure and CDWs at the (20{bar 1}) surface. Within the STM's spatial resolution, the CDWs are incommensurate with the lattice at midrange temperatures and approach commensurability at low temperatures. Incommensurate CDWs are present on the surface and the degree of the incommensurability between blue bronze lattice and CDW lattice agree well with those determined from bulk scattering techniques.

  11. Intermode Coupling Drives the Irreversible Tautomerization in Porphycene on Copper(111) Induced by Scanning Tunnelling Microscopy.

    PubMed

    Novko, Dino; Blanco-Rey, María; Tremblay, Jean Christophe

    2017-03-02

    In this contribution, we develop a nonadiabatic theory that explains, from first-principles, the recently reported irreversible trans → cis tautomerization of porphycene on Cu(111) induced by a scanning tunnelling microscope at finite bias. The inelastic contribution to the STM current is found to excite a large number of skeletal vibrational modes of the molecule, thereby inducing a deformation of the potential energy landscape along the hydrogen transfer coordinate. Above a threshold bias, the stability of the tautomers is reversed, which indirectly drives the reaction via intermode coupling. The proposed potential deformation term accounts effectively for the excitation of all internal vibrational modes without increasing the dimensionality of the problem. The model yields information about reaction rates, explains the reaction irreversibility at low temperatures, and accounts for the presence of resonant processes.

  12. Electromagnetic model for near-field microwave microscope with atomic resolution: Determination of tunnel junction impedance

    SciTech Connect

    Reznik, Alexander N.

    2014-08-25

    An electrodynamic model is proposed for the tunneling microwave microscope with subnanometer space resolution as developed by Lee et al. [Appl. Phys. Lett. 97, 183111 (2010)]. Tip-sample impedance Z{sub a} was introduced and studied in the tunneling and non-tunneling regimes. At tunneling breakdown, the microwave current between probe and sample flows along two parallel channels characterized by impedances Z{sub p} and Z{sub t} that add up to form overall impedance Z{sub a}. Quantity Z{sub p} is the capacitive impedance determined by the near field of the probe and Z{sub t} is the impedance of the tunnel junction. By taking into account the distance dependences of effective tip radius r{sub 0}(z) and tunnel resistance R{sub t}(z) = Re[Z{sub t}(z)], we were able to explain the experimentally observed dependences of resonance frequency f{sub r}(z) and quality factor Q{sub L}(z) of the microscope. The obtained microwave resistance R{sub t}(z) and direct current tunnel resistance R{sub t}{sup dc}(z) exhibit qualitatively similar behavior, although being largely different in both magnitude and the characteristic scale of height dependence. Interpretation of the microwave images of the atomic structure of test samples proved possible by taking into account the inductive component of tunnel impedance ImZ{sub t} = ωL{sub t}. Relation ωL{sub t}/R{sub t} ≈ 0.235 was obtained.

  13. Scanning tunneling microscopy/spectroscopy on perovskite oxide thin films deposited in situ.

    PubMed

    Hitosugi, Taro; Shimizu, Ryota; Ohsawa, Takeo; Iwaya, Katsuya

    2014-10-01

    Complex oxide surfaces and interfaces, consisting of two or more cations and oxygen anions, have attracted a great deal of attention because their properties are crucial factors in the performance of catalysts, fuel cells, and Li-ion batteries. However, atomic-scale investigations of these oxide surfaces have been hindered because of the difficulties in surface preparation. Here, we demonstrate atomic-scale surface studies of complex perovskite oxides and the initial growth processes in oxide epitaxial films deposited on (✓13 × ✓13)-R33.7° reconstructed SrTiO3 (001) substrates using a scanning tunneling microscope integrated with a pulsed laser deposition system. The atomically ordered, reconstructed SrTiO3 (001) surface is stable under the typical conditions necessary for the growth of oxide thin films, and hence is considered suitable for the study of the initial growth processes in oxide films. The atomic-scale microscopic/spectroscopic characterizations performed here shed light on the microscopic origin of electronic properties observed in complex oxides and their heterostructures.

  14. Using the scanning electron microscope on the production line to assure quality semiconductors

    NASA Technical Reports Server (NTRS)

    Adolphsen, J. W.; Anstead, R. J.

    1972-01-01

    The use of the scanning electron microscope to detect metallization defects introduced during batch processing of semiconductor devices is discussed. A method of determining metallization integrity was developed which culminates in a procurement specification using the scanning microscope on the production line as a quality control tool. Batch process control of the metallization operation is monitored early in the manufacturing cycle.

  15. A method of dynamic chromatic aberration correction in low-voltage scanning electron microscopes.

    PubMed

    Khursheed, Anjam

    2005-07-01

    A time-of-flight concept that dynamically corrects for chromatic aberration effects in scanning electron microscopes (SEMs) is presented. The method is predicted to reduce the microscope's chromatic aberration by an order of magnitude. The scheme should significantly improve the spatial resolution of low-voltage scanning electron microscopes (LVSEMs). The dynamic means of correcting for chromatic aberration also allows for the possibility of obtaining high image resolution from electron guns that have relatively large energy spreads.

  16. Metal-silicene interaction studied by scanning tunneling microscopy.

    PubMed

    Li, Zhi; Feng, Haifeng; Zhuang, Jincheng; Pu, Na; Wang, Li; Xu, Xun; Hao, Weichang; Du, Yi

    2016-01-27

    Ag atoms have been deposited on 3  ×  3 silicene and  √3  ×  √3 silicene films by molecular beam epitaxy method in ultrahigh vacuum. Using scanning tunneling microscopy and Raman spectroscopy, we found that Ag atoms do not form chemical bonds with both 3  ×  3 silicene and  √3  ×  √3 silicene films, which is due to the chemically inert surface of silicene. On 3  ×  3 silicene films, Ag atoms mostly form into stable flat-top Ag islands. In contrast, Ag atoms form nanoclusters and glide on silicene films, suggesting a more inert nature. Raman spectroscopy suggests that there is more sp (2) hybridization in  √3  ×  √3 than in  √7  ×  √7/3  ×  3 silicene films.

  17. Metal-silicene interaction studied by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Li, Zhi; Feng, Haifeng; Zhuang, Jincheng; Pu, Na; Wang, Li; Xu, Xun; Hao, Weichang; Du, Yi

    2016-01-01

    Ag atoms have been deposited on 3  ×  3 silicene and  √3  ×  √3 silicene films by molecular beam epitaxy method in ultrahigh vacuum. Using scanning tunneling microscopy and Raman spectroscopy, we found that Ag atoms do not form chemical bonds with both 3  ×  3 silicene and  √3  ×  √3 silicene films, which is due to the chemically inert surface of silicene. On 3  ×  3 silicene films, Ag atoms mostly form into stable flat-top Ag islands. In contrast, Ag atoms form nanoclusters and glide on silicene films, suggesting a more inert nature. Raman spectroscopy suggests that there is more sp 2 hybridization in  √3  ×  √3 than in  √7  ×  √7/3  ×  3 silicene films.

  18. Active nanocharacterization of nanofunctional materials by scanning tunneling microscopy.

    PubMed

    Fujita, Daisuke; Sagisaka, Keisuke

    2008-01-01

    Recent developments in the application of scanning tunneling microscopy (STM) to nanofabrication and nanocharacterization are reviewed. The main focus of this paper is to outline techniques for depositing and manipulating nanometer-scale structures using STM tips. Firstly, the transfer of STM tip material through the application of voltage pulses is introduced. The highly reproducible fabrication of metallic silver nanodots and nanowires is discussed. The mechanism is thought to be spontaneous point-contact formation caused by field-enhanced diffusion to the apex of the tip. Transfer through the application of z-direction pulses is also introduced. Sub-nanometer displacement pulses along the z-direction form point contacts that can be used for reproducible nanodot deposition. Next, the discovery of the STM structural manipulation of surface phases is discussed. It has been demonstrated that superstructures on Si(001) surfaces can be reverse-manipulated by controlling the injected carriers. Finally, the fabrication of an atomic-scale one-dimensional quantum confinement system by single-atom deposition using a controlled point contact is presented. Because of its combined nanofabrication and nanocharacterization capabilities, STM is a powerful tool for exploring the nanotechnology and nanoscience fields.

  19. Active nanocharacterization of nanofunctional materials by scanning tunneling microscopy

    PubMed Central

    Fujita, Daisuke; Sagisaka, Keisuke

    2008-01-01

    Recent developments in the application of scanning tunneling microscopy (STM) to nanofabrication and nanocharacterization are reviewed. The main focus of this paper is to outline techniques for depositing and manipulating nanometer-scale structures using STM tips. Firstly, the transfer of STM tip material through the application of voltage pulses is introduced. The highly reproducible fabrication of metallic silver nanodots and nanowires is discussed. The mechanism is thought to be spontaneous point-contact formation caused by field-enhanced diffusion to the apex of the tip. Transfer through the application of z-direction pulses is also introduced. Sub-nanometer displacement pulses along the z-direction form point contacts that can be used for reproducible nanodot deposition. Next, the discovery of the STM structural manipulation of surface phases is discussed. It has been demonstrated that superstructures on Si(001) surfaces can be reverse-manipulated by controlling the injected carriers. Finally, the fabrication of an atomic-scale one-dimensional quantum confinement system by single-atom deposition using a controlled point contact is presented. Because of its combined nanofabrication and nanocharacterization capabilities, STM is a powerful tool for exploring the nanotechnology and nanoscience fields. PMID:27877921

  20. Visualizing Topological Surface States using Scanning Tunneling Microscopy and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Yazdani, Ali

    2010-03-01

    Topological insulators are a new class of insulators in which a bulk gap for electronic excitations is generated by strong spin-orbit coupling. These novel materials are distinguished from ordinary insulators by the presence of gapless metallic boundary states, akin to the chiral edge modes in quantum Hall systems, but with unconventional spin textures. Angle resolved photoemission experiments and theoretical efforts have provided strong evidence for bulk topological insulators and their spin-chiral surface states in several Bi-based compounds. We have performed scanning tunneling microscopy and spectroscopic studies of topological surface states on a range of different compounds. I will describe how these experiments illustrate the importance of the spin-texture of these novel states on their scattering and quantum confinement. Experiments demonstrate that these states are protected from backscattering between opposite spin states due to their chiral spin textures. [1]. More recently, our studies were extended to determine the interplay between the influence of spin symmetry on scattering and the possibility of energy level quantization due to geometric confinement for topological surface states. [2] Work was done in collaboration with P. Roushan, J. Seo, H. Beidenkopf, Y.-S. Hor, C. Parker, D. Hsieh, D. Qian, and A. Richardella, M. Z. Hasan, R. Cava. Supported by ARO, ONR, and MRSEC through PCCM. [4pt] [1] P. Roushan et al. Nature 460, 1106 (2009). [0pt] [2] J. Seo et al. submitted (2009).

  1. Scanning Tunneling Microscopy Studies of Diamond Films and Optoelectronic Materials

    NASA Technical Reports Server (NTRS)

    Perez, Jose M.

    1996-01-01

    We present a summary of the research, citations of publications resulting from the research and abstracts of such publications. We have made no inventions in the performance of the work in this project. The main goals of the project were to set up a Chemical Vapor Deposition (CVD) diamond growth system attached to an UltraHigh Vacuum (UHV) atomic resolution Scanning Tunneling Microscopy (STM) system and carry out experiments aimed at studying the properties and growth of diamond films using atomic resolution UHV STM. We successfully achieved these goals. We observed, for the first time, the atomic structure of the surface of CVD grown epitaxial diamond (100) films using UHV STM. We studied the effects of atomic hydrogen on the CVD diamond growth process. We studied the electronic properties of the diamond (100) (2x1) surface, and the effect of alkali metal adsorbates such as Cs on the work function of this surface using UHV STM spectroscopy techniques. We also studied, using STM, new electronic materials such as carbon nanotubes and gold nanostructures. This work resulted in four publications in refereed scientific journals and five publications in refereed conference proceedings.

  2. Scanning Tunneling Microscopy of Dirac Fermions at mK Temperatures

    NASA Astrophysics Data System (ADS)

    Stroscio, Joseph

    2011-03-01

    Since the beginning of the last century new frontiers in physics have emerged when advances in instrumentation achieved lower experimental operating temperatures. Notable examples include the discovery of superconductivity and the integer and fractional quantum Hall effects. New experimental techniques are continually adapted in order to meet new experimental challenges. A case in point is scanning tunneling microscopy (STM) which has seen a wealth of new measurements emerge as cryogenic STM instruments have been developed in the last two decades. In this talk I describe the design, development and performance of a scanning probe microscopy facility operating at a base temperature of 10 mK in magnetic fields up to 15 T. The microscope is cooled by a custom designed, fully ultra-high vacuum (UHV) compatible dilution refrigerator (DR) and is capable of in-situ tip and sample exchange. Sub-picometer stability at the tip-sample junction is achieved through three independent vibration isolation stages and careful design of the dilution refrigerator. The system can be connected to, or disconnected from, a network of interconnected auxiliary UHV chambers used for sample and probe tip preparation. Current measurements are focusing on Dirac fermions in graphene and in topological insulators. The history of the fractional quantum Hall states in semiconductor heterostructures suggests that studying graphene at lower temperatures and higher magnetic fields may reveal new quantum phases of matter. Scanning tunneling spectroscopy of graphene at mK temperatures reveals the detailed structure of the degenerate Landau levels in graphene, resolving the full quartet of states corresponding to the lifting of the spin and valley dengeneracies. When the Fermi level lies inside the four-fold Landau manifold, significant electron correlation effects result in enhanced valley splitting and spin splitting. New many-body states are observed at fractional filling factors of 7/2, 9/2, and 11/2.

  3. Tunnelling junctions with additional degrees of freedom: An extended toolbox of scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Wagner, Christian; Temirov, Ruslan

    2015-05-01

    Considering studies of molecular adsorption we review recent developments in the field of scanning probe microscopy and in particular in scanning tunnelling microscopy, concentrating on the progress that has been achieved by controlled decoration of the microscope tip. A view is presented according to which the tip decoration generally introduces additional degrees of freedom into the scanning junction and thus extends its functionality. In particular tips decorated with atomic point-like particles may attain the additional function of a force sensor which is realized through the degrees of freedom associated with the relative position of the decorating probe-particle with respect to the tip. It is shown how the force sensor function of such tips helps when studying large molecular adsorbates. Further prospects of more complex junctions equipped with numerous internal degrees of freedom are discussed. It is argued that the main problem impeding the utilization of such junctions is related to their control. An approach towards a higher degree of control is presented that is based on the analysis of single molecule manipulation experiments.

  4. Josephson scanning tunneling microscopy -- a local and direct probe of the superconducting order parameter

    SciTech Connect

    Kimura, Hikari; Dynes, Robert; Barber Jr., Richard. P.; Ono, S.; Ando, Y.

    2009-09-01

    Direct measurements of the superconducting superfluid on the surface of vacuum-cleaved Bi2Sr2CaCu2O8+delta (BSCCO) samples are reported. These measurements are accomplished via Josephson tunneling into the sample using a novel scanning tunneling microscope (STM) equipped with a superconducting tip. The spatial resolution of the STM of lateral distances less than the superconducting coherence length allows it to reveal local inhomogeneities in the pair wavefunction of the BSCCO. Instrument performance is demonstrated first with Josephson measurements of Pb films followed by the layered superconductor NbSe2. The relevant measurement parameter, the Josephson ICRN product, is discussed within the context of both BCS superconductors and the high transition temperature superconductors. The local relationship between the ICRN product and the quasiparticle density of states (DOS) gap are presented within the context of phase diagrams for BSCCO. Excessive current densities can be produced with these measurements and have been found to alter the local DOS in the BSCCO. Systematic studies of this effect were performed to determine the practical measurement limits for these experiments. Alternative methods for preparation of the BSCCO surface are also discussed.

  5. Time-resolved scanning tunneling microscopy for studies of nanoscale magnetization dynamics

    NASA Astrophysics Data System (ADS)

    Loth, Sebastian

    2015-03-01

    The time resolution of the scanning tunneling microscope can be boosted greatly by use of electronic pump probe measurement schemes. Pulse shaping of the input pulses can even overcome bandwidth limitations of the instrument and enables sub-nanosecond time resolution. In this talk we will focus on applications of this technique for measurements of fast spin dynamics in nanomagnets. We use the probe tip of a low-temperature STM to arrange magnetic atoms into arrays of our own design. Thin insulating films decouple the atoms from the supporting metallic substrate so that the nanostructures show quantum-magnetic properties with discrete spin states. The time-domain information gained in pump probe spectroscopy quantifies the spin relaxation between metastable spin states. It enables isolating the interaction between the nanomagnet and its environment. In particular, we find that the magnetic atoms of a spin-polarized STM tip interact significantly with the surface even at moderate tunneling conditions. This interaction acts analogously to a highly localized magnetic field. It depends exponentially on the tip-nanomagnet distance and can reach a strength of several tesla. We use this atomically localized magnetic field to control the spin state mixing of a nanomagnet in an avoided level crossing of low-energy spin states. Furthermore, pump probe spectroscopy enables non-local measurements of magnetic states and highlights pathways to design and control magnetism at the single atom level.

  6. Sub-nanosecond time-resolved near-field scanning magneto-optical microscope.

    PubMed

    Rudge, J; Xu, H; Kolthammer, J; Hong, Y K; Choi, B C

    2015-02-01

    We report on the development of a new magnetic microscope, time-resolved near-field scanning magneto-optical microscope, which combines a near-field scanning optical microscope and magneto-optical contrast. By taking advantage of the high temporal resolution of time-resolved Kerr microscope and the sub-wavelength spatial resolution of a near-field microscope, we achieved a temporal resolution of ∼50 ps and a spatial resolution of <100 nm. In order to demonstrate the spatiotemporal magnetic imaging capability of this microscope, the magnetic field pulse induced gyrotropic vortex dynamics occurring in 1 μm diameter, 20 nm thick CoFeB circular disks has been investigated. The microscope provides sub-wavelength resolution magnetic images of the gyrotropic motion of the vortex core at a resonance frequency of ∼240 MHz.

  7. Scanning tunnelling microscopy of charge-density waves in transition metal chalcogenides

    NASA Astrophysics Data System (ADS)

    Coleman, R. V.; Giambattista, B.; Hansma, P. K.; Johnson, A.; McNairy, W. W.; Slough, C. G.

    1988-11-01

    We have used scanning tunnelling microscopes (STMs) operating at liquid helium and liquid nitrogen temperatures to image the charge-density waves (CDWs) in transition metal chalcogenides. The layer structure dichalcogenides TaSe2, TaS2, NbSe2, VSe2, TiSe2 and TiS2 have been studied including representative polytype phases such as 1T, 2H and 4Hb. Experimental results are presented for the complete range of CDW amplitudes and structures observed in these materials. In most cases both the CDW and the surface atomic structure have been simultaneously imaged. Results on the trichalcogenide NbSe3 are also included.The formation of the CDW along with the associated periodic lattice distortion gaps the Fermi surface (FS) and modifies the local density-of-states (LDOS) detected by the tunnelling process. The tunnelling microscopes have been operated mostly in the constant current mode which maps the LDOS at the position of the tunnelling tip. The relative amplitudes and profiles of the CDW superlattice and the atomic lattice have been measured and confirm on an atomic scale the CDW structures predicted by X-ray, electron and neutron diffraction. The absolute STM deflections are larger than expected for the CDW induced modifications of the LDOS above the surface and possible enhancement mechanisms are reviewed.In the 2H trigonal prismatic coordination phases the CDWs involve a relatively small charge transfer and the atomic structure dominates the STM images. In the 1T octahedral coordination phases the charge transfer is large and the CDW structure dominates the STM image with an anomalously large enhancement of the STM profile. Systematic comparison of the STM profiles with band structure and FS information is included.In the case of the 4Hb mixed coordination phases at the lowest temperatures two nearly independent CDWs form in alternate sandwiches. STM studies on 4Hb crystals with both octahedral and trigonal prismatic surface sandwiches have been carried out. The STM

  8. Scanning tunneling microscopy studies of mixed self-assembled monolayers

    NASA Astrophysics Data System (ADS)

    Raigoza, Annette Fernandez

    This thesis examines the formation of multicomponent self-assembled mono-layers (SAMs) on the Au(111) surface using scanning tunneling microscopy. Two methods, sequential adsorption and coadsorption, are used to create these mixed SAMs. In the sequential adsorption experiments, a clean Au(111)-on-mica sub-strate is exposed to the first molecular species and then this adsorbate-covered sample is exposed to the second molecular species. Alternately, in the coadsorption experiments, a gold surface is exposed to both adsorbates simultaneously. Exposing a coronene- or dithiocarbamate-covered surface to excess thiol in the vapor phase results in a drastic restructuring of the initial surface. This is primarily driven by the kinetics of the octanethiol monolayer formation process, but the extent to which this happens is dependent on the molecule-molecule and molecule-surface interactions of the adsorbate due to the initial coverage and order of the monolayer. An octanethiolate monolayer is also substantially modified when immersed in a solution containing dithiocarbamate (DTC). Defects in the octanethiol monolayer are prime sites for molecular exchange. A surplus of DTC in the solution drives substitution that can lead to the complete removal of thiol from the surface. When a Au(111) surface is exposed to solutions containing both octanethiol and dithiocarbamate (DTC), both molecular species compete for available ad- sorption sites. At equal octanethiol-to-DTC ratios, molecular exchange hinders octanethiol monolayer formation. Higher octanethiol concentration in solution results in the incorporation of thiol into the resulting monolayer, with a strong dependence on the chain length of the DTC molecules.

  9. Probing of basal planes of MoS2 by scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; Henson, Tammy D.; Armstrong, Neal R.; Bell, L. Stephen

    1988-06-01

    Atomically resolved images of MoS2 have been obtained using scanning tunneling microscopy with both positively and negatively biased samples yielding the hexagonal symmetry of the surface of the crystal. Also measured were curves of tunneling current as a function of bias voltage, from which the density of states of the valence and conduction bands can be inferred.

  10. A 3-d laser scanning system and scan data processing method for the monitoring of tunnel deformations

    NASA Astrophysics Data System (ADS)

    Chmelina, Klaus; Jansa, Josef; Hesina, Gerd; Traxler, Christoph

    2012-11-01

    The paper presents the mobile multi-sensor system Orthos Plus for the monitoring and mapping of tunnel walls, a scan data processing method for the evaluation of 3-d tunnel wall displacements from subsequent wall scans and, finally, a virtual reality tool supporting the interpretation of data. The measuring system consists of a 3-d laser scanner, a motorised total station and a digital camera that are integrated on a light metal frame that is installed on a mobile platform. It has been designed to perform tunnel measurements most efficiently and to meet the special requirements of tunnels under construction. The evaluation of 3-d displacements is based on a 3-d matching algorithm that takes advantage of the particular conditions of tunnel (shotcrete) surfaces. The virtual reality tool allows viewing of data in a 3-d virtual reality tunnel model and their animation in time and space in order supports understanding in an optimal way. The measuring system Orthos Plus has been developed in the course of a national research project, the 3-d matching method in the frame of the Austrian Christian Doppler Laboratory Spatial Data from Laser Scanning and Remote Sensing and the VR tool in the Austrian COMET K1 Competence Center VRVis Center (www.vrvis.at).

  11. Study on molecular cavity of oligoamide macrocycles by using scanning tunneling microscopy.

    PubMed

    Wang, Yibing; Li, Yibao; Luo, Yin; Xu, Meng; Zhang, Xuemei; Guo, Yuanyuan; Wei, Guanghong; Yuan, Lihua; Gong, Bing; Yang, Yanlian; Wang, Chen

    2012-11-12

    The molecular structures and assembly structures of aromatic oligoamide macrocycles are identified by using scanning tunneling microscopy at liquid/solid interface, which shows persistent shapes, tunable cavity sizes, and binding of water molecules.

  12. [Scanning electron microscope study of chemically disinfected endodontic files].

    PubMed

    Navarro, G; Mateos, M; Navarro, J L; Canalda, C

    1991-01-01

    Forty stainless steel endodontic files were observed at scanning electron microscopy after being subjected to ten disinfection cycles of 10 minutes each one, immersed in different chemical disinfectants. Corrosion was not observed on the surface of the files in circumstances that this study was made.

  13. Imaging the Predicted Isomerism of Oligo(aniline)s: A Scanning Tunneling Microscopy Study.

    PubMed

    Thomas, James O; Andrade, Hugo D; Mills, Benjamin M; Fox, Neil A; Hoerber, Heinrich J K; Faul, Charl F J

    2015-07-01

    The self-assembly of two emeraldine base tetra(aniline) derivatives is investigated using scanning tunneling microscopy. A combination of the scanning tunneling microscopy data and calculations reveals the presence of predicted cis/trans isomerism in this oxidation state. This isomerism is shown to hinder self-assembly into ordered structures, and provides indications as to why the properties of these materials, and their parent polymer, polyaniline, remain unfulfilled.

  14. Large area fabrication of plasmonic nanoparticle grating structure by conventional scanning electron microscope

    SciTech Connect

    Sudheer, Tiwari, P.; Rai, V. N.; Srivastava, A. K.; Mukharjee, C.

    2015-06-24

    Plasmonic nanoparticle grating (PNG) structure of different periods has been fabricated by electron beam lithography using silver halide based transmission electron microscope film as a substrate. Conventional scanning electron microscope is used as a fabrication tool for electron beam lithography. Optical microscope and energy dispersive spectroscopy (EDS) have been used for its morphological and elemental characterization. Optical characterization is performed by UV-Vis absorption spectroscopic technique.

  15. Quantitative analysis of scanning tunneling microscopy images of mixed-ligand-functionalized nanoparticles.

    PubMed

    Biscarini, Fabio; Ong, Quy Khac; Albonetti, Cristiano; Liscio, Fabiola; Longobardi, Maria; Mali, Kunal S; Ciesielski, Artur; Reguera, Javier; Renner, Christoph; De Feyter, Steven; Samorì, Paolo; Stellacci, Francesco

    2013-11-12

    Ligand-protected gold nanoparticles exhibit large local curvatures, features rapidly varying over small scales, and chemical heterogeneity. Their imaging by scanning tunneling microscopy (STM) can, in principle, provide direct information on the architecture of their ligand shell, yet STM images require laborious analysis and are challenging to interpret. Here, we report a straightforward, robust, and rigorous method for the quantitative analysis of the multiscale features contained in STM images of samples consisting of functionalized Au nanoparticles deposited onto Au/mica. The method relies on the analysis of the topographical power spectral density (PSD) and allows us to extract the characteristic length scales of the features exhibited by nanoparticles in STM images. For the mixed-ligand-protected Au nanoparticles analyzed here, the characteristic length scale is 1.2 ± 0.1 nm, whereas for the homoligand Au NPs this scale is 0.75 ± 0.05 nm. These length scales represent spatial correlations independent of scanning parameters, and hence the features in the PSD can be ascribed to a fingerprint of the STM contrast of ligand-protected nanoparticles. PSD spectra from images recorded at different laboratories using different microscopes and operators can be overlapped across most of the frequency range, proving that the features in the STM images of nanoparticles can be compared and reproduced.

  16. Preparation of scanning tunneling microscopy tips using pulsed alternating current etching

    SciTech Connect

    Valencia, Victor A.; Thaker, Avesh A.; Derouin, Jonathan; Valencia, Damian N.; Farber, Rachael G.; Gebel, Dana A.; Killelea, Daniel R.

    2015-03-15

    An electrochemical method using pulsed alternating current etching (PACE) to produce atomically sharp scanning tunneling microscopy (STM) tips is presented. An Arduino Uno microcontroller was used to control the number and duration of the alternating current (AC) pulses, allowing for ready optimization of the procedures for both Pt:Ir and W tips using a single apparatus. W tips prepared using constant and pulsed AC power were compared. Tips fashioned using PACE were sharper than those etched with continuous AC power alone. Pt:Ir tips were prepared with an initial coarse etching stage using continuous AC power followed by fine etching using PACE. The number and potential of the finishing AC pulses was varied and scanning electron microscope imaging was used to compare the results. Finally, tip quality using the optimized procedures was verified by UHV-STM imaging. With PACE, at least 70% of the W tips and 80% of the Pt:Ir tips were of sufficiently high quality to obtain atomically resolved images of HOPG or Ni(111)

  17. Scanning Tunneling Microscopy Study on Strongly Correlated Materials

    NASA Astrophysics Data System (ADS)

    He, Yang

    Strongly correlated electrons and spin-orbit interaction have been the two major research directions of condensed matter physics in recent years. The discovery of high temperature superconductors in 1986 not only brought excitement into the field but also challenged our theory on quantum materials. After almost three decades of extensive study, the underlying mechanism of high temperature superconductivity is still not fully understood, the reason for which is mainly a poor understanding of strongly correlated systems. The phase diagram of cuprate superconductors has become more complicated throughout the years as multiple novel electronic phases have been discovered, while few of them are fully understood. Topological insulators are a newly discovered family of materials bearing topological non-trivial quantum states as a result of spin-orbit coupling. The theoretically predicted topological Kondo insulators as strongly correlated systems with strong spin-orbital coupling make an ideal playground to test our theory of quantum materials. Scanning tunneling microscopy (STM) is a powerful technique to explore new phenomena in materials with exotic electronic states due to its high spacial resolution and high sensitivity to low energy electronic structures. Moreover, as a surface-sensitive technique, STM is an ideal tool to investigate the electronic properties of topological and non-topological surface states. In this thesis, I will describe experiments we performed on high temperature superconductors and topological Kondo insulators using STM. First, I will describe our experiments on a Bi-based high temperature superconductor Bi2Sr2CuO6+delta. The quasiparticle interference technique uncovers a Fermi surface reconstruction. We also discovered the coexistence of Bogoliubov quasiparticle and pseudogap state at the antinodes. Afterwards, I will discuss our discovery of d-form factor density wave in the same material, showing the omnipresence of d form factor density

  18. Scanning Tunneling Microscopy and Spectroscopy of Silicon and Carbon Surfaces

    NASA Astrophysics Data System (ADS)

    Baker, Shenda Mary

    1992-01-01

    Scanning Tunneling Microscopy (STM) investigations and additional surface analyses were performed on carbon and silicon surfaces. A number of anomalies have been observed on highly oriented pyrolytic graphite (HOPG), including large corrugations, distorted images, large range of tip motion and the absence of defects. A mechanism involving direct contact between tip and sample or contact through a contamination layer to provide an additional conducting pathway is proposed. This model of point-contact imaging provides an explanation for added stability of the STM system, a mechanism for producing multiple tips or sliding graphite planes and an explanation for the observed anomalies. These observations indicate that the use of HOPG for testing and calibration of STM instrumentation may be misleading. Designs for the atmospheric STM used in this study are also presented. The conditions necessary for preparing a clean silicon(111) (7x7) surface are discussed. The design and analysis of heaters necessary to prepare the silicon reconstructed surface at ultrahigh vacuum (UHV) are described. Results from both radiatively and resistively heated samples are shown in addition to a comparison of topographic and barrier height images of the boron (surd 3 times surd 3) reconstructed surfaces. A spectroscopic distinction between sites of boron, silicon or contaminants is demonstrated. A synthetic boron-doped diamond was examined by a number of analytical techniques in order to determine its composition and surface morphology. Current-voltage spectroscopy taken with the STM indicates that the diamond Fermi level can be pinned in atmospheric conditions. In ultrahigh vacuum, band bending is observed, but the strength of the electric field experienced by the diamond semiconductor is less than expected; introduction of surface charges is shown to account for the field screening. Presentation of an STM study of a protein-antibody complex on a gold surface illustrates the requirements

  19. Scanning electron microscopic study on Toxascaris transfuga (Rudolphi, 1819) (Nematoda).

    PubMed

    Tenora, F; Mituch, J; Hovorka, I

    1989-01-01

    The authors present original observations on the species Toxascaris transfuga obtained by means of scanning electron microscopy. Attention was paid to the structure of head end, morphology of papillae of the head and abdominal end, specific morphological traits of cloacae edges and morphology of the egg surface. Presented are morphological criteria which apparently differentiate the species T. transfuga from T. leonina (Linstow, 1902). T. transfuga and T. multipapillata Kreis, 1938 seem to be conspecific.

  20. Laser scanning confocal microscope with programmable amplitude, phase, and polarization of the illumination beam.

    PubMed

    Boruah, B R; Neil, M A A

    2009-01-01

    We describe the design and construction of a laser scanning confocal microscope with programmable beam forming optics. The amplitude, phase, and polarization of the laser beam used in the microscope can be controlled in real time with the help of a liquid crystal spatial light modulator, acting as a computer generated hologram, in conjunction with a polarizing beam splitter and two right angled prisms assembly. Two scan mirrors, comprising an on-axis fast moving scan mirror for line scanning and an off-axis slow moving scan mirror for frame scanning, configured in a way to minimize the movement of the scanned beam over the pupil plane of the microscope objective, form the XY scan unit. The confocal system, that incorporates the programmable beam forming unit and the scan unit, has been implemented to image in both reflected and fluorescence light from the specimen. Efficiency of the system to programmably generate custom defined vector beams has been demonstrated by generating a bottle structured focal volume, which in fact is the overlap of two cross polarized beams, that can simultaneously improve both the lateral and axial resolutions if used as the de-excitation beam in a stimulated emission depletion confocal microscope.

  1. Imaging graphite in air by scanning tunneling microscopy - Role of the tip

    NASA Technical Reports Server (NTRS)

    Colton, R. J.; Baker, S. M.; Driscoll, R. J.; Youngquist, M. G.; Baldeschwieler, J. D.; Kaiser, W. J.

    1988-01-01

    Atomically resolved images of highly oriented pyrolytic graphite (HOPG) in air at point contact have been obtained. Direct contact between tip and sample or contact through a contamination layer provides a conduction mechanism in addition to the exponential tunneling mechanism responsible for scanning tunneling microscopy (STM) imaging. Current-voltage (I-V) spectra were obtained while scanning in the current imaging mode with the feedback circuit interrupted in order to study the graphite imaging mechanism. Multiple tunneling tips are probably responsible for images without the expected hexagonal or trigonal symmetry. The observations indicate that the use of HOPG for testing and calibration of STM instrumentation may be misleading.

  2. Scanning tunneling microscopy studies of charge transport in cadmium selenide/zinc sulfide quantum dots

    NASA Astrophysics Data System (ADS)

    Hummon, Marissa Rachel

    2009-12-01

    This thesis examines charge transport in individual colloidal nanocrystals (quantum dots) using a scanning tunneling microscope. We observe coulomb blockade (CB) at room temperature and extract the charging energy of the quantum dot (QD). We analyze time-dependent CB measurements to determine the lifetime and energy of the trapped charge on the QD. A model of the lifetime is presented, furthering our analysis of the charge detrapping mechanism. We observe a hysteresis in the current-voltage (IV) tunneling spectra as the substrate bias is swept from empty to filled states and then back to empty states. This hysteresis is consistent with trapped charge(s) presenting an additional potential barrier to tunneling, a measure of CB. Traditional CB experiments measure a coulomb repulsion due to charge build-up on the island between two electrodes. We observe CB, hysteresis in successive IV sweeps, due to charge trapping/detrapping in a state other than the transport level. This trap state may be related to the dark state in blinking experiments. Optical and electrical measurements of QD trap states are often related to a puzzling physical phenomena observed universally in QDs: blinking. Blinking is the stochastic photoluminescence behavior of quantum dots, where, under constant excitation by a laser, a QD does not emit a continuous stream of photons. In fact, the QD will blink "on" and "off" for completely unpredictable durations that are thought to be related to the QD being in either a neutral or charged state. We measure a lifetime for the charged state of 15 +/- 7 s when Vsub ≤ 1.5 V and 170 +/- 140 ms when Vsub ≥ 1.6 V. The abrupt transition in lifetime between 1.5 and 1.6 V implies that this is the voltage necessary to lower the Au Fermi level equal to the trap state energy, thus allowing the trapped charge to tunnel out of the trap state. The voltage drop between the QD and substrate, determined from a self-consistent calculation of the relative capacitance

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

    NASA Astrophysics Data System (ADS)

    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.

  4. The design and construction of a cost-efficient confocal laser scanning microscope

    NASA Astrophysics Data System (ADS)

    Xi, Peng; Rajwa, Bartlomiej; Jones, James T.; Robinson, J. Paul

    2007-03-01

    The optical dissection ability of confocal microscopy makes it a powerful tool for biological materials. However, the cost and complexity of confocal scanning laser microscopy hinders its wide application in education. We describe the construction of a simplified confocal scanning laser microscope and demonstrate three-dimensional projection based on cost-efficient commercial hardware, together with available open source software.

  5. Compact scanning transmission x-ray microscope at the photon factory

    SciTech Connect

    Takeichi, Yasuo Inami, Nobuhito; Ono, Kanta; Suga, Hiroki; Takahashi, Yoshio

    2016-01-28

    We report the design and performance of a compact scanning transmission X-ray microscope developed at the Photon Factory. Piezo-driven linear stages are used as coarse stages of the microscope to realize excellent compactness, mobility, and vibrational and thermal stability. An X-ray beam with an intensity of ∼10{sup 7} photons/s was focused to a diameter of ∼40 nm at the sample. At the soft X-ray undulator beamline used with the microscope, a wide range of photon energies (250–1600 eV) is available. The microscope has been used to research energy materials and in environmental sciences.

  6. Scanning electron microscope studies of human metaphase chromosomes.

    PubMed

    Shemilt, L A; Estandarte, A K C; Yusuf, M; Robinson, I K

    2014-03-06

    Scanning electron microscopy (SEM) is used to evaluate potential chromosome preparations and staining methods for application in high-resolution three-dimensional X-ray imaging. Our starting point is optical fluorescence microscopy, the standard method for chromosomes, which only gives structural detail at the 200 nm scale. In principle, with suitable sample preparation protocols, including contrast enhancing staining, the surface structure of the chromosomes can be viewed at the 1 nm level by SEM. Here, we evaluate a heavy metal nucleic-acid-specific stain, which gives strong contrast in the backscattered electron signal. This study uses SEM to examine chromosomes prepared in different ways to establish a sample preparation protocol for X-rays. Secondary electron and backscattered electron signals are compared to evaluate the effectiveness of platinum-based stains used to enhance the contrast.

  7. Length Dependence of Tunneling Current Through Single Phenylene Oligomers Measured by Scanning Tunneling Microscopy at Low Temperature

    NASA Astrophysics Data System (ADS)

    Wakamatsu, Satoshi; Fujii, Shintaro; Akiba, Uichi; Fujihira, Masamichi

    2006-04-01

    The length dependence of tunneling current through single phenylene oligomers, i.e., benzenemethanethiol, 4-biphenylmethanethiol and [1,1':4',1''-terphenyl]-4-methanethiol, was determined experimentally by scanning tunneling microscopy (STM). The single phenylene oligomers were isolated in a self-assembled monolayer (SAM) matrix of a disulfide with two spherical bicyclo[2.2.2]octane moieties on Au(111). The STM measurement was conducted at a low temperature to prevent the thermal motions of the isolated molecules that occur at room temperature. The isolated single molecules inserted in the SAM matrix were observed as protrusions in an STM topography using a constant-current mode owing to their higher tunneling ability. The decay constant, β, of the tunneling current through single phenylene oligomers was estimated from the STM heights of the protrusions corresponding to the single phenylene oligomers using a bilayer tunnel junction model. The value of β for tunneling current through single phenylene oligomers was 5.5 ± 0.2 nm-1. In a constant-height mode, we measured the conductance of the isolated single molecules. We estimated an averaged single-molecular conductance of the isolated molecules of a biphenyl derivative to be ca. 2 nS. Here, one side of each isolated molecule was bound via an Au-S bond and the other phenyl end was physically in contact with an Au STM tip.

  8. Scanning Tunneling Microscopy Studies of Oxide Surface Structure

    NASA Astrophysics Data System (ADS)

    Novak, David S.

    The structural properties of several oxide and metal/oxide systems have been investigated using scanning tunneling microscopy (STM). Oxide materials find wide use in many very important technological applications, and many of these applications depend on nanometer scale structure of the material. STM provides a unique tool for probing the properties of materials in real-space on the atomic ({~}1A) and nanometer distance scales. Oxides are also scientifically interesting for the wide range of physical properties that they exhibit. In these investigations we have studied the surface structure of the metallic oxide Rb _{0.3}MoO_3, the wide band gap semiconductor TiO_2(110), and metal thin films of copper on TiO_2 (110). Much of this research was performed with a UHV STM system which was built in-house at Rutgers. The design and construction of this UHV STM system, including the STM scanners and control electronics, is described in this dissertation. We have prepared nearly perfect TiO_2 (110) (1 x 1) surfaces which are observed with STM to be atomically flat over large areas. The atomic scale structure of the (1 x 1) surface has been successfully imaged with the STM, and the periodicity found in the images is consistent with the bulk truncated (charge neutral) model for the TiO_2(110) (1 x 1) surface. A discussion is given as to whether the STM is imaging the bridging oxygen atom rows (geometric structure dominating) or the five-fold coordinated titanium site (electronic structure dominating). Under certain preparation conditions, a line defect structure is observed on this surface. The defect structure consists of a rowlike feature of approximately 2 A height oriented along the (001). It is believed that these defect rows are the initial steps in the formation of the "high temperature" (1 x 2) phase which has been observed by several groups. A comparison is made between the experimental data and the various models that have been proposed for the defect rows and the

  9. A study of surface diffusion with the scanning tunneling microscope from fluctuations of the tunneling current

    SciTech Connect

    Manuel, Lozano

    1996-01-12

    The transport of atoms or molecules over surfaces has been an important area of study for several decades now, with its progress generally limited by the available experimental techniques to characterize the phenomena. A number of methods have been developed over the years to measure surface diffusion yet only very few systems have been characterized to this day mainly due to the physical limitations inherent in these available methods. Even the STM with its astonishing atomically-resolved images of the surface has been limited in terms of its capability to determine mass transport properties. This is because the STM is inherently a ``slow`` instrument, i.e., a finite time is needed for signal averaging in order to produce the image. A need exists for additional surface diffusion measurement techniques, ideally ones which are able to study varied systems and measure a wide range of diffusion rates. The STM (especially because of its highly local nature) presents itself as a promising tool to conduct dynamical studies if its poor time resolution during ``normal operation`` can somehow be overcome. The purpose of this dissertation is to introduce a new technique of using the STM to measure adatom mobility on surfaces -- one with a capacity to achieve excellent time resolution.

  10. Flow cytometric and laser scanning microscopic approaches in epigenetics research.

    PubMed

    Szekvolgyi, Lorant; Imre, Laszlo; Minh, Doan Xuan Quang; Hegedus, Eva; Bacso, Zsolt; Szabo, Gabor

    2009-01-01

    Our understanding of epigenetics has been transformed in recent years by the advance of technological possibilities based primarily on a powerful tool, chromatin immunoprecipitation (ChIP). However, in many cases, the detection of epigenetic changes requires methods providing a high-throughput (HTP) platform. Cytometry has opened a novel approach for the quantitative measurement of molecules, including PCR products, anchored to appropriately addressed microbeads (Pataki et al. 2005. Cytometry 68, 45-52). Here we show selected examples for the utility of two different cytometry-based platforms of epigenetic analysis: ChIP-on-beads, a flow-cytometric test of local histone modifications (Szekvolgyi et al. 2006. Cytometry 69, 1086-1091), and the laser scanning cytometry-based measurement of global epigenetic modifications that might help predict clinical behavior in different pathological conditions. We anticipate that such alternative tools may shortly become indispensable in clinical practice, translating the systematic screening of epigenetic tags from basic research into routine diagnostics of HTP demand.

  11. In situ fatigue loading stage inside scanning electron microscope

    NASA Technical Reports Server (NTRS)

    Telesman, Jack; Kantzos, Peter; Brewer, David

    1988-01-01

    A fatigue loading stage inside a scanning electron microscopy (SEM) was developed. The stage allows dynamic and static high-magnification and high-resolution viewing of the fatigue crack initiation and crack propagation processes. The loading stage is controlled by a closed-loop servohydraulic system. Maximum load is 1000 lb (4450 N) with test frequencies ranging up to 30 Hz. The stage accommodates specimens up to 2 inches (50 mm) in length and tolerates substantial specimen translation to view the propagating crack. At room temperature, acceptable working resolution is obtainable for magnifications ranging up to 10,000X. The system is equipped with a high-temperature setup designed for temperatures up to 2000 F (1100 C). The signal can be videotaped for further analysis of the pertinent fatigue damage mechanisms. The design allows for quick and easy interchange and conversion of the SEM from a loading stage configuration to its normal operational configuration and vice versa. Tests are performed entirely in the in-situ mode. In contrast to other designs, the NASA design has greatly extended the life of the loading stage by not exposing the bellows to cyclic loading. The loading stage was used to investigate the fatigue crack growth mechanisms in the (100)-oriented PWA 1480 single-crystal, nickel-based supperalloy. The high-magnification observations revealed the details of the crack growth processes.

  12. Environmental scanning electron microscope imaging examples related to particle analysis.

    PubMed

    Wight, S A; Zeissler, C J

    1993-08-01

    This work provides examples of some of the imaging capabilities of environmental scanning electron microscopy applied to easily charged samples relevant to particle analysis. Environmental SEM (also referred to as high pressure or low vacuum SEM) can address uncoated samples that are known to be difficult to image. Most of these specimens are difficult to image by conventional SEM even when coated with a conductive layer. Another area where environmental SEM is particularly applicable is for specimens not compatible with high vacuum, such as volatile specimens. Samples from which images were obtained that otherwise may not have been possible by conventional methods included fly ash particles on an oiled plastic membrane impactor substrate, a one micrometer diameter fiber mounted on the end of a wire, uranium oxide particles embedded in oil-bearing cellulose nitrate, teflon and polycarbonate filter materials with collected air particulate matter, polystyrene latex spheres on cellulosic filter paper, polystyrene latex spheres "loosely" sitting on a glass slide, and subsurface tracks in an etched nuclear track-etch detector. Surface charging problems experienced in high vacuum SEMs are virtually eliminated in the low vacuum SEM, extending imaging capabilities to samples previously difficult to use or incompatible with conventional methods.

  13. Scanning Tunneling Microscopy, Atomic Force Microscopy, and Related Techniques

    DTIC Science & Technology

    1992-02-26

    primary surface contaminants on electrochemically etched tunpten STM tips as CO. graphite, WC, and tungsten oxide (B55). Several unusual STM tips...the energy density of states by a contamination -induced peak, charging of electron traps, and resonant tunneling in a double- barier quantum well...inequivalent molecules in the unit cell of a free standing tetracene crystal (D371). Atomic resolution on different faces of the conductive perylene radical

  14. Contact-Free Scanning and Imaging with the Scanning Ion Conductance Microscope

    PubMed Central

    2014-01-01

    Scanning ion conductance microscopy (SICM) offers the ability to obtain very high-resolution topographical images of living cells. One of the great advantages of SICM lies in its ability to perform contact-free scanning. However, it is not yet clear when the requirements for this scan mode are met. We have used finite element modeling (FEM) to examine the conditions for contact-free scanning. Our findings provide a framework for understanding the contact-free mode of SICM and also extend previous findings with regard to SICM resolution. Finally, we demonstrate the importance of our findings for accurate biological imaging. PMID:24521282

  15. Local imaging of high mobility two-dimensional electron systems with virtual scanning tunneling microscopy

    SciTech Connect

    Pelliccione, M.; Bartel, J.; Goldhaber-Gordon, D.; Sciambi, A.; Pfeiffer, L. N.; West, K. W.

    2014-11-03

    Correlated electron states in high mobility two-dimensional electron systems (2DESs), including charge density waves and microemulsion phases intermediate between a Fermi liquid and Wigner crystal, are predicted to exhibit complex local charge order. Existing experimental studies, however, have mainly probed these systems at micron to millimeter scales rather than directly mapping spatial organization. Scanning probes should be well-suited to study the spatial structure of these states, but high mobility 2DESs are found at buried semiconductor interfaces, beyond the reach of conventional scanning tunneling microscopy. Scanning techniques based on electrostatic coupling to the 2DES deliver important insights, but generally with resolution limited by the depth of the 2DES. In this letter, we present our progress in developing a technique called “virtual scanning tunneling microscopy” that allows local tunneling into a high mobility 2DES. Using a specially designed bilayer GaAs/AlGaAs heterostructure where the tunnel coupling between two separate 2DESs is tunable via electrostatic gating, combined with a scanning gate, we show that the local tunneling can be controlled with sub-250 nm resolution.

  16. Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Xue, Jiamin; Sanchez-Yamagishi, Javier; Bulmash, Danny; Jacquod, Philippe; Deshpande, Aparna; Watanabe, K.; Taniguchi, T.; Jarillo-Herrero, Pablo; Leroy, Brian J.

    2011-04-01

    Graphene has demonstrated great promise for future electronics technology as well as fundamental physics applications because of its linear energy-momentum dispersion relations which cross at the Dirac point. However, accessing the physics of the low-density region at the Dirac point has been difficult because of disorder that leaves the graphene with local microscopic electron and hole puddles. Efforts have been made to reduce the disorder by suspending graphene, leading to fabrication challenges and delicate devices which make local spectroscopic measurements difficult. Recently, it has been shown that placing graphene on hexagonal boron nitride (hBN) yields improved device performance. Here we use scanning tunnelling microscopy to show that graphene conforms to hBN, as evidenced by the presence of Moiré patterns. However, contrary to predictions, this conformation does not lead to a sizeable band gap because of the misalignment of the lattices. Moreover, local spectroscopy measurements demonstrate that the electron-hole charge fluctuations are reduced by two orders of magnitude as compared with those on silicon oxide. This leads to charge fluctuations that are as small as in suspended graphene, opening up Dirac point physics to more diverse experiments.

  17. Scanning tunnelling microscopy and spectroscopy of ultra-flat graphene on hexagonal boron nitride.

    PubMed

    Xue, Jiamin; Sanchez-Yamagishi, Javier; Bulmash, Danny; Jacquod, Philippe; Deshpande, Aparna; Watanabe, K; Taniguchi, T; Jarillo-Herrero, Pablo; LeRoy, Brian J

    2011-04-01

    Graphene has demonstrated great promise for future electronics technology as well as fundamental physics applications because of its linear energy-momentum dispersion relations which cross at the Dirac point. However, accessing the physics of the low-density region at the Dirac point has been difficult because of disorder that leaves the graphene with local microscopic electron and hole puddles. Efforts have been made to reduce the disorder by suspending graphene, leading to fabrication challenges and delicate devices which make local spectroscopic measurements difficult. Recently, it has been shown that placing graphene on hexagonal boron nitride (hBN) yields improved device performance. Here we use scanning tunnelling microscopy to show that graphene conforms to hBN, as evidenced by the presence of Moiré patterns. However, contrary to predictions, this conformation does not lead to a sizeable band gap because of the misalignment of the lattices. Moreover, local spectroscopy measurements demonstrate that the electron-hole charge fluctuations are reduced by two orders of magnitude as compared with those on silicon oxide. This leads to charge fluctuations that are as small as in suspended graphene, opening up Dirac point physics to more diverse experiments.

  18. Scanning Tunneling Microscopy Studies of Crystalline Hydrogenation of Graphene Grown on Cu(111)

    NASA Astrophysics Data System (ADS)

    Tjung, Steven J.; Gambrel, Grady A.; Hollen, Shawna M.; Gupta, Jay A.

    Because of the sensitivity of 2D material surfaces, chemical functionalization can be exploited to tune the electronic structure of these materials. For example, hydrogen bonding to carbon atoms in graphene tunes the material from a semi-metal to a wide-gap insulator. We developed a method for a reproducible epitaxial growth of graphene on Cu(111) in the ultra-high vacuum chamber of a scanning tunneling microscope (STM). We find that hydrogen atoms can be bonded to the graphene in a nanoscale region using a novel field-emission process, whereby physisorbed H2 is cracked in situ using the STM tip. This method produced crystalline surfaces of hydrogen-terminated graphene with 4.2Å lattice, which has proven difficult to produce using conventional atomic beam methods which typically produced disordered hydrogenation. Additionally, this hydrogenation process is reversible and we are able to recover the pristine graphene by H desorption during STM imaging at a high bias. STM images after the dehydrogenation process showed the same atomic lattice and Moiré pattern as the pristine graphene, with the exception of additional point defects. STM spectra show the suppression of the Cu surface state on the hydrogenated graphene, but the opening of a wide-gap was not observed. Funded by the Center for Emergent Materials at the Ohio State University, an NSF MRSEC (Grant No. DMR-1420451 and DMR-0820414).

  19. Scanning Tunneling Microscopy of the π Magnetism of a Single Carbon Vacancy in Graphene.

    PubMed

    Zhang, Yu; Li, Si-Yu; Huang, Huaqing; Li, Wen-Tian; Qiao, Jia-Bin; Wang, Wen-Xiao; Yin, Long-Jing; Bai, Ke-Ke; Duan, Wenhui; He, Lin

    2016-10-14

    Pristine graphene is strongly diamagnetic. However, graphene with single carbon atom defects could exhibit paramagnetism. Theoretically, the π magnetism induced by the monovacancy in graphene is characteristic of two spin-split density-of-states (DOS) peaks close to the Dirac point. Since its prediction, many experiments have attempted to study this π magnetism in graphene, whereas only a notable resonance peak has been observed around the atomic defects, leaving the π magnetism experimentally elusive. Here, we report direct experimental evidence of π magnetism by using a scanning tunneling microscope. We demonstrate that the localized state of the atomic defects is split into two DOS peaks with energy separations of several tens of meV. Strong magnetic fields further increase the energy separations of the two spin-polarized peaks and lead to a Zeeman-like splitting. Unexpectedly, the effective g factor around the atomic defect is measured to be about 40, which is about 20 times larger than the g factor for electron spins.

  20. Hand Controlled Manipulation of Single Molecules via a Scanning Probe Microscope with a 3D Virtual Reality Interface.

    PubMed

    Leinen, Philipp; Green, Matthew F B; Esat, Taner; Wagner, Christian; Tautz, F Stefan; Temirov, Ruslan

    2016-10-02

    Considering organic molecules as the functional building blocks of future nanoscale technology, the question of how to arrange and assemble such building blocks in a bottom-up approach is still open. The scanning probe microscope (SPM) could be a tool of choice; however, SPM-based manipulation was until recently limited to two dimensions (2D). Binding the SPM tip to a molecule at a well-defined position opens an opportunity of controlled manipulation in 3D space. Unfortunately, 3D manipulation is largely incompatible with the typical 2D-paradigm of viewing and generating SPM data on a computer. For intuitive and efficient manipulation we therefore couple a low-temperature non-contact atomic force/scanning tunneling microscope (LT NC-AFM/STM) to a motion capture system and fully immersive virtual reality goggles. This setup permits "hand controlled manipulation" (HCM), in which the SPM tip is moved according to the motion of the experimenter's hand, while the tip trajectories as well as the response of the SPM junction are visualized in 3D. HCM paves the way to the development of complex manipulation protocols, potentially leading to a better fundamental understanding of nanoscale interactions acting between molecules on surfaces. Here we describe the setup and the steps needed to achieve successful hand-controlled molecular manipulation within the virtual reality environment.

  1. Nanoelectrical probing with multiprobe SPM Systems compatible with scanning electron microscopes

    NASA Astrophysics Data System (ADS)

    Lewis, Aaron; Ignatov, Andrey; Taha, Hesham; Zhinoviev, Oleg; Komissar, Anatoly; Krol, Alexander; Lewis, David

    2011-03-01

    A scanning electron microscope compatible platform that permits multiprobe atomic force microscopy based nanoelectrical characterization will be described. To achieve such multiple parameter nanocharacterization with scanning electron microscope compatibility involves a number of innovations both in instrument and probe design. This presentation will focus on how these advances were achieved and the results obtained with such instrumentation on electrical nano-characterization and electrical nano-manipulation. The advances include: 1. Specialized scanners; 2. An ultrasensitive feedback mechanism based on tuning forks with no optical feedback interference that can induce carriers in semiconductor devices; and 3. Unique probes compatible with multiprobe geometries in which the probe tips can be brought into physical contact with one another. Experiments will be described with such systems that will include multiprobe electrical measurements with metal and glass coated coaxial nanowires of platinum. This combination of scanning electron microscopes integrated with multiprobe instrumentation allows for important applications not available today in the field of semiconductor processing technology.

  2. A new apparatus for electron tomography in the scanning electron microscope

    SciTech Connect

    Morandi, V. Maccagnani, P.; Masini, L.; Migliori, A.; Ortolani, L.; Pezza, A.; Del Marro, M.; Pallocca, G.; Vinciguerra, P.; Rossi, M.; Ferroni, M.; Sberveglieri, G.; Vittori-Antisari, M.

    2015-06-23

    The three-dimensional reconstruction of a microscopic specimen has been obtained by applying the tomographic algorithm to a set of images acquired in a Scanning Electron Microscope. This result was achieved starting from a series of projections obtained by stepwise rotating the sample under the beam raster. The Scanning Electron Microscope was operated in the scanning-transmission imaging mode, where the intensity of the transmitted electron beam is a monotonic function of the local mass-density and thickness of the specimen. The detection strategy has been implemented and tailored in order to maintain the projection requirement over the large tilt range, as required by the tomographic workflow. A Si-based electron detector and an eucentric-rotation specimen holder have been specifically developed for the purpose.

  3. Response function and optimum configuration of semiconductor backscattered-electron detectors for scanning electron microscopes

    SciTech Connect

    Rau, E. I.; Orlikovskiy, N. A.; Ivanova, E. S.

    2012-06-15

    A new highly efficient design for semiconductor detectors of intermediate-energy electrons (1-50 keV) for application in scanning electron microscopes is proposed. Calculations of the response function of advanced detectors and control experiments show that the efficiency of the developed devices increases on average twofold, which is a significant positive factor in the operation of modern electron microscopes in the mode of low currents and at low primary electron energies.

  4. System design and new applications for atomic force microscope based on tunneling

    NASA Astrophysics Data System (ADS)

    Wang, X.; Liu, A. P.; Yang, X. H.

    2015-09-01

    The design of atomic force microscopy (AFM) with high resolution is introduced in this paper. Mainly, we have developed the system design of the apparatus based on tunneling. AFM.IPC-208B, this kind of apparatus combines scanning tunnel microscopy (STM) and AFM availability, and its lens body with original frame enhances the capability of the machine. In order to analyze the performance of AFM.IPC-208B, as a new tool in the field of Life Science, we make use of the system to study natural mica and molecular protein structures of Cattle-insulin and human antibody immunoglobulin G (IgG) coupled with staphylococcus protein A (SPA). As the results of new applications, the resolution of AFM.IPC-208B is proved to be 0.1 nm, and these nanometer measurement results provide much valuable information for the study of small molecular proteins and HIV experiments.

  5. Mirror Buckling Transitions in Freestanding Graphene Membranes Induced through Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Schoelz, James K.

    Graphene has the ability to provide for a technological revolution. First isolated and characterized in 2004, this material shows promise in the field of flexible electronics. The electronic properties of graphene can be tuned by controlling the shape of the membrane. Of particular interest in this endeavor are the thermal ripples in graphene membranes. Years of theoretical work by such luminaries as Lev Landau, Rudolf Peierls, David Mermin and Herbert Wagner have established that 2D crystals should not be thermodynamically stable. Experimental research on thin films has supported this finding. Yet graphene exists, and freestanding graphene films have been grown on large scales. It turns out that coupling between the bending and stretching phonons can stabilize the graphene in a flat, albeit rippled phase. These ripples have attracted much attention, and recent work has shown how to arrange these ripples in a variety of configurations. In this thesis, I will present work done using a scanning tunneling microscope (STM) to interact with freestanding graphene membranes. First I will present STM images of freestanding graphene and show how these images show signs of distortion under the electrostatic influence of the STM tip. This electrostatic attraction between the STM tip and the graphene sample can be used to pull on the graphene sample. At the same time, by employing Joule heating in order to heat graphene using the tunneling current, and exploiting the negative coefficient of thermal expansion, a repulsive thermal load can be generated. By repeatedly pulling on the graphene using the electrostatic potential, while sequentially increasing the setpoint current we can generate a thermal mirror buckling event. Slowly heating the graphene using the tunneling current, prepares a small convex region of graphene under the tip. By increasing thermal stress, as well as pulling using the out of plane electrostatic force, the graphene suddenly and irreversibly switches the

  6. Three-dimensional microscope vision system based on micro laser line scanning and adaptive genetic algorithms

    NASA Astrophysics Data System (ADS)

    Apolinar, J.; Rodríguez, Muñoz

    2017-02-01

    A microscope vision system to retrieve small metallic surface via micro laser line scanning and genetic algorithms is presented. In this technique, a 36 μm laser line is projected on the metallic surface through a laser diode head, which is placed to a small distance away from the target. The micro laser line is captured by a CCD camera, which is attached to the microscope. The surface topography is computed by triangulation by means of the line position and microscope vision parameters. The calibration of the microscope vision system is carried out by an adaptive genetic algorithm based on the line position. In this algorithm, an objective function is constructed from the microscope geometry to determine the microscope vision parameters. Also, the genetic algorithm provides the search space to calculate the microscope vision parameters with high accuracy in fast form. This procedure avoids errors produced by the missing of references and physical measurements, which are employed by the traditional microscope vision systems. The contribution of the proposed system is corroborated by an evaluation via accuracy and speed of the traditional microscope vision systems, which retrieve micro-scale surface topography.

  7. Imaging properties and its improvements of scanning/imaging x-ray microscope

    SciTech Connect

    Takeuchi, Akihisa Uesugi, Kentaro; Suzuki, Yoshio

    2016-01-28

    A scanning / imaging X-ray microscope (SIXM) system has been developed at SPring-8. The SIXM consists of a scanning X-ray microscope with a one-dimensional (1D) X-ray focusing device and an imaging (full-field) X-ray microscope with a 1D X-ray objective. The motivation of the SIXM system is to realize a quantitative and highly-sensitive multimodal 3D X-ray tomography by taking advantages of both the scanning X-ray microscope using multi-pixel detector and the imaging X-ray microscope. Data acquisition process of a 2D image is completely different between in the horizontal direction and in the vertical direction; a 1D signal is obtained with the linear-scanning while the other dimensional signal is obtained with the imaging optics. Such condition have caused a serious problem on the imaging properties that the imaging quality in the vertical direction has been much worse than that in the horizontal direction. In this paper, two approaches to solve this problem will be presented. One is introducing a Fourier transform method for phase retrieval from one phase derivative image, and the other to develop and employ a 1D diffuser to produce an asymmetrical coherent illumination.

  8. Efficient electrochemical etching method to fabricate sharp metallic tips for scanning probe microscopes

    SciTech Connect

    Kim, Pilkyu; Kim, Jun Ho; Jeong, Mun Seok; Ko, Do-Kyeong; Lee, Jongmin; Jeong, Sungho

    2006-10-15

    A new technique based on electrochemical etching for the fabrication of sharp metallic tips for scanning probe microscopes is introduced. In the proposed method, a small Teflon mass is attached to the end of an immersed tungsten wire using an aluminum tape, which leads to a significant enhancement of yield rate of sharp tungsten tips with an apex size below 100 nm to over 60%. The functionality of the tungsten tips fabricated by the proposed method is verified by measuring the topography of a standard sample using a shear-force scanning probe microscope.

  9. Functional group-selective adsorption using scanning tunneling microscopy.

    PubMed

    Min, Young Hwan; Park, Eun Hee; Kim, Do Hwan; Kim, Sehun

    2012-04-24

    In this study, we selectively enhanced two types of adsorption of 3-mercaptoisobutyric acid on a Ge(100) surface by using the tunneling electrons from an STM and the catalytic effect of an STM tip. 3-Mercaptoisobutyric acid has two functional groups: a carboxylic acid group at one end of the molecule and a thiol group at the other end. It was found that the adsorption occurring through the carboxylic acid group was selectively enhanced by the application of electrons tunneling between an STM tip and the surface. Using this enhancement, it was possible to make thiol group-terminated surfaces at any desired location. In addition, via the use of a tungsten STM tip coated with a tungsten oxide (WO(3)) layer, we selectively catalyzed the adsorption through the thiol group. Using this catalysis, it was possible to generate carboxylic acid group-terminated surfaces at any desired location. This functional group-selective adsorption using STM could be applied in positive lithographic methods to produce semiconductor substrates terminated by desired functional groups.

  10. Insulated gold scanning tunneling microscopy probes for recognition tunneling in an aqueous environment.

    PubMed

    Tuchband, Michael; He, Jin; Huang, Shuo; Lindsay, Stuart

    2012-01-01

    Chemically functionalized probes are required for tunneling measurements made via chemical contacts ("Recognition Tunneling"). Here, we describe the etching of gold STM probes suitable for chemical functionalization with moieties bearing thiol groups. Insulated with high density polyethylene, these probes may be used in aqueous electrolytes with sub pA leakage currents. The area of the exposed probe surface was characterized via the saturation current in an electroactive solution (0.1 M K(3)Fe(CN)(6)). Twenty five percent of the probes had an exposed region of 10 nm radius or less.

  11. Fabrication and scanning tunneling microscopy characterization of suspended monolayer graphene on periodic Si nanopillars

    NASA Astrophysics Data System (ADS)

    Zhao, Xin; Zhai, Xiaofang; Zhao, Aidi; Wang, Bing; Hou, J. G.

    2013-05-01

    We present the fabrication and scanning tunneling microscopy (STM) characterization of suspended monolayer graphene (SMG) on periodic Si nanostructure. Monolayer graphene (MG) was grown on Cu foils by chemical vapor deposition (CVD) and transferred onto a Si substrate with etched array of periodic nanopillars, obtaining partly suspended MG. Low-temperature STM characterization was performed on the suspension area of the MG with atomic resolution images obtained. The scanning tunneling spectroscopy of SMG shows a nonlinear behavior near the Fermi level (EF), which is attributed to the Dirac cone reshaped by electron-electron interaction.

  12. High-resolution, high-throughput imaging with a multibeam scanning electron microscope

    PubMed Central

    EBERLE, AL; MIKULA, S; SCHALEK, R; LICHTMAN, J; TATE, ML KNOTHE; ZEIDLER, D

    2015-01-01

    Electron–electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers. Lay Description The composition of our world and our bodies on the very small scale has always fascinated people, making them search for ways to make this visible to the human eye. Where light microscopes reach their resolution limit at a certain magnification, electron microscopes can go beyond. But their capability of visualizing extremely small features comes at the cost of a very small field of view. Some of the questions researchers seek to answer today deal with the ultrafine structure of brains, bones or computer chips. Capturing these objects with electron microscopes takes a lot of time – maybe even exceeding the time span of a human being – or new tools that do the job much faster. A new type of scanning electron microscope scans with 61 electron beams in parallel, acquiring 61 adjacent images of the sample at the same time a conventional scanning electron microscope captures one of these images. In principle, the multibeam scanning electron microscope’s field of view is 61 times larger and therefore coverage of the sample surface can be accomplished in less time. This enables researchers to think about large-scale projects, for example in the rather new field of connectomics. A very good introduction to imaging a brain at nanometre resolution can be found within course material from Harvard University on http://www.mcb80x.org/# as featured media entitled ‘connectomics’. PMID:25627873

  13. Masked illumination scheme for a galvanometer scanning high-speed confocal fluorescence microscope.

    PubMed

    Kim, Dong Uk; Moon, Sucbei; Song, Hoseong; Kwon, Hyuk-Sang; Kim, Dug Young

    2011-01-01

    High-speed beam scanning and data acquisition in a laser scanning confocal microscope system are normally implemented with a resonant galvanometer scanner and a frame grabber. However, the nonlinear scanning speed of a resonant galvanometer can generate nonuniform photobleaching in a fluorescence sample as well as image distortion near the edges of a galvanometer scanned fluorescence image. Besides, incompatibility of signal format between a frame grabber and a point detector can lead to digitization error during data acquisition. In this article, we introduce a masked illumination scheme which can effectively decrease drawbacks in fluorescence images taken by a laser scanning confocal microscope with a resonant galvanometer and a frame grabber. We have demonstrated that the difference of photobleaching between the center and the edge of a fluorescence image can be reduced from 26 to 5% in our confocal laser scanning microscope with a square illumination mask. Another advantage of our masked illumination scheme is that the zero level or the lowest input level of an analog signal in a frame grabber can be accurately set by the dark area of a mask in our masked illumination scheme. We have experimentally demonstrated the advantages of our masked illumination method in detail.

  14. Three-Dimensional Laser Scanning for Geometry Documentation and Construction Management of Highway Tunnels during Excavation

    PubMed Central

    Gikas, Vassilis

    2012-01-01

    Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered. PMID:23112655

  15. Three-dimensional laser scanning for geometry documentation and construction management of highway tunnels during excavation.

    PubMed

    Gikas, Vassilis

    2012-01-01

    Driven by progress in sensor technology, computer software and data processing capabilities, terrestrial laser scanning has recently proved a revolutionary technique for high accuracy, 3D mapping and documentation of physical scenarios and man-made structures. Particularly, this is of great importance in the underground space and tunnel construction environment as surveying engineering operations have a great impact on both technical and economic aspects of a project. This paper discusses the use and explores the potential of laser scanning technology to accurately track excavation and construction activities of highway tunnels. It provides a detailed overview of the static laser scanning method, its principles of operation and applications for tunnel construction operations. Also, it discusses the planning, execution, data processing and analysis phases of laser scanning activities, with emphasis given on geo-referencing, mesh model generation and cross-section extraction. Specific case studies are considered based on two construction sites in Greece. Particularly, the potential of the method is examined for checking the tunnel profile, producing volume computations and validating the smoothness/thickness of shotcrete layers at an excavation stage and during the completion of excavation support and primary lining. An additional example of the use of the method in the geometric documentation of the concrete lining formwork is examined and comparisons against dimensional tolerances are examined. Experimental comparisons and analyses of the laser scanning method against conventional surveying techniques are also considered.

  16. A Mythical History of the Scanning Probe Microscope - How it Could Have Been

    NASA Astrophysics Data System (ADS)

    Elings, Virgil

    2007-03-01

    The path from the ground breaking Topografiner by Young et. al. in 1972 to the current Atomic Force Microscopes was tortuous, to say the least. Now as an entrepreneur, they say that you should study the problem, work out a plan, and then execute the plan. Since this rarely works for me in real life, let's follow the mythical history of Phil the physics student whose simple approach to scanning probe microscopes during his summer job may explain life better than real life did. Comparisons between Phil's experience and real life will be made along the way to show how random real life was compared to Phil's straightforward approach. We will follow Phil as he goes from the Scanning Touching Microscope (STM) to the All Fancy Microscope (AFM) and ends up with a current scanning probe microscope. The ``lesson'' in this story is that when you are doing something new, you learn so much while you are doing it that what you thought at the beginning (the plan) is rarely the best way to go. It is more important, I believe, for entrepreneurs to explore possibilities and keep their eyes open along the way rather than pretend the path they are on is the right one. Phil is mythical because he always knew where he was headed and it was always the right direction. So how does Phil's story end? I'm working on it and will tell you at the March Meeting.

  17. Scanning electron microscope view of iron crystal growing on pyroxene crystal

    NASA Technical Reports Server (NTRS)

    1972-01-01

    A scanning electron microscope photograph of a four-micron size iron crystal growing on a pyroxene crystal (calcium-magnesium-iron silicate) from the Apollo 15 Hadley-Apennino lunar landing site. The well developed crystal faces indicate that the crystal was formed from a hot vapor as the rock was cooling.

  18. Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

    NASA Astrophysics Data System (ADS)

    Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao

    2016-01-01

    Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke's tabulated data.

  19. High-resolution, high-throughput imaging with a multibeam scanning electron microscope.

    PubMed

    Eberle, A L; Mikula, S; Schalek, R; Lichtman, J; Knothe Tate, M L; Zeidler, D

    2015-08-01

    Electron-electron interactions and detector bandwidth limit the maximal imaging speed of single-beam scanning electron microscopes. We use multiple electron beams in a single column and detect secondary electrons in parallel to increase the imaging speed by close to two orders of magnitude and demonstrate imaging for a variety of samples ranging from biological brain tissue to semiconductor wafers.

  20. Scanning electron microscopic study of an anterior chamber intraocular lens: latent endophthalmitis.

    PubMed

    Schémann, J F

    1987-01-01

    Two years after intracapsular cataract extraction and intraocular lens implantation, an anterior chamber lens was removed. The lens was studied by scanning electron microscope which demonstrated the presence of colonies of cocci, a thin acellular membrane covering part of the lens and some modifications of the lens surface.

  1. Quantitative phase tomography by using x-ray microscope with Foucault knife-edge scanning filter

    SciTech Connect

    Watanabe, Norio; Tsuburaya, Yuji; Shimada, Akihiro; Aoki, Sadao

    2016-01-28

    Quantitative phase tomography was evaluated by using a differential phase microscope with a Foucault knife-edge scanning filter. A 3D x-ray phase image of polystyrene beads was obtained at 5.4 keV. The reconstructed refractive index was fairly good agreement with the Henke’s tabulated data.

  2. Quantitative Phase Imaging with a Scanning Transmission X-Ray Microscope

    PubMed Central

    de Jonge, M. D.; Hornberger, B.; Holzner, C.; Legnini, D.; Paterson, D.; McNulty, I.; Jacobsen, C.; Vogt, S.

    2010-01-01

    We obtain quantitative phase reconstructions from differential phase contrast images obtained with a scanning transmission x-ray microscope and 2.5 keV x rays. The theoretical basis of the technique is presented along with measurements and their interpretation. PMID:18518198

  3. High spatial resolution confocal microscope with independent excitation and detection scanning capabilities.

    PubMed

    Marcet, S; Ouellet-Plamondon, C; Francoeur, S

    2009-06-01

    We present the design of a confocal microscope adapted for optical spectroscopy and imaging at cryogenic temperatures. This system is based on the existing approach of partly inserting the optical components of the microscope inside a helium-bath cryostat. It provides a spatial resolution approaching the diffraction limit with a mechanical stability allowing uninterrupted integration times exceeding 10 h and allows keeping track of a single emitter for unlimited periods of time. Furthermore, our design allows scanning the excitation spot and detection area independently of the sample position. This feature provides the means to perform probeless transport experiments on one-dimensional nanostructures. The scanning capabilities of this microscope are fully detailed and characterized using the photoluminescence of single nitrogen dyads at 4.5 K.

  4. Simultaneously measured signals in scanning probe microscopy with a needle sensor: Frequency shift and tunneling current

    NASA Astrophysics Data System (ADS)

    Morawski, Ireneusz; Voigtländer, Bert

    2010-03-01

    We present combined noncontact scanning force microscopy and tunneling current images of a platinum(111) surface obtained by means of a 1 MHz quartz needle sensor. The low-frequency circuit of the tunneling current was combined with a high-frequency signal of the quartz resonator enabling full electrical operation of the sensor. The frequency shift and the tunneling current were detected simultaneously, while the feedback control loop of the topography signal was fed using one of them. In both cases, the free signal that was not connected to the feedback loop reveals proportional-integral controller errorlike behavior, which is governed by the time derivative of the topography signal. A procedure is proposed for determining the mechanical oscillation amplitude by utilizing the tunneling current also including the average tip-sample work function.

  5. Fixing the energy scale in scanning tunneling microscopy on semiconductor surfaces.

    PubMed

    Münnich, Gerhard; Donarini, Andrea; Wenderoth, Martin; Repp, Jascha

    2013-11-22

    In scanning tunneling experiments on semiconductor surfaces, the energy scale within the tunneling junction is usually unknown due to tip-induced band bending. Here, we experimentally recover the zero point of the energy scale by combining scanning tunneling microscopy with Kelvin probe force spectroscopy. With this technique, we revisit shallow acceptors buried in GaAs. Enhanced acceptor-related conductance is observed in negative, zero, and positive band-bending regimes. An Anderson-Hubbard model is used to rationalize our findings, capturing the crossover between the acceptor state being part of an impurity band for zero band bending and the acceptor state being split off and localized for strong negative or positive band bending, respectively.

  6. A scanning Hall probe microscope for high resolution, large area, variable height magnetic field imaging

    NASA Astrophysics Data System (ADS)

    Shaw, Gorky; Kramer, R. B. G.; Dempsey, N. M.; Hasselbach, K.

    2016-11-01

    We present a scanning Hall probe microscope operating in ambient conditions. One of the unique features of this microscope is the use of the same stepper motors for both sample positioning as well as scanning, which makes it possible to have a large scan range (few mm) in the x and y directions, with a scan resolution of 0.1 μm. Protocols have been implemented to enable scanning at different heights from the sample surface. The z range is 35 mm. Microstructured Hall probes of size 1-5 μm have been developed. A minimum probe-sample distance <2 μm has been obtained by the combination of new Hall probes and probe-sample distance regulation using a tuning fork based force detection technique. The system is also capable of recording local B(z) profiles. We discuss the application of the microscope for the study of micro-magnet arrays being developed for applications in micro-systems.

  7. Confocal Laser Microscope Scanning Applied To Three-Dimensional Studies Of Biological Specimens.

    NASA Astrophysics Data System (ADS)

    Franksson, Olof; Liljeborg, Anders; Carlsson, Kjell; Forsgren, Per-Ola

    1987-08-01

    The depth-discriminating property of confocal laser microscope scanners can be used to record the three-dimensional structure of specimens. A number of thin sections (approx. 1 μm thick) can be recorded by a repeated process of image scanning and refocusing of the microscope. We have used a confocal microscope scanner in a number of feasibility studies to investigate its possibilities and limitations. It has proved to be well suited for examining fluorescent specimens with a complicated three-dimensional structure, such as nerve cells. It has also been used to study orchid seeds, as well as cell colonies, greatly facilitating evaluation of such specimens. Scanning of the specimens is performed by a focused laser beam that is deflected by rotating mirrors, and the reflected or fluorescent light from the specimen is detected. The specimen thus remains stationary during image scanning, and is only moved stepwise in the vertical direction for refocusing between successive sections. The scanned images consist of 256*256 or 512*512 pixels, each pixel containing 8 bits of data. After a scanning session a large number of digital images, representing consecutive sections of the specimen, are stored on a disk memory. In a typical case 200 such 256*256 images are stored. To display and process this information in a meaningful way requires both appropriate software and a powerful computer. The computer used is a 32-bits minicomputer equipped with an array processor (FPS 100). The necessary software was developed at our department.

  8. Electronic properties of graphene: a perspective from scanning tunneling microscopy and magnetotransport.

    PubMed

    Andrei, Eva Y; Li, Guohong; Du, Xu

    2012-05-01

    This review covers recent experimental progress in probing the electronic properties of graphene and how they are influenced by various substrates, by the presence of a magnetic field and by the proximity to a superconductor. The focus is on results obtained using scanning tunneling microscopy, spectroscopy, transport and magnetotransport techniques.

  9. Process dependent morphology of the Si/SiO2 interface measured with scanning tunneling microscopy

    NASA Technical Reports Server (NTRS)

    Hecht, Michael H.; Bell, L. D.; Grunthaner, F. J.; Kaiser, W. J.

    1988-01-01

    A new experimental technique to determine Si/SiO2 interface morphology is described. Thermal oxides of silicon are chemically removed, and the resulting surface topography is measured with scanning tunneling microscopy. Interfaces prepared by oxidation of Si (100) and (111) surfaces, followed by postoxidation anneal (POA) at different temperatures, have been characterized. Correlations between interface structure, chemistry, and electrical characteristics are described.

  10. Four-Wave Mixing And Scanning Tunneling Microscopy Of Semiconductor Clusters

    NASA Astrophysics Data System (ADS)

    Sarid, Dror; McGinnis, B. P.; Henson, Tammy D.

    1988-05-01

    Semiconductor structures in lower dimensions, dubbed quantum dots, exhibit novel properties which result from size quantization of their charge carriers, as well as from their large surface-to-volume ratio. Optical measurements, combined with scanning tunneling microscopy, can provide the detailed information required to model the nonlinear optical response of these clusters.

  11. Preparation of Chemically Etched Tips for Ambient Instructional Scanning Tunneling Microscopy

    ERIC Educational Resources Information Center

    Zaccardi, Margot J.; Winkelmann, Kurt; Olson, Joel A.

    2010-01-01

    A first-year laboratory experiment that utilizes concepts of electrochemical tip etching for scanning tunneling microscopy (STM) is described. This experiment can be used in conjunction with any STM experiment. Students electrochemically etch gold STM tips using a time-efficient method, which can then be used in an instructional grade STM that…

  12. Evaluation of Enterococcus faecalis adhesion, penetration, and method to prevent the penetration of Enterococcus faecalis into root cementum: Confocal laser scanning microscope and scanning electron microscope analysis

    PubMed Central

    Halkai, Rahul S.; Hegde, Mithra N.; Halkai, Kiran R.

    2016-01-01

    Aim: To ascertain the role of Enterococcus faecalis in persistent infection and a possible method to prevent the penetration of E. faecalis into root cementum. Methodology: One hundred and twenty human single-rooted extracted teeth divided into five groups. Group I (control): intact teeth, Group II: no apical treatment done, Group III divided into two subgroups. In Groups IIIa and IIIb, root apex treated with lactic acid of acidic and neutral pH, respectively. Group IV: apical root cementum exposed to lactic acid and roughened to mimic the apical resorption. Group V: apical treatment done same as Group IV and root-end filling done using mineral trioxide aggregate (MTA). Apical one-third of all samples immersed in E. faecalis broth for 8 weeks followed by bone morphogenetic protein and obturation and again immersed into broth for 8 weeks. Teeth split into two halves and observed under confocal laser scanning microscope and scanning electron microscope, organism identified by culture and polymerase chain reaction techniques. Results: Adhesion and penetration was observed in Group IIIa and Group IV. Only adhesion in Group II and IIIB and no adhesion and penetration in Group I and V. Conclusion: Adhesion and penetration of E. faecalis into root cementum providing a long-term nidus for subsequent infection are the possible reason for persistent infection and root-end filling with MTA prevents the adhesion and penetration. PMID:27994316

  13. Characterization of grain boundary conductivity of spin-sprayed ferrites using scanning microwave microscope

    SciTech Connect

    Myers, J.; Nicodemus, T.; Zhuang, Y.; Watanabe, T.; Matsushita, N.; Yamaguchi, M.

    2014-05-07

    Grain boundary electrical conductivity of ferrite materials has been characterized using scanning microwave microscope. Structural, electrical, and magnetic properties of Fe{sub 3}O{sub 4} spin-sprayed thin films onto glass substrates for different length of growth times were investigated using a scanning microwave microscope, an atomic force microscope, a four-point probe measurement, and a made in house transmission line based magnetic permeameter. The real part of the magnetic permeability shows almost constant between 10 and 300 MHz. As the Fe{sub 3}O{sub 4} film thickness increases, the grain size becomes larger, leading to a higher DC conductivity. However, the loss in the Fe{sub 3}O{sub 4} films at high frequency does not increase correspondingly. By measuring the reflection coefficient s{sub 11} from the scanning microwave microscope, it turns out that the grain boundaries of the Fe{sub 3}O{sub 4} films exhibit higher electric conductivity than the grains, which contributes loss at radio frequencies. This result will provide guidance for further improvement of low loss ferrite materials for high frequency applications.

  14. Phase-gradient contrast in thick tissue with a scanning microscope

    PubMed Central

    Mertz, J.; Gasecka, A.; Daradich, A.; Davison, I.; Coté, D.

    2014-01-01

    It is well known that the principle of reciprocity is valid for light traveling even through scattering or absorptive media. This principle has been used to establish an equivalence between conventional widefield microscopes and scanning microscopes. We make use of this principle to introduce a scanning version of oblique back-illumination microscopy, or sOBM. This technique provides sub-surface phase-gradient and amplitude images from unlabeled tissue, in an epi-detection geometry. That is, it may be applied to arbitrarily thick tissue. sOBM may be implemented as a simple, cost-effective add-on with any scanning microscope, requiring only the availability of an extra input channel in the microscope electronics. We demonstrate here its implementation in combination with two-photon excited fluorescence (TPEF) microscopy and with coherent anti-Stokes Raman scattering (CARS) microscopy, applied to brain or spinal cord tissue imaging. In both cases, sOBM provides information on tissue morphology complementary to TPEF or CARS contrast. This information is obtained simultaneously and is automatically co-registered. Finally, we show that sOBM can be operated at video rate. PMID:24575336

  15. Characterization of grain boundary conductivity of spin-sprayed ferrites using scanning microwave microscope

    NASA Astrophysics Data System (ADS)

    Myers, J.; Nicodemus, T.; Zhuang, Y.; Watanabe, T.; Matsushita, N.; Yamaguchi, M.

    2014-05-01

    Grain boundary electrical conductivity of ferrite materials has been characterized using scanning microwave microscope. Structural, electrical, and magnetic properties of Fe3O4 spin-sprayed thin films onto glass substrates for different length of growth times were investigated using a scanning microwave microscope, an atomic force microscope, a four-point probe measurement, and a made in house transmission line based magnetic permeameter. The real part of the magnetic permeability shows almost constant between 10 and 300 MHz. As the Fe3O4 film thickness increases, the grain size becomes larger, leading to a higher DC conductivity. However, the loss in the Fe3O4 films at high frequency does not increase correspondingly. By measuring the reflection coefficient s11 from the scanning microwave microscope, it turns out that the grain boundaries of the Fe3O4 films exhibit higher electric conductivity than the grains, which contributes loss at radio frequencies. This result will provide guidance for further improvement of low loss ferrite materials for high frequency applications.

  16. High-Resolution Scanning Tunneling Microscopy of Fully Hydrated Ripple-Phase Bilayers

    PubMed Central

    Woodward IV, J. T.; Zasadzinski, J. A.

    1997-01-01

    A modified freeze-fracture replication technique for use with the scanning tunneling microscope (STM) has provided a quantitative, high-resolution description of the waveform and amplitude of rippled bilayers in the Pβ, phase of dimyristoylphosphatidylcholine (DMPC) in excess water. The ripples are uniaxial and asymmetrical, with a temperature-dependent amplitude of 2.4 nm near the chain melting temperature that decreases to zero at the chain crystallization temperature. The wavelength of 11 nm does not change with temperature. The observed ripple shape and the temperature-induced structural changes are not predicted by any current theory. Calibration and reproducibility of the STM/replica technique were tested with replicas of well-characterized bilayers of cadmium arachidate on mica that provide regular 5.5-nm steps. STM images were analyzed using a cross-correlation averaging program to eliminate the effects of noise and the finite size and shapes of the metal grains that make up the replica. The correlation averaging allowed us to develop a composite ripple profile averaged over hundreds of individual ripples measured on different samples with different STM tips. The STM/replica technique avoids many of the previous artifacts of biological STM imaging and can be used to examine a variety of periodic hydrated lipid and protein samples at a lateral resolution of about 1 nm and a vertical resolution of about 0.3 nm. This resolution is superior to conventional and tapping mode AFM of soft biological materials; the technique is substrate-free, and the conductive and chemically uniform replicas make image interpretation simple and direct. ImagesFIGURE 1FIGURE 2FIGURE 3FIGURE 5 PMID:9017222

  17. Photon scanning-tunneling microscopy of unstained mammalian cells and chromosomes

    SciTech Connect

    Meriaudeau, F.; Goudonnet, J.P.; Carver, E.; Parks, J.E. Jr.; Jacobson, K.B.; Warmack, R.J.; Ferrell, T.L.

    1998-11-01

    The photon scanning-tunneling microscope (PSTM) yields optical topographical images of samples that are thin or that are transparent at the wavelength used. A range of sample sizes can be imaged extending to well below the diffraction limit for sufficiently flat samples. But samples of the order of several to many micrometers in size can be analyzed with less-refined resolution if total internal reflection can be made to occur in the sample. We used the PSTM to examine the optical topography of mouse and human cells and of chromosomes that are unstained. Our objectives were to demonstrate the images as an alternative to conventional microscopy and to provide a sample-preparation methodology that will later permit localized, simultaneous fluorescence or absorption spectroscopy with the signals collected by the probe tip. Furthermore, the PSTM{close_quote}s ability to produce optical profiles in air and in water was tested to establish the basis for future investigation of possible abnormalities in the chromosomes. That is, we considered both physical and biological objectives. To this end we utilized the 442-nm line of a He{endash}Cd laser as well as the 633-nm line from a He{endash}Ne laser, the resulting image quality being tested partly to ascertain the increased effects of scattering at the smaller wavelength. It is shown that adequate resolution and signal-to-noise ratio can be obtained with the shorter wavelength even in the presence of intensity fluctuations from the laser, thus showing that fluorescence and absorption studies can be expected to be practicable. {copyright} 1998 Optical Society of America

  18. Observation of Atomic Steps on Vicinal Si(111) Annealed in Hydrogen Gas Flow by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Kitahara, Kuninori; Ueda, Osamu

    1993-12-01

    The surface of vicinal Si(111) annealed in H2 flow was observed by equipping the chemical vapor deposition chamber with the scanning tunneling microscope. Samples were annealed at 1000°C for 10 min by passing an electric current under the H2 pressure of 7 Torr. Their surface morphology was compared with those annealed in ultrahigh vacuum (UHV) and in N2 flow at the same temperature. We found that the step motion during annealing in H2 was obviously smaller than that for annealing in UHV and N2. The multisteps formed during the annealing in UHV and N2 were not observed for H2 annealing except in the case of heating by direct current in the direction of lower to higher terraces. The mechanism of the interruption of the step motion is discussed from the viewpoint of the interaction between the surface and hydrogen.

  19. Superconducting scanning tunneling microscopy tips in a magnetic field: Geometry-controlled order of the phase transition

    SciTech Connect

    Eltschka, Matthias Jäck, Berthold; Assig, Maximilian; Etzkorn, Markus; Ast, Christian R.; Kondrashov, Oleg V.; Skvortsov, Mikhail A.; Kern, Klaus

    2015-09-21

    The properties of geometrically confined superconductors significantly differ from their bulk counterparts. Here, we demonstrate the geometrical impact for superconducting scanning tunneling microscopy (STM) tips, where the confinement ranges from the atomic to the mesoscopic scale. To this end, we compare the experimentally determined magnetic field dependence for several vanadium tips to microscopic calculations based on the Usadel equation. For our theoretical model of a superconducting cone, we find a direct correlation between the geometry and the order of the superconducting phase transition. Increasing the opening angle of the cone changes the phase transition from first to second order. Comparing our experimental findings to the theory reveals first and second order quantum phase transitions in the vanadium STM tips. In addition, the theory also explains experimentally observed broadening effects by the specific tip geometry.

  20. Atomic-scale studies of nanometer-sized graphene on III-V semiconductors using scanning tunneling microscopy.

    NASA Astrophysics Data System (ADS)

    He, Kevin; Koepke, Justin; Lyding, Joseph

    2009-03-01

    We utilize the Dry Contact Transfer (DCT) method [1] to deposit nanometer-sized, monolayer graphene flakes, in situ, onto cleaved GaAs (110) and InAs (110) surfaces. The flakes were characterized using a homebuilt, room temperature, ultrahigh-vacuum scanning tunneling microscope. We report on the apparent electronic semi-transparency of the monolayer graphene flakes, such that the underlying III-V semiconductor lattice is revealed in our topographic images. This transparency is strongly dependent on the applied sample bias, similar to results seen on SiC (1000) for large sheets of graphene grown via thermal desorption [2]. [3pt] [1] P.M. Albrecht and J.W. Lyding, APL 83, 5029 (2003). [0pt] [2] G.M. Rutter et al, Phys. Rev. B 76, 235416 (2007).

  1. Miniaturized multimodal CARS microscope based on MEMS scanning and a single laser source.

    PubMed

    Murugkar, Sangeeta; Smith, Brett; Srivastava, Prateek; Moica, Adrian; Naji, Majid; Brideau, Craig; Stys, Peter K; Anis, Hanan

    2010-11-08

    We demonstrate a novel miniaturized multimodal coherent anti-Stokes Raman scattering (CARS) microscope based on microelectromechanical systems (MEMS) scanning mirrors and custom miniature optics. A single Ti:sapphire femtosecond pulsed laser is used as the light source to produce the CARS, two photon excitation fluorescence (TPEF) and second harmonic generation (SHG) images using this miniaturized microscope. The high resolution and distortion-free images obtained from various samples such as a USAF target, fluorescent and polystyrene microspheres and biological tissue successfully demonstrate proof of concept, and pave the path towards future integration of parts into a handheld multimodal CARS probe for non- or minimally-invasive in vivo imaging.

  2. Rapid and precise scanning helium ion microscope milling of solid-state nanopores for biomolecule detection

    SciTech Connect

    Yang, Jijin; Ferranti, David C; Stern, Lewis A; Sanford, Colin A; Huang, Jason; Ren, Zheng; Qin, Lu-Chang; Hall, Adam R

    2011-06-10

    We report the formation of solid-state nanopores using a scanning helium ion microscope. The fabrication process offers the advantage of high sample throughput along with fine control over nanopore dimensions, producing single pores with diameters below 4 nm. Electronic noise associated with ion transport through the resultant pores is found to be comparable with levels measured on devices made with the established technique of transmission electron microscope milling. We demonstrate the utility of our nanopores for biomolecular analysis by measuring the passage of double-strand DNA.

  3. Examination of silicon solar cells by means of the Scanning Laser Acoustic Microscope (SLAM)

    NASA Technical Reports Server (NTRS)

    Vorres, C.; Yuhas, D. E.

    1981-01-01

    The Scanning Laser Acoustic Microscope produces images of internal structure in materials. The acoustic microscope is an imaging system based upon acoustic rather than electromagnetic waves. Variations in the elastic propertis are primarily responsible for structure visualized in acoustic micrographs. The instrument used in these investigations is the SONOMICROSCOPE 100 which can be operated at ultrasonic frequencies of from 30 MHz to 500 MHz. The examination of the silicon solar cells was made at 100 MHz. Data are presented in the form of photomicrographs.

  4. Construction of a new type of low-energy scanning electron microscope with atomic resolution

    NASA Astrophysics Data System (ADS)

    Eastham, D. A.; Edmondson, P.; Donnelly, S.; Olsson, E.; Svensson, K.; Bleloch, A.

    2009-05-01

    We describe a new type of scanning electron microscope which works by directly imaging the electron field-emission sites on a nanotip. Electrons are extracted from the nanotip through a nanoscale aperture, accelerated in a high electric field and focussed to a spot using a microscale einzel lens. If the whole microscope (accelerating section and lens) and the focal length are both restricted in size to below 10 microns, then computer simulations show that the effects of aberration are extremely small and it is possible to have a system with approximately unit magnification, at electron energies as low as 300 eV. Thus a typical emission site of 1 nm diameter will produce an image of the same size and an atomic emission site with give a resolution of 0.1-0.2 nm (1-2 Å), and because the beam is not allowed to expand beyond 100nm in diameter the depth of field is large and the contribution to the beam spot size from chromatic aberrations is less than 0.02 nm (0.2 Å) for 500 eV electrons. Since it is now entirely possible to make stable atomic sized emitters (nanopyramids) it is expected that this instrument will have atomic resolution. Furthermore the brightness of the beam is determined only by the field-emission and can be up to a million times larger than in a typical (high-energy) electron microscope. The construction of this microscope, based on using a nanotip electron source which is mounted on a nanopositioner so that it can be positioned at the correct point adjacent to the microscope, entrance aperture, is described. In this geometry the scanning is achieved by moving the sample using piezos. Two methods for the construction of the microscope column are reviewed and the results of preliminary tests are described. The advantages of this low energy, bright-beam, electron microscope with atomic resolution are described. It can be used in either scanning mode or diffraction mode. The major advantage over existing microscopes is that because it works at very low

  5. Scanning tunneling microscopy of cauliflower-like DNA nanostructures synthesised by loop-mediated isothermal amplification.

    PubMed

    Gill, P; Ranjbar, B; Saber, R

    2011-03-01

    DNA nanotechnology is a novel approach for synthesis of DNA-based nanostructures. Stem-loops, nanojunctions, sticky-ends and periodic lengths of DNA are the most essential nanostructures in DNA nanofabrications. Loop-mediated isothermal amplification (LAMP) is a powerful technology for repetitive synthesis of double-stranded and cauliflower-like DNAs. The process leads to long and repetitive sequences of DNAs, which are fabricated via loop primers. The authors demonstrate here scanning tunneling micrographs of LAMP-synthesised DNAs deposited on highly ordered pyrolytic graphite. The scans are compared with natural DNAs. Scanning tunneling microscopy (STM) images indicated the creation of periodic long DNAs, stem-looped DNAs and three-way DNA nanojunctions. It is also suggested that such nanomaterials could be promising candidates for use in DNA-based nanodevices.

  6. An ultra-low temperature scanning Hall probe microscope for magnetic imaging below 40 mK

    NASA Astrophysics Data System (ADS)

    Karcı, Özgür; Piatek, Julian O.; Jorba, Pau; Dede, Münir; Rønnow, Henrik M.; Oral, Ahmet

    2014-10-01

    We describe the design of a low temperature scanning Hall probe microscope (SHPM) for a dilution refrigerator system. A detachable SHPM head with 25.4 mm OD and 200 mm length is integrated at the end of the mixing chamber base plate of the dilution refrigerator insert (Oxford Instruments, Kelvinox MX-400) by means of a dedicated docking station. It is also possible to use this detachable SHPM head with a variable temperature insert (VTI) for 2 K-300 K operations. A microfabricated 1μm size Hall sensor (GaAs/AlGaAs) with integrated scanning tunneling microscopy tip was used for magnetic imaging. The field sensitivity of the Hall sensor was better than 1 mG/√Hz at 1 kHz bandwidth at 4 K. Both the domain structure and topography of LiHoF4, which is a transverse-field Ising model ferromagnet which orders below TC = 1.53 K, were imaged simultaneously below 40 mK.

  7. An ultra-low temperature scanning Hall probe microscope for magnetic imaging below 40 mK.

    PubMed

    Karcı, Özgür; Piatek, Julian O; Jorba, Pau; Dede, Münir; Rønnow, Henrik M; Oral, Ahmet

    2014-10-01

    We describe the design of a low temperature scanning Hall probe microscope (SHPM) for a dilution refrigerator system. A detachable SHPM head with 25.4 mm OD and 200 mm length is integrated at the end of the mixing chamber base plate of the dilution refrigerator insert (Oxford Instruments, Kelvinox MX-400) by means of a dedicated docking station. It is also possible to use this detachable SHPM head with a variable temperature insert (VTI) for 2 K-300 K operations. A microfabricated 1μm size Hall sensor (GaAs/AlGaAs) with integrated scanning tunneling microscopy tip was used for magnetic imaging. The field sensitivity of the Hall sensor was better than 1 mG/√Hz at 1 kHz bandwidth at 4 K. Both the domain structure and topography of LiHoF4, which is a transverse-field Ising model ferromagnet which orders below TC = 1.53 K, were imaged simultaneously below 40 mK.

  8. Intercomparison of lateral scales of scanning electron microscopes and atomic force microscopes in research institutes in Northern Europe

    NASA Astrophysics Data System (ADS)

    Seppä, Jeremias; Korpelainen, Virpi; Bergstrand, Sten; Karlsson, Helge; Lillepea, Lauri; Lassila, Antti

    2014-04-01

    An intercomparison of lateral scales of scanning electron microscopes (SEM) and atomic force microscopes (AFM) in various research laboratories in Northern Europe was organized by the local national metrology institutes. In this paper are presented the results of the comparison, with also an example uncertainty budget for AFM grating pitch measurement. Grating samples (1D) were circulated among the participating laboratories. The participating laboratories were also asked about the calibration of their instruments. The accuracy of the uncertainty estimates seemed to vary largely between the laboratories, and for some laboratories the appropriateness of the calibration procedures could be considered. Several institutes (60% of all results in terms of En value) also had good comprehension of their measurement capability. The average difference from reference value was 6.7 and 10.0 nm for calibrated instruments and 20.6 and 39.9 nm for uncalibrated instruments for 300 nm and 700 nm gratings, respectively. The correlation of the results for both nominally 300 and 700 nm gratings shows that a simple scale factor calibration would have corrected a large part of the deviations from the reference values.

  9. Apparent rippling with honeycomb symmetry and tunable periodicity observed by scanning tunneling microscopy on suspended graphene

    NASA Astrophysics Data System (ADS)

    Georgi, A.; Nemes-Incze, P.; Szafranek, B.; Neumaier, D.; Geringer, V.; Liebmann, M.; Morgenstern, M.

    2016-11-01

    Suspended graphene is difficult to image by scanning probe microscopy due to the inherent van der Waals and dielectric forces exerted by the tip, which are not counteracted by a substrate. Here, we report scanning tunneling microscopy data of suspended monolayer graphene in constant-current mode, revealing a surprising honeycomb structure with amplitude of 50-200 pm and lattice constant of 10-40 nm. The apparent lattice constant is reduced by increasing the tunneling current I , but does not depend systematically on tunneling voltage V or scan speed vscan. The honeycomb lattice of the rippling is aligned with the atomic structure observed on supported areas, while no atomic corrugation is found on suspended areas down to the resolution of about 3 -4 pm. We rule out that the honeycomb structure is induced by the feedback loop using a changing vscan, that it is a simple enlargement effect of the atomic lattice, as well as models predicting frozen phonons or standing phonon waves induced by the tunneling current. Although we currently do not have a convincing explanation for the observed effect, we expect that our intriguing results will inspire further research related to suspended graphene.

  10. Scanning tunneling spectroscopy of the vortex state in NbSe 2 using a superconducting tip

    NASA Astrophysics Data System (ADS)

    Rodrigo, J. G.; Crespo, V.; Vieira, S.

    2008-04-01

    The vortex electronic structure in the multiband superconductor NbSe2 is studied by means of scanning tunneling spectroscopy (STS) using a superconducting tip. The use of a superconducting tip (Pb) as a probe provides an enhancement of the different features related to the DOS of NbSe2 in the tunneling conductance curves. This use allows the observation of rich patterns of electronic states in the conductance images around the vortex cores in a wide range of temperature, as well as the simultaneous acquisition of Josephson current images in the vortex state.

  11. Imaging correlated wave functions of few-electron quantum dots: Theory and scanning tunneling spectroscopy experimentsa)

    NASA Astrophysics Data System (ADS)

    Rontani, Massimo; Molinari, Elisa; Maruccio, Giuseppe; Janson, Martin; Schramm, Andreas; Meyer, Christian; Matsui, Tomohiro; Heyn, Christian; Hansen, Wolfgang; Wiesendanger, Roland

    2007-04-01

    We show both theoretically and experimentally that scanning tunneling spectroscopy (STS) images of semiconductor quantum dots may display clear signatures of electron-electron correlation. We apply many-body tunneling theory to a realistic model, which fully takes into account correlation effects and dot anisotropy. Comparing measured STS images of freestanding InAs quantum dots with those calculated by the full configuration interaction method, we explain the wave-function sequence in terms of images of one- and two-electron states. The STS map corresponding to double charging is significantly distorted by electron correlation with respect to the noninteracting case.

  12. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    SciTech Connect

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-15

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  13. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications.

    PubMed

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  14. Combined frequency modulated atomic force microscopy and scanning tunneling microscopy detection for multi-tip scanning probe microscopy applications

    NASA Astrophysics Data System (ADS)

    Morawski, Ireneusz; Spiegelberg, Richard; Korte, Stefan; Voigtländer, Bert

    2015-12-01

    A method which allows scanning tunneling microscopy (STM) tip biasing independent of the sample bias during frequency modulated atomic force microscopy (AFM) operation is presented. The AFM sensor is supplied by an electronic circuit combining both a frequency shift signal and a tunneling current signal by means of an inductive coupling. This solution enables a control of the tip potential independent of the sample potential. Individual tip biasing is specifically important in order to implement multi-tip STM/AFM applications. An extensional quartz sensor (needle sensor) with a conductive tip is applied to record simultaneously topography and conductivity of the sample. The high resonance frequency of the needle sensor (1 MHz) allows scanning of a large area of the surface being investigated in a reasonably short time. A recipe for the amplitude calibration which is based only on the frequency shift signal and does not require the tip being in contact is presented. Additionally, we show spectral measurements of the mechanical vibration noise of the scanning system used in the investigations.

  15. Development of a hybrid atomic force microscopic measurement system combined with white light scanning interferometry.

    PubMed

    Guo, Tong; Wang, Siming; Dorantes-Gonzalez, Dante J; Chen, Jinping; Fu, Xing; Hu, Xiaotang

    2012-01-01

    A hybrid atomic force microscopic (AFM) measurement system combined with white light scanning interferometry for micro/nanometer dimensional measurement is developed. The system is based on a high precision large-range positioning platform with nanometer accuracy on which a white light scanning interferometric module and an AFM head are built. A compact AFM head is developed using a self-sensing tuning fork probe. The head need no external optical sensors to detect the deflection of the cantilever, which saves room on the head, and it can be directly fixed under an optical microscopic interferometric system. To enhance the system's dynamic response, the frequency modulation (FM) mode is adopted for the AFM head. The measuring data can be traceable through three laser interferometers in the system. The lateral scanning range can reach 25 mm × 25 mm by using a large-range positioning platform. A hybrid method combining AFM and white light scanning interferometry is proposed to improve the AFM measurement efficiency. In this method, the sample is measured firstly by white light scanning interferometry to get an overall coarse morphology, and then, further measured with higher resolution by AFM. Several measuring experiments on standard samples demonstrate the system's good measurement performance and feasibility of the hybrid measurement method.

  16. Mechanism for improving the signal-to-noise ratio in scanning optical microscopes

    NASA Astrophysics Data System (ADS)

    Milster, Tom D.; Walker, Edwin P.

    1996-08-01

    We demonstrate an improved signal-to-noise ratio in a scanning optical microscope used to read out information from a magneto-optical data storage layer. By placing a shading band in the return path of the optical system we can reduce noise by as much as 3 dB in certain spatial frequency ranges. The signal-to-noise ratio improvement arises from differences in the signal and noise distributions in the pupil of the optical system. Although the experimental results are shown only in one dimension, the concept is applicable to two-dimensional scanning of low-contrast samples.

  17. Magnetic field imaging of a tungsten carbide film by scanning nano-SQUID microscope

    NASA Astrophysics Data System (ADS)

    Shibata, Yusuke; Nomura, Shintaro; Ishiguro, Ryosuke; Kashiwaya, Hiromi; Kashiwaya, Satoshi; Nago, Yusuke; Takayanagi, Hideaki

    2016-10-01

    We present the results of magnetic field imaging by scanning nano-superconducting quantum interference device (SQUID) microscopy on a tungsten carbide (W-C) film fabricated using focused-ion-beam chemical vapor deposition. We have investigated magnetic field change by a W-C film in an external magnetic field using a scanning nano-SQUID microscope system. We have found that the reduction of the magnetic field above the W-C film was 0.9%, indicating the penetration of vortices in the W-C at an external magnetic field of 0.171 mT.

  18. Detection of Luminescent Nanodiamonds Using a Scanning Near-Field Optical Microscope with an Aperture Probe

    NASA Astrophysics Data System (ADS)

    Shershulin, V. A.; Samoylenko, S. R.; Shenderova, O. A.; Vlasov, I. I.; Konov, V. I.

    2016-09-01

    Scanning near-fi eld optical microscopy (SNOM) with an aperture probe has been used to map the luminescence of isolated submicron diamond crystallites. 532-nm laser light was used to excite luminescence of nitrogen-vacancy (NV) centers. The sizes of the analyzed diamond crystallites were determined with an atomic-force microscope. The optical resolution for the lateral dimensions of the luminescing diamond crystallites was doubled on going from confocal luminescence microscopy to scanning near-fi eld optical microscopy with a 290-nm probe aperture diameter.

  19. A compact multipurpose nanomanipulator for use inside a scanning electron microscope

    NASA Astrophysics Data System (ADS)

    Heeres, E. C.; Katan, A. J.; van Es, M. H.; Beker, A. F.; Hesselberth, M.; van der Zalm, D. J.; Oosterkamp, T. H.

    2010-02-01

    A compact, two-stage nanomanipulator was designed and built for use inside a scanning electron microscope. It consists of a fine stage employing piezostacks that provide a 15 μm range in three dimensions and a coarse stage based on commercially available stick-slip motors. Besides the fabrication of enhanced probes for scanning probe microscopy and the enhancement of electron field emitters, other novel manipulation processes were developed, such as locating, picking up, and positioning small nanostructures with an accuracy of ˜10 nm. In combination with in situ I-V experiments, welding, and etching, this results in a multipurpose nanofactory, enabling a new range of experiments.

  20. Scanning Electron Microscope Calibration Using a Multi-Image Non-Linear Minimization Process

    NASA Astrophysics Data System (ADS)

    Cui, Le; Marchand, Éric

    2015-04-01

    A scanning electron microscope (SEM) calibrating approach based on non-linear minimization procedure is presented in this article. A part of this article has been published in IEEE International Conference on Robotics and Automation (ICRA), 2014. . Both the intrinsic parameters and the extrinsic parameters estimations are achieved simultaneously by minimizing the registration error. The proposed approach considers multi-images of a multi-scale calibration pattern view from different positions and orientations. Since the projection geometry of the scanning electron microscope is different from that of a classical optical sensor, the perspective projection model and the parallel projection model are considered and compared with distortion models. Experiments are realized by varying the position and the orientation of a multi-scale chessboard calibration pattern from 300× to 10,000×. The experimental results show the efficiency and the accuracy of this approach.

  1. A scanning soft x-ray microscope with an ellipsoidal focusing mirror.

    PubMed

    Voss, J; Dadras, H; Kunz, C; Moewes, A; Roy, G; Sievers, H; Storjohann, I; Wongel, H

    1992-01-01

    We have developed and brought into operation a new type of scanning soft x-ray microscope which can operate at any photon energy from 20 to 1300 eV. This microscope demagnifies a diaphragm by means of an annular section of an ellipsoidal mirror to a smallest spot size of, at present, about 0.4 μm (FWHM), certainly containing only a small fraction of the total intensity. The sample is scanned across this spot. Between mirror and focus a free space of 30 mm is available for detectors, and particles emitted from a surface at more than 30° to the normal can be extracted into a mass or energy analyzer. Transmission, photoemission, luminescence, photostimulated desorption, reflectivity, and other signals may serve for imaging. In addition, a static analysis of very small samples or spots on a sample will become feasible.

  2. Depth Sectioning with the Aberration-Corrected Scanning Transmission Electron Microscope

    SciTech Connect

    Borisevich, Albina Y; Lupini, Andrew R; Pennycook, Stephen J

    2006-01-01

    The ability to correct the aberrations of the probe-forming lens in the scanning transmission electron microscope provides not only a significant improvement in transverse resolution but in addition brings depth resolution at the nanometer scale. Aberration correction therefore opens up the possibility of 3D imaging by optical sectioning. Here we develop a definition for the depth resolution for scanning transmission electron microscope depth sectioning and present initial results from this method. Objects such as catalytic metal clusters and single atoms on various support materials are imaged in three dimensions with a resolution of several nanometers. Effective focal depth is determined by statistical analysis and the contributing factors are discussed. Finally, current challenges and future capabilities available through new instruments are discussed.

  3. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-07-13

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  4. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2010-06-29

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  5. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-11-10

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of impaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  6. Spin microscope based on optically detected magnetic resonance

    DOEpatents

    Berman, Gennady P.; Chernobrod, Boris M.

    2007-12-11

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  7. Spin microscope based on optically detected magnetic resonance

    SciTech Connect

    Berman, Gennady P.; Chernobrod, Boris M.

    2009-10-27

    The invention relates to scanning magnetic microscope which has a photoluminescent nanoprobe implanted in the tip apex of an atomic force microscope (AFM), a scanning tunneling microscope (STM) or a near-field scanning optical microscope (NSOM) and exhibits optically detected magnetic resonance (ODMR) in the vicinity of unpaired electron spins or nuclear magnetic moments in the sample material. The described spin microscope has demonstrated nanoscale lateral resolution and single spin sensitivity for the AFM and STM embodiments.

  8. Differential phase microscope and micro-tomography with a Foucault knife-edge scanning filter

    NASA Astrophysics Data System (ADS)

    Watanabe, N.; Hashizume, J.; Goto, M.; Yamaguchi, M.; Tsujimura, T.; Aoki, S.

    2013-10-01

    An x-ray differential phase microscope with a Foucault knife-edge scanning filter was set up at the bending magnet source BL3C, Photon Factory. A reconstructed phase profile from the differential phase image of an aluminium wire at 5.36 keV was fairly good agreement with the numerical simulation. Phase tomography of a biological specimen, such as an Artemia cyst, could be successfully demonstrated.

  9. Carbon-fiber tips for scanning probe microscopes and molecular electronics experiments

    PubMed Central

    2012-01-01

    We fabricate and characterize carbon-fiber tips for their use in combined scanning tunneling and force microscopy based on piezoelectric quartz tuning fork force sensors. An electrochemical fabrication procedure to etch the tips is used to yield reproducible sub-100-nm apex. We also study electron transport through single-molecule junctions formed by a single octanethiol molecule bonded by the thiol anchoring group to a gold electrode and linked to a carbon tip by the methyl group. We observe the presence of conductance plateaus during the stretching of the molecular bridge, which is the signature of the formation of a molecular junction. PMID:22587692

  10. Compact two-photon laser-scanning microscope made from minimally modified commercial components

    NASA Astrophysics Data System (ADS)

    Iyer, Vijay; Hoogland, Tycho; Losavio, Bradley E.; McQuiston, A. R.; Saggau, Peter

    2002-06-01

    A compact two-photon laser-scanning microscope (TPLSM) was constructed using a diode-pumped, mode-locked Nd:YLF laser (Biolight 1000, Coherent Laser Group) and a small confocal laser scan-head (PCM2000, Nikon Bioscience). The laser emits at 1047nm and is fiber-coupled to a compact compressor unit producing a pulse-width of ~175fsec. Both the pulse compressor and confocal scan head were interfaced on a small optical breadboard that was directly attached to an upright research microscope (Eclipse E600FN, Nikon Bioscience). Two-photon fluorescence emitted from the specimen was collected into a multimode fiber and transmitted directly to an external PMT supplied with the Nikon confocal system. The modifications to the scanhead were minimal (a single mirror replacement) and did not interfere with its confocal function. The resulting system offers several advantages: compact size, turnkey operation, and the ability to translate the microscope rather than an often delicate specimen. In addition, it is possible to switch between confocal and two-photon operation, allowing for straightforward comparison. Using this compact TPLSM, we obtained structural and functional images from hippocampal neurons in living brain slices using commonly available fluorophores.

  11. Fabrication and Characterization of Low-Dimensional Nanostructures using Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Fujita, Daisuke; Sagisaka, Keisuke; Onishi, Keiko; Ohgi, Taizo

    Recent developments of fabrication, manipulation and characterization techniques at nanometer scale for low-dimensional nanostructures using scanning tunneling microscopy (STM) are reviewed. Firstly two reliable methods for metallic nanostructure formation using tip material transfer are introduced. Secondly STM-manipulation of Au nanoclusters grown on self-assembled monolayers is introduced, where single electron tunneling effect is clearly observable using tunneling spectroscopy. As a new type of STM manipulation, a reversible control method of surface periodic structures (phases) on Si(100) at low temperatures is introduced. Finally using a single atom deposition technique using a controlled point contact, fabrication of one-dimensional quantum well on a single dimer row of Si(100) surface is explained. Combining the fabrication and characterization capabilities of STM in various environments, STM can be a powerful tool for the exploration of nanotechnology and nanoscience.

  12. Field enhancement factors and self-focus functions manifesting in field emission resonances in scanning tunneling microscopy.

    PubMed

    Su, Wei-Bin; Lin, Chun-Liang; Chan, Wen-Yuan; Lu, Shin-Ming; Chang, Chia-Seng

    2016-04-29

    Field emission (FE) resonance (or Gundlach oscillation) in scanning tunneling microscopy (STM) is a phenomenon in which the FE electrons emitted from the microscope tip couple into the quantized standing-wave states within the STM tunneling gap. Although the occurrence of FE resonance peaks can be semi-quantitatively described using the triangular potential well model, it cannot explain the experimental observation that the number of resonance peaks may change under the same emission current. This study demonstrates that the aforementioned variation can be adequately explained by introducing a field enhancement factor that is related to the local electric field at the tip apex. The peak number of FE resonances increases with the field enhancement factor. The peak intensity of the FE resonance on the reconstructed Au(111) surface varies in the face-center cubic, hexagonal-close-packed, and ridge regions, thus providing the contrast in the mapping through FE resonances. The mapping contrast is demonstrated to be nearly independent of the tip-sample distance, implying that the FE electron beam is not divergent because of a self-focus function intrinsically involved in the STM configuration.

  13. Quantum Interference between Energy Absorption Processes of Molecular Exciton and Interface Plasmons on Luminescence Induced by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Miwa, Kuniyuki; Imasa, Hiroshi; Sakaue, Mamoru; Kasai, Hideaki; Kim, Yousoo

    2015-03-01

    Luminescence induced by the tunneling current of a scanning tunneling microscope (STM) from molecule-covered metal surfaces is attributed to radiative decays of molecules and interface plasmons localized near the tip-substrate gap region. Since the dynamics of molecule and interface plasmons strongly influence each other, the interplay between these dynamics gives rise to peculiar phenomena originating from quantum many-body effects. In this study, we develop the effective model of the system and investigate the luminescence properties using the nonequilibrium Green's function method. The results show that, in addition to the dynamics of molecule, energy reabsorption by interface plasmons have a critical role in determining the luminescence spectral profile of interface plasmons. The additional peak structure arises owing to the interference between these energy absorption processes. Origin of prominent peak and dip structures observed in recent experiments are identified by the developed theory. The details of the interference effects on the luminescence properties will be discussed. This work was supported by JSPS KAKENHI Grant Number 26886013.

  14. Automatic Extraction of Tunnel Lining Cross-Sections from Terrestrial Laser Scanning Point Clouds

    PubMed Central

    Cheng, Yun-Jian; Qiu, Wenge; Lei, Jin

    2016-01-01

    Tunnel lining (bare-lining) cross-sections play an important role in analyzing deformations of tunnel linings. The goal of this paper is to develop an automatic method for extracting bare-lining cross-sections from terrestrial laser scanning (TLS) point clouds. First, the combination of a 2D projection strategy and angle criterion is used for tunnel boundary point detection, from which we estimate the two boundary lines in the X-Y plane. The initial direction of the cross-sectional plane is defined to be orthogonal to one of the two boundary lines. In order to compute the final cross-sectional plane, the direction is adjusted twice with the total least squares method and Rodrigues’ rotation formula, respectively. The projection of nearby points is made onto the adjusted plane to generate tunnel cross-sections. Finally, we present a filtering algorithm (similar to the idea of the morphological erosion) to remove the non-lining points in the cross-section. The proposed method was implemented on railway tunnel data collected in Sichuan, China. Compared with an existing method of cross-sectional extraction, the proposed method can offer high accuracy and more reliable cross-sectional modeling. We also evaluated Type I and Type II errors of the proposed filter, at the same time, which gave suggestions on the parameter selection of the filter. PMID:27782063

  15. Automatic Extraction of Tunnel Lining Cross-Sections from Terrestrial Laser Scanning Point Clouds.

    PubMed

    Cheng, Yun-Jian; Qiu, Wenge; Lei, Jin

    2016-10-06

    Tunnel lining (bare-lining) cross-sections play an important role in analyzing deformations of tunnel linings. The goal of this paper is to develop an automatic method for extracting bare-lining cross-sections from terrestrial laser scanning (TLS) point clouds. First, the combination of a 2D projection strategy and angle criterion is used for tunnel boundary point detection, from which we estimate the two boundary lines in the X-Y plane. The initial direction of the cross-sectional plane is defined to be orthogonal to one of the two boundary lines. In order to compute the final cross-sectional plane, the direction is adjusted twice with the total least squares method and Rodrigues' rotation formula, respectively. The projection of nearby points is made onto the adjusted plane to generate tunnel cross-sections. Finally, we present a filtering algorithm (similar to the idea of the morphological erosion) to remove the non-lining points in the cross-section. The proposed method was implemented on railway tunnel data collected in Sichuan, China. Compared with an existing method of cross-sectional extraction, the proposed method can offer high accuracy and more reliable cross-sectional modeling. We also evaluated Type I and Type II errors of the proposed filter, at the same time, which gave suggestions on the parameter selection of the filter.

  16. Using the Scanning Electron Microscope to Study Tracks in CR-39

    NASA Astrophysics Data System (ADS)

    Sullivan, Kyle; Roberts, Samuel; McLean, James; Padalino, Steve

    2002-10-01

    CR-39 is a plastic used for high-energy charged particle detection. When particles hit the detector, they create tracks. These tracks can be enlarged with wet-chemical etching, and are useful in determining the energy and type of incident particle. To understand the etching process beyond the capabilities of an optical microscope, a scanning electron microscope investigation was undertaken. Preparation of a CR-39 sample involved exposing it to 5.5 MeV alpha particles, etching it in 6M NaOH at 80 degrees Celsius, and applying a thin conductive layer of gold-palladium. Three main areas of study were focused upon. It was found that the diameters of tracks increased linearly as a function of how long the samples were etched. A depth profile of a track was constructed by using the parallax that occurs between normal and tilted views. Techniques for scanning an entire sample were compared to optical methods used at the Laboratory for Laser Energetics. Although higher image quality can be achieved, factors, such as total scan time, decreased its appeal as a new way to scan CR-39. Research funded in part by the United States Department of Energy

  17. Observation and manipulation of hexa-adamantyl-hexa-benzocoronene molecules by low temperature scanning tunneling microscopy.

    PubMed

    Calmettes, Bastien; Vernisse, Loranne; Guillermet, Olivier; Benjalal, Youness; Bouju, Xavier; Coudret, Christophe; Coratger, Roland

    2014-11-07

    Large molecules made of a central hexa-adamantyl-hexa-benzocoronene plateau surrounded by six adamantyl groups have been investigated by low temperature scanning tunneling microscopy and scanning tunneling spectroscopy coupled with image calculations and molecular mechanics. The structure of large self-assembled domains reveals that the intermolecular interactions between adamantyl peripheral groups dominate film growth. At very low coverage, the molecules can exhibit a certain instability for negative bias voltages which induces a partial rotation. Manipulations of single objects using the STM tip are used to create small clusters of two or three molecules. The formed structures can be obtained and manipulated provided that the flexible adamantyl moieties of neighbouring molecules are brought in close contact promoting a robust mechanical anchoring.

  18. Scanning-tunneling-microscopy and spectroscopy studies of C70 thin films on gold substrates

    NASA Astrophysics Data System (ADS)

    Chen, T.; Howells, S.; Gallagher, M.; Sarid, D.; Lamb, L. D.; Huffman, D. R.; Workman, R. K.

    1992-06-01

    Thin films of high-purity C70 were deposited on polycrystalline gold surfaces and studied by scanning tunneling microscropy (STM) in ultrahigh vacuum. Topographic images reveal initial-stage growth patterns ranging from close packing with a twofold symmetry to random stacking. C70 molecules appear oval-shaped, in agreement with the proposed D5h structure of C70. Static orientational disorder is observed in both close-packed and random-stacked regions. The adsorbed C70 molecules show the highest STM contrast at bias voltages well below the HOMO-LUMO gap voltage. These and scanning-tunneling-spectroscopy results are discussed and compared with those obtained previously on similarly prepared C60 thin films.

  19. Method and apparatus for a high-resolution three dimensional confocal scanning transmission electron microscope

    DOEpatents

    de Jonge, Niels [Oak Ridge, TN

    2010-08-17

    A confocal scanning transmission electron microscope which includes an electron illumination device providing an incident electron beam propagating in a direction defining a propagation axis, and a precision specimen scanning stage positioned along the propagation axis and movable in at least one direction transverse to the propagation axis. The precision specimen scanning stage is configured for positioning a specimen relative to the incident electron beam. A projector lens receives a transmitted electron beam transmitted through at least part of the specimen and focuses this transmitted beam onto an image plane, where the transmitted beam results from the specimen being illuminated by the incident electron beam. A detection system is placed approximately in the image plane.

  20. Pointed carbon fiber ultramicroelectrodes: a new probe option for electrochemical scanning tunneling microscopy.

    PubMed

    Sripirom, Jiyapa; Kuhn, Sonja; Jung, Ulrich; Magnussen, Olaf; Schulte, Albert

    2013-01-15

    Carbon tips for in situ scanning tunneling microscopy studies in an electrochemical environment were prepared by electrochemical etching of carbon fibers and subsequent coating with electrodeposition paint and a silicone elastomer. The tips obtained were stable in acidic electrolyte and allowed high-resolution in situ imaging of the bare Au(111) electrode surface and of Au(111) covered by monolayers of the octyl-triazatriangulenium molecule.

  1. Note: Fabrication and characterization of molybdenum tips for scanning tunneling microscopy and spectroscopy

    SciTech Connect

    Carrozzo, P.; Tumino, F.; Facibeni, A.; Passoni, M.; Casari, C. S.; Li Bassi, A.

    2015-01-15

    We present a method for the preparation of bulk molybdenum tips for Scanning Tunneling Microscopy and Spectroscopy and we assess their potential in performing high resolution imaging and local spectroscopy by measurements on different single crystal surfaces in UHV, namely, Au(111), Si(111)-7 × 7, and titanium oxide 2D ordered nanostructures supported on Au(111). The fabrication method is versatile and can be extended to other metals, e.g., cobalt.

  2. Surface structure and analysis with scanning probe microscopy and electron tunneling spectroscopy. Final report

    SciTech Connect

    Hsu, Julia

    1998-05-01

    This report summarizes the results accomplished during the funding period of this grant (June 1, 1995 to May 31, 1998). The projects are (1) room-temperature atomic force microscopy (AFM) studies of NbSe{sub 3} doped with various elements and (2) low-temperature scanning tunneling microscopy (STM) studies of NbSe{sub 3}. In addition, AFM was used to study the surface morphology and defects of GaAs films grown on Ge and Ge/Si substracts.

  3. Ultrafast Scanning Tunneling Microscopy Using a Photoexcited Low-Temperature-Grown GaAs Tip

    SciTech Connect

    Donati, G.P.; Rodriguez, G.; Taylor, A.J.

    1999-05-21

    The authors report ultrafast scanning tunneling microscopy using a low-temperature-grown GaAs tip photoexcited by 100-fs, 800-nm pulses. They use this tip to detect picosecond transients on a coplanar stripline and demonstrate a temporal resolution of 1.7 ps. A dependence of the transient signal upon spatial position of the tip is revealed, indicating that the signal arises from areas on the sample smaller than {approximately}20nm.

  4. The geometry of nanometer-sized electrodes and its influence on electrolytic currents and metal deposition processes in scanning tunneling and scanning electrochemical microscopy

    NASA Astrophysics Data System (ADS)

    Sklyar, Oleg; Treutler, Thomas H.; Vlachopoulos, Nikolaos; Wittstock, Gunther

    2005-12-01

    Electrodes with an effective radius of about 10 nm have been produced by a combination of electrochemical etching, electrophoretic deposition of polymer, and heat curing. Their size and stability were characterized by cyclic voltammetry. They were then used in combined electrochemical scanning tunneling microscopic (ECSTM) and scanning electrochemical microscopic (SECM) experiments. In an extension of an earlier report, electrochemical surface modification approaches are reported here. They comprise the local electrochemical removal of a self-assembled monolayer (SAM) of dodecanethiol on flame-annealed gold by an electrochemical desorption procedure. The possibility of local electrochemical deposition is demonstrated by positioning a nanoelectrode 0.5 nm above a surface and switching off the distance regulation while performing an electrodeposition of Pt at the tip. The growing deposit bridges the tip-sample gap. If the distance regulation is switched on after 1 ms, the Pt junction is disrupted leaving a Pt nanodot at the sample surface. The dot was characterized by ECSTM experiments after solution exchange. Digital simulations by the boundary element method (BEM) provide a quantitative description of Faraday currents in nanoelectrochemical assemblies. A software tool was created that can accept arbitrary geometries as input data sets. The flexibility of the simulation strategy was demonstrated by the calculation of local current densities during electrochemical copper deposition on a smooth electrode in the presence of an ECSTM tip close to the surface. The current densities deviate less than 1% from those in the absence of tip if the average current density is kept below 1 μA cm -2. SECM approach curves for nanoelectrodes were also calculated.

  5. Two-dimensional simulation and modeling in scanning electron microscope imaging and metrology research.

    PubMed

    Postek, Michael T; Vladár, András E; Lowney, Jeremiah R; Keery, William J

    2002-01-01

    Traditional Monte Carlo modeling of the electron beam-specimen interactions in a scanning electron microscope (SEM) produces information about electron beam penetration and output signal generation at either a single beam-landing location, or multiple landing positions. If the multiple landings lie on a line, the results can be graphed in a line scan-like format. Monte Carlo results formatted as line scans have proven useful in providing one-dimensional information about the sample (e.g., linewidth). When used this way, this process is called forward line scan modeling. In the present work, the concept of image simulation (or the first step in the inverse modeling of images) is introduced where the forward-modeled line scan data are carried one step further to construct theoretical two-dimensional (2-D) micrographs (i.e., theoretical SEM images) for comparison with similar experimentally obtained micrographs. This provides an ability to mimic and closely match theory and experiment using SEM images. Calculated and/or measured libraries of simulated images can be developed with this technique. The library concept will prove to be very useful in the determination of dimensional and other properties of simple structures, such as integrated circuit parts, where the shape of the features is preferably measured from a single top-down image or a line scan. This paper presents one approach to the generation of 2-D simulated images and presents some suggestions as to their application to critical dimension metrology.

  6. Scanning tunneling microscopy study and nanomanipulation of graphene-coated water on mica.

    PubMed

    He, Kevin T; Wood, Joshua D; Doidge, Gregory P; Pop, Eric; Lyding, Joseph W

    2012-06-13

    We study interfacial water trapped between a sheet of graphene and a muscovite (mica) surface using Raman spectroscopy and ultrahigh vacuum scanning tunneling microscopy (UHV-STM) at room temperature. We are able to image the graphene-water interface with atomic resolution, revealing a layered network of water trapped underneath the graphene. We identify water layer numbers with a carbon nanotube height reference. Under normal scanning conditions, the water structures remain stable. However, at greater electron energies, we are able to locally manipulate the water using the STM tip.

  7. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK.

    PubMed

    den Haan, A M J; Wijts, G H C J; Galli, F; Usenko, O; van Baarle, G J C; van der Zalm, D J; Oosterkamp, T H

    2014-03-01

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures.

  8. Atomic resolution scanning tunneling microscopy in a cryogen free dilution refrigerator at 15 mK

    SciTech Connect

    Haan, A. M. J. den Wijts, G. H. C. J.; Galli, F.; Oosterkamp, T. H.; Usenko, O.; Baarle, G. J. C. van; Zalm, D. J. van der

    2014-03-15

    Pulse tube refrigerators are becoming more common, because they are cost efficient and demand less handling than conventional (wet) refrigerators. However, a downside of a pulse tube system is the vibration level at the cold-head, which is in most designs several micrometers. We implemented vibration isolation techniques which significantly reduced vibration levels at the experiment. These optimizations were necessary for the vibration sensitive magnetic resonance force microscopy experiments at milli-kelvin temperatures for which the cryostat is intended. With these modifications we show atomic resolution scanning tunneling microscopy on graphite. This is promising for scanning probe microscopy applications at very low temperatures.

  9. Scanning transmission x-ray microscope for materials science spectromicroscopy at the ALS

    SciTech Connect

    Warwick, T.; Seal, S.; Shin, H.

    1997-04-01

    The brightness of the Advanced Light Source will be exploited by several new instruments for materials science spectromicroscopy over the next year or so. The first of these to become operational is a scanning transmission x-ray microscope with which near edge x-ray absorption spectra (NEXAFS) can be measured on spatial features of sub-micron size. Here the authors describe the instrument as it is presently implemented, its capabilities, some studies made to date and the developments to come. The Scanning Transmission X-ray Microscope makes use of a zone plate lens to produce a small x-ray spot with which to perform absorption spectroscopy through thin samples. The x-ray beam from ALS undulator beamline 7.0 emerges into the microscope vessel through a silicon nitride vacuum window 160nm thick and 300{mu}m square. The vessel is filled with helium at atmospheric pressure. The zone plate lens is illuminated 1mm downstream from the vacuum window and forms an image in first order of a pinhole which is 3m upstream in the beamline. An order sorting aperture passes the first order converging light and blocks the unfocused zero order. The sample is at the focus a few mm downstream of the zone plate and mounted from a scanning piezo stage which rasters in x and y so that an image is formed, pixel by pixel, by an intensity detector behind the sample. Absorption spectra are measured point-by-point as the photon energy is scanned by rotating the diffraction grating in the monochromator and changing the undulator gap.

  10. Efficient transport of gold atoms with a scanning tunneling microscopy tip and a linker molecule.

    PubMed

    Boscoboinik, J Anibal; Kohlmeyer, Ryan R; Chen, Jian; Tysoe, Wilfred T

    2011-08-02

    A thiophene-containing molecule attached to a scanning tunneling microscopy (STM) tip is used to transport gold atoms on a Au(111) surface. The molecule contains eight thiophene rings and therefore has sulfur atoms that are known to bind to gold atoms. Using a gold-coated tip, the molecules previously deposited on the surface bind to the lower-coordination gold atoms of the tip. When that tip is used to scan the surface, the still free thiophene rings (not all of the sulfur atoms bind to the tip) can attach to gold atoms from the surface and drag them along the scanning direction, depositing them either at the position where the tip changes its scanning direction or where the tip encounters an "up step", whichever event occurs first.

  11. A scanning and transmission electron microscopic analysis of the cerebral aqueduct in the rabbit.

    PubMed

    Meller, S T; Dennis, B J

    1993-09-01

    An examination of the surface of the cerebral aqueduct with the scanning electron microscope revealed that the walls of the cerebral aqueduct were so heavily ciliated that most of the ependymal surface was obscured, yet certain specialized supraependymal structures could be discerned lying on (or embedded within) this matt of cilia. These structures were determined by transmission electron microscopy and Golgi analysis to be either macrophages, supraependymal neurons, dendrites from medial periaqueductal gray neurons, or axons of unknown origin. Some axons, which were found to contain vesicles, appeared to make synaptic contacts with ependymal cells. Using the transmission electron microscope, the ependymal lining was found to consist of two different cell types: normal ependymal cells and tanycytes which have a long tapering basal process that was observed to contact blood vessels or, more rarely, seemed to terminate in relation to neuronal elements. While there have been previous reports on the structure of the third and lateral ventricles in other species, there are limited reports in the rabbit. The present report is not only the first description for the rabbit, but it is the first complete scanning and transmission electron microscopic analysis of the cerebral aqueduct in any species.

  12. The structure of hematite (α-Fe 2O 3) (001) surfaces in aqueous media: scanning tunneling microscopy and resonant tunneling calculations of coexisting O and Fe terminations

    NASA Astrophysics Data System (ADS)

    Eggleston, Carrick M.; Stack, Andrew G.; Rosso, Kevin M.; Higgins, Steven R.; Bice, Angela M.; Boese, Steven W.; Pribyl, Richard D.; Nichols, Jeremy J.

    2003-03-01

    The iron oxide-water interface is of interest not only in geochemical and environmental processes, but also in fields ranging from corrosion to photocatalysis. The structure of α-Fe 2O 3 (001) surfaces is not fully understood, and questions have arisen recently concerning different terminations of (001) terraces; a so-called Fe-termination is expected, but under some conditions an O-termination may also be possible. Ultra-high vacuum (UHV) scanning tunneling microscope (STM) studies report evidence for an O-termination in coexistence with an Fe-termination, but other studies find no evidence for an O-termination. Molecular mechanics studies suggest that an O-termination should be possible in an aqueous environment. An O-termination could result from dissolution; if Fe atoms were to dissolve from an Fe-termination, an O-termination would presumably result (and vice-versa). We imaged hematite (001) surfaces in air and aqueous solution using STM. To aid interpretation of the images, we use a resonant tunneling model (RTM) parameterized using ab initio calculations. Our STM and RTM results are consistent with mixed O- and Fe-terminated (001) surfaces. For acid-etched surfaces we find evidence for a periodic (with wavelength of 2.2 ± 0.2 nm) arrangement of nominal O- and Fe-terminated domains. Two different borders between domains should occur, one in which the Fe-termination is high relative to the O-termination, and the reverse. The different domain borders have significantly different heights, consistent with RTM calculations. This agreement allows us to conclude that the Fe-termination is topographically high on most terraces. Surface domains are observed in aqueous solutions at the atomic scale, and appear to be very unreactive on tens-of-seconds time scales at pH 1.

  13. Development of a Near-Field Scanning Optical Microscope for Imaging Biological Samples in Physiological Buffer

    NASA Astrophysics Data System (ADS)

    Seibel, Eric Jeffrey

    A near-field scanning optical microscope was constructed for imaging intact biological samples in physiological buffer at a resolution beyond the optical diffraction limit. Images are formed by raster scanning the sample within the near -field of the optical probe, which emits collimated light for a limited distance. The technical challenges that were encountered were making the probe, micropositioning the probe and sample with piezoelectrics, and maintaining the sample-probe separation to within the near-field ( <200 nm). By recording the measurement of probe-sample separation during a scan, a topographic image is generated simultaneously with the near-field optical image. The microscope having both imaging modalities was tested and judged fully operational by imaging fluorescently -labeled microspheres under water. The potential of near-field scanning optical microscopy for future biological research was investigated by imaging a fluorescently-labeled, biological test specimen, the single myofibril. Imaging the intact myofibril in buffered saline without chemical fixation provides a challenging, practical test for the microscope. Near-field fluorescence and topographic images of single myofibrils produced image resolution of <=q300 nm, versus ~500 nm for conventional optical microscopy. Interpretation of the images is facilitated by the protein-specific fluorescence labeling. Increasing sample thickness degrades the resolution of the fluorescence images only. Thus, biological samples having > 1 μm thickness, are the practical limit of sample thickness for generating high resolution near-field optical images, when fluorescence is collected in transmission. In contrast, the method of generating the topographic images (called lateral shear-force microscopy), has the advantage of being insensitive to sample thickness. In the topographic images of myofibrils, the change in topography and/or stiffness from the binding of antibodies was detected. The results of this

  14. Nondestructive Sectioning Of Fixed And Living Specimens Using A Confocal Scanning Laser Fluorescence Microscope: Microtomoscopy

    NASA Astrophysics Data System (ADS)

    Stelzer, Ernst H...; Wijnaendts-Van-Resandt, Roelof W.

    1987-08-01

    Modern molecular biologists and in particular cell biologists have a large set of experimental tools at their disposal. Immunocytochemistry, fluorescence labels, and microscopy are only subsets of the entire spectrum of methods. Depending on the fields in which biologists work a lot of results are obtained with classical biochemistry, gel electrophoresis and blotting techniques. Gathering morphological data may not be the least important task, but will in many cases be considered only after all other methods have failed. With the advent of video microscopes and the availability of high speed image processing devices, microscopy can also be used for quantitation. Confocal scanning laser fluorescence microscopy (Ft-CSCM) [Cox 1984] is in fact another technique or method that is entering the rapidly developing field of quantitative microscopy. It is therefore very important to understand the physical properties of the CSCLM in detail and to compare a confocal microscope not only with other confocal microscopes, but also with all the other techniques and methods. The confocal microscope has to find its particular application and it should be understood that it will replace neither conventional microscopy, nor video microscopy, nor electron microscopy. It will not be used for every application and every type of investigation. The CSCM has to find its niche in the laboratories and this paper will present two applications in which it proves its usefulness.

  15. Identification of mycobacterium tuberculosis in sputum smear slide using automatic scanning microscope

    NASA Astrophysics Data System (ADS)

    Rulaningtyas, Riries; Suksmono, Andriyan B.; Mengko, Tati L. R.; Saptawati, Putri

    2015-04-01

    Sputum smear observation has an important role in tuberculosis (TB) disease diagnosis, because it needs accurate identification to avoid high errors diagnosis. In development countries, sputum smear slide observation is commonly done with conventional light microscope from Ziehl-Neelsen stained tissue and it doesn't need high cost to maintain the microscope. The clinicians do manual screening process for sputum smear slide which is time consuming and needs highly training to detect the presence of TB bacilli (mycobacterium tuberculosis) accurately, especially for negative slide and slide with less number of TB bacilli. For helping the clinicians, we propose automatic scanning microscope with automatic identification of TB bacilli. The designed system modified the field movement of light microscope with stepper motor which was controlled by microcontroller. Every sputum smear field was captured by camera. After that some image processing techniques were done for the sputum smear images. The color threshold was used for background subtraction with hue canal in HSV color space. Sobel edge detection algorithm was used for TB bacilli image segmentation. We used feature extraction based on shape for bacilli analyzing and then neural network classified TB bacilli or not. The results indicated identification of TB bacilli that we have done worked well and detected TB bacilli accurately in sputum smear slide with normal staining, but not worked well in over staining and less staining tissue slide. However, overall the designed system can help the clinicians in sputum smear observation becomes more easily.

  16. A novel approach for fast scanning of nuclear emulsions with continuous motion of the microscope stage

    NASA Astrophysics Data System (ADS)

    Aleksandrov, A.; Tioukov, V.

    2013-08-01

    Nuclear emulsions have been used in particle physics experiments for many decades because of their unique spatial resolution. The use of nuclear emulsions as precise tracking detectors in large experiments has recently been made possible due to advances in the production of emulsion films and to the development of very fast automatic scanning devices. The present scanning speed of the European Scanning System (ESS), which has been developed within the OPERA Collaboration, is about 20 cm2/h. In addition to the scanning of OPERA films, the ESS is used for other applications with ever-growing demands for scanning speed, such as the muon radiography of volcanoes. In order to further increase the scanning speed of the ESS, we are testing a novel approach different from the standard stop-and-go motion of the microscope stage in the horizontal plane. Indeed we perform data acquisition with the stage moving at constant speed, using an objective lens with wide field of view. Unlike the implementation realized in Japan where the movement of objective lens and stage are synchronized to pile up images of the same view in a vertical stack, in this approach only the stage is moving horizontally. Thus images at different depths are not fully overlapped and special care is needed in the reconstruction. This approach can give a substantial increase in the scanning speed, especially for thin emulsion layers and wide field of view. In this paper we demonstrate that, after applying special corrections, the emulsion data quality can be as good as with the standard stop-and-go approach. This technique allows to double the scanning speed of the ESS, bringing it to 40 cm2/h without any hardware modification.

  17. I Situ Electrochemical Scanning Tunneling Microscopy Study of Dealloying and Stress Corrosion Cracking of Copper - Alloys.

    NASA Astrophysics Data System (ADS)

    Chen, Jin-Syung Fred

    The mechanism of stress corrosion cracking (SCC) of Cu-30Au in 0.6 M NaCl was investigated by a series of experiments, in which samples were dealloyed (i.e., selective removal of copper atoms) by potentiostatic anodic polarization at zero applied stress (i) for varying lengths of time (10 seconds to 30 minutes) and then impact bent, and (ii) for 30 minutes followed by a period of time (5 seconds to 10 minutes) at the open circuit potential and then impact bent. The results indicate that dealloying at zero applied stress produces a surface porous layer that is capable, for a brief period of time (<= ~ 15 seconds), of inducing intergranular cleavage failure of the normally ductile FCC substrate. However, for time >15 seconds at open circuit potential, aging or coarsening reverses the ability of the surface layer to induce cleavage. In addition, samples were dealloyed and simultaneously stressed at various nominal values. At low values of applied stress, failure occurred by brittle intergranular cracking (IGSCC); and at high values of stress, failure occurred by brittle transgranular cracking (TGSCC). The results indicate that the mechanism of IGSCC is identical to that of TGSCC and can best be described by a modification of the "film-induced cleavage" model. The implication of the aging phenomenon to the film-induced cleavage model of stress corrosion cracking is also discussed. An electrochemical scanning tunneling microscope (ESTM) was built and used to study the in-situ dealloying process of thin-film Cu-Au alloys. Thin-films of Cu-75 at%Au alloy were prepared by thermal evaporation of the bulk alloy and deposition of the vapor onto heated mica. The surface structure of the thin film thus grown consists of terrace of well defined (111) planes separated by atomic height steps. The results from in-situ ESTM indicate that if applied potentials were lower than the critical potential (E_{rm c}), dissolution of Cu preferentially occurred at the low coordination sites

  18. Design and development of multi functional confocal laser scanning microscope with UV / VIS laser source

    NASA Astrophysics Data System (ADS)

    Kanai, Yoshikazu; Kanzaki, Yousuke; Wakaki, Moriaki; Takeyama, Norihide

    2005-08-01

    A high resolution Confocal Laser Scanning Microscope (CLSM) with UV / VIS light sources was developed as the first step of multi-functional microscope. The optical system is designed to optimize for both UV and VIS wavelengths. An UV laser is used to achieve higher resolution, and a VIS is for multi functions. A new objective lens specialized for this application was designed and fabricated. Specification of the lens and the optical system is NA:0.95, EFL:2.5mm, WD:1.5mm, Resolution:160nm and achromatic for two wavelengths of UV 325.0nm / VIS 632.8nm. Several specimens were characterized to check the performance of the system. Some optical materials under study were measured for evaluation, and interesting results could be obtained. Multi-functional measurements are being planed as a next step. This system will help the research of nano-structures, photonic-crystals and biology.

  19. Osteogenesis imperfecta lethal in infancy: case report and scanning electron microscopic studies of the deciduous teeth.

    PubMed

    Levin, L S; Rosenbaum, K N; Brady, J M; Dorst, J P

    1982-12-01

    Radiologic evaluation of the skeleton and scanning electron microscopic studies of the teeth were performed on an infant boy with a lethal osteogenesis imperfecta (OI) syndrome who died at 10 mo of pneumonia. The skeletal findings included ribs that were focally expanded by fracture calluses, flat vertebral bodies, and wide limb bones. On fractured tooth surfaces, the enamel and dentin were normal as was the dentin calcification front. Although microscopic abnormalities have been noted in teeth from previously reported infants with lethal OI, a few studies also report infants with normal teeth. These differences in dental findings may indicate heterogeneity in OI lethal in infancy. Results of our study indicate that, until the primary biochemical defects in the OI syndromes are elucidated, examination of teeth from other infants with lethal OI and detailed evaluation of other clinical and skeletal features will aid in delineating heterogeneity and variation in expression in lethal OI.

  20. Fabrication and characterization of solid-state nanopores using a field emission scanning electron microscope

    SciTech Connect

    Chang Hung; Iqbal, Samir M.; Stach, Eric A.; King, Alexander H.; Zaluzec, Nestor J.; Bashir, Rashid

    2006-03-06

    The fabrication of solid-state nanopores using the electron beam of a transmission electron microscope (TEM) has been reported in the past. Here, we report a similar method to fabricate solid-state nanopores using the electron source of a conventional field-emission scanning electron microscope (FESEM) instead. Micromachining was used to create initial pore diameters between 50 nm and 200 nm, and controlled pore shrinking to sub 10 nm diameters was performed subsequently during in situ processing in the FESEM. Noticeably, different shrinking behavior was observed when using irradiation from the electron source of the FESEM than the TEM. Unlike previous reports of TEM mediated pore shrinkage, the mechanism of pore shrinkage when using the FESEM could be a result of surface defects generated by radiolysis and subsequent motion of silicon atoms to the pore periphery.

  1. Visualization of microcrack anisotropy in granite affected by afault zone, using confocal laser scanning microscope

    SciTech Connect

    Onishi, Celia T.; Shimizu, Ichiko

    2004-01-02

    Brittle deformation in granite can generate a fracture system with different patterns. Detailed fracture analyses at both macroscopic and microscopic scales, together with physical property data from a drill-core, are used to classify the effects of reverse fault deformation in four domains: (1) undeformed granite, (2) fractured granite with cataclastic seams, (3) fractured granite from the damage zone, and (4) foliated cataclasite from the core of the fault. Intact samples from two orthogonal directions, horizontal (H) and vertical (V), from the four domains indicate a developing fracture anisotropy toward the fault, which is highly developed in the damage zone. As a specific illustration of this phenomenon, resin impregnation, using a confocal laser scanning microscope (CLSM) technique is applied to visualize the fracture anisotropy developed in the Toki Granite, Japan. As a result, microcrack networks have been observed to develop in H sections and elongate open cracks in V sections, suggesting that flow pathways can be determined by deformation.

  2. Fractal evaluation of drug amorphicity from optical and scanning electron microscope images

    NASA Astrophysics Data System (ADS)

    Gavriloaia, Bogdan-Mihai G.; Vizireanu, Radu C.; Neamtu, Catalin I.; Gavriloaia, Gheorghe V.

    2013-09-01

    Amorphous materials are metastable, more reactive than the crystalline ones, and have to be evaluated before pharmaceutical compound formulation. Amorphicity is interpreted as a spatial chaos, and patterns of molecular aggregates of dexamethasone, D, were investigated in this paper by using fractal dimension, FD. Images having three magnifications of D were taken from an optical microscope, OM, and with eight magnifications, from a scanning electron microscope, SEM, were analyzed. The average FD for pattern irregularities of OM images was 1.538, and about 1.692 for SEM images. The FDs of the two kinds of images are less sensitive of threshold level. 3D images were shown to illustrate dependence of FD of threshold and magnification level. As a result, optical image of single scale is enough to characterize the drug amorphicity. As a result, the OM image at a single scale is enough to characterize the amorphicity of D.

  3. Scanning electron microscope cathodoluminescence imaging of subgrain boundaries, twins and planar deformation features in quartz

    NASA Astrophysics Data System (ADS)

    Hamers, M. F.; Pennock, G. M.; Drury, M. R.

    2016-11-01

    The study of deformation features has been of great importance to determine deformation mechanisms in quartz. Relevant microstructures in both growth and deformation processes include dislocations, subgrains, subgrain boundaries, Brazil and Dauphiné twins and planar deformation features (PDFs). Dislocations and twin boundaries are most commonly imaged using a transmission electron microscope (TEM), because these cannot directly be observed using light microscopy, in contrast to PDFs. Here, we show that red-filtered cathodoluminescence imaging in a scanning electron microscope (SEM) is a useful method to visualise subgrain boundaries, Brazil and Dauphiné twin boundaries. Because standard petrographic thin sections can be studied in the SEM, the observed structures can be directly and easily correlated to light microscopy studies. In contrast to TEM preparation methods, SEM techniques are non-destructive to the area of interest on a petrographic thin section.

  4. Biological application of Compressed Sensing Tomography in the Scanning Electron Microscope

    NASA Astrophysics Data System (ADS)

    Ferroni, Matteo; Signoroni, Alberto; Sanzogni, Andrea; Masini, Luca; Migliori, Andrea; Ortolani, Luca; Pezza, Alessandro; Morandi, Vittorio

    2016-09-01

    The three-dimensional tomographic reconstruction of a biological sample, namely collagen fibrils in human dermal tissue, was obtained from a set of projection-images acquired in the Scanning Electron Microscope. A tailored strategy for the transmission imaging mode was implemented in the microscope and proved effective in acquiring the projections needed for the tomographic reconstruction. Suitable projection alignment and Compressed Sensing formulation were used to overcome the limitations arising from the experimental acquisition strategy and to improve the reconstruction of the sample. The undetermined problem of structure reconstruction from a set of projections, limited in number and angular range, was indeed supported by exploiting the sparsity of the object projected in the electron microscopy images. In particular, the proposed system was able to preserve the reconstruction accuracy even in presence of a significant reduction of experimental projections.

  5. Biological application of Compressed Sensing Tomography in the Scanning Electron Microscope

    PubMed Central

    Ferroni, Matteo; Signoroni, Alberto; Sanzogni, Andrea; Masini, Luca; Migliori, Andrea; Ortolani, Luca; Pezza, Alessandro; Morandi, Vittorio

    2016-01-01

    The three-dimensional tomographic reconstruction of a biological sample, namely collagen fibrils in human dermal tissue, was obtained from a set of projection-images acquired in the Scanning Electron Microscope. A tailored strategy for the transmission imaging mode was implemented in the microscope and proved effective in acquiring the projections needed for the tomographic reconstruction. Suitable projection alignment and Compressed Sensing formulation were used to overcome the limitations arising from the experimental acquisition strategy and to improve the reconstruction of the sample. The undetermined problem of structure reconstruction from a set of projections, limited in number and angular range, was indeed supported by exploiting the sparsity of the object projected in the electron microscopy images. In particular, the proposed system was able to preserve the reconstruction accuracy even in presence of a significant reduction of experimental projections. PMID:27646194

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

    SciTech Connect

    Imtiaz, Atif; Wallis, Thomas M.; Brubaker, Matt D.; Blanchard, Paul T.; Bertness, Kris A.; Sanford, Norman A.; Kabos, Pavel; Weber, Joel C.; Coakley, Kevin J.

    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.

  7. Performance and characterization of the prototype nm-scale spatial resolution scanning multilayer Laue lenses microscope

    NASA Astrophysics Data System (ADS)

    Nazaretski, E.; Kim, Jungdae; Yan, H.; Lauer, K.; Eom, D.; Shu, D.; Maser, J.; Pešić, Z.; Wagner, U.; Rau, C.; Chu, Y. S.

    2013-03-01

    Synchrotron based x-ray microscopy established itself as a prominent tool for noninvasive investigations in many areas of science and technology. Many facilities around the world routinely achieve sub-micrometer resolution with a few instruments capable of imaging with the spatial resolution better than 100 nm. With an ongoing effort to push the 2D/3D resolution down to 10 nm in the hard x-ray regime both fabrication of the nano-focusing optics and stability of a microscope become extremely challenging. In this work we present our approach to overcome technical challenges on the path towards high spatial resolution hard x-ray microscopy and demonstrate the performance of a scanning fluorescence microscope equipped with the multilayer Laue lenses focusing optics.

  8. Frequency-doubled Alexandrite laser for use in periodontology: a scanning electron microscopic investigation

    NASA Astrophysics Data System (ADS)

    Rechmann, Peter; Hennig, Thomas

    1996-12-01

    During prior studies it could be demonstrated that engaging a frequency double Alexandrite-laser allows a fast and strictly selective ablation of supra- and subgingival calculus. Furthermore, the removal of unstained microbial plaque was observed. First conclusions were drawn following light microscopic investigations on undecalcified sections of irradiated teeth. In the present study the cementum surface after irradiation with a frequency doubled Alexandrite-laser was observed by means of a scanning electron microscope. After irradiation sections of teeth were dried in alcohol and sputtered with gold. In comparison irradiated cementum surfaces of unerupted operatively removed wisdom teeth and tooth surfaces after the selective removal of calculus were investigated. A complete removal of calculus was observed as well as a remaining smooth surface of irradiated cementum.

  9. Flexible polygon-mirror based laser scanning microscope platform for multiphoton in-vivo imaging.

    PubMed

    Li, Y X; Gautam, V; Brüstle, A; Cockburn, I A; Daria, V R; Gillespie, C; Gaus, K; Alt, C; Lee, W M

    2017-02-06

    Commercial microscopy systems make use of tandem scanning i.e. either slow or fast scanning. We constructed, for the first time, an advanced control system capable of delivering a dynamic line scanning speed ranging from 2.7 kHz to 27 kHz and achieve variable frame rates from 5 Hz to 50 Hz (512 × 512). The dynamic scanning ability is digitally controlled by a new customized open-source software named PScan1.0. This permits manipulation of scanning rates either to gain higher fluorescence signal at slow frame rate without increasing laser power or increase frame rates to capture high speed events. By adjusting imaging speed from 40 Hz to 160 Hz, we capture a range of calcium waves and transient peaks from soma and dendrite of single fluorescence neuron (CAL-520AM). Motion artifacts arising from respiratory and cardiac motion in small animal imaging reduce quality of real-time images of single cells in-vivo. An image registration algorithm, integrated with PScan1.0, was shown to perform both real time and post-processed motion correction. The improvement is verified by quantification of blood flow rates. This work describes all the steps necessary to develop a high performance and flexible polygon-mirror based multiphoton microscope system for in-vivo biological imaging.

  10. Electron tomography of HEK293T cells using scanning electron microscope-based scanning transmission electron microscopy.

    PubMed

    You, Yun-Wen; Chang, Hsun-Yun; Liao, Hua-Yang; Kao, Wei-Lun; Yen, Guo-Ji; Chang, Chi-Jen; Tsai, Meng-Hung; Shyue, Jing-Jong

    2012-10-01

    Based on a scanning electron microscope operated at 30 kV with a homemade specimen holder and a multiangle solid-state detector behind the sample, low-kV scanning transmission electron microscopy (STEM) is presented with subsequent electron tomography for three-dimensional (3D) volume structure. Because of the low acceleration voltage, the stronger electron-atom scattering leads to a stronger contrast in the resulting image than standard TEM, especially for light elements. Furthermore, the low-kV STEM yields less radiation damage to the specimen, hence the structure can be preserved. In this work, two-dimensional STEM images of a 1-μm-thick cell section with projection angles between ±50° were collected, and the 3D volume structure was reconstructed using the simultaneous iterative reconstructive technique algorithm with the TomoJ plugin for ImageJ, which are both public domain software. Furthermore, the cross-sectional structure was obtained with the Volume Viewer plugin in ImageJ. Although the tilting angle is constrained and limits the resulting structural resolution, slicing the reconstructed volume generated the depth profile of the thick specimen with sufficient resolution to examine cellular uptake of Au nanoparticles, and the final position of these nanoparticles inside the cell was imaged.

  11. Influence of atomic tip structure on the intensity of inelastic tunneling spectroscopy data analyzed by combined scanning tunneling spectroscopy, force microscopy, and density functional theory

    NASA Astrophysics Data System (ADS)

    Okabayashi, Norio; Gustafsson, Alexander; Peronio, Angelo; Paulsson, Magnus; Arai, Toyoko; Giessibl, Franz J.

    2016-04-01

    Achieving a high intensity in inelastic scanning tunneling spectroscopy (IETS) is important for precise measurements. The intensity of the IETS signal can vary by up to a factor of 3 for various tips without an apparent reason accessible by scanning tunneling microscopy (STM) alone. Here, we show that combining STM and IETS with atomic force microscopy enables carbon monoxide front-atom identification, revealing that high IETS intensities for CO/Cu(111) are obtained for single-atom tips, while the intensity drops sharply for multiatom tips. Adsorption of the CO molecule on a Cu adatom [CO/Cu/Cu(111)] such that the molecule is elevated over the substrate strongly diminishes the tip dependence of IETS intensity, showing that an elevated position channels most of the tunneling current through the CO molecule even for multiatom tips, while a large fraction of the tunneling current bypasses the CO molecule in the case of CO/Cu(111).

  12. Origin of Symmetric Dimer Images of Si(001) Observed by Low-Temperature Scanning Tunneling Microscopy

    PubMed Central

    Ren, Xiao-Yan; Kim, Hyun-Jung; Niu, Chun-Yao; Jia, Yu; Cho, Jun-Hyung

    2016-01-01

    It has been a long-standing puzzle why buckled dimers of the Si(001) surface appeared symmetric below ~20 K in scanning tunneling microscopy (STM) experiments. Although such symmetric dimer images were concluded to be due to an artifact induced by STM measurements, its underlying mechanism is still veiled. Here, we demonstrate, based on a first-principles density-functional theory calculation, that the symmetric dimer images are originated from the flip-flop motion of buckled dimers, driven by quantum tunneling (QT). It is revealed that at low temperature the tunneling-induced surface charging with holes reduces the energy barrier for the flipping of buckled dimers, thereby giving rise to a sizable QT-driven frequency of the flip-flop motion. However, such a QT phenomenon becomes marginal in the tunneling-induced surface charging with electrons. Our findings provide an explanation for low-temperature STM data that exhibits apparent symmetric (buckled) dimer structure in the filled-state (empty-state) images. PMID:27292000

  13. Origin of Symmetric Dimer Images of Si(001) Observed by Low-Temperature Scanning Tunneling Microscopy.

    PubMed

    Ren, Xiao-Yan; Kim, Hyun-Jung; Niu, Chun-Yao; Jia, Yu; Cho, Jun-Hyung

    2016-06-13

    It has been a long-standing puzzle why buckled dimers of the Si(001) surface appeared symmetric below ~20 K in scanning tunneling microscopy (STM) experiments. Although such symmetric dimer images were concluded to be due to an artifact induced by STM measurements, its underlying mechanism is still veiled. Here, we demonstrate, based on a first-principles density-functional theory calculation, that the symmetric dimer images are originated from the flip-flop motion of buckled dimers, driven by quantum tunneling (QT). It is revealed that at low temperature the tunneling-induced surface charging with holes reduces the energy barrier for the flipping of buckled dimers, thereby giving rise to a sizable QT-driven frequency of the flip-flop motion. However, such a QT phenomenon becomes marginal in the tunneling-induced surface charging with electrons. Our findings provide an explanation for low-temperature STM data that exhibits apparent symmetric (buckled) dimer structure in the filled-state (empty-state) images.

  14. Combining mobile terrestrial laser scanning geometric and radiometric data to eliminate accessories in circular metro tunnels

    NASA Astrophysics Data System (ADS)

    Tan, Kai; Cheng, Xiaojun; Ju, Qiaoqiao

    2016-07-01

    Terrestrial laser scanning (TLS) is a noninvasive technique to monitor surface conditions and morphological characteristics of structures and has been successfully introduced to the regular inspection and maintenance of metro tunnels. To accurately analyze the deformation and structural conditions of a metro tunnel, nonliner points (e.g., outliers and accessories) should be detected and eliminated. Nevertheless, the accessories are attached very closely to the liner and cannot be thoroughly eliminated by three-dimensional (3D) geometric information. This study proposes to separate the liner and accessories by combining TLS geometric and radiometric information. A refitted mobile Faro Focus3D X330 system is used for data collection of a new-built metro tunnel in Hangzhou, China. The results show that the corrected intensity data are an effective physical criterion and a complementary data source to remove accessories that cannot be eliminated by geometric data. After the removal of accessories by geometric and radiometric data, the remaining liner points can accurately reflect the actual structural and deformation conditions of metro tunnels.

  15. Theory of scanning tunneling spectroscopy: from Kondo impurities to heavy fermion materials

    NASA Astrophysics Data System (ADS)

    Morr, Dirk K.

    2017-01-01

    Kondo systems ranging from the single Kondo impurity to heavy fermion materials present us with a plethora of unconventional properties whose theoretical understanding is still one of the major open problems in condensed matter physics. Over the last few years, groundbreaking scanning tunneling spectroscopy (STS) experiments have provided unprecedented new insight into the electronic structure of Kondo systems. Interpreting the results of these experiments—the differential conductance and the quasi-particle interference spectrum—however, has been complicated by the fact that electrons tunneling from the STS tip into the system can tunnel either into the heavy magnetic moment or the light conduction band states. In this article, we briefly review the theoretical progress made in understanding how quantum interference between these two tunneling paths affects the experimental STS results. We show how this theoretical insight has allowed us to interpret the results of STS experiments on a series of heavy fermion materials providing detailed knowledge of their complex electronic structure. It is this knowledge that is a conditio sine qua non for developing a deeper understanding of the fascinating properties exhibited by heavy fermion materials, ranging from unconventional superconductivity to non-Fermi-liquid behavior in the vicinity of quantum critical points.

  16. Size-dependent energy levels of InSb quantum dots measured by scanning tunneling spectroscopy.

    PubMed

    Wang, Tuo; Vaxenburg, Roman; Liu, Wenyong; Rupich, Sara M; Lifshitz, Efrat; Efros, Alexander L; Talapin, Dmitri V; Sibener, S J

    2015-01-27

    The electronic structure of single InSb quantum dots (QDs) with diameters between 3 and 7 nm was investigated using atomic force microscopy (AFM) and scanning tunneling spectroscopy (STS). In this size regime, InSb QDs show strong quantum confinement effects which lead to discrete energy levels on both valence and conduction band states. Decrease of the QD size increases the measured band gap and the spacing between energy levels. Multiplets of equally spaced resonance peaks are observed in the tunneling spectra. There, multiplets originate from degeneracy lifting induced by QD charging. The tunneling spectra of InSb QDs are qualitatively different from those observed in the STS of other III-V materials, for example, InAs QDs, with similar band gap energy. Theoretical calculations suggest the electron tunneling occurs through the states connected with L-valley of InSb QDs rather than through states of the Γ-valley. This observation calls for better understanding of the role of indirect valleys in strongly quantum-confined III-V nanomaterials.

  17. Scanning tunneling microscopy/spectroscopy of vortices in LiFeAs

    NASA Astrophysics Data System (ADS)

    Hanaguri, T.; Kitagawa, K.; Matsubayashi, K.; Mazaki, Y.; Uwatoko, Y.; Takagi, H.

    2012-06-01

    We investigate vortices in LiFeAs using scanning tunneling microscopy/spectroscopy. Zero-field tunneling spectra show two superconducting gaps without detectable spectral weight near the Fermi energy, evidencing fully gapped multiband superconductivity. We image vortices in a wide field range from 0.1 T to 11 T by mapping the tunneling conductance at the Fermi energy. A quasihexagonal vortex lattice at low field contains domain boundaries which consist of alternating vortices with unusual coordination numbers of 5 and 7. With increasing field, the domain boundaries become ill defined, resulting in a uniformly disordered vortex matter. Tunneling spectra taken at the vortex center are characterized by a sharp peak just below the Fermi energy, apparently violating particle-hole symmetry. The image of each vortex shows energy-dependent 4-fold anisotropy which may be associated with the anisotropy of the Fermi surface. The vortex radius shrinks with decreasing temperature and becomes smaller than the coherence length estimated from the upper critical field. This is direct evidence of the Kramer-Pesch effect expected in a clean superconductor.

  18. Theory of scanning tunneling spectroscopy: from Kondo impurities to heavy fermion materials.

    PubMed

    Morr, Dirk K

    2017-01-01

    Kondo systems ranging from the single Kondo impurity to heavy fermion materials present us with a plethora of unconventional properties whose theoretical understanding is still one of the major open problems in condensed matter physics. Over the last few years, groundbreaking scanning tunneling spectroscopy (STS) experiments have provided unprecedented new insight into the electronic structure of Kondo systems. Interpreting the results of these experiments-the differential conductance and the quasi-particle interference spectrum-however, has been complicated by the fact that electrons tunneling from the STS tip into the system can tunnel either into the heavy magnetic moment or the light conduction band states. In this article, we briefly review the theoretical progress made in understanding how quantum interference between these two tunneling paths affects the experimental STS results. We show how this theoretical insight has allowed us to interpret the results of STS experiments on a series of heavy fermion materials providing detailed knowledge of their complex electronic structure. It is this knowledge that is a conditio sine qua non for developing a deeper understanding of the fascinating properties exhibited by heavy fermion materials, ranging from unconventional superconductivity to non-Fermi-liquid behavior in the vicinity of quantum critical points.

  19. TRIASSIC: the Time-Resolved Industrial Alpha-Source Scanning Induced Current microscope

    NASA Astrophysics Data System (ADS)

    Pallone, Arthur

    Time-resolved ion beam induced current (TRIBIC) microscopy yields useful information such as carrier mobility and lifetimes in semiconductors and defect locations in devices; however, traditional TRIBIC uses large, expensive particle accelerators that require specialized training to operate and maintain. The time-resolved industrial alpha-source scanning induced current (TRIASSIC) microscope transforms TRIBIC by replacing the particle accelerator facility with an affordable, tabletop instrument suitable for use in research and education at smaller colleges and universities. I will discuss the development of, successes with, setbacks to and future directions for TRIASSIC.

  20. SLAM examination of solar cells and solar cell welds. [Scanning Laser Acoustic Microscope

    NASA Technical Reports Server (NTRS)

    Stella, P. M.; Vorres, C. L.; Yuhas, D. E.

    1981-01-01

    The scanning laser acoustic microscope (SLAM) has been evaluated for non-destructive examination of solar cells and interconnector bonds. Using this technique, it is possible to view through materials in order to reveal regions of discontinuity such as microcracks and voids. Of particular interest is the ability to evaluate, in a unique manner, the bonds produced by parallel gap welding. It is possible to not only determine the area and geometry of the bond between the tab and cell, but also to reveal any microcracks incurred during the welding. By correlating the SLAM results with conventional techniques of weld evaluation a more confident weld parameter optimization can be obtained.

  1. Resonance oscillation damping of a scanning microscope probe by a near-surface viscous liquid layer

    NASA Astrophysics Data System (ADS)

    Maslenikov, I. I.; Reshetov, N. V.

    2016-05-01

    Viscous liquid layer motion between a probe with a tip shaped as a paraboloid of revolution and a surface is considered for semicontact-mode operation of a scanning probe microscope. The presence of a viscous liquid layer leads to energy dissipation and is one of the factors responsible for the decrease in the probe oscillation amplitude. The Reynolds equation for viscous liquid motion is used to obtain an analytic solution to the problem. The formula derived for the loss is compared with experimental data obtained for probes and layers with various curvature radii and viscosities.

  2. Unveiling the Mysteries of Mars with a Miniaturized Variable Pressure Scanning Electron Microscope (MVP-SEM)

    NASA Technical Reports Server (NTRS)

    Edmunson, J.; Gaskin, J. A.; Doloboff, I. J.; Jerman, G.

    2017-01-01

    Development of a miniaturized scanning electron microscope that will utilize the martian atmosphere to dissipate charge during analysis continues. This instrument is expected to be used on a future rover or lander to answer fundamental Mars science questions. To identify the most important questions, a survey was taken at the 47th Lunar and Planetary Science Conference (LPSC). From the gathered information initial topics were identified for a SEM on the martian surface. These priorities are identified and discussed below. Additionally, a concept of operations is provided with the goal of maximizing the science obtained with the minimum amount of communication with the instrument.

  3. Electron channeling contrast imaging studies of nonpolar nitrides using a scanning electron microscope

    SciTech Connect

    Naresh-Kumar, G.; Kraeusel, S.; Bruckbauer, J.; Edwards, P. R.; Hourahine, B.; Trager-Cowan, C.; Mauder, C.; Heuken, M.; Wang, K. R.; Trampert, A.; Kalisch, H.; Vescan, A.; Giesen, C.; Day, A. P.

    2013-04-08

    Threading dislocations, stacking faults, and associated partial dislocations significantly degrade the optical and electrical properties of materials such as non-polar III-nitride semiconductor thin films. Stacking faults are generally difficult to detect and quantify with existing characterization techniques. We demonstrate the use of electron channeling contrast imaging in the scanning electron microscope to non-destructively reveal basal plane stacking faults terminated by partial dislocations in m-plane GaN and InGaN/GaN multiple quantum well structures grown on {gamma}-LiAlO{sub 2} by metal organic vapor phase epitaxy.

  4. Scanning-electron-microscope study of normal-impingement erosion of ductile metals

    NASA Technical Reports Server (NTRS)

    Brainard, W. A.; Salik, J.

    1980-01-01

    Scanning electron microscopy was used to characterize the erosion of annealed copper and aluminum surfaces produced by both single- and multiple-particle impacts. Macroscopic 3.2 mm diameter steel balls and microscopic, brittle erodant particles were projected by a gas gun system so as to impact at normal incidence at speeds up to 140 m/sec. During the impacts by the brittle erodant particles, at lower speeds the erosion behavior was similar to that observed for the larger steel balls. At higher velocities, particle fragmentation and the subsequent cutting by the radial wash of debris created a marked change in the erosion mechanism.

  5. The Scanning Electron Microscope As An Accelerator For The Undergraduate Advanced Physics Laboratory

    SciTech Connect

    Peterson, Randolph S.; Berggren, Karl K.; Mondol, Mark

    2011-06-01

    Few universities or colleges have an accelerator for use with advanced physics laboratories, but many of these institutions have a scanning electron microscope (SEM) on site, often in the biology department. As an accelerator for the undergraduate, advanced physics laboratory, the SEM is an excellent substitute for an ion accelerator. Although there are no nuclear physics experiments that can be performed with a typical 30 kV SEM, there is an opportunity for experimental work on accelerator physics, atomic physics, electron-solid interactions, and the basics of modern e-beam lithography.

  6. A practical method for the remote control of the scanning electron microscope.

    PubMed

    Yamada, Atsushi; Hirahara, Osamu; Tsuchida, Takayoshi; Sugano, Naoki; Date, Masaru

    2003-01-01

    We have developed a remote control system for the scanning electron microscope (SEM). It is called Web-SEM and can be accessed by anyone through the Web browser. It is not necessary to install special software to control the SEM. Because the operating performance changes with the amount of traffic on the Internet, we have connected the Web-SEM to a LAN/Internet in order to overcome this. We have checked the performance of the remote control operation and we were able to perform focus adjustment, stage movement, etc. over the Internet by improving the method of operation and image transfer.

  7. Scanning tunneling microscopy of atomically precise graphene nanoribbons exfoliated onto H:Si(100)

    NASA Astrophysics Data System (ADS)

    Radocea, Adrian; Mehdi Pour, Mohammad; Vo, Timothy; Shekhirev, Mikhail; Sinitskii, Alexander; Lyding, Joseph

    Atomically precise graphene nanoribbons (GNRs) are promising materials for next generation transistors due to their well-controlled bandgaps and the high thermal conductivity of graphene. The solution synthesis of graphene nanoribbons offers a pathway towards scalable manufacturing. While scanning tunneling microscopy (STM) can access size scales required for characterization, solvent residue increases experimental difficulty and precludes band-gap determination via scanning tunneling spectroscopy (STS). Our work addresses this challenge through a dry contact transfer method that cleanly transfers solution-synthesized GNRs onto H:Si(100) under UHV using a fiberglass applicator. The semiconducting silicon surface avoids problems with image charge screening enabling intrinsic bandgap measurements. We characterize the nanoribbons using STM and STS. For chevron GNRs, we find a 1.6 eV bandgap, in agreement with computational modeling, and map the electronic structure spatially with detailed spectra lines and current imaging tunneling spectroscopy. Mapping the electronic structure of graphene nanoribbons is an important step towards taking advantage of the ability to form atomically precise nanoribbons and finely tune their properties.

  8. High-speed imaging upgrade for a standard sample scanning atomic force microscope using small cantilevers

    SciTech Connect

    Adams, Jonathan D.; Nievergelt, Adrian; Erickson, Blake W.; Yang, Chen; Dukic, Maja; Fantner, Georg E.

    2014-09-15

    We present an atomic force microscope (AFM) head for optical beam deflection on small cantilevers. Our AFM head is designed to be small in size, easily integrated into a commercial AFM system, and has a modular architecture facilitating exchange of the optical and electronic assemblies. We present two different designs for both the optical beam deflection and the electronic readout systems, and evaluate their performance. Using small cantilevers with our AFM head on an otherwise unmodified commercial AFM system, we are able to take tapping mode images approximately 5–10 times faster compared to the same AFM system using large cantilevers. By using additional scanner turnaround resonance compensation and a controller designed for high-speed AFM imaging, we show tapping mode imaging of lipid bilayers at line scan rates of 100–500 Hz for scan areas of several micrometers in size.

  9. Scanning tunneling microscopy characterization of the geometric and electronic structure of hydrogen-terminated silicon surfaces

    NASA Technical Reports Server (NTRS)

    Kaiser, W. J.; Bell, L. D.; Hecht, M. H.; Grunthaner, F. J.

    1988-01-01

    Scanning tunneling microscopy (STM) methods are used to characterize hydrogen-terminated Si surfaces prepared by a novel method. The surface preparation method is used to expose the Si-SiO2 interface. STM images directly reveal the topographic structure of the Si-SiO2 interface. The dependence of interface topography on oxide preparation conditions observed by STM is compared to the results of conventional surface characterization methods. Also, the electronic structure of the hydrogen-terminated surface is studied by STM spectroscopy. The near-ideal electronic structure of this surface enables direct tunnel spectroscopy measurements of Schottky barrier phenomena. In addition, this method enables probing of semiconductor subsurface properties by STM.

  10. Dynamic probe of ZnTe(110) surface by scanning tunneling microscopy.

    PubMed

    Kanazawa, Ken; Yoshida, Shoji; Shigekawa, Hidemi; Kuroda, Shinji

    2015-02-01

    The reconstructed surface structure of the II-VI semiconductor ZnTe (110), which is a promising material in the research field of semiconductor spintronics, was studied by scanning tunneling microscopy/spectroscopy (STM/STS). First, the surface states formed by reconstruction by the charge transfer of dangling bond electrons from cationic Zn to anionic Te atoms, which are similar to those of IV and III-V semiconductors, were confirmed in real space. Secondly, oscillation in tunneling current between binary states, which is considered to reflect a conformational change in the topmost Zn-Te structure between the reconstructed and bulk-like ideal structures, was directly observed by STM. Third, using the technique of charge injection, a surface atomic structure was successfully fabricated, suggesting the possibility of atomic-scale manipulation of this widely applicable surface of ZnTe.

  11. Scanning tunneling spectroscopy of inhomogeneous electronic structure in monolayer and bilayer graphene on SiC

    NASA Astrophysics Data System (ADS)

    Brar, Victor W.; Zhang, Yuanbo; Yayon, Yossi; Ohta, Taisuke; McChesney, Jessica L.; Bostwick, Aaron; Rotenberg, Eli; Horn, Karsten; Crommie, Michael F.

    2007-09-01

    The authors present a scanning tunneling spectroscopy (STS) study of the local electronic structure of single and bilayer graphene grown epitaxially on a SiC(0001) surface. Low voltage topographic images reveal fine, atomic-scale carbon networks, whereas higher bias images are dominated by emergent spatially inhomogeneous large-scale structure similar to a carbon-rich reconstruction of SiC(0001). STS spectroscopy shows an ˜100meV gaplike feature around zero bias for both monolayer and bilayer graphene/SiC, as well as significant spatial inhomogeneity in electronic structure above the gap edge. Nanoscale structure at the SiC/graphene interface is seen to correlate with observed electronic spatial inhomogeneity. These results are relevant for potential devices involving electronic transport or tunneling in graphene/SiC.

  12. Measurement of shear strength for HOPG with scanning tunneling microscopy by thermal excitation method.

    PubMed

    Ding, X D; Wang, Y Z; Xiong, X M; Du, X S; Zhang, J X

    2012-04-01

    An experimental observation of force interactions in scanning tunneling microscopy (STM) is presented. A technique for measuring force interactions between a conventional STM probe and a sample by spectra analysis of its thermal fluctuations from tunneling current in STM is developed theoretically and experimentally. Thermally excited fluctuation of the STM probe is exactly discerned in air and then force gradient is determined from its corresponding eigen-frequency with a formula similar to that for a small-amplitude atomic force microscopy (AFM). The observed force interactions are consistent with forces in dynamic AFM. Shear strength of 7 GPa for highly oriented pyrolytic graphite (HOPG) under compressive stress is obtained from the experiment and using the elastic theory. We believe that this technique is of scientific significance as it enables accurate measurement of short-range force interactions at atomic scale under true STM conditions.

  13. Quantitative analysis of Scanning Tunneling Microscopy images for surface structure determination: Sulfur on Re(0001)

    SciTech Connect

    Ogletree, D.F.; Dunphy, J.C.; Salmeron, M.B.; Sautet, P. |

    1993-02-01

    Scanning Tunneling Microscopy (STM) images of adsorbed atoms and molecules on single crystal substrates provide important information on surface structure and order. In many cases images are interpreted qualitatively based on other information on the system. To obtain quantitative information, a theoretical analysis of the STM image is required. A new method of calculating STM images is presented that includes a full description of the STM tip and surface structure. This method is applied to experimental STM images of sulfur adsorbed on Re(0001). Effects of adsorption site, adsorbate geometry, tip composition and tunnel gap resistance on STM image contrast are analyzed. The chemical identity of tip apex atom and substrate subsurface structure are both shown to significantly affect STM image contrast.

  14. Novel control scheme for a high-speed metrological scanning probe microscope

    NASA Astrophysics Data System (ADS)

    Vorbringer-Dorozhovets, N.; Hausotte, T.; Manske, E.; Shen, J. C.; Jäger, G.

    2011-09-01

    Some time ago, an interferometer-based metrological scanning probe microscope (SPM) was developed at the Institute of Process Measurement and Sensor Technology of the Ilmenau University of Technology, Germany. The specialty of this SPM is the combined deflection detection system that comprises an interferometer and a beam deflection. Due to this system it is possible to simultaneously measure the displacement, bending and torsion of the probe (cantilever). The SPM is integrated into a nanopositioning and nanomeasuring machine (NPM machine) and allows measurements with a resolution of 0.1 nm over a range of 25 mm × 25 mm × 5 mm. Excellent results were achieved for measurements of calibrated step height and lateral standards and these results are comparable to the calibration values from the Physikalisch-Technische Bundesanstalt (PTB) (Dorozhovets N et al 2007 Proc. SPIE 6616 661624-1-7). The disadvantage was a low attainable scanning speed and accordingly large expenditure of time. Control dynamics and scanning speed are limited because of the high masses of the stage and corner mirror of the machine. For the vertical axis an additional high-speed piezoelectric drive is integrated in the SPM in order to increase the measuring dynamics. The movement of the piezoelectric drive is controlled and traceable measured by the interferometer. Hence, nonlinearity and hysteresis in the actuator do not affect the measurement. The outcome of this is an improvement of the bending control of the cantilever and much higher scan speeds of up to 200 µm s-1.

  15. Imaging inflammation in mouse colon using a rapid stage-scanning confocal fluorescence microscope

    NASA Astrophysics Data System (ADS)

    Saldua, Meagan A.; Olsovsky, Cory A.; Callaway, Evelyn S.; Chapkin, Robert S.; Maitland, Kristen C.

    2012-01-01

    Large area confocal microscopy may provide fast, high-resolution image acquisition for evaluation of tissue in pre-clinical studies with reduced tissue processing in comparison to histology. We present a rapid beam and stage-scanning confocal fluorescence microscope to image cellular and tissue features along the length of the entire excised mouse colon. The beam is scanned at 8,333 lines/sec by a polygon scanning mirror while the specimen is scanned in the orthogonal axis by a motorized translation stage with a maximum speed of 7 mm/sec. A single 1×60 mm2 field of view image spanning the length of the mouse colon is acquired in 10 s. Z-projection images generated from axial image stacks allow high resolution imaging of the surface of non-flat specimens. In contrast to the uniform size, shape, and distribution of colon crypts in confocal images of normal colon, confocal images of chronic bowel inflammation exhibit heterogeneous tissue structure with localized severe crypt distortion.

  16. Microscopic C-V measurements of SOI wafers by scanning capacitance microscopy

    NASA Astrophysics Data System (ADS)

    Ishida, T.; Yoshida, H.; Kishino, S.

    2004-07-01

    Scanning capacitance microscopy (SCM) has been applied to microscopic characterization of electrical properties of silicon-on-insulator (SOI) wafers. Two kinds of capacitance-voltage (C-V) methods have been proposed for separately characterizing the electrical properties of a gate oxide, an SOI layer, a buried oxide (BOX) layer, a Si substrate, and their interfaces: (i) a front-gate C-V method whereby the electrical properties of the gate oxide and front SOI (the gate oxide/SOI) interface can be characterized, and (ii) a back-gate C-V method for the characterization of the electrical properties of the BOX layer, back SOI (the BOX/SOI) interface, and the BOX/Si substrate interface. Furthermore, SCM images of the sampled SOI wafer have been obtained for visualizing the microscopic spatial distribution of electrical properties of SOI wafers by using the proposed C-V methods. These SCM images revealed the fluctuation in the oxide charges and interface traps. SCM has been demonstrated to be an effective tool for microscopic electrical characterization of SOI wafers.

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

    PubMed

    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.

  18. Atmospheric scanning electron microscope system with an open sample chamber: configuration and applications.

    PubMed

    Nishiyama, Hidetoshi; Koizumi, Mitsuru; Ogawa, Koji; Kitamura, Shinich; Konyuba, Yuji; Watanabe, Yoshiyuki; Ohbayashi, Norihiko; Fukuda, Mitsunori; Suga, Mitsuo; Sato, Chikara

    2014-12-01

    An atmospheric scanning electron microscope (ASEM) with an open sample chamber and optical microscope (OM) is described and recent developments are reported. In this ClairScope system, the base of the open sample dish is sealed to the top of the inverted SEM column, allowing the liquid-immersed sample to be observed by OM from above and by SEM from below. The optical axes of the two microscopes are aligned, ensuring that the same sample areas are imaged to realize quasi-simultaneous correlative microscopy in solution. For example, the cathodoluminescence of ZnO particles was directly demonstrated. The improved system has (i) a fully motorized sample stage, (ii) a column protection system in the case of accidental window breakage, and (iii) an OM/SEM operation system controlled by a graphical user interface. The open sample chamber allows the external administration of reagents during sample observation. We monitored the influence of added NaCl on the random motion of silica particles in liquid. Further, using fluorescence as a transfection marker, the effect of small interfering RNA-mediated knockdown of endogenous Varp on Tyrp1 trafficking in melanocytes was examined. A temperature-regulated titanium ASEM dish allowed the dynamic observation of colloidal silver nanoparticles as they were heated to 240°C and sintered.

  19. Excitation-scanning hyperspectral imaging system for microscopic and endoscopic applications

    NASA Astrophysics Data System (ADS)

    Mayes, Sam A.; Leavesley, Silas J.; Rich, Thomas C.

    2016-04-01

    Current microscopic and endoscopic technologies for cancer screening utilize white-light illumination sources. Hyper-spectral imaging has been shown to improve sensitivity while retaining specificity when compared to white-light imaging in both microscopy and in vivo imaging. However, hyperspectral imaging methods have historically suffered from slow acquisition times due to the narrow bandwidth of spectral filters. Often minutes are required to gather a full image stack. We have developed a novel approach called excitation-scanning hyperspectral imaging that provides 2-3 orders of magnitude increased signal strength. This reduces acquisition times significantly, allowing for live video acquisition. Here, we describe a preliminary prototype excitation-scanning hyperspectral imaging system that can be coupled with endoscopes or microscopes for hyperspectral imaging of tissues and cells. Our system is comprised of three subsystems: illumination, transmission, and imaging. The illumination subsystem employs light-emitting diode arrays to illuminate at different wavelengths. The transmission subsystem utilizes a unique geometry of optics and a liquid light guide. Software controls allow us to interface with and control the subsystems and components. Digital and analog signals are used to coordinate wavelength intensity, cycling and camera triggering. Testing of the system shows it can cycle 16 wavelengths at as fast as 1 ms per cycle. Additionally, more than 18% of the light transmits through the system. Our setup should allow for hyperspectral imaging of tissue and cells in real time.

  20. Design and calibration of a scanning force microscope for friction, adhesion, and contact potential studies

    NASA Astrophysics Data System (ADS)

    Koleske, D. D.; Lee, G. U.; Gans, B. I.; Lee, K. P.; DiLella, D. P.; Wahl, K. J.; Barger, W. R.; Whitman, L. J.; Colton, R. J.

    1995-09-01

    We present the design and calibration of a scanning force microscope which can be used to study friction, adhesion, and contact potential differences between the cantilever tip and surface. The microscope uses a modular design where the laser, cantilever/sample holder, reflecting mirror, and detector are mounted directly on an optical table. The laser, reflecting mirror, and detector are mounted on translation and rotation stages. With this design the components can be rearranged to calibrate the Z piezo motion as a function of applied voltage. Using the detector micrometers, the detector response (voltage-to-distance relationship) can be determined after each series of measurements. The cantilever/sample holder is constructed such that the components are material matched and thermally compensated from a common reference point. This design feature minimizes thermal drift of the instrument. The instrument can be used in a contact scanning mode where both normal and lateral deflections of the cantilever are measured. In addition, the instrument can be used in frictional force studies, force curve mapping of the surface, and contact potential measurements. We present examples of each, including a detailed account of the instrument design and calibration.