Science.gov

Sample records for scanning probe spectroscopy

  1. Scanning Probe Microscopy and Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wiesendanger, Roland

    1994-09-01

    Preface; List of acronyms; Introduction; Part I. Experimental Methods and Theoretical Background of Scanning Probe Microscopy and Spectroscopy: 1. Scanning tunnelling microscopy; 2. Scanning force microscopy; 3. Related scanning probe techniques; Part II. Applications of Scanning Probe Microscopy and Spectroscopy: 4. Condensed matter physics; 5. Chemistry; 6. Organic materials; 7. Metrology and standards; 8. Nanotechnology; References; Index.

  2. Scanning-probe Single-electron Capacitance Spectroscopy

    PubMed Central

    Walsh, Kathleen A.; Romanowich, Megan E.; Gasseller, Morewell; Kuljanishvili, Irma; Ashoori, Raymond; Tessmer, Stuart

    2013-01-01

    The integration of low-temperature scanning-probe techniques and single-electron capacitance spectroscopy represents a powerful tool to study the electronic quantum structure of small systems - including individual atomic dopants in semiconductors. Here we present a capacitance-based method, known as Subsurface Charge Accumulation (SCA) imaging, which is capable of resolving single-electron charging while achieving sufficient spatial resolution to image individual atomic dopants. The use of a capacitance technique enables observation of subsurface features, such as dopants buried many nanometers beneath the surface of a semiconductor material1,2,3. In principle, this technique can be applied to any system to resolve electron motion below an insulating surface. As in other electric-field-sensitive scanned-probe techniques4, the lateral spatial resolution of the measurement depends in part on the radius of curvature of the probe tip. Using tips with a small radius of curvature can enable spatial resolution of a few tens of nanometers. This fine spatial resolution allows investigations of small numbers (down to one) of subsurface dopants1,2. The charge resolution depends greatly on the sensitivity of the charge detection circuitry; using high electron mobility transistors (HEMT) in such circuits at cryogenic temperatures enables a sensitivity of approximately 0.01 electrons/Hz½ at 0.3 K 5. PMID:23929222

  3. Charge trapping in polymer transistors probed by terahertz spectroscopy and scanning probe potentiometry

    NASA Astrophysics Data System (ADS)

    Lloyd-Hughes, J.; Richards, T.; Sirringhaus, H.; Castro-Camus, E.; Herz, L. M.; Johnston, M. B.

    2006-09-01

    Terahertz time-domain spectroscopy and scanning probe potentiometry were used to investigate charge trapping in polymer field-effect transistors fabricated on a silicon gate. The hole density in the transistor channel was determined from the reduction in the transmitted terahertz radiation under an applied gate voltage. Prolonged device operation creates an exponential decay in the differential terahertz transmission, compatible with an increase in the density of trapped holes in the polymer channel. Taken in combination with scanning probe potentionmetry measurements, these results indicate that device degradation is largely a consequence of hole trapping, rather than of changes to the mobility of free holes in the polymer.

  4. Probing Transition Metal Dichalcogenide Monolayers and Heterostructures by Optical Spectroscopy and Scanning Tunneling Spectroscopy

    NASA Astrophysics Data System (ADS)

    Hill, Heather M.

    Atomically thin two-dimensional materials, such as graphene and semiconductor transition metal dichalcogenides (TMDCs), exhibit remarkable and desirable optical and electronic properties. This dissertation focuses on the excitonic properties of monolayer TMDCs taken first in isolation and then in contact with another material. We begin with a study of the exciton binding energy in two monolayer TMDCs, WS2 and MoS2. We observe excited states of the exciton by two dierent optical spectroscopy techniques: reflectance contrast and photoluminescence excitation (PLE) spectroscopy. We fit a hydrogenic model to the energies associated with the excited states and infer a binding energy, which is an order of magnitude higher than the bulk material. In the second half of this work, we study two types of two-dimensional vertical heterostructures. First, we investigate heterostructures composed of monolayer WS2 partially capped with graphene one to four layers thick. Using reflectance contrast to measure the spectral broadening of the excitonic features, we measure the decrease in the coherence lifetime of the exciton in WS2 due to charge and energy transfer when in contact with graphene. We then compare our results with the exciton lifetime in MoS 2/WS2 and MoSe2/WSe2 heterostructures. In TMDC/TMDC heterostructures, the decrease in exciton lifetime is twice that in WS2/graphene heterostructures and due predominantly to charge transfer between the layers. Finally, we probe the band alignment in MoS2/WS2 heterostructures using scanning tunneling microscopy (STM) and spectroscopy (STS). We confirm the monolayer band gaps and the predicted type II band alignment in the heterostructure. Drawing from all the research presented, we arrive at a favorable conclusion about the viability of TMDC based devices.

  5. Electron spin resonance scanning probe spectroscopy for ultrasensitive biochemical studies.

    PubMed

    Campbell, Jason P; Ryan, Jason T; Shrestha, Pragya R; Liu, Zhanglong; Vaz, Canute; Kim, Ji-Hong; Georgiou, Vasileia; Cheung, Kin P

    2015-01-01

    Electron spin resonance (ESR) spectroscopy's affinity for detecting paramagnetic free radicals, or spins, has been increasingly employed to examine a large variety of biochemical interactions. Such paramagnetic species are broadly found in nature and can be intrinsic (defects in solid-state materials systems, electron/hole pairs, stable radicals in proteins) or, more often, purposefully introduced into the material of interest (doping/attachment of paramagnetic spin labels to biomolecules of interest). Using ESR to trace the reactionary path of paramagnetic spins or spin-active proxy molecules provides detailed information about the reaction's transient species and the label's local environment. For many biochemical systems, like those involving membrane proteins, synthesizing the necessary quantity of spin-labeled biomolecules (typically 50 pmol to 100 pmol) is quite challenging and often limits the possible biochemical reactions available for investigation. Quite simply, ESR is too insensitive. Here, we demonstrate an innovative approach that greatly enhances ESR's sensitivity (>20000× improvement) by developing a near-field, nonresonant, X-band ESR spectrometric method. Sensitivity improvement is confirmed via measurement of 140 amol of the most common nitroxide spin label in a ≈593 fL liquid cell at ambient temperature and pressure. This experimental approach eliminates many of the typical ESR sample restrictions imposed by conventional resonator-based ESR detection and renders the technique feasible for spatially resolved measurements on a wider variety of biochemical samples. Thus, our approach broadens the pool of possible biochemical and structural biology studies, as well as greatly enhances the analytical power of existing ESR applications. PMID:25867553

  6. ZnO(0001) surfaces probed by scanning tunneling spectroscopy: Evidence for an inhomogeneous electronic structure

    NASA Astrophysics Data System (ADS)

    Dumont, J.; Hackens, B.; Faniel, S.; Mouthuy, P.-O.; Sporken, R.; Melinte, S.

    2009-09-01

    The stability of the polar Zn-terminated ZnO surface is probed by low-temperature scanning tunneling microscopy and scanning tunneling spectroscopy (STS). Surface states in the bandgap of ZnO are evidenced by STS and their presence is correlated with the local surface corrugation. Very defective surface regions are characterized by a bulk electronic structure showing a wide bandgap while nanometer-scale defect free regions exhibit a narrower bandgap and surface states. We also image atomically resolved (√3 ×√3 )R30° reconstructions on the defect-free areas.

  7. Ultrafast scanning probe microscopy

    SciTech Connect

    Botkin, D.; Weiss, S.; Ogletree, D.F.; Salmeron, M.; Chemla, D.S.

    1994-01-01

    The authors have developed a general technique which combines the temporal resolution of ultrafast laser spectroscopy with the spatial resolution of scanned probe microscopy (SPM). Using this technique with scanning tunneling microscopy (STM), they have obtained simultaneous 2 ps time resolution and 50 {angstrom} spatial resolution. This improves the time resolution currently attainable with STM by nine orders of magnitude. The potential of this powerful technique for studying ultrafast dynamical phenomena on surfaces with atomic resolution is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    PubMed

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

    2016-04-15

    The nanoscale optical response of surface plasmons in three-dimensional metallic nanostructures plays an important role in many nanotechnology applications, where precise spatial and spectral characteristics of plasmonic elements control device performance. Electron energy loss spectroscopy (EELS) and cathodoluminescence (CL) within a scanning transmission electron microscope have proven to be valuable tools for studying plasmonics at the nanoscale. Each technique has been used separately, producing three-dimensional reconstructions through tomography, often aided by simulations for complete characterization. Here we demonstrate that the complementary nature of the two techniques, namely that EELS probes beam-induced electronic excitations while CL probes radiative decay, allows us to directly obtain a spatially- and spectrally-resolved picture of the plasmonic characteristics of nanostructures in three dimensions. The approach enables nanoparticle-by-nanoparticle plasmonic analysis in three dimensions to aid in the design of diverse nanoplasmonic applications. PMID:26934391

  10. Imaging via complete cantilever dynamic detection: general dynamic mode imaging and spectroscopy in scanning probe microscopy.

    PubMed

    Somnath, Suhas; Collins, Liam; Matheson, Michael A; Sukumar, Sreenivas R; Kalinin, Sergei V; Jesse, Stephen

    2016-10-14

    We develop and implement a multifrequency spectroscopy and spectroscopic imaging mode, referred to as general dynamic mode (GDM), that captures the complete spatially- and stimulus dependent information on nonlinear cantilever dynamics in scanning probe microscopy (SPM). GDM acquires the cantilever response including harmonics and mode mixing products across the entire broadband cantilever spectrum as a function of excitation frequency. GDM spectra substitute the classical measurements in SPM, e.g. amplitude and phase in lock-in detection. Here, GDM is used to investigate the response of a purely capacitively driven cantilever. We use information theory techniques to mine the data and verify the findings with governing equations and classical lock-in based approaches. We explore the dependence of the cantilever dynamics on the tip-sample distance, AC and DC driving bias. This approach can be applied to investigate the dynamic behavior of other systems within and beyond dynamic SPM. GDM is expected to be useful for separating the contribution of different physical phenomena in the cantilever response and understanding the role of cantilever dynamics in dynamic AFM techniques. PMID:27607339

  11. Imaging via complete cantilever dynamic detection: General dynamic mode imaging and spectroscopy in scanning probe microscopy

    DOE PAGESBeta

    Somnath, Suhas; Collins, Liam; Matheson, Michael A.; Sukumar, Sreenivas R.; Kalinin, Sergei V.; Jesse, Stephen

    2016-09-08

    We develop and implement a multifrequency spectroscopy and spectroscopic imaging mode, referred to as general dynamic mode (GDM), that captures the complete spatially- and stimulus dependent information on nonlinear cantilever dynamics in scanning probe microscopy (SPM). GDM acquires the cantilever response including harmonics and mode mixing products across the entire broadband cantilever spectrum as a function of excitation frequency. GDM spectra substitute the classical measurements in SPM, e.g. amplitude and phase in lock-in detection. Here, GDM is used to investigate the response of a purely capacitively driven cantilever. We use information theory techniques to mine the data and verify themore » findings with governing equations and classical lock-in based approaches. We explore the dependence of the cantilever dynamics on the tip–sample distance, AC and DC driving bias. This approach can be applied to investigate the dynamic behavior of other systems within and beyond dynamic SPM. In conclusion, GDM is expected to be useful for separating the contribution of different physical phenomena in the cantilever response and understanding the role of cantilever dynamics in dynamic AFM techniques.« less

  12. Topographical and chemical microanalysis of surfaces with a scanning probe microscope and laser-induced breakdown spectroscopy

    PubMed

    Kossakovski; Beauchamp

    2000-10-01

    Spatially resolved chemical imaging is achieved by combining a fiber-optic scanning probe microscope with laser-induced breakdown spectroscopy in a single instrument, TOPOLIBS. Elemental composition of surfaces can be mapped and correlated with topographical data. The experiment is conducted in air with minimal sample preparation. In a typical experiment, surface topography is analyzed by scanning a sharp fiber-optic probe across the sample using shear force feedback. The probe is then positioned over a feature of interest and pulsed radiation is delivered to the surface using a nitrogen laser. The pulse vaporizes material from the surface and generates a localized plasma plume. Optical emission from the plume is analyzed with a compact UV/visible spectrometer. Ablation crater size is controlled by the amount of laser power coupled into the probe. Sampling areas with submicrometer dimensions are achieved by using reduced laser power. PMID:11028639

  13. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, Shimon; Chemla, Daniel S.; Ogletree, D. Frank; Botkin, David

    1995-01-01

    An ultrafast scanning probe microscopy method for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample.

  14. Ultrafast scanning probe microscopy

    DOEpatents

    Weiss, S.; Chemla, D.S.; Ogletree, D.F.; Botkin, D.

    1995-05-16

    An ultrafast scanning probe microscopy method is described for achieving subpicosecond-temporal resolution and submicron-spatial resolution of an observation sample. In one embodiment of the present claimed invention, a single short optical pulse is generated and is split into first and second pulses. One of the pulses is delayed using variable time delay means. The first pulse is then directed at an observation sample located proximate to the probe of a scanning probe microscope. The scanning probe microscope produces probe-sample signals indicative of the response of the probe to characteristics of the sample. The second pulse is used to modulate the probe of the scanning probe microscope. The time delay between the first and second pulses is then varied. The probe-sample response signal is recorded at each of the various time delays created between the first and second pulses. The probe-sample response signal is then plotted as a function of time delay to produce a cross-correlation of the probe sample response. In so doing, the present invention provides simultaneous subpicosecond-temporal resolution and submicron-spatial resolution of the sample. 6 Figs.

  15. Adsorbate-induced quantum Hall system probed by scanning tunneling spectroscopy combined with transport measurements

    SciTech Connect

    Masutomi, Ryuichi Okamoto, Tohru

    2015-06-22

    An adsorbate-induced quantum Hall system at the cleaved InSb surfaces is investigated in magnetic fields up to 14 T using low-temperature scanning tunneling microscopy and spectroscopy combined with transport measurements. We show that an enhanced Zeeman splitting in the Shubnikov-de Haas oscillations is explained by an exchange enhancement of spin splitting and potential disorder, both of which are obtained from the spatially averaged density of states (DOS). Moreover, the Altshuler–Aronov correlation gap is observed in the spatially averaged DOS at 0 T.

  16. Adaptive scanning probe microscopies

    SciTech Connect

    Swartzentruber, B.S.; Bouchard, A.M.; Osbourn, G.C.

    1997-02-01

    This work is comprised of two major sections. In the first section the authors develop multivariate image classification techniques to distinguish and identify surface electronic species directly from multiple-bias scanning tunneling microscope (STM) images. Multiple measurements at each site are used to distinguish and categorize inequivalent electronic or atomic species on the surface via a computerized classification algorithm. Then, comparison with theory or other suitably chosen experimental data enables the identification of each class. They demonstrate the technique by analyzing dual-polarity constant-current topographs of the Ge(111) surface. Just two measurements, negative- and positive-bias topography height, permit pixels to be separated into seven different classes. Labeling four of the classes as adatoms, first-layer atoms, and two inequivalent rest-atom sites, they find excellent agreement with the c(2 x 8) structure. The remaining classes are associated with structural defects and contaminants. This work represents a first step toward developing a general electronic/chemical classification and identification tool for multivariate scanning probe microscopy imagery. In the second section they report measurements of the diffusion of Si dimers on the Si(001) surface at temperatures between room temperature and 128 C using a novel atom-tracking technique that can resolve every diffusion event. The atom tracker employs lateral-positioning feedback to lock the STM probe tip into position above selected atoms with sub-Angstrom precision. Once locked the STM tracks the position of the atoms as they migrate over the crystal surface. By tracking individual atoms directly, the ability of the instrument to measure dynamic events is increased by a factor of {approximately} 1,000 over conventional STM imaging techniques.

  17. Fast photodynamics of azobenzene probed by scanning excited-state potential energy surfaces using slow spectroscopy

    PubMed Central

    Tan, Eric M. M.; Amirjalayer, Saeed; Smolarek, Szymon; Vdovin, Alexander; Zerbetto, Francesco; Buma, Wybren Jan

    2015-01-01

    Azobenzene, a versatile and polymorphic molecule, has been extensively and successfully used for photoswitching applications. The debate over its photoisomerization mechanism leveraged on the computational scrutiny with ever-increasing levels of theory. However, the most resolved absorption spectrum for the transition to S1(nπ*) has not followed the computational advances and is more than half a century old. Here, using jet-cooled molecular beam and multiphoton ionization techniques we report the first high-resolution spectra of S1(nπ*) and S2(ππ*). The photophysical characterization reveals directly the structural changes upon excitation and the timescales of dynamical processes. For S1(nπ*), we find that changes in the hybridization of the nitrogen atoms are the driving force that triggers isomerization. In combination with quantum chemical calculations we conclude that photoisomerization occurs along an inversion-assisted torsional pathway with a barrier of ~2 kcal mol−1. This methodology can be extended to photoresponsive molecular systems so far deemed non-accessible to high-resolution spectroscopy. PMID:25562840

  18. Fast photodynamics of azobenzene probed by scanning excited-state potential energy surfaces using slow spectroscopy.

    PubMed

    Tan, Eric M M; Amirjalayer, Saeed; Smolarek, Szymon; Vdovin, Alexander; Zerbetto, Francesco; Buma, Wybren Jan

    2015-01-01

    Azobenzene, a versatile and polymorphic molecule, has been extensively and successfully used for photoswitching applications. The debate over its photoisomerization mechanism leveraged on the computational scrutiny with ever-increasing levels of theory. However, the most resolved absorption spectrum for the transition to S1(nπ*) has not followed the computational advances and is more than half a century old. Here, using jet-cooled molecular beam and multiphoton ionization techniques we report the first high-resolution spectra of S1(nπ*) and S2(ππ*). The photophysical characterization reveals directly the structural changes upon excitation and the timescales of dynamical processes. For S1(nπ*), we find that changes in the hybridization of the nitrogen atoms are the driving force that triggers isomerization. In combination with quantum chemical calculations we conclude that photoisomerization occurs along an inversion-assisted torsional pathway with a barrier of ~2 kcal mol(-1). This methodology can be extended to photoresponsive molecular systems so far deemed non-accessible to high-resolution spectroscopy. PMID:25562840

  19. Scanning probe nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Dinelli, F.; Menozzi, C.; Baschieri, P.; Facci, P.; Pingue, P.

    2010-02-01

    The present paper reports on a novel lithographic approach at the nanoscale level, which is based on scanning probe microscopy (SPM) and nanoimprint lithography (NIL). The experimental set-up consists of an atomic force microscope (AFM) operated via software specifically developed for the purpose. In particular, this software allows one to apply a predefined external load for a given lapse of time while monitoring in real-time the relative distance between the tip and the sample as well as the normal and lateral force during the embossing process. Additionally, we have employed AFM tips sculptured by means of focused ion beam in order to create indenting tools of the desired shape. Anti-sticking layers can also be used to functionalize the tips if one needs to investigate the effects of different treatments on the indentation and de-molding processes. The lithographic capabilities of this set-up are demonstrated on a polystyrene NIL-patterned sample, where imprinted features have been obtained upon using different normal load values for increasing time intervals, and on a thermoplastic polymer film, where the imprint process has been monitored in real-time.

  20. Functional probes for scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Hasegawa, Yukio; Akiyama, Kotone; Hamada, Masayuki; Eguchi, Toyoaki; An, Toshu; Fujikawa, Yasunori; Sakurai, Toshio

    2008-03-01

    Inspite of importance of the probe in scanning probe microscopy (SPM), little attention was paid for the SPM probes for most of the measurements of SPM. We developed sharp metal-tip cantilevers with a typical curvature radius better than 5nm using focused ion beam (FIB) suitable for Kelvin probe force microscopy (KFM)^1. We obtained atomically resolved KFM images with an energy resolution less than 3meV with the probe^2. We also developed a glass-coated tungsten tip for synchrotron radiation-scanning tunneling microscopy with the FIB method^3 and obtained elementally resolved images in a resolution less than 20nm^4. We are now developing a precise atomic force microscope (AFM) lithography^5 with the FIB-milled tip attached to a quartz tuning fork controlled by noncontact AFM. We will present recent results of our AFM lithography, such as an Au line with a width of 20˜30 nm and characters drawn with Au nano dots on a Si surface. 1 K. Akiyama et al., RSI 76, 033705 (2005) 2 T. Eguchi, K. Akiyama et al., PRL 93, 266102 (2004) 3 K. Akiyama et al., RSI 76, 083711 (2005) 4 T. Eguchi, K. Akiyama et al., APL 89, 243119 (2006) 5 K. Akiyama et al., JP 61, 22 (2007).

  1. Band Alignment in MoS2/WS2 Transition Metal Dichalcogenide Heterostructures Probed by Scanning Tunneling Microscopy and Spectroscopy.

    PubMed

    Hill, Heather M; Rigosi, Albert F; Rim, Kwang Taeg; Flynn, George W; Heinz, Tony F

    2016-08-10

    Using scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS), we examine the electronic structure of transition metal dichalcogenide heterostructures (TMDCHs) composed of monolayers of MoS2 and WS2. STS data are obtained for heterostructures of varying stacking configuration as well as the individual monolayers. Analysis of the tunneling spectra includes the influence of finite sample temperature, yield information about the quasi-particle bandgaps, and the band alignment of MoS2 and WS2. We report the band gaps of MoS2 (2.16 ± 0.04 eV) and WS2 (2.38 ± 0.06 eV) in the materials as measured on the heterostructure regions and the general type II band alignment for the heterostructure, which shows an interfacial band gap of 1.45 ± 0.06 eV. PMID:27298270

  2. Functional Probes for Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Akiyama, Kotone; Eguchi, Toyoaki; An, Toshu; Fujikawa, Yasunori; Hasegawa, Yukio; Sakurai, Toshio

    2007-03-01

    For superior performance of scanning probe microscopy, we are working to fabricate functional probes. For Kelvin probe force microscopy, we fabricated a metal-tip cantilever by attaching a thin metal wire to a regular Si cantilever and milling it by focused ion beam (FIB)^1. By using the W tip with a curvature radius of 3.5 nm, we obtained the potential profile of Ge/Si(105) surface in atomic resolution with the energy resolution better than 3 meV^2. For synchrotron-radiation-light-irradiated scanning tunneling microscopy which aims at atomically resolved elemental analysis, we fabricated a glass-coated W tip using FIB^3. It is found that the glass coating blocks the unwanted secondary electrons, which come from large area of the sample, by a factor of 40 with respect to the case no coating. Using the tip to detect the electrons emitted just below the tip, we obtained element specific images with a spatial resolution better than 20 nm under the photo irradiation whose energy is just above the adsorption edge of the element^4. 1 K. Akiyama et al., RSI 76, 033705 (2005) 2 T. Eguchi, K. Akiyama et al., PRL 93, 266102 (2004) 3 K. Akiyama et al., RSI 76, 083711 (2005) 4 T. Eguchi, K. Akiyama et al., APL, in press

  3. On the pH Responsive, Charge Selective, Polymer Brush-Mediated Transport Probed by Traditional and Scanning Fluorescence Correlation Spectroscopy

    PubMed Central

    Daniels, C. R.; Tauzin, L. J.; Foster, E.; Advincula, R. C.; Landes, C. F.

    2013-01-01

    The complete and reversible charge-selective sequestration of fluorophores by a weak polyelectrolyte brush, poly(2-(dimethylamino) ethyl-methacrylate) (PDMAEMA) was demonstrated using Fluorescence Correlation Spectroscopy (FCS). The chemistry and thickness of the weak polyelectrolyte PDMAEMA was tuned reversibly between neutral and cationic polymer forms. Thus, by switching the pH successively, the brush architecture was tuned to selectively trap and release anionic dye probes, while continuously excluding cationic molecules. In addition, line-scan FCS was implemented and applied for the first time to a synthetic polymer system, and used to identify a new, slower diffusion time on the order of seconds for the sequestered anionic probe under acidic conditions. These results, which quantify the selective sequestration properties of the PDMAEMA brush, are important because they enable a better understanding of transport in polymers, and establish a spectroscopic means of evaluating materials with proposed applications in separations science, charge storage/release and environmental remediation. PMID:23092304

  4. On the pH-responsive, charge-selective, polymer-brush-mediated transport probed by traditional and scanning fluorescence correlation spectroscopy.

    PubMed

    Daniels, C R; Tauzin, L J; Foster, E; Advincula, R C; Landes, C F

    2013-04-25

    The complete and reversible charge-selective sequestration of fluorophores by a weak polyelectrolyte brush, poly(2-(dimethylamino)ethylmethacrylate) (PDMAEMA) was demonstrated using fluorescence correlation spectroscopy (FCS). The chemistry and thickness of the weak polyelectrolyte PDMAEMA was tuned reversibly between neutral and cationic polymer forms. Thus, by switching the pH successively, the brush architecture was tuned to selectively trap and release anionic dye probes while continuously excluding cationic molecules. In addition, line-scan FCS was implemented and applied for the first time to a synthetic polymer system and used to identify a new, slower diffusion time on the order of seconds for the sequestered anionic probe under acidic conditions. These results, which quantify the selective sequestration properties of the PDMAEMA brush, are important because they enable a better understanding of transport in polymers and establish a spectroscopic means of evaluating materials with proposed applications in separations science, charge storage/release, and environmental remediation. PMID:23092304

  5. The Effect of Electrode Coupling on Single Molecule Device Characteristics: An X-Ray Spectroscopy and Scanning Probe Microscopy Study

    NASA Astrophysics Data System (ADS)

    Batra, Arunabh

    This thesis studies electronic properties of molecular devices in the limiting cases of strong and weak electrode-molecule coupling. In these two limits, we use the complementary techniques of X-Ray spectroscopy and Scanning Tunneling Microscopy (STM) to understand the mechanisms for electrode-molecule bond formation, the energy level realignment due to metal-molecule bonds, the effect of coupling strength on single-molecule conductance in low-bias measurements, and the effect of coupling on transport under high-bias. We also introduce molecular designs with inherent asymmetries, and develop an analytical method to determine the effect of these features on high-bias conductance. This understanding of the role of electrode-molecule coupling in high-bias regimes enables us to develop a series of functional electronic devices whose properties can be predictably tuned through chemical design. First, we explore the weak electrode-molecule coupling regime by studing the interaction of two types of paracyclophane derivates that are coupled 'through-space' to underlying gold substrates. The two paracyclophane derivatives differ in the strength of their intramolecular through-space coupling. X-Ray photoemission spectroscopy (XPS) and Near-Edge X-ray Absorbance Fine Structure (NEXAFS) spectroscopy allows us to determine the orientation of both molecules; Resonant Photoemission Spectroscopy (RPES) then allows us to measure charge transfer time from molecule to metal for both molecules. This study provides a quantititative measure of charge transfer time as a function of through-space coupling strength. Next we use this understanding in STM based single-molecule current-voltage measurements of a series of molecules that couple through-space to one electrode, and through-bond to the other. We find that in the high-bias regime, these molecules respond differently depending on the direction of the applied field. This asymmetric response to electric field direction results in

  6. Ion Implantation with Scanning Probe Alignment

    SciTech Connect

    Persaud, A.; Liddle, J.A.; Schenkel, T.; Bokor, J.; Ivanov, Tzv.; Rangelow, I.W.

    2005-07-12

    We describe a scanning probe instrument which integrates ion beams with the imaging and alignment function of a piezo-resistive scanning probe in high vacuum. The beam passes through several apertures and is finally collimated by a hole in the cantilever of the scanning probe. The ion beam spot size is limited by the size of the last aperture. Highly charged ions are used to show hits of single ions in resist, and we discuss the issues for implantation of single ions.

  7. Integration of scanning probes and ion beams

    SciTech Connect

    Persaud, A.; Park, S.J.; Liddle, J.A.; Schenkel, T.; Bokor, J.; Rangelow, I.

    2005-03-30

    We report the integration of a scanning force microscope with ion beams. The scanning probe images surface structures non-invasively and aligns the ion beam to regions of interest. The ion beam is transported through a hole in the scanning probe tip. Piezoresistive force sensors allow placement of micromachined cantilevers close to the ion beam lens. Scanning probe imaging and alignment is demonstrated in a vacuum chamber coupled to the ion beam line. Dot arrays are formed by ion implantation in resist layers on silicon samples with dot diameters limited by the hole size in the probe tips of a few hundred nm.

  8. Dopant Diffusion and Activation in Silicon Nanowires Fabricated by ex Situ Doping: A Correlative Study via Atom-Probe Tomography and Scanning Tunneling Spectroscopy.

    PubMed

    Sun, Zhiyuan; Hazut, Ori; Huang, Bo-Chao; Chiu, Ya-Ping; Chang, Chia-Seng; Yerushalmi, Roie; Lauhon, Lincoln J; Seidman, David N

    2016-07-13

    Dopants play a critical role in modulating the electric properties of semiconducting materials, ranging from bulk to nanoscale semiconductors, nanowires, and quantum dots. The application of traditional doping methods developed for bulk materials involves additional considerations for nanoscale semiconductors because of the influence of surfaces and stochastic fluctuations, which may become significant at the nanometer-scale level. Monolayer doping is an ex situ doping method that permits the post growth doping of nanowires. Herein, using atom-probe tomography (APT) with subnanometer spatial resolution and atomic-ppm detection limit, we study the distributions of boron and phosphorus in ex situ doped silicon nanowires with accurate control. A highly phosphorus doped outer region and a uniformly boron doped interior are observed, which are not predicted by criteria based on bulk silicon. These phenomena are explained by fast interfacial diffusion of phosphorus and enhanced bulk diffusion of boron, respectively. The APT results are compared with scanning tunneling spectroscopy data, which yields information concerning the electrically active dopants. Overall, comparing the information obtained by the two methods permits us to evaluate the diffusivities of each different dopant type at the nanowire oxide, interface, and core regions. The combined data sets permit us to evaluate the electrical activation and compensation of the dopants in different regions of the nanowires and understand the details that lead to the sharp p-i-n junctions formed across the nanowire for the ex situ doping process. PMID:27351447

  9. Scanning Josephson spectroscopy on the atomic scale

    NASA Astrophysics Data System (ADS)

    Randeria, Mallika T.; Feldman, Benjamin E.; Drozdov, Ilya K.; Yazdani, Ali

    2016-04-01

    The Josephson effect provides a direct method to probe the strength of the pairing interaction in superconductors. By measuring the phase fluctuating Josephson current between a superconducting tip of a scanning tunneling microscope and a BCS superconductor with isolated magnetic adatoms on its surface, we demonstrate that the spatial variation of the pairing order parameter can be characterized on the atomic scale. This system provides an example where the local pairing potential suppression is not directly reflected in the spectra measured via quasiparticle tunneling. Spectroscopy with such superconducting tips also shows signatures of previously unexplored Andreev processes through individual impurity-bound Shiba states. The atomic resolution achieved here establishes scanning Josephson spectroscopy as a promising technique for the study of novel superconducting phases.

  10. Probe microscopy: Scanning below the cell surface

    NASA Astrophysics Data System (ADS)

    Sahin, Ozgur

    2008-08-01

    Conventional atomic force microscopy probes only the surface of specimens. A related technique called scanning near-field ultrasonic holography can now image nanoparticles buried below the surfaces of cells, which could prove useful in nanotoxicology.

  11. Open Source Scanning Probe Microscopy Control Software Package Gxsm

    SciTech Connect

    Zahl P.; Wagner, T.; Moller, R.; Klust, A.

    2009-08-10

    Gxsm is a full featured and modern scanning probe microscopy (SPM) software. It can be used for powerful multidimensional image/data processing, analysis, and visualization. Connected toan instrument, it is operating many different avors of SPM, e.g., scanning tunneling microscopy(STM) and atomic force microscopy (AFM) or in general two-dimensional multi channel data acquisition instruments. The Gxsm core can handle different data types, e.g., integer and oating point numbers. An easily extendable plug-in architecture provides many image analysis and manipulation functions. A digital signal processor (DSP) subsystem runs the feedback loop, generates the scanning signals and acquires the data during SPM measurements. The programmable Gxsm vector probe engine performs virtually any thinkable spectroscopy and manipulation task, such as scanning tunneling spectroscopy (STS) or tip formation. The Gxsm software is released under the GNU general public license (GPL) and can be obtained via the Internet.

  12. Creating and Probing Graphene Electron Optics with Local Scanning Probes

    NASA Astrophysics Data System (ADS)

    Stroscio, Joseph

    Ballistic propagation and the light-like dispersion of graphene charge carriers make graphene an attractive platform for optics-inspired graphene electronics where gate tunable potentials can control electron refraction and transmission. In analogy to optical wave propagation in lenses, mirrors and metamaterials, gate potentials can be used to create a negative index of refraction for Veselago lensing and Fabry-Pérot interferometers. In circular geometries, gate potentials can induce whispering gallery modes (WGM), similar to optical and acoustic whispering galleries albeit on a much smaller length scale. Klein scattering of Dirac carriers plays a central role in determining the coherent propagation of electron waves in these resonators. In this talk, I examine the probing of electron resonators in graphene confined by linear and circular gate potentials with the scanning tunneling microscope (STM). The tip in the STM tunnel junction serves both as a tunable local gate potential, and as a probe of the graphene states through tunneling spectroscopy. A combination of a back gate potential, Vg, and tip potential, Vb, creates and controls a circular pn junction that confines the WGM graphene states. The resonances are observed in two separate channels in the tunneling spectroscopy experiment: first, by directly tunneling into the state at the bias energy eVb, and, second, by tunneling from the resonance at the Fermi level as the state is gated by the tip potential. The second channel produces a fan-like set of WGM peaks, reminiscent of the fringes seen in planar geometries by transport measurements. The WGM resonances split in a small applied magnetic field, with a large energy splitting approaching the WGM spacing at 0.5 T. These results agree well with recent theory on Klein scattering in graphene electron resonators. This work is done in collaboration with Y. Zhao, J. Wyrick, F.D. Natterer, J. F. Rodriquez-Nieva, C. Lewandoswski, K. Watanabe, T. Taniguchi, N. B

  13. Soft stylus probes for scanning electrochemical microscopy.

    PubMed

    Cortés-Salazar, Fernando; Träuble, Markus; Li, Fei; Busnel, Jean-Marc; Gassner, Anne-Laure; Hojeij, Mohamad; Wittstock, Gunther; Girault, Hubert H

    2009-08-15

    A soft stylus microelectrode probe has been developed to carry out scanning electrochemical microscopy (SECM) of rough, tilted, and large substrates in contact mode. It is fabricated by first ablating a microchannel in a polyethylene terephthalate thin film and filling it with a conductive carbon ink. After curing the carbon track and lamination with a polymer film, the V-shaped stylus was cut thereby forming a probe, with the cross section of the carbon track at the tip being exposed either by UV-photoablation machining or by blade cutting followed by polishing to produce a crescent moon-shaped carbon microelectrode. The probe properties have been assessed by cyclic voltammetry, approach curves, and line scans over electrochemically active and inactive substrates of different roughness. The influence of probe bending on contact mode imaging was then characterized using simple patterns. Boundary element method simulations were employed to rationalize the distance-dependent electrochemical response of the soft stylus probes. PMID:19630394

  14. Scanning Probe Microscopy of Graphene

    NASA Astrophysics Data System (ADS)

    Tautz, Pamela

    2011-10-01

    Scanning tunneling microscopy has been used to study the unusual electronic properties of graphene. In an effort to support the graphene with minimal interaction with the substrate, we used a hexagonal boron nitride (hBN) substrate. To minimize contaminants between the CVD graphene and boron nitride, the graphene samples were cleaned with distilled water and isopropanol prior to transfer to hBN substrate. We have also examined the growth of graphene flakes by chemical vapor deposition. In particular, we examined the relationship between the orientations of the first and second layer of CVD grown graphene. We found the growth mechanism preferentially resulted in rotations of 9^o or less indicating flakes with first and second layers aligned.

  15. Scanning probe image wizard: A toolbox for automated scanning probe microscopy data analysis

    NASA Astrophysics Data System (ADS)

    Stirling, Julian; Woolley, Richard A. J.; Moriarty, Philip

    2013-11-01

    We describe SPIW (scanning probe image wizard), a new image processing toolbox for SPM (scanning probe microscope) images. SPIW can be used to automate many aspects of SPM data analysis, even for images with surface contamination and step edges present. Specialised routines are available for images with atomic or molecular resolution to improve image visualisation and generate statistical data on surface structure.

  16. 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.

  17. Probing many body effects using Fourier Transform Scanning Tunneling Spectroscopy: Can spin-orbit splitting in dispersion be observed in q-space?

    NASA Astrophysics Data System (ADS)

    Farahi, Gelareh; UBC Labortory for Atomic Imaging Research (LAIR)) Team

    Well studied surface systems such as Ag and Cu provide a safe platform to test novel spectroscopy methods that can have extended applications in near future. Our current focus is given to Fourier Transform Scanning Tunneling Spectroscopy (FT-STS) that allows us to study scattering effects (quasiparticle interactions - namely QPI) of CO and Co on Cu(111) surface. Magnetic Co adatoms are expected to generate a spin-orbit split in dispersion in QPI(q) space, the existence of which is confirmed by the k-space angle-resolved photo-emission spectroscopy (ARPES) of Cu(111) surface in the recent years. Hence the previously observed electron-phonon kink and spin-orbit splitting of the dispersion, as well as the scattering properties of CO molecules and Co adatoms, should also be observable in QPI space via FT-STS of Cu(111), and compatible with previous studies on similar systems. We are using a low temperature (4.2 K) commercial Scanning Tunneling Microscope (CREATEC STM) that operates using Nanonis electronic controllers and software which allows us to perform FT-STS as well as topological imaging.

  18. Nanotubes as nanoprobes in scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Dai, Hongjie; Hafner, Jason H.; Rinzler, Andrew G.; Colbert, Daniel T.; Smalley, Richard E.

    1996-11-01

    SINCE the invention of the scanning tunnelling microscope1, the value of establishing a physical connection between the macroscopic world and individual nanometre-scale objects has become increasingly evident, both for probing these objects2-4 and for direct manipulation5-7 and fabrication8-10 at the nanometre scale. While good progress has been made in controlling the position of the macroscopic probe of such devices to sub-ångström accuracy, and in designing sensitive detection schemes, less has been done to improve the probe tip itself4. Ideally the tip should be as precisely defined as the object under investigation, and should maintain its integrity after repeated use not only in high vacuum but also in air and water. The best tips currently used for scanning probe microscopy do sometimes achieve sub-nanometre resolution, but they seldom survive a 'tip crash' with the surface, and it is rarely clear what the atomic configuration of the tip is during imaging. Here we show that carbon nanotubes11,12 might constitute well defined tips for scanning probe microscopy. We have attached individual nanotubes several micrometres in length to the silicon cantilevers of conventional atomic force microscopes. Because of their flexibility, the tips are resistant to damage from tip crashes, while their slenderness permits imaging of sharp recesses in surface topography. We have also been able to exploit the electrical conductivity of nanotubes by using them for scanning tunnelling microscopy.

  19. High-resolution scanning hall probe microscopy

    NASA Astrophysics Data System (ADS)

    Hicks, Clifford; Luan, Lan; Hendrik Bluhm, J.; Moler, Kathryn; Guikema, Janice; Zeldov, Eli; Shtrikman, Hadas

    2006-03-01

    Scanning hall sensors can be used to directly image magnetic fields at surfaces. They offer high resolution, high sensitivity, operability over a broad temperature range, and linearity. We have fabricated hall sensors on GaAs / Al0.35Ga0.65As and GaAs / Al0.3Ga0.7As heterostructures containing 2D electron gases 40, 39 and 140nm beneath the surface. The sensitive areas of our probes range from microns to 85nm on a side. We report on the field sensitivities of probes of various sizes and their spatial resolution in a scanning configuration.

  20. 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.

  1. Vertically aligned nanostructure scanning probe microscope tips

    SciTech Connect

    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.

  2. Scanning probe microscopy on new dental alloys

    NASA Astrophysics Data System (ADS)

    Reusch, B.; Geis-Gerstorfer, J.; Ziegler, C.

    Surface analytical methods such as scanning force microscopy (SFM), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were used to determine the surface properties of amalgam substitutes as tooth filling materials. In particular the corrosion and the passivation behavior of new gallium restorative materials were studied. To give relevant practical data, the measurements were performed with and without the alloys being stored in artificial saliva to simulate physiological oral conditions.

  3. Improved controlled atmosphere high temperature scanning probe microscope

    NASA Astrophysics Data System (ADS)

    Hansen, K. V.; Wu, Y.; Jacobsen, T.; Mogensen, M. B.; Theil Kuhn, L.

    2013-07-01

    To locally access electrochemical active surfaces and interfaces in operando at the sub-micron scale at high temperatures in a reactive gas atmosphere is of great importance to understand the basic mechanisms in new functional materials, for instance, for energy technologies, such as solid oxide fuel cells and electrolyzer cells. Here, we report on advanced improvements of our original controlled atmosphere high temperature scanning probe microscope, CAHT-SPM. The new microscope can employ a broad range of the scanning probe techniques including tapping mode, scanning tunneling microscopy, scanning tunneling spectroscopy, conductive atomic force microscopy, and Kelvin probe force microscopy. The temperature of the sample can be as high as 850 °C. Both reducing and oxidizing gases such as oxygen, hydrogen, and nitrogen can be added in the sample chamber and the oxygen partial pressure (pO2) is monitored by an oxygen sensor. We present here some examples of its capabilities demonstrated by high temperature topography with simultaneously ac electrical conductance measurements during atmosphere changes, electrochemical impedance spectroscopy at various temperatures, and measurements of the surface potential. The improved CAHT-SPM, therefore, holds a great potential for local sub-micron analysis of high-temperature and gas induced changes of a wide range of materials.

  4. High-resolution scanning hall probe microscopy

    NASA Astrophysics Data System (ADS)

    Hicks, C. W.; Guikema, J. W.; Zeldov, E.

    2005-03-01

    Scanning hall sensors can be used to directly image magnetic fields at surfaces. They offer high resolution, high sensitivity, operability from cryogenic to room temperature, and linearity. We have fabricated hall sensors on GaAs / Al0.35Ga0.65As and GaAs / Al0.3Ga0.7As heterostructures, one containing a 2D electron gas 40 nanometers below the surface and another 140nm below the surface, as well as an In0.5Al0.5As / GaSb / AlSb / InAs heterostructure containing a 2DEG 21nm below the surface. The sensitive areas of our probes range from microns to 60nm on a side. We report on the field sensitivities of the probes and their spatial resolution in a scanning configuration.

  5. Intermittent contact hydration scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Aloisi, G.; Bacci, F.; Carlà, M.; Dolci, D.

    2010-07-01

    Hydration scanning probe microscopy is a technique similar to scanning tunneling microscopy, in which the probe current, sustained by the slight surface conduction of a thin hydration layer covering an insulating support surface, is essentially electrochemical in nature instead of electronic tunneling. Such a technique allows the imaging of a great variety of samples, including insulators, provided that they are hydrophilic, as well as the study of molecular samples of biological interest (such as DNA) fixed on a suitable supporting surface. The main problem to obtain stable and reproducible images comes from the very critical determination of the operating conditions under which the probe-hydration layer interaction does not lead to the formation of a relatively large water meniscus. It has been suggested that this issue can be removed by adding a high frequency oscillation to the probe movement, as in tapping atomic force microscopy. Meniscus formation and breakup have been investigated in order to determine the best values for the amplitude and the frequency of the oscillation. Results obtained in this mode are discussed in comparison with the usual continuous contact mode.

  6. "Un-annealed and Annealed Pd Ultra-Thin Film on SiC Characterized by Scanning Probe Microscopy and X-ray Photoelectron Spectroscopy"

    NASA Technical Reports Server (NTRS)

    Lu, W. J.; Shi, D. T.; Elshot, K.; Bryant, E.; Lafate, K.; Chen, H.; Burger, A.; Collins, W. E.

    1998-01-01

    Pd/SiC has been used as a hydrogen and a hydrocarbon gas sensor operated at high temperature. UHV (Ultra High Vacuum)-Scanning Tunneling Microscopy (STM), Atomic Force Microscopy (AFM) and X-ray Photoelectron Spectroscopy (XPS) techniques were applied to study the relationship between the morphology and chemical compositions for Pd ultra-thin films on SiC (less than 30 angstroms) at different annealing temperatures. Pd ultra-thin film on 6H-SiC was prepared by the RF sputtering method. The morphology from UHV-STM and AFM shows that the Pd thin film was well deposited on SiC substrate, and the Pd was partially aggregated to round shaped participates at an annealing temperature of 300 C. At 400 C, the amount of surface participates decreases, and some strap shape participates appear. From XPS, Pd2Si was formed on the surface after annealing at 300 C, and all Pd reacted with SiC to form Pd2Si after annealing at 400 C. The intensity of the XPS Pd peak decreases enormously at 400 C. The Pd film diffused into SiC, and the Schottky barrier height has almost no changes. The work shows the Pd sicilides/SiC have the same electronic properties with Pd/SiC, and explains why the Pd/SiC sensor still responds to hydrogen at high operating temperatures.

  7. Band excitation method applicable to scanning probe microscopy

    DOEpatents

    Jesse, Stephen [Knoxville, TN; Kalinin, Sergei V [Knoxville, TN

    2010-08-17

    Methods and apparatus are described for scanning probe microscopy. A method includes generating a band excitation (BE) signal having finite and predefined amplitude and phase spectrum in at least a first predefined frequency band; exciting a probe using the band excitation signal; obtaining data by measuring a response of the probe in at least a second predefined frequency band; and extracting at least one relevant dynamic parameter of the response of the probe in a predefined range including analyzing the obtained data. The BE signal can be synthesized prior to imaging (static band excitation), or adjusted at each pixel or spectroscopy step to accommodate changes in sample properties (adaptive band excitation). An apparatus includes a band excitation signal generator; a probe coupled to the band excitation signal generator; a detector coupled to the probe; and a relevant dynamic parameter extractor component coupled to the detector, the relevant dynamic parameter extractor including a processor that performs a mathematical transform selected from the group consisting of an integral transform and a discrete transform.

  8. Band excitation method applicable to scanning probe microscopy

    DOEpatents

    Jesse, Stephen; Kalinin, Sergei V

    2013-05-28

    Methods and apparatus are described for scanning probe microscopy. A method includes generating a band excitation (BE) signal having finite and predefined amplitude and phase spectrum in at least a first predefined frequency band; exciting a probe using the band excitation signal; obtaining data by measuring a response of the probe in at least a second predefined frequency band; and extracting at least one relevant dynamic parameter of the response of the probe in a predefined range including analyzing the obtained data. The BE signal can be synthesized prior to imaging (static band excitation), or adjusted at each pixel or spectroscopy step to accommodate changes in sample properties (adaptive band excitation). An apparatus includes a band excitation signal generator; a probe coupled to the band excitation signal generator; a detector coupled to the probe; and a relevant dynamic parameter extractor component coupled to the detector, the relevant dynamic parameter extractor including a processor that performs a mathematical transform selected from the group consisting of an integral transform and a discrete transform.

  9. Low cost PC based scanning Kelvin probe

    NASA Astrophysics Data System (ADS)

    Baikie, I. D.; Estrup, P. J.

    1998-11-01

    We have developed a novel, low cost, scanning Kelvin probe (SKP) system that can measure work function (wf) and surface potential (sp) topographies to within 1 meV energy resolution. The control and measurement subcomponents are PC based and incorporate a flexible user interface, permitting software control of major parameters and allowing easy user implementation via automatic setup and scanning procedures. We review the mode of operation and design features of the SKP including the digital oscillator, the compact ambient voice-coil head-stage, and signal processing techniques. This system offers unique tip-to-sample spacing control (to within 40 nm) which provides a method of simultaneously imaging sample height topographies and is essential to avoid spurious or "apparent" wf changes due to scanning-induced spacing changes. We illustrate SKP operation in generating high resolution wf/sp profiles of metal interfaces (as a tip characterization procedure) and operational electronic devices. The SKP potentially has a very wide range of applications ranging from semiconductor quality control thin film and surface analyses to corrosion and biopotential imaging.

  10. Piezoresistive sensors for scanning probe microscopy

    PubMed

    Gotszalk; Grabiec; Rangelow

    2000-02-01

    In this article we summarize the efforts devoted to the realization of our ideas of the development of piezoresistive sensor family used in scanning probe microscopy. All the sensors described here are fabricated based on advanced silicon micromachining and standard CMOS processing. The fabrication scenario presented in this article allows for the production of different sensors with the same tip deflection piezoresistive detection scheme. In this way we designed and fabricated, as a basic sensor, piezoresistive cantilever for atomic force microscopy, which enables surface topography measurements with a resolution of 0.1 nm. Next, by introducing a conductive tip isolated from the beam we obtained a microprobe for scanning capacitance microscopy and scanning tunneling microscopy. With this microprobe we measured capacitance between the microtip and the surface in the range of 10(-22) F. Furthermore, a modification of the piezoresistors placement, based on the finite element method (FEM) simulation permits fabrication of the multipurpose sensor for lateral force microscopy, which enables measurements of friction forces with a resolution of 1 nN. Finally, using the same basic device idea and only slightly modified process sequence we manufactured femtocalorimeter for the detection of heat energy in the range of 50 pJ. PMID:10741650

  11. Scanning Probe Microscopy of Organic Solar Cells

    NASA Astrophysics Data System (ADS)

    Reid, Obadiah G.

    Nanostructured composites of organic semiconductors are a promising class of materials for the manufacture of low-cost solar cells. Understanding how the nanoscale morphology of these materials affects their efficiency as solar energy harvesters is crucial to their eventual potential for large-scale deployment for primary power generation. In this thesis we describe the use of optoelectronic scanning-probe based microscopy methods to study this efficiency-structure relationship with nanoscale resolution. In particular, our objective is to make spatially resolved measurements of each step in the power conversion process from photons to an electric current, including charge generation, transport, and recombination processes, and correlate them with local device structure. We have achieved two aims in this work: first, to develop and apply novel electrically sensitive scanning probe microscopy experiments to study the optoelectronic materials and processes discussed above; and second, to deepen our understanding of the physics underpinning our experimental techniques. In the first case, we have applied conductive-, and photoconductive atomic force (cAFM & pcAFM) microscopy to measure both local photocurrent collection and dark charge transport properties in a variety of model and novel organic solar cell composites, including polymer/fullerene blends, and polymer-nanowire/fullerene blends, finding that local heterogeneity is the rule, and that improvements in the uniformity of specific beneficial nanostructures could lead to large increases in efficiency. We have used scanning Kelvin probe microscopy (SKPM) and time resolved-electrostatic force microscopy (trEFM) to characterize all-polymer blends, quantifying their sensitivity to photochemical degradation and the subsequent formation of local charge traps. We find that while trEFM provides a sensitive measure of local quantum efficiency, SKPM is generally unsuited to measurements of efficiency, less sensitive than tr

  12. Band Excitation in Scanning Probe Microscopy: Recognition and Functional Imaging

    SciTech Connect

    Jesse, Stephen; Vasudevan, Dr. Rama; Collins, Liam; Strelcov, Evgheni; Okatan, Mahmut B; Belianinov, Alex; Baddorf, Arthur P; Proksch, Roger; Kalinin, Sergei V

    2014-01-01

    Field confinement at the junction between a biased scanning probe microscope s (SPM) tip and solid surface enables local probing of various bias-induced transformations such as polarization switching, ionic motion, or electrochemical reactions to name a few. The nanoscale size of the biased region is smaller or comparable to features like grain boundaries and dislocations, potentially allows for the study of kinetics and thermodynamics at the level of a single defect. In contrast to classical statistically averaged approaches, this allows one to link structure to functionality and deterministically decipher associated mesoscopic and atomistic mechanisms. Furthermore, this type of information can serve as a fingerprint of local material functionality, allowing for local recognition imaging. Here, current progress in multidimensional SPM techniques based on band-excitation time and voltage spectroscopies is illustrated, including discussions on data acquisition, dimensionality reduction, and visualization along with future challenges and opportunities for the field.

  13. Scanned probe characterization of semiconductor nanostructures

    NASA Astrophysics Data System (ADS)

    Law, James Jeremy Macdonald

    Advances in the synthesis of materials and device structures have accentuated the need to understand nanoscale electronic structure and its implications. Scanning probe microscopy offers a rich variety of highly spatially accurate techniques that can further our understanding of the interactions that occur in nanoscale semiconductor materials and devices. The promising nitride semiconductor materials system suffers from perturbations in local electronic structure due to crystallographic defects. Understanding the electronic properties and physical origin of these defects can be invaluable in mitigating their impacts or eliminating them all together. In the second chapter of this dissertation, scanning capacitance microscopy (SCM) is used to characterize local electronic structure in alpha-plane n-type gallium nitride. Analysis reveals the presence of a linear, positively charged feature aligned along the [1¯100] direction which likely corresponds to a partial dislocation at the edge of a stacking fault. In the third chapter, conductive atomic force microscopy is used to determine the effects of Ga/N flux on the conductive behavior of reverse-bias leakage paths in gallium nitride grown by molecular beam epitaxy (MBE). Our data reveal a band of fluxes near Ga/N ≈ 1 for which these pathways cease to be observable. These observations suggest a method for controlling the primary source of reverse-bias Schottky contact leakage in n-type GaN grown by MBE. A deeper understanding of the interaction between macro-scale objects and nanoscale electronic properties is required to bring the exciting new possibilities that semiconductor nanowires offer to fruition. In the fourth chapter, SCM is used to examine the effects of micron-scale metal contacts on carrier modulation and electrostatic behavior in indium arsenide semiconductor nanowires. We interpret a pronounced dependence of capacitance spectra on distance between the probe tip and nanowire contact as a consequence of

  14. Time-resolved multiple probe spectroscopy

    SciTech Connect

    Greetham, G. M.; Sole, D.; Clark, I. P.; Parker, A. W.; Pollard, M. R.; Towrie, M.

    2012-10-15

    Time-resolved multiple probe spectroscopy combines optical, electronic, and data acquisition capabilities to enable measurement of picosecond to millisecond time-resolved spectra within a single experiment, using a single activation pulse. This technology enables a wide range of dynamic processes to be studied on a single laser and sample system. The technique includes a 1 kHz pump, 10 kHz probe flash photolysis-like mode of acquisition (pump-probe-probe-probe, etc.), increasing the amount of information from each experiment. We demonstrate the capability of the instrument by measuring the photolysis of tungsten hexacarbonyl (W(CO){sub 6}) monitored by IR absorption spectroscopy, following picosecond vibrational cooling of product formation through to slower bimolecular diffusion reactions on the microsecond time scale.

  15. Complete information acquisition in scanning probe microscopy

    SciTech Connect

    Belianinov, Alex; Kalinin, Sergei V.; Jesse, Stephen

    2015-03-13

    In the last three decades, scanning probe microscopy (SPM) has emerged as a primary tool for exploring and controlling the nanoworld. A critical part of the SPM measurements is the information transfer from the tip-surface junction to a macroscopic measurement system. This process reduces the many degrees of freedom of a vibrating cantilever to relatively few parameters recorded as images. Similarly, the details of dynamic cantilever response at sub-microsecond time scales of transients, higher-order eigenmodes and harmonics are averaged out by transitioning to millisecond time scale of pixel acquisition. Hence, the amount of information available to the external observer is severely limited, and its selection is biased by the chosen data processing method. Here, we report a fundamentally new approach for SPM imaging based on information theory-type analysis of the data stream from the detector. This approach allows full exploration of complex tip-surface interactions, spatial mapping of multidimensional variability of material s properties and their mutual interactions, and SPM imaging at the information channel capacity limit.

  16. Complete information acquisition in scanning probe microscopy

    DOE PAGESBeta

    Belianinov, Alex; Kalinin, Sergei V.; Jesse, Stephen

    2015-03-13

    In the last three decades, scanning probe microscopy (SPM) has emerged as a primary tool for exploring and controlling the nanoworld. A critical part of the SPM measurements is the information transfer from the tip-surface junction to a macroscopic measurement system. This process reduces the many degrees of freedom of a vibrating cantilever to relatively few parameters recorded as images. Similarly, the details of dynamic cantilever response at sub-microsecond time scales of transients, higher-order eigenmodes and harmonics are averaged out by transitioning to millisecond time scale of pixel acquisition. Hence, the amount of information available to the external observer ismore » severely limited, and its selection is biased by the chosen data processing method. Here, we report a fundamentally new approach for SPM imaging based on information theory-type analysis of the data stream from the detector. This approach allows full exploration of complex tip-surface interactions, spatial mapping of multidimensional variability of material s properties and their mutual interactions, and SPM imaging at the information channel capacity limit.« less

  17. 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…

  18. EDITORIAL: Scanning probe microscopy: a visionary development Scanning probe microscopy: a visionary development

    NASA Astrophysics Data System (ADS)

    Demming, Anna

    2013-07-01

    The development of scanning probe microscopy repositioned modern physics. When Rohrer and Binnig first used electronic tunnelling effects to image atoms and quantum states they did more than pin down theoretical hypotheses to real-world observables; the scanning tunnelling microscope fed imaginations, prompting researchers to consider new directions and possibilities [1]. As Rohrer once commented, 'We could show that you can easily manipulate or position something small in space with an accuracy of 10 pm.... When you can do that, you simply have ideas of what you can do' [2]. The development heralded a cavalry of scanning probe techniques—such as atomic force microscopy (AFM) [3-5], scanning near-field optical microscopy (SNOM) [6-8] and Kelvin probe force microscopy (KPFM) [9, 10]—that still continue to bring nanomaterials and nanoscale phenomena into fresh focus. Not long after the development of scanning tunnelling microscopy, Binnig, Quate and Gerber collaborating in California in the US published work on a new type of microscope also capable of atomic level resolution [3]. The original concept behind scanning tunnelling microscopy uses electrical conductance, which places substantial limitations on the systems that it can image. Binnig, Quate and Gerber developed the AFM to 'feel' the topology of surfaces like the needle of an old fashioned vinyl player. In this way insulators could be imaged as well. The development of a force modulation mode AFM extended the tool's reach to soft materials making images of biological samples accessible with the technique [4]. There have now been a number of demonstrations of image capture at rates that allow dynamics at the nanoscale to be tracked in real time, opening further possibilities in applications of the AFM as described in a recent review by Toshio Ando at Kanazawa University [5]. Researchers also found a way to retrieve optical information at 'super-resolution' [6, 7]. Optical microscopy provides spectral

  19. Analysis of scanning probe microscope images using wavelets.

    PubMed

    Gackenheimer, C; Cayon, L; Reifenberger, R

    2006-03-01

    The utility of wavelet transforms for analysis of scanning probe images is investigated. Simulated scanning probe images are analyzed using wavelet transforms and compared to a parallel analysis using more conventional Fourier transform techniques. The wavelet method introduced in this paper is particularly useful as an image recognition algorithm to enhance nanoscale objects of a specific scale that may be present in scanning probe images. In its present form, the applied wavelet is optimal for detecting objects with rotational symmetry. The wavelet scheme is applied to the analysis of scanning probe data to better illustrate the advantages that this new analysis tool offers. The wavelet algorithm developed for analysis of scanning probe microscope (SPM) images has been incorporated into the WSxM software which is a versatile freeware SPM analysis package. PMID:16439061

  20. Band excitation method applicable to scanning probe microscopy

    DOEpatents

    Jesse, Stephen; Kalinin, Sergei V.

    2015-08-04

    Scanning probe microscopy may include a method for generating a band excitation (BE) signal and simultaneously exciting a probe at a plurality of frequencies within a predetermined frequency band based on the excitation signal. A response of the probe is measured across a subset of frequencies of the predetermined frequency band and the excitation signal is adjusted based on the measured response.

  1. Position-Sensitive Scanning Fluorescence Correlation Spectroscopy

    PubMed Central

    Skinner, Joseph P.; Chen, Yan; Müller, Joachim D.

    2005-01-01

    Fluorescence correlation spectroscopy (FCS) uses a stationary laser beam to illuminate a small sample volume and analyze the temporal behavior of the fluorescence fluctuations within the stationary observation volume. In contrast, scanning FCS (SFCS) collects the fluorescence signal from a moving observation volume by scanning the laser beam. The fluctuations now contain both temporal and spatial information about the sample. To access the spatial information we synchronize scanning and data acquisition. Synchronization allows us to evaluate correlations for every position along the scanned trajectory. We use a circular scan trajectory in this study. Because the scan radius is constant, the phase angle is sufficient to characterize the position of the beam. We introduce position-sensitive SFCS (PSFCS), where correlations are calculated as a function of lag time and phase. We present the theory of PSFCS and derive expressions for diffusion, diffusion in the presence of flow, and for immobilization. To test PSFCS we compare experimental data with theory. We determine the direction and speed of a flowing dye solution and the position of an immobilized particle. To demonstrate the feasibility of the technique for applications in living cells we present data of enhanced green fluorescent protein measured in the nucleus of COS cells. PMID:15894645

  2. 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.

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

    PubMed

    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. PMID:23902073

  4. Scanned probe microscopy for thin film superconductor development

    SciTech Connect

    Moreland, J.

    1996-12-31

    Scanned probe microscopy is a general term encompassing the science of imaging based on piezoelectric driven probes for measuring local changes in nanoscale properties of materials and devices. Techniques like scanning tunneling microscopy, atomic force microscopy, and scanning potentiometry are becoming common tools in the production and development labs in the semiconductor industry. The author presents several examples of applications specific to the development of high temperature superconducting thin films and thin-film devices.

  5. Frequency-agile, rapid scanning spectroscopy

    NASA Astrophysics Data System (ADS)

    Truong, G.-W.; Douglass, K. O.; Maxwell, S. E.; van Zee, R. D.; Plusquellic, D. F.; Hodges, J. T.; Long, D. A.

    2013-07-01

    Challenging applications in trace gas measurements require low uncertainty and high acquisition rates. Many cavity-enhanced spectroscopies exhibit significant sensitivity and potential, but their scanning rates are limited by reliance on either mechanical or thermal frequency tuning. Here, we present frequency-agile, rapid scanning spectroscopy (FARS) in which a high-bandwidth electro-optic modulator steps a selected laser sideband to successive optical cavity modes. This approach involves no mechanical motion and allows for a scanning rate of 8 kHz per cavity mode, a rate that is limited only by the cavity response time itself. Unlike rapidly frequency-swept techniques, FARS does not reduce the measurement duty cycle, degrade the spectrum's frequency axis or require an unusual cavity configuration. FARS allows for a sensitivity of ~2 × 10-12 cm-1 Hz-1/2 and a tuning range exceeding 70 GHz. This technique shows promise for fast and sensitive trace gas measurements and studies of chemical kinetics.

  6. Three-dimensional Analysis of Nanomaterials by Scanning Probe Nanotomography

    NASA Astrophysics Data System (ADS)

    Efimov, Anton E.; Agapova, Olga I.; Mochalov, Konstantin E.; Agapov, Igor I.

    Micro and nanostructure of scaffolds made from fibroin of Bombyx mori silkworm by salt leaching technique was studied by scanning probe nanotomography. Nanopores with dimensions in range from 30 to 180 nm are observed in the scaffold volume. Three - dimensional analysis of obtained data shows that degree of scaffold nanoporosity is 0.5% and nanopores are not interconnected with each other. Usage of scanning probe nanotomography technique enables to obtain unique nanoscale information of 3D structure of biopolymer nanomaterials.

  7. Fabrication of all diamond scanning probes for nanoscale magnetometry.

    PubMed

    Appel, Patrick; Neu, Elke; Ganzhorn, Marc; Barfuss, Arne; Batzer, Marietta; Gratz, Micha; Tschöpe, Andreas; Maletinsky, Patrick

    2016-06-01

    The electronic spin of the nitrogen vacancy (NV) center in diamond forms an atomically sized, highly sensitive sensor for magnetic fields. To harness the full potential of individual NV centers for sensing with high sensitivity and nanoscale spatial resolution, NV centers have to be incorporated into scanning probe structures enabling controlled scanning in close proximity to the sample surface. Here, we present an optimized procedure to fabricate single-crystal, all-diamond scanning probes starting from commercially available diamond and show a highly efficient and robust approach for integrating these devices in a generic atomic force microscope. Our scanning probes consisting of a scanning nanopillar (200 nm diameter, 1-2 μm length) on a thin (<1 μm) cantilever structure enable efficient light extraction from diamond in combination with a high magnetic field sensitivity (ηAC≈50±20nT/Hz). As a first application of our scanning probes, we image the magnetic stray field of a single Ni nanorod. We show that this stray field can be approximated by a single dipole and estimate the NV-to-sample distance to a few tens of nanometer, which sets the achievable resolution of our scanning probes. PMID:27370455

  8. Fabrication of all diamond scanning probes for nanoscale magnetometry

    NASA Astrophysics Data System (ADS)

    Appel, Patrick; Neu, Elke; Ganzhorn, Marc; Barfuss, Arne; Batzer, Marietta; Gratz, Micha; Tschöpe, Andreas; Maletinsky, Patrick

    2016-06-01

    The electronic spin of the nitrogen vacancy (NV) center in diamond forms an atomically sized, highly sensitive sensor for magnetic fields. To harness the full potential of individual NV centers for sensing with high sensitivity and nanoscale spatial resolution, NV centers have to be incorporated into scanning probe structures enabling controlled scanning in close proximity to the sample surface. Here, we present an optimized procedure to fabricate single-crystal, all-diamond scanning probes starting from commercially available diamond and show a highly efficient and robust approach for integrating these devices in a generic atomic force microscope. Our scanning probes consisting of a scanning nanopillar (200 nm diameter, 1-2 μm length) on a thin (<1 μm) cantilever structure enable efficient light extraction from diamond in combination with a high magnetic field sensitivity ( η AC ≈ 50 ± 20 nT / √{ Hz } ). As a first application of our scanning probes, we image the magnetic stray field of a single Ni nanorod. We show that this stray field can be approximated by a single dipole and estimate the NV-to-sample distance to a few tens of nanometer, which sets the achievable resolution of our scanning probes.

  9. Remote adjustable focus Raman spectroscopy probe

    DOEpatents

    Schmucker, John E.; Blasi, Raymond J.; Archer, William B.

    1999-01-01

    A remote adjustable focus Raman spectroscopy probe allows for analyzing Raman scattered light from a point of interest external probe. An environmental barrier including at least one window separates the probe from the point of interest. An optical tube is disposed adjacent to the environmental barrier and includes a long working length compound lens objective next to the window. A beam splitter and a mirror are at the other end. A mechanical means is used to translated the prove body in the X, Y, and Z directions resulting in a variable focus optical apparatus. Laser light is reflected by the beam splitter and directed toward the compound lens objective, then through the window and focused on the point of interest. Raman scattered light is then collected by the compound lens objective and directed through the beam splitter to a mirror. A device for analyzing the light, such as a monochrometer, is coupled to the mirror.

  10. Scanning photoluminescent spectroscopy of bioconjugated quantum dots

    NASA Astrophysics Data System (ADS)

    Chornokur, G.; Ostapenko, S.; Oleynik, E.; Phelan, C.; Korsunska, N.; Kryshtab, T.; Zhang, J.; Wolcott, A.; Sellers, T.

    2009-04-01

    We report on the application of the bio-conjugated quantum dots (QDs) for a "sandwich" enzyme-linked immunosorbent assay (ELISA) cancer testing technique. Quantum dot ELISA detection of the cancer PSA antigen at concentrations as low as 0.01 ng/ml which is ˜50 times lower than the classic "sandwich" ELISA was demonstrated. Scanning photoluminescence (PL) spectroscopy was performed on dried ELISA wells and the results compared with the same QD samples dried on a solid substrate. We confirmed a "blue" up to 37 nm PL spectral shift in a case of QDs conjugated to PSA antibodies. Increasing of the "blue" spectral shift was observed at lower PSA antigen concentrations. The results can be used to improve sensitivity of "sandwich" ELISA cancer antigen detection.

  11. Quantification of thermal and contact resistances of scanning thermal probes

    SciTech Connect

    Kim, Kyeongtae E-mail: meyhofer@umich.edu Jeong, Wonho; Lee, Woochul; Sadat, Seid; Thompson, Dakotah; Meyhofer, Edgar E-mail: meyhofer@umich.edu; Reddy, Pramod E-mail: meyhofer@umich.edu

    2014-11-17

    Scanning thermal probes are widely used for imaging temperature fields with nanoscale resolution, for studying near-field radiative heat transport and for locally heating samples. In all these applications, it is critical to know the thermal resistance to heat flow within the probe and the thermal contact resistance between the probe and the sample. Here, we present an approach for quantifying the aforementioned thermal resistances using picowatt resolution heat flow calorimeters. The measured contact resistance is found to be in good agreement with classical predictions for thermal contact resistance. The techniques developed here are critical for quantitatively probing heat flows at the nanoscale.

  12. Micromachined photoplastic probe for scanning near-field optical microscopy

    NASA Astrophysics Data System (ADS)

    Genolet, G.; Despont, M.; Vettiger, P.; Staufer, U.; Noell, W.; de Rooij, N. F.; Cueni, T.; Bernal, M.-P.; Marquis-Weible, F.

    2001-10-01

    We present a hybrid probe for scanning near-field optical microscopy (SNOM), which consists of a micromachined photoplastic tip with a metallic aperture at the apex that is attached to an optical fiber, thus combining the advantages of optical fiber probes and micromachined tips. The tip and aperture are batch fabricated and assembled to a preetched optical fiber with micrometer centering precision. Rectangular apertures of 50 nm×130 nm have been produced without the need of any postprocessing. Topographical and optical imaging with a probe having an aperture of 300 nm demonstrate the great potential of the photoplastic probe for SNOM applications.

  13. Carbon nanotube scanning probe for imaging in aqueous environment

    NASA Technical Reports Server (NTRS)

    Stevens, Ramsey M.; Nguyen, Cattien V.; Meyyappan, M.

    2004-01-01

    Carbon nanotubes (CNTs) used as a probe for scanning probe microscopy has become one of the many potential usages of CNTs that is finding real applications in scientific research and industrial communities. It has been proposed that the unique mechanical buckling properties of the CNT would lessen the imaging force exerted on the sample and, thus, make CNT scanning probes ideal for imaging soft materials, including biological samples in liquid environments. The hydrophobic nature of the CNT graphitic sidewall is clearly chemically incompatible with the aqueous solution requirements in some biological imaging applications. In this paper, we present electron micrograph results demonstrating the instability of CNT scanning probes when submerged in aqueous solution. Moreover, we also introduce a novel approach to resolve this chemical incompatibility problem. By coating the CNT probe with ethylenediamine, thus rendering the CNT probe less hydrophobic, we demonstrate the liquid imaging capability of treated CNT probes. Experimental data for imaging in aqueous solutions are presented, which include an ultrathin Ir film and DNA molecules on a mica surface.

  14. Correcting nonlinear drift distortion of scanning probe and scanning transmission electron microscopies from image pairs with orthogonal scan directions.

    PubMed

    Ophus, Colin; Ciston, Jim; Nelson, Chris T

    2016-03-01

    Unwanted motion of the probe with respect to the sample is a ubiquitous problem in scanning probe and scanning transmission electron microscopies, causing both linear and nonlinear artifacts in experimental images. We have designed a procedure to correct these artifacts by using orthogonal scan pairs to align each measurement line-by-line along the slow scan direction, by fitting contrast variation along the lines. We demonstrate the accuracy of our algorithm on both synthetic and experimental data and provide an implementation of our method. PMID:26716724

  15. Tuning Localized Surface Plasmon Resonance in Scanning Near-Field Optical Microscopy Probes.

    PubMed

    Vasconcelos, Thiago L; Archanjo, Bráulio S; Fragneaud, Benjamin; Oliveira, Bruno S; Riikonen, Juha; Li, Changfeng; Ribeiro, Douglas S; Rabelo, Cassiano; Rodrigues, Wagner N; Jorio, Ado; Achete, Carlos A; Cançado, Luiz Gustavo

    2015-06-23

    A reproducible route for tuning localized surface plasmon resonance in scattering type near-field optical microscopy probes is presented. The method is based on the production of a focused-ion-beam milled single groove near the apex of electrochemically etched gold tips. Electron energy-loss spectroscopy and scanning transmission electron microscopy are employed to obtain highly spatially and spectroscopically resolved maps of the milled probes, revealing localized surface plasmon resonance at visible and near-infrared wavelengths. By changing the distance L between the groove and the probe apex, the localized surface plasmon resonance energy can be fine-tuned at a desired absorption channel. Tip-enhanced Raman spectroscopy is applied as a test platform, and the results prove the reliability of the method to produce efficient scattering type near-field optical microscopy probes. PMID:26027751

  16. Thermal Wave-Based Scanning Probe Microscopy and Its Applications

    NASA Astrophysics Data System (ADS)

    Pelzl, J.; Chirtoc, M.; Meckenstock, R.

    2013-09-01

    In the last two decades scanning thermal microscopes (SThM) with DC- and AC-heating have been developed offering resolutions down to the nanometer scale. The SThM is based on an atomic force microscope (AFM) that is equipped with a temperature sensitive nanoprobe. Most frequently a tip with a temperature-dependent electrical resistor is used which can be operated as a thermometer or as a heater. The lateral resolution of about 100 nm is determined by the tip radius. Alternatively, if the thermoelastic response is detected by a smaller AFM probe, a spatial resolution of about 10 nm can be attained. Thermal wave-based SThM-techniques (AC-SThM) are used (i) to control the thermal management of electronic devices and to image thermal parameters with submicron resolution and (ii) to study resonance absorption processes of optical, infrared, and microwave radiation on the nanometer scale. Examples presented comprise the thermal imaging of hot spots in high power and in-plane-gate transistors and local studies of the temperature dependence of the thermal conductivity of nano-structured NiTi shape memory alloys by the method. The use of the SThM as a tool for a spatially resolved spectroscopy is demonstrated by locally resolved ferromagnetic resonance measurements in thin iron and nickel films deposited on various substrates.

  17. 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.

  18. Non-Contact Measurement Using A Laser Scanning Probe

    NASA Astrophysics Data System (ADS)

    Modjarrad, Amir

    1989-03-01

    Traditional high accuracy touch-trigger probing can now be complemented by high speed, non-contact, profile scanning to give another "dimension" to the three-dimensional Co-ordinate Measuring Machines (CMMs). Some of the features of a specially developed laser scanning probe together with the trade-offs involved in the design of inspection systems that use triangulation are examined. Applications of such a laser probe on CMMs are numerous since high speed scanning allows inspection of many different components and surfaces. For example, car body panels, tyre moulds, aircraft wing skins, turbine blades, wax and clay models, plastics, etc. Other applications include in-process surveillance in manufacturing and food processing, robotics vision and many others. Some of these applications are discussed and practical examples, case studies and experimental results are given with particular reference to use on CMMs. In conclusion, future developments and market trends in high speed non-contact measurement are discussed.

  19. Optimization of Designs for Nanotube-based Scanning Probes

    NASA Technical Reports Server (NTRS)

    Harik, V. M.; Gates, T. S.; Bushnell, Dennis M. (Technical Monitor)

    2002-01-01

    Optimization of designs for nanotube-based scanning probes, which may be used for high-resolution characterization of nanostructured materials, is examined. Continuum models to analyze the nanotube deformations are proposed to help guide selection of the optimum probe. The limitations on the use of these models that must be accounted for before applying to any design problem are presented. These limitations stem from the underlying assumptions and the expected range of nanotube loading, end conditions, and geometry. Once the limitations are accounted for, the key model parameters along with the appropriate classification of nanotube structures may serve as a basis for the design optimization of nanotube-based probe tips.

  20. Fast and reliable method of conductive carbon nanotube-probe fabrication for scanning probe microscopy

    SciTech Connect

    Dremov, Vyacheslav Fedorov, Pavel; Grebenko, Artem; Fedoseev, Vitaly

    2015-05-15

    We demonstrate the procedure of scanning probe microscopy (SPM) conductive probe fabrication with a single multi-walled carbon nanotube (MWNT) on a silicon cantilever pyramid. The nanotube bundle reliably attached to the metal-covered pyramid is formed using dielectrophoresis technique from the MWNT suspension. It is shown that the dimpled aluminum sample can be used both for shortening/modification of the nanotube bundle by applying pulse voltage between the probe and the sample and for controlling the probe shape via atomic force microscopy imaging the sample. Carbon nanotube attached to cantilever covered with noble metal is suitable for SPM imaging in such modulation regimes as capacitance contrast microscopy, Kelvin probe microscopy, and scanning gate microscopy. The majority of such probes are conductive with conductivity not degrading within hours of SPM imaging.

  1. Fast and reliable method of conductive carbon nanotube-probe fabrication for scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Dremov, Vyacheslav; Fedoseev, Vitaly; Fedorov, Pavel; Grebenko, Artem

    2015-05-01

    We demonstrate the procedure of scanning probe microscopy (SPM) conductive probe fabrication with a single multi-walled carbon nanotube (MWNT) on a silicon cantilever pyramid. The nanotube bundle reliably attached to the metal-covered pyramid is formed using dielectrophoresis technique from the MWNT suspension. It is shown that the dimpled aluminum sample can be used both for shortening/modification of the nanotube bundle by applying pulse voltage between the probe and the sample and for controlling the probe shape via atomic force microscopy imaging the sample. Carbon nanotube attached to cantilever covered with noble metal is suitable for SPM imaging in such modulation regimes as capacitance contrast microscopy, Kelvin probe microscopy, and scanning gate microscopy. The majority of such probes are conductive with conductivity not degrading within hours of SPM imaging.

  2. Cantilevers with integrated organic LEDs for scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    An, Kwang Hyup; O'Connor, Brendan; Zhao, Yiying; Loh, William; Pipe, Kevin P.; Shtein, Max

    2007-02-01

    Organic thin films which are based on Van der Waals-bonded molecular organic compounds can be deposited onto a variety of substrates including scanning probe cantilevers without the lattice-matching constraints of conventional covalently-bonded semiconductors. Here we demonstrate organic light-emitting devices (OLEDs) fabricated on scanning probe cantilevers using thermal evaporation of molecular organic compounds and metallic electrodes. Ion beam lithography was used to define the emissive region in the shape of a ring having a diameter of 5 micrometers. The width of the ring emission was less than a micron as measured in the far field. Stable light emission was observed from the device at forward bias, with a current-voltage response similar to that of archetypal OLEDs. Such a probe can enable a new form of electrically-pumped SNOM compatible with existing atomic force microscopy tools and techniques. The emission wavelength can be tuned across the entire visible spectrum, including white light emission, by altering the composition of the emissive layer with a wide range of luminescent dyes. Should the ring-shaped light emission be used for imaging, the sample image can be deconvolved using a ring filter to achieve high resolution. The OLED probe can also be used to transfer excitons through the cathode to a sample via plasmon-assisted energy transfer; such a probe would be valuable for studying exciton dynamics in organic or organic/inorganic hybrid photovoltaic devices. By demonstrating the first active organic device on a scanning probe cantilever, this work opens the door to a wide range of new scanning probe techniques based on this class of materials for areas such as biological imaging.

  3. Handheld probes and galvanometer scanning for optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Duma, V.-F.; Dobre, G.; Demian, D.; Cernat, R.; Sinescu, C.; Topala, F. I.; Negrutiu, M. L.; Hutiu, Gh.; Bradu, A.; Rolland, J. P.; Podoleanu, A. G.

    2015-09-01

    As part of the ongoing effort of the biomedical imaging community to move Optical Coherence Tomography (OCT) systems from the lab to the clinical environment and produce OCT systems appropriate for multiple types of investigations in a medical department, handheld probes equipped with different types of scanners need to be developed. These allow different areas of a patient's body to be investigated using OCT with the same system and even without changing the patient's position. This paper reviews first the state of the art regarding OCT handheld probes. Novel probes with a uni-dimensional (1D) galvanometer-based scanner (GS) developed in our groups are presented. Their advantages and limitations are discussed. Aspects regarding the use of galvoscanners with regard to Micro-Electro- Mechanical Systems (MEMS) are pointed out, in relationship with our studies on optimal scanning functions of galvanometer devices in OCT. These scanning functions are briefly discussed with regard to their main parameters: profile, theoretical duty cycle, scan frequency, and scan amplitude. The optical design of the galvoscanner and refractive optics combination in the probe head, optimized for various applications, is considered. Perspectives of the field are pointed out in the final part of the paper.

  4. Endoscope two dimensional scanning fiber probe and the driving method

    NASA Astrophysics Data System (ADS)

    Li, Guangping; Gao, He; Zhou, Ai; Liu, Zhihai

    2011-11-01

    We design and fabricate an endoscope scanning fiber probe based on the piezoelectric transducer (PZT) for optical coherence tomography (OCT) to perform two-dimensional scanning. The driving part of the optical fiber probe is composed of two piezoelectric ceramics and a thin conductive substrate. The optical fiber is fixed in the middle of the piezoelectric ceramics to form a configuration of cantilever. A sine wave is employed for driving the PZT to make the cantilever vibrate along the vertical direction and form a line scanning. A saw tooth wave is load on the PZT to make the cantilever vibrate along the horizontal direction and form the field scanning. The frequency of the sine wave is set to be close to the resonance frequency of the fiber cantilever to increase the scanning range, whereas the frequency of the saw tooth wave is much lower than the resonance frequency to avoid the generation of blind spots. The finite element model is established for the theorical analysis of the device. Experimental results show that the scanning range can reach to 500x500 μm, and the scanning range can be adjusted by changing the amplitude of the drive signals.

  5. Massively Multiplexed Cantilever-free Scanning Probe Lithography

    NASA Astrophysics Data System (ADS)

    Brown, Keith A.; Eichelsdoerfer, Daniel J.; Shim, Wooyoung; Boya, Radha; Schmucker, Abrin L.; Liu, Guoliang; Mirkin, Chad A.

    2013-03-01

    Cantilever-free scanning probe lithography has emerged as a low-cost technique for rapidly patterning nanoscale materials. In this architecture, an array of probes is fabricated on a soft backing layer that provides mechanical compliance to each probe while an underlying hard surface maintains the structural integrity of the array. One drawback of this technique is that each probe in the array acts simultaneously and thus generates a copy of the same pattern. Here, we discuss recent efforts to incorporate heaters into these probe arrays so that when a given heater is activated, the thermal expansion of the elastomer actuates a single tip. We find thermal actuation to be powerful enough to actuate individual tips over 4 μm with minimal crosstalk, fast enough to actuate on relevant time scales (20 ms), and scalable by virtue of being electrically addressable. Furthermore, tuning the individual heaters allows for variability in the arrays to be compensated for precisely, resulting in high quality nanopatterning. The addition of tunable actuators transforms cantilever-free scanning probe lithography into a technique capable of true desktop nanofabrication.

  6. Plant cell wall characterization using scanning probe microscopy techniques

    PubMed Central

    Yarbrough, John M; Himmel, Michael E; Ding, Shi-You

    2009-01-01

    Lignocellulosic biomass is today considered a promising renewable resource for bioenergy production. A combined chemical and biological process is currently under consideration for the conversion of polysaccharides from plant cell wall materials, mainly cellulose and hemicelluloses, to simple sugars that can be fermented to biofuels. Native plant cellulose forms nanometer-scale microfibrils that are embedded in a polymeric network of hemicelluloses, pectins, and lignins; this explains, in part, the recalcitrance of biomass to deconstruction. The chemical and structural characteristics of these plant cell wall constituents remain largely unknown today. Scanning probe microscopy techniques, particularly atomic force microscopy and its application in characterizing plant cell wall structure, are reviewed here. We also further discuss future developments based on scanning probe microscopy techniques that combine linear and nonlinear optical techniques to characterize plant cell wall nanometer-scale structures, specifically apertureless near-field scanning optical microscopy and coherent anti-Stokes Raman scattering microscopy. PMID:19703302

  7. Cleaved thin-film probes for scanning tunneling microscopy.

    PubMed

    Siahaan, T; Kurnosikov, O; Barcones, B; Swagten, H J M; Koopmans, B

    2016-01-22

    We introduce an alternative type of probe for scanning tunneling microscopy (STM). Instead of using a needle-like tip made from a piece of metallic wire, a sharp-edged cleaved insulating substrate, which is initially covered by a thin conductive film, is used. The sharp tip is formed at the intersection of the two cleaved sides. Using this approach a variety of materials for STM probes can be used, and functionalization of STM probes is possible. The working principle of different probes made of metallic (Pt, Co, and CoB), indium-tin oxide, as well as Cu/Pt and Co/Pt multilayer films are demonstrated by STM imaging of clean Cu(001) and Cu(111) surfaces as well as the epitaxial Co clusters on Cu(111). PMID:26636763

  8. Single-molecule chemistry and physics explored by low-temperature scanning probe microscopy.

    PubMed

    Swart, Ingmar; Gross, Leo; Liljeroth, Peter

    2011-08-28

    It is well known that scanning probe techniques such as scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) routinely offer atomic scale information on the geometric and the electronic structure of solids. Recent developments in STM and especially in non-contact AFM have allowed imaging and spectroscopy of individual molecules on surfaces with unprecedented spatial resolution, which makes it possible to study chemistry and physics at the single molecule level. In this feature article, we first review the physical concepts underlying image contrast in STM and AFM. We then focus on the key experimental considerations and use selected examples to demonstrate the capabilities of modern day low-temperature scanning probe microscopy in providing chemical insight at the single molecule level. PMID:21584325

  9. Scanning probe lithography approach for beyond CMOS devices

    NASA Astrophysics Data System (ADS)

    Durrani, Zahid; Jones, Mervyn; Kaestner, Marcus; Hofer, Manuel; Guliyev, Elshad; Ahmad, Ahmad; Ivanov, Tzvetan; Zoellner, Jens-Peter; Rangelow, Ivo W.

    2013-03-01

    As present CMOS devices approach technological and physical limits at the sub-10 nm scale, a `beyond CMOS' information-processing technology is necessary for timescales beyond the semiconductor technology roadmap. This requires new approaches to logic and memory devices, and to associated lithographic processes. At the sub-5 nm scale, a technology platform based on a combination of high-resolution scanning probe lithography (SPL) and nano-imprint lithography (NIL) is regarded as a promising candidate for both resolution and high throughput production. The practical application of quantum-effect devices, such as room temperature single-electron and quantum-dot devices, then becomes feasible. This paper considers lithographic and device approaches to such a `single nanometer manufacturing' technology. We consider the application of scanning probes, capable of imaging, probing of material properties and lithography at the single nanometer scale. Modified scanning probes are used to pattern molecular glass based resist materials, where the small particle size (<1 nm) and mono-disperse nature leads to more uniform and smaller lithographic pixel size. We also review the current status of single-electron and quantum dot devices capable of room-temperature operation, and discuss the requirements for these devices with regards to practical application.

  10. Compact piezoelectric transducer fiber scanning probe for optical coherence tomography.

    PubMed

    Zhang, Ning; Tsai, Tsung-Han; Ahsen, Osman O; Liang, Kaicheng; Lee, Hsiang-Chieh; Xue, Ping; Li, Xingde; Fujimoto, James G

    2014-01-15

    We developed a compact, optical fiber scanning piezoelectric transducer (PZT) probe for endoscopic and minimally invasive optical coherence tomography (OCT). Compared with previous forward-mount fiber designs, we present a reverse-mount design that achieves a shorter rigid length. The fiber was mounted at the proximal end of a quadruple PZT tube and scanned inside the hollow PZT tube to reduce the probe length. The fiber resonant frequency was 338 Hz using a 17-mm-long fiber. A 0.9 mm fiber deflection was achieved with a driving amplitude of 35 V. Using a GRIN lens-based optical design with a 1.3× magnification, a ∼6 μm spot was scanned over a 1.2 mm diameter field. The probe was encased in a metal hypodermic tube with a ∼25 mm rigid length and covered with a 3.2 mm outer diameter (OD) plastic sheath. Imaging was performed with a swept source OCT system based on a Fourier domain modelocked laser (FDML) light source at a 240 kHz axial scan rate and 8 μm axial resolution (in air). En face OCT imaging of skin in vivo and human colon ex vivo was demonstrated. PMID:24562102

  11. Tip Based Nanofabrication Using Multi-mode Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Hu, Weihua

    Scanning probe microscopy (SPM) based nanotechnology is a promising technology in nano-device fabrication. It is able to both manipulate nanostructures and characterize the created nanopatterns using the nano-tip of the scanning probe on a mechanical basis or electrical basis. With the tip and device on similar scales, nano-tip based fabrication permits accurate control over the device geometry through tip manipulation with nanometer (or better) accuracy. However, SPM based nanofabrication is a slow process because the scanning velocity of the microscopy is low. Large, multi-tip arrays offer the possibility for parallel device fabrication, allowing mass fabrication with nanometer control. The goal of Tip-directed Field-emission Assisted Nanofabrication (TFAN) project was to realize parallel fabrication using our probe arrays. We started by fabricating nanodevice using one single probe. In this work, we investigated the study of fabricating single electron transistor (SET) using one single SPM probe. There were four stages we went through toward fabricating a SET. The first stage was to accomplish atomic-precision lithography in TFAN system. Atomic level lithography was achieved by desorbing hydrogen atoms, which were previously adsorbed to the Si(100)-2 × 1 surface, in ultrahigh vacuum scanning tunneling microscopy (UHV-STM). The second stage was to develop method for fabricating SET. SPM based local oxidation was chosen as the method to fabricate a SET on a thin titanium (Ti) film. A multi-mode SPM oxidation method was developed, in which both scanning tunneling microscopy (STM) mode and atomic microscopy (AFM) mode local oxidation were used to fabricated Ti-TiOx-Ti structures with the same conductive AFM probe. This multi-mode method enabled significantly fine feature size control by STM mode, working on insulating SiO2 substrates needed to isolate the device by AFM mode and in situ electrical characterization with conductive AFM mode. After developing the multi

  12. Integration of Ion Implantation with Scanning ProbeAlignment

    SciTech Connect

    Persaud, A.; Rangelow, I.W.; Schenkel, T.

    2005-03-01

    We describe a scanning probe instrument which integrates ion beams with imaging and alignment functions of a piezo resistive scanning probe in high vacuum. Energetic ions (1 to a few hundred keV) are transported through holes in scanning probe tips [1]. Holes and imaging tips are formed by Focused Ion Beam (FIB) drilling and ion beam assisted thin film deposition. Transport of single ions can be monitored through detection of secondary electrons from highly charged dopant ions (e. g., Bi{sup 45+}) enabling single atom device formation. Fig. 1 shows SEM images of a scanning probe tip formed by ion beam assisted Pt deposition in a dual beam FIB. Ion beam collimating apertures are drilled through the silicon cantilever with a thickness of 5 {micro}m. Aspect ratio limitations preclude the direct drilling of holes with diameters well below 1 {micro}m, and smaller hole diameters are achieved through local thin film deposition [2]. The hole in Fig. 1 was reduced from 2 {micro}m to a residual opening of about 300 nm. Fig. 2 shows an in situ scanning probe image of an alignment dot pattern taken with the tip from Fig. 1. Transport of energetic ions through the aperture in the scanning probe tip allows formation of arbitrary implant patterns. In the example shown in Fig. 2 (right), a 30 nm thick PMMA resist layer on silicon was exposed to 7 keV Ar{sup 2+} ions with an equivalent dose of 10{sup 14} ions/cm{sup 2} to form the LBL logo. An exciting goal of this approach is the placement of single dopant ions into precise locations for integration of single atom devices, such as donor spin based quantum computers [3, 4]. In Fig. 3, we show a section of a micron size dot area exposed to a low dose (10{sup 11}/cm{sup 2}) of high charge state dopant ions. The Bi{sup 45+} ions (200 keV) were extracted from a low emittance highly charged ions source [5]. The potential energy of B{sup 45+}, i. e., the sum of the binding energies required to remove the electrons, amounts to 36 ke

  13. Multifrequency scanning probe microscopy study of nanodiamond agglomerates

    NASA Astrophysics Data System (ADS)

    Aravind, Vasudeva; Lippold, Stephen; Li, Qian; Strelcov, Evgheny; Okatan, Baris; Legum, Benjamin; Kalinin, Sergei; Clarion University Team; Oak Ridge National Laboratory Team

    Due to their rich surface chemistry and excellent mechanical properties and non-toxic nature, nanodiamond particles have found applications such as biomedicine, tribology and lubrication, targeted drug delivery systems, tissue scaffolds and surgical implants. Although single nanodiamond particles have diameters about 4-5nm, they tend to form agglomerates. While these agglomerates can be useful for some purposes, many applications of nanodiamonds require single particle, disaggregated nanodiamonds. This work is oriented towards studying forces and interactions that contribute to agglomeration in nanodiamonds. In this work, using multifrequency scanning probe microscopy techniques, we show that agglomerate sizes can vary between 50-100nm in raw nanodiamonds. Extremeties of particles and Interfaces between agglomerates show dissipative forces with scanning probe microscope tip, indicating agglomerates could act as points of increased adhesion, thus reducing lubricating efficiency when nanodiamonds are used as lubricant additives. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  14. Quantum metrology with a scanning probe atom interferometer.

    PubMed

    Ockeloen, Caspar F; Schmied, Roman; Riedel, Max F; Treutlein, Philipp

    2013-10-01

    We use a small Bose-Einstein condensate on an atom chip as an interferometric scanning probe to map out a microwave field near the chip surface with a few micrometers resolution. With the use of entanglement between the atoms, our interferometer overcomes the standard quantum limit of interferometry by 4 dB and maintains enhanced performance for interrogation times up to 10 ms. This corresponds to a microwave magnetic field sensitivity of 77 pT/√Hz in a probe volume of 20 μm(3). Quantum metrology with entangled atoms is useful in measurements with high spatial resolution, since the atom number in the probe volume is limited by collisional loss. High-resolution measurements of microwave near fields, as demonstrated here, are important for the development of integrated microwave circuits for quantum information processing and applications in communication technology. PMID:24138235

  15. Tailored molecular glass resists for scanning probe lithography

    NASA Astrophysics Data System (ADS)

    Neuber, Christian; Schmidt, Hans-Werner; Strohriegl, Peter; Ringk, Andreas; Kolb, Tristan; Schedl, Andreas; Fokkema, Vincent; van Veghel, Marijn G. A.; Cooke, Mike; Rawlings, Colin; Dürig, Urs; Knoll, Armin; de Marneffe, Jean-François; el Otell, Ziad; Kaestner, Marcus; Krivoshapkina, Yana; Budden, Matthias; Rangelow, Ivo W.

    2015-03-01

    In the presented work solvent-free film preparation from tailored molecular glass resists, their thermal analysis, the characterization of etch resistance for plasma etching transfer processes, and the evaluation of the patterning performance using scanning probe lithography (SPL) tools, in particular electric field and thermal based SPL, are demonstrated. Therefore a series of fully aromatic spiro-based and tris-substituted twisted resist materials were systematically investigated. The materials feature very high glass transition temperatures of up to 173 °C, which allows solvent-free thin film preparation by physical vapor deposition (PVD) due to their high thermal stability. The PVD prepared films offer distinct advantages compared to spin coated films such as no pinholes, defects, or residual solvent domains, which can locally affect the film properties. In addition, PVD prepared films do not need a post apply bake (PAB) and can be precisely prepared in the nanometer range layer thickness. An observed sufficient plasma etching resistance is promising for an efficient pattern transfer even by utilizing only 10 nm thin resist films. Their lithographic resolution potential is demonstrated by a positive and a negative tone patterning using electric field, current controlled scanning probe lithography (EF-CC-SPL) at the Technical University of Ilmenau or thermal scanning probe lithography (tSPL) investigations at the IBM Research - Zurich. High resolution tSPL prepared patterns of 11 nm half pitch and at 4 nm patterning depth are demonstrated.

  16. Potential Applications of Scanning Probe Microscopy in Forensic Science

    NASA Astrophysics Data System (ADS)

    Watson, G. S.; Watson, J. A.

    2007-04-01

    The forensic community utilises a myriad of techniques to investigate a wide range of materials, from paint flakes to DNA. The various microscopic techniques have provided some of the greatest contributions, e.g., FT-IR (Fourier-transform infrared) microspectroscopy utilised in copy toner discrimination, multi-layer automobile paint fragment examination, etc, SEM-EDA (scanning electron microscopy with energy dispersive analysis) used to investigate glass fragments, fibers, and explosives, and SEM in microsampling for elemental analysis, just to name a few. This study demonstrates the ability of the Scanning Probe Microscope (SPM) to analyse human fingerprints on surfaces utilising a step-and-scan feature, enabling analysis of a larger field-of-view. We also extend a line crossings study by incorporating height analysis and surface roughness measurements. The study demonstrates the potential for SPM techniques to be utilised for forensic analysis which could complement the more traditional methodologies used in such investigations.

  17. Structurally induced FEES from nanotips: implications for scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia, N.; Binh, Vu Thien; Purcell, S. T.

    1993-08-01

    Recent theoretical studies and experimental data show the existence of energy levels at the apex atom of nanotips. We report here experimental measurements, by field emission electron spectroscopy (FEES), of strong modifications of the local density of states for varying atomic configurations of the nanotips. The local density of states specific to each protrusion must then be considered in interpreting scanning tunneling microscopy and scanning tunneling spectroscopy experiments with atomic resolution instead of the commonly used free-electron model.

  18. Structurally induced FEES from nanotips: implications for scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Garcia, N.; Binh, Vu Thien; Purcell, S. T.

    Recent theoretical studies and experimental data show the existence of energy levels the apex atom of nanotips. We report here experimental measurements, by field emission electron spectroscopy (FEES), of strong modifications of the local density of states for varying atomic configurations of the nanotips. The local density of states specific to each protrusion must then be considered in interpreting scanning tunneling microscopy and scanning tunneling spectroscopy experiments with atomic resolution instead of the commonly used free-electron model.

  19. Three-axis positional drift correction in scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Follin, Nathan D.; Musalo, Christopher J.; Trawick, Matthew L.

    2011-03-01

    Positional drift in scanning probe microscopy can cause image distortion and metrological errors of tens of nanometers or more. It can arise from thermal drift, due to thermal expansion of materials in the sample and microscope while scanning, or from piezo creep, particularly along the z axis. We present a technique for correcting positional drift errors in all three axes. Our method works by comparing each scanned topographical image to a second, partial scan, taken immediately afterwards, on which the fast and slow scan axes have been reversed. We model the positional distortion as a low-order polynomial function in three dimensions, searching for the set of correctional coefficients that minimizes the difference between the two scans. Using this technique we have successfully reduced positional errors from 50 nm to 0.5 nm in the z axis, and from 40 nm to 2 nm (about half of a single pixel) in the xy plane. Supported by an award from Research Corporation for Science Advancement, and by the American Chemical Society Petroleum Research Fund through Grant number 46380-GB7.

  20. Thermal scanning probe microscopy in the development of pharmaceuticals.

    PubMed

    Dai, Xuan; Moffat, Jonathan G; Wood, John; Reading, Mike

    2012-04-01

    The ability to characterize the physical and chemical properties of dosage forms is crucial to a more complete understanding of how vehicles for drug delivery behave and therefore how effective they are. Spatially resolved characterization that enables the visualization of properties on the nanoscale is particularly powerful. The usefulness of scanning probe microscopy (SPM) in the field of drug delivery is becoming increasingly well established and the use of thermal probes offers new capabilities thus enabling SPM to provide more and sometimes unique information. One type of measurement enabled by thermal probes is determining transition temperatures by means of local thermal analysis. The ability to identify and characterize materials in this way has found applications in characterizing a wide range of dosage forms. A complimentary thermal probe technique is photothermal infrared microspectroscopy (PTMS). PTMS offers a variety of advantages over more conventional approaches including the ability analyze compacts without the need for thin sections. It is also able to achieve sub-micron spatial resolution. Thermal probe techniques can characterize pharmaceutical dosage forms in terms of their physical properties and their chemical composition. PMID:21856345

  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. PMID:27107628

  2. Low-Temperature Scanning Capacitance Probe for Imaging Electron Motion

    NASA Astrophysics Data System (ADS)

    Bhandari, S.; Westervelt, R. M.

    2014-12-01

    Novel techniques to probe electronic properties at the nanoscale can shed light on the physics of nanoscale devices. In particular, studying the scattering of electrons from edges and apertures at the nanoscale and imaging the electron profile in a quantum dot, have been of interest [1]. In this paper, we present the design and implementation of a cooled scanning capacitance probe that operates at liquid He temperatures to image electron waves in nanodevices. The conducting tip of a scanned probe microscope is held above the nanoscale structure, and an applied sample-to-tip voltage creates an image charge that is measured by a cooled charge amplifier [2] adjacent to the tip. The circuit is based on a low-capacitance, high- electron-mobility transistor (Fujitsu FHX35X). The input is a capacitance bridge formed by a low capacitance pinched-off HEMT transistor and tip-sample capacitance. We have achieved low noise level (0.13 e/VHz) and high spatial resolution (100 nm) for this technique, which promises to be a useful tool to study electronic behavior in nanoscale devices.

  3. Pump-Probe Noise Spectroscopy of Molecular Junctions.

    PubMed

    Ochoa, Maicol A; Selzer, Yoram; Peskin, Uri; Galperin, Michael

    2015-02-01

    The slow response of electronic components in junctions limits the direct applicability of pump-probe type spectroscopy in assessing the intramolecular dynamics. Recently the possibility of getting information on a sub-picosecond time scale from dc current measurements was proposed. We revisit the idea of picosecond resolution by pump-probe spectroscopy from dc measurements and show that any intramolecular dynamics not directly related to charge transfer in the current direction is missed by current measurements. We propose a pump-probe dc shot noise spectroscopy as a suitable alternative. Numerical examples of time-dependent and average responses of junctions are presented for generic models. PMID:26261965

  4. Combined fiber probe for fluorescence lifetime and Raman spectroscopy

    PubMed Central

    Dochow, Sebastian; Ma, Dinglong; Latka, Ines; Bocklitz, Thomas; Hartl, Brad; Bec, Julien; Fatakdawala, Hussain; Marple, Eric; Urmey, Kirk; Wachsmann-Hogiu, Sebastian; Schmitt, Michael; Marcu, Laura; Popp, Jürgen

    2016-01-01

    In this contribution we present a dual modality fiber optic probe combining fluorescence lifetime imaging (FLIm) and Raman spectroscopy for in vivo endoscopic applications. The presented multi-spectroscopy probe enables efficient excitation and collection of fluorescence lifetime signals for FLIm in the UV/visible wavelength region, as well as of Raman spectra in the near-IR for simultaneous Raman/FLIm imaging. The probe was characterized in terms of its lateral resolution and distance dependency of the Raman and FLIm signals. In addition, the feasibility of the probe for in vivo FLIm and Raman spectral characterization of tissue was demonstrated. PMID:26093843

  5. Cone penetrometer fiber optic raman spectroscopy probe assembly

    DOEpatents

    Kyle, Kevin R.; Brown, Steven B.

    2000-01-01

    A chemically and mechanically robust optical Raman spectroscopy probe assembly that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

  6. Cone penetrometer fiber optic Raman spectroscopy probe assembly

    SciTech Connect

    Kyle, K.R.; Brown, S.B.

    2000-01-25

    A chemically and mechanically robust optical Raman spectroscopy probe assembly is described that can be incorporated in a cone penetrometer (CPT) for subsurface deployment. This assembly consists of an optical Raman probe and a penetrometer compatible optical probe housing. The probe is intended for in-situ chemical analysis of chemical constituents in the surrounding environment. The probe is optically linked via fiber optics to the light source and the detection system at the surface. A built-in broadband light source provides a strobe method for direct measurement of sample optical density. A mechanically stable sapphire window is sealed directly into the side-wall of the housing using a metallic, chemically resistant, hermetic seal design. This window permits transmission of the interrogation light beam and the resultant signal. The spectroscopy probe assembly is capable of accepting Raman, Laser induced Fluorescence, reflectance, and other optical probes with collimated output for CPT deployment.

  7. Metallized Capillaries as Probes for Raman Spectroscopy

    NASA Technical Reports Server (NTRS)

    Pelletier, Michael

    2003-01-01

    A class of miniature probes has been proposed to supplant the fiber-optic probes used heretofore in some Raman and fluorescence spectroscopic systems. A probe according to the proposal would include a capillary tube coated with metal on its inside to make it reflective. A microlens would be hermetically sealed onto one end of the tube. A spectroscopic probe head would contain a single such probe, which would both deliver laser light to a sample and collect Raman or fluorescent light emitted by the sample.

  8. Ion Channel Probes for Scanning Ion Conductance Microscopy

    PubMed Central

    2015-01-01

    The sensitivity and selectivity of ion channels provide an appealing opportunity for sensor development. Here, we describe ion channel probes (ICPs), which consist of multiple ion channels reconstituted into lipid bilayers suspended across the opening of perflourinated glass micropipets. When incorporated with a scanning ion conductance microscope (SICM), ICPs displayed a distance-dependent current response that depended on the number of ion channels in the membrane. With distance-dependent current as feedback, probes were translated laterally, to demonstrate the possibility of imaging with ICPs. The ICP platform yields several potential advantages for SICM that will enable exciting opportunities for incorporation of chemical information into imaging and for high-resolution imaging. PMID:25425190

  9. Optical spectroscopy and scanning tunneling microscopy studies of molecular adsorbates and anisotropic ultrathin films. Final report

    SciTech Connect

    Hemminger, J.C.

    1998-09-01

    The bonding, chemistry and ordering of molecular adsorbates on well defined single crystal surfaces and in ultrathin films was to be studied in an effort to develop sufficient fundamental understanding to allow the controlled preparation of anisotropic ultrathin films of organic monolayers. In this research the authors combine the use of optical probes (Raman spectroscopy, laser induced thermal desorption with Fourier transform mass spectrometry detection) with scanning tunneling microscopy (STM) and conventional methods of UHV surface science (Auger electron spectroscopy, x-ray photoelectron spectroscopy, low energy electron diffraction, and thermal desorption spectroscopy). The conventional surface probes provide well tested methods for the preparation and characterization of single crystal substrates. The optical probes used in the experiments provide powerful methods for the molecular identification of adsorbates in monolayers and ultrathin films. Scanning tunneling microscopy provides one with the ability to determine the detailed molecular level ordering of the molecular adsorbates. The emphasis of this research is on more complex molecular absorbates some of which are monomer precursors to ultrathin polymer films. Enhanced methods of Raman spectroscopy have been developed for the study of monolayer adsorbates on surfaces in ultrahigh vacuum environments. This report gives an overview of recent research results, including the construction of UHV variable temperature STM, analysis of STM images, growth and chemistry of intermetallic single crystal ultrathin films, and electron beam induced chemistry of tetracyanoquinodimethane.

  10. Method for nanoscale spatial registration of scanning probes with substrates and surfaces

    NASA Technical Reports Server (NTRS)

    Wade, Lawrence A. (Inventor)

    2010-01-01

    Embodiments in accordance with the present invention relate to methods and apparatuses for aligning a scanning probe used to pattern a substrate, by comparing the position of the probe to a reference location or spot on the substrate. A first light beam is focused on a surface of the substrate as a spatial reference point. A second light beam then illuminates the scanning probe being used for patterning. An optical microscope images both the focused light beam, and a diffraction pattern, shadow, or light backscattered by the illuminated scanning probe tip of a scanning probe microscope (SPM), which is typically the tip of the scanning probe on an atomic force microscope (AFM). Alignment of the scanning probe tip relative to the mark is then determined by visual observation of the microscope image. This alignment process may be repeated to allow for modification or changing of the scanning probe microscope tip.

  11. Temperature mapping of operating nanoscale devices by scanning probe thermometry

    PubMed Central

    Menges, Fabian; Mensch, Philipp; Schmid, Heinz; Riel, Heike; Stemmer, Andreas; Gotsmann, Bernd

    2016-01-01

    Imaging temperature fields at the nanoscale is a central challenge in various areas of science and technology. Nanoscopic hotspots, such as those observed in integrated circuits or plasmonic nanostructures, can be used to modify the local properties of matter, govern physical processes, activate chemical reactions and trigger biological mechanisms in living organisms. The development of high-resolution thermometry techniques is essential for understanding local thermal non-equilibrium processes during the operation of numerous nanoscale devices. Here we present a technique to map temperature fields using a scanning thermal microscope. Our method permits the elimination of tip–sample contact-related artefacts, a major hurdle that so far has limited the use of scanning probe microscopy for nanoscale thermometry. We map local Peltier effects at the metal–semiconductor contacts to an indium arsenide nanowire and self-heating of a metal interconnect with 7 mK and sub-10 nm spatial temperature resolution. PMID:26936427

  12. Temperature mapping of operating nanoscale devices by scanning probe thermometry

    NASA Astrophysics Data System (ADS)

    Menges, Fabian; Mensch, Philipp; Schmid, Heinz; Riel, Heike; Stemmer, Andreas; Gotsmann, Bernd

    2016-03-01

    Imaging temperature fields at the nanoscale is a central challenge in various areas of science and technology. Nanoscopic hotspots, such as those observed in integrated circuits or plasmonic nanostructures, can be used to modify the local properties of matter, govern physical processes, activate chemical reactions and trigger biological mechanisms in living organisms. The development of high-resolution thermometry techniques is essential for understanding local thermal non-equilibrium processes during the operation of numerous nanoscale devices. Here we present a technique to map temperature fields using a scanning thermal microscope. Our method permits the elimination of tip-sample contact-related artefacts, a major hurdle that so far has limited the use of scanning probe microscopy for nanoscale thermometry. We map local Peltier effects at the metal-semiconductor contacts to an indium arsenide nanowire and self-heating of a metal interconnect with 7 mK and sub-10 nm spatial temperature resolution.

  13. Temperature mapping of operating nanoscale devices by scanning probe thermometry.

    PubMed

    Menges, Fabian; Mensch, Philipp; Schmid, Heinz; Riel, Heike; Stemmer, Andreas; Gotsmann, Bernd

    2016-01-01

    Imaging temperature fields at the nanoscale is a central challenge in various areas of science and technology. Nanoscopic hotspots, such as those observed in integrated circuits or plasmonic nanostructures, can be used to modify the local properties of matter, govern physical processes, activate chemical reactions and trigger biological mechanisms in living organisms. The development of high-resolution thermometry techniques is essential for understanding local thermal non-equilibrium processes during the operation of numerous nanoscale devices. Here we present a technique to map temperature fields using a scanning thermal microscope. Our method permits the elimination of tip-sample contact-related artefacts, a major hurdle that so far has limited the use of scanning probe microscopy for nanoscale thermometry. We map local Peltier effects at the metal-semiconductor contacts to an indium arsenide nanowire and self-heating of a metal interconnect with 7 mK and sub-10 nm spatial temperature resolution. PMID:26936427

  14. Probing ultrafast spin dynamics with optical pump-probe scanning tunnelling microscopy.

    PubMed

    Yoshida, Shoji; Aizawa, Yuta; Wang, Zi-han; Oshima, Ryuji; Mera, Yutaka; Matsuyama, Eiji; Oigawa, Haruhiro; Takeuchi, Osamu; Shigekawa, Hidemi

    2014-08-01

    Studies of spin dynamics in low-dimensional systems are important from both fundamental and practical points of view. Spin-polarized scanning tunnelling microscopy allows localized spin dynamics to be characterized and plays important roles in nanoscale science and technology. However, nanoscale analysis of the ultrafast dynamics of itinerant magnetism, as well as its localized characteristics, should be pursued to advance further the investigation of quantum dynamics in functional structures of small systems. Here, we demonstrate the optical pump-probe scanning tunnelling microscopy technique, which enables the nanoscale probing of spin dynamics with the temporal resolution corresponding, in principle, to the optical pulse width. Spins are optically oriented using circularly polarized light, and their dynamics are probed by scanning tunnelling microscopy based on the optical pump-probe method. Spin relaxation in a single quantum well with a width of 6 nm was observed with a spatial resolution of ∼ 1 nm. In addition to spin relaxation dynamics, spin precession, which provides an estimation of the Landé g factor, was observed successfully. PMID:24974938

  15. Probing ultrafast spin dynamics with optical pump-probe scanning tunnelling microscopy

    NASA Astrophysics Data System (ADS)

    Yoshida, Shoji; Aizawa, Yuta; Wang, Zi-Han; Oshima, Ryuji; Mera, Yutaka; Matsuyama, Eiji; Oigawa, Haruhiro; Takeuchi, Osamu; Shigekawa, Hidemi

    2014-08-01

    Studies of spin dynamics in low-dimensional systems are important from both fundamental and practical points of view. Spin-polarized scanning tunnelling microscopy allows localized spin dynamics to be characterized and plays important roles in nanoscale science and technology. However, nanoscale analysis of the ultrafast dynamics of itinerant magnetism, as well as its localized characteristics, should be pursued to advance further the investigation of quantum dynamics in functional structures of small systems. Here, we demonstrate the optical pump-probe scanning tunnelling microscopy technique, which enables the nanoscale probing of spin dynamics with the temporal resolution corresponding, in principle, to the optical pulse width. Spins are optically oriented using circularly polarized light, and their dynamics are probed by scanning tunnelling microscopy based on the optical pump-probe method. Spin relaxation in a single quantum well with a width of 6 nm was observed with a spatial resolution of ~1 nm. In addition to spin relaxation dynamics, spin precession, which provides an estimation of the Landé g factor, was observed successfully.

  16. Development and demonstration of table-top synchronized fast-scan femtosecond time-resolved spectroscopy system by single-shot scan photo detector array

    NASA Astrophysics Data System (ADS)

    Yabushita, Atsushi; Kao, Chih-Hsien; Lee, Yu-Hsien; Kobayashi, Takayoshi

    2015-07-01

    Ultrafast dynamics is generally studied by pump-probe method with laser pulse, which scans optical delay by motorized stage step by step. Using ultrashort laser pulse shorter than typical molecular vibration periods, the pump-probe measurement can study both of electronic dynamics and vibration dynamics simultaneously. The probe wavelength dependence of the ultrafast electronic and vibration dynamics (UEVD) helps us to distinguish the signal contributions from the dynamics of the electronic ground state and that of the electronic excited states, which elucidates primary reaction mechanism after photoexcitation. Meanwhile, the measurement time of UEVD spectroscopy takes too long time to be used in realistic application. In our previous work, we have developed multi-channel lock-in amplifying (MLA) detectors to study UEVD at all probe wavelengths simultaneously, and synchronized it with laser and fast-scan delay stage to scan the data in five seconds. It enabled us to study UEVD spectroscopy even for photo-fragile materials. However, the home-made MLA detectors required for the measurement is expensive and massive in size and weight, thus not suitable for general researchers in the field of ultrafast time-resolved spectroscopy. In the present work, we have developed a table-top synchronized fast-scan femtosecond time-resolved spectroscopy system using single shot scan line CCD. This system measures time-resolved trace at all probe wavelengths simultaneously in five seconds. The CCD-based fast-scan time-resolved spectroscopy system enables us to study ultrafast dynamics of various materials even biomaterials, which have been thought to be hard or even impossible to be studied in previous methods.

  17. 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.

  18. Scanning thermal microscopy with heat conductive nanowire probes.

    PubMed

    Timofeeva, Maria; Bolshakov, Alexey; Tovee, Peter D; Zeze, Dagou A; Dubrovskii, Vladimir G; Kolosov, Oleg V

    2016-03-01

    Scanning thermal microscopy (SThM), which enables measurement of thermal transport and temperature distribution in devices and materials with nanoscale resolution is rapidly becoming a key approach in resolving heat dissipation problems in modern processors and assisting development of new thermoelectric materials. In SThM, the self-heating thermal sensor contacts the sample allowing studying of the temperature distribution and heat transport in nanoscaled materials and devices. The main factors that limit the resolution and sensitivities of SThM measurements are the low efficiency of thermal coupling and the lateral dimensions of the probed area of the surface studied. The thermal conductivity of the sample plays a key role in the sensitivity of SThM measurements. During the SThM measurements of the areas with higher thermal conductivity the heat flux via SThM probe is increased compared to the areas with lower thermal conductivity. For optimal SThM measurements of interfaces between low and high thermal conductivity materials, well defined nanoscale probes with high thermal conductivity at the probe apex are required to achieve a higher quality of the probe-sample thermal contact while preserving the lateral resolution of the system. In this paper, we consider a SThM approach that can help address these complex problems by using high thermal conductivity nanowires (NW) attached to a tip apex. We propose analytical models of such NW-SThM probes and analyse the influence of the contact resistance between the SThM probe and the sample studied. The latter becomes particularly important when both tip and sample surface have high thermal conductivities. These models were complemented by finite element analysis simulations and experimental tests using prototype probe where a multiwall carbon nanotube (MWCNT) is exploited as an excellent example of a high thermal conductivity NW. These results elucidate critical relationships between the performance of the SThM probe on

  19. Role of space charge in scanned probe oxidation

    NASA Astrophysics Data System (ADS)

    Dagata, J. A.; Inoue, T.; Itoh, J.; Matsumoto, K.; Yokoyama, H.

    1998-12-01

    The growth rate and electrical character of nanostructures produced by scanned probe oxidation are investigated by integrating an in situ electrical force characterization technique, scanning Maxwell-stress microscopy, into the fabrication process. Simultaneous topographical, capacitance, and surface potential data are obtained for oxide features patterned on n- and p-type silicon and titanium thin-film substrates. The electric field established by an applied voltage pulse between the probe tip and substrate depends upon reactant and product ion concentrations associated with the water meniscus at the tip-substrate junction and within the growing oxide film. Space-charge effects are consistent with the rapid decline of high initial growth rates, account for observed doping and voltage-pulse dependencies, and provide a basis for understanding local density variations within oxide features. An obvious method for avoiding the buildup of space charge is to employ voltage modulation and other dynamic pulse-shaping techniques during the oxidation pulse. Voltage modulation leads to a significant enhancement of the growth rate and to improvements in the aspect ratio compared with static voltage pulses.

  20. Combined fiber probe for fluorescence lifetime and Raman spectroscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Dochow, Sebastian; Ma, Dinglong; Latka, Ines; Bocklitz, Thomas; Hartl, Brad; Bec, Julien; Fatakdawala, Hussain; Wachsmann-Hogiu, Sebastian; Marple, Eric; Urmey, Kirk; Schmitt, Michael; Marcu, Laura; Popp, Jürgen

    2016-03-01

    Raman spectroscopy has been proven to have tremendous potential as biomedical analytical tool for spectroscopic disease diagnostics. The use of fiberoptic coupled Raman spectroscopy systems can enable in-vivo characterization of suspicious lesions. However, Raman spectroscopy has the drawback of rather long acquisition times of several hundreds of milliseconds which makes scanning of larger regions quite challenging. By combining Raman spectroscopy with a fast imaging technique this problem can be alleviate in part. Fluorescence lifetime imaging (FLIm) offers a great potential for such a combination. FLIm can allow for fast tissue area pre-segmentation and location of the points for Raman spectra acquisition. Here, we introduce an optical fiber probe combining FLIm and Raman spectroscopy with an outer diameter of 2 mm. Fluorescence is generated via excitation with a fiber laser at 355 nm. The fluorescence emission is spectrally resolved using a custom-made wavelength-selection module (WSM). The Raman excitation power at 785 nm was set to 50 mW for the in-vivo measurements to prevent sample drying. The lateral probe resolution was determined to be <250 μm for both modalities. This value was taken as step size for several raster scans of different tissue types which were conducted to show the overlap of both modalities under realistic conditions. Finally the probe was used for in vivo raster scans of a rat's brain and subsequently to acquire FLIm guided Raman spectra of several tissues in and around the craniotomy.

  1. Multidimensional NMR spectroscopy in a single scan.

    PubMed

    Gal, Maayan; Frydman, Lucio

    2015-11-01

    Multidimensional NMR has become one of the most widespread spectroscopic tools available to study diverse structural and functional aspects of organic and biomolecules. A main feature of multidimensional NMR is the relatively long acquisition times that these experiments demand. For decades, scientists have been working on a variety of alternatives that would enable NMR to overcome this limitation, and deliver its data in shorter acquisition times. Counting among these methodologies is the so-called ultrafast (UF) NMR approach, which in principle allows one to collect arbitrary multidimensional correlations in a single sub-second transient. By contrast to conventional acquisitions, a main feature of UF NMR is a spatiotemporal manipulation of the spins that imprints the chemical shift and/or J-coupling evolutions being sought, into a spatial pattern. Subsequent gradient-based manipulations enable the reading out of this information and its multidimensional correlation into patterns that are identical to those afforded by conventional techniques. The current review focuses on the fundamental principles of this spatiotemporal UF NMR manipulation, and on a few of the methodological extensions that this form of spectroscopy has undergone during the years. PMID:26249041

  2. Dual-probe scanning tunneling microscope for study of nanoscale metal-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Yi, W.; Kaya, I. I.; Altfeder, I. B.; Appelbaum, I.; Chen, D. M.; Narayanamurti, V.

    2005-06-01

    Using a dual-probe scanning tunneling microscope, we have performed three-terminal ballistic electron emission spectroscopy on Au /GaAs(100) by contacting the patterned metallic thin film with one tip and injecting ballistic electrons with another tip. The collector current spectra agree with a Monte-Carlo simulation based on modified planar tunneling theory. Our results suggest that it is possible to study nanoscale metal-semiconductor interfaces without the requirement of an externally-contacted continuous metal thin film.

  3. Probing the Inelastic Interactions in Molecular Junctions by Scanning Tunneling Microscope

    NASA Astrophysics Data System (ADS)

    Xu, Chen

    With a sub-Kelvin scanning tunneling microscope, the energy resolution of spectroscopy is improved dramatically. Detailed studies of finer features of spectrum become possible. The asymmetry in the line shape of carbon monoxide vibrational spectra is observed to correlate with the couplings of the molecule to the tip and substrates. The spin-vibronic coupling in the molecular junctions is revisited with two metal phthalocyanine molecules, unveiling sharp spin-vibronic peaks. Finally, thanks to the improved spectrum resolution, the bonding structure of the acyclic compounds molecules is surveyed with STM inelastic tunneling probe, expanding the capability of the innovative high resolution imaging technique.

  4. Scanning tunneling spectroscopy of chemical vapor deposition grown graphene

    NASA Astrophysics Data System (ADS)

    Cormode, Daniel; Reynolds, Collin; Leroy, Brian

    2011-03-01

    The electronic properties of CVD grown graphene were investigated by scanning tunneling microscopy. Mono and multi layered samples were prepared by growth on copper and transferred to 300 nm Si O2 substrates. Raman spectroscopy mapping was used to determine the thickness of the samples as well as characterize regions of higher disorder as evidenced by an increased D peak. The samples were then measured in ultra high vacuum by scanning tunneling spectroscopy at 5 K. The type and density of defects measured with the STM were compared with measured D peak intensity. We have examined the correlation between changes in the local density of states and disorder in monolayer graphene.

  5. Potentiostatic deposition of DNA for scanning probe microscopy.

    PubMed Central

    Lindsay, S M; Tao, N J; DeRose, J A; Oden, P I; Lyubchenko YuL; Harrington, R E; Shlyakhtenko, L

    1992-01-01

    We describe a procedure for reversible adsorption of DNA onto a gold electrode maintained under potential control. The adsorbate can be imaged by scanning probe microscopy in situ. Quantitative control of a molecular adsorbate for microscopy is now possible. We found a potential window (between 0 and 180 mV versus a silver wire quasi reference) over which a gold (111) surface under phosphate buffer is positively charged, but is not covered with a dense adsorbate. When DNA is present in these conditions, molecules adsorb onto the electrode and remain stable under repeated scanning with a scanning tunneling microscope (STM). They become removed when the surface is brought to a negative charge. When operated at tunnel currents below approximately 0.4 nA, the STM yields a resolution of approximately 1 nm, which is better than can be obtained with atomic force microscopy (AFM) at present. We illustrate this procedure by imaging a series of DNA molecules made by ligating a 21 base-pair oligonucleotide. We observed the expected series of fragment lengths but small fragments are adsorbed preferentially. Images FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 7 FIGURE 8 FIGURE 9 FIGURE 10 FIGURE 11 PMID:1617139

  6. Fluorescent probes for shock compression spectroscopy

    NASA Astrophysics Data System (ADS)

    Banishev, Alexandr; Christensen, James; Dlott, Dana

    We have demonstrated the capability of using Rhodamine 6G dye as an ultrafast emission probe in high-speed shock compression of condensed matter. The ultimate time response of the probe, which functions as a high-speed pressure sensor, is limited by fundamental photophysical processes such as radiative rates, internal conversion rates and intersystem crossing rates. The time response has been greatly improved by encapsulating the dye in silica nano or microparticles. This probe was used to observed nanosecond viscoelastic shock compression of a polymer (PMMA), and has been used to monitor the response of individual grains of sand to high-speed impact.

  7. Scanning gate spectroscopy of a quantum Hall island near a quantum point contact

    NASA Astrophysics Data System (ADS)

    Hackens, Benoit; Martins, Frederico; Faniel, Sebastien; Bayot, Vincent; Rosenow, Bernd; Desplanque, Ludovic; Wallart, Xavier; Pala, Marco; Sellier, Hermann; Huant, Serge

    2013-03-01

    We report on low temperature (100 mK) scanning gate experiments performed at high magnetic field (around 10 T) on a mesoscopic device patterned in an InGaAs/InAlAs heterostructure. Magnetotransport measurements yield signatures of ultra-small Quantum Hall Islands (QHI) formed by closed quantum Hall edge states and connected to propagating edge channels through tunnel barriers. Scanning gate microscopy and scanning gate spectroscopy are used to locate and probe a single QHI near a quantum point contact. The presence of Coulomb diamonds in the local spectroscopy confirms that Coulomb blockade governs transport across the QHI. Varying the microscope tip bias as well as current bias across the device, we uncover the QHI discrete energy spectrum arising from electronic confinement and we extract estimates of the gradient of the confining potential and of the edge state velocity.

  8. Characterization of probe contact effects on diffuse reflectance spectroscopy measurements

    NASA Astrophysics Data System (ADS)

    Reistad, Nina; Mayjonade, Mallory; Ahadi, Aylin; Andersson-Engels, Stefan

    2015-06-01

    Diffuse reflectance spectroscopy (DRS) is a rapid, non-invasive optical method widely adopted to gain diagnostic information of tissue. The most flexible approach to this method is a fiber-optic contact-probe used with a spectroscopy system. A challenge of this method is that the external pressure brought by the probe can significantly affect the tissue optical properties as well as the light coupling into the probe, and thus influence the collected DRS-spectrum. In this study we investigate and characterize the effect of probe pressure on DRS-spectra obtained with a calibrated loaded-spring system used with a fiber optic probe in the range (400 - 1600) nm. A multilayer FE-model of the indentation is developed to get a better insight of the distribution of pressure and stresses inside the skin under indentation.

  9. Nanoscale Electromechanics of Ferroelectric and Biological Systems: A New Dimension in Scanning Probe Microscopy

    SciTech Connect

    Kalinin, Sergei V; Rodriguez, Brian J; Jesse, Stephen; Karapetian, Edgar; Mirman, B; Eliseev, E. A.; Morozovska, A. N.

    2007-01-01

    Functionality of biological and inorganic systems ranging from nonvolatile computer memories and microelectromechanical systems to electromotor proteins and cellular membranes is ultimately based on the intricate coupling between electrical and mechanical phenomena. In the past decade, piezoresponse force microscopy (PFM) has been established as a powerful tool for nanoscale imaging, spectroscopy, and manipulation of ferroelectric and piezoelectric materials. Here, we give an overview of the fundamental image formation mechanism in PFM and summarize recent theoretical and technological advances. In particular, we show that the signal formation in PFM is complementary to that in the scanning tunneling microscopy (STM) and atomic force microscopy (AFM) techniques, and we discuss the implications. We also consider the prospect of extending PFM beyond ferroelectric characterization for quantitative probing of electromechanical behavior in molecular and biological systems and high-resolution probing of static and dynamic polarization switching processes in low-dimensional ferroelectric materials and heterostructures.

  10. Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography

    NASA Astrophysics Data System (ADS)

    Albisetti, E.; Petti, D.; Pancaldi, M.; Madami, M.; Tacchi, S.; Curtis, J.; King, W. P.; Papp, A.; Csaba, G.; Porod, W.; Vavassori, P.; Riedo, E.; Bertacco, R.

    2016-06-01

    The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method.

  11. Scanning Hall probe microscopy of a diluted magnetic semiconductor

    SciTech Connect

    Kweon, Seongsoo; Samarth, Nitin; Lozanne, Alex de

    2009-05-01

    We have measured the micromagnetic properties of a diluted magnetic semiconductor as a function of temperature and applied field with a scanning Hall probe microscope built in our laboratory. The design philosophy for this microscope and some details are described. The samples analyzed in this work are Ga{sub 0.94}Mn{sub 0.06}As films grown by molecular beam epitaxy. We find that the magnetic domains are 2-4 mum wide and fairly stable with temperature. Magnetic clusters are observed above T{sub C}, which we ascribe to MnAs defects too small and sparse to be detected by a superconducting quantum interference device magnetometer.

  12. Ferroelectric Switching by the Grounded Scanning Probe Microscopy Tip

    SciTech Connect

    Ievlev, Anton V.; Morozovska, A. N.; Shur, Vladimir Ya.; Kalinin, Sergei V.

    2015-06-19

    The process of polarization reversal by the tip of scanning probe microscope was intensively studied for last two decades. Number of the abnormal switching phenomena was reported by the scientific groups worldwide. In particularly it was experimentally and theoretically shown that slow dynamics of the surface screening controls kinetics of the ferroelectric switching, backswitching and relaxation and presence of the charges carriers on the sample surface and in the sample bulk significantly change polarization reversal dynamics. Here we experimentally demonstrated practical possibility of the history dependent polarization reversal by the grounded SPM tip. This phenomenon was attributed to induction of the slowly dissipating charges into the surface of the grounded tip that enables polarization reversal under the action of the produced electric field. Analytical and numerical electrostatic calculations allow additional insight into nontrivial abnormal switching phenomena reported earlier.

  13. Ferroelectric Switching by the Grounded Scanning Probe Microscopy Tip

    DOE PAGESBeta

    Ievlev, Anton V.; Morozovska, A. N.; Shur, Vladimir Ya.; Kalinin, Sergei V.

    2015-06-19

    The process of polarization reversal by the tip of scanning probe microscope was intensively studied for last two decades. Number of the abnormal switching phenomena was reported by the scientific groups worldwide. In particularly it was experimentally and theoretically shown that slow dynamics of the surface screening controls kinetics of the ferroelectric switching, backswitching and relaxation and presence of the charges carriers on the sample surface and in the sample bulk significantly change polarization reversal dynamics. Here we experimentally demonstrated practical possibility of the history dependent polarization reversal by the grounded SPM tip. This phenomenon was attributed to induction ofmore » the slowly dissipating charges into the surface of the grounded tip that enables polarization reversal under the action of the produced electric field. Analytical and numerical electrostatic calculations allow additional insight into nontrivial abnormal switching phenomena reported earlier.« less

  14. 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.

  15. Nanopatterning reconfigurable magnetic landscapes via thermally assisted scanning probe lithography.

    PubMed

    Albisetti, E; Petti, D; Pancaldi, M; Madami, M; Tacchi, S; Curtis, J; King, W P; Papp, A; Csaba, G; Porod, W; Vavassori, P; Riedo, E; Bertacco, R

    2016-06-01

    The search for novel tools to control magnetism at the nanoscale is crucial for the development of new paradigms in optics, electronics and spintronics. So far, the fabrication of magnetic nanostructures has been achieved mainly through irreversible structural or chemical modifications. Here, we propose a new concept for creating reconfigurable magnetic nanopatterns by crafting, at the nanoscale, the magnetic anisotropy landscape of a ferromagnetic layer exchange-coupled to an antiferromagnetic layer. By performing localized field cooling with the hot tip of a scanning probe microscope, magnetic structures, with arbitrarily oriented magnetization and tunable unidirectional anisotropy, are reversibly patterned without modifying the film chemistry and topography. This opens unforeseen possibilities for the development of novel metamaterials with finely tuned magnetic properties, such as reconfigurable magneto-plasmonic and magnonic crystals. In this context, we experimentally demonstrate spatially controlled spin wave excitation and propagation in magnetic structures patterned with the proposed method. PMID:26950242

  16. Probing Access Resistance of Solid-state Nanopores with a Scanning Probe Microscope Tip.

    PubMed

    Hyun, Changbae; Rollings, Ryan; Li, Jiali

    2012-02-01

    An apparatus that integrates solid-state nanopore ionic current measurement with a Scanning Probe Microscope has been developed. When a micrometer-scale scanning probe tip is near a voltage biased nanometer-scale pore (10-100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, we estimate the relative pore resistance increase due to the tip, ΔR/R(0), as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ΔR/R(0) also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, ~10 nm, our experiments show that ΔR/R(0) depends on salt concentration as predicted by the Poisson and Nernst-Planck equations. Furthermore, our measurements show that ΔR/R(0) goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally, they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip. PMID:22393313

  17. Probing access resistance of solid-state nanopores with a scanning-probe microscope tip.

    PubMed

    Hyun, Changbae; Rollings, Ryan; Li, Jiali

    2012-02-01

    An apparatus that integrates solid-state nanopore ionic current measurement with a scanning-probe microscope is developed. When a micrometer-scale scanning-probe tip is near a voltage-biased nanometer-scale pore (10–100 nm), the tip partially blocks the flow of ions to the pore and increases the pore access resistance. The apparatus records the current blockage caused by the probe tip and the location of the tip simultaneously. By measuring the current blockage map near a nanopore as a function of the tip position in 3D space in salt solution, the relative pore resistance increases due to the tip and ΔR/R0 is estimated as a function of the tip location, nanopore geometry, and salt concentration. The amplitude of ΔR/R0 also depends on the ratio of the pore length to its radius as Ohm's law predicts. When the tip is very close to the pore surface, ≈10 nm, experiments show that ΔR/R0 depends on salt concentration as predicted by the Poisson and Nernst–Planck equations. Furthermore, the measurements show that ΔR/R0 goes to zero when the tip is about five times the pore diameter away from the center of the pore entrance. The results in this work not only demonstrate a way to probe the access resistance of nanopores experimentally; they also provide a way to locate the nanopore in salt solution, and open the door to future nanopore experiments for detecting single biomolecules attached to a probe tip. PMID:22287084

  18. Simulation of near-field scanning optical microscopy using a plasmonic gap probe

    NASA Astrophysics Data System (ADS)

    Tanaka, Kazuo; Tanaka, Masahiro; Katayama, Kiyofumi

    2006-10-01

    Imaging by near-field scanning optical microscopy (NSOM) with a plasmonic gap probe (PGP) is simulated to confirm the operation of the recently proposed PGP. The simulations demonstrate that the probe works in illumination, collection-reflection and collection mode, and that is it not necessary to vibrate the probe tip in order to remove background noise. The resolution of the scanned image is also shown to be approximately equal to the diameter of the probe tip. Furthermore, the throughput of the probe is much higher than conventional aperture probes providing similar resolution. The proposed probe thus has the advantages of both aperture probes and scattering probes, and is expected to have excellent characteristics for use as a scanning probe for NSOM.

  19. Three axis vector magnet set-up for cryogenic scanning probe microscopy

    SciTech Connect

    Galvis, J. A.; Herrera, E.; Buendía, A.; Guillamón, I.; Vieira, S.; Suderow, H.; Azpeitia, J.; Luccas, R. F.; Munuera, C.; García-Hernandez, M.; and others

    2015-01-15

    We describe a three axis vector magnet system for cryogenic scanning probe microscopy measurements. We discuss the magnet support system and the power supply, consisting of a compact three way 100 A current source. We obtain tilted magnetic fields in all directions with maximum value of 5T along z-axis and of 1.2T for XY-plane magnetic fields. We describe a scanning tunneling microscopy-spectroscopy (STM-STS) set-up, operating in a dilution refrigerator, which includes a new high voltage ultralow noise piezodrive electronics and discuss the noise level due to vibrations. STM images and STS maps show atomic resolution and the tilted vortex lattice at 150 mK in the superconductor β-Bi{sub 2}Pd. We observe a strongly elongated hexagonal lattice, which corresponds to the projection of the tilted hexagonal vortex lattice on the surface. We also discuss Magnetic Force Microscopy images in a variable temperature insert.

  20. Three axis vector magnet set-up for cryogenic scanning probe microscopy.

    PubMed

    Galvis, J A; Herrera, E; Guillamón, I; Azpeitia, J; Luccas, R F; Munuera, C; Cuenca, M; Higuera, J A; Díaz, N; Pazos, M; García-Hernandez, M; Buendía, A; Vieira, S; Suderow, H

    2015-01-01

    We describe a three axis vector magnet system for cryogenic scanning probe microscopy measurements. We discuss the magnet support system and the power supply, consisting of a compact three way 100 A current source. We obtain tilted magnetic fields in all directions with maximum value of 5T along z-axis and of 1.2T for XY-plane magnetic fields. We describe a scanning tunneling microscopy-spectroscopy (STM-STS) set-up, operating in a dilution refrigerator, which includes a new high voltage ultralow noise piezodrive electronics and discuss the noise level due to vibrations. STM images and STS maps show atomic resolution and the tilted vortex lattice at 150 mK in the superconductor β-Bi2Pd. We observe a strongly elongated hexagonal lattice, which corresponds to the projection of the tilted hexagonal vortex lattice on the surface. We also discuss Magnetic Force Microscopy images in a variable temperature insert. PMID:25638089

  1. Thermochemical scanning probe lithography of protein gradients at the nanoscale.

    PubMed

    Albisetti, E; Carroll, K M; Lu, X; Curtis, J E; Petti, D; Bertacco, R; Riedo, E

    2016-08-01

    Patterning nanoscale protein gradients is crucial for studying a variety of cellular processes in vitro. Despite the recent development in nano-fabrication technology, combining nanometric resolution and fine control of protein concentrations is still an open challenge. Here, we demonstrate the use of thermochemical scanning probe lithography (tc-SPL) for defining micro- and nano-sized patterns with precisely controlled protein concentration. First, tc-SPL is performed by scanning a heatable atomic force microscopy tip on a polymeric substrate, for locally exposing reactive amino groups on the surface, then the substrate is functionalized with streptavidin and laminin proteins. We show, by fluorescence microscopy on the patterned gradients, that it is possible to precisely tune the concentration of the immobilized proteins by varying the patterning parameters during tc-SPL. This paves the way to the use of tc-SPL for defining protein gradients at the nanoscale, to be used as chemical cues e.g. for studying and regulating cellular processes in vitro. PMID:27344982

  2. Thermochemical scanning probe lithography of protein gradients at the nanoscale

    NASA Astrophysics Data System (ADS)

    Albisetti, E.; Carroll, K. M.; Lu, X.; Curtis, J. E.; Petti, D.; Bertacco, R.; Riedo, E.

    2016-08-01

    Patterning nanoscale protein gradients is crucial for studying a variety of cellular processes in vitro. Despite the recent development in nano-fabrication technology, combining nanometric resolution and fine control of protein concentrations is still an open challenge. Here, we demonstrate the use of thermochemical scanning probe lithography (tc-SPL) for defining micro- and nano-sized patterns with precisely controlled protein concentration. First, tc-SPL is performed by scanning a heatable atomic force microscopy tip on a polymeric substrate, for locally exposing reactive amino groups on the surface, then the substrate is functionalized with streptavidin and laminin proteins. We show, by fluorescence microscopy on the patterned gradients, that it is possible to precisely tune the concentration of the immobilized proteins by varying the patterning parameters during tc-SPL. This paves the way to the use of tc-SPL for defining protein gradients at the nanoscale, to be used as chemical cues e.g. for studying and regulating cellular processes in vitro.

  3. Nanoscale ferroelectric field-effect writing and reading using scanning tunnelling spectroscopy.

    PubMed

    Kuffer, Olivier; Maggio-Aprile, Ivan; Fischer, Øystein

    2005-05-01

    Control of the density of mobile charge carriers using electric fields is widely used in a variety of metal-insulator-semiconductor structures and is the governing principle behind the operation of field-effect transistors. Ferroelectric materials possessing a switchable and non-volatile polarization field can be used as insulating layers, revealing new opportunities for device applications. Advances in material processing and in particular complex oxide thin-film growth mean that high-quality field-effect devices can be based on ferroelectric/metallic oxide heterostructures. In addition, advances in local probe techniques such as atomic force microscopy allow them to be used in the imaging and study of small ferroelectric domain structures in bulk crystals and thin films. Meanwhile, scanning tunnelling microscopy and spectroscopy have established themselves as powerful techniques for atomic manipulation and nanometre-resolution electron tunnelling spectroscopy. Here, a scanning tunnelling microscope is used to investigate the ferroelectric field effect in all-perovskite heterostructures. Scanning tunnelling spectroscopy allows us to probe the local electronic properties of the polarized channel of a ferroelectric field-effect device as a function of the field orientation. This technique can be used to read and write ferroelectric field-induced regions with a size as low as 20 nm. PMID:15834416

  4. Integrated scanning Kelvin probe-scanning electrochemical microscope system: development and first applications.

    PubMed

    Maljusch, Artjom; Schönberger, Bernd; Lindner, Armin; Stratmann, Martin; Rohwerder, Michael; Schuhmann, Wolfgang

    2011-08-01

    The integration of a scanning Kelvin probe (SKP) and a scanning electrochemical microscope (SECM) into a single SKP-SECM setup, the concept of the proposed system, its technical realization, and first applications are presented and discussed in detail. A preloaded piezo actuator placed in a grounded stainless steel case was used as the driving mechanism for oscillation of a Pt disk electrode as conventionally used in SECM when the system was operated in the SKP mode. Thus, the same tip is recording the contact potential difference (CPD) during SKP scanning and is used as a working electrode for SECM imaging in the redox-competition mode (RC-SECM). The detection of the local CPD is established by amplification of the displacement current at an ultralow noise operational amplifier and its compensation by application of a variable backing potential (V(b)) in the external circuit. The control of the tip-to-sample distance is performed by applying an additional alternating voltage with a much lower frequency than the oscillation frequency of the Kelvin probe. The main advantage of the SKP-SECM system is that it allows constant distance measurements of the CPD in air under ambient conditions and in the redox-competition mode of the SECM in the electrolyte of choice over the same sample area without replacement of the sample or exchange of the working electrode. The performance of the system was evaluated using a test sample made by sputtering thin Pt and W films on an oxidized silicon wafer. The obtained values of the CPD correlate well with known data, and the electrochemical activity for oxygen reduction is as expected higher over Pt than W. PMID:21675763

  5. Monolithically Integrated, Mechanically Resilient Carbon-Based Probes for Scanning Probe Microscopy

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Megerian, Krikor G.; Jennings, Andrew T.; Greer, Julia R.

    2010-01-01

    Scanning probe microscopy (SPM) is an important tool for performing measurements at the nanoscale in imaging bacteria or proteins in biology, as well as in the electronics industry. An essential element of SPM is a sharp, stable tip that possesses a small radius of curvature to enhance spatial resolution. Existing techniques for forming such tips are not ideal. High-aspect-ratio, monolithically integrated, as-grown carbon nanofibers (CNFs) have been formed that show promise for SPM applications by overcoming the limitations present in wet chemical and separate substrate etching processes.

  6. Sparse sampling and reconstruction for electron and scanning probe microscope imaging

    SciTech Connect

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

    2015-07-28

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

  7. Electrical Measurements and Nanomechanics Using Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Chang, Yong

    2002-10-01

    In the early 1980s, G. Binnig et al. invented the Scanning Tunneling Microscopy (STM) [1], making it possible to obtain atomic resolution images of conducting surfaces. After that, many different types of Scanning Probe Microscopy (SPM) were invented and some of the most useful representatives are Atomic Force Microscopy (AFM) [2], Electrostatic Force Microscopy (EFM) [3] and Kelvin Probe Force Microscopy (KPFM) [4,5]. In 1985, G. Binnig et al. [2] invented the AFM, which now is used as a fundamental tool in many fields of research. Developed from AFM, Y. Martin et al. [3] invented EFM in 1987. The development of AC mode AFM allows the detection of weak long-range forces. EFM has also been used to study other systems and phenomena, such as thin liquid films on solid surfaces [6], electrically stressed gold nanowires [7], and spatial charge distribution in quantum wires [8]. In 1991, M. Nonnenmacher et al. [5] invented Kelvin Probe Force Microscopy. KPFM is used to study any property that affects the tip-surface Contact Potential Difference (CPD), such as voltage signals in integrated circuits (IC) [9], charged grain boundaries in polycrystalline silicon [10] and surface potential variations in multilayer semiconductor devices [11]. The aim of this poster is to discuss the application of SPM to electrical measurements. The theory of SPM was presented. The AFM was firstly introduced as it was developed before the other two. The design and theory were discussed. The force-distance curve was introduced. After this EFM was presented. EFM was developed from AC mode AFM. The technique was achieved by applying a DC voltage between the tip and the sample. The design, theory and features of it were surveyed. KPFM was also discussed. KPFM was developed from EFM. The central part of this technique is to measure the CPD. Experimental measurements of SPM were described after theory part. Research work using AFM was presented. The newest technique of AFM, UHV-AFM has been used in

  8. Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope.

    PubMed

    Li, Meng; Xu, Chunkai; Zhang, Panke; Li, Zhean; Chen, Xiangjun

    2016-08-01

    We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than the size of the incident electron beam. PMID:27587179

  9. Note: Electron energy spectroscopy mapping of surface with scanning tunneling microscope

    NASA Astrophysics Data System (ADS)

    Li, Meng; Xu, Chunkai; Zhang, Panke; Li, Zhean; Chen, Xiangjun

    2016-08-01

    We report a novel scanning probe electron energy spectrometer (SPEES) which combines a double toroidal analyzer with a scanning tunneling microscope to achieve both topography imaging and electron energy spectroscopy mapping of surface in situ. The spatial resolution of spectroscopy mapping is determined to be better than 0.7 ± 0.2 μm at a tip sample distance of 7 μm. Meanwhile, the size of the field emission electron beam spot on the surface is also measured, and is about 3.6 ± 0.8 μm in diameter. This unambiguously demonstrates that the spatial resolution of SPEES technique can be much better than the size of the incident electron beam.

  10. Spatial heterodyne spectroscopy - Interferometric performance at any wavelength without scanning

    NASA Technical Reports Server (NTRS)

    Roesler, F. L.; Harlander, J.

    1990-01-01

    Spatial heterodyne spectroscopy (SHS) employing a two-beam dispersive interferometer producing a Fizeau fringe pattern having wavelength-dependent spatial frequencies is presented. The pattern is recorded on an imaging detector and Fourier transformed to recover the input stream. It is pointed out that spectrometers operating on the SHS principle can achieve the theoretical resolution limit of the gratings without scanning, retaining at the same time the large angular input tolerance and multiplexing properties of conventional scanning Fourier-transform spectrometers. Additionally, broad spectral coverages can be achieved, and field widening can be accomplished without moving parts.

  11. Ultrasonic Wave Field Modeling in a Conical Scanning Probe Tip

    NASA Astrophysics Data System (ADS)

    Every, Arthur; Wenke, Ingo; Aebi, Laurent; Dual, Jurg

    2011-06-01

    The ultrasonic wave field modeling reported in this paper has been undertaken with a view to optimizing the design of a conical scanning probe microscope tip to be used in measuring the near surface elastic properties of solids at high frequencies and high spatial resolution. The modeling is concerned with the evolution of a pulse which is launched from the upper spherical shaped surface of the tip, and is aimed at achieving the greatest possible concentration of acoustic energy at the lower sharp end of the tip. The calculations assume a transversely isotropic medium. Two complementary approaches have been taken, firstly the discretization of the equations of motion on a 1000×1000 mesh and solution using the commercial FE package ABAQUS, and secondly an analytical approach based on the angular spectrum method and stationary phase approximation. A high degree of consistency is achieved between the two approaches regarding the characteristics of the focal region, dispersion of the pulse attendant on the discretization of the system, and other features of the wave field. With the combination of the two approaches we are able to model the wave field over a very wide range of frequencies from low frequencies, where advantage lies with the FE method, to high frequencies where the computational cost of the FE method is inordinate and the analytical approach becomes progressively more accurate.

  12. Laser scanning dental probe for endodontic root canal treatment

    NASA Astrophysics Data System (ADS)

    Blank, Molly A. B.; Friedrich, Michal; Hamilton, Jeffrey D.; Lee, Peggy; Berg, Joel; Seibel, Eric J.

    2011-03-01

    Complications that arise during endodontic procedures pose serious threats to the long-term integrity and health of the tooth. Potential complexities of root canals include residual pulpal tissue, cracks, mesial-buccal 2 and accessory canals. In the case of a failed root canal, a successful apicoectomy can be jeopardized by isthmuses, accessory canals, and root microfracture. Confirming diagnosis using a small imaging probe would allow proper treatment and prevent retreatment of endodontic procedures. An ultrathin and flexible laser scanning endoscope of 1.2 to 1.6mm outer diameter was used in vitro to image extracted teeth with varied root configurations. Teeth were opened using a conventional bur and high speed drill. Imaging within the opened access cavity clarified the location of the roots where canal filing would initiate. Although radiographs are commonly used to determine the root canal size, position, and shape, the limited 2D image perspective leaves ambiguity that could be clarified if used in conjunction with a direct visual imaging tool. Direct visualization may avoid difficulties in locating the root canal and reduce the number of radiographs needed. A transillumination imaging device with the separated illumination and light collection functions rendered cracks visible in the prepared teeth that were otherwise indiscernible using reflected visible light. Our work demonstrates that a small diameter endoscope with high spatial resolution may significantly increase the efficiency and success of endodontic procedures.

  13. Probing Individual Ice Nucleation Events with Environmental Scanning Electron Microscopy

    NASA Astrophysics Data System (ADS)

    Wang, Bingbing; China, Swarup; Knopf, Daniel; Gilles, Mary; Laskin, Alexander

    2016-04-01

    Heterogeneous ice nucleation is one of the processes of critical relevance to a range of topics in the fundamental and the applied science and technologies. Heterogeneous ice nucleation initiated by particles proceeds where microscopic properties of particle surfaces essentially control nucleation mechanisms. Ice nucleation in the atmosphere on particles governs the formation of ice and mixed phase clouds, which in turn influence the Earth's radiative budget and climate. Heterogeneous ice nucleation is still insufficiently understood and poses significant challenges in predictive understanding of climate change. We present a novel microscopy platform allowing observation of individual ice nucleation events at temperature range of 193-273 K and relative humidity relevant for ice formation in the atmospheric clouds. The approach utilizes a home built novel ice nucleation cell interfaced with Environmental Scanning Electron Microscope (IN-ESEM system). The IN-ESEM system is applied for direct observation of individual ice formation events, determining ice nucleation mechanisms, freezing temperatures, and relative humidity onsets. Reported microanalysis of the ice nucleating particles (INP) include elemental composition detected by the energy dispersed analysis of X-rays (EDX), and advanced speciation of the organic content in particles using scanning transmission x-ray microscopy with near edge X-ray absorption fine structure spectroscopy (STXM/NEXAFS). The performance of the IN-ESEM system is validated through a set of experiments with kaolinite particles with known ice nucleation propensity. We demonstrate an application of the IN-ESEM system to identify and characterize individual INP within a complex mixture of ambient particles.

  14. Probing nanoscale ferroelectricity by ultraviolet Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Tenne, Dmitri

    2007-03-01

    Conventional vibrational spectroscopies operating in visible and infrared range fail to measure the phonon spectra of nanoscale ferroelectric structures because of extremely weak signals and the overwhelming substrate contribution. In this talk, application of ultraviolet (UV) Raman spectroscopy for studies of lattice dynamics and ferroelectric phase transitions in nanoscale ferroelectrics will be presented. We demonstrate that UV Raman spectroscopy is an effective technique allowing the observation of phonons and determination of the ferroelectric phase transition temperature (Tc) in nanoscale ferroelectrics, specifically, BaTiO3/SrTiO3 superlattices having the ferroelectric BaTiO3 layers as thin as 1 unit cell, and single BaTiO3 layers as thin as 4 nm. BaTiO3/SrTiO3 superlattices and ultrathin BaTiO3 films studied were grown by molecular beam epitaxy on SrTiO3 as well as GdScO3 and DyScO3 substrates. Excellent epitaxial quality and atomically abrupt interfaces are evidenced by X-ray diffraction and high resolution transmission electron microscopy. UV Raman results show that one-unit-cell thick BaTiO3 layers in BaTiO3/SrTiO3 superlattices are ferroelectric with the Tc as high as 250 K, and induce the polarization in much thicker SrTiO3 layers adjacent to them. The Tc in superlattices was tuned by hundreds of degrees from ˜170 to 650 K by varying the thicknesses of BaTiO3 and SrTiO3 layers. Using scandate substrates enables growth of superlattices with systematically changed coherent strain, thus allowing studying the stress effect on the ferroelectric phase transitions. UV Raman data are supported by the thermodynamic calculations of polarization in superlattices as a function of temperature. The work was done in collaboration with A. Soukiassian, W. Tian, D.G. Schlom, Y.L. Li, L.-Q. Chen, X.X. Xi (Pennsylvania State University), A. Bruchhausen, A. Fainstein (Centro Atomico Bariloche & Instituto Balseiro, Argentina), R. S. Katiyar (University of Puerto Rico), A

  15. Probing Cancer Cell Metabolism Using NMR Spectroscopy.

    PubMed

    Hollinshead, Kate E R; Williams, Debbie S; Tennant, Daniel A; Ludwig, Christian

    2016-01-01

    Altered cellular metabolism is now accepted to be at the core of many diseases including cancer. Over the past 20 years, NMR has become a core technology to study these metabolic perturbations in detail. This chapter reviews current NMR-based methods for steady-state metabolism and, in particular, the use of non-radioactive stable isotope-enriched tracers. Opportunities and challenges for each method, such as 1D (1)H NMR spectroscopy and (13)C carbon-based NMR spectroscopic methods, are discussed. Ultimately, the combination of NMR and mass spectra as orthogonal technologies are required to compensate for the drawbacks of each technique when used singly are discussed. PMID:27325263

  16. Probing core-electron orbitals by scanning transmission electron microscopy and measuring the delocalization of core-level excitations

    NASA Astrophysics Data System (ADS)

    Jeong, Jong Seok; Odlyzko, Michael L.; Xu, Peng; Jalan, Bharat; Mkhoyan, K. Andre

    2016-04-01

    By recording low-noise energy-dispersive x-ray spectroscopy maps from crystalline specimens using aberration-corrected scanning transmission electron microscopy, it is possible to probe core-level electron orbitals in real space. Both the 1 s and 2 p orbitals of Sr and Ti atoms in SrTi O3 are probed, and their projected excitation potentials are determined. This paper also demonstrates experimental measurement of the electronic excitation impact parameter and the delocalization of an excitation due to Coulombic beam-orbital interaction.

  17. Improved optical fiber probes for scanning near field optical microscopy

    NASA Astrophysics Data System (ADS)

    Wheaton, Bryan R.

    2004-12-01

    The motivation behind this work stems from a combination of my interest in atomic force microscopy (AFM) and the need to apply AFM to several areas of glass research. AFM was used as the main characterization tool in the study of near-field scanning optical microscopy (NSOM) tip formation, evaluation of phase separation in glasses and copper oxide semiconductor film formation. The use of atomic force microscopy (AFM) to evaluate the evolving tip structure of an optical fiber probe for NSOM was studied. This study demonstrates the feasibility of predicting the final tip cone angle, without taking the etching process to completion. Cone angles reported in this study ranged from 58 to 152 degrees, depending on the fiber type and etch conditions. The ability to vary the probe cone angle, and utilize AFM to evaluate the cone angle that results from a set of etch conditions, are valuable additions to the development of NSOM fiber tips. The chemical and spatial variation of phase separated morphologies in glasses can range from a few angstroms to microns, often requiring very high magnification for detection. Historically phase separated glasses have been characterized by transmission electron microscopy (TEM), a time consuming and costly technique. Atomic force microscopy (AFM) provides an inexpensive alternative to TEM and has proven to be a powerful tool in the evaluation of type, degree and scale of phase separation in glasses down to the nanometer level. AFM was used to show that the thickness and uniformity of the CuO films grown in-situ on the surface of copper containing alkali borosilicate glasses increased with time and temperature, however an upper time limit was reached in which no further thickness increases were realized. Tenorite, cuprite and copper metal films were produced depending on the heat treatment environment. XPS was utilized to confirm that copper oxide film formation during heat treatments of glasses near Tg results from the oxidation of copper

  18. Electronic linearization of piezoelectric actuators and noise budget in scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Aloisi, G.; Santucci, A.; Carlà, M.; Dolci, D.; Lanzi, L.

    2006-07-01

    The maximum resolution achievable with a scanning probe microscope is limited by the probe size, by the mechanism of interaction with the sample, as is widely known, and by the electronic noise in the instrument. The evaluation of this noise for the three motion axes of a linearized high resolution scanning electrochemical microscope has been carried through and the intrinsic maximum resolution is discussed.

  19. Local tunneling decay length and Kelvin probe force spectroscopy

    NASA Astrophysics Data System (ADS)

    Albrecht, Florian; Fleischmann, Martin; Scheer, Manfred; Gross, Leo; Repp, Jascha

    2015-12-01

    In the past, current-distance spectroscopy has been widely applied to determine variations of the work function at surfaces. While for homogeneous sample areas this technique is commonly accepted to yield at least qualitative results, its applicability to atomic-scale variations has not been proven neither right nor wrong. Here we benchmark measurements of the current-distance decay constant against the well established Kelvin probe force spectroscopy for four distinctly different cases with atomic-scale variations of the local contact potential. The two techniques yield quite different results. Whereas the maps of the current-distance decay constant are consistent with being topographical artifacts, the Kelvin probe force spectroscopy maps show variations of the local contact potential difference in agreement with expected surface dipoles. This comparison clarifies that maps of the current-distance decay constant are not suited to directly characterize contact potential variations at surfaces on atomic length scales.

  20. Scanning Hall probe microscopy of supercurrents in YBCO films

    NASA Astrophysics Data System (ADS)

    Dinner, Rafael Baruch

    High-temperature superconductors were discovered 20 years ago, inspiring dreams of levitating trains fed by superconducting power lines. The cuprates, particularly YBa2Cu3O7-delta (YBCO), still promise to fulfill such applications, but must be made to carry higher current density, Jc, which is limited by the rapid onset of dissipation. The dissipation arises from the movement of magnetic vortices in the material, driven by the magnetic field of the current. It is therefore natural to use magnetic imaging to understand these limits on the current. Initially, I fix a mesoscopic ring of YBCO to a micro-Hall sensor and demonstrate that the sensor is capable of detecting small numbers of vortices. I then proceed with magnetic imaging, constructing a cryogenic scanning Hall probe microscope that combines a 1 x 4 cm scan range with 200 nm positioning resolution by coupling stepper motors to high-resolution drivers and reducing gears. It enables me to image an entire sample, then zoom in on regions of interest, down to the level of an individual quantized vortex. Applying this capability to current-carrying YBCO strips, I generate magnetic movies of the materials' periodic response to applied ac currents. From the movies, I reconstruct current density by inverting the Biot-Savart law, and electric field by approximating dB/dt and using Faraday's law. I thereby obtain complete, space- and time-resolved characterizations of the materials, including maps of ac power losses. After demonstrating this analysis on a single-crystal film, I image two "coated conductors"---YBCO grown on metal tape. I find relatively homogeneous flux penetration in a film grown by pulsed laser deposition (PLD) on an ion beam assisted deposition (IBAD) substrate, which contrasts with the weak-link behavior of grain boundaries in a film grown by metalorganic deposition (MOD) on rolling assisted biaxially textured substrate (RABiTS). Nonetheless, the in-plane meandering of the MOD film's boundaries

  1. Miniaturized magnetic-driven scanning probe for endoscopic optical coherence tomography.

    PubMed

    Pang, Ziwei; Wu, Jigang

    2015-06-01

    We designed and implemented a magnetic-driven scanning (MDS) probe for endoscopic optical coherence tomography (OCT). The probe uses an externally-driven tiny magnet in the distal end to achieve unobstructed 360-degree circumferential scanning at the side of the probe. The design simplifies the scanning part inside the probe and thus allows for easy miniaturization and cost reduction. We made a prototype probe with an outer diameter of 1.4 mm and demonstrated its capability by acquiring OCT images of ex vivo trachea and artery samples from a pigeon. We used a spectrometer-based Fourier-domain OCT system and the system sensitivity with our prototype probe was measured to be 91 dB with an illumination power of 850 μW and A-scan exposure time of 1 ms. The axial and lateral resolutions of the system are 6.5 μm and 8.1 μm, respectively. PMID:26114041

  2. Scanning thermal microscopy probe capable of simultaneous electrical imaging and the addition of diamond tip

    NASA Astrophysics Data System (ADS)

    Brown, E.; Hao, L.; Cox, D. C.; Gallop, J. C.

    2008-03-01

    Scanning Thermal Microscopy (SThM) is a scanning probe technique that allows the mapping of the thermal properties and/or temperature of a substrate. Developments in this scanning probe technique are of great importance to further the study of thermal transport at the micron and at the nano scale, for instance to better the understanding of heat transport in nano-electronic devices or energy transfer in biological systems. Here we describe: 1) the scanning technique developed to acquire simultaneous images of the topography, the thermal and electrical properties of the substrate using a commercially available Veeco SThM probe; 2) how the SThM probe was modified by mounting a micron-sized diamond pyramid on its tip in order to improve the probe's lateral resolution and the topography resolution tests on the performance of the modified probe.

  3. Multispectral scanning time-resolved fluorescence spectroscopy (TRFS) technique for intravascular diagnosis

    PubMed Central

    Xie, Hongtao; Bec, Julien; Liu, Jing; Sun, Yang; Lam, Matthew; Yankelevich, Diego R.; Marcu, Laura

    2012-01-01

    This study describes a scanning time-resolved fluorescence spectroscopy (TRFS) system designed to continuously acquire fluorescence emission and to reconstruct fluorescence lifetime images (FLIM) from a luminal surface by using a catheter-based optical probe with rotary joint and pull-back device. The ability of the system to temporally and spectrally resolve the fluorescence emission from tissue was validated using standard dyes and tissue phantoms (e.g., ex vivo pig aorta phantom). Current results demonstrate that this system is capable to reliably resolve the fluorescence emission of multiple fluorophores located in the lumen; and suggest its potential for intravascular detection of distinct biochemical features of atherosclerotic plaques. PMID:22808425

  4. PVD prepared molecular glass resists for scanning probe lithography

    NASA Astrophysics Data System (ADS)

    Neuber, Christian; Schmidt, Hans-Werner; Strohriegl, Peter; Wagner, Daniel; Krohn, Felix; Schedl, Andreas; Bonanni, Simon; Holzner, Felix; Rawlings, Colin; Dürig, Urs; Knoll, Armin W.

    2016-03-01

    In the presented work solvent-free film preparation from molecular glass resists, the evaluation of the patterning performance using thermal scanning probe lithography (tSPL) and an efficient etch transfer process are demonstrated. As the presented materials have a high tendency to crystallize and thus form crystalline films of bad quality when processed by solution casting, two component mixtures prepared by coevaporation were investigated. Stable amorphous films were obtained by selecting compatible material pairs for the coevaporation. One optimized material pair is based on trissubstituted, twisted resist materials with a distinct difference in molecular design. Here a high resolution tSPL prepared pattern of 18 nm half pitch in a 10 nm thick film is demonstrated. A further optimization is reported for "small" cubic silsequioxane molecules. Again single component films show independent to applied film preparation techniques bad film forming properties due to the high crystallinity of the symmetric cubic silsequioxane molecules. But coevaporation of the phenyl substituted octaphenylsilsequioxane combined with the fully aromatic 2,2',7,7'-tetraphenyl-9,9'-spirobi[fluorene] results in stable amorphous thin films. tSPL investigations demonstrate the patternability by writing high resolution line features of 20 nm half pitch. An important advantage of such a silicon rich resist material is that it can be directly converted to SiO2, yielding to a patterned hardmask of SiO2. This proof of principle is demonstrated and an efficient pattern transfer of 60 nm half pitch line into the underlying HM8006 is reported.

  5. A resonant scanning dipole-antenna probe for enhanced nanoscale imaging.

    PubMed

    Neumann, Lars; van 't Oever, Jorick; van Hulst, Niek F

    2013-11-13

    We present a scanning antenna probe that provides 35 nm optical hotspots with a 16-fold excitation enhancement. A resonant optical antenna, tuned to operation in the visible, is carved into the aluminum-coated scanning probe. The antenna resonances, field localization, excitation, and polarization response are probed in the near-field by scanning over single fluorescent nanobeads. At the same time, the distance-dependent coupling of the emission to the antenna mode is mapped. Good agreement with theory is obtained. The presented scanning antenna approach is useful for both nanoscale plasmonic mode imaging and (bio)imaging. PMID:24124987

  6. Coherence specific signal detection via chiral pump-probe spectroscopy.

    PubMed

    Holdaway, David I H; Collini, Elisabetta; Olaya-Castro, Alexandra

    2016-05-21

    We examine transient circular dichroism (TRCD) spectroscopy as a technique to investigate signatures of exciton coherence dynamics under the influence of structured vibrational environments. We consider a pump-probe configuration with a linearly polarized pump and a circularly polarized probe, with a variable angle θ between the two directions of propagation. In our theoretical formalism the signal is decomposed in chiral and achiral doorway and window functions. Using this formalism, we show that the chiral doorway component, which beats during the population time, can be isolated by comparing signals with different values of θ. As in the majority of time-resolved pump-probe spectroscopy, the overall TRCD response shows signatures of both excited and ground state dynamics. However, we demonstrate that the chiral doorway function has only a weak ground state contribution, which can generally be neglected if an impulsive pump pulse is used. These findings suggest that the pump-probe configuration of optical TRCD in the impulsive limit has the potential to unambiguously probe quantum coherence beating in the excited state. We present numerical results for theoretical signals in an example dimer system. PMID:27208941

  7. Scanning tunneling spectroscopy study of the Dirac spectrum of germanene

    NASA Astrophysics Data System (ADS)

    Walhout, C. J.; Acun, A.; Zhang, L.; Ezawa, M.; Zandvliet, H. J. W.

    2016-07-01

    The temperature dependence of the density of states of germanene, synthesized on Ge/Pt crystals, has been investigated with scanning tunneling spectroscopy. After correction for thermal broadening, a virtually perfect V-shaped density of states, which is a hallmark of a two-dimensional Dirac system, has been found. In an attempt to directly measure the energy dispersion relation via quasiparticle interference we have recorded spatial maps of the differential conductivity near the edges and defects of germanene. Unfortunately, we did not find any sign of Friedel oscillations. The absence of these Friedel oscillations hints to the occurrence of Klein tunneling.

  8. Scanning tunneling spectroscopy study of the Dirac spectrum of germanene.

    PubMed

    Walhout, C J; Acun, A; Zhang, L; Ezawa, M; Zandvliet, H J W

    2016-07-20

    The temperature dependence of the density of states of germanene, synthesized on Ge/Pt crystals, has been investigated with scanning tunneling spectroscopy. After correction for thermal broadening, a virtually perfect V-shaped density of states, which is a hallmark of a two-dimensional Dirac system, has been found. In an attempt to directly measure the energy dispersion relation via quasiparticle interference we have recorded spatial maps of the differential conductivity near the edges and defects of germanene. Unfortunately, we did not find any sign of Friedel oscillations. The absence of these Friedel oscillations hints to the occurrence of Klein tunneling. PMID:27227390

  9. Scanning probe microscopy investigation of complex-oxide heterostructures

    NASA Astrophysics Data System (ADS)

    Bi, Feng

    Advances in the growth of precisely tailored complex-oxide heterostructures have led to new emergent behavior and associated discoveries. One of the most successful examples consists of an ultrathin layer of LaAlO 3 (LAO) deposited on TiO2-terminated SrTiO3 (STO), where a high mobility quasi-two dimensional electron liquid (2DEL) is formed at the interface. Such 2DEL demonstrates a variety of novel properties, including field tunable metal-insulator transition, superconductivity, strong spin-orbit coupling, magnetic and ferroelectric like behavior. Particularly, for 3-unit-cell (3 u.c.) LAO/STO heterostructures, it was demonstrated that a conductive atomic force microscope (c-AFM) tip can be used to "write" or "erase" nanoscale conducting channels at the interface, making LAO/STO a highly flexible platform to fabricate novel nanoelectronics. This thesis is focused on scanning probe microscopy studies of LAO/STO properties. We investigate the mechanism of c-AFM lithography over 3 u.c. LAO/STO in controlled ambient conditions by using a vacuum AFM, and find that the water molecules dissociated on the LAO surface play a critical role during the c-AFM lithography process. We also perform electro-mechanical response measurements over top-gated LAO/STO devices. Simultaneous piezoresponse force microscopy (PFM) and capacitance measurements reveal a correlation between LAO lattice distortion and interfacial carrier density, which suggests that PFM could not only serve as a powerful tool to map the carrier density at the interface but also provide insight into previously reported frequency dependence of capacitance enhancement of top-gated LAO/STO structures. To study magnetism at the LAO/STO interface, magnetic force microscopy (MFM) and magnetoelectric force microscopy (MeFM) are carried out to search for magnetic signatures that depend on the carrier density at the interface. Results demonstrate an electronicallycontrolled ferromagnetic phase on top-gated LAO

  10. 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

  11. Principles and application of heterodyne scanning tunnelling spectroscopy.

    PubMed

    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

  12. Spatial-scanning hyperspectral imaging probe for bio-imaging applications

    NASA Astrophysics Data System (ADS)

    Lim, Hoong-Ta; Murukeshan, Vadakke Matham

    2016-03-01

    The three common methods to perform hyperspectral imaging are the spatial-scanning, spectral-scanning, and snapshot methods. However, only the spectral-scanning and snapshot methods have been configured to a hyperspectral imaging probe as of today. This paper presents a spatial-scanning (pushbroom) hyperspectral imaging probe, which is realized by integrating a pushbroom hyperspectral imager with an imaging probe. The proposed hyperspectral imaging probe can also function as an endoscopic probe by integrating a custom fabricated image fiber bundle unit. The imaging probe is configured by incorporating a gradient-index lens at the end face of an image fiber bundle that consists of about 50 000 individual fiberlets. The necessary simulations, methodology, and detailed instrumentation aspects that are carried out are explained followed by assessing the developed probe's performance. Resolution test targets such as United States Air Force chart as well as bio-samples such as chicken breast tissue with blood clot are used as test samples for resolution analysis and for performance validation. This system is built on a pushbroom hyperspectral imaging system with a video camera and has the advantage of acquiring information from a large number of spectral bands with selectable region of interest. The advantages of this spatial-scanning hyperspectral imaging probe can be extended to test samples or tissues residing in regions that are difficult to access with potential diagnostic bio-imaging applications.

  13. Pump and probe spectroscopy with continuous wave quantum cascade lasers

    SciTech Connect

    Kirkbride, James M. R.; Causier, Sarah K.; Dalton, Andrew R.; Ritchie, Grant A. D.; Weidmann, Damien

    2014-02-07

    This paper details infra-red pump and probe studies on nitric oxide conducted with two continuous wave quantum cascade lasers both operating around 5 μm. The pump laser prepares a velocity selected population in a chosen rotational quantum state of the v = 1 level which is subsequently probed using a second laser tuned to a rotational transition within the v = 2 ← v = 1 hot band. The rapid frequency scan of the probe (with respect to the molecular collision rate) in combination with the velocity selective pumping allows observation of marked rapid passage signatures in the transient absorption profiles from the polarized vibrationally excited sample. These coherent transient signals are influenced by the underlying hyperfine structure of the pump and probe transitions, the sample pressure, and the coherent properties of the lasers. Pulsed pump and probe studies show that the transient absorption signals decay within 1 μs at 50 mTorr total pressure, reflecting both the polarization and population dephasing times of the vibrationally excited sample. The experimental observations are supported by simulation based upon solving the optical Bloch equations for a two level system.

  14. Laser-induced breakdown spectroscopy based deminers' probe

    NASA Astrophysics Data System (ADS)

    Hauck, James P.; Walker, Mark; Hamadani, Siavosh; Bloomhardt, Natalie; Eagan, Justin

    2009-05-01

    We report on a prototype Laser Induced Breakdown Spectroscopy (LIBS) Deminers' Probe used to identify underground objects. We have built a prototype, and are in the process of developing a more advanced LIBS based Deminer' s Probe used to prod objects underground, and then sense them by creating a micro-plasma plume of the surface material and analyzing the spectrum of the emitted light to identify the object. It is expected that the Deminer will be able to eliminate many false positives, which consume most of the Deminers' time. SARA Fiber-Optics coupled LIBS system consists in a probe that can be inserted into the ground to provide a path for both the laser beam to the target, and for the micro-plasma plume fluorescence from the target to a spectrometer or spectrometers for analysis. The probe is closely modeled after the conventional Deminers' probe, resembling a saber. We have demonstrated that this simple system is capable of producing remarkably different spectra from different materials. Our next steps are to add a number of features to the Deminers' Probe. These include: a new optical configuration to increase the irradiance and fluence created by the pulsed laser at the target, a multiple channel fluorescence reception system that can increase the amount of light delivered to the spectrometers, a fluidic system to clear the detritus away from the probe tip, and a complete operational/control and readout system for the Deminer to use. Mine-lane tests are planned to be performed in the later part of 2009, or shortly thereafter.

  15. Using photoemission spectroscopy to probe a strongly interacting Fermi gas.

    PubMed

    Stewart, J T; Gaebler, J P; Jin, D S

    2008-08-01

    Ultracold atomic gases provide model systems in which to study many-body quantum physics. Recent experiments using Fermi gases have demonstrated a phase transition to a superfluid state with strong interparticle interactions. This system provides a realization of the 'BCS-BEC crossover' connecting the physics of Bardeen-Cooper-Schrieffer (BCS) superconductivity with that of Bose-Einstein condensates (BECs). Although many aspects of this system have been investigated, it has not yet been possible to measure the single-particle excitation spectrum (a fundamental property directly predicted by many-body theories). Here we use photoemission spectroscopy to directly probe the elementary excitations and energy dispersion in a strongly interacting Fermi gas of (40)K atoms. In the experiments, a radio-frequency photon ejects an atom from the strongly interacting system by means of a spin-flip transition to a weakly interacting state. We measure the occupied density of single-particle states at the cusp of the BCS-BEC crossover and on the BEC side of the crossover, and compare these results to that for a nearly ideal Fermi gas. We show that, near the critical temperature, the single-particle spectral function is dramatically altered in a way that is consistent with a large pairing gap. Our results probe the many-body physics in a way that could be compared to data for the high-transition-temperature superconductors. As in photoemission spectroscopy for electronic materials, our measurement technique for ultracold atomic gases directly probes low-energy excitations and thus can reveal excitation gaps and/or pseudogaps. Furthermore, this technique can provide an analogue of angle-resolved photoemission spectroscopy for probing anisotropic systems, such as atoms in optical lattice potentials. PMID:18685703

  16. Multifunctional cantilever-free scanning probe arrays coated with multilayer graphene.

    PubMed

    Shim, Wooyoung; Brown, Keith A; Zhou, Xiaozhu; Rasin, Boris; Liao, Xing; Mirkin, Chad A

    2012-11-01

    Scanning probe instruments have expanded beyond their traditional role as imaging or "reading" tools and are now routinely used for "writing." Although a variety of scanning probe lithography techniques are available, each one imposes different requirements on the types of probes that must be used. Additionally, throughput is a major concern for serial writing techniques, so for a scanning probe lithography technique to become widely applied, there needs to be a reasonable path toward a scalable architecture. Here, we use a multilayer graphene coating method to create multifunctional massively parallel probe arrays that have wear-resistant tips of uncompromised sharpness and high electrical and thermal conductivities. The optical transparency and mechanical flexibility of graphene allow this procedure to be used for coating exceptionally large, cantilever-free arrays that can pattern with electrochemical desorption and thermal, in addition to conventional, dip-pen nanolithography. PMID:23086161

  17. Multifunctional cantilever-free scanning probe arrays coated with multilayer graphene

    PubMed Central

    Shim, Wooyoung; Brown, Keith A.; Zhou, Xiaozhu; Rasin, Boris; Liao, Xing; Mirkin, Chad A.

    2012-01-01

    Scanning probe instruments have expanded beyond their traditional role as imaging or “reading” tools and are now routinely used for “writing.” Although a variety of scanning probe lithography techniques are available, each one imposes different requirements on the types of probes that must be used. Additionally, throughput is a major concern for serial writing techniques, so for a scanning probe lithography technique to become widely applied, there needs to be a reasonable path toward a scalable architecture. Here, we use a multilayer graphene coating method to create multifunctional massively parallel probe arrays that have wear-resistant tips of uncompromised sharpness and high electrical and thermal conductivities. The optical transparency and mechanical flexibility of graphene allow this procedure to be used for coating exceptionally large, cantilever-free arrays that can pattern with electrochemical desorption and thermal, in addition to conventional, dip-pen nanolithography. PMID:23086161

  18. Carbon Nanotube Tip Probes: Stability and Lateral Resolution in Scanning Probe Microscopy and Application to Surface Science to Semiconductors

    NASA Technical Reports Server (NTRS)

    Nguyen, Cattien V.; Chao, Kuo-Jen; Stevens, Ramsey M. D.; Delzeit, Lance; Cassell, Alan; Han, Jie; Meyyappan, M.; Arnold, James (Technical Monitor)

    2001-01-01

    In this paper we present results on the stability and lateral resolution capability of carbon nanotube (CNT) scanning probes as applied to atomic force microscopy (AFM). Surface topography images of ultra-thin films (2-5 nm thickness) obtained with AFM are used to illustrate the lateral resolution capability of single-walled carbon nanotube probes. Images of metal films prepared by ion beam sputtering exhibit grain sizes ranging from greater than 10 nm to as small as approximately 2 nm for gold and iridium respectively. In addition, imaging stability and lifetime of multi-walled carbon nanotube scanning probes are studied on a relatively hard surface of silicon nitride (Si3N4). AFM images Of Si3N4 surface collected after more than 15 hrs of continuous scanning show no detectable degradation in lateral resolution. These results indicate the general feasibility of CNT tips and scanning probe microscopy for examining nanometer-scale surface features of deposited metals as well as non-conductive thin films. AFM coupled with CNT tips offers a simple and nondestructive technique for probing a variety of surfaces, and has immense potential as a surface characterization tool in integrated circuit manufacturing.

  19. Metamaterial-inspired miniaturized microwave edge coupled surface scanning probe

    NASA Astrophysics Data System (ADS)

    Wiwatcharagoses, Nophadon; Park, Kyoung Y.; Chahal, Premjeet; Udpa, Lalita

    2013-01-01

    This paper introduces a new concept on sub-wavelength resolution imaging and surface scanning using metamaterial based near field sensor array. Multiple split ring resonator structures (SRRs), having different band stop frequencies, are implemented in a microstrip transmission line configuration. A mirror image copy of these resonators is also incorporated on the transmission line to achieve built in frequency references. A smart card is scanned to detect buried antenna and Si chip within the plastic card.

  20. Magnetic hydroxyapatite coatings as a new tool in medicine: A scanning probe investigation.

    PubMed

    Gambardella, A; Bianchi, M; Kaciulis, S; Mezzi, A; Brucale, M; Cavallini, M; Herrmannsdoerfer, T; Chanda, G; Uhlarz, M; Cellini, A; Pedna, M F; Sambri, V; Marcacci, M; Russo, A

    2016-05-01

    Hydroxyapatite films enriched with magnetite have been fabricated via a Pulsed Plasma Deposition (PPD) system with the final aim of representing a new platform able to disincentivate bacterial adhesion and biofilm formation. The chemical composition and magnetic properties of films were respectively examined by X-ray photoelectron spectroscopy (XPS) and Superconducting Quantum Interference Device (SQUID) measurements. The morphology and conductive properties of the magnetic films were investigated via a combination of scanning probe technologies including atomic force microscopy (AFM), electrostatic force microscopy (EFM), and scanning tunneling microscopy (STM). Interestingly, the range of adopted techniques allowed determining the preservation of the chemical composition and magnetic properties of the deposition target material while STM analysis provided new insights on the presence of surface inhomogeneities, revealing the presence of magnetite-rich islands over length scales compatible with the applications. Finally, preliminary results of bacterial adhesion tests, indicated a higher ability of magnetic hydroxyapatite films to reduce Escherichia coli adhesion at 4h from seeding compared to control hydroxyapatite films. PMID:26952445

  1. Invited review article: A 10 mK scanning probe microscopy facility.

    PubMed

    Song, Young Jae; Otte, Alexander F; Shvarts, Vladimir; Zhao, Zuyu; Kuk, Young; Blankenship, Steven R; Band, Alan; Hess, Frank M; Stroscio, Joseph A

    2010-12-01

    We describe the design, development and performance of a scanning probe microscopy (SPM) 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. Subpicometer 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, which include growth chambers for metal and semiconductor samples, a field-ion microscope for tip characterization, and a fully independent additional quick access low temperature scanning tunneling microscope (STM) and atomic force microscope (AFM) system. To characterize the system, we present the cooling performance of the DR, vibrational, tunneling current, and tip-sample displacement noise measurements. In addition, we show the spectral resolution capabilities with tunneling spectroscopy results obtained on an epitaxial graphene sample resolving the quantum Landau levels in a magnetic field, including the sublevels corresponding to the lifting of the electron spin and valley degeneracies. PMID:21198007

  2. Probing battery chemistry with liquid cell electron energy loss spectroscopy

    DOE PAGESBeta

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; Unocic, Kinga A.; Sacci, Robert L.; Dudney, Nancy J.; More, Karren Leslie; Aguiar, Jeffery A.

    2015-09-15

    Electron energy loss spectroscopy (EELS) was used to determine the chemistry and oxidation state of LiMn2O4 and Li4Ti5O12 thin film battery electrodes in liquid cells for in situ scanning/transmission electron microscopy (S/TEM). Using the L2,3 white line intensity ratio method we determine the oxidation state of Mn and Ti in a liquid electrolyte solvent and discuss experimental parameters that influence measurement sensitivity.

  3. Cryogenic Scanning Tunneling Spectroscopy of Superconducting Iron Chalcogenide Single Crystals

    NASA Astrophysics Data System (ADS)

    Wei, J. Y. T.; Fridman, Igor; Yeh, Kuo-Wei; Wu, Maw-Kuen; Hu, Rongwei; Petrovic, C.

    2011-03-01

    We report scanning tunneling spectroscopy measurements on the iron-based superconductors of the ``11'' family including Fe 1-y Te 1-x Se x and Fe 1-y Te 1-x Sx . Conductance spectra and atomically-resolved images are obtained on single crystals down to 300 mK. A gap-like structure is observed, showing an asymmetric spectral background, non-trivial spatial variation and temperature dependence. We discuss our data in terms of possible gap anisotropy and doping inhomogeneities, and in relation to other recent spectroscopic measurements on iron-based superconductors. Work supported by NSERC, CFI/OIT, CIFAR, Taiwan National Science Council, U.S. DOE and Brookhaven Science Associates (No. DE-Ac02-98CH10886), and in part by the Center for Emergent Superconductivity, an Energy Frontier Research Center.

  4. Moessbauer spectroscopy and scanning electron microscopy of the Murchison meteorite

    NASA Technical Reports Server (NTRS)

    Brown, Christopher L.; Oliver, Frederick W.; Hammond, Ernest C., Jr.

    1989-01-01

    Meteorites provide a wealth of information about the solar system's formation, since they have similar building blocks as the Earth's crust but have been virtually unaltered since their formation. Some stony meteorites contain minerals and silicate inclusions, called chondrules, in the matrix. Utilizing Moessbauer spectroscopy, we identified minerals in the Murchison meteorite, a carbonaceous chondritic meteorite, by the gamma ray resonance lines observed. Absorption patterns of the spectra were found due to the minerals olivine and phyllosilicate. We used a scanning electron microscope to describe the structure of the chondrules in the Murchison meteorite. The chondrules were found to be deformed due to weathering of the meteorite. Diameters varied in size from 0.2 to 0.5 mm. Further enhancement of the microscopic imagery using a digital image processor was used to describe the physical characteristics of the inclusions.

  5. Scanning Gate Spectroscopy and its Application to Carbon Nanotube Defects

    PubMed Central

    Hunt, Steven R.; Wan, Danny; Khalap, Vaikunth R.; Corso, Brad L.; Collins, Philip G.

    2011-01-01

    A variation of scanning gate microscopy (SGM) is demonstrated in which this imaging mode is extended into an electrostatic spectroscopy. Continuous variation of the SGM probe’s electrostatic potential is used to directly resolve the energy spectrum of localized electronic scattering in functioning, molecular scale devices. The technique is applied to the energy-dependent carrier scattering that occurs at defect sites in carbon nanotube transistors, and fitting energy-resolved experimental data to a simple transmission model determines the electronic character of each defect site. For example, a phenolic type of covalent defect is revealed to produce a tunnel barrier 0.1 eV high and 0.5 nm wide. PMID:21280660

  6. Scanning Tunneling Microscopy and Spectroscopy of Compound Semiconductor Heterojunctions

    NASA Astrophysics Data System (ADS)

    Gwo, Shang-, Jr.

    Scanning tunneling microscopy and spectroscopy (STM/S) were used to investigate the structural and electronic properties of III-V compound semiconductor heterojunctions in cross section. The most important properties of heterostructures can now be measured in real space with unprecedented resolution. By using prototypical Al_{0.3}Ga _{0.7}As/GaAs heterojunction and GaAs pn-junction systems, we demonstrate the unique capability of STM/S to precisely map out the detailed band structure across semiconductor junctions with nanometer resolution. An ultra-high vacuum STM system was designed and constructed in our laboratory for this work. The details of this system as well as the methodology used for the cross-sectional study are presented here. Because of its capability to provide valuable information on solid/solid interfaces, the cross-sectional STM/S characterization method reported here may have an important technological impact as device miniaturization continues.

  7. Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system.

    PubMed

    Johansson, Johannes D; Mireles, Miguel; Morales-Dalmau, Jordi; Farzam, Parisa; Martínez-Lozano, Mar; Casanovas, Oriol; Durduran, Turgut

    2016-02-01

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma. PMID:26977357

  8. Scanning, non-contact, hybrid broadband diffuse optical spectroscopy and diffuse correlation spectroscopy system

    PubMed Central

    Johansson, Johannes D.; Mireles, Miguel; Morales-Dalmau, Jordi; Farzam, Parisa; Martínez-Lozano, Mar; Casanovas, Oriol; Durduran, Turgut

    2016-01-01

    A scanning system for small animal imaging using non-contact, hybrid broadband diffuse optical spectroscopy (ncDOS) and diffuse correlation spectroscopy (ncDCS) is presented. The ncDOS uses a two-dimensional spectrophotometer retrieving broadband (610-900 nm) spectral information from up to fifty-seven source-detector distances between 2 and 5 mm. The ncDCS data is simultaneously acquired from four source-detector pairs. The sample is scanned in two dimensions while tracking variations in height. The system has been validated with liquid phantoms, demonstrated in vivo on a human fingertip during an arm cuff occlusion and on a group of mice with xenoimplanted renal cell carcinoma. PMID:26977357

  9. Two Simple Classroom Demonstrations for Scanning Probe Microscopy Based on a Macroscopic Analogy

    ERIC Educational Resources Information Center

    Hajkova, Zdenka; Fejfar, Antonin; Smejkal, Petr

    2013-01-01

    This article describes two simple classroom demonstrations that illustrate the principles of scanning probe microscopy (SPM) based on a macroscopic analogy. The analogy features the bumps in an egg carton to represent the atoms on a chemical surface and a probe that can be represented by a dwarf statue (illustrating an origin of the prefix…

  10. Fast scanning probe for the NSTX spherical tokamak.

    PubMed

    Boedo, J A; Crocker, N; Chousal, L; Hernandez, R; Chalfant, J; Kugel, H; Roney, P; Wertenbaker, J

    2009-12-01

    We describe a fast reciprocating Langmuir probe and drive system, which has four main new features: (1) use of high-temperature, vacuum, circuit boards instead of cables to reduce weight and increase to 21 the number of possible connections, (2) rotatable and removable shaft, (3) 10 tip construction with designed hardware bandwidth up to 10 MHz, and (4) a detachable and modular tip assembly for easy maintenance. The probe is mounted in a fast pneumatic drive capable of speeds approximately 7 m/s and approximately 20g's acceleration in order to reach the scrape-off layer (SOL) and pedestal regions and remain inserted long enough to obtain good statistics while minimizing the heat deposition to the tips and head in a power density environment of 1-10 MW/m2. The National Spherical Torus Experiment SOL features electron temperature, T(e) approximately 10-30 eV, and electron density, n(e) approximately 0.1-5x10(12) cm(-3) while the pedestal features n(e) approximately 0.5-1.5x10(13) cm(-3) and T(e) approximately 30-150 eV. The probe described here has ten tips which obtain a wide spectrum of plasma parameters: electron temperature profile T(e)(r), electron density profile n(e)(r) and Mach number profile M(r), floating potential V(f)(r), poloidal and radial electric field profiles E(theta)(r) and E(rho)(r), saturation current profile I(sat)(r), and their fluctuations up to 3 MHz. We describe the probe and show representative radial profiles of various parameters. PMID:20073119

  11. Fast scanning probe for the NSTX spherical tokamak

    NASA Astrophysics Data System (ADS)

    Boedo, J. A.; Crocker, N.; Chousal, L.; Hernandez, R.; Chalfant, J.; Kugel, H.; Roney, P.; Wertenbaker, J.; NSTX Team

    2009-12-01

    We describe a fast reciprocating Langmuir probe and drive system, which has four main new features: (1) use of high-temperature, vacuum, circuit boards instead of cables to reduce weight and increase to 21 the number of possible connections, (2) rotatable and removable shaft, (3) 10 tip construction with designed hardware bandwidth up to 10 MHz, and (4) a detachable and modular tip assembly for easy maintenance. The probe is mounted in a fast pneumatic drive capable of speeds ˜7 m/s and ˜20g's acceleration in order to reach the scrape-off layer (SOL) and pedestal regions and remain inserted long enough to obtain good statistics while minimizing the heat deposition to the tips and head in a power density environment of 1-10 MW/m2. The National Spherical Torus Experiment SOL features electron temperature, Te˜10-30 eV, and electron density, ne˜0.1-5×1012 cm-3 while the pedestal features ne˜0.5-1.5×1013 cm-3 and Te˜30-150 eV. The probe described here has ten tips which obtain a wide spectrum of plasma parameters: electron temperature profile Te(r), electron density profile ne(r) and Mach number profile M(r ), floating potential Vf(r), poloidal and radial electric field profiles Eθ(r) and Eρ(r), saturation current profile Isat(r), and their fluctuations up to 3 MHz. We describe the probe and show representative radial profiles of various parameters.

  12. Broadband pump-probe spectroscopy at 20-MHz modulation frequency.

    PubMed

    Preda, Fabrizio; Kumar, Vikas; Crisafi, Francesco; Figueroa Del Valle, Diana Gisell; Cerullo, Giulio; Polli, Dario

    2016-07-01

    We introduce an innovative high-sensitivity broadband pump-probe spectroscopy system, based on Fourier-transform detection, operating at 20-MHz modulation frequency. A common-mode interferometer employing birefringent wedges creates two phase-locked delayed replicas of the broadband probe pulse, interfering at a single photodetector. A single-channel lock-in amplifier demodulates the interferogram, whose Fourier transform provides the differential transmission spectrum. Our approach combines broad spectral coverage with high sensitivity, due to high-frequency modulation and detection. We demonstrate its performances by measuring two-dimensional differential transmission maps of a carbon nanotubes sample, simultaneously acquiring the signal over the entire 950-1350 nm range with 2.7·10-6  rms noise over 1.5 s integration time. PMID:27367078

  13. Optical depletion spectroscopy for probing evaporatively cooled OH

    NASA Astrophysics Data System (ADS)

    Hummon, Matthew; Wu, Hao; Stuhl, Benjamin; Reens, David; Yeo, Mark; Ye, Jun

    2013-05-01

    Pulsed laser induced fluorescence (PLIF) measurements provide a sensitive probe for the detection of molecular species. However, the broad linewidth of the pulsed lasers used for molecular excitation obscures spectral information useful for determination of molecule temperature. This limitation can be overcome by the use of a second, narrowband source of radiation that can deplete a subset of the molecules detected using PLIF, and a high resolution depletion spectrum can be obtained. In the past, we have demonstrated the use of microwave depletion spectroscopy to measure magnetically trapped, evaporatively cooled OH temperatures in the range of 5-50 mK. The lower limit of 5 mK is set by the details of the microwave transition. Here we present temperature measurements of trapped OH using an optical depletion technique, which is in principle capable of probing temperatures as low as 50 microkelvin. We acknowledge funding from the NSF Physics Frontier Center, NIST, DOE, and the AFOSR MURI on Cold Molecules.

  14. Nanoscale infrared spectroscopy as a non-destructive probe of extraterrestrial samples.

    PubMed

    Dominguez, Gerardo; Mcleod, A S; Gainsforth, Zack; Kelly, P; Bechtel, Hans A; Keilmann, Fritz; Westphal, Andrew; Thiemens, Mark; Basov, D N

    2014-01-01

    Advances in the spatial resolution of modern analytical techniques have tremendously augmented the scientific insight gained from the analysis of natural samples. Yet, while techniques for the elemental and structural characterization of samples have achieved sub-nanometre spatial resolution, infrared spectral mapping of geochemical samples at vibrational 'fingerprint' wavelengths has remained restricted to spatial scales >10 μm. Nevertheless, infrared spectroscopy remains an invaluable contactless probe of chemical structure, details of which offer clues to the formation history of minerals. Here we report on the successful implementation of infrared near-field imaging, spectroscopy and analysis techniques capable of sub-micron scale mineral identification within natural samples, including a chondrule from the Murchison meteorite and a cometary dust grain (Iris) from NASA's Stardust mission. Complementary to scanning electron microscopy, energy-dispersive X-ray spectroscopy and transmission electron microscopy probes, this work evidences a similarity between chondritic and cometary materials, and inaugurates a new era of infrared nano-spectroscopy applied to small and invaluable extraterrestrial samples. PMID:25487365

  15. Atomic-Scale Imaging and Spectroscopy Using Scanning Tunneling Microscopy.

    NASA Astrophysics Data System (ADS)

    Youngquist, Michael George

    Advances in scanning tunneling microscopy (STM) instrumentation and applications are presented. An ultrahigh vacuum (UHV) scanning tunneling microscope incorporating computer-controlled two-dimensional sample translation and in vacuo tip and sample transfer was developed. Its performance is documented through large-area and atomic -resolution imaging of highly stepped Si(111) 7 x 7 reconstructed surfaces and physisorbed clusters on graphite. An STM with automated approach and intra-Dewar spring suspension was developed for operation in cryogenic liquids. A high performance digital signal processor (DSP) based control system was constructed, and software with advanced spectroscopic imaging and data processing capabilities was developed. The feasibility of individual-molecule vibrational spectroscopy via STM-detected inelastic electron tunneling is assessed. In preliminary experiments, a low-temperature STM was used for energy gap and phonon spectroscopy of superconducting Pb films. The first STM observation of phonon density of states effects in a superconductor is reported. A systematic UHV STM imaging and spectroscopy study of 2H-MoS_2 was conducted. Atom -resolved images from three distinct imaging modes are presented. Occasional appearance of negative differential resistance (NDR) in I vs. V measurements is traced to changing tip electronic structure rather than localized surface states. Other potential NDR mechanisms are discussed including electron trap charging and resonant tunneling through a double-barrier quantum well structure arising from layer separation in the MoS_2 crystal. DNA was imaged at atomic resolution with a UHV STM. Images show double-helical structure, base pairs, and atomic-scale substructure. Experimental STM profiles have atom-for-atom correlation with the A-DNA van der Waals surface. This work demonstrates the potential of the STM for characterization of large biomolecular structures. Impurity-pinned steps on silicon and gold surfaces

  16. Characterization of charge motion in Poly(3-alkylthiophene) field effect transistors with Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Moscatello, Jason P.; Patterson, Morgen; Davis, Andrew R.; Carter, Kenneth R.; Aidala, Katherine E.

    2014-03-01

    Poly(3-hexylthiophene) (P3HT) is a promising conductive organic polymer for applications such as organic FETs and photovoltaics. Key to proper utilization of P3HT is the understanding of how charges move and are trapped in the polymer, which directly affects the mobility of the charges as well as device efficiency. Scanning probe techniques, such as Kelvin Probe Force Microscopy, offer the advantage of being able to observe charges and local potentials down to the nano-scale. We present our work using scanning probe techniques to study charge injection and flow through P3HT FETs.

  17. Probing Intermolecular Interaction through Thermal-Lens Spectroscopy

    PubMed Central

    Bhattacharyya, Indrajit; Kumar, Pardeep; Goswami, Debabrata

    2013-01-01

    Binary liquid mixtures are studied using femtosecond pump–probe thermal-lens (TL) spectroscopy. Changes in the measured TL signals as a function of relative concentration of binary mixtures show that these result from a combined effect of physical and molecular properties of the constituent binary liquids. The experimental TL values deviate from the ones calculated from phenomenological equations. These, we argue, are due to an underestimation of the influence of molecular interactions when the TL signals are calculated by using physical parameters only. PMID:21166402

  18. Probing microscopic mechanical properties of hard tissues with Brillouin spectroscopy

    NASA Astrophysics Data System (ADS)

    Meng, Zhaokai; Yakovlev, Vladislav V.

    2015-02-01

    Mechanical properties of hard tissues play an important role in understanding underlying biological structures, as well as assessing the quality of artificial bone replacement materials. In this study, we employed Brillouin spectroscopy as a non-invasive approach to probe the microscopic elasticity of hard tissues, such as bones. Brillouin spectra were collected using a background free virtually imaged phased array spectrometer. As a reference, Raman spectra were also acquired for each imaging point. Experimental results reveal a positive correlation between the local concentration of the mineral content and the corresponding tissue stiffness, assessed through a Brillouin shift.

  19. Handheld scanning probes for optical coherence tomography: developments, applications, and perspectives

    NASA Astrophysics Data System (ADS)

    Duma, V.-F.; Demian, D.; Sinescu, C.; Cernat, R.; Dobre, G.; Negrutiu, M. L.; Topala, F. I.; Hutiu, Gh.; Bradu, A.; Podoleanu, A. G.

    2016-03-01

    We present the handheld scanning probes that we have recently developed in our current project for biomedical imaging in general and for Optical Coherence Tomography (OCT) in particular. OCT is an established, but dynamic imagistic technique based on laser interferometry, which offers micrometer resolutions and millimeters penetration depths. With regard to existing devices, the newly developed handheld probes are simple, light and relatively low cost. Their design is described in detail to allow for the reproduction in any lab, including for educational purposes. Two probes are constructed almost entirely from off-the-shelf components, while a third, final variant is constructed with dedicated components, in an ergonomic design. The handheld probes have uni-dimensional (1D) galvanometer scanners therefore they achieve transversal sections through the biological sample investigated - in contrast to handheld probes equipped with bi-dimensional (2D) scanners that can also achieve volumetric (3D) reconstructions of the samples. These latter handheld probes are therefore also discussed, as well as the possibility to equip them with galvanometer 2D scanners or with Risley prisms. For galvanometer scanners the optimal scanning functions studied in a series of previous works are pointed out; these functions offer a higher temporal efficiency/duty cycle of the scanning process, as well as artifact-free OCT images. The testing of the handheld scanning probes in dental applications is presented, for metal ceramic prosthesis and for teeth.

  20. Nano-material processing with laser radiation in the near field of a scanning probe tip

    NASA Astrophysics Data System (ADS)

    Jersch, J.; Demming, F.; Hildenhagen, J.; Dickmann, K.

    1998-04-01

    We report preliminary results of using a scanning probe microscope/laser combination to perform nanostructuring on insulator and metal surfaces in air. This technique enables processing of structures with a lateral resolution of approximately 10 nm. In this paper we present our last structuring results with both scanning tunnelling and scanning force microscopy. Some possible interaction mechanisms responsible for the structuring will be discussed.

  1. Wall scanning probe for high-field side plasma measurements on Alcator C-Mod.

    PubMed

    Smick, Noah; LaBombard, Brian

    2009-02-01

    A new, high-field side scanning probe has been added to Alcator C-Mod's complement of edge diagnostics. The wall scanning probe is designed to provide all the benefits of a linear plunge, multielectrode scanning probe while working from the confined space of the inner tokamak wall. The drive mechanism is an embedded coil which produces a torque with the ambient toroidal magnetic field when energized, thus allowing the probe to plunge to different preprogramed depths at different times during a plasma discharge. The probe tip is designed for easy replacement and is presently configured to operate as a modified, high heat-flux "Gundestrup-type" probe with four tungsten electrodes. The probe has demonstrated the ability to obtain cross-field profiles for electron temperature, density, floating potential, and plasma flow information (parallel and perpendicular to B) up to a depth of a few millimiters inside the last-closed flux surface in standard C-Mod discharges. The tungsten-tipped probe has proved very robust and shows little or no damage though it routinely handles surface heat fluxes on the order of 100 MW/m(2) at peak insertion. PMID:19256643

  2. Double-resonance probe for near-field scanning optical microscopy

    NASA Astrophysics Data System (ADS)

    Cherkun, A. P.; Serebryakov, D. V.; Sekatskii, S. K.; Morozov, I. V.; Letokhov, V. S.

    2006-03-01

    A surface-contact transducer is developed for scanning probe microscopes, whose operating principle is based on the coincidence between the resonance frequency of a 32kHz quartz tuning fork and that of the probe attached to it. This allows the transducer to have a high quality factor and, if the vibration amplitude of the probe tip exceeds that of the tuning fork prongs, materially improves its force sensitivity. The resonance transducer proposed by us has an experimentally verified force sensitivity of 8pN (rms) in the 300Hz frequency band, which is of the same order of magnitude as the sensitivity of atomic force microscope (AFM) cantilever sensors. The manufacture of such transducers equipped with optical-fiber probes for near-field scanning optical microscopy and with tungsten probes for AFM is described as an example.

  3. Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes

    SciTech Connect

    Li, Y.; Zakharov, D.; Zhao, S.; Tappero, R.; Jung, U.; Elsen, A.; Baumann, Ph.; Nuzzo, R. G.; Stach, E. A.; Frenkel, A. I.

    2015-06-29

    Understanding how heterogeneous catalysts change size, shape and structure during chemical reactions is limited by the paucity of methods for studying catalytic ensembles in working state, that is, in operando conditions. Here by a correlated use of synchrotron X-ray absorption spectroscopy and scanning transmission electron microscopy in operando conditions, we quantitatively describe the complex structural dynamics of supported Pt catalysts exhibited during an exemplary catalytic reaction—ethylene hydrogenation. This work exploits a microfabricated catalytic reactor compatible with both probes. The results demonstrate dynamic transformations of the ensemble of Pt clusters that spans a broad size range throughout changing reaction conditions. Lastly, this method is generalizable to quantitative operando studies of complex systems using a wide variety of X-ray and electron-based experimental probes.

  4. Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes.

    PubMed

    Li, Y; Zakharov, D; Zhao, S; Tappero, R; Jung, U; Elsen, A; Baumann, Ph; Nuzzo, R G; Stach, E A; Frenkel, A I

    2015-01-01

    Understanding how heterogeneous catalysts change size, shape and structure during chemical reactions is limited by the paucity of methods for studying catalytic ensembles in working state, that is, in operando conditions. Here by a correlated use of synchrotron X-ray absorption spectroscopy and scanning transmission electron microscopy in operando conditions, we quantitatively describe the complex structural dynamics of supported Pt catalysts exhibited during an exemplary catalytic reaction-ethylene hydrogenation. This work exploits a microfabricated catalytic reactor compatible with both probes. The results demonstrate dynamic transformations of the ensemble of Pt clusters that spans a broad size range throughout changing reaction conditions. This method is generalizable to quantitative operando studies of complex systems using a wide variety of X-ray and electron-based experimental probes. PMID:26119246

  5. Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes

    NASA Astrophysics Data System (ADS)

    Li, Y.; Zakharov, D.; Zhao, S.; Tappero, R.; Jung, U.; Elsen, A.; Baumann, Ph.; Nuzzo, R. G.; Stach, E. A.; Frenkel, A. I.

    2015-06-01

    Understanding how heterogeneous catalysts change size, shape and structure during chemical reactions is limited by the paucity of methods for studying catalytic ensembles in working state, that is, in operando conditions. Here by a correlated use of synchrotron X-ray absorption spectroscopy and scanning transmission electron microscopy in operando conditions, we quantitatively describe the complex structural dynamics of supported Pt catalysts exhibited during an exemplary catalytic reaction--ethylene hydrogenation. This work exploits a microfabricated catalytic reactor compatible with both probes. The results demonstrate dynamic transformations of the ensemble of Pt clusters that spans a broad size range throughout changing reaction conditions. This method is generalizable to quantitative operando studies of complex systems using a wide variety of X-ray and electron-based experimental probes.

  6. Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes

    PubMed Central

    Li, Y.; Zakharov, D.; Zhao, S.; Tappero, R.; Jung, U.; Elsen, A.; Baumann, Ph.; Nuzzo, R.G.; Stach, E.A.; Frenkel, A.I.

    2015-01-01

    Understanding how heterogeneous catalysts change size, shape and structure during chemical reactions is limited by the paucity of methods for studying catalytic ensembles in working state, that is, in operando conditions. Here by a correlated use of synchrotron X-ray absorption spectroscopy and scanning transmission electron microscopy in operando conditions, we quantitatively describe the complex structural dynamics of supported Pt catalysts exhibited during an exemplary catalytic reaction—ethylene hydrogenation. This work exploits a microfabricated catalytic reactor compatible with both probes. The results demonstrate dynamic transformations of the ensemble of Pt clusters that spans a broad size range throughout changing reaction conditions. This method is generalizable to quantitative operando studies of complex systems using a wide variety of X-ray and electron-based experimental probes. PMID:26119246

  7. Complex structural dynamics of nanocatalysts revealed in Operando conditions by correlated imaging and spectroscopy probes

    DOE PAGESBeta

    Li, Y.; Zakharov, D.; Zhao, S.; Tappero, R.; Jung, U.; Elsen, A.; Baumann, Ph.; Nuzzo, R. G.; Stach, E. A.; Frenkel, A. I.

    2015-06-29

    Understanding how heterogeneous catalysts change size, shape and structure during chemical reactions is limited by the paucity of methods for studying catalytic ensembles in working state, that is, in operando conditions. Here by a correlated use of synchrotron X-ray absorption spectroscopy and scanning transmission electron microscopy in operando conditions, we quantitatively describe the complex structural dynamics of supported Pt catalysts exhibited during an exemplary catalytic reaction—ethylene hydrogenation. This work exploits a microfabricated catalytic reactor compatible with both probes. The results demonstrate dynamic transformations of the ensemble of Pt clusters that spans a broad size range throughout changing reaction conditions. Lastly,more » this method is generalizable to quantitative operando studies of complex systems using a wide variety of X-ray and electron-based experimental probes.« less

  8. 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.

  9. Pump probe spectroscopy of quasiparticle dynamics in cuprate superconductors

    SciTech Connect

    Segre, Gino P.

    2001-05-01

    Pump probe spectroscopy is used to examine the picosecond response of a BSCCO thin film, and two YBCO crystals in the near infrared. The role of pump fluence and temperature have been closely examined in an effort to clarify the mechanism by which the quasiparticles rejoin the condensate. BSCCO results suggest that the recombination behavior is consistent with the d-wave density of states in that quasiparticles appear to relax to the nodes immediately before they rejoin the condensate. The first substantial investigation of polarized pump probe response in detwinned YBCO crystals is also reported. Dramatic doping dependent anisotropies along the a and b axes are observed in time and temperature resolved studies. Among many results, we highlight the discovery of an anomalous temperature and time dependence of a- axis response in optimally doped YBCO. We also report on the first observation of the photoinduced response in a magnetic field. We find the amplitude of the response, and in some cases, the dynamics considerably changed with the application of a 6T field. Finally, we speculate on two of the many theoretical directions stimulated by our results. We find that the two-fluid model suggests a mechanism to explain how changes at very low energies are visible to a high-energy probe. Also discussed are basic recombination processes which may play a role in the observed decay.

  10. Probing battery chemistry with liquid cell electron energy loss spectroscopy.

    PubMed

    Unocic, Raymond R; Baggetto, Loïc; Veith, Gabriel M; Aguiar, Jeffery A; Unocic, Kinga A; Sacci, Robert L; Dudney, Nancy J; More, Karren L

    2015-11-25

    We demonstrate the ability to apply electron energy loss spectroscopy (EELS) to follow the chemistry and oxidation states of LiMn2O4 and Li4Ti5O12 battery electrodes within a battery solvent. This is significant as the use and importance of in situ electrochemical cells coupled with a scanning/transmission electron microscope (S/TEM) has expanded and been applied to follow changes in battery chemistry during electrochemical cycling. We discuss experimental parameters that influence measurement sensitivity and provide a framework to apply this important analytical method to future in situ electrochemical studies. PMID:26404766

  11. Probing battery chemistry with liquid cell electron energy loss spectroscopy

    SciTech Connect

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; Unocic, Kinga A.; Sacci, Robert L.; Dudney, Nancy J.; More, Karren Leslie; Aguiar, Jeffery A.

    2015-09-15

    Electron energy loss spectroscopy (EELS) was used to determine the chemistry and oxidation state of LiMn2O4 and Li4Ti5O12 thin film battery electrodes in liquid cells for in situ scanning/transmission electron microscopy (S/TEM). Using the L2,3 white line intensity ratio method we determine the oxidation state of Mn and Ti in a liquid electrolyte solvent and discuss experimental parameters that influence measurement sensitivity.

  12. Probing Battery Chemistry with Liquid Cell Electron Energy Loss Spectroscopy

    SciTech Connect

    Unocic, Raymond R.; Baggetto, Loic; Veith, Gabriel M.; Aguiar, Jeffery A.; Unocic, Kinga A.; Sacci, Robert L.; Dudney, Nancy J.; More, Karren L.

    2015-11-25

    We demonstrate the ability to apply electron energy loss spectroscopy (EELS) to follow the chemistry and oxidation states of LiMn2O4 and Li4Ti5O12 battery electrodes within a battery solvent. The use and importance of in situ electrochemical cells coupled with a scanning/transmission electron microscope (S/TEM) has expanded and been applied to follow changes in battery chemistry during electrochemical cycling. Furthermore, we discuss experimental parameters that influence measurement sensitivity and provide a framework to apply this important analytical method to future in situ electrochemical studies.

  13. A Scanning Probe Microscope for Surface Measurement in Nano-Scale.

    PubMed

    Yu, Huijuan; Huang, Qiangxian; Zhang, Rui; Li, Zhibo; Cheng, Zhenying

    2016-06-01

    A tapping mode scanning probe microscopy (TM SPM) system for surface measurement in nanoscale is developed, of which the main element is a scanning probe consisting of quartz tuning fork and a long sharp tungsten tip. Quartz tuning fork is a very good resonant element with piezoelectrical characteristic, and it acts as an actuator and a force sensor simultaneously in the probe. The vertical spatial resolution of the TM SPM is up to sub-nanometer (0.11 nm) and the measuring force is in micro Newton magnitude (about 30 μN). In the scanning operation, the probe vibrates at its resonant frequency, so that the amplitude or frequency (or phase) of the resonant tuning fork is very sensitive to external forces (Its quality factor in air is about 3138). Using the TM SPM constructed by this probe, silicon samples are scanned. Their topography and phase images which indicate the surface material characteristics are reconstructed effectively with a high resolution and low destructiveness. Soft materials, such as Protein structure can also be scanned theoretically without damage. In addition, because of the using of the long sharp tungsten tip, the system has the capacity of measuring micro structures with large aspect ratio, such as large micro steps, deep micro trenches, etc. PMID:27427664

  14. Development of a micro-CMM with five-axis scanning touch probe

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Chen, Hung-Chi

    2016-01-01

    The purpose of this study is to develop with low cost, high precision, low contact force micro-CMM that has fiveaxis scanning touch probe. In this study, the measurement performance of the proposed system is enhanced through the use of a rigid aluminum double-arch-bridge structure to support the five-axis scanning touch probe. Furthermore, the reliability of the scanning probe mechanism of three degrees of freedom was analyzed and validated. in addition two axis (A-axis and C-axis) was added on the scanning probe. This design can be achieved independent of measurement, and minimize the dynamic error. In terms of software, a PC-Based controller was integrates five-axis motion systems with the measurement system through a five-axis control card and a data acquisition card. It also completed the functional modules of Set, Manual and Measurement. In the measurement system, we used our own developed coordinate measurement software, with the XYZ platforms system, rotating mechanism and scanning probe to achieve complex surface measurements. The micro-CMM has a working volume the micro-CMM has a working volume of 80×80×40 mm3 , and the overall dimensions is 486 × 486 × 448 mm.

  15. Development of a scanning touch probe with 5-axis measuring functions

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Lai, Kuan-Wen; Chen, Hung-Chi

    2015-02-01

    The purpose of this study is to develop a five-axis scanning touch probe with high precision and low contact force. The development of scanning touch probe is consisted of three parts: mechanism design, optical path design, and rotation structure design. The mechanism design contains three parts, Z-axis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, and thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the work piece only leads to change in the angles of X- and Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. The rotation structure refers to the principle of 5-axis machining design, and the two rotary axes (A- and C-axis) to join the self-developed scanning probe. This design can achieve independent measurements and eliminate the dynamic measurement error that three-axis scanning systems typically have. By validation through an experiment, the three-dimensional scanning touch probe developed by this study has a measuring range of +/-1mm×+/-1mm×1mm, and unidirectional repeatability of 0.6μm.

  16. Localized Electroless Ag Plating at a Tip Apex for Scanning Kelvin Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Lin, Chun-Ting; Yu, Ming-Han; Su, James; Chen, Po-Li; Shiao, Ming-Hua; Nemcsics, Akos; Chang, Mao-Nan

    2013-06-01

    A typical probe for scanning Kelvin probe microscopy (SKPM) consists of an atomic force microscopy (AFM) probe with a metallic coating. Such probes result in a large sensing area and lead to poor spatial resolution due to the stray-field effect. With electroless Ag plating (EAP), we employed an AFM system to form a Ag nanodot (AND) at the apex of the probe tip, which reduces the sensing area of the SKPM probe, thereby suppressing the stray-field effect. It was revealed that the tip with an AND structure had improved the spatial resolution in SKPM. Our experimental results showed that the EAP process can be completed in a few seconds, implying that localized EAP is a simple and rapid process for preparing an AND structure at the tip apex in SKPM measurements.

  17. A fast spatial scanning combination emissive and mach probe for edge plasma diagnosis

    SciTech Connect

    Lehmer, R.D.; LaBombard, B.; Conn, R.W.

    1989-04-01

    A fast spatially scanning emissive and mach probe has been developed for the measurement of plasma profiles in the PISCES facility at UCLA. A pneumatic cylinder is used to drive a multiple tip probe along a 15cm stroke in less than 400msec, giving single shot profiles while limiting power deposition to the probe. A differentially pumped sliding O-ring seal allows the probe to be moved between shots to infer two and three dimensional profiles. The probe system has been used to investigate the plasma potential, density, and parallel mach number profiles of the presheath induced by a wall surface and scrape-off-layer profile modifications in biased limiter simulation experiments. Details of the hardware, data acquisition electronics, and tests of probe reliability are discussed. 30 refs., 24 figs.

  18. Probing electrode/electrolyte interfaces in situ by X-ray spectroscopies: old methods, new tricks.

    PubMed

    Wu, Cheng Hao; Weatherup, Robert S; Salmeron, Miquel B

    2015-11-11

    Electrode/electrolyte interfaces play a vital role in various electrochemical systems, but in situ characterization of such buried interfaces remains a major challenge. Several efforts to develop techniques or to modify existing techniques to study such interfaces are showing great promise to overcome this challenge. Successful examples include electrochemical scanning tunneling microscopy (EC-STM), surface-sensitive vibrational spectroscopies, environmental transmission electron microscopy (E-TEM), and surface X-ray scattering. Other techniques such as X-ray core-level spectroscopies are element-specific and chemical-state-specific, and are being widely applied in materials science research. Herein we showcase four types of newly developed strategies to probe electrode/electrolyte interfaces in situ with X-ray core-level spectroscopies. These include the standing wave approach, the meniscus approach, and two liquid cell approaches based on X-ray photoelectron spectroscopy and soft X-ray absorption spectroscopy. These examples demonstrate that with proper modifications, many ultra-high-vacuum based techniques can be adapted to study buried electrode/electrolyte interfaces and provide interface-sensitive, element- and chemical-state-specific information, such as solute distribution, hydrogen-bonding network, and molecular reorientation. At present, each method has its own specific limitations, but all of them enable in situ and operando characterization of electrode/electrolyte interfaces that can provide important insights into a variety of electrochemical systems. PMID:26514115

  19. Recovery of local density of states using scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Passoni, M.; Donati, F.; Li Bassi, A.; Casari, C. S.; Bottani, C. E.

    2009-01-01

    Scanning tunneling spectroscopy (STS) provides a unique method for the investigation of the local surface-projected electron density of states (DOS), mostly for its capability of reaching atomic resolution. Such information is contained in a nonobvious way in STS data, and a proper understanding of the overall features of the system (sample+tip) is mandatory in order to obtain quantitative information. Several approaches have been proposed in the literature to tackle this problem. A common feature of these methods is that they are mostly based on a one-dimensional (1D) WKB description of the tunneling current. We present a critical analysis and an extension of the methods so far proposed, with the main goal of applying the results to STS experimental data. This study has been conducted by modeling the tip-sample system within the frame of 1D-WKB theory, investigating key open issues, such as the estimation of required but usually experimentally unknown parameters such as the tip-sample distance and the role played by the presence of a nonconstant tip local DOS on STS data. This investigation allows us to ascertain strengths and weaknesses of the existing methods and leads to an optimized and improved strategy which we propose for the analysis of STS data. We tested our conclusions on STS measurements of the Si(111)-7×7 and Au(111) surfaces, acquired with W and Cr tips.

  20. Scanning gate transconductance microscopy and spectroscopy of a mesoscopic ring

    NASA Astrophysics Data System (ADS)

    Hackens, Benoit; Martins, Frederico; Faniel, Sebastien; Bayot, Vincent; Pala, Marco; Sellier, Hermann; Huant, Serge; Desplanque, Ludovic; Wallart, Xavier

    2011-03-01

    In scanning gate microscopy (SGM), a dc voltage is applied to a sharp tip moving in the vicinity of a device. This alters the electrostatic potential seen by electrons inside the device, and consequently changes the device conductance. Here, we superimpose a small ac voltage to the dc bias applied on the tip, and record the change of device conductance at the tip bias modulation frequency, i.e. the local transconductance. We first image the low temperature transconductance of a mesoscopic ring patterned in a two-dimensional electron system (2DES) hosted in an InGaAs/InAlAs heterostructure. The tranconductance images are decorated by concentric features that we associate with charging of electron traps located close to the 2DES. We perform spectroscopy of these traps by positioning the tip close to them, and recording the ring transconductance as a function of the tip dc voltage and the bias accross the quantum ring. We observe Coulomb diamonds in our spectroscopic data, which confirms that Coulomb blockade is at play.

  1. 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.

  2. Differentiating Ferroelectric and Nonferroelectric Electromechanical Effects with Scanning Probe Microscopy.

    PubMed

    Balke, Nina; Maksymovych, Petro; Jesse, Stephen; Herklotz, Andreas; Tselev, Alexander; Eom, Chang-Beom; Kravchenko, Ivan I; Yu, Pu; Kalinin, Sergei V

    2015-06-23

    Ferroelectricity in functional materials remains one of the most fascinating areas of modern science in the past several decades. In the last several years, the rapid development of piezoresponse force microscopy (PFM) and spectroscopy revealed the presence of electromechanical hysteresis loops and bias-induced remnant polar states in a broad variety of materials including many inorganic oxides, polymers, and biosystems. In many cases, this behavior was interpreted as the ample evidence for ferroelectric nature of the system. Here, we systematically analyze PFM responses on ferroelectric and nonferroelectric materials and demonstrate that mechanisms unrelated to ferroelectricity can induce ferroelectric-like characteristics through charge injection and electrostatic forces on the tip. We will focus on similarities and differences in various PFM measurement characteristics to provide an experimental guideline to differentiate between ferroelectric material properties and charge injection. In the end, we apply the developed measurement protocols to an unknown ferroelectric material. PMID:26035634

  3. Scanning probe measurements on a magnetic bead biosensor

    NASA Astrophysics Data System (ADS)

    Megens, Mischa; de Theije, Femke; de Boer, Bart; van Gaal, Frans

    2007-07-01

    We experimentally demonstrate the sensitivity of an integrated detection scheme for small superparamagnetic beads, intended for medical diagnostic applications. Detection is based on the giant magnetoresistance effect of a 100×3μm2 magnetic multilayer strip. A conductive wire to magnetize the superparamagnetic beads is integrated on the same substrate. By scanning a single bead over the wires and sensor strip using an atomic force microscope, we simultaneously measure topography and sensor resistivity in a three-dimensional volume above the sensor. The observations can be explained well by means of the macroscopically measured sensor resistivity curve and the magnetization of the beads, combined with the Biot-Savart law for the magnetic field of the wire. From these encouraging results, we project that it is possible to detect even a single 300nm superparamagnetic bead on our sensor.

  4. Application of Scanning Probe Microscopy to Genetic Analysis

    NASA Astrophysics Data System (ADS)

    Sugiyama, Shigeru; Yoshino, Tomoyuki; Tsukamoto, Kazumi; Sasou, Megumi; Kuwazaki, Seigo; Takahashi, Hirokazu; Suetsugu, Yoshitaka; Narukawa, Junko; Yamamoto, Kimiko; Ohtani, Toshio

    2006-03-01

    We are developing an integrated technique involving of nanometer-size dissection of chromosome fragments by atomic force microscopy (AFM) and direct detection of the location of genome library clones by scanning near-field optical/atomic force microscopy (SNOM/AFM). The locations of nucleus organizer regions (NORs) on barley chromosomes and a bacterial artificial chromosome (BAC) clone were successfully detected by SNOM/AFM. Nanometer-scale dissection of silkworm pachytene chromosomes was also performed by AFM, and we succeeded in three successive dissection events of the chromosome region approximately 250 nm apart from each other. If this type of integrated method can be established in the near future, we will easily obtain the nucleotide sequences with positional information on chromosomes, which lead to a time- and cost-saving genome analysis technique.

  5. Scanning mass spectrometry probe: a scanning probe electrospray ion source for imaging mass spectrometry of submerged interfaces and transient events in solution.

    PubMed

    Kottke, Peter A; Degertekin, F Levent; Fedorov, Andrei G

    2010-01-01

    The scanning mass spectrometry (SMS) probe is a new electrospray ion source. Motivated by the need for untargeted chemical imaging of dynamic events in solution, we have exploited an approach to electrospray ionization (ESI) that allows continuous sampling from a highly localized volume (approximately picoliters) in a liquid environment, softly ionizes molecules in the sample to render them amenable for mass spectrometric analysis, and sends the ions to the mass spectrometer. The key underlying concepts for our approach are (1) treating the electrospray capillary inlet as a chemical scanning probe and (2) locating the electrospray point as close as possible to the sampling point, thus providing the shortest response time possible. This approach enables chemical monitoring or imaging of submerged interfaces, providing access to details of spatial heterogeneity and temporal changes within liquid samples. It also permits direct access to liquid/ liquid interfaces for ESI-MS analysis. In this letter we report the first demonstrations of these capabilities of the SMS probe and describe some of the probe's basic characteristics. PMID:19904914

  6. Multi-scale Imaging of Cellular and Sub-cellular Structures using Scanning Probe Recognition Microscopy.

    NASA Astrophysics Data System (ADS)

    Chen, Q.; Rice, A. F.

    2005-03-01

    Scanning Probe Recognition Microscopy is a new scanning probe capability under development within our group to reliably return to and directly interact with a specific nanobiological feature of interest. In previous work, we have successfully recognized and classified tubular versus globular biological objects from experimental atomic force microscope images using a method based on normalized central moments [ref. 1]. In this paper we extend this work to include recognition schemes appropriate for cellular and sub-cellular structures. Globular cells containing tubular actin filaments are under investigation. Thus there are differences in external/internal shapes and scales. Continuous Wavelet Transform with a differential Gaussian mother wavelet is employed for multi- scale analysis. [ref. 1] Q. Chen, V. Ayres and L. Udpa, ``Biological Investigation Using Scanning Probe Recognition Microscopy,'' Proceedings 3rd IEEE Conference on Nanotechnology, vol. 2, p 863-865 (2003).

  7. Probing electron transport and structural properties of nanostructures on Si with a quadraprobe scanning tunneling microscope

    SciTech Connect

    Kim, Tae Hwan; Wendelken, J F; Li, An-Ping

    2008-01-01

    The electron transport and structural properties of nanostructured materials have been examined with a newly developed low temperature quadraprobe scanning tunneling microscope (STM) system. The quadraprobe STM system, as a "nano" version of a four-probe station provides an integrated research platform with a low temperature four-probe STM, a molecular-beam epitaxy growth chamber, a high resolution scanning electron microscope, and a scanning Auger microscope. The four STM probes can be driven independently with sub-nanometer precision, enabling conventional STM imaging and four-point electrical transport study of surface electronic systems and nanostructured materials at temperatures down to 10 K. Self-assembled nanostructures grown on Si by doping with metal atoms (Au, Gd, Ag) have been fabricated and characterized in situ.

  8. Resolving 2D Amorphous Materials with Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Burson, Kristen M.; Buechner, Christin; Lewandowski, Adrian; Heyde, Markus; Freund, Hans-Joachim

    Novel two-dimensional (2D) materials have garnered significant scientific interest due to their potential technological applications. Alongside the emphasis on crystalline materials, such as graphene and hexagonal BN, a new class of 2D amorphous materials must be pursued. For amorphous materials, a detailed understanding of the complex structure is necessary. Here we present a structural study of 2D bilayer silica on Ru(0001), an insulating material which is weakly coupled to the substrate. Atomic structure has been determined with a dual mode atomic force microscopy (AFM) and scanning tunneling microscopy (STM) sensor in ultra-high vacuum (UHV) at low temperatures, revealing a network of different ring sizes. Liquid AFM measurements with sub-nanometer resolution bridge the gap between clean UHV conditions and the environments that many material applications demand. Samples are grown and characterized in vacuum and subsequently transferred to the liquid AFM. Notably, the key structural features observed, namely nanoscale ring networks and larger holes to the substrate, show strong quantitative agreement between the liquid and UHV microscopy measurements. This provides direct evidence for the structural stability of these silica films for nanoelectronics and other applications. KMB acknowledges support from the Alexander von Humboldt Foundation.

  9. Nanoscale thermal imaging using a scanning spin probe

    NASA Astrophysics Data System (ADS)

    Laraoui, Abdelghani; Aycock-Rizzo, Halley; Gao, Yang; Riedo, Elisa; Meriles, Carlos

    We use a 30-nm diamond-nanocrystal-hosted nitrogen-vacancy (NV) center attached to the apex of a silicon tip as a local temperature sensor. First, we apply an electrical current to heat up the tip to a predefined operating temperature and rely on the NV to monitor the small thermal changes the tip experiences as it is brought into contact with surfaces of varying thermal conductivity. With the aid of a combined AFM/confocal setup, we image engineered microstructures with nanoscale resolution, and attain excellent agreement between the thermal conductivity and topographic maps. Given the small mass of the NV-hosting diamond nanoparticle, our technique shows a fast time response of order hundred microseconds, limited by the heat dissipation time of the tip. In a second approach, we heat nanostructured gold deposited on glass substrate by injecting a direct current. By monitoring the frequency shift of NV spin transitions upon scanning the AFM tip we reconstruct nanometer-resolved temperature maps. Our technique promises multiple applications ranging from the investigation of phonon dynamics in nanostructures to the characterization of heterogeneous phase transitions in various solid-state systems.

  10. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach.

    PubMed

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K; Kalinin, Sergei V

    2016-08-01

    Energy technologies of the 21(st) century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry. PMID:27146961

  11. Use of scanning probe microscopy to study the evolution of nanometer sized liquid structures

    NASA Astrophysics Data System (ADS)

    Aloisi, Giovanni; Bacci, Federico; Carlà, Marcello; Dolci, David

    2011-10-01

    The evolution of the profile of nanometer sized water drops on a mica surface has been studied through hydration scanning probe microscopy. A time range from a few seconds down to a fraction of millisecond after the formation of the drop has been explored. This high time resolution has been obtained by sampling a series of statistically equivalent drops. This approach also avoids any probe interference during the drop evolution process.

  12. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    DOE PAGESBeta

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-04-21

    Energy technologies of the 21st century require an understanding and precise control over ion transport and electrochemistry at all length scales – from single atoms to macroscopic devices. Our short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. In this discussion we present the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.

  13. Solid-state electrochemistry on the nanometer and atomic scales: the scanning probe microscopy approach

    NASA Astrophysics Data System (ADS)

    Strelcov, Evgheni; Yang, Sang Mo; Jesse, Stephen; Balke, Nina; Vasudevan, Rama K.; Kalinin, Sergei V.

    2016-07-01

    Energy technologies of the 21st century require an understanding and precise control over ion transport and electrochemistry at all length scales - from single atoms to macroscopic devices. This short review provides a summary of recent studies dedicated to methods of advanced scanning probe microscopy for probing electrochemical transformations in solids at the meso-, nano- and atomic scales. The discussion presents the advantages and limitations of several techniques and a wealth of examples highlighting peculiarities of nanoscale electrochemistry.

  14. 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.

  15. Investigation of the depletion layer by scanning capacitance force microscopy with Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Uruma, Takeshi; Satoh, Nobuo; Yamamoto, Hidekazu

    2016-08-01

    We have developed a scanning probe microscope (SPM) that combines atomic force microscopy (AFM) with both Kelvin probe force microscopy (KFM — to measure the surface potential) and scanning capacitance force microscopy (SCFM — to measure the differential capacitance). The surface physical characteristics of a commercial Si Schottky barrier diode (Si-SBD), with and without an applied reverse bias, were measured over the same area by our AFM/KFM/SCFM system. We thus investigated the discrete power device by calculating the depletion-layer width and drawing an energy-band diagram.

  16. Study of wear of diamond-coated probe tips when scanning on different materials

    NASA Astrophysics Data System (ADS)

    Küng, A.; Nicolet, A.; Meli, F.

    2015-08-01

    The accuracy of today’s coordinate measuring machines (CMM) has reached a level at which the exact knowledge of each component is required. The role of the probe tip is particularly crucial because it is in contact with the sample surface. Understanding how the probe tip wears off will help to narrow the measurement errors. Today, diamond-coated probes of excellent quality are becoming commercially available. In the present work, the wear of those probes was studied when scanning on different sample materials and under different measuring conditions. The wear rate was quantified in terms of the rate of the removed diamond volume per meter scan length. It cannot be simply derived from material properties or scanning conditions. A simple calculation also shows that only a very small fraction of the friction energy is devoted to the removal of atoms from the diamond crystal. The wear rate of diamond-coated probes was found to be orders of magnitude smaller compared with the wear of traditional sapphire probes.

  17. Nondestructive millimeter wave imaging and spectroscopy using dielectric focusing probes

    NASA Astrophysics Data System (ADS)

    Hejase, Jose A.; Shane, Steven S.; Park, Kyoung Y.; Chahal, Premjeet

    2014-02-01

    A tool for interrogating objects over a wide band of frequencies with subwavelength resolution at small standoff distances (near field region) in the transmission mode using a single source and detector measurement setup in the millimeter wave band is presented. The design utilizes optics like principles for guiding electromagnetic millimeter waves from large cross-sectional areas to considerably smaller sub-wavelength areas. While plano-convex lenses can be used to focus waves to a fine resolution, they usually require a large stand-off distance thus resulting in alignment and spacing issues. The design procedure and simulation analysis of the focusing probes are presented in this study along with experimental verification of performance and imaging and spectroscopy examples. Nondestructive evaluation will find benefit from such an apparatus including biological tissue imaging, electronic package integrity testing, composite dielectric structure evaluation for defects and microfluidic sensing.

  18. Nondestructive millimeter wave imaging and spectroscopy using dielectric focusing probes

    SciTech Connect

    Hejase, Jose A.; Shane, Steven S.; Park, Kyoung Y.; Chahal, Premjeet

    2014-02-18

    A tool for interrogating objects over a wide band of frequencies with subwavelength resolution at small standoff distances (near field region) in the transmission mode using a single source and detector measurement setup in the millimeter wave band is presented. The design utilizes optics like principles for guiding electromagnetic millimeter waves from large cross-sectional areas to considerably smaller sub-wavelength areas. While plano-convex lenses can be used to focus waves to a fine resolution, they usually require a large stand-off distance thus resulting in alignment and spacing issues. The design procedure and simulation analysis of the focusing probes are presented in this study along with experimental verification of performance and imaging and spectroscopy examples. Nondestructive evaluation will find benefit from such an apparatus including biological tissue imaging, electronic package integrity testing, composite dielectric structure evaluation for defects and microfluidic sensing.

  19. Determination of diffusion tensors from oscillating and circulating scanning probe tips

    NASA Astrophysics Data System (ADS)

    Hahne, Susanne; Rahe, Philipp; Maass, Philipp

    2015-06-01

    We develop two methods for determining anisotropic diffusion properties of molecules on surfaces. These methods are based on the analysis of signal fluctuations recorded with moving probe tips, of, for example, a scanning tunneling microscope. In the first method, the probe tip oscillates along a straight line, which allows to quantify the effective diffusion perpendicular to the line. By varying the line orientation, the diffusion tensor is obtained. In the second method, the probe tip rotates along a circle and the diffusion tensor is determined by analysis of cross-correlations between antipodal points. Both methods are successfully validated against surrogate data from kinetic Monte Carlo simulations.

  20. Mitochondrial respiratory complex I probed by delayed luminescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Baran, Irina; Ionescu, Diana; Privitera, Simona; Scordino, Agata; Mocanu, Maria Magdalena; Musumeci, Francesco; Grasso, Rosaria; Gulino, Marisa; Iftime, Adrian; Tofolean, Ioana Teodora; Garaiman, Alexandru; Goicea, Alexandru; Irimia, Ruxandra; Dimancea, Alexandru; Ganea, Constanta

    2013-12-01

    The role of mitochondrial complex I in ultraweak photon-induced delayed photon emission [delayed luminescence (DL)] of human leukemia Jurkat T cells was probed by using complex I targeting agents like rotenone, menadione, and quercetin. Rotenone, a complex I-specific inhibitor, dose-dependently increased the mitochondrial level of reduced nicotinamide adenine dinucleotide (NADH), decreased clonogenic survival, and induced apoptosis. A strong correlation was found between the mitochondrial levels of NADH and oxidized flavin mononucleotide (FMNox) in rotenone-, menadione- and quercetin-treated cells. Rotenone enhanced DL dose-dependently, whereas quercetin and menadione inhibited DL as well as NADH or FMNox. Collectively, the data suggest that DL of Jurkat cells originates mainly from mitochondrial complex I, which functions predominantly as a dimer and less frequently as a tetramer. In individual monomers, both pairs of pyridine nucleotide (NADH/reduced nicotinamide adenine dinucleotide phosphate) sites and flavin (FMN-a/FMN-b) sites appear to bind cooperatively their specific ligands. Enhancement of delayed red-light emission by rotenone suggests that the mean time for one-electron reduction of ubiquinone or FMN-a by the terminal Fe/S center (N2) is 20 or 284 μs, respectively. All these findings suggest that DL spectroscopy could be used as a reliable, sensitive, and robust technique to probe electron flow within complex I in situ.

  1. Apertureless scanning microscope probe as a detector of semiconductor laser emission

    SciTech Connect

    Dunaevskiy, Mikhail; Dontsov, Anton; Monakhov, Andrei; Alekseev, Prokhor; Titkov, Alexander; Baranov, Alexei; Girard, Paul; Arinero, Richard; Teissier, Roland

    2015-04-27

    An operating semiconductor laser has been studied using a scanning probe microscope. A shift of the resonance frequency of probe that is due to its heating by laser radiation has been analyzed. The observed shift is proportional to the absorbed radiation and can be used to measure the laser near field or its output power. A periodical dependence of the measured signal has been observed as a function of distance between the probe and the surface of the laser due to the interference of the outgoing and cantilever-reflected waves. Due to the multiple reflections resulting in the interference, the light absorption by the probe cantilever is greatly enhanced compared with a single pass case. Interaction of infrared emission of a diode laser with different probes has been studied.

  2. Steady-state spectroscopy of new biological probes

    NASA Astrophysics Data System (ADS)

    Abou-Zied, Osama K.

    2007-02-01

    The steady state absorption and fluorescence spectroscopy of 2-(2'-hydroxyphenyl)benzoxazole (HBO) and (2,2'-bipyridine)-3,3'-diol (BP(OH) II) were studied here free in solution and in human serum albumin (HSA) in order to test their applicability as new biological probes. HBO and BP(OH) II are known to undergo intramolecular proton transfers in the excited state. Their absorption and fluorescence spectra are sensitive to environmental change from hydrophilic to hydrophobic, thus allowing the opportunity to use them as environment-sensitive probes. The effect of water on the steady state spectra of the two molecules also shows unique features which may position them as water sensors in biological systems. For HBO in buffer, fluorescence is only due to the syn-keto tautomer, whereas in HSA the fluorescence is due to four species in equilibrium in the excited state (the syn-keto tautomer, the anti-enol tautomer, the solvated syn-enol tautomer, and the anion species of HBO). Analysis of the fluorescence spectra of HBO in HSA indicates that HBO is exposed to less water in the HBO:HSA complex. For the BP(OH) II molecule, unique absorption due to water was observed in the spectral region of 400-450 nm. This absorption decreases in the presence of HSA due to less accessibility to water as a result of binding to HSA. Fluorescence of BP(OH) II is due solely to the di-keto tautomer after double proton transfer in the excited state. The fluorescence peak of BP(OH) II shows a red-shift upon HSA recognition which is attributed to the hydrophobic environment inside the binding site of HSA. We discuss also the effect of probe-inclusion inside well-defined hydrophobic cavities of cyclodextrins.

  3. Aqueous hydrogen bonding probed with polarization and matrix isolation spectroscopy

    NASA Astrophysics Data System (ADS)

    Shultz, Mary Jane; Bisson, Patrick; Buch, Victoria; Groenzin, Henning; Li, Irene

    2010-05-01

    A major challenge in hydrogen-bond research is interpreting the vibrational spectrum of water, arguably the most fundamental hydrogen bonding system. This challenge remains despite over a half century of progress in vibrational spectroscopy, largely due to a combination of the huge oscillator strength and the enormous width of the hydrogen-bond region. Lack of assignment of the resonances in the hydrogen-bond region hinders investigation of interactions between water and solutes. This lack-of-interpretation issue is an even more significant problem for studies of the aqueous interface. Numerous solutes are known to have an effect, some very dramatic, on the shape of the surface spectrum. These effects, however, are but tantalizing teasers because lack of interpretation means that the changes cannot be used to diagnose the effect of solutes or impinging gas-phase molecules on the surface. In the reported work two techniques are used to probe the origin of vibrational resonances in the H-bonded region: the surface sensitive technique sum frequency generation (SFG) and room-temperature matrix isolation spectroscopy (RT-MIS). A polarization technique called polarization angle null (PAN) has been developed that extends SFG and enables identification of resonances. The result of applying PAN-SFG to single crystal, I h ice is identification of at least nine underlying resonances and assignment of two of these. One resonance is correlated with the crystal temperature and is a sensitive probe for interactions that disrupt long range order on the surface - it is a morphology reporter. The second is associated with weakly bonded, double-donor water molecules. This resonance is sensitive to interaction of hydrogen bond donors, i.e. acids, with the surface. Both modes are more correctly pictured as collective modes. These two assignments are the first definitive assignments in the hydrogen-bond region for the aqueous surface. The effect of salts on the vibrational spectrum of

  4. Nanoscale electrical property studies of individual GeSi quantum rings by conductive scanning probe microscopy

    PubMed Central

    2012-01-01

    The nanoscale electrical properties of individual self-assembled GeSi quantum rings (QRs) were studied by scanning probe microscopy-based techniques. The surface potential distributions of individual GeSi QRs are obtained by scanning Kelvin microscopy (SKM). Ring-shaped work function distributions are observed, presenting that the QRs' rim has a larger work function than the QRs' central hole. By combining the SKM results with those obtained by conductive atomic force microscopy and scanning capacitance microscopy, the correlations between the surface potential, conductance, and carrier density distributions are revealed, and a possible interpretation for the QRs' conductance distributions is suggested. PMID:23194252

  5. Advanced electric-field scanning probe lithography on molecular resist using active cantilever

    NASA Astrophysics Data System (ADS)

    Kaestner, Marcus; Aydogan, Cemal; Lipowicz, Hubert-Seweryn; Ivanov, Tzvetan; Lenk, Steve; Ahmad, Ahmad; Angelov, Tihomir; Reum, Alexander; Ishchuk, Valentyn; Atanasov, Ivaylo; Krivoshapkina, Yana; Hofer, Manuel; Holz, Mathias; Rangelow, Ivo W.

    2015-03-01

    The routine "on demand" fabrication of features smaller than 10 nm opens up new possibilities for the realization of many novel nanoelectronic, NEMS, optical and bio-nanotechnology-based devices. Based on the thermally actuated, piezoresistive cantilever technology we have developed a first prototype of a scanning probe lithography (SPL) platform able to image, inspect, align and pattern features down to single digit nano regime. The direct, mask-less patterning of molecular resists using active scanning probes represents a promising path circumventing the problems in today's radiation-based lithography. Here, we present examples of practical applications of the previously published electric field based, current-controlled scanning probe lithography on molecular glass resist calixarene by using the developed tabletop SPL system. We demonstrate the application of a step-and-repeat scanning probe lithography scheme including optical as well as AFM based alignment and navigation. In addition, sequential read-write cycle patterning combining positive and negative tone lithography is shown. We are presenting patterning over larger areas (80 x 80 μm) and feature the practical applicability of the lithographic processes.

  6. Cavity-Enhanced Frequency-Agile Rapid Scanning (fars) Spectroscopy: Measurement Principles

    NASA Astrophysics Data System (ADS)

    Hodges, Joseph T.; Long, David A.; Truong, Gar-Wing; Douglass, Kevin O.; Maxwell, Stephen E.; Zee, Roger Van; Plusquellic, David F.

    2013-06-01

    We present the principles of frequency-agile, rapid scanning (FARS) spectroscopy, a new technique for high-bandwidth, cavity-enhanced, laser absorption measurements. This method enables a visible or near-infrared probe laser beam to be frequency tuned over several tens of GHz using a microwave source, a waveguide phase modulator and a filter cavity. For the types of cavity-enhanced methods discussed here, the optical resonator itself is used to select a single sideband of the modulated laser spectrum, obviating the need for a separate filter cavity. FARS offers several important advantages over conventional cw laser tuning methods based on thermal or mechanical methods. These include, high speed tuning with sub-ms switching times, the ability to select arbitrary frequency steps or chirp rates, and the realization of a spectrum detuning axis with sub-kHz level precision. We discuss how FARS can be applied to cavity ring-down spectroscopy and other cavity-enhanced methods to enable rapid and accurate measurements of line parameters and to give noise-equivalent absorption coefficients at the 10^{-12} cm^{-1} Hz^{-1/2} level.

  7. Scanning elastic scattering spectroscopy detects metastatic breast cancer in sentinel lymph nodes

    NASA Astrophysics Data System (ADS)

    Austwick, Martin R.; Clark, Benjamin; Mosse, Charles A.; Johnson, Kristie; Chicken, D. Wayne; Somasundaram, Santosh K.; Calabro, Katherine W.; Zhu, Ying; Falzon, Mary; Kocjan, Gabrijela; Fearn, Tom; Bown, Stephen G.; Bigio, Irving J.; Keshtgar, Mohammed R. S.

    2010-07-01

    A novel method for rapidly detecting metastatic breast cancer within excised sentinel lymph node(s) of the axilla is presented. Elastic scattering spectroscopy (ESS) is a point-contact technique that collects broadband optical spectra sensitive to absorption and scattering within the tissue. A statistical discrimination algorithm was generated from a training set of nearly 3000 clinical spectra and used to test clinical spectra collected from an independent set of nodes. Freshly excised nodes were bivalved and mounted under a fiber-optic plate. Stepper motors raster-scanned a fiber-optic probe over the plate to interrogate the node's cut surface, creating a 20×20 grid of spectra. These spectra were analyzed to create a map of cancer risk across the node surface. Rules were developed to convert these maps to a prediction for the presence of cancer in the node. Using these analyses, a leave-one-out cross-validation to optimize discrimination parameters on 128 scanned nodes gave a sensitivity of 69% for detection of clinically relevant metastases (71% for macrometastases) and a specificity of 96%, comparable to literature results for touch imprint cytology, a standard technique for intraoperative diagnosis. ESS has the advantage of not requiring a pathologist to review the tissue sample.

  8. Combining scanning haptic microscopy and fibre optic Raman spectroscopy for tissue characterization.

    PubMed

    Candefjord, S; Murayama, Y; Nyberg, M; Hallberg, J; Ramser, K; Ljungberg, B; Bergh, A; Lindahl, O A

    2012-08-01

    The tactile resonance method (TRM) and Raman spectroscopy (RS) are promising for tissue characterization in vivo. Our goal is to combine these techniques into one instrument, to use TRM for swift scanning, and RS for increasing the diagnostic power. The aim of this study was to determine the classification accuracy, using support vector machines, for measurements on porcine tissue and also produce preliminary data on human prostate tissue. This was done by developing a new experimental set-up combining micro-scale TRM-scanning haptic microscopy (SHM)-for assessing stiffness on a micro-scale, with fibre optic RS measurements for assessing biochemical content. We compared the accuracy using SHM alone versus SHM combined with RS, for different degrees of tissue homogeneity. The cross-validation classification accuracy for healthy porcine tissue types using SHM alone was 65-81%, and when RS was added it increased to 81-87%. The accuracy for healthy and cancerous human tissue was 67-70% when only SHM was used, and increased to 72-77% for the combined measurements. This shows that the potential for swift and accurate classification of healthy and cancerous prostate tissue is high. This is promising for developing a tool for probing the surgical margins during prostate cancer surgery. PMID:22762445

  9. 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. PMID:25927249

  10. 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

  11. Development of a scanning nanopipette probe microscope for fine processing using atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Morimatsu, Daisuke; Sugimoto, Hiromitsu; Nakamura, Atsushi; Ogino, Akihisa; Nagatsu, Masaaki; Iwata, Futoshi

    2016-08-01

    We developed a novel technique for fine material processing based on a localized atmospheric-pressure plasma jet (APPJ) using a scanning probe microscope equipped with a nanopipette. Using a nanopipette — a tapered glass capillary with an aperture of sub-micrometer diameter — as a nozzle makes it possible to localize the discharge area of the APPJ for fine surface processing. The nanopipette can also be used as a probe for a scanning probe microscope operated with shear-force feedback control, which is capable of positioning the pipette edge in the vicinity of material surfaces for APPJ processing and imaging of the processed surface. Sub-micrometer holes and line patterns were successfully processed on a photoresist film. It was possible to control the size of the processed patterns by varying the applied pulse voltage and the distance between the pipette and the surface.

  12. Single-body lensed-fiber scanning probe actuated by magnetic force for optical imaging.

    PubMed

    Min, Eun Jung; Na, Jihoon; Ryu, Seon Young; Lee, Byeong Ha

    2009-06-15

    We propose a fiber-based hand-held scanning probe suitable for the sample arm of an optical imaging system including optical coherence tomography. To achieve compactness, a single-body lensed-fiber and a solenoid actuator were utilized. The focusing lens of the probe was directly formed onto the distal end of a fiber, which eliminated the need for additional optical components and optical alignment. A ferromagnetic iron bead was glued onto the middle of the fiber to enable actuation by magnetic force, which allowed easy fabrication and good practicality. The fiber piece having the built-in fiber lens was forced to oscillate in its resonant frequency. With the implemented probe, optical coherence tomography images of a human fingertip and a pearl were obtained at an imaging speed of 30 frames/s over a scanning range of 4 mm. PMID:19529740

  13. Localized spin-wave excitation by the evanescent microwave scanning probe

    SciTech Connect

    Sakran, F.; Golosovsky, M.; Davidov, D.; Monod, P.

    2006-02-15

    We report a technique for the local contactless spin-wave excitation using the evanescent microwave scanning probe. Our probe is based on a dielectric resonator with the thin slit aperture. It operates at 8.8 GHz, has a spatial resolution of 10-100 {mu}m, and may be operated in the parallel and in the perpendicular magnetic field. The measurements can be performed in contact mode or by scanning the sample at constant probe-sample separation. Using 120-150 nm thick Permalloy films on a glass substrate as test samples, we show how our technique can be used for thickness measurements of thin magnetic films and for the mapping of their magnetic properties, such as magnetization and surface anisotropy.

  14. Differentiation of surface and bulk conductivities in topological insulator via four-probe spectroscopy

    DOE PAGESBeta

    Zhang, Xiaoguang; McGuire, Michael A.; Chen, Yong P.; Li, An -Ping; Durand, Corentin; Hus, Saban M.; Ma, Chuanxu; Hu, Yang; Cao, Helin; Miotkowski, Ireneusz

    2016-03-08

    Topological insulators, with characteristic topological surface states, have emerged as a new state of matter with rich potentials for both fundamental physics and device applications. However, the experimental detection of the surface transport has been hampered by the unavoidable extrinsic conductivity associated with the bulk crystals. Here we show that a four-probe transport spectroscopy in a multi-probe scanning tunneling microscopy system can be used to differentiate conductivities from the surface states and the coexisting bulk states in topological insulators. We derive a scaling relation of measured resistance with respect to varying inter-probe spacing for two interconnected conduction channels, which allowsmore » quantitative determination of conductivities from both channels. Using this method, we demonstrate the separation of 2D and 3D conduction in topological insulators by comparing the conductance scaling of Bi2Se3, Bi2Te2Se, and Sb-doped Bi2Se3 with that of a pure 2D conductance of graphene on SiC substrate. We also report the 2D conductance enhancement due to the surface doping effect in topological insulators. This technique can be applied to reveal 2D to 3D crossover of conductance in other complex systems.« less

  15. Differentiation of surface and bulk conductivities in topological insulator via four-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Li, An-Ping; Durand, Corentin; Hus, Saban; Zhang, Xiaoguang; McGuire, Michael; Chen, Yong

    The direct measurement of the topological surface states (TSS) conductivity is often hard to achieve due to the pronounced contribution from the bulk conduction channel. Here, we show a new method to differentiate conductivities from the surface states and the coexisting bulk states in topological insulators (TI) using a four-probe transport spectroscopy in a multi-probe scanning tunneling microscopy system. In contrast to conventional models that assume two resistors in parallel to count for both the TSS and bulk conductance channels, we derive a scaling relation of measured resistance with respect to varying inter-probe spacing for two interconnected conduction channels, which allows quantitative determination of conductivities from both channels. Using this method, we demonstrate the separation of 2D and 3D conduction in TI by comparing the conductance scaling of Bi2Se3, Bi2Te2Se, and Sb-doped Bi2Se3 with that of a pure 2D conductance of graphene on SiC substrate. We also quantitatively show the effect of surface doping carriers on the 2D conductance enhancement in TI. The method offers an approach to understanding not just the topological insulators but also the 2D to 3D crossover of conductance in other complex systems. This research was conducted at the Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility.

  16. Ultra-broadband infrared pump-probe spectroscopy using synchrotron radiation and a tuneable pump

    SciTech Connect

    Carroll, Lee; Friedli, Peter; Stutz, Stefan; Sigg, Hans; Lerch, Philippe; Schneider, Joerg; Treyer, Daniel; Hunziker, Stephan

    2011-06-15

    Synchrotron infrared sources have become popular mainly because of their excellent broadband brilliance, which enables spectroscopically resolved spatial-mapping of stationary objects at the diffraction limit. In this article we focus on an often-neglected further advantage of such sources - their unique time-structure - to bring such broadband spectroscopy to the time domain, for studying dynamic phenomenon down to the 100 ps limit. We describe the ultra-broadband (12.5 to 1.1 {mu}m) Fourier transform pump-probe setup, for condensed matter transmission- and reflection-spectroscopy, installed at the X01DC infrared beam-line of the Swiss Light Source (SLS). The optical pump consists of a widely tuneable 100 ps 1 kHz laser system, covering 94% of the 16 to 1.1 {mu}m range. A thorough description of the system is given, including (i) the vector-modulator providing purely electronic tuning of the pump-probe overlap up to 1 ms with sub-ps time resolution, (ii) the 500 MHz data acquisition system interfaced with the experimental physics and industrial control system (EPICS) based SLS control system for consecutive pulse sampling, and (iii) the step-scan time-slice Fourier transform scheme for simultaneous recording of the dual-channel pumped, un-pumped, and difference spectra. The typical signal/noise ratio of a single interferogram in a 100 ps time slice is 300 (measured during one single 140 s TopUp period). This signal/noise ratio is comparable to that of existing gated Globar pump-probe Fourier transform spectroscopy, but brings up to four orders of magnitude better time resolution. To showcase the utility of broadband pump-probe spectroscopy, we investigate a Ge-on-Si material system similar to that in which optically pumped direct-gap lasing was recently reported. We show that the mid-infrared reflection-spectra can be used to determine the optically injected carrier density, while the mid- and near-infrared transmission-spectra can be used to separate the strong

  17. Differentiation of Surface and Bulk Conductivities in Topological Insulators via Four-Probe Spectroscopy.

    PubMed

    Durand, Corentin; Zhang, X-G; Hus, Saban M; Ma, Chuanxu; McGuire, Michael A; Xu, Yang; Cao, Helin; Miotkowski, Ireneusz; Chen, Yong P; Li, An-Ping

    2016-04-13

    We show a new method to differentiate conductivities from the surface states and the coexisting bulk states in topological insulators using a four-probe transport spectroscopy in a multiprobe scanning tunneling microscopy system. We derive a scaling relation of measured resistance with respect to varying interprobe spacing for two interconnected conduction channels to allow quantitative determination of conductivities from both channels. Using this method, we demonstrate the separation of 2D and 3D conduction in topological insulators by comparing the conductance scaling of Bi2Se3, Bi2Te2Se, and Sb-doped Bi2Se3 against a pure 2D conductance of graphene on SiC substrate. We also quantitatively show the effect of surface doping carriers on the 2D conductance enhancement in topological insulators. The method offers a means to understanding not just the topological insulators but also the 2D to 3D crossover of conductance in other complex systems. PMID:26954427

  18. Electromechanical response of amorphous LaAlO{sub 3} thin film probed by scanning probe microscopies

    SciTech Connect

    Borowiak, Alexis S.; Baboux, Nicolas; Albertini, David; Gautier, Brice; Vilquin, Bertrand; Saint Girons, Guillaume; Pelloquin, Sylvain

    2014-07-07

    The electromechanical response of a 3 nm thick amorphous LaAlO{sub 3} layer obtained by molecular beam epitaxy has been studied using scanning probe microscopies. Although this kind of sample is not ferroelectric due to its amorphous nature, the resulting images are identical to what is generally obtained on truly ferroelectric samples probed by piezoresponse force microscopy: domains of apparently opposite polarisation are detected, and perfect, square shaped hysteresis loops are recorded. Moreover, written patterns are stable within 72 h. We discuss in the general case the possible origins of this behaviour in terms of charge injection, ionic conduction and motion of oxygen vacancies. In the case presented in this paper, since the writing process has been conducted with applied voltages lower than the injection threshold measured by conductive atomic force Microscopy, allowing to withdraw the hypothesis of charge injection in the sample, we propose that a bistable distribution of oxygen vacancies is responsible for this contrast.

  19. Frequency-scanning marginal oscillator for ion cyclotron resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Kemper, Paul R.; Bowers, Michael T.

    1982-07-01

    A number of ion cyclotron resonance applications have arisen in the past few years which require a frequency-scanned detection system. Since the traditional marginal oscillator detector has always been a fixed-frequency detector, alternative detection techniques such as bridge circuit detectors have become widely used. In this paper we present an alternative to the bridge detector, namely, a frequency-scanning marginal oscillator. Requirements and modifications necessary to convert a marginal oscillator to frequency scanning operation are discussed in detail and the necessary circuit diagrams presented. Finally, a theoretical comparison is made between bridge circuit and marginal oscillator sensitivities.

  20. Contrast analysis of near-field scanning microscopy using a metal slit probe at millimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Nozokido, Tatsuo; Ishino, Manabu; Seto, Ryosuke; Bae, Jongsuck

    2015-09-01

    We describe an analytical method for investigating the signal contrast obtained in near-field scanning microscopy using a metal slit probe. The probe has a slit-like aperture at the open end of a rectangular or a parallel plate waveguide. In our method, the electromagnetic field around the metal slit aperture at the probe tip is calculated from Maxwell's equations in the Fourier domain in order to derive the electrical admittance of a sample system consisting of layered dielectrics as seen from the probe tip. A simple two-port electrical circuit terminated by this admittance is then established to calculate the complex reflection coefficient of the probe as a signal. The validity of the method is verified at millimeter wavelengths by a full-wave high frequency 3-D finite element modeler and also by experiment. The signal contrast when varying the short dimension of the slit aperture, the separation between the probe tip and the sample, and the sample thickness are successfully explained in terms of the variation in the product of the admittance and the characteristic impedance of the waveguide at the probe tip. In particular, the cause of the local minimum in the signal intensity when varying the separation is clarified.

  1. A scanning Hall probe microscope for high resolution magnetic imaging down to 300 mK

    NASA Astrophysics Data System (ADS)

    Khotkevych, V. V.; Milošević, M. V.; Bending, S. J.

    2008-12-01

    We present the design, construction, and performance of a low-temperature scanning Hall probe microscope with submicron lateral resolution and a large scanning range. The detachable microscope head is mounted on the cold flange of a commercial H3e-refrigerator (Oxford Instruments, Heliox VT-50) and operates between room temperature and 300 mK. It is fitted with a three-axis slip-stick nanopositioner that enables precise in situ adjustment of the probe location within a 6×6×7 mm3 space. The local magnetic induction at the sample surface is mapped with an easily changeable microfabricated Hall probe [typically GsAs/AlGaAs or AlGaAs/InGaAs/GaAs Hall sensors with integrated scanning tunnel microscopy (STM) tunneling tips] and can achieve minimum detectable fields ⩾10 mG/Hz1/2. The Hall probe is brought into very close proximity to the sample surface by sensing and controlling tunnel currents at the integrated STM tip. The instrument is capable of simultaneous tunneling and Hall signal acquisition in surface-tracking mode. We illustrate the potential of the system with images of superconducting vortices at the surface of a Nb thin film down to 372 mK, and also of labyrinth magnetic-domain patterns of an yttrium iron garnet film captured at room temperature.

  2. A scanning Hall probe microscope for high resolution magnetic imaging down to 300 mK

    SciTech Connect

    Khotkevych, V. V.; Bending, S. J.; Milosevic, M. V.

    2008-12-15

    We present the design, construction, and performance of a low-temperature scanning Hall probe microscope with submicron lateral resolution and a large scanning range. The detachable microscope head is mounted on the cold flange of a commercial {sup 3}He-refrigerator (Oxford Instruments, Heliox VT-50) and operates between room temperature and 300 mK. It is fitted with a three-axis slip-stick nanopositioner that enables precise in situ adjustment of the probe location within a 6x6x7 mm{sup 3} space. The local magnetic induction at the sample surface is mapped with an easily changeable microfabricated Hall probe [typically GsAs/AlGaAs or AlGaAs/InGaAs/GaAs Hall sensors with integrated scanning tunnel microscopy (STM) tunneling tips] and can achieve minimum detectable fields {>=}10 mG/Hz{sup 1/2}. The Hall probe is brought into very close proximity to the sample surface by sensing and controlling tunnel currents at the integrated STM tip. The instrument is capable of simultaneous tunneling and Hall signal acquisition in surface-tracking mode. We illustrate the potential of the system with images of superconducting vortices at the surface of a Nb thin film down to 372 mK, and also of labyrinth magnetic-domain patterns of an yttrium iron garnet film captured at room temperature.

  3. Development of a micro-CMM with scanning touch probe and high-precision coplanar platform

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Lu, Chin-Tu; Chen, Hung-Chi; Ke, Jhih-Sian; Chang, Chao-Ming

    2013-10-01

    This study develops a micro-CMM incorporating a scanning touch probe and a high-precision coplanar platform. The measurement performance of the proposed system was enhanced through the use of a rigid aluminum double-arch-bridge structure to support the scanning touch probe. For the working stage, a linear motor was used for long-stroke positioning and a piezoelectric actuator was then employed to fine-tune the positioning so as to achieve a requirement of highprecision. The platform has two characteristics: (i) the driving and measuring axes are designed along the same line so that Abbe error of the stage can be eliminated; (ii) the coplanar design makes the X and Y axes reach a goal of two-axis concurrent. The aforementioned two designs can reduce the error of the platform so that the micro-CMM reaches a positioning accuracy of ±0.1μm for a working volume of 80×80×40 mm3. Furthermore, the reliability of the probe mechanism of three degrees of freedom was analyzed and validated. The sensor coordinates a laser diode with Position Sensor Detectors (PSD) working with an optical path to measure placement of Z-axis and angle placement of XY-axis. By validation through an experiment, the three dimensional scanning touch probe developed by this study has a measuring range of ±1mm × ±1mm × 1mm with a unidirectional repeatability of 0.6μm.

  4. Green's function modeling of response of two-dimensional materials to point probes for scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Tewary, V. K.; Quardokus, Rebecca C.; DelRio, Frank W.

    2016-04-01

    A Green's function (GF) method is developed for interpreting scanning probe microscopy (SPM) measurements on new two-dimensional (2D) materials. GFs for the Laplace/Poisson equations are calculated by using a virtual source method for two separate cases of a finite material containing a rectangular defect and a hexagonal defect. The prescribed boundary values are reproduced almost exactly by the calculated GFs. It is suggested that the GF is not just a mathematical artefact but a basic physical characteristic of material systems, which can be measured directly by SPM for 2D solids. This should make SPM an even more powerful technique for characterization of 2D materials.

  5. Bases for time-resolved probing of transient carrier dynamics by optical pump-probe scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Yokota, Munenori; Yoshida, Shoji; Mera, Yutaka; Takeuchi, Osamu; Oigawa, Haruhiro; Shigekawa, Hidemi

    2013-09-01

    The tangled mechanism that produces optical pump-probe scanning tunneling microscopy spectra from semiconductors was analyzed by comparing model simulation data with experimental data. The nonlinearities reflected in the spectra, namely, the excitations generated by paired laser pulses with a delay time, the logarithmic relationship between carrier density and surface photovoltage (SPV), and the effect of the change in tunneling barrier height depending on SPV, were examined along with the delay-time-dependent integration process used in measurement. The optimum conditions required to realize reliable measurement, as well as the validity of the microscopy technique, were demonstrated for the first time.

  6. Batch-fabrication of cantilevered magnets on attonewton-sensitivity mechanical oscillators for scanned-probe nanoscale magnetic resonance imaging

    PubMed Central

    Hickman, Steven A.; Moore, Eric W.; Lee, SangGap; Longenecker, Jonilyn G.; Wright, Sarah J.; Harrell, Lee E.; Marohn, John A.

    2015-01-01

    We have batch-fabricated cantilevers with ~100 nm diameter nickel nanorod tips and force sensitivities of a few attonewtons at 4.2 kelvin. The magnetic nanorods were engineered to overhang the leading edge of the cantilever and, consequently, the cantilevers experience what we believe is the lowest surface noise ever achieved in a scanned probe experiment. Cantilever magnetometry indicated that the tips were well magnetized, with a ≤ 20 nm dead layer; the composition of the dead layer was studied by electron microscopy and electron energy loss spectroscopy. In what we believe is the first demonstration of scanned probe detection of electron-spin resonance from a batch fabricated tip, the cantilevers were used to observe electron-spin resonance from nitroxide spin labels in a film via force-gradient-induced shifts in cantilever resonance frequency. The magnetic field dependence of the magnetic resonance signal suggests a non-uniform tip magnetization at an applied field near 0.6 T. PMID:21082863

  7. Inference of protein diffusion probed via fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Tsekouras, Konstantinos

    2015-03-01

    Fluctuations are an inherent part of single molecule or few particle biophysical data sets. Traditionally, ``noise'' fluctuations have been viewed as a nuisance, to be eliminated or minimized. Here we look on how statistical inference methods - that take explicit advantage of fluctuations - have allowed us to draw an unexpected picture of single molecule diffusional dynamics. Our focus is on the diffusion of proteins probed using fluorescence correlation spectroscopy (FCS). First, we discuss how - in collaboration with the Bustamante and Marqusee labs at UC Berkeley - we determined using FCS data that individual enzymes are perturbed by self-generated catalytic heat (Riedel et al, Nature, 2014). Using the tools of inference, we found how distributions of enzyme diffusion coefficients shift in the presence of substrate revealing that enzymes performing highly exothermic reactions dissipate heat by transiently accelerating their center of mass following a catalytic reaction. Next, when molecules diffuse in the cell nucleus they often appear to diffuse anomalously. We analyze FCS data - in collaboration with Rich Day at the IU Med School - to propose a simple model for transcription factor binding-unbinding in the nucleus to show that it may give rise to apparent anomalous diffusion. Here inference methods extract entire binding affinity distributions for the diffusing transcription factors, allowing us to precisely characterize their interactions with different components of the nuclear environment. From this analysis, we draw key mechanistic insight that goes beyond what is possible by simply fitting data to ``anomalous diffusion'' models.

  8. Probing Spin Excitations Using Magneto-Raman Spectroscopy

    NASA Astrophysics Data System (ADS)

    Thirunavukkuarasu, K.; Lu, Z.; Simpson, J.; Walker, A.; Sears, J.; Kim, Y.-J.; Burch, K.; Smirnov, D.

    The presence of a 2D quantum spin liquid state was recently suggested for the spin-orbit coupled Mott insulator α-RuCl3 with a honeycomb lattice.[Phys. Rev. 90, 041112 (2014)] Optical spectroscopy, Raman scattering, specific heat as well as magnetic susceptibility measurements on α-RuCl3 identified elementary excitations due to electronic correlations and spin-orbit coupling.[arXiv:1503.07593, Phys. Rev. Letters 114, 147201 (2015), and Phys. Rev. 91, 144420 (2015)] These observations appear to be consistent with theoretical expectations for Heisenberg-Kitaev model for QSL.[Phys. Rev. 91, 241110 (2015)] The underlying mechanism for the unconventional magnetism in α-RuCl3 was further investigated by probing the effect of external magnetic field on the Raman spectroscopic signatures. Raman scattering experiments were performed at temperatures down to 5 K and magnetic fields up to 10 T. The intensity of strongest A1g phonon was found to decrease with increasing magnetic field strength suggesting the presence of strong magnetic interactions. The experimental observations and its implications will be presented. Current Affiliation: Florida A and M University.

  9. PHEBUS: Probing of Hermean Exosphere By Ultraviolet Spectroscopy

    NASA Astrophysics Data System (ADS)

    Wedlund, M.; Chassefière, E.; Maria, J.-L.; Rouanet, N.; Quémerais, E.; Leblanc, F.

    2008-09-01

    Abstract The double spectrometer PHEBUS covers the range of Extreme Ultraviolet (55-155 nm) and Far Ultraviolet (145-315 nm) [1]. Focusing on the characterisation, composition, dynamics and surface-exosphere coupling of Mercury, PHEBUS addresses the following main scientific objectives: determination of the composition and the vertical structure of the exosphere, characterization of the exospheric dynamics: day to night circulation, active to inactive regional transport, study of surface release processes, identification and characterization of the sources of exospheric constituents, detection and characterization of the ionosphere and its relation with the neutral atmosphere, space and time monitoring of exosphere/magnetosphere exchange and transport processes, study and quantification of escape, global scale source/sink balance and geochemical cycles synergistically with other experiments of BepiColombo (MSASI, MPPE on MMO and MIXS, SERENA on MPO). Instrumentation PHEBUS consists of two gratings and two detectors which are fitted within a very compact design. The spectrum detection is based on the photon counting method using Micro Channel Plate (MCP) detectors with Resistive Anode Encoder (RAE) with photocathode's coated with CsI for the EUV range and CsTe for the FUV range. Extra visible lines (K and Ca) are monitored using a Photomultiplier (PM) that is also used in photon counting mode. In order to prevent sensitivity losses which are critical in UV ranges, a minimum of reflections is achieved inside the instrument using only an off-axis parabola and a set of holographic gratings. A one degree-offreedom scanning system allows probing at the highest possible signal to noise ratio in the selected regions and altitude ranges of interest. Different modes of observation will be used sequentially (vertical scans, along-orbit scans, grazing observations at twilight…). During the mission, the instrument will be regularly calibrated on well chosen stars to

  10. Scanning electron microscopy and electron probe X-ray microanalysis (SEM-EPMA) of pink teeth

    SciTech Connect

    Ikeda, N.; Watanabe, G.; Harada, A.; Suzuki, T.

    1988-11-01

    Samples of postmortem pink teeth were investigated by scanning electron microscopy and electron probe X-ray microanalysis. Fracture surfaces of the dentin in pink teeth were noticeably rough and revealed many more smaller dentinal tubules than those of the control white teeth. Electron probe X-ray microanalysis showed that the pink teeth contained iron which seemed to be derived from blood hemoglobin. The present study confirms that under the same circumstance red coloration of teeth may occur more easily in the teeth in which the dentin is less compact and contains more dentinal tubules.

  11. Characterization of microfabricated probes for combined atomic force and high-resolution scanning electrochemical microscopy.

    PubMed

    Gullo, Maurizio R; Frederix, Patrick L T M; Akiyama, Terunobu; Engel, Andreas; deRooij, Nico F; Staufer, Urs

    2006-08-01

    A combined atomic force and scanning electrochemical microscope probe is presented. The probe is electrically insulated except at the very apex of the tip, which has a radius of curvature in the range of 10-15 nm. Steady-state cyclic voltammetry measurements for the reduction of Ru(NH3)6Cl3 and feedback experiments showed a distinct and reproducible response of the electrode. These experimental results agreed with finite element simulations for the corresponding diffusion process. Sequentially topographical and electrochemical studies of Pt lines deposited onto Si3N4 and spaced 100 nm apart (edge to edge) showed a lateral electrochemical resolution of 10 nm. PMID:16878880

  12. Local electrochemical functionality in energy storage materials and devices by scanning probe microscopies: status and perspectives.

    PubMed

    Kalinin, Sergei V; Balke, Nina

    2010-09-15

    Energy storage and conversion systems are an integral component of emerging green technologies, including mobile electronic devices, automotive, and storage components of solar and wind energy economics. Despite the rapidly expanding manufacturing capabilities and wealth of phenomenological information on the macroscopic device behaviors, the microscopic mechanisms underpinning battery and fuel cell operations in the nanometer-micrometer range are virtually unknown. This lack of information is due to the dearth of experimental techniques capable of addressing elementary mechanisms involved in battery operation, including electronic and ion transport, vacancy injection, and interfacial reactions, on the nanometer scale. In this article, a brief overview of scanning probe microscopy (SPM) methods addressing nanoscale electrochemical functionalities is provided and compared with macroscopic electrochemical methods. Future applications of emergent SPM methods, including near field optical, electromechanical, microwave, and thermal probes and combined SPM-(S)TEM (scanning transmission electron microscopy) methods in energy storage and conversion materials are discussed. PMID:20730814

  13. Practical aspects of single-pass scan Kelvin probe force microscopy.

    PubMed

    Li, Guangyong; Mao, Bin; Lan, Fei; Liu, Liming

    2012-11-01

    The single-pass scan Kelvin probe force microscopy (KPFM) in ambient condition has a few advantages over the dual-pass lift-up scan KPFM. For example, its spatial resolution is expected to be higher; and its topographical errors caused by electrostatic forces are minimized because electrostatic forces are actively suppressed during the simultaneous topographical and KPFM measurement. Because single-pass scan KPFM in ambient condition is relatively new, it received little attention in the literature so far. In this article, we discuss several major practical aspects of single-pass scan KPFM especially in ambient condition. First, we define the resolution using a point spread function. With this definition, we analyze the relation between the resolution and the scanning parameters such as tip apex radius and tip-surface distance. We further study the accuracy of KPFM based on the point spread function. Then, we analyze the sensitivity of KPFM under different operation modes. Finally, we investigate the crosstalk between the topographical image and the surface potential image and demonstrate the practical ways to minimize the crosstalk. These discussions not only help us to understand the single-pass scan KPFM but also provide practical guidance in using single-pass scan KPFM. PMID:23206065

  14. Practical aspects of single-pass scan Kelvin probe force microscopy

    NASA Astrophysics Data System (ADS)

    Li, Guangyong; Mao, Bin; Lan, Fei; Liu, Liming

    2012-11-01

    The single-pass scan Kelvin probe force microscopy (KPFM) in ambient condition has a few advantages over the dual-pass lift-up scan KPFM. For example, its spatial resolution is expected to be higher; and its topographical errors caused by electrostatic forces are minimized because electrostatic forces are actively suppressed during the simultaneous topographical and KPFM measurement. Because single-pass scan KPFM in ambient condition is relatively new, it received little attention in the literature so far. In this article, we discuss several major practical aspects of single-pass scan KPFM especially in ambient condition. First, we define the resolution using a point spread function. With this definition, we analyze the relation between the resolution and the scanning parameters such as tip apex radius and tip-surface distance. We further study the accuracy of KPFM based on the point spread function. Then, we analyze the sensitivity of KPFM under different operation modes. Finally, we investigate the crosstalk between the topographical image and the surface potential image and demonstrate the practical ways to minimize the crosstalk. These discussions not only help us to understand the single-pass scan KPFM but also provide practical guidance in using single-pass scan KPFM.

  15. Determining the state of non-volatile memory cells with floating gate using scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Hanzii, D.; Kelm, E.; Luapunov, N.; Milovanov, R.; Molodcova, G.; Yanul, M.; Zubov, D.

    2013-01-01

    During a failure analysis of integrated circuits, containing non-volatile memory, it is often necessary to determine its contents while Standard memory reading procedures are not applicable. This article considers how the state of NVM cells with floating gate can be determined using scanning probe microscopy. Samples preparation and measuring procedure are described with the example of Microchip microcontrollers with the EPROM memory (PIC12C508) and flash-EEPROM memory (PIC16F876A).

  16. Single-molecule protein arrays enabled by scanning probe block copolymer lithography.

    PubMed

    Chai, Jinan; Wong, Lu Shin; Giam, Louise; Mirkin, Chad A

    2011-12-01

    The ability to control the placement of individual protein molecules on surfaces could enable advances in a wide range of areas, from the development of nanoscale biomolecular devices to fundamental studies in cell biology. Such control, however, remains a challenge in nanobiotechnology due to the limitations of current lithographic techniques. Herein we report an approach that combines scanning probe block copolymer lithography with site-selective immobilization strategies to create arrays of proteins down to the single-molecule level with arbitrary pattern control. Scanning probe block copolymer lithography was used to synthesize individual sub-10-nm single crystal gold nanoparticles that can act as scaffolds for the adsorption of functionalized alkylthiol monolayers, which facilitate the immobilization of specific proteins. The number of protein molecules that adsorb onto the nanoparticles is dependent upon particle size; when the particle size approaches the dimensions of a protein molecule, each particle can support a single protein. This was demonstrated with both gold nanoparticle and quantum dot labeling coupled with transmission electron microscopy imaging experiments. The immobilized proteins remain bioactive, as evidenced by enzymatic assays and antigen-antibody binding experiments. Importantly, this approach to generate single-biomolecule arrays is, in principle, applicable to many parallelized cantilever and cantilever-free scanning probe molecular printing methods. PMID:22106270

  17. Nanocarbon-scanning probe microscopy synergy: fundamental aspects to nanoscale devices.

    PubMed

    Kurra, Narendra; Reifenberger, Ronald G; Kulkarni, Giridhar U

    2014-05-14

    Scanning probe techniques scanning tunneling microscopy (STM) and atomic force microscopy (AFM) have emerged as unique local probes for imaging, manipulation, and modification of surfaces at the nanoscale. Exercising the fabrication of atomic and nansocale devices with desired properties have demanded rapid development of scanning probe based nanolithographies. Dip pen nanolithography (DPN) and local anodic oxidation (LAO) have been widely employed for fabricating functional patterns and prototype devices at nanoscale. This review discusses the progress in AFM bias lithography with focus on nanocarbon species on which many functional quantum device structures have been realized using local electrochemical and electrostatic processes. As water meniscus is central to AFM bias lithography, the meniscus formation, estimation and visualization is discussed briefly. A number of graphene-based nanodevices have been realized on the basis AFM bias lithography in the form of nanoribbons, nanorings and quantum dots with sufficiently small dimensions to show quantum phenomena such as conductance fluctuations. Several studies involving graphitic surfaces and carbon nanotubes are also covered. AFM based scratching technique is another promising approach for the fabrication of nanogap electrodes, important in molecular electronics. PMID:24697666

  18. Reciprocity theory of apertureless scanning near-field optical microscopy with point-dipole probes.

    PubMed

    Esslinger, Moritz; Vogelgesang, Ralf

    2012-09-25

    Near-field microscopy offers the opportunity to reveal optical contrast at deep subwavelength scales. In scanning near-field optical microscopy (SNOM), the diffraction limit is overcome by a nanoscopic probe in close proximity to the sample. The interaction of the probe with the sample fields necessarily perturbs the bare sample response, and a critical issue is the interpretation of recorded signals. For a few specific SNOM configurations, individual descriptions have been modeled, but a general and intuitive framework is still lacking. Here, we give an exact formulation of the measurable signals in SNOM which is easily applicable to experimental configurations. Our results are in close analogy with the description Tersoff and Hamann have derived for the tunneling currents in scanning tunneling microscopy. For point-like scattering probe tips, such as used in apertureless SNOM, the theory simplifies dramatically to a single scalar relation. We find that the measured signal is directly proportional to the field of the coupled tip-sample system at the position of the tip. For weakly interacting probes, the model thus verifies the empirical findings that the recorded signal is proportional to the unperturbed field of the bare sample. In the more general case, it provides guidance to an intuitive and faithful interpretation of recorded images, facilitating the characterization of tip-related distortions and the evaluation of novel SNOM configurations, both for aperture-based and apertureless SNOM. PMID:22897563

  19. The probe profile and lateral resolution of scanning transmission electron microscopy of thick specimens.

    PubMed

    Demers, Hendrix; Ramachandra, Ranjan; Drouin, Dominique; de Jonge, Niels

    2012-06-01

    Lateral profiles of the electron probe of scanning transmission electron microscopy (STEM) were simulated at different vertical positions in a micrometers-thick carbon sample. The simulations were carried out using the Monte Carlo method in CASINO software. A model was developed to fit the probe profiles. The model consisted of the sum of a Gaussian function describing the central peak of the profile and two exponential decay functions describing the tail of the profile. Calculations were performed to investigate the fraction of unscattered electrons as a function of the vertical position of the probe in the sample. Line scans were also simulated over gold nanoparticles at the bottom of a carbon film to calculate the achievable resolution as a function of the sample thickness and the number of electrons. The resolution was shown to be noise limited for film thicknesses less than 1 μm. Probe broadening limited the resolution for thicker films. The validity of the simulation method was verified by comparing simulated data with experimental data. The simulation method can be used as quantitative method to predict STEM performance or to interpret STEM images of thick specimens. PMID:22564444

  20. Development of a three dimensional scanning touch probe with high precision and low contact force

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Liang; Ke, Jhih-Sian; Chen, Hung-Chi

    2013-01-01

    This study aims to develop a three dimensional scanning touch probe with high precision and low contact force. The overall design has two parts, mechanism design and optical path design. The mechanism design contains three parts, Zaxis system, XY-axis system, and probe mechanism. The Z-axis system applies the characteristic of the thin sheet spring to move vertically. In the design of XY-axis system, a micro-beam is employed, through which length, width, thickness of the micro-beam and corresponding dimensions of the leaf spring are designed according to the selected contact force. The freedom degree is limited to three. And the center of the mechanism is equipped with a stylus to inhibit displacement of the Z-axis. The contact between the probe and the workpiece only leads to change in the angles of Xand Y-axes, achieving the feature of 2-degree freedom. To enable rapid change for the probes, this study designs a probe mechanism, reliability of which is analyzed and validated with ANSYS software, so that the design of 3-degree freedom mechanism is completed. The sensor has a laser diode to coordinate with Position Sensor Detector (PSD) which works with the optical path designed to measure placement of Z-axis and angle placement of XY-axis. By validation through an experiment, the three dimensional scanning touch probe developed by this study has a measuring range of +/-1mm×+/-1mm×1mm, and unidirectional repeatability of 0.6um.

  1. Investigation of the contrast inversion effect on hydrophilic surfaces using Pt/C whisker probes in a scanning force microscope

    NASA Astrophysics Data System (ADS)

    Zhukov, M. V.; Mukhin, I. S.; Levichev, V. V.; Golubok, A. O.

    2015-02-01

    We compare the spatial resolution and image contrast of an erythrocyte surface obtained by means of scanning force microscopy (SFM) with conventional hydrophobic Si probes and probes modified by hydrophilic Pt/C whisker probes. It is shown that probes with Pt/C nanowhiskers provide a higher spatial resolution and contrast when imaging relief on the surface of erythrocytes. The contrast inversion is revealed in some areas of the SFM images when replacing Si probes by probes with Pt/C nanowhiskers. The origin of this inversion in the tapping and contact modes is discussed.

  2. 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.

  3. MEMS-based non-rotatory circumferential scanning optical probe for endoscopic optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Xu, Yingshun; Singh, Janak; Siang, Teo Hui; Ramakrishna, Kotlanka; Premchandran, C. S.; Sheng, Chen Wei; Kuan, Chuah Tong; Chen, Nanguang; Olivo, Malini C.; Sheppard, Colin J. R.

    2007-07-01

    In this paper, we present a non-rotatory circumferential scanning optical probe integrated with a MEMS scanner for in vivo endoscopic optical coherence tomography (OCT). OCT is an emerging optical imaging technique that allows high resolution cross-sectional imaging of tissue microstructure. To extend its usage to endoscopic applications, a miniaturized optical probe based on Microelectromechanical Systems (MEMS) fabrication techniques is currently desired. A 3D electrothermally actuated micromirror realized using micromachining single crystal silicon (SCS) process highlights its very large angular deflection, about 45 degree, with low driving voltage for safety consideration. The micromirror is integrated with a GRIN lens into a waterproof package which is compatible with requirements for minimally invasive endoscopic procedures. To implement circumferential scanning substantially for diagnosis on certain pathological conditions, such as Barret's esophagus, the micromirror is mounted on 90 degree to optical axis of GRIN lens. 4 Bimorph actuators that are connected to the mirror on one end via supporting beams and springs are selected in this micromirror design. When actuators of the micromirror are driven by 4 channels of sinusoidal waveforms with 90 degree phase differences, beam focused by a GRIN is redirected out of the endoscope by 45 degree tilting mirror plate and achieve circumferential scanning pattern. This novel driving method making full use of very large angular deflection capability of our micromirror is totally different from previously developed or developing micromotor-like rotatory MEMS device for circumferential scanning.

  4. Molecular-Level Insights into Photocatalysis from Scanning Probe Microscopy Studies on TiO2(110)

    SciTech Connect

    Henderson, Michael A.; Lyubinetsky, Igor

    2013-06-12

    The field of heterogeneous photocatalysis has grown considerably in the decades since Fujishima and Honda's ground-breaking publications of photoelectrochemistry on TiO2. Numerous review articles continue to point to both progress made in the use of heterogeneous materials (such as TiO2) to perform photoconversion processes, and the many opportunities and challenges in heterogeneous photocatalysis research such as solar energy conversion and environmental remediation. The past decade has also seen an increase in the use of molecular-level approaches applied to model single crystal surfaces in an effort to obtain new insights into photocatalytic phenomena. In particular, scanning probe techniques (SPM) have enabled researchers to take a ‘nanoscale’ approach to photocatalysis that includes interrogation of the reactivities of specific sites and adsorbates on a model photocatalyst surface. The rutile TiO2(110) surface has become the prototypical oxide single crystal surface for fundamental studies of many interfacial phenomena. In particular, TiO2(110) has become an excellent model surface for probing photochemical and photocatalytic reactions at the molecular level. A variety of experimental approaches have emerged as being ideally suited for studying photochemical reactions on TiO2(110), including desorption-oriented approaches and electronic spectroscopies, but perhaps the most promising techniques for evaluating site-specific properties are those of SPM. In this review, we highlight the growing use of SPM techniques in providing molecular-level insights into surface photochemistry on the model photocatalyst surface of rutile TiO2(110). Our objective is to both illustrate the unique knowledge that scanning probe techniques have already provided the field of photocatalysis, and also to motivate a new generation of effort into the use of such approaches to obtain new insights into the molecular level details of photochemical events occurring at interfaces

  5. Critical current density measurement of striated multifilament-coated conductors using a scanning Hall probe microscope

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Fen; Kochat, Mehdi; Majkic, Goran; Selvamanickam, Venkat

    2016-08-01

    In this paper the authors succeeded in measuring the critical current density ({J}{{c}}) of multifilament-coated conductors (CCs) with thin filaments as low as 0.25 mm using the scanning hall probe microscope (SHPM) technique. A new iterative method of data analysis is developed to make the calculation of {J}{{c}} for thin filaments possible, even without a very small scan distance. The authors also discussed in detail the advantage and limitation of the iterative method using both simulation and experiment results. The results of the new method correspond well with the traditional fast Fourier transform method where this is still applicable. However, the new method is applicable for the filamentized CCs in much wider measurement conditions such as with thin filament and a large scan distance, thus overcoming the barrier for application of the SHPM technique on {J}{{c}} measurement of long filamentized CCs with narrow filaments.

  6. Excited-State Vibrational Coherence in Perylene Bisimide Probed by Femtosecond Broadband Pump-Probe Spectroscopy.

    PubMed

    Son, Minjung; Park, Kyu Hyung; Yoon, Min-Chul; Kim, Pyosang; Kim, Dongho

    2015-06-18

    Broadband laser pulses with ultrashort duration are capable of triggering impulsive excitation of the superposition of vibrational eigenstates, giving rise to quantum beating signals originating from coherent wave packet motions along the potential energy surface. In this work, coherent vibrational wave packet dynamics of an N,N'-bis(2,6-dimethylphenyl)perylene bisimide (DMP-PBI) were investigated by femtosecond broadband pump-probe spectroscopy which features fast and balanced data acquisition with a wide spectral coverage of >200 nm. Clear modulations were observed in the envelope of the stimulated emission decay profiles of DMP-PBI with the oscillation frequencies of 140 and 275 cm(-1). Fast Fourier transform analysis of each oscillatory mode revealed characteristic phase jumps near the maxima of the steady-state fluorescence, indicating that the observed vibrational coherence originates from an excited-state wave packet motion. Quantum calculations of the normal modes at the low-frequency region suggest that low-frequency C-C (C═C) stretching motions accompanied by deformation of the dimethylphenyl substituents are responsible for the manifestation of such coherent wave packet dynamics. PMID:25992707

  7. Nematicity in FeSe single crystals probed by pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Luo, C. W.; Cheng, P. C.; Wu, K. H.; Juang, J. Y.; Wang, S.-H.; Chiang, J.-C.; Lin, J.-Y.; Chareev, D. A.; Volkova, O. S.; Vasiliev, A. N.

    The anisotropic quasiparticle dynamics in FeSe single crystals have been studied by polarized pump-probe spectroscopy. Two distinguishable relaxation components were unambiguously observed in transient reflectivity changes (ΔR / R) . The orientation-dependent fast component with the timescale of 0.1-1.5 ps associated with the electronic structure clearly shows two-fold symmetry, which further reveals the gap opening along ky below the temperature of structure phase transition (Ts) and the electronic nematicity can persist up to 200 K. For the slow component with the timescale of 8-25 ps, it is assigned to the energy relaxation through spin sub-system and also shows a two-fold symmetry below Ts. However, this two-fold symmetry is dramatically weakened above Ts and surprisingly persists up to at least 200 K. Consequently, the high-temperature nematic fluctuations in FeSe may be driven by the order parameters which associated with both charge (orbital) and spin sub-systems. This project is financially sponsored by the MOST, Taiwan, (Grants No. 103-2923-M-009-001-MY3) and the MOE-ATU plan at NCTU.

  8. A versatile and reconfigurable setup for all-terahertz time-resolved pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Elezzabi, A. Y.; Maraghechi, P.

    2012-05-01

    A versatile optical setup for all-terahertz (THz) time resolved pump-probe spectroscopy was designed and tested. By utilizing a dual THz pulse generator emitter module, independent and synchronized THz radiation pump and probe pulses were produced, thus eliminating the need for THz beam splitters and the limitations associated with their implementation. The current THz setup allows for precise control of the electric fields splitting ratio between the THz radiation pump and probe pulses, as well as in-phase, out-of-phase, and polarization dependent pump-probe spectroscopy. Since the present THz pump-probe setup does not require specialized THz radiation optical components, such as phase shifters, polarization rotators, or wide bandwidth beam splitters, it can be easily implemented with minimal alterations to a conventional THz time domain spectroscopy system. The present setup is valuable for studying the time dynamics of THz coherent phenomena in solid-state, chemical, and biological systems.

  9. Quantitative scanning thermal microscopy based on determination of thermal probe dynamic resistance.

    PubMed

    Bodzenta, J; Juszczyk, J; Chirtoc, M

    2013-09-01

    Resistive thermal probes used in scanning thermal microscopy provide high spatial resolution of measurement accompanied with high sensitivity to temperature changes. At the same time their sensitivity to variations of thermal conductivity of a sample is relatively low. In typical dc operation mode the static resistance of the thermal probe is measured. It is shown both analytically and experimentally that the sensitivity of measurement can be improved by a factor of three by measuring the dynamic resistance of a dc biased probe superimposed with small ac current. The dynamic resistance can be treated as a complex value. Its amplitude represents the slope of the static voltage-current U-I characteristic for a given I while its phase describes the delay between the measured ac voltage and applied ac current component in the probe. The phase signal also reveals dependence on the sample thermal conductivity. Signal changes are relatively small but very repeatable. In contrast, the difference between dynamic and static resistance has higher sensitivity (the same maximum value as that of the 2nd and 3rd harmonics), and also much higher amplitude than higher harmonics. The proposed dc + ac excitation scheme combines the benefits of dc excitation (mechanical stability of probe-sample contact, average temperature control) with those of ac excitation (base-line stability, rejection of ambient temperature influence, high sensitivity, lock-in signal processing), when the experimental conditions prohibit large ac excitation. PMID:24089831

  10. Exciton dynamics in pentacene and tetracene studied using optical pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Thorsmølle, V. K.; Averitt, R. D.; Demsar, J.; Chi, X.; Smith, D. L.; Ramirez, A. P.; Taylor, A. J.

    We present room temperature photoinduced reflection and transmission measurements in pentacene and tetracene single crystals using optical pump-probe spectroscopy. Singlet exciton recombination, singlet-triplet fission, excited singlet, and triplet state absorption is observed.

  11. Exciton dynamics in pentacene and tetracene studied using optical pump-probe spectroscopy

    SciTech Connect

    Thorsmølle, V. K.; Averitt, R. D.; Demsar, J.; Chi, X.; Smith, D. L.; Ramirez, A. P.; Taylor, Antoinette J.,

    2004-01-01

    We present room temperature photoinduced reflection and transmission measurements in pentacene and tetracene single crystals using optical pump-probe spectroscopy. Singlet exciton recombination, singlet-triplet fission, excited singlet, and triplet state absorption is observed.

  12. Rubidium pump-probe spectroscopy: Comparison between ab initio theory and experiment

    SciTech Connect

    Himsworth, M.; Freegarde, T.

    2010-02-15

    We present a simple, analytic model for pump-probe spectroscopy in dilute atomic gases. Our model treats multilevel atoms, takes several broadening mechanisms into account and, with no free parameters, shows excellent agreement with experimentally observed spectra.

  13. Probing Nitrosyl Ligation of Surface-Confined Metalloporphyrins by Inelastic Electron Tunneling Spectroscopy

    PubMed Central

    2013-01-01

    Complexes obtained by the ligation of nitric oxide (NO) to metalloporphyrins represent important model systems with biological relevance. Herein we report a molecular-level investigation of surface-confined cobalt tetraphenyl porphyrin (Co-TPP) species and their interaction with NO under ultrahigh vacuum conditions. It is demonstrated that individual NO adducts can be desorbed using the atomically sharp tip of a scanning tunneling microscope, whereby a writing process is implemented for fully saturated regular metalloporphyrin arrays. The low-energy vibrational characteristics of individual Co-TPP-nitrosyl complexes probed by inelastic electron tunneling spectroscopy (IETS) reveal a prominent signature at an energy of ≃31 meV. Using density functional theory-based IETS simulations—the first to be performed on such an extensive interfacial nanosystem—we succeed to reproduce the low-frequency spectrum for the NO-ligated complex and explain the absence of IETS activity for bare Co-TPP. Moreover, we can conclusively assign the IETS peak of NO-Co-TPP to a unique vibration mode involving the NO complexation site, namely, the in-plane Co–N–O rocking mode. In addition, we verify that the propensity rules previously designed on small aromatic systems and molecular fragments hold true for a metal–organic entity. This work notably permits one to envisage IETS spectroscopy as a sensitive tool to chemically characterize hybrid interfaces formed by complex metal–organic units and gaseous adducts. PMID:23718257

  14. Scanning angle Raman spectroscopy: Investigation of Raman scatter enhancement techniques for chemical analysis

    SciTech Connect

    Meyer, Matthew W.

    2013-01-01

    This thesis outlines advancements in Raman scatter enhancement techniques by applying evanescent fields, standing-waves (waveguides) and surface enhancements to increase the generated mean square electric field, which is directly related to the intensity of Raman scattering. These techniques are accomplished by employing scanning angle Raman spectroscopy and surface enhanced Raman spectroscopy. A 1064 nm multichannel Raman spectrometer is discussed for chemical analysis of lignin. Extending dispersive multichannel Raman spectroscopy to 1064 nm reduces the fluorescence interference that can mask the weaker Raman scattering. Overall, these techniques help address the major obstacles in Raman spectroscopy for chemical analysis, which include the inherently weak Raman cross section and susceptibility to fluorescence interference.

  15. A sensitive charge scanning probe based on silicon single electron transistor

    NASA Astrophysics Data System (ADS)

    Lina, Su; Xinxing, Li; Hua, Qin; Xiaofeng, Gu

    2016-04-01

    Single electron transistors (SETs) are known to be extremely sensitive electrometers owing to their high charge sensitivity. In this work, we report the design, fabrication, and characterization of a silicon-on-insulator-based SET scanning probe. The fabricated SET is located about 10 μm away from the probe tip. The SET with a quantum dot of about 70 nm in diameter exhibits an obvious Coulomb blockade effect measured at 4.1 K. The Coulomb blockade energy is about 18 meV, and the charge sensitivity is in the order of 10‑5‑10‑3 e/Hz1/2. This SET scanning probe can be used to map charge distribution and sense dynamic charge fluctuation in nanodevices or circuits under test, realizing high sensitivity and high spatial resolution charge detection. Project supported by the Instrument Developing Project of the Chinese Academy of Sciences (No. YZ201152), the National Natural Science Foundation of China (No. 11403084), the Fundamental Research Funds for Central Universities (Nos. JUSRP51510, JUDCF12032), and the Graduate Student Innovation Program for Universities of Jiangsu Province (No. CXLX12_0724).

  16. Scanning Tunneling Spectroscopy of Proximity Superconductivity in Epitaxial Multilayer Graphene

    PubMed Central

    Natterer, Fabian D.; Ha, Jeonghoon; Baek, Hongwoo; Zhang, Duming; Cullen, William; Zhitenev, Nikolai B.; Kuk, Young; Stroscio, Joseph A.

    2016-01-01

    We report on spatial measurements of the superconducting proximity effect in epitaxial graphene induced by a graphene-superconductor interface. Superconducting aluminum films were grown on epitaxial multilayer graphene on SiC. The aluminum films were discontinuous with networks of trenches in the film morphology reaching down to exposed graphene terraces. Scanning tunneling spectra measured on the graphene terraces show a clear decay of the superconducting energy gap with increasing separation from the graphene-aluminum edges. The spectra were well described by Bardeen-Cooper-Schrieffer (BCS) theory. The decay length for the superconducting energy gap in graphene was determined to be greater than 400 nm. Deviations in the exponentially decaying energy gap were also observed on a much smaller length scale of tens of nanometers. PMID:27088134

  17. The Use Of Scanning Probe Microscopy To Investigate Crystal-Fluid Interfaces

    SciTech Connect

    Orme, C A; Giocondi, J L

    2007-04-16

    Over the past decade there has been a natural drive to extend the investigation of dynamic surfaces in fluid environments to higher resolution characterization tools. Various aspects of solution crystal growth have been directly visualized for the first time. These include island nucleation and growth using transmission electron microscopy and scanning tunneling microscopy; elemental step motion using scanning probe microscopy; and the time evolution of interfacial atomic structure using various diffraction techniques. In this lecture we will discuss the use of one such in situ method, scanning probe microscopy, as a means of measuring surface dynamics during crystal growth and dissolution. We will cover both practical aspects of imaging such as environmental control, fluid flow, and electrochemical manipulation, as well as the types of physical measurements that can be made. Measurements such as step motion, critical lengths, nucleation density, and step fluctuations, will be put in context of the information they provide about mechanistic processes at surfaces using examples from metal and mineral crystal growth.

  18. 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.

  19. 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.

  20. THE INTEGRATED USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY, AND VIRTUAL REALITY TO PREDICT THE CHEMICAL REACTIVITY OF ENVIRONMENTAL SURFACES

    EPA Science Inventory

    In the last decade three new techniques scanning probe microscopy (SPM), virtual reality (YR) and computational chemistry ave emerged with the combined capability of a priori predicting the chemically reactivity of environmental surfaces. Computational chemistry provides the cap...

  1. Nonlinear femtosecond pump-probe spectroscopy using a power-encoded soliton delay line.

    PubMed

    Saint-Jalm, Sarah; Andresen, Esben Ravn; Bendahmane, Abdelkrim; Kudlinski, Alexandre; Rigneault, Hervé

    2016-01-01

    We show femtosecond time-resolved nonlinear pump-probe spectroscopy using a fiber soliton as the probe pulse. Furthermore, we exploit soliton dynamics to record an entire transient trace with a power-encoded delay sweep. The power-encoded delay line takes advantage of the dependency of the soliton trajectory in the (λ,z) space upon input power; the difference in accumulated group delay between trajectories converts a fast power sweep into a fast delay sweep. We demonstrate the concept by performing transient absorption spectroscopy in a test sample and validate it against a conventional pump-probe setup. PMID:26696172

  2. Scanning Hall Probe Microscopy of Magnetic Vortices inVery Underdoped yttrium-barium-copper-oxide

    SciTech Connect

    Guikema, Janice Wynn; /SLAC, SSRL

    2005-12-02

    Since their discovery by Bednorz and Mueller (1986), high-temperature cuprate superconductors have been the subject of intense experimental research and theoretical work. Despite this large-scale effort, agreement on the mechanism of high-T{sub c} has not been reached. Many theories make their strongest predictions for underdoped superconductors with very low superfluid density n{sub s}/m*. For this dissertation I implemented a scanning Hall probe microscope and used it to study magnetic vortices in newly available single crystals of very underdoped YBa{sub 2}Cu{sub 3}O{sub 6+x} (Liang et al. 1998, 2002). These studies have disproved a promising theory of spin-charge separation, measured the apparent vortex size (an upper bound on the penetration depth {lambda}{sub ab}), and revealed an intriguing phenomenon of ''split'' vortices. Scanning Hall probe microscopy is a non-invasive and direct method for magnetic field imaging. It is one of the few techniques capable of submicron spatial resolution coupled with sub-{Phi}{sub 0} (flux quantum) sensitivity, and it operates over a wide temperature range. Chapter 2 introduces the variable temperature scanning microscope and discusses the scanning Hall probe set-up and scanner characterizations. Chapter 3 details my fabrication of submicron GaAs/AlGaAs Hall probes and discusses noise studies for a range of probe sizes, which suggest that sub-100 nm probes could be made without compromising flux sensitivity. The subsequent chapters detail scanning Hall probe (and SQUID) microscopy studies of very underdoped YBa{sub 2}Cu{sub 3}O{sub 6+x} crystals with T{sub c} {le} 15 K. Chapter 4 describes two experimental tests for visons, essential excitations of a spin-charge separation theory proposed by Senthil and Fisher (2000, 2001b). We searched for predicted hc/e vortices (Wynn et al. 2001) and a vortex memory effect (Bonn et al. 2001) with null results, placing upper bounds on the vison energy inconsistent with the theory. Chapter

  3. Accurate flexural spring constant calibration of colloid probe cantilevers using scanning laser Doppler vibrometry

    NASA Astrophysics Data System (ADS)

    Gates, Richard S.; Osborn, William A.; Shaw, Gordon A.

    2015-06-01

    Calibration of the flexural spring constant for atomic force microscope (AFM) colloid probe cantilevers provides significant challenges. The presence of a large attached spherical added mass complicates many of the more common calibration techniques such as reference cantilever, Sader, and added mass. Even the most promising option, AFM thermal calibration, can encounter difficulties during the optical lever sensitivity measurement due to strong adhesion and friction between the sphere and a surface. This may cause buckling of the end of the cantilever and hysteresis in the approach-retract curves resulting in increased uncertainty in the calibration. Most recently, a laser Doppler vibrometry thermal method has been used to accurately calibrate the normal spring constant of a wide variety of tipped and tipless commercial cantilevers. This paper describes a variant of the technique, scanning laser Doppler vibrometry, optimized for colloid probe cantilevers and capable of spring constant calibration uncertainties near ±1%.

  4. Ultrasonic probe deployment device for increased wave transmission and rapid area scan inspections

    SciTech Connect

    DiMambro, Joseph; Roach, Dennis P; Rackow, Kirk A; Nelson, Ciji L; Dasch, Cameron J; Moore, David G

    2013-02-12

    An ultrasonic probe deployment device in which an ultrasound-transmitting liquid forms the portion of the ultrasonic wave path in contact with the surface being inspected (i.e., the inspection surface). A seal constrains flow of the liquid, for example preventing the liquid from surging out and flooding the inspection surface. The seal is not rigid and conforms to variations in the shape and unevenness of the inspection surface, thus forming a seal (although possibly a leaky seal) around the liquid. The probe preferably is held in place to produce optimum ultrasonic focus on the area of interest. Use of encoders can facilitate the production of C-scan area maps of the material being inspected.

  5. Ultrasonic probe deployment device for increased wave transmission and rapid area scan inspections

    SciTech Connect

    DiMambro, Joseph; Roach, Dennis P.; Rackow, Kirk A.; Nelson, Ciji L.; Dasch, Cameron J.; Moore, David G.

    2012-01-03

    An ultrasonic probe deployment device in which an ultrasound-transmitting liquid forms the portion of the ultrasonic wave path in contact with the surface being inspected (i.e., the inspection surface). A seal constrains flow of the liquid, for example preventing the liquid from surging out and flooding the inspection surface. The seal is not rigid and conforms to variations in the shape and unevenness of the inspection surface, thus forming a seal (although possibly a leaky seal) around the liquid. The probe preferably is held in place to produce optimum ultrasonic focus on the area of interest. Use of encoders can facilitate the production of C-scan area maps of the material being inspected.

  6. Whispering-gallery acoustic sensing: characterization of mesoscopic films and scanning probe microscopy applications.

    PubMed

    La Rosa, Andres H; Li, Nan; Fernandez, Rodolfo; Wang, Xiaohua; Nordstrom, Richard; Padigi, S K

    2011-09-01

    Full understanding of the physics underlying the striking changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like films undergo at solid-liquid interfaces, or under confinement between two sliding solid boundaries, constitutes one of the major challenges in condensed matter physics. Their role in the imaging process of solid substrates by scanning probe microscopy (SPM) is also currently controversial. Aiming at improving the reliability and versatility of instrumentation dedicated to characterize mesoscopic films, a noninvasive whispering-gallery acoustic sensing (WGAS) technique is introduced; its application as feedback control in SPM is also demonstrated. To illustrate its working principle and potential merits, WGAS has been integrated into a SPM that uses a sharp tip attached to an electrically driven 32-kHz piezoelectric tuning fork (TF), the latter also tighten to the operating microscope's frame. Such TF-based SPMs typically monitor the TF's state of motion by electrical means, hence subjected to the effects caused by the inherent capacitance of the device (i.e., electrical resonance differing from the probe's mechanical resonance). Instead, the novelty of WGAS resides in exploiting the already existent microscope's frame as an acoustic cavity (its few centimeter-sized perimeter closely matching the operating acoustic wavelength) where standing-waves (generated by the nanometer-sized oscillations of the TF's tines) are sensitively detected by an acoustic transducer (the latter judiciously placed around the microscope's frame perimeter for attaining maximum detection). This way, WGAS is able to remote monitoring, via acoustic means, the nanometer-sized amplitude motion of the TF's tines. (This remote-detection method resembles the ability to hear faint, but still clear, levels of sound at the galleries of a cathedral, despite the extraordinary distance location of the sound source.) In applications aiming at

  7. Whispering-gallery acoustic sensing: Characterization of mesoscopic films and scanning probe microscopy applications

    NASA Astrophysics Data System (ADS)

    La Rosa, Andres H.; Li, Nan; Fernandez, Rodolfo; Wang, Xiaohua; Nordstrom, Richard; Padigi, S. K.

    2011-09-01

    Full understanding of the physics underlying the striking changes in viscoelasticity, relaxation time, and phase transitions that mesoscopic fluid-like films undergo at solid-liquid interfaces, or under confinement between two sliding solid boundaries, constitutes one of the major challenges in condensed matter physics. Their role in the imaging process of solid substrates by scanning probe microscopy (SPM) is also currently controversial. Aiming at improving the reliability and versatility of instrumentation dedicated to characterize mesoscopic films, a noninvasive whispering-gallery acoustic sensing (WGAS) technique is introduced; its application as feedback control in SPM is also demonstrated. To illustrate its working principle and potential merits, WGAS has been integrated into a SPM that uses a sharp tip attached to an electrically driven 32-kHz piezoelectric tuning fork (TF), the latter also tighten to the operating microscope's frame. Such TF-based SPMs typically monitor the TF's state of motion by electrical means, hence subjected to the effects caused by the inherent capacitance of the device (i.e., electrical resonance differing from the probe's mechanical resonance). Instead, the novelty of WGAS resides in exploiting the already existent microscope's frame as an acoustic cavity (its few centimeter-sized perimeter closely matching the operating acoustic wavelength) where standing-waves (generated by the nanometer-sized oscillations of the TF's tines) are sensitively detected by an acoustic transducer (the latter judiciously placed around the microscope's frame perimeter for attaining maximum detection). This way, WGAS is able to remote monitoring, via acoustic means, the nanometer-sized amplitude motion of the TF's tines. (This remote-detection method resembles the ability to hear faint, but still clear, levels of sound at the galleries of a cathedral, despite the extraordinary distance location of the sound source.) In applications aiming at

  8. Local Probe Spectroscopy of Two-Dimensional van der Waals Heterostructures

    NASA Astrophysics Data System (ADS)

    Yankowitz, Matthew Abraham

    A large family of materials, collectively known as "van der Waals materials", have attracted enormous research attention over the past decade following the realization that they could be isolated into individual crystalline monolayers, with charge carriers behaving effectively two-dimensionally. More recently, an even larger class of composite materials has been realized, made possible by combining the isolated atomic layers of different materials into "van der Waals heterostructures", which can exhibit electronic and optical behaviors not observed in the parent materials alone. This thesis describes efforts to characterize the atomic-scale structural and electronic properties of these van der Waals materials and heterostructures through scanning tunneling microscopy measurements. The majority of this work addresses the properties of monolayer and few-layer graphene, whose charge carriers are described by massless and massive chiral Dirac Hamiltonians, respectively. In heterostructures with hexagonal boron nitride, an insulating isomorph of graphene, we observe electronic interference patterns between the two materials which depend on their relative rotation. As a result, replica Dirac cones are formed in the valence and conduction bands of graphene, with their energy tuned by the rotation. Further, we are able to dynamically drag the graphene lattice in these heterostructures, owing to an interaction between the scanning probe tip and the domain walls formed by the electronic interference pattern. Similar dragging is observed in domain walls of trilayer graphene, whose electronic properties are found to depend on the stacking configuration of the three layers. Scanning tunneling spectroscopy provides a direct method for visualizing the scattering pathways of electrons in these materials. By analyzing the scattering, we can directly infer properties of the band structures and local environments of these heterostructures. In bilayer graphene, we map the electrically

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

    NASA Astrophysics Data System (ADS)

    Sadeghian, Hamed; Herfst, Rodolf; Winters, Jasper; Crowcombe, Will; Kramer, Geerten; van den Dool, Teun; van Es, Maarten H.

    2015-11-01

    We have developed a high speed, miniature scanning probe microscope (MSPM) integrated with a Positioning Unit (PU) for accurately positioning the MSPM on a large substrate. This combination enables simultaneous, parallel operation of many units on a large sample for high throughput measurements. The size of the MSPM is 19 × 45 × 70 mm3. It contains a one-dimensional flexure stage with counter-balanced actuation for vertical scanning with a bandwidth of 50 kHz and a z-travel range of more than 2 μm. This stage is mechanically decoupled from the rest of the MSPM by suspending it on specific dynamically determined points. The motion of the probe, which is mounted on top of the flexure stage is measured by a very compact optical beam deflection (OBD). Thermal noise spectrum measurements of short cantilevers show a bandwidth of 2 MHz and a noise of less than 15 fm/Hz1/2. A fast approach and engagement of the probe to the substrate surface have been achieved by integrating a small stepper actuator and direct monitoring of the cantilever response to the approaching surface. The PU has the same width as the MSPM, 45 mm and can position the MSPM to a pre-chosen position within an area of 275×30 mm2 to within 100 nm accuracy within a few seconds. During scanning, the MSPM is detached from the PU which is essential to eliminate mechanical vibration and drift from the relatively low-resonance frequency and low-stiffness structure of the PU. Although the specific implementation of the MSPM we describe here has been developed as an atomic force microscope, the general architecture is applicable to any form of SPM. This high speed MSPM is now being used in a parallel SPM architecture for inspection and metrology of large samples such as semiconductor wafers and masks.

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

    PubMed

    Sadeghian, Hamed; Herfst, Rodolf; Winters, Jasper; Crowcombe, Will; Kramer, Geerten; van den Dool, Teun; van Es, Maarten H

    2015-11-01

    We have developed a high speed, miniature scanning probe microscope (MSPM) integrated with a Positioning Unit (PU) for accurately positioning the MSPM on a large substrate. This combination enables simultaneous, parallel operation of many units on a large sample for high throughput measurements. The size of the MSPM is 19 × 45 × 70 mm(3). It contains a one-dimensional flexure stage with counter-balanced actuation for vertical scanning with a bandwidth of 50 kHz and a z-travel range of more than 2 μm. This stage is mechanically decoupled from the rest of the MSPM by suspending it on specific dynamically determined points. The motion of the probe, which is mounted on top of the flexure stage is measured by a very compact optical beam deflection (OBD). Thermal noise spectrum measurements of short cantilevers show a bandwidth of 2 MHz and a noise of less than 15 fm/Hz(1/2). A fast approach and engagement of the probe to the substrate surface have been achieved by integrating a small stepper actuator and direct monitoring of the cantilever response to the approaching surface. The PU has the same width as the MSPM, 45 mm and can position the MSPM to a pre-chosen position within an area of 275×30 mm(2) to within 100 nm accuracy within a few seconds. During scanning, the MSPM is detached from the PU which is essential to eliminate mechanical vibration and drift from the relatively low-resonance frequency and low-stiffness structure of the PU. Although the specific implementation of the MSPM we describe here has been developed as an atomic force microscope, the general architecture is applicable to any form of SPM. This high speed MSPM is now being used in a parallel SPM architecture for inspection and metrology of large samples such as semiconductor wafers and masks. PMID:26628143

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

    SciTech Connect

    Sadeghian, Hamed E-mail: h.sadeghianmarnani@tudelft.nl; Herfst, Rodolf; Winters, Jasper; Crowcombe, Will; Kramer, Geerten; Dool, Teun van den; Es, Maarten H. van

    2015-11-15

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

  12. A line-scan hyperspectral Raman system for spatially offset Raman spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conventional methods of spatially offset Raman spectroscopy (SORS) typically use single-fiber optical measurement probes to slowly and incrementally collect a series of spatially offset point measurements moving away from the laser excitation point on the sample surface, or arrays of multiple fiber ...

  13. Scanning Hall probe microscopy of magnetic vortices in very underdoped yttrium-barium-copper-oxide

    NASA Astrophysics Data System (ADS)

    Guikema, Janice Wynn

    Since their discovery by Bednorz and Muller in 1986, high-temperature cuprate superconductors have been the subject of intense research. Despite this effort, agreement on the mechanism of high- Tc has not been reached. Many theories make their strongest predictions for underdoped superconductors with very low superfluid density ns/m*. I implemented a scanning Hall probe microscope (SHPM) and used it to study magnetic vortices in newly available single crystals of very underdoped YBa2Cu3O6+x . These studies have disproved a promising theory of spin-charge separation, measured the apparent vortex size (an upper bound on the penetration depth lambda ab), and revealed an intriguing phenomenon of "split" vortices. SHPM is a non-invasive and direct method for magnetic field imaging. It is one of the few techniques capable of submicron spatial resolution coupled with sub-phi0 (flux quantum) sensitivity, and it operates over a wide temperature range. Chapter 2 introduces the variable temperature scanning microscope and discusses the scanning Hall probe set-up and scanner characterizations. Chapter 3 details my fabrication of submicron GaAs/AlGaAs Hall probes and discusses noise studies for a range of probe sizes, which suggest that sub-100 nm probes could be made without compromising flux sensitivity. The subsequent chapters detail SHPM (and SQUID) studies of very underdoped YBa2Cu3O6+x crystals with T c ≤ 15 K. Chapter 4 describes two experimental tests for visons, essential excitations of a spin-charge separation theory proposed by Senthil and Fisher. We searched for predicted hc/ e vortices and a vortex memory effect with null results, placing upper bounds on the vison energy inconsistent with the theory. Chapter 5 discusses imaging of isolated vortices as a function of Tc. Vortex images were fit with theoretical magnetic field profiles in order to extract the apparent vortex size. The data for the lowest Tc 's (5 and 6.5 K) show some inhomogeneity and suggest that

  14. What is Scanning Probe Microscopy? And How Can It Be Used In Failure Analysis?

    SciTech Connect

    Campbell, A.; Tangyunyong, P.

    1999-03-26

    Scanning probe microscopy (SPM) techniques are not suitable as global defect-localization tools. They can, however, pinpoint the exact location of the defects once the approximate locations of the defects have been identified by other failure analysis techniques. SPM techniques also provide information such as 3-D topology, current, surface potential, and 2-D dopant profile that may not be readily obtainable with other techniques. This information, coupled with the unparalleled spatial resolution and high detection sensitivity can be used by failure analysts for root cause analysis.

  15. Bioelectromechanical Imaging by Scanning Probe Microscopy: Galvani's Experiment at the Nanoscale

    SciTech Connect

    Kalinin, Sergei V; Rodriguez, Brian J; Shin, Junsoo; Jesse, Stephen; Grichko, V.; Thundat, Thomas George; Baddorf, Arthur P; Gruverman, A.

    2006-01-01

    Since the discovery in the late 18th century of electrically induced mechanical response in muscle tissue, coupling between electrical and mechanical phenomena has been shown to be a near-universal feature of biological systems. Here, we employ scanning probe microscopy (SPM) to measure the sub-Angstrom mechanical response of a biological system induced by an electric bias applied to a conductive SPM tip. Visualization of the spiral shape and orientation of protein fibrils with 5 nm spatial resolution in a human tooth and chitin molecular bundle orientation in a butterfly wing is demonstrated. In particular, the applicability of SPM-based techniques for the determination of molecular orientation is discussed.

  16. Emerging scanning probe approaches to the measurement of ionic reactivity at energy storage materials.

    PubMed

    Barton, Zachary J; Rodríguez-López, Joaquín

    2016-04-01

    Many modern energy storage technologies operate via the nominally reversible shuttling of alkali ions between an anode and a cathode capable of hosting them. The degradation process that occurs with normal usage is not yet fully understood, but emerging progress in analytical tools may help address this knowledge gap. By interrogating ionic fluxes over electrified surfaces, scanning probe methods may identify features that impact the local cyclability of a material and subsequently help inform rational electrode design for future generations of batteries. Methods developed for identifying ion fluxes for batteries show great promise for broader applications, including biological interfaces, corrosion, and catalysis. Graphical Abstract Versatile ionics for next-generation batteries. PMID:26898202

  17. Principal Component Analysis of Spectroscopic Imaging Data in Scanning Probe Microscopy

    SciTech Connect

    Jesse, Stephen; Kalinin, Sergei V

    2009-01-01

    The approach for data analysis in band excitation family of scanning probe microscopies based on principal component analysis (PCA) is explored. PCA utilizes the similarity between spectra within the image to select the relevant response components. For small signal variations within the image, the PCA components coincide with the results of deconvolution using simple harmonic oscillator model. For strong signal variations, the PCA allows effective approach to rapidly process, de-noise and compress the data. The extension of PCA for correlation function analysis is demonstrated. The prospects of PCA as a universal tool for data analysis and representation in multidimensional SPMs are discussed.

  18. Transition of oxide film configuration and the critical stress inferred by scanning probe microscopy at nanoscale

    NASA Astrophysics Data System (ADS)

    Fang, Xufei; Li, Yan; Zhang, Changxing; Dong, Xuelin; Feng, Xue

    2016-09-01

    Scanning probe microscopy (SPM) equipped in high temperature nanoindentation instrument is adopted to in situ characterize the oxide film growth on Ni-base single crystal at nanoscale. SPM images reveal a transition of oxide film configuration that the originally flat surface roughens during oxidation. Based on the stress-diffusion coupling effect during oxidation, the stress evolution in the oxide film and the evolution of surface configuration are analyzed. A new method to infer the critical stress in the oxide film at the transition point is proposed by measuring the undulated surface wavelength based on the surface morphology obtained by SPM.

  19. Electrostrictive and electrostatic responses in contact mode voltage modulated Scanning Probe Microscopies

    SciTech Connect

    Eliseev, E. A.; Morozovska, A. N.; Ievlev, Anton; Balke, Nina; Maksymovych, Petro; Tselev, Alexander; Kalinin, Sergei V

    2014-01-01

    Electromechanical response of solids underpins image formation mechanism of several scanning probe microscopy techniques including the piezoresponse force microscopy (PFM) and electrochemical strain microscopy (ESM). While the theory of linear piezoelectric and ionic responses are well developed, the contributions of quadratic effects including electrostriction and capacitive tip-surface forces to measured signal remain poorly understood. Here we analyze the electrostrictive and capacitive contributions to the PFM and ESM signals and discuss the implications of the dielectric tip-surface gap on these interactions.

  20. Teaching Plasmonics, Scanning Probe Microscopy and Other Useful Experiments at the Upper Level

    NASA Astrophysics Data System (ADS)

    Sanchez, Erik

    2012-10-01

    It is important to teach students concepts and experimental skills relating to modern research being performed today. Experiments that help educate students about the latest research helps them get jobs and into the doors at many great academic institutions. PSU's Advanced Experimental Class for physics undergraduates offers many novel experiments to help the students accomplish this task. Labs involving Plasmonics, thin film deposition, scanning probe microscopy (SPM) and more will be discussed. In addition, a new NSF funded project involving the building of a Do-It-Yourself (DIY) SPM will be discussed.

  1. Hotspot decorations map plasmonic patterns with the resolution of scanning probe techniques.

    PubMed

    Valev, V K; Silhanek, A V; Jeyaram, Y; Denkova, D; De Clercq, B; Petkov, V; Zheng, X; Volskiy, V; Gillijns, W; Vandenbosch, G A E; Aktsipetrov, O A; Ameloot, M; Moshchalkov, V V; Verbiest, T

    2011-06-01

    In high definition mapping of the plasmonic patterns on the surfaces of nanostructures, the diffraction limit of light remains an important obstacle. Here we demonstrate that this diffraction limit can be completely circumvented. We show that upon illuminating nanostructures made of nickel and palladium, the resulting surface-plasmon pattern is imprinted on the structures themselves; the hotspots (regions of local field enhancement) are decorated with overgrowths, allowing for their subsequent imaging with scanning-probe techniques. The resulting resolution of plasmon pattern imaging is correspondingly improved. PMID:21702624

  2. Enabling freehand lateral scanning of optical coherence tomography needle probes with a magnetic tracking system

    PubMed Central

    Yeo, Boon Y.; McLaughlin, Robert A.; Kirk, Rodney W.; Sampson, David D.

    2012-01-01

    We present a high-resolution three-dimensional position tracking method that allows an optical coherence tomography (OCT) needle probe to be scanned laterally by hand, providing the high degree of flexibility and freedom required in clinical usage. The method is based on a magnetic tracking system, which is augmented by cross-correlation-based resampling and a two-stage moving window average algorithm to improve upon the tracker's limited intrinsic spatial resolution, achieving 18 µm RMS position accuracy. A proof-of-principle system was developed, with successful image reconstruction demonstrated on phantoms and on ex vivo human breast tissue validated against histology. This freehand scanning method could contribute toward clinical implementation of OCT needle imaging. PMID:22808429

  3. Specification, design and commissioning of an ultra-low-vibration facility for Scanning probe microscopy experiments

    NASA Astrophysics Data System (ADS)

    MacLeod, Benjamin; Pennec, Yan; Wong, Vincent; Adamson, Graeme

    2012-10-01

    Scanning probe microscopes are perhaps best known for being able to image individual atoms in real space. A practical complication of this extreme spatial sensitivity is that these instruments are also extremely sensitive to mechanical vibrations; to approach ultimate levels of performance, these microscopes must therefore be operated in an environment with an extremely low level of mechanical vibrations. In this work, the specification, design and commissioning of a new ultra-low-vibration facility recently completed at the University of British Columbia is presented. Based on the pneumatically-suspended inertial slab concept used at NIST's Gaithersburg facilityfootnotetextHal Amick, Bea Sennewald, Norman C. Pardue, Clayton Teague, and Brian Scace, Noise Control Engineering Journal 46, 39-47 (1998). this system will be used as a highly stable platform for a 50mK Scanning Tunneling Microscope system.

  4. Comment on ``MEMS-based high speed scanning probe microscopy'' [Rev. Sci. Instrum. 81, 043702 (2010)

    NASA Astrophysics Data System (ADS)

    Degertekin, F. Levent; Torun, Hamdi

    2010-11-01

    In a recent article, Disseldorp et al. [Rev. Sci. Instrum. 81, 043702 (2010)] present a micromachined z-scanner for scanning probe microscopy (SPM). The scanner comprises a micromachined electrostatically actuated membrane anchored to its substrate with crab-leg flexures. This structure is used as a fast actuator specifically for atomic force microscope and scanning tunneling microscope. The authors present topographic images acquired using the scanner in this paper and elsewhere [F. C. Tabak et al., Ultramicroscopy 110, 599 (2010)]. Although the work is clearly described, it does not appear to be placed in proper context. For example, the authors claim that previous work on microelectromechanical systems SPM has not been focused on high-speed imaging with feedback, which is not supported by the existing literature. In addition, similar actuator structures, albeit slightly larger scale, have been designed and used for SPM applications. Here, we would like comment briefly on the existing literature to clarify the significance of the work.

  5. Finger probe array for topography-tolerant scanning electrochemical microscopy of extended samples.

    PubMed

    Lesch, Andreas; Chen, Po-Chung; Roelfs, Folkert; Dosche, Carsten; Momotenko, Dmitry; Cortés-Salazar, Fernando; Girault, Hubert H; Wittstock, Gunther

    2014-01-01

    Scanning electrochemical microscopy with soft microelectrode array probes has recently been used to enable reactivity imaging of extended areas and to compensate sample corrugation perpendicular to the scanning direction. Here, the use of a new type of microelectrode arrays is described in which each individual microelectrode can independently compensate corrugations of the sample surface. It consists of conventional Pt microelectrodes enclosed in an insulating glass sheath. The microelectrodes are individually fixed to a new holder system by magnetic forces. The concept was tested using a large 3D sample with heights up to 12 μm specially prepared by inkjet printing. The microelectrodes follow the topography in a constant working distance independently from each other while exerting low pressure on the surface. PMID:24328212

  6. Characterizing Surfaces of the Wide Bandgap Semiconductor Ilmenite with Scanning Probe Microcopies

    NASA Technical Reports Server (NTRS)

    Wilkins, R.; Powell, Kirk St. A.

    1997-01-01

    Ilmenite (FeTiO3) is a wide bandgap semiconductor with an energy gap of about 2.5eV. Initial radiation studies indicate that ilmenite has properties suited for radiation tolerant applications, as well as a variety of other electronic applications. Two scanning probe microscopy methods have been used to characterize the surface of samples taken from Czochralski grown single crystals. The two methods, atomic force microscopy (AFM) and scanning tunneling microscopy (STM), are based on different physical principles and therefore provide different information about the samples. AFM provides a direct, three-dimensional image of the surface of the samples, while STM give a convolution of topographic and electronic properties of the surface. We will discuss the differences between the methods and present preliminary data of each method for ilmenite samples.

  7. Orthogonal Supramolecular Polymer Formation on Highly Oriented Pyrolytic Graphite (HOPG) Surfaces Characterized by Scanning Probe Microscopy.

    PubMed

    Gong, Yongxiang; Zhang, Siqi; Geng, Yanfang; Niu, Chunmei; Yin, Shouchun; Zeng, Qingdao; Li, Min

    2015-10-27

    Formation of an orthogonal supramolecular polymer on a highly oriented pyrolytic graphite (HOPG) surface was demonstrated for the first time by means of scanning probe microscopy (SPM). Atomic force microscopy (AFM) was employed to characterize the variation of both the thickness and the topography of the film formed from (1) monomer 1, (2) monomer 1/Zn(2+), and (3) monomer 1/Zn(2+)/cross-linker 2, respectively. Scanning tunneling microscopy (STM) was used to monitor the self-assembly behavior of monomer 1 itself, as well as 1/Zn(2+) ions binary system on graphite surface, further testifying for the formation of linear polymer via coordination interaction at the single molecule level. These results, given by the strong surface characterization tool of SPM, confirm the formation of the orthogonal polymer on the surface of graphite, which has great significance in regard to fabricating a complex superstructure on surfaces. PMID:26457462

  8. Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

    NASA Astrophysics Data System (ADS)

    Pelliccione, Matthew; Jenkins, Alec; Ovartchaiyapong, Preeti; Reetz, Christopher; Emmanuelidu, Eve; Ni, Ni; Bleszynski Jayich, Ania

    The nitrogen vacancy (NV) defect in diamond has emerged as a promising candidate for high resolution magnetic imaging based on its atomic size and quantum-limited sensing capabilities afforded by long spin coherence times. Although the NV center has been successfully implemented as a nanoscale scanning magnetic probe at room temperature, it has remained an outstanding challenge to extend this capability to cryogenic temperatures, where many solid-state systems exhibit non-trivial magnetic order. In this talk, we present NV magnetic imaging at T = 6 K, first benchmarking the technique with a magnetic hard disk sample, then utilizing the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with Tc = 30 K. In addition, we discuss other candidate solid-state systems that can benefit from the high spatial resolution and field sensitivity of the scanning NV magnetometer.

  9. Fabrication of Si nanowires on Si (100) using a scanning probe tip

    NASA Astrophysics Data System (ADS)

    Smith, Joshua; Davis, Robert; Dang, Ying Yi; Fedder, Gary; Bain, Jim; Ricketts, David

    2009-03-01

    Reliable fabrication on the nanoscale is becoming increasingly important. The co-author team is investigating a nanolithography technique for the deposition of nanoscale features entitled ``Tip-directed, field-emission assisted nanomanufacturing'' (TFAN). The TFAN process involves the adsorption of a layer of silicon-containing gas, such as disilane, to a substrate and the selective patterning of the surface with field-emitted electrons from a scanning probe tip. The electrons crack the Si containing molecules, which results in the deposition of Si on the substrate. The adsorption of the Si-containing molecules to the substrate surface is critical to the success of this approach. The investigation involves the determination of the coverage, sticking coefficient, and time constant of disilane on the Si(100) surface using temperature programmed desorption and scanning tunneling microscopy.

  10. Self-sensing cantilevers with integrated conductive coaxial tips for high-resolution electrical scanning probe metrology

    NASA Astrophysics Data System (ADS)

    Haemmerli, Alexandre J.; Harjee, Nahid; Koenig, Markus; Garcia, Andrei G. F.; Goldhaber-Gordon, David; Pruitt, Beth L.

    2015-07-01

    The lateral resolution of many electrical scanning probe techniques is limited by the spatial extent of the electrostatic potential profiles produced by their probes. Conventional unshielded conductive atomic force microscopy probes produce broad potential profiles. Shielded probes could offer higher resolution and easier data interpretation in the study of nanostructures. Electrical scanning probe techniques require a method of locating structures of interest, often by mapping surface topography. As the samples studied with these techniques are often photosensitive, the typical laser measurement of cantilever deflection can excite the sample, causing undesirable changes electrical properties. In this work, we present the design, fabrication, and characterization of probes that integrate coaxial tips for spatially sharp potential profiles with piezoresistors for self-contained, electrical displacement sensing. With the apex 100 nm above the sample surface, the electrostatic potential profile produced by our coaxial tips is more than 2 times narrower than that of unshielded tips with no long tails. In a scan bandwidth of 1 Hz-10 kHz, our probes have a displacement resolution of 2.9 Å at 293 K and 79 Å at 2 K, where the low-temperature performance is limited by amplifier noise. We show scanning gate microscopy images of a quantum point contact obtained with our probes, highlighting the improvement to lateral resolution resulting from the coaxial tip.

  11. Self-sensing cantilevers with integrated conductive coaxial tips for high-resolution electrical scanning probe metrology

    SciTech Connect

    Haemmerli, Alexandre J.; Pruitt, Beth L.; Harjee, Nahid; Koenig, Markus; Garcia, Andrei G. F.; Goldhaber-Gordon, David

    2015-07-21

    The lateral resolution of many electrical scanning probe techniques is limited by the spatial extent of the electrostatic potential profiles produced by their probes. Conventional unshielded conductive atomic force microscopy probes produce broad potential profiles. Shielded probes could offer higher resolution and easier data interpretation in the study of nanostructures. Electrical scanning probe techniques require a method of locating structures of interest, often by mapping surface topography. As the samples studied with these techniques are often photosensitive, the typical laser measurement of cantilever deflection can excite the sample, causing undesirable changes electrical properties. In this work, we present the design, fabrication, and characterization of probes that integrate coaxial tips for spatially sharp potential profiles with piezoresistors for self-contained, electrical displacement sensing. With the apex 100 nm above the sample surface, the electrostatic potential profile produced by our coaxial tips is more than 2 times narrower than that of unshielded tips with no long tails. In a scan bandwidth of 1 Hz–10 kHz, our probes have a displacement resolution of 2.9 Å at 293 K and 79 Å at 2 K, where the low-temperature performance is limited by amplifier noise. We show scanning gate microscopy images of a quantum point contact obtained with our probes, highlighting the improvement to lateral resolution resulting from the coaxial tip.

  12. Development of a c-scan photoacoutsic imaging probe for prostate cancer detection

    NASA Astrophysics Data System (ADS)

    Valluru, Keerthi S.; Chinni, Bhargava K.; Rao, Navalgund A.; Bhatt, Shweta; Dogra, Vikram S.

    2011-03-01

    Prostate cancer is the second leading cause of death in American men after lung cancer. The current screening procedures include Digital Rectal Exam (DRE) and Prostate Specific Antigen (PSA) test, along with Transrectal Ultrasound (TRUS). All suffer from low sensitivity and specificity in detecting prostate cancer in early stages. There is a desperate need for a new imaging modality. We are developing a prototype transrectal photoacoustic imaging probe to detect prostate malignancies in vivo that promises high sensitivity and specificity. To generate photoacoustic (PA) signals, the probe utilizes a high energy 1064 nm laser that delivers light pulses onto the prostate at 10Hz with 10ns duration through a fiber optic cable. The designed system will generate focused C-scan planar images using acoustic lens technology. A 5 MHz custom fabricated ultrasound sensor array located in the image plane acquires the focused PA signals, eliminating the need for any synthetic aperture focusing. The lens and sensor array design was optimized towards this objective. For fast acquisition times, a custom built 16 channel simultaneous backend electronics PCB has been developed. It consists of a low-noise variable gain amplifier and a 16 channel ADC. Due to the unavailability of 2d ultrasound arrays, in the current implementation several B-scan (depth-resolved) data is first acquired by scanning a 1d array, which is then processed to reconstruct either 3d volumetric images or several C-scan planar images. Experimental results on excised tissue using a in-vitro prototype of this technology are presented to demonstrate the system capability in terms of resolution and sensitivity.

  13. Scanning gate spectroscopy of transport across a quantum Hall nano-island

    NASA Astrophysics Data System (ADS)

    Martins, F.; Faniel, S.; Rosenow, B.; Pala, M. G.; Sellier, H.; Huant, S.; Desplanque, L.; Wallart, X.; Bayot, V.; Hackens, B.

    2013-01-01

    We explore transport across an ultra-small quantum Hall island (QHI) formed by closed quantum Hall edge states and connected to propagating edge channels through tunnel barriers. Scanning gate microscopy and scanning gate spectroscopy are used to first localize and then study a single QHI near a quantum point contact. The presence of Coulomb diamonds in the spectroscopy confirms that Coulomb blockade governs transport across the QHI. Varying the microscope tip bias as well as current bias across the device, we uncover the QHI discrete energy spectrum arising from electronic confinement and we extract estimates of the gradient of the confining potential and of the edge state velocity.

  14. 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.

  15. Correction of distortion due to thermal drift in scanning probe microscopy.

    PubMed

    Salmons, Brian S; Katz, Daniel R; Trawick, Matthew L

    2010-03-01

    A common source of distortion in scanning probe microscope (SPM) images is "thermal drift," the slow thermal expansion of different materials in the sample and microscope due to small changes in temperature over the course of a scan. We describe here a method for correcting this distortion by immediately following each image scan with a rescan of a small, narrow portion of the same area with the slow and fast scan axes reversed. The original, full image is corrected using a low-order polynomial mapping function, with coefficients determined by a pixel-wise comparison between the original full and rescanned partial images. We demonstrate here that this method can correctly remove distortion from a wide range of images with a precision of better than one pixel, and is also robust to common imaging artifacts. We also address some of the programming considerations that have gone into implementing this computationally intensive technique, which can now be performed using standard desktop hardware in times that range between a few seconds and a few minutes. PMID:20149540

  16. Thymine Dimer Formation probed by Time-Resolved Vibrational Spectroscopy

    NASA Astrophysics Data System (ADS)

    Schreier, Wolfgang J.; Schrader, Tobias E.; Roller, Florian O.; Gilch, Peter; Zinth, Wolfgang; Kohler, Bern

    Cyclobutane pyrimidine dimers are the major photoproducts formed when DNA is exposed to UV light. Femtosecond time-resolved vibrational spectroscopy reveals that thymine dimers are formed in thymidine oligonucleotides in an ultrafast photoreaction.

  17. Direct and quantitative broadband absorptance spectroscopy with multilayer cantilever probes

    SciTech Connect

    Hsu, Wei-Chun; Tong, Jonathan Kien-Kwok; Liao, Bolin; Chen, Gang

    2015-04-21

    A system for measuring the absorption spectrum of a sample is provided that includes a broadband light source that produces broadband light defined within a range of an absorptance spectrum. An interferometer modulates the intensity of the broadband light source for a range of modulation frequencies. A bi-layer cantilever probe arm is thermally connected to a sample arm having at most two layers of materials. The broadband light modulated by the interferometer is directed towards the sample and absorbed by the sample and converted into heat, which causes a temperature rise and bending of the bi-layer cantilever probe arm. A detector mechanism measures and records the deflection of the probe arm so as to obtain the absorptance spectrum of the sample.

  18. Monte Carlo analysis on probe performance for endoscopic diffuse optical spectroscopy of tubular organ

    NASA Astrophysics Data System (ADS)

    Zhang, Yunyao; Zhu, Jingping; Cui, Weiwen; Nie, Wei; Li, Jie; Xu, Zhenghong

    2015-03-01

    We investigated the performance of endoscopic diffuse optical spectroscopy probes with circular or linear fiber arrangements for tubular organ cancer detection. Probe performance was measured by penetration depth. A Monte Carlo model was employed to simulate light transport in the hollow cylinder that both emits and receives light from the inner boundary of the sample. The influence of fiber configurations and tissue optical properties on penetration depth was simulated. The results show that under the same condition, probes with circular fiber arrangement penetrate deeper than probes with linear fiber arrangement, and the difference between the two probes' penetration depth decreases with an increase in the 'distance between source and detector (SD)' and the radius of the probe. Other results show that the penetration depths and their differences both decrease with an increase in the absorption coefficient and the reduced scattering coefficient but remain constant with changes in the anisotropy factor. Moreover, the penetration depth was more affected by the absorption coefficient than the reduced scattering coefficient. It turns out that in NIR band, probes with linear fiber arrangements are more appropriate for diagnosing superficial cancers, whereas probes with circular fiber arrangements should be chosen for diagnosing adenocarcinoma. But in UV-VIS band, the two probe configurations exhibit nearly the same. These results are useful in guiding endoscopic diffuse optical spectroscopy-based diagnosis for esophageal, cervical, colorectal and other cancers.

  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. Nanolithography by scanning probes on calixarene molecular glass resist using mix-and-match lithography

    NASA Astrophysics Data System (ADS)

    Kaestner, Marcus; Hofer, Manuel; Rangelow, Ivo W.

    2013-07-01

    Going "beyond the CMOS information-processing era," taking advantage of quantum effects occurring at sub-10-nm level, requires novel device concepts and associated fabrication technologies able to produce promising features at acceptable cost levels. Herein, the challenge affecting the lithographic technologies comprises the marriage of down-scaling the device-relevant feature size towards single-nanometer resolution with a simultaneous increase of the throughput capabilities. Mix-and-match lithographic strategies are one promising path to break through this trade-off. Proof-of-concept combining electron beam lithography (EBL) with the outstanding capabilities of closed-loop electric field current-controlled scanning probe nanolithography (SPL) is demonstrated. This combination, whereby also extreme ultraviolet lithography (EUVL) is possible instead of EBL, enables more: improved patterning resolution and reproducibility in combination with excellent overlay and placement accuracy. Furthermore, the symbiosis between EBL (EUVL) and SPL expands the process window of EBL (EUVL) beyond the state of the art, allowing SPL-based pre- and post-patterning of EBL (EUVL) written features at critical dimension levels with scanning probe microscopy-based pattern overlay alignment capability. Moreover, we are able to modify the EBL (EUVL) pattern even after the development step. The ultra-high resolution mix-and-match lithography experiments are performed on the molecular glass resist calixarene using a Gaussian e-beam lithography system operating at 10 keV and a home-developed SPL setup.

  1. Facile Preparation of a Platinum Silicide Nanoparticle-Modified Tip Apex for Scanning Kelvin Probe Microscopy.

    PubMed

    Lin, Chun-Ting; Chen, Yu-Wei; Su, James; Wu, Chien-Ting; Hsiao, Chien-Nan; Shiao, Ming-Hua; Chang, Mao-Nan

    2015-12-01

    In this study, we propose an ultra-facile approach to prepare a platinum silicide nanoparticle-modified tip apex (PSM tip) used for scanning Kelvin probe microscopy (SKPM). We combined a localized fluoride-assisted galvanic replacement reaction (LFAGRR) and atmospheric microwave annealing (AMA) to deposit a single platinum silicide nanoparticle with a diameter of 32 nm on the apex of a bare silicon tip of atomic force microscopy (AFM). The total process was completed in an ambient environment in less than 3 min. The improved potential resolution in the SKPM measurement was verified. Moreover, the resolution of the topography is comparable to that of a bare silicon tip. In addition, the negative charges found on the PSM tips suggest the possibility of exploring the use of current PSM tips to sense electric fields more precisely. The ultra-fast and cost-effective preparation of the PSM tips provides a new direction for the preparation of functional tips for scanning probe microscopy. PMID:26471480

  2. Near-field microwave scanning probe imaging of conductivity inhomogeneities in CVD graphene.

    PubMed

    Tselev, Alexander; Lavrik, Nickolay V; Vlassiouk, Ivan; Briggs, Dayrl P; Rutgers, Maarten; Proksch, Roger; Kalinin, Sergei V

    2012-09-28

    We have performed near-field scanning microwave microscopy (SMM) of graphene grown by chemical vapor deposition. Due to the use of probe-sample capacitive coupling and a relatively high ac frequency of a few GHz, this scanning probe method allows mapping of local conductivity without a dedicated counter electrode, with a spatial resolution of about 50 nm. Here, the coupling was enabled by atomic layer deposition of alumina on top of graphene, which in turn enabled imaging both large-area films, as well as micron-sized islands, with a dynamic range covering a low sheet resistance of a metal film and a high resistance of highly disordered graphene. The structures of graphene grown on Ni films and Cu foils are explored, and the effects of growth conditions are elucidated. We present a simple general scheme for interpretation of the contrast in the SMM images of our graphene samples and other two-dimensional conductors, which is supported by extensive numerical finite-element modeling. We further demonstrate that combination of the SMM and numerical modeling allows quantitative information about the sheet resistance of graphene to be obtained, paving the pathway for characterization of graphene conductivity with a sub-100 nm special resolution. PMID:22948033

  3. Near-field Microwave Scanning Probe Imaging of Conductivity Inhomogeneities in CVD Graphene

    SciTech Connect

    Tselev, Alexander; Lavrik, Nickolay V; Vlassiouk, Ivan V; Briggs, Dayrl P; Rutgers, Maarten; Proksch, Roger; Kalinin, Sergei V

    2012-01-01

    We have performed near-field scanning microwave microscopy (SMM) of graphene grown by chemical vapor deposition. Due to the use of probe-sample capacitive coupling and a relatively high ac frequency of a few GHz, this scanning probe method allows mapping of local conductivity without a dedicated counter electrode, with a spatial resolution of about 50 nm. Here, the coupling was enabled by atomic layer deposition of alumina on top of graphene, which in turn enabled imaging both large-area films, as well as micron-sized islands, with a dynamic range covering a low sheet resistance of a metal film and a high resistance of highly disordered graphene. The structures of graphene grown on Ni films and Cu foils are explored, and the effects of growth conditions are elucidated. We present a simple general scheme for interpretation of the contrast in the SMM images of our graphene samples and other two-dimensional conductors, which is supported by extensive numerical finite-element modeling. We further demonstrate that combination of the SMM and numerical modeling allows quantitative information about the sheet resistance of graphene to be obtained, paving the pathway for characterization of graphene conductivity with a sub-100 nm special resolution.

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

    SciTech Connect

    Wu Yan; Shannon, Mark A.

    2006-04-15

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

  5. Nanoscale Radiative Heat Transfer between a Scanning Probe and a Flat Surface

    NASA Astrophysics Data System (ADS)

    Song, Bai; Kim, Kyeongtae; Lee, Woochul; Jeong, Won Ho; Meyhofer, Edgar; Reddy, Pramod

    2014-03-01

    Fluctuational electrodynamics based calculations predict a significant increase in the efficiency of thermophotovoltaic devices when an emitter is placed in the close proximity of an appropriately designed photovoltaic (PV) cell. The enhancement is expected to be further increased if the emissive properties of the emitter are matched to the band gap of the PV cell via nanostructuring. However, before this can be accomplished, it is necessary to better understand the underlying physics. This is especially true given the discrepancies seen between published experimental and theoretical studies. Here we present our measurements of nanoscale radiative heat transfer between the tip of scanning probes and an atomically flat surface spatially separated by very small gaps (1-10 nm). The experiments were performed in a UHV environment using custom-developed scanning probed with picowatt heat-flow resolution. Current measurements show significant deviations from computational predictions. We are currently studying radiative thermal transport between a range of materials to reveal the contribution of important effects such as non-locality and eddy currents. 1) US Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under award no. DE-SC0004871 2) Army Research office (W911NF-12-1-0612), 3) NSF Thermal Transport Prcesses (CBET 1235691).

  6. Advanced electric-field scanning probe lithography on molecular resist using active cantilever

    NASA Astrophysics Data System (ADS)

    Kaestner, Marcus; Aydogan, Cemal; Ivanov, Tzvetan; Ahmad, Ahmad; Angelov, Tihomir; Reum, Alexander; Ishchuk, Valentyn; Krivoshapkina, Yana; Hofer, Manuel; Lenk, Steve; Atanasov, Ivaylo; Holz, Mathias; Rangelow, Ivo W.

    2015-07-01

    The routine "on demand" fabrication of features smaller than 10 nm opens up new possibilities for the realization of many devices. Driven by the thermally actuated piezoresistive cantilever technology, we have developed a prototype of a scanning probe lithography (SPL) platform which is able to image, inspect, align, and pattern features down to the single digit nanoregime. Here, we present examples of practical applications of the previously published electric-field based current-controlled scanning probe lithography. In particular, individual patterning tests are carried out on calixarene by using our developed table-top SPL system. We have demonstrated the application of a step-and-repeat SPL method including optical as well as atomic force microscopy-based navigation and alignment. The closed-loop lithography scheme was applied to sequentially write positive and negative tone features. Due to the integrated unique combination of read-write cycling, each single feature is aligned separately with the highest precision and inspected after patterning. This routine was applied to create a pattern step by step. Finally, we have demonstrated the patterning over larger areas, over existing topography, and the practical applicability of the SPL processes for lithography down to 13-nm pitch patterns. To enhance the throughput capability variable beam diameter electric field, current-controlled SPL is briefly discussed.

  7. Microfabrication of patterns of adherent marine bacterium Phaeobacter inhibens using soft lithography and scanning probe lithography.

    PubMed

    Zhao, Chuan; Burchardt, Malte; Brinkhoff, Thorsten; Beardsley, Christine; Simon, Meinhard; Wittstock, Gunther

    2010-06-01

    Two lithographic approaches have been explored for the microfabrication of cellular patterns based on the attachment of marine bacterium Phaeobacter inhibens strain T5. Strain T5 produces a new antibiotic that makes this bacterium potentially interesting for the pharmaceutical market and as a probiotic organism in aquacultures and in controlling biofouling. The microcontact printing (microCP) method is based on the micropatterning of self-assembled monolayers (SAMs) terminated with adhesive end groups such as CH(3) and COOH and nonadhesive groups (e.g., short oligomers of ethylene glycol (OEG)) to form micropatterned substrates for the adhesion of strain T5. The scanning probe lithographic method is based on the surface modification of OEG SAM by using a microelectrode, the probe of a scanning electrochemical microscope (SECM). Oxidizing agents (e.g., Br(2)) were electrogenerated in situ at the microelectrodes from Br(-) in aqueous solution to remove OEG SAMs locally, which allows the subsequent adsorption of bacteria. Various micropatterns of bacteria could be formed in situ on the substrate without a prefabricated template. The fabricated cellular patterns may be applied to a variety of marine biological studies that require the analysis of biofilm formation, cell-cell and cell-surface interactions, and cell-based biosensors and bioelectronics. PMID:20397716

  8. Novel failure analysis techniques using photon probing with a scanning optical microscope

    SciTech Connect

    Cole, E.I. Jr.; Soden, J.M.; Rife, J.L.; Barton, D.L.; Henderson, C.L.

    1993-12-31

    Three new failure analysis techniques for integrated circuits (ICs) have been developed using localized photon probing with a scanning optical microscope (SOM). The first two are light-induced voltage alteration (LIVA) imaging techniques that (1) localize open-circuited and damaged junctions and (2) image transistor logic states. The third technique uses the SOM to control logic states optically from the IC backside. LIVA images are produced by monitoring the voltage fluctuations of a constant current power supply as a laser beam is scanned over the IC. High selectivity for localizing defects has been demonstrated using the LIVA approach. Logic state mapping results, similar to previous work using biased optical beam induced current (OBIC) and laser probing approaches have also been produced using LIVA. Application of the two LIVA based techniques to backside failure analysis has been demonstrated using an infrared laser source. Optical logic state control is based upon earlier work examining transistor response to photon injection. The physics of each method and their applications for failure analysis are described.

  9. Probing plasmons in three dimensions in a scanning transmission electron microscope

    NASA Astrophysics Data System (ADS)

    Hachtel, Jordan; Mouti, Anas; Mayo, Daniel; Marvinney, Claire; Mu, Richard; Haglund, Richard; Pennycook, Stephen; Chisholm, Matthew; Pantelides, Sokrates

    2015-03-01

    The optical behavior of nanostructured materials is of significant interest across many fields. Surface plasmons and their interactions with emitters in nanoscale devices allow us to control light below the coherence limit. By understanding the nature of plasmonics at the local level we can move towards unlocking the full potential of photonic devices. To this end, we examine plasmonic Ag nanoparticles suspended on insulating nanowires by combining cathodoluminescence spectroscopy, electron energy loss spectroscopy, and high resolution annular dark field imaging in a scanning transmission electron microscope. The complementary nature of CL and EELS allow us to extract optical data from a randomly shaped and oriented nanoparticle, and understand its plasmonic behavior in all three spatial dimensions. This work was sponsored by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division, as well as NSF-EPS-1004083 and NSF-TN-SCORE.

  10. Design and testing of prototype handheld scanning probes for optical coherence tomography.

    PubMed

    Demian, Dorin; Duma, Virgil-Florin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-08-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic-for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat-in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated. PMID:25107512

  11. Design and testing of prototype handheld scanning probes for optical coherence tomography

    PubMed Central

    Demian, Dorin; Sinescu, Cosmin; Negrutiu, Meda Lavinia; Cernat, Ramona; Topala, Florin Ionel; Hutiu, Gheorghe; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-01-01

    Three simple and low-cost configurations of handheld scanning probes for optical coherence tomography have been developed. Their design and testing for dentistry applications are presented. The first two configurations were built exclusively from available off-the-shelf optomechanical components, which, to the best of our knowledge, are the first designs of this type. The third configuration includes these components in an optimized and ergonomic probe. All the designs are presented in detail to allow for their duplication in any laboratory with a minimum effort, for applications that range from educational to high-end clinical investigations. Requirements that have to be fulfilled to achieve configurations which are reliable, ergonomic—for clinical environments, and easy to build are presented. While a range of applications is possible for the prototypes developed, in this study the handheld probes are tested ex vivo with a spectral domain optical coherence tomography system built in-house, for dental constructs. A previous testing with a swept source optical coherence tomography system has also been performed both in vivo and ex vivo for ear, nose, and throat—in a medical environment. The applications use the capability of optical coherence tomography to achieve real-time, high-resolution, non-contact, and non-destructive interferometric investigations with micrometer resolutions and millimeter penetration depth inside the sample. In this study, testing the quality of the material of one of the most used types of dental prosthesis, metalo-ceramic is thus demonstrated. PMID:25107512

  12. Scanning thermo-ionic microscopy for probing local electrochemistry at the nanoscale

    NASA Astrophysics Data System (ADS)

    Eshghinejad, Ahmadreza; Nasr Esfahani, Ehsan; Wang, Peiqi; Xie, Shuhong; Geary, Timothy C.; Adler, Stuart B.; Li, Jiangyu

    2016-05-01

    Conventional electrochemical characterization techniques based on voltage and current measurements only probe faradaic and capacitive rates in aggregate. In this work we develop a scanning thermo-ionic microscopy (STIM) to probe local electrochemistry at the nanoscale, based on imaging of Vegard strain induced by thermal oscillation. It is demonstrated from both theoretical analysis and experimental validation that the second harmonic response of thermally induced cantilever vibration, associated with thermal expansion, is present in all solids, whereas the fourth harmonic response, caused by local transport of mobile species, is only present in ionic materials. The origin of STIM response is further confirmed by its reduced amplitude with respect to increased contact force, due to the coupling of stress to concentration of ionic species and/or electronic defects. The technique has been applied to probe Sm-doped Ceria and LiFePO4, both of which exhibit higher concentrations of mobile species near grain boundaries. The STIM gives us a powerful method to study local electrochemistry with high sensitivity and spatial resolution for a wide range of ionic systems, as well as ability to map local thermomechanical response.

  13. Technique for real-time tissue characterization based on scanning multispectral fluorescence lifetime spectroscopy (ms-TRFS)

    PubMed Central

    Ma, Dinglong; Bec, Julien; Gorpas, Dimitris; Yankelevich, Diego; Marcu, Laura

    2015-01-01

    We report a novel technique for continuous acquisition, processing and display of fluorescence lifetimes enabling real-time tissue diagnosis through a single hand held or biopsy fiber-optic probe. A scanning multispectral time-resolved fluorescence spectroscopy (ms-TRFS) with self-adjustable photon detection range was developed to account for the dynamic changes of fluorescence intensity typically encountered in clinical application. A fast algorithm was implemented in the ms-TRFS software platform, providing up to 15 Hz continuous display of fluorescence lifetime values. Potential applications of this technique, including biopsy guidance, and surgical margins delineation were demonstrated in proof-of-concept experiments. Current results showed accurate display of fluorescence lifetimes values and discrimination of distinct fluorescence markers and tissue types in real-time (< 100 ms per data point). PMID:25798320

  14. Probing deeper by hard x-ray photoelectron spectroscopy

    SciTech Connect

    Risterucci, P.; Renault, O. Martinez, E.; Delaye, V.; Detlefs, B.; Zegenhagen, J.; Gaumer, C.; Grenet, G.; Tougaard, S.

    2014-02-03

    We report an hard x-ray photoelectron spectroscopy method combining high excitation energy (15 keV) and improved modelling of the core-level energy loss features. It provides depth distribution of deeply buried layers with very high sensitivity. We show that a conventional approach relying on intensities of the core-level peaks is unreliable due to intense plasmon losses. We reliably determine the depth distribution of 1 ML La in a high-κ/metal gate stack capped with 50 nm a-Si. The method extends the sensitivity of photoelectron spectroscopy to depths beyond 50 nm.

  15. Screening properties of graphene layers studied by Kelvin Probe Force Microscopy and Landau Level Spectroscopy

    NASA Astrophysics Data System (ADS)

    Vetick, John; Lu, Chih-Pin; Altvater, Michael; Duan, Junxi; Li, Guohong; Andrei, Eva Y.

    2015-03-01

    Graphene is one of the best conductors known, but due to its two dimensional structure and the need to support it on insulating substrates, its electronic properties are often masked by substrate-induced random potential fluctuations. In order to realize graphene's full potential for electronic application it is therefore important to understand its screening properties and to find ways to minimize substrate invasiveness. We employed Kelvin Probe Force microscopy (KPFM) to investigate the screening properties of CVD grown graphene crystals as a function of layer number and substrate material using a gated device geometry. The KPFM study was complemented by low temperature scanning tunneling microscopy and Landau level spectroscopy in similar samples and device configurations. Measurements were carried out on single layer, bilayer, trilayer and twisted bilayer samples deposited on SiO2 and hBN substrates. Our findings show that twisted graphene layers provide superior screening of charged impurities and random potentials while at the same time preserving the unique electronic band structure of single layer graphene. Work Supported by DOE-FG02-99ER45742 and NSF DMR 1207108.

  16. Thermodynamics of nanodomain formation and breakdown in Scanning Probe Microscopy: Landau-Ginzburg-Devonshire approach

    SciTech Connect

    Morozovska, Anna N.; Eliseev, Eugene A.; Li, Yulan; Svechnikov, Sergei V.; Maksymovych, Peter; Shur, V. Y.; Gopalan, Venkatraman; Chen , L.Q.; Kalinin, Sergei V.

    2009-12-01

    Thermodynamics of tip-induced nanodomain formation in scanning probe microscopy of ferroelectric films and crystals is studied using the analytical Landau-Ginzburg-Devonshire approach and phase-field modeling. The local redistribution of polarization induced by the biased probe apex is analyzed including the effects of polarization gradients, field dependence of dielectric properties, intrinsic domain-wall width, and film thickness. The polarization distribution inside a 'subcritical' nucleus of the domain preceding the nucleation event is shown to be 'soft' (i.e., smooth without domain walls) and localized below the probe, and the electrostatic field distribution is dominated by the tip. In contrast, polarization distribution inside a stable domain is 'hard' (i.e., sharp contrast with delineated domain walls) and the spontaneous polarization reorientation takes place inside a localized spatial region, where the absolute value of the resulting electric field is larger than the thermodynamic coercive field. The calculated coercive biases corresponding to formation of switched domains are in a good agreement with available experimental results for typical ferroelectric materials. The microscopic origin of the observed domain-tip elongation in the region where the probe electric field is much smaller than the intrinsic coercive field is the positive depolarization field in front of the moving-counter domain wall. For infinitely thin domain wall the depolarization field outside the semiellipsoidal domain tip is always higher than the intrinsic coercive field that must initiate the local domain breakdown through the sample depth while the domain length is finite in the energetic approach evolved by Landauer and Molotskii (we refer the phenomenon as Landauer-Molotskii paradox). Our approach provides the solution of the paradox: the domain vertical growth should be accompanied by the increase in the charged domain-wall width.

  17. Thermodynamics of nanodomain formation and breakdown in Scanning Probe Microscopy: Landau-Ginzburg-Devonshire approach

    SciTech Connect

    Morozovska, A. N.; Eliseev, E. A.; Li, Yulan; Svechnikov, S. V.; Maksymovych, Petro; Gopalana, V.; Chen, Long-Qing; Kalinin, Sergei V

    2009-01-01

    Thermodynamics of tip-induced nanodomain formation in scanning probe microscopy of ferroelectric films and crystals is studied using the analytical Landau-Ginzburg-Devonshire approach and phase-field modeling. The local redistribution of polarization induced by the biased probe apex is analyzed including the effects of polarization gradients, field dependence of dielectric properties, intrinsic domain wall width, and film thickness. The polarization distribution inside a subcritical nucleus of the domain preceding the nucleation event is shown to be soft (i.e. smooth without domain walls) and localized below the probe, and the electrostatic field distribution is dominated by the tip. In contrast, polarization distribution inside a stable domain is hard (i.e. sharp contrast with delineated domain walls) and the spontaneous polarization reorientation takes place inside a localized spatial region, where the absolute value of the resulting electric field is larger than the thermodynamic coercive field. The calculated coercive biases corresponding to formation of switched domains are in a good agreement with available experimental results for typical ferroelectric materials. The microscopic origin of the observed domain tip elongation in the region where the probe electric field is much smaller than the intrinsic coercive field is the positive depolarization field in front of the moving counter domain wall. For infinitely thin domain wall the depolarization field outside the semi-ellipsoidal domain tip is always higher than the intrinsic coercive field that must initiate the local domain breakdown through the sample depth, while the domain length is finite in the energetic approach evolved by Landauer and Molotskii (we refer the phenomenon as Landauer-Molotskii paradox). Our approach provides the solution of the paradox: the domain vertical growth should be accompanied by the increase of the charged domain wall width.

  18. An exchangeable-tip scanning probe instrument for the analysis of combinatorial libraries of electrocatalysts

    NASA Astrophysics Data System (ADS)

    Rus, Eric D.; Wang, Hongsen; Legard, Anna E.; Ritzert, Nicole L.; Bruce Van Dover, Robert; Abruña, Héctor D.

    2013-02-01

    A combined scanning differential electrochemical mass spectrometer (SDEMS)-scanning electrochemical microscope (SECM) apparatus is described. The SDEMS is used to detect and spatially resolve volatile electrochemically generated species at the surface of a substrate electrode. The SECM can electrochemically probe the reactivity of the surface and also offers a convenient means of leveling the sample. It is possible to switch between these two different scanning tips and techniques without moving the sample and while maintaining potential control of the substrate electrode. A procedure for calibration of the SDEMS tip-substrate separation, based upon the transit time of electrogenerated species from the substrate to the tip is also described. This instrument can be used in the characterization of combinatorial libraries of direct alcohol fuel cell anode catalysts. The apparatus was used to analyze the products of methanol oxidation at a Pt substrate, with the SDEMS detecting carbon dioxide and methyl formate, and a PtPb-modified Pt SECM tip used for the selective detection of formic acid. As an example system, the electrocatalytic methanol oxidation activity of a sputter-deposited binary PtRu composition spread in acidic media was analyzed using the SDEMS. These results are compared with those obtained from a pH-sensitive fluorescence assay.

  19. 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.

  20. Demonstration of parallel scanning probe microscope for high throughput metrology and inspection

    NASA Astrophysics Data System (ADS)

    Sadeghian, Hamed; Dekker, Bert; Herfst, Rodolf; Winters, Jasper; Eigenraam, Alexander; Rijnbeek, Ramon; Nulkes, Nicole

    2015-03-01

    With the device dimensions moving towards the 1X node and below, the semiconductor industry is rapidly approaching the point where existing metrology, inspection and review tools face huge challenges in terms of resolution, the ability to resolve 3D and the throughput. Due to the advantages of sub-nanometer resolution and the ability of true 3D scanning, scanning probe microscope (SPM) and specifically atomic force microscope (AFM) are considered as alternative technologies for CD-metrology, defect inspection and review of 1X node and below. In order to meet the increasing demand for resolution and throughput of CD-metrology, defect inspection and review, TNO has previously introduced the parallel SPM concept, consisting of parallel operation of many miniaturized SPMs on a 300 and 450 mm wafer. In this paper we will present the proof of principle of the parallelization for metrology and inspection. To give an indication of the system's specifications, the throughput of scanning is 4500 sites per hour, each within an area of 1 μm2 and 1024 ×1024 pixels.

  1. An exchangeable-tip scanning probe instrument for the analysis of combinatorial libraries of electrocatalysts.

    PubMed

    Rus, Eric D; Wang, Hongsen; Legard, Anna E; Ritzert, Nicole L; Van Dover, Robert Bruce; Abruña, Héctor D

    2013-02-01

    A combined scanning differential electrochemical mass spectrometer (SDEMS)-scanning electrochemical microscope (SECM) apparatus is described. The SDEMS is used to detect and spatially resolve volatile electrochemically generated species at the surface of a substrate electrode. The SECM can electrochemically probe the reactivity of the surface and also offers a convenient means of leveling the sample. It is possible to switch between these two different scanning tips and techniques without moving the sample and while maintaining potential control of the substrate electrode. A procedure for calibration of the SDEMS tip-substrate separation, based upon the transit time of electrogenerated species from the substrate to the tip is also described. This instrument can be used in the characterization of combinatorial libraries of direct alcohol fuel cell anode catalysts. The apparatus was used to analyze the products of methanol oxidation at a Pt substrate, with the SDEMS detecting carbon dioxide and methyl formate, and a PtPb-modified Pt SECM tip used for the selective detection of formic acid. As an example system, the electrocatalytic methanol oxidation activity of a sputter-deposited binary PtRu composition spread in acidic media was analyzed using the SDEMS. These results are compared with those obtained from a pH-sensitive fluorescence assay. PMID:23464226

  2. Scanning Ultrasonic Spectroscopy System Developed for the Inspection of Composite Flywheels

    NASA Technical Reports Server (NTRS)

    Martin, Richard E.; Baaklini, George Y.

    2002-01-01

    Composite flywheels are being considered as replacements for chemical batteries aboard the International Space Station. A flywheel stores energy in a spinning mass that can turn a generator to meet power demands. Because of the high rotational speeds of the spinning mass, extensive testing of the flywheel system must be performed prior to flight certification. With this goal in mind, a new scanning system has been developed at the NASA Glenn Research Center for the nondestructive inspection of composite flywheels and flywheel subcomponents. The system uses ultrasonic waves to excite a material and examines the response to detect and locate flaws and material variations. The ultrasonic spectroscopy system uses a transducer to send swept-frequency ultrasonic waves into a test material and then receives the returning signal with a second transducer. The received signal is then analyzed in the frequency domain using a fast Fourier transform. A second fast Fourier transform is performed to examine the spacing of the peaks in the frequency domain. The spacing of the peaks is related to the standing wave resonances that are present in the material because of the constructive and destructive interferences of the waves in the full material thickness as well as in individual layers within the material. Material variations and flaws are then identified by changes in the amplitudes and positions of the peaks in both the frequency and resonance spacing domains. This work, conducted under a grant through the Cleveland State University, extends the capabilities of an existing point-by-point ultrasonic spectroscopy system, thus allowing full-field automated inspection. Results of an ultrasonic spectroscopy scan of a plastic cylinder with intentionally seeded flaws. The result of an ultrasonic spectroscopy scan of a plastic cylinder used as a proof-of-concept specimen is shown. The cylinder contains a number of flat bottomed holes of various sizes and shapes. The scanning system

  3. Transmission pump-probe spectroscopy on multilayer black phosphorus

    NASA Astrophysics Data System (ADS)

    Suess, Ryan J.; Jadidi, Mohammad M.; Murphy, Thomas E.; Mittendorff, Martin

    Black phosphorus is a two-dimensional material that has recently attracted interest due to its high mobility and direct bandgap. In this work we examine the pump-induced change in optical transmission of mechanically exfoliated black phosphorus flakes using a two-color optical pump-probe measurement. The time-resolved data reveal a fast pump-induced transparency accompanied by a slower absorption that we attribute to Pauli blocking and free-carrier absorption, respectively. Polarization studies show that these effects are also highly anisotropic - underscoring the importance of crystal orientation in the design of optical devices based on this material. Ongoing work suggests that exploring the carrier density dependence of the pump-probe signals, which can be accessed experimentally via electrostatic gating, may allow for improved understanding of the optical response and carrier dynamics in the material. Supported by NSF and ONR-MURI.

  4. Hollow cathode theory and experiment. I. Plasma characterization using fast miniature scanning probes

    SciTech Connect

    Goebel, Dan M.; Jameson, Kristina K.; Watkins, Ron M.; Katz, Ira; Mikellides, Ioannis G.

    2005-12-01

    A detailed study of the spatial variation of plasma density, temperature, and potential in hollow cathodes using miniature fast scanning probes has been undertaken in order to better understand the cathode operation and to provide benchmark data for the modeling of the cathode performance and life described in a companion paper. Profiles are obtained throughout the discharge and in the very high-density orifice region by pneumatically driven Langmuir probes, which are inserted directly into the hollow cathode orifice from either the upstream insert region inside the hollow cathode or from the downstream anode-plasma region. A fast transverse-scanning probe is also used to provide radial profiles of the cathode plume as a function of position from the cathode exit. The probes are extremely small to avoid perturbing the plasma; the ceramic tube insulator is 0.05 cm in diameter with a probe tip area of 0.002 cm{sup 2}. A series of current-voltage characteristics are obtained by applying a rapid sawtooth voltage wave form to the probe as it is scanned through the plasma at speeds of up to 2 m/s to produce the profiles with a spatial resolution of about 0.05 cm. At discharge currents of 10-25 A from the 1.5-cm-diameter hollow cathode, the plasma density inside the cathode is found to exceed 10{sup 14} cm{sup -3}, with the peak density occurring upstream of the orifice. The plasma potentials on axis inside the cathode are found to be in the 10-20 V range with electron temperatures of 2-5 eV, depending on the discharge current and gas flow rate. A potential discontinuity or double layer of less than 10 V is observed in the orifice region, and under certain conditions appears in the bright 'plasma ball' in front of the cathode. This structure tends to change location and magnitude with discharge current, gas flow, and orifice size. A potential maximum proposed in the literature to exist in or near the cathode orifice is not observed. Instead, the plasma potential increases

  5. Probing vibrational anisotropy with nuclear resonance vibrational spectroscopy.

    SciTech Connect

    Pavlik, J. W.; Barabanschikov, A.; Oliver, A. G.; Alp, E. E.; Sturhahn, W.; Zhao, J.; Sage, J. T.; Scheidt, W. R.

    2010-06-14

    A NRVS single-crystal study (NRVS=nuclear resonance vibrational spectroscopy) has provided detailed information on the in-plane modes of nitrosyl iron porphyrinate [Fe(oep)(NO)] (see picture; oep=octaethylporphyrin). The axial nitrosyl ligand controls the direction of the in-plane iron motion.

  6. NMR difference spectroscopy with a dual saddle-coil difference probe.

    PubMed

    Macnaughtan, Megan A; Smith, Aaron P; Goldsbrough, Peter B; Santini, Robert E; Raftery, Daniel

    2004-03-01

    A new difference probe for nuclear magnetic resonance (NMR) spectroscopy is presented. The difference probe uses two saddle-shaped coils to excite and detect two samples simultaneously. The samples are held in a specially modified 3-mm NMR tube with an Ultem plastic disk to separate the samples. The probe's resonant circuit contains two crossed diodes that passively switch the relative phase of each coil during the NMR experiment. The result is a difference spectrum from the two samples. The degree of cancellation of common signals was determined to be approximately 90%, and the application of the probe to relaxation-edited difference spectroscopy for identifying protein-ligand interactions was demonstrated using glutathione and glutathione S-transferase binding protein. PMID:15214412

  7. Pump-Probe Spectroscopy of Two-Body Correlations in Ultracold Gases

    SciTech Connect

    Koch, Christiane P.; Kosloff, Ronnie

    2009-12-31

    We suggest pump-probe spectroscopy to study pair correlations that determine the many-body dynamics in weakly interacting, dilute ultracold gases. A suitably chosen, short laser pulse depletes the pair density locally, creating a 'hole' in the electronic ground state. The dynamics of this nonstationary pair density is monitored by a time-delayed probe pulse. The resulting transient signal allows us to spectrally decompose the hole and to map out the pair correlation function.

  8. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    DOE PAGESBeta

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-24

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. Here we present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  9. Aberrated electron probes for magnetic spectroscopy with atomic resolution: Theory and practical aspects

    NASA Astrophysics Data System (ADS)

    Rusz, Ján; Idrobo, Juan Carlos

    2016-03-01

    It was recently proposed that electron magnetic circular dichroism can be measured in scanning transmission electron microscopy with atomic resolution by tuning the phase distribution of an electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. We present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  10. Aberrated electron probes for novel spectroscopy with atomic resolution: theory and practical aspects

    SciTech Connect

    Rusz, Jan; Idrobo Tapia, Juan Carlos

    2016-01-01

    It was recently proposed that electron magnetic circular dichroism (EMCD) can be measured in scanning transmission electron microscopy (STEM) with atomic resolution by tuning the phase distribution of a electron beam. Here, we describe the theoretical and practical aspects for the detection of out-of-plane and in-plane magnetization utilizing atomic size electron probes. We present the calculated optimized astigmatic probes and discuss how to achieve them experimentally.

  11. Characterization of Antisticking Layers for UV Nanoimprint Lithography Molds with Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Kurihara, Masaaki; Hatakeyama, Sho; Yamada, Noriko; Shimomura, Takeya; Nagai, Takaharu; Yoshida, Kouji; Tomita, Tatsuya; Hoga, Morihisa; Hayashi, Naoya; Ohtani, Hiroyuki; Fujihira, Masamichi

    2010-06-01

    Antisticking layers (ASLs) on UV nanoimprint lithography (UV-NIL) molds were characterized by scanning probe microscopies (SPMs) in addition to macroscopic analyses of work of adhesion and separation force. Local physical properties of the ASLs were measured by atomic force microscopy (AFM) and friction force microscopy (FFM). The behavior of local adhesive forces measured with AFM on several surfaces was consistent with that of work of adhesion obtained from contact angle. The ASLs were coated by two different processes, i.e., one is a vapor-phase process and the other a spin-coating process. The homogeneity of the ASLs prepared by the vapor-phase process was better than that of those prepared by the spin-coating process. In addition, we measured the thicknesses of ASL patterns prepared by a lift-off method to investigate the effect of the ASL thicknesses on critical dimensions of the molds with ASLs and found that this effect is not negligible.

  12. Scanning Probe Microscopy for Identifying the Component Materials of a Nanostripe Structure

    NASA Astrophysics Data System (ADS)

    Mizuno, Akira; Ando, Yasuhisa

    2010-08-01

    The authors prepared a nanostripe structure in which two types of metal are arranged alternately, and successfully identified the component materials using scanning probe microscopy (SPM) to measure the lateral force distribution image. The nanostripe structure was prepared using a new method developed by the authors and joint development members. The lateral force distribution image was measured in both friction force microscopy (FFM) and lateral modulation friction force microscopy (LM-FFM) modes. In FFM mode, the effect of slope angle appeared in the lateral force distribution image; therefore, no difference in the type of material was observed. On the other hand, in LM-FFM mode, the effect of surface curvature was observed in the lateral force distribution image. A higher friction force on chromium than on gold was identified, enabling material identification.

  13. High-precision calibration of a Scanning-Probe Microscope (SPM) for manufacturing applications

    SciTech Connect

    Chernoff, D.A.; Lohr, J.D.; Hansen, D.; Lines, M.

    1996-12-31

    For ordinary SPM (Scanning Probe Microscope) work, accuracy of XYZ length measurements of about 5% is acceptable. This is accomplished by periodic calibration checks (and adjustments, if required). Measurement of critical dimensions such as feature width and spacing on integrated circuits of compact discs requires much higher accuracy. For example, the new DVD (digital video disc) standard calls for a mean track pitch of 740 nm with a maximum allowable jitter (range) of 30 nm. To achieve a range of 30 nm, the standard deviation should be 10 nm or less. According to the gage-maker`s rule, the measurement tool should be 4x more precise than the object being measured, so we need a standard deviation of 2.5 nm. This report describes the combined use of a new type of calibration standard and new software to meet these requirements.

  14. Towards quantitative electrochemical measurements on the nanoscale by scanning probe microscopy: environmental and current spreading effects

    SciTech Connect

    Arruda, Thomas M; Kumar, Amit; Veith, Gabriel M; Jesse, Stephen; Tselev, Alexander; Baddorf, Arthur P; Balke, Nina; Kalinin, Sergei V

    2013-01-01

    The application of electric bias across tip-surface junctions in scanning probe microscopy can readily induce surface and bulk electrochemical processes that can be further detected though changes in surface topography, Faradaic or conductive currents, or electromechanical strain responses. However, the basic factors controlling tip-induced electrochemical processes, including the relationship between applied tip bias and the thermodynamics of local processes remains largely unexplored. Using the model Li-ion reduction reaction on the surface in Li-ion conducting glass ceramic, we explore the factors controlling Li-metal formation and find surprisingly strong effects of atmosphere and back electrode composition on the process. These studies suggest the feasibility of SPM-based quantitative electrochemical studies under proper environmental controls, extending the concepts of ultramicroelectrodes to the single-digit nanometer scale.

  15. Fabrication of sub-12 nm thick silicon nanowires by processing scanning probe lithography masks

    SciTech Connect

    Kyoung Ryu, Yu; Garcia, Ricardo; Aitor Postigo, Pablo; Garcia, Fernando

    2014-06-02

    Silicon nanowires are key elements to fabricate very sensitive mechanical and electronic devices. We provide a method to fabricate sub-12 nm silicon nanowires in thickness by combining oxidation scanning probe lithography and anisotropic dry etching. Extremely thin oxide masks (0.3–1.1 nm) are transferred into nanowires of 2–12 nm in thickness. The width ratio between the mask and the silicon nanowire is close to one which implies that the nanowire width is controlled by the feature size of the nanolithography. This method enables the fabrication of very small single silicon nanowires with cross-sections below 100 nm{sup 2}. Those values are the smallest obtained with a top-down lithography method.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  17. Scanning probe acoustic microscopy of extruded starch materials: direct visual evidence of starch crystal.

    PubMed

    Liu, Zhongdong; Liu, Boxiang; Li, Mengxing; Wei, Min; Li, Hua; Liu, Peng; Wan, Tuo

    2013-10-15

    Scanning probe acoustic microscopy (SPAM) has been successfully used to study inorganic and keratin biomaterials. However, few studies have attempted to apply SPAM to structural study of non-keratin organic materials such as starch based materials. This study investigated hardness and surface finish to establish sample preparation method suitable for SPAM imaging and acquired clear acoustic images of extruded starch materials. Acquired acoustic images directly exhibited certain structure of starch materials and provided visual evidence of starch material components and aggregates. In addition, through correlating acoustic images with X-ray diffraction data, crystal-structural information in nano-scale was obtained and acoustic image contrast showed a linear relationship with starch amylose content in extruded starch materials. PMID:23987357

  18. Friedel oscillations in graphene-based systems probed by Scanning Tunneling Microscopy

    NASA Astrophysics Data System (ADS)

    Mallet, Pierre; Brihuega, Iván; Cherkez, Vladimir; Gómez-Rodríguez, Jose Marìa; Veuillen, Jean-Yves

    2016-03-01

    For the last 25 years, scientists have demonstrated the capabilities of Scanning Tunneling Microscopy (STM) to visualize in real space the response of a two-dimensional electron gas to atomic-scale impurities. The analysis of the Friedel oscillations surrounding the impurities yields valuable information regarding the elastic scattering properties, the band structure, the doping level and the symmetry of the electronic states in the two-dimensional host system. We will address in this article the use of this technique for probing the electronic properties of graphene, the star two-dimensional compound of the last decade. In particular, we will emphasize how this technique can be pushed up to unravel the electronic pseudospin, a distinctive degree of freedom of graphene's Dirac fermions. xml:lang="fr"

  19. Three-Dimensional Nanoprinting via Scanning Probe Lithography-Delivered Layer-by-Layer Deposition.

    PubMed

    Zhao, Jianli; Swartz, Logan A; Lin, Wei-Feng; Schlenoff, Philip S; Frommer, Jane; Schlenoff, Joseph B; Liu, Gang-Yu

    2016-06-28

    Three-dimensional (3D) printing has been a very active area of research and development due to its capability to produce 3D objects by design. Miniaturization and improvement of spatial resolution are major challenges in current 3D printing technology development. This work reports advances in miniaturizing 3D printing to the nanometer scale using scanning probe microscopy in conjunction with local material delivery. Using polyelectrolyte polymers and complexes, we have demonstrated the concept of layer-by-layer nanoprinting by design. Nanometer precision is achieved in all three dimensions, as well as in interlayer registry. The approach enables production of designed functional 3D materials with nanometer resolution and, as such, creates a platform for conducting scientific research in designed 3D nanoenvironments as well. In doing so, it enables production of nanomaterials and scaffolds for photonics devices, biomedicine, and tissue engineering. PMID:27203853

  20. Quantitative characterization of crosstalk effects for friction force microscopy with scan-by-probe SPMs.

    PubMed

    Prunici, Pavel; Hess, Peter

    2008-06-01

    If the photodetector and cantilever of an atomic force microscope (AFM) are not properly adjusted, crosstalk effects will appear. These effects disturb measurements of the absolute vertical and horizontal cantilever deflections, which are involved in friction force microscopy (FFM). A straightforward procedure is proposed to study quantitatively crosstalk effects observed in scan-by-probe SPMs. The advantage of this simple, fast, and accurate procedure is that no hardware change or upgrade is needed. The results indicate that crosstalk effects depend not only on the alignment of the detector but also on the cantilever properties, position, and detection conditions. The measurements may provide information on the origin of the crosstalk effect. After determination of its magnitude, simple correction formulas can be applied to correct the crosstalk effects and then the single-load wedge method, using a commercially available grating, can be employed for accurate calibration of the lateral force. PMID:18035500

  1. Scanning Hall probe measurements of field distributions of a coated conductor under applied fields

    NASA Astrophysics Data System (ADS)

    Yoo, Jaeun; Jung, Yonghwan; Lee, Jaeyoung; Lim, Sunme; Moo Lee, Sang; Jung, Ye Hyun; Youm, Dojun; Kim, Hosup; Ha, Hong Soo; Oh, Sangsoo

    2006-12-01

    We measured the field profiles near the surface of a coated conductor (CC) under various applied fields by using the scanning Hall probe method. The field, applied in the normal direction, was increased from zero to 171.5 Oe and then decreased to -58.8 Oe. We could not analyse our data completely by the direct use of Brandt's calculation but by a modification with unusual field dependences of the introduced parameters. Since Brandt's original calculation was based on homogeneous films, it was not suitable for CCs with coarse granular structures. The modified calculations with appropriate parameters are related to the coarse granular structures. Those parameters, D, Jc, and R, represent the three characteristics of the flux penetration network: the average distance of flux penetrations, the density of critical sheet currents, and the range of meandering of the flux penetration front, respectively. The external field dependences of these parameters were different from those of the classical critical state model.

  2. Chemical-contrast imaging with pulse-shaping based pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Flynn, Daniel C.; Bhagwat, Amar R.; Ogilvie, Jennifer P.

    2013-02-01

    Ultrafast pump-probe spectroscopy and pulse-shaping techniques are providing new modes of contrast for the field of multiphoton microscopy. Endogenous species such as heme proteins show rich nonlinear spectroscopic signatures of excited state absorption, stimulated emission and ground-state bleaching. Commercially available octave-spanning Ti:sapphire oscillators offer new opportunities for imaging based on pump-probe contrast. Spatial light modulators take advantage of this large bandwidth, shaping pulses of light to selectively excite molecular structures with similar spectral properties. We present two-color pump-probe imaging of heme proteins solutions and red blood cells.

  3. [Comparison of the M and XL FibroScan(®) probes to estimate liver stiffness by transient elastography].

    PubMed

    Herrero, José Ignacio; Iñarrairaegui, Mercedes; D'Avola, Delia; Sangro, Bruno; Prieto, Jesús; Quiroga, Jorge

    2014-04-01

    The FibroScan(®) XL probe has been specifically designed for obese patients to measure liver stiffness by transient elastography, but it has not been well tested in non-obese patients. The aim of this study was to compare the M and XL FibroScan(®) probes in a series of unselected obese (body mass index above 30 kg/m(2)) and non-obese patients with chronic liver disease. Two hundred and fifty-four patients underwent a transient elastography examination with both the M and XL probes. The results obtained with the two probes were compared in the whole series and in obese (n=82) and non-obese (n=167) patients separately. The reliability of the examinations was assessed using the criteria defined by Castéra et al. The proportion of reliable exams was significantly higher when the XL probe was used (83% versus 73%; P=.001). This significance was maintained in the group of obese patients (82% versus 55%; P<.001), but not in the non-obese patients (84% versus 83%). Despite a high correlation between the stiffness values obtained with the two probes (R=.897; P<.001), and a high concordance in the estimation of fibrosis obtained with the two probes (Cronbach's alpha value: 0.932), the liver stiffness values obtained with the XL probe were significantly lower than those obtained with the M probe, both in the whole series (9.5 ± 9.1 kPa versus 11.3 ± 12.6 kPa; P<0.001) and in the obese and non-obese groups. In conclusion, transient elastography with the XL probe allows a higher proportion of reliable examinations in obese patients but not in non-obese patients. Stiffness values were lower with the XL probe than with the M probe. PMID:24417906

  4. An evaluation of a combined scanning probe and optical microscope for lunar regolith studies

    NASA Astrophysics Data System (ADS)

    Yang, S.; Pike, W. T.; Staufer, U.; Claus, D.; Rodenburg, J. M.

    2011-12-01

    The microscopic properties of the lunar regolith such as the shape, the surface texture and the size distribution are required for an understanding of both past surface processes and potential hazards for future human exploration [1]. To reveal the particle morphology at the sub micrometer scale, scanning-probe microscopy (SPM), first used on the 2008 Phoenix mission [1], is a proven approach; however, there are two main challenges for the measurement of lunar particles. Firstly, the SPM tip is liable to move particles during scanning, even when using the lower contact forces of the dynamic-mode imaging. Hence the particles need to be stabilised during imaging. Secondly, typically the AFM tip extends about 10 μm from its cantilever, so larger particles protruding more than this height above their substrates cannot be scanned completely. To immobilize particles and eliminate large particles during SPM scanning, micromachined Si substrates, which have been successfully applied in the Phoenix project for Mars investigation in 2008 [2], have been investigated for lunar analogue material. On these substrates micrometer pits are patterned and serve as traps to enhance the stability of the AFM scanning by grasping the particles. In addition, the diameter of pits can determine the size of dusts to be captured and reduce the adhesion for the larger dust and so eliminate the oversized particles. To extend the imaging range and assist in selecting scan areas for the SPM, we use a type of lensless optical imaging (LOM) which uses ptychographic diffractive imaging [3] to eliminate the restrictions and performance limitations of conventional focusing devices. As a reference, scanning electron microscopy (SEM) which minimizes particle-probe interactions and has the advantage of an extended depth of field, is employed to image the same particle fields at resolutions covering both the SPM and LOM. By comparing the differences and the similarities between SEM and LOM images, the

  5. Surface characterization of InP trenches embedded in oxide using scanning probe microscopy

    SciTech Connect

    Mannarino, Manuel E-mail: manuelmannarino@gmail.com; Chintala, Ravi; Vandervorst, Wilfried; Moussa, Alain; Merckling, Clement; Eyben, Pierre; Paredis, Kristof

    2015-12-14

    Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III–V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III–V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP.

  6. Surface characterization of InP trenches embedded in oxide using scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Mannarino, Manuel; Chintala, Ravi; Moussa, Alain; Merckling, Clement; Eyben, Pierre; Paredis, Kristof; Vandervorst, Wilfried

    2015-12-01

    Metrology for structural and electrical analyses at device level has been identified as one of the major challenges to be resolved for the sub-14 nm technology nodes. In these advanced nodes, new high mobility semiconductors, such as III-V compounds, are grown in narrow trenches on a Si substrate. Probing the nature of the defects, the defect density, and the role of processing steps on the surface of such structures are prime metrology requirements. In order to enable defect analysis on a (III-V) surface, a proper sample preparation for oxide removal is of primary importance. In this work, the effectiveness of different chemical cleanings and thermal annealing procedures is investigated on both blanket InP and oxide embedded InP trenches by means of scanning probe microscopy techniques. It is found that the most effective approach is a combination of an HCl-based chemical cleaning combined with a low-temperature thermal annealing leading to an oxide free surface with atomically flat areas. Scanning tunneling microscopy (STM) has been the preferred method for such investigations on blanket films due to its intrinsic sub-nm spatial resolution. However, its application on oxide embedded structures is non-trivial. To perform STM on the trenches of interest (generally <20 nm wide), we propose a combination of non-contact atomic force microscopy and STM using the same conductive atomic force microscopy tip Our results prove that with these procedures, it is possible to perform STM in narrow InP trenches showing stacking faults and surface reconstruction. Significant differences in terms of roughness and terrace formation are also observed between the blanket and the oxide embedded InP.

  7. Probing DNA hybridization efficiency and single base mismatch by X-ray photoelectron spectroscopy.

    PubMed

    Liu, Zheng-Chun; Zhang, Xin; He, Nong-Yue; Lu, Zu-Hong; Chen, Zhen-Cheng

    2009-07-01

    We demonstrated the use of X-ray photoelectron spectroscopy (XPS) to study DNA hybridization. Target DNA labeled with hexachloro-fluorescein (HEX) was hybridized to DNA arrays with four different probes. Each probe dot of the hybridized arrays was detected with XPS. The XPS Cl2p peak areas were found to decrease with an increase in mismatched bases in DNA probes. The Cl2p core-level peak area ratio of a probe perfectly matched to one, two and three base-mismatched probes accorded well with the results of conventional fluorescent imaging, which shows that XPS is a potential tool for analyzing DNA arrays. The DNA arrays' hybridization efficiency was assessed by the molar ratio of chlorine to phosphorus in a DNA strand, which was determined from the relevant XPS Cl2p and P2p core-level peak areas after hybridization. This could provide a new method to detect DNA hybridization efficiency. PMID:19282155

  8. Contact transfer length investigation of a 2D nanoparticle network by scanning probe microscopy.

    PubMed

    Ruiz-Vargas, Carlos S; Reissner, Patrick A; Wagner, Tino; Wyss, Roman M; Park, Hyung Gyu; Stemmer, Andreas

    2015-09-11

    Nanoparticle network devices find growing application in sensing and electronics. One recurring challenge in the design and fabrication of this class of devices is ensuring a stable interface via robust yet unobstructive electrodes. A figure of merit which dictates the minimum electrode overlap required for optimal charge injection into the network is the contact transfer length. However, we find that traditional contact characterization using the transmission line model, an indirect method which requires extrapolation, is insufficient for network devices. Instead, we apply Kelvin probe force microscopy to characterize the contact resistance by imaging the surface potential with nanometer resolution. We then use scanning probe lithography to directly investigate the contact transfer length. We have determined the transfer length in graphene contacted devices to be 200-400 nm, thus apt for further device reduction which is often necessary for on-site sensing applications. Simulations from a two-dimensional resistor model support our observations and are expected to be an important tool for further optimizing the design of nanoparticle-based devices. PMID:26291069

  9. Quantifying charge carrier concentration in ZnO thin films by Scanning Kelvin Probe Microscopy

    PubMed Central

    Maragliano, C.; Lilliu, S.; Dahlem, M. S.; Chiesa, M.; Souier, T.; Stefancich, M.

    2014-01-01

    In the last years there has been a renewed interest for zinc oxide semiconductor, mainly triggered by its prospects in optoelectronic applications. In particular, zinc oxide thin films are being widely used for photovoltaic applications, in which the determination of the electrical conductivity is of great importance. Being an intrinsically doped material, the quantification of its doping concentration has always been challenging. Here we show how to probe the charge carrier density of zinc oxide thin films by Scanning Kelvin Probe Microscopy, a technique that allows measuring the contact potential difference between the tip and the sample surface with high spatial resolution. A simple electronic energy model is used for correlating the contact potential difference with the doping concentration in the material. Limitations of this technique are discussed in details and some experimental solutions are proposed. Two-dimensional doping concentration images acquired on radio frequency-sputtered intrinsic zinc oxide thin films with different thickness and deposited under different conditions are reported. We show that results inferred with this technique are in accordance with carrier concentration expected for zinc oxide thin films deposited under different conditions and obtained from resistivity and mobility measurements. PMID:24569599

  10. Quantitative Decoupling of Excited-State Absorption Cross Section and Population via Pump-Probe Spectroscopy with a Strong Probe

    NASA Astrophysics Data System (ADS)

    Barker, Alex J.; Hodgkiss, Justin M.

    2015-08-01

    Photoinduced absorption signals measured by transient absorption spectroscopy are typically proportional to the product of absorption cross section (σ ) and excited-state density (N ). We show that this approximation does not hold at high probe-pulse intensities, and introduce the use of probe-intensity-dependent spectroscopy to decouple the two parameters. The singlet excited-state (S1→S2) absorption cross section of the conjugated polymer F8BT is measured to be 1.6 ×10-16 cm2±40 % at 800 nm and 3.7×10 -16 cm2±30 % at 900 nm, with no variation over the time window surveyed. The robustness of these parameters is established by observing that only N scales with excitation fluence and time delay, and conversely only σ is dependent on probe wavelength. The technique may be useful for quantifying salient parameters in many systems, such as branching yields in systems exhibiting singlet fission or triplet production, or cross sections required for photophysical models.

  11. SCAN+

    SciTech Connect

    Kenneth Krebs, John Svoboda

    2009-11-01

    SCAN+ is a software application specifically designed to control the positioning of a gamma spectrometer by a two dimensional translation system above spent fuel bundles located in a sealed spent fuel cask. The gamma spectrometer collects gamma spectrum information for the purpose of spent fuel cask fuel loading verification. SCAN+ performs manual and automatic gamma spectrometer positioning functions as-well-as exercising control of the gamma spectrometer data acquisitioning functions. Cask configuration files are used to determine the positions of spent fuel bundles. Cask scanning files are used to determine the desired scan paths for scanning a spent fuel cask allowing for automatic unattended cask scanning that may take several hours.

  12. Carrier density distribution in silicon nanowires investigated by scanning thermal microscopy and Kelvin probe force microscopy.

    PubMed

    Wielgoszewski, Grzegorz; Pałetko, Piotr; Tomaszewski, Daniel; Zaborowski, Michał; Jóźwiak, Grzegorz; Kopiec, Daniel; Gotszalk, Teodor; Grabiec, Piotr

    2015-12-01

    The use of scanning thermal microscopy (SThM) and Kelvin probe force microscopy (KPFM) to investigate silicon nanowires (SiNWs) is presented. SThM allows imaging of temperature distribution at the nanoscale, while KPFM images the potential distribution with AFM-related ultra-high spatial resolution. Both techniques are therefore suitable for imaging the resistance distribution. We show results of experimental examination of dual channel n-type SiNWs with channel width of 100 nm, while the channel was open and current was flowing through the SiNW. To investigate the carrier distribution in the SiNWs we performed SThM and KPFM scans. The SThM results showed non-symmetrical temperature distribution along the SiNWs with temperature maximum shifted towards the contact of higher potential. These results corresponded to those expressed by the distribution of potential gradient along the SiNWs, obtained using the KPFM method. Consequently, non-uniform distribution of resistance was shown, being a result of non-uniform carrier density distribution in the structure and showing the pinch-off effect. Last but not least, the results were also compared with results of finite-element method modeling. PMID:26381074

  13. Magnetic scanning gate microscopy of a domain wall nanosensor using microparticle probe

    NASA Astrophysics Data System (ADS)

    Corte-León, H.; Gribkov, B.; Krzysteczko, P.; Marchi, F.; Motte, J.-F.; Schumacher, H. W.; Antonov, V.; Kazakova, O.

    2016-02-01

    We apply the magnetic scanning gate microscopy (SGM) technique to study the interaction between a magnetic bead (MB) and a domain wall (DW) trapped in an L-shaped magnetic nanostructure. Magnetic SGM is performed using a custom-made probe, comprising a hard magnetic NdFeB bead of diameter 1.6 μm attached to a standard silicon tip. The MB-DW interaction is detected by measuring changes in the electrical resistance of the device as a function of the tip position. By scanning at different heights, we create a 3D map of the MB-DW interaction and extract the sensing volume for different widths of the nanostructure's arms. It is shown that for 50 nm wide devices the sensing volume is a cone of 880 nm in diameter by 1.4 μm in height, and reduces down to 800 nm in height for 100 nm devices with almost no change in its diameter.

  14. New ultrarapid-scanning interferometer for FT-IR spectroscopy with microsecond time-resolution.

    PubMed

    Süss, B; Ringleb, F; Heberle, J

    2016-06-01

    A novel Fourier-transform infrared (FT-IR) rapid-scan spectrometer has been developed (patent pending EP14194520.4) which yields 1000 times higher time resolution as compared to conventional rapid-scanning spectrometers. The central element to achieve faster scanning rates is based on a sonotrode whose front face represents the movable mirror of the interferometer. A prototype spectrometer with a time resolution of 13 μs was realized, capable of fully automated long-term measurements with a flow cell for liquid samples, here a photosynthetic membrane protein in solution. The performance of this novel spectrometer is demonstrated by recording the photoreaction of bacteriorhodopsin initiated by a short laser pulse that is synchronized to the data recording. The resulting data are critically compared to those obtained by step-scan spectroscopy and demonstrate the relevance of performing experiments on proteins in solution. The spectrometer allows for future investigations of fast, non-repetitive processes, whose investigation is challenging to step-scan FT-IR spectroscopy. PMID:27370432

  15. New ultrarapid-scanning interferometer for FT-IR spectroscopy with microsecond time-resolution

    NASA Astrophysics Data System (ADS)

    Süss, B.; Ringleb, F.; Heberle, J.

    2016-06-01

    A novel Fourier-transform infrared (FT-IR) rapid-scan spectrometer has been developed (patent pending EP14194520.4) which yields 1000 times higher time resolution as compared to conventional rapid-scanning spectrometers. The central element to achieve faster scanning rates is based on a sonotrode whose front face represents the movable mirror of the interferometer. A prototype spectrometer with a time resolution of 13 μs was realized, capable of fully automated long-term measurements with a flow cell for liquid samples, here a photosynthetic membrane protein in solution. The performance of this novel spectrometer is demonstrated by recording the photoreaction of bacteriorhodopsin initiated by a short laser pulse that is synchronized to the data recording. The resulting data are critically compared to those obtained by step-scan spectroscopy and demonstrate the relevance of performing experiments on proteins in solution. The spectrometer allows for future investigations of fast, non-repetitive processes, whose investigation is challenging to step-scan FT-IR spectroscopy.

  16. Initial photochemistry of bilirubin probed by femtosecond spectroscopy.

    PubMed

    Zietz, Burkhard; Gillbro, Tomas

    2007-10-18

    Bilirubin is a breakdown product from heme catabolism, and reduced excretion of bilirubin can lead to jaundice. Phototherapy is the most common treatment for neonatal jaundice, a condition frequently encountered in newborn infants. Knowledge of the photochemistry of bilirubin, which is dominated by (ultra)fast components, is necessary for the profound understanding of the processes in phototherapy. Here, we report results from femtosecond fluorescence upconversion measurements on bilirubin and half-bilirubin model compounds, as well as pump-probe absorption measurements on bilirubin. A fast component of ca. 120 fs in the multiexponential fluorescence decay, being only visible in the bilirubin molecule, is interpreted as exciton localization within the molecular halves. The slower components of several hundreds of femtoseconds and a few picoseconds, occurring in bilirubin and the half-bilirubin model, are interpreted as relaxation to a (twisted) intermediate, which decays further with ca. 15 ps to the ground state. PMID:17927274

  17. Light Driven Energy Research at LCLS: Planned Pump-Probe X-ray Spectroscopy Studies on Photosynthetic Water Splitting

    NASA Astrophysics Data System (ADS)

    Bergmann, Uwe

    2010-02-01

    Arguably the most important chemical reaction on earth is the photosynthetic splitting of water to molecular oxygen by the Mn-containing oxygen-evolving complex (Mn-OEC) in the protein known as photosystem II (PSII). It is this reaction which has, over the course of some 3.8 billion years, gradually filled our atmosphere with O2 and consequently enabled and sustained the evolution of complex aerobic life. Coupled to the reduction of carbon dioxide, biological photosynthesis contributes foodstuffs for nutrition while recycling CO2 from the atmosphere and replacing it with O2. By utilizing sunlight to power these energy-requiring reactions, photosynthesis also serves as a model for addressing societal energy needs as we enter an era of diminishing fossil hydrocarbon resources. Understanding, at the molecular level, the dynamics and mechanism of how nature has solved this problem is of fundamental importance and could be critical to aid in the design of manufactured devices to accomplish the conversion of sunlight into useful electrochemical energy and transportable fuel in the foreseeable future. In order to understand the photosynthetic splitting of water by the Mn-OEC we need to be able to follow the reaction in real time at an atomic level. A powerful probe to study the electronic and molecular structure of the Mn-OEC is x-ray spectroscopy. Here, in particular x-ray emission spectroscopy (XES) has two crucial qualities for LCLS based time-dependent pump-probe studies of the Mn-OEC: a) it directly probes the Mn oxidation state and ligation, b) it can be performed with wavelength dispersive optics to avoid the necessity of scanning in pump probe experiments. Recent results and the planned time dependent experiments at LCLS will be discussed. )

  18. Cavity-Enhanced Frequency-Agile Rapid Scanning (fars) Spectroscopy: Experimental Realizations and Measurement Results

    NASA Astrophysics Data System (ADS)

    Long, David A.; Truong, Gar-Wing; Zee, Roger Van; Plusquellic, David F.; Hodges, Joseph T.

    2013-06-01

    We present a series of experimental realizations of cavity-enhanced, frequency-agile rapid scanning (FARS) spectroscopy using distributed feedback diode lasers, external cavity diode lasers, and ultra-narrow linewidth fiber lasers. FARS offers a scanning rate which is limited only by the cavity response time itself as well as a microwave-level frequency axis. Finally, it allows for an absorption sensitivity which is one of the highest ever reported. These realizations offer a range of applications from low-cost field measurements of trace gases to laboratory-based metrology.

  19. Nanoscale investigation of viscoelasticity in thin polymer films using environmental scanning probe microscopy

    NASA Astrophysics Data System (ADS)

    Schmidt, Ronald Henry

    The tribological and rheological behavior of thin polymer films at the nanometer length scale has become a topic of extreme technological and scientific interest. The friction and wear characteristics of ultrathin organic coatings are critical in magnetic storage media devices, as well as emerging technologies such as microelectromechanical devices. In the microelectronics industry, the ability to produce ultrathin coatings of photoresists and electron resists that are free of scratches and thickness fluctuations is a crucial step in any lithography process. Fortunately the need to understand the behavior of ultrathin organic films has coincided with the development of the scanning probe microscope (SPM) which is able to impose shear and tensile forces, and image the resulting deformations, on the nanometer scale. In contrast to traditional scientific disciplines like condensed matter physics and physical chemistry, the "nanoscience" community has only recently begun to examine the role of temperature in material response. This is largely because piezoelectric transducers are incompatible with substantial temperature elevation. A recent advance in SPM design has isolated the transducer and accompanying electronics from the sample, enabling investigators to heat samples to temperatures as high as 170°C without affecting the performance of the instrument. Using an environmental SPM, we examined the temperature and rate dependence of tip-imposed plastic and viscoelastic deformations in thin polymer films. Viscous flow in defects in nonwetting films was investigated as well. Chapter 1 provides a brief review of viscoelastic and plastic deformations in bulk polymers, the glass transition temperature, and the effect of confining polymer molecules to an interface on the observed glass transition temperature. Chapter 2 discusses scanning probe microscopy instrumentation, techniques, and applications to polymer thin film tribology. In Chapters 3 and 4, results are

  20. Implementation on a desktop computer of the real time feedback control loop of a scanning probe microscope

    NASA Astrophysics Data System (ADS)

    Aloisi, G.; Bacci, F.; Carlà, M.; Dolci, D.; Lanzi, L.

    2008-11-01

    A software package has been developed to implement the real time feedback control loop needed in scanning probe microscopy on a general purpose desktop computer of the current high-speed/multicore generation. The main features of the implementation of both the feedback loop and the control of the experiment on the same computer are discussed. The package can work with several general purpose data acquisition boards and can be extended in a modular way to further board models; timing performance has been tested with several hardware configurations and some applications common in scanning probe microscopy. The package is available under an Open Source license.

  1. Probing Spatial Spin Correlations of Ultracold Gases by Quantum Noise Spectroscopy

    SciTech Connect

    Bruun, G. M.; Andersen, Brian M.; Demler, Eugene; Soerensen, Anders S.

    2009-01-23

    Spin noise spectroscopy with a single laser beam is demonstrated theoretically to provide a direct probe of the spatial correlations of cold fermionic gases. We show how the generic many-body phenomena of antibunching, pairing, antiferromagnetic, and algebraic spin liquid correlations can be revealed by measuring the spin noise as a function of laser width, temperature, and frequency.

  2. Development of Two-Photon Pump Polarization Spectroscopy Probe Technique Tpp-Psp for Measurements of Atomic Hydrogen .

    NASA Astrophysics Data System (ADS)

    Satija, Aman; Lucht, Robert P.

    2015-06-01

    Atomic hydrogen (H) is a key radical in combustion and plasmas. Accurate knowledge of its concentration can be used to better understand transient phenomenon such as ignition and extinction in combustion environments. Laser induced polarization spectroscopy is a spatially resolved absorption technique which we have adapted for quantitative measurements of H atom. This adaptation is called two-photon pump, polarization spectroscopy probe technique (TPP-PSP) and it has been implemented using two different laser excitation schemes. The first scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-3P levels using a circularly polarized 656-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 656 nm. As a result, the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. The laser beams were created by optical parametric generation followed by multiple pulse dye amplification stages. This resulted in narrow linewidth beams which could be scanned in frequency domain and varied in energy. This allowed us to systematically investigate saturation and Stark effect in 2S-3P transitions with the goal of developing a quantitative H atom measurement technique. The second scheme involves the two-photon excitation of 1S-2S transitions using a linearly polarized 243-nm beam. An anisotropy is created amongst Zeeman states in 2S-4P transitions using a circularly polarized 486-nm pump beam. This anisotropy rotates the polarization of a weak, linearly polarized probe beam at 486 nm. As a result the weak probe beam "leaks" past an analyzer in the detection channel and is measured using a PMT. This signal can be related to H atom density in the probe volume. A dye laser was pumped by third harmonic of a Nd:YAG laser to create a laser beam

  3. Subnanometre enzyme mechanics probed by single-molecule force spectroscopy

    NASA Astrophysics Data System (ADS)

    Pelz, Benjamin; Žoldák, Gabriel; Zeller, Fabian; Zacharias, Martin; Rief, Matthias

    2016-02-01

    Enzymes are molecular machines that bind substrates specifically, provide an adequate chemical environment for catalysis and exchange products rapidly, to ensure fast turnover rates. Direct information about the energetics that drive conformational changes is difficult to obtain. We used subnanometre single-molecule force spectroscopy to study the energetic drive of substrate-dependent lid closing in the enzyme adenylate kinase. Here we show that in the presence of the bisubstrate inhibitor diadenosine pentaphosphate (AP5A), closing and opening of both lids is cooperative and tightly coupled to inhibitor binding. Surprisingly, binding of the substrates ADP and ATP exhibits a much smaller energetic drive towards the fully closed state. Instead, we observe a new dominant energetic minimum with both lids half closed. Our results, combining experiment and molecular dynamics simulations, give detailed mechanical insights into how an enzyme can cope with the seemingly contradictory requirements of rapid substrate exchange and tight closing, to ensure efficient catalysis.

  4. Subnanometre enzyme mechanics probed by single-molecule force spectroscopy.

    PubMed

    Pelz, Benjamin; Žoldák, Gabriel; Zeller, Fabian; Zacharias, Martin; Rief, Matthias

    2016-01-01

    Enzymes are molecular machines that bind substrates specifically, provide an adequate chemical environment for catalysis and exchange products rapidly, to ensure fast turnover rates. Direct information about the energetics that drive conformational changes is difficult to obtain. We used subnanometre single-molecule force spectroscopy to study the energetic drive of substrate-dependent lid closing in the enzyme adenylate kinase. Here we show that in the presence of the bisubstrate inhibitor diadenosine pentaphosphate (AP5A), closing and opening of both lids is cooperative and tightly coupled to inhibitor binding. Surprisingly, binding of the substrates ADP and ATP exhibits a much smaller energetic drive towards the fully closed state. Instead, we observe a new dominant energetic minimum with both lids half closed. Our results, combining experiment and molecular dynamics simulations, give detailed mechanical insights into how an enzyme can cope with the seemingly contradictory requirements of rapid substrate exchange and tight closing, to ensure efficient catalysis. PMID:26906294

  5. Subnanometre enzyme mechanics probed by single-molecule force spectroscopy

    PubMed Central

    Pelz, Benjamin; Žoldák, Gabriel; Zeller, Fabian; Zacharias, Martin; Rief, Matthias

    2016-01-01

    Enzymes are molecular machines that bind substrates specifically, provide an adequate chemical environment for catalysis and exchange products rapidly, to ensure fast turnover rates. Direct information about the energetics that drive conformational changes is difficult to obtain. We used subnanometre single-molecule force spectroscopy to study the energetic drive of substrate-dependent lid closing in the enzyme adenylate kinase. Here we show that in the presence of the bisubstrate inhibitor diadenosine pentaphosphate (AP5A), closing and opening of both lids is cooperative and tightly coupled to inhibitor binding. Surprisingly, binding of the substrates ADP and ATP exhibits a much smaller energetic drive towards the fully closed state. Instead, we observe a new dominant energetic minimum with both lids half closed. Our results, combining experiment and molecular dynamics simulations, give detailed mechanical insights into how an enzyme can cope with the seemingly contradictory requirements of rapid substrate exchange and tight closing, to ensure efficient catalysis. PMID:26906294

  6. SPIN POLARIZED PHOTOELECTRON SPECTROSCOPY AS A PROBE OF MAGNETIC SYSTEMS.

    SciTech Connect

    JOHNSON, P.D.; GUNTHERODT, G.

    2006-11-01

    Spin-polarized photoelectron spectroscopy has developed into a versatile tool for the study of surface and thin film magnetism. In this chapter, we examine the methodology of the technique and its recent application to a number of different problems. We first examine the photoemission process itself followed by a detailed review of spin-polarization measurement techniques and the related experimental requirements. We review studies of spin polarized surface states, interface states and quantum well states followed by studies of the technologically important oxide systems including half-metallic transition metal oxides, ferromagnet/oxide interfaces and the antiferromagnetic cuprates that exhibit high Tc Superconductivity. We also discuss the application of high-resolution photoemission with spin resolving capabilities to the study of spin dependent self energy effects.

  7. Fluctuation spectroscopy: a new probe of old stellar populations

    SciTech Connect

    Van Dokkum, Pieter G.; Conroy, Charlie

    2014-12-10

    We introduce a new method to determine the relative contributions of different types of stars to the integrated light of nearby early-type galaxies. As is well known, the surface brightness of these galaxies shows pixel-to-pixel fluctuations due to Poisson variations in the number of giant stars. Differential spectroscopy of pixels as a function of fluctuation strength ({sup f}luctuation spectroscopy{sup )} effectively measures the spectral variation of stars as a function of their luminosity, information that is otherwise difficult to obtain for individual stars outside of the Local Group. We apply this technique to the elliptical galaxy NGC 4472, using Hubble Space Telescope/Advanced Camera for Surveys imaging in six narrow-band ramp filters tuned to spectral features in the range 0.8 μm-1.0 μm. Pixels with ±5% broad-band variations show differential color variations of 0.1%-1.0% in the narrow-band filters. These variations are primarily due to the systematic increase in TiO absorption strength with increasing luminosity on the upper giant branch. The data are very well reproduced by the same Conroy and van Dokkum stellar population synthesis model that is the best fit to the integrated light, with residuals in the range 0.03%-0.09%. Models with ages or metallicities that are significantly different from the integrated-light values do not yield good fits. We can also rule out several modifications to the underlying model, including the presence of a significant (>3% of the light) population of late M giants. The current observations constitute a powerful test of the expected luminosities and temperatures of metal-rich giants in massive early-type galaxies. Studies of pixels with much larger (negative) fluctuations will provide unique information on main sequence stars and the stellar initial mass function.

  8. Imaging of biological samples by a collection-mode photon scanning tunneling microscope with an apertured probe

    NASA Astrophysics Data System (ADS)

    Naya, Masayuki; Mononobe, Shuji; Uma Maheswari, R.; Saiki, Tosiharu; Ohtsu, Motoichi

    1996-02-01

    We report on high resolution imaging by a collection-mode photon scanning tunneling microscope (c-mode PSTM). In our PSTM system, we have used a novel probe with a nanometric protrusion formed from a metal coated sharpened fiber. By using this probe, flagellar filaments of salmonella of diameter 25 nm could be imaged to have a full width at half maximum of 50 nm. Obtained images strongly depended on the separation of the sample to the probe, the diameter of the aperture, and polarization of the irradiated light. Comments on the origins of these dependencies are given.

  9. Ultrafast dynamics in pentacene and tetracene probed using optical pump-probe spectroscopy

    NASA Astrophysics Data System (ADS)

    Thorsmølle, Verner; Averitt, Richard; Demsar, Jure; Chi, Xiaoliu; Tretiak, Sergie; Ramirez, Arthur; Taylor, Antoinette

    2004-03-01

    Here we present optical pump-probe measurements of photoinduced (PI) changes in the reflectivity and transmissivity of tetracene and pentacene single crystals. We studied the carrier relaxation dynamics as a function of probe photon energy aiming to elucidate the electronic structure and carrier dynamics in the singlet and triplet manifolds. We observe singlet exciton recombination, singlet fission, and triplet state absorption, which we can identify in the photoinduced (PI) absorption spectrum. In particular, both compounds display a broad long-lived (>>1ns) PI absorption. In tetracene this feature is centered at approximately 1.7 eV, while in pentacene it is centered around 1.4 eV and is very pronounced. The long relaxation time suggests that the state being probed is the triplet state T1 (i.e. T1->Tn). On the other hand, the width of the PI absorption band suggests that the final state is a band-like state at 1.7 eV (1.4 eV) above the triplet state in tetracene (pentacene). This observation supports the semiconductor band model.

  10. Probing the Active Galactic Nuclei using optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Vivek, M.

    Variability studies offer one of the best tools for understanding the physical conditions present in regions close to the central engine in an AGN. We probed the various properties of AGN through time variability studies of spectral lines in the optical wavelengths using the 2m telescope in IUCAA Girawali observatory. The absorption line variability studies are mainly concentrated in understanding the nature of outflows in quasars. Quasar outflows have a huge impact on the evolution of central supermassive blackholes, their host galaxies and the surrounding intergalactic medium. Studying the variability in these Broad Absorption Lines (BALs) can help us understand the structure, evolution, and basic physical properties of these outflows. We conducted a repeated Low ionization BAL monitoring program with 27 LoBALs (Low Ionization BALs) at z 0.3-2.1 covering timescales from 3.22 to 7.69 years in the quasar rest frame. We see a variety of phenomena, including some BALs that either appeared or disappeared completely and some BALs which do not vary over the observation period. In one case, the excited fine structure lines have changed dramatically. One source shows signatures of radiative acceleration. Here, we present the results from this program. Emission line studies are concentrated in understanding the peculiar characteristics of a dual-AGN source SDSS J092712.64+294344.0.

  11. Probing the Higgs force with isotope shift spectroscopy

    NASA Astrophysics Data System (ADS)

    Ozeri, Roee; Delaunay, Cedric; Perez, Gilad; Soreq, Yotam

    2016-05-01

    The Higgs boson, the last missing piece of the Standard Model (SM) of elementary particles, was recently observed by experiments in the Large Hadron Collider (LHC). To check whether this is indeed the SM Higgs, its coupling to other elementary particles should be experimentally measured. Current limits placed by LHC experiments on the coupling of the Higgs to the main building block of matter; the electron and the up and down quarks; are orders of magnitude larger than the SM predictions. Here, we propose to use the measurement of isotope shifts in optical atomic clock transitions to probe the Higgs boson coupling to electrons and nuclei. We show that the Higgs force between nuclei and bound electrons induces measurable nonlinearities to the King relation between isotope shifts. With current state-of-the-art accuracy in frequency comparison, limits which compete with, or even surpass, the bounds provided by LHC experiments can be achieved. Improved knowledge of these couplings is an important test of the SM. Similarly, this measurement could lead to an improved sensitivity to the presence of new physics.

  12. Cryoprotectant redistribution along the frozen straw probed by Raman spectroscopy.

    PubMed

    Karpegina, Yu A; Okotrub, K A; Brusentsev, E Yu; Amstislavsky, S Ya; Surovtsev, N V

    2016-04-01

    The distribution of cryoprotectant (10% glycerol) and ice along the frozen plastic straw (the most useful container for freezing mammalian semen, oocytes and embryos) was studied by Raman scattering technique. Raman spectroscopy being a contactless, non-invasive tool was applied for the straws filled with the cryoprotectant solution and frozen by controlled rate programs commonly used for mammalian embryos freezing. Analysis of Raman spectra measured at different points along the straw reveals a non-uniform distribution of the cryoprotectant. The ratio between non-crystalline solution and ice was found to be increased by several times at the bottom side of the solution column frozen by the standard freezing program. The increase of the cryoprotectant fraction occurs in the area where embryos or oocytes are normally placed during their freezing. Possible effects of the cooling rate and the ice nucleation temperature on the cryoprotectant fraction at the bottom side of the solution column were considered. Our findings highlight that the ice fraction around cryopreserved embryos or oocytes can differ significantly from the averaged one in the frozen plastic straws. PMID:26794460

  13. Probing of different conformations of piperazine using Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    SenGupta, Sumana; Maiti, Nandita; Chadha, Ridhima; Kapoor, Sudhir

    2014-06-01

    Piperazine exists in a number of energetically close structural conformations, and here, we investigated the dependence of their relative abundance on the surrounding conditions by using Raman and SERS spectroscopy in pure solid, aqueous solution and Ag hydrosol. The experimental results were interpreted by DFT calculations using B3LYP functional with aug-cc-pvdz/LANL2DZ basis sets. In the chair form of piperazine, which is more stable than the skewed boat by ∼8 kcal mol-1, the two N-H bonds can remain equatorial or axial, leading to three different conformations, eq-eq, eq-ax and ax-ax. The calculated Raman spectrum of the lowest energy eq-eq conformation corresponds well with the experimental spectrum in pure solid, indicating eq-eq to be predominant. But, the contribution of the eq-ax conformation was found to be maximum in aqueous solution. The SERS spectrum revealed that eq-ax conformation was preferably adopted as piperazine was adsorbed vertically through its axial N-atom over silver nanoparticle surface.

  14. Probing skin interaction with hydrogen peroxide using diffuse reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Zonios, George; Dimou, Aikaterini; Galaris, Dimitrios

    2008-01-01

    Hydrogen peroxide is an important oxidizing agent in biological systems. In dermatology, it is frequently used as topical antiseptic, it has a haemostatic function, it can cause skin blanching, and it can facilitate skin tanning. In this work, we investigated skin interaction with hydrogen peroxide, non-invasively, using diffuse reflectance spectroscopy. We observed transient changes in the oxyhaemoglobin and deoxyhaemoglobin concentrations as a result of topical application of dilute H2O2 solutions to the skin, with changes in deoxyhaemoglobin concentration being more pronounced. Furthermore, we did not observe any appreciable changes in melanin absorption properties as well as in the skin scattering properties. We also found no evidence for production of oxidized haemoglobin forms. Our observations are consistent with an at least partial decomposition of hydrogen peroxide within the stratum corneum and epidermis, with the resulting oxygen and/or remaining hydrogen peroxide inducing vasoconstriction to dermal blood vessels and increasing haemoglobin oxygen saturation. An assessment of the effects of topical application of hydrogen peroxide to the skin may serve as the basis for the development of non-invasive techniques to measure skin antioxidant capacity and also may shed light onto skin related disorders such as vitiligo.

  15. Fabrication of surface confined biomolecular, polymeric, and metallic nanostructures using scanning probe and electron beam lithography

    NASA Astrophysics Data System (ADS)

    Lee, Woo Kyung

    This thesis presents the fabrication and characterization of surface-confined nanostructures of biomolecules, polymer brushes, and gold nanowires on gold and silicon substrates. The molecular recognition-mediated, stepwise fabrication of patterned proteins (biotin and streptavidin) and stimulus-responsive elastin-like polypeptide (ELP) nanostructures with feature sizes on the order of 200 nm is described. Dip-pen nanolithography (DPN) of 16-mercaptohexadecanoic acid (MHA) on gold was used to build templates to tether biomolecular nanostructures. It is shown that streptavidin nanopatterns provide adapter surfaces for biotinylated proteins by molecular recognition. Nanopatterned ELPs were shown to undergo a reversible, hydrophilic-hydrophobic phase transition in response to external stimuli. Here, this phase transition behavior was studied on the molecular level by adhesion force measurements using an AFM. The strong hydrophobic interactions between ELPs were exploited to reversibly immobilize a thioredoxin-ELP fusion protein onto ELP nanopatterns above the lower critical solution temperature (LCST), demonstrating the potential for ELP nanoarrays in reusable lab-on-chip devices for protein purification or nanoscale analysis. The fabrication of surface-confined stimulus-responsive pNIPAAM brush nanopatterns in a "grafting-from" approach that combines scanning probe lithography or electron beam lithography with surface-initiated atom transfer radical polymerization (ATRP) is described. The reversible, stimulus-responsive conformational height change of nanopatterned pNIPAAM brushes was demonstrated by inverse transition cycling in water-methanol cononsolvent mixtures. The triggered control of interfacial properties on the nanometer scale holds significant promise for actuation in bionanotechnology applications where polymeric actuators may manipulate the transport, separation, and detection of biomolecules. The potentially important phenomenon of polymer brush

  16. Serine O-sulfation probed by IRMPD spectroscopy.

    PubMed

    Paciotti, Roberto; Coletti, Cecilia; Re, Nazzareno; Scuderi, Debora; Chiavarino, Barbara; Fornarini, Simonetta; Crestoni, Maria Elisa

    2015-10-21

    The sulfation of amino acids is a frequent post-translational modification. It is highly labile, though, and characterizing it by mass spectrometry, an otherwise powerful and widely exploited tool in analytical proteomics, is a challenge. The presently reported study is aimed at revealing the O-sulfation of l-serine and elucidating the effects of protonation and deprotonation on the structure and stability of the ensuing ionic species, [sSer + H](+) and [sSer - H](-). These ions are obtained as gaseous, isolated species by electrospray ionization, trapped in a Paul ion-trap, and sampled by IR multiple photon dissociation (IRMPD) spectroscopy in either the 750-1900 cm(-1) fingerprint range, or the 2900 and 3700 cm(-1) range encompassing the N-H and O-H stretching modes. The recorded IRMPD spectra present diagnostic signatures of the sulfate modification which are missing in the spectra of the native serine ions, [Ser + H](+) and [Ser - H](-). The experimental IRMPD features have been interpreted by comparison with the linear IR spectra of the lowest energy structures that are likely candidates for the sampled ions, calculated at the M06-2X/6-311+G(d,p) level of theory. Evidence is gathered that the most stable conformations of [sSer + H](+) are stabilized by hydrogen bonding interactions between the protonated amino group and both the carbonyl and sulfate oxygens. [sSer - H](-) ions possess a negatively charged sulfate group involved in either a S=O···HN or a S=O···HO hydrogen bond. The experimental IRMPD spectra are consistent with the presence of multiple low-lying structures in a thermally equilibrated population of several species particularly in the case of [sSer - H](-) ions, where the high structural flexibility combined with the presence of a negative charge favors the co-existence of several different H-bonding motifs. PMID:26027702

  17. SCAN+

    Energy Science and Technology Software Center (ESTSC)

    2009-11-01

    SCAN+ is a software application specifically designed to control the positioning of a gamma spectrometer by a two dimensional translation system above spent fuel bundles located in a sealed spent fuel cask. The gamma spectrometer collects gamma spectrum information for the purpose of spent fuel cask fuel loading verification. SCAN+ performs manual and automatic gamma spectrometer positioning functions as-well-as exercising control of the gamma spectrometer data acquisitioning functions. Cask configuration files are used to determinemore » the positions of spent fuel bundles. Cask scanning files are used to determine the desired scan paths for scanning a spent fuel cask allowing for automatic unattended cask scanning that may take several hours.« less

  18. Development of single-crystal diamond scanning probes with nitrogen-vacancy centers for cryogenic magnetometry with nanoscale spatial resolution

    NASA Astrophysics Data System (ADS)

    Jenkins, Alec; Pelliccione, Matthew; Ovartchaiyapong, Preeti; Reetz, Christopher; Bleszynski Jayich, Ania

    Scanning probes based on the nitrogen-vacancy (NV) defect center in diamond are powerful tools for imaging magnetic phenomena at the nanoscale. In particular, extending the operation of these probes to cryogenic temperatures opens up a wide range of condensed matter systems that can be studied. In this talk, we demonstrate a variable temperature NV scanning magnetometer consisting of an atomic-force microscope housed in a closed-cycle cryostat integrated with custom confocal optics. With this microscope we have observed 6-nm spatial resolution and 3 μT /√{Hz} sensitivity at T = 6 K. The single-crystal diamond scanning probes that contain shallow and coherent NV centers are critical to the performance of the microscope. The probes are designed with the aim of reducing the NV-sample separation and increasing collection of NV fluorescence, both while maintaining the spin coherence properties of the defects. We describe the fabrication of these probes as well as ongoing efforts to improve their sensitivity and spatial resolution.

  19. PREDICTING CHEMICAL REACTIVITY OF HUMIC SUBSTANCES FOR MINERALS AND XENOBIOTICS: USE OF COMPUTATIONAL CHEMISTRY, SCANNING PROBE MICROSCOPY AND VIRTUAL REALITY

    EPA Science Inventory

    In this chapter we review the literature on scanning probe microscopy (SPM), virtual reality (VR), and computational chemistry and our earlier work dealing with modeling lignin, lignin-carbohydrate complexes (LCC), humic substances (HSs) and non-bonded organo-mineral interactions...

  20. Cy3 in AOT reverse micelles II. Probing intermicellar interactions using fluorescence correlation spectroscopy.

    PubMed

    McPhee, Jeffrey T; Scott, Eric; Levinger, Nancy E; Van Orden, Alan

    2011-08-11

    Cyanine-3 (Cy3) fluorescent dye molecules confined in sodium di-2-ethylhexyl sulfosuccinate (AOT) reverse micelles were examined using dynamic light scattering and fluorescence correlation spectroscopy to probe the kinetics of Cy3 dye and reverse micelle aggregation. This study explored a range of reverse micelle sizes, defined as w(0) = [H(2)O]/[AOT], in which the occupation number ranged from one Cy3 molecule per ∼10(5) to ∼10(6) reverse micelles. These measurements reveal that in the smallest reverse micelle, w(0) = 1, the Cy3 molecules aggregate to form H-aggregate dimers, and the Cy3 dimerization is accompanied by the formation of a transient dimer between reverse micelles. Transient reverse micelle dimer particles are only observed in the small fraction of Cy3-labeled reverse micelles probed by fluorescence correlation spectroscopy and are not observed in the bulk solution probed by dynamic light scattering. Furthermore, fluorescence correlation spectroscopy makes it possible to probe the size and shape of these dimers, revealing prolate ellipsoid-shaped particles with twice the volume and surface area of a single reverse micelle. PMID:21761943

  1. Scanning tunneling microscopy, orbital-mediated tunneling spectroscopy, and ultraviolet photoelectron spectroscopy of metal(II) tetraphenylporphyrins deposited from vapor.

    PubMed

    Scudiero, L; Barlow, D E; Mazur, U; Hipps, K W

    2001-05-01

    Thin films of vapor-deposited Ni(II) and Co(II) complexes of tetraphenylporphyrin (NiTPP and CoTPP) were studied supported on gold and embedded in Al-Al(2)O(3)-MTPP-Pb tunnel diodes, where M = Ni or Co. Thin films deposited onto polycrystalline gold were analyzed by ultraviolet photoelectron spectroscopy (UPS) using He I radiation. Scanning tunneling microscopy (STM) and orbital-mediated tunneling spectroscopy (STM-OMTS) were performed on submonolayer films of CoTPP and NiTPP supported on Au(111). Inelastic electron tunneling spectroscopy (IETS) and OMTS were measured in conventional tunnel diode structures. The highest occupied pi molecular orbital of the porphyrin ring was seen in both STM-OMTS and UPS at about 6.4 eV below the vacuum level. The lowest unoccupied pi molecular orbital of the porphyrin ring was observed by STM-OMTS and by IETS-OMTS to be located near 3.4 eV below the vacuum level. The OMTS spectra of CoTPP had a band near 5.2 eV (below the vacuum level) that was attributed to transient oxidation of the central Co(II) ion. That is, it is due to electron OMT via the half-filled d(z)(2) orbital present in Co(II) of CoTPP. The NiTPP OMTS spectra show no such band, consistent with the known difficulty of oxidation of the Ni(II) ion. The STM-based OMTS allowed these two porphyrin complexes to be easily distinguished. The present work is the first report of the observation of STM-OMTS, tunnel junction OMTS, and UPS of the same compounds. Scanning tunneling microscope-based orbital-mediated tunneling provides more information than UPS or tunnel junction-based OMTS and does so with molecular-scale resolution. PMID:11457159

  2. 4D scanning transmission ultrafast electron microscopy: Single-particle imaging and spectroscopy.

    PubMed

    Ortalan, Volkan; Zewail, Ahmed H

    2011-07-20

    We report the development of 4D scanning transmission ultrafast electron microscopy (ST-UEM). The method was demonstrated in the imaging of silver nanowires and gold nanoparticles. For the wire, the mechanical motion and shape morphological dynamics were imaged, and from the images we obtained the resonance frequency and the dephasing time of the motion. Moreover, we demonstrate here the simultaneous acquisition of dark-field images and electron energy loss spectra from a single gold nanoparticle, which is not possible with conventional methods. The local probing capabilities of ST-UEM open new avenues for probing dynamic processes, from single isolated to embedded nanostructures, without being affected by the heterogeneous processes of ensemble-averaged dynamics. Such methodology promises to have wide-ranging applications in materials science and in single-particle biological imaging. PMID:21615171

  3. Fluorescence suppression using wavelength modulated Raman spectroscopy in fiber-probe-based tissue analysis

    NASA Astrophysics Data System (ADS)

    Praveen, Bavishna B.; Ashok, Praveen C.; Mazilu, Michael; Riches, Andrew; Herrington, Simon; Dholakia, Kishan

    2012-07-01

    In the field of biomedical optics, Raman spectroscopy is a powerful tool for probing the chemical composition of biological samples. In particular, fiber Raman probes play a crucial role for in vivo and ex vivo tissue analysis. However, the high-fluorescence background typically contributed by the auto fluorescence from both a tissue sample and the fiber-probe interferes strongly with the relatively weak Raman signal. Here we demonstrate the implementation of wavelength-modulated Raman spectroscopy (WMRS) to suppress the fluorescence background while analyzing tissues using fiber Raman probes. We have observed a significant signal-to-noise ratio enhancement in the Raman bands of bone tissue, which have a relatively high fluorescence background. Implementation of WMRS in fiber-probe-based bone tissue study yielded usable Raman spectra in a relatively short acquisition time (~30 s), notably without any special sample preparation stage. Finally, we have validated its capability to suppress fluorescence on other tissue samples such as adipose tissue derived from four different species.

  4. Extending the plasmonic lifetime of tip-enhanced Raman spectroscopy probes.

    PubMed

    Kumar, Naresh; Spencer, Steve J; Imbraguglio, Dario; Rossi, Andrea M; Wain, Andrew J; Weckhuysen, Bert M; Roy, Debdulal

    2016-05-21

    Tip-enhanced Raman spectroscopy (TERS) is an emerging technique for simultaneous mapping of chemical composition and topography of a surface at the nanoscale. However, rapid degradation of TERS probes, especially those coated with silver, is a major bottleneck to the widespread uptake of this technique and severely prohibits the success of many TERS experiments. In this work, we carry out a systematic time-series study of the plasmonic degradation of Ag-coated TERS probes under different environmental conditions and demonstrate that a low oxygen (<1 ppm) and a low moisture (<1 ppm) environment can significantly improve the plasmonic lifetime of TERS probes from a few hours to a few months. Furthermore, using X-ray photoelectron spectroscopy (XPS) measurements on Ag nanoparticles we show that the rapid plasmonic degradation of Ag-coated TERS probes can be correlated to surface oxide formation. Finally, we present practical guidelines for the effective use and storage of TERS probes to improve their plasmonic lifetime based on the results of this study. PMID:27140329

  5. Scanning electron microscopy and electron probe microanalysis studies of human pineal concretions.

    PubMed

    Kodaka, T; Mori, R; Debari, K; Yamada, M

    1994-10-01

    The calcareous concretions of human pineal bodies were investigated with scanning electron microscopy and electron probe microanalysis. The initial concretions measuring 5-7 microns in diameter may have started at the calcified pinealocytes. They grew appositionally forming concentric laminations, and then the simple calcospherulites over 20 microns occasionally aggregated with each other. Some of them became numerous spherulite-aggregated concretions. Others individually grew with scallop-shaped concentric laminations at intervals of 0.05-1 microns and became lobated calcospherulites up to 0.5 mm. The concretions over 0.5 mm were formed by their attachments. The major elements were Ca and P, while traces of S, Mg, and Na were detected. In the calcification and crystallization values, the center of the concretions over 50 microns was significantly higher than the periphery, while there were no differences among the centers and also among the peripheries. The Ca and P amounts in the center were 30.8% and 14.2% by weight and the Ca/P molar ratio was 1.68; thereby the sand-grain-shaped crystals may be nearly hydroxyapatite, as reported previously. PMID:7699308

  6. 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. PMID:22047297

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

    NASA Astrophysics Data System (ADS)

    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.

  8. Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor

    NASA Astrophysics Data System (ADS)

    Pelliccione, Matthew; Jenkins, Alec; Ovartchaiyapong, Preeti; Reetz, Christopher; Emmanouilidou, Eve; Ni, Ni; Bleszynski Jayich, Ania C.

    2016-08-01

    High-spatial-resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogen–vacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor on the basis of its atomic size and quantum-limited sensing capabilities. It has remained an outstanding challenge to implement the NV centre as a nanoscale scanning magnetic probe at cryogenic temperatures, however, where many solid-state systems exhibit non-trivial magnetic order. Here, we present NV magnetic imaging down to 6 K with 3 μT Hz–1/2 field sensitivity, and use the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with critical temperature Tc = 30 K. The expansion of NV-based magnetic imaging to cryogenic temperatures will enable future studies of previously inaccessible nanoscale magnetism in condensed-matter systems.

  9. Observations of liver cancer cells in scanning probe acoustic microscope: a preliminary study

    NASA Astrophysics Data System (ADS)

    Chen, Xiaohui; Fang, Xiaoyue; Xi, Qing; Guo, Hua; Zhang, Ning; Ding, Mingyue

    2016-04-01

    Scanning probe acoustic microscope (SPAM) can be used to acquire the morphology image as well as the non-destructive internal structures acoustic image. However, the observations of the morphology image as well as the internal structures acoustic image of liver cancer cells in SPAM are few. In this paper, we cultured 4 different types of liver cancer cells on the silicon wafer and coverslip to observe their morphology images as well as acoustic images in SPAM, and made a preliminary study of the 8 types of cells specimens (hereinafter referred to as the silicon specimens and coverslips specimens). The experimental measurement results showed that some cellular pseudopodium were observed in the morphology images of the coverslip specimens while no such cellular pseupodium were appeared in the morphology images of the silicon specimens, which concluded that the living liver cancer cells were less likely to grow on the silicon wafer. SPAM provides a rapid and sensitive visual method for studying the morphology and internal structures of the cancer cells. The proposed method can be also used to obtain the morphology and internal information in both solid and soft material wafers, such as silicon and cells, with the resolution of nanometer scale.

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

    PubMed

    Green, Matthew F B; Esat, Taner; Wagner, Christian; Leinen, Philipp; Grötsch, Alexander; Tautz, F Stefan; Temirov, Ruslan

    2014-01-01

    One of the paramount goals in nanotechnology is molecular-scale functional design, which includes arranging molecules into complex structures at will. The first steps towards this goal were made through the invention of the scanning probe microscope (SPM), which put single-atom and single-molecule manipulation into practice for the first time. Extending the controlled manipulation to larger molecules is expected to multiply the potential of engineered nanostructures. Here we report an enhancement of the SPM technique that makes the manipulation of large molecular adsorbates much more effective. By using a commercial motion tracking system, we couple the movements of an operator's hand to the sub-angstrom precise positioning of an SPM tip. Literally moving the tip by hand we write a nanoscale structure in a monolayer of large molecules, thereby showing that our method allows for the successful execution of complex manipulation protocols even when the potential energy surface that governs the interaction behaviour of the manipulated nanoscale object(s) is largely unknown. PMID:25383304

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

    PubMed Central

    Green, Matthew F B; Esat, Taner; Wagner, Christian; Leinen, Philipp; Grötsch, Alexander; Tautz, F Stefan

    2014-01-01

    Summary One of the paramount goals in nanotechnology is molecular-scale functional design, which includes arranging molecules into complex structures at will. The first steps towards this goal were made through the invention of the scanning probe microscope (SPM), which put single-atom and single-molecule manipulation into practice for the first time. Extending the controlled manipulation to larger molecules is expected to multiply the potential of engineered nanostructures. Here we report an enhancement of the SPM technique that makes the manipulation of large molecular adsorbates much more effective. By using a commercial motion tracking system, we couple the movements of an operator's hand to the sub-angstrom precise positioning of an SPM tip. Literally moving the tip by hand we write a nanoscale structure in a monolayer of large molecules, thereby showing that our method allows for the successful execution of complex manipulation protocols even when the potential energy surface that governs the interaction behaviour of the manipulated nanoscale object(s) is largely unknown. PMID:25383304

  12. Virtual reality visual feedback for hand-controlled scanning probe microscopy manipulation of single molecules.

    PubMed

    Leinen, Philipp; Green, Matthew F B; Esat, Taner; Wagner, Christian; Tautz, F Stefan; Temirov, Ruslan

    2015-01-01

    Controlled manipulation of single molecules is an important step towards the fabrication of single molecule devices and nanoscale molecular machines. Currently, scanning probe microscopy (SPM) is the only technique that facilitates direct imaging and manipulations of nanometer-sized molecular compounds on surfaces. The technique of hand-controlled manipulation (HCM) introduced recently in Beilstein J. Nanotechnol. 2014, 5, 1926-1932 simplifies the identification of successful manipulation protocols in situations when the interaction pattern of the manipulated molecule with its environment is not fully known. Here we present a further technical development that substantially improves the effectiveness of HCM. By adding Oculus Rift virtual reality goggles to our HCM set-up we provide the experimentalist with 3D visual feedback that displays the currently executed trajectory and the position of the SPM tip during manipulation in real time, while simultaneously plotting the experimentally measured frequency shift (Δf) of the non-contact atomic force microscope (NC-AFM) tuning fork sensor as well as the magnitude of the electric current (I) flowing between the tip and the surface. The advantages of the set-up are demonstrated by applying it to the model problem of the extraction of an individual PTCDA molecule from its hydrogen-bonded monolayer grown on Ag(111) surface. PMID:26665087

  13. Electrochemical and scanning probe microscopic characterization of spontaneously adsorbed organothiolate monolayers at gold

    SciTech Connect

    Wong, Sze-Shun Season

    1999-12-10

    This dissertation presented several results which add to the general knowledge base regarding organothiolates monolayer spontaneously adsorbed at gold films. Common to the body of this work is the use of voltammetric reductive resorption and variants of scanning probe microscopy to gain insight into the nature of the monolayer formation process as well as the resulting interface. The most significant result from this work is the success of using friction force microscopy to discriminate the end group orientation of monolayer chemisorbed at smooth gold surfaces with micrometer resolution (Chapter 4). The ability to detect the differences in the orientational disposition is demonstrated by the use PDMS polymer stamp to microcontact print an adlayer of n-alkanethiolate of length n in a predefine pattern onto a gold surface, followed by the solution deposition of a n-alkanethiol of n {+-} 1 to fill in the areas on the gold surface intentionally not coated by the stamping process. These two-component monolayers can be discriminated by using friction force microscopy which detects differences in friction contributed by the differences in the orientation of the terminal groups at surfaces. This success has recently led to the detection of the orientation differences at nanometer scale. Although the substrates examined in this work consisted entirely of smooth gold films, the same test can be performed on other smooth substrates and monolayer materials.

  14. Scanned probe imaging of nanoscale magnetism at cryogenic temperatures with a single-spin quantum sensor.

    PubMed

    Pelliccione, Matthew; Jenkins, Alec; Ovartchaiyapong, Preeti; Reetz, Christopher; Emmanouilidou, Eve; Ni, Ni; Bleszynski Jayich, Ania C

    2016-08-01

    High-spatial-resolution magnetic imaging has driven important developments in fields ranging from materials science to biology. However, to uncover finer details approaching the nanoscale with greater sensitivity requires the development of a radically new sensor technology. The nitrogen-vacancy (NV) defect in diamond has emerged as a promising candidate for such a sensor on the basis of its atomic size and quantum-limited sensing capabilities. It has remained an outstanding challenge to implement the NV centre as a nanoscale scanning magnetic probe at cryogenic temperatures, however, where many solid-state systems exhibit non-trivial magnetic order. Here, we present NV magnetic imaging down to 6 K with 3 μT Hz(-1/2) field sensitivity, and use the technique to image vortices in the iron pnictide superconductor BaFe2(As0.7P0.3)2 with critical temperature Tc = 30 K. The expansion of NV-based magnetic imaging to cryogenic temperatures will enable future studies of previously inaccessible nanoscale magnetism in condensed-matter systems. PMID:27136130

  15. Virtual reality visual feedback for hand-controlled scanning probe microscopy manipulation of single molecules

    PubMed Central

    Leinen, Philipp; Green, Matthew F B; Esat, Taner; Wagner, Christian; Tautz, F Stefan

    2015-01-01

    Summary Controlled manipulation of single molecules is an important step towards the fabrication of single molecule devices and nanoscale molecular machines. Currently, scanning probe microscopy (SPM) is the only technique that facilitates direct imaging and manipulations of nanometer-sized molecular compounds on surfaces. The technique of hand-controlled manipulation (HCM) introduced recently in Beilstein J. Nanotechnol. 2014, 5, 1926–1932 simplifies the identification of successful manipulation protocols in situations when the interaction pattern of the manipulated molecule with its environment is not fully known. Here we present a further technical development that substantially improves the effectiveness of HCM. By adding Oculus Rift virtual reality goggles to our HCM set-up we provide the experimentalist with 3D visual feedback that displays the currently executed trajectory and the position of the SPM tip during manipulation in real time, while simultaneously plotting the experimentally measured frequency shift (Δf) of the non-contact atomic force microscope (NC-AFM) tuning fork sensor as well as the magnitude of the electric current (I) flowing between the tip and the surface. The advantages of the set-up are demonstrated by applying it to the model problem of the extraction of an individual PTCDA molecule from its hydrogen-bonded monolayer grown on Ag(111) surface. PMID:26665087

  16. Probing weak localization in chemical vapor deposition graphene wide constriction using scanning gate microscopy.

    PubMed

    Chuang, C; Matsunaga, M; Liu, F-H; Woo, T-P; Aoki, N; Lin, L-H; Wu, B-Y; Ochiai, Y; Liang, C-T

    2016-02-19

    Low-temperature scanning gate microscopy (LT-SGM) studies of graphene allow one to obtain important spatial information regarding coherent transport such as weak localization (WL) and universal conductance fluctuations. Although fascinating LT-SGM results on pristine graphene prepared by mechanical exfoliation have been reported in the literature, there appears to be a dearth of LT-SGM results on chemical vapor deposition (CVD)-grown graphene whose large scale and flexible substrate transferability make it an ideal candidate for coherent electronic applications. To this end, we have performed LT-SGM studies on CVD-grown graphene wide constriction (0.8 μm), which can be readily prepared by cost-effective optical lithography fully compatible with those in wafer foundry, in the WL regime. We find that the movable local gate can sensitively modulate the total conductance of the CVD graphene constriction possibly due to the intrinsic grain boundaries and merged domains, a great advantage for applications in coherent electronics. Moreover, such a conductance modulation by LT-SGM provides an additional, approximately magnetic-field-independent probe for studying coherent transport such as WL in graphene and spatial conductance variation. PMID:26762929

  17. Probing weak localization in chemical vapor deposition graphene wide constriction using scanning gate microscopy

    NASA Astrophysics Data System (ADS)

    Chuang, C.; Matsunaga, M.; Liu, F.-H.; Woo, T.-P.; Aoki, N.; Lin, L.-H.; Wu, B.-Y.; Ochiai, Y.; Liang, C.-T.

    2016-02-01

    Low-temperature scanning gate microscopy (LT-SGM) studies of graphene allow one to obtain important spatial information regarding coherent transport such as weak localization (WL) and universal conductance fluctuations. Although fascinating LT-SGM results on pristine graphene prepared by mechanical exfoliation have been reported in the literature, there appears to be a dearth of LT-SGM results on chemical vapor deposition (CVD)-grown graphene whose large scale and flexible substrate transferability make it an ideal candidate for coherent electronic applications. To this end, we have performed LT-SGM studies on CVD-grown graphene wide constriction (0.8 μm), which can be readily prepared by cost-effective optical lithography fully compatible with those in wafer foundry, in the WL regime. We find that the movable local gate can sensitively modulate the total conductance of the CVD graphene constriction possibly due to the intrinsic grain boundaries and merged domains, a great advantage for applications in coherent electronics. Moreover, such a conductance modulation by LT-SGM provides an additional, approximately magnetic-field-independent probe for studying coherent transport such as WL in graphene and spatial conductance variation.

  18. Spin-noise spectroscopy under resonant optical probing conditions: Coherent and nonlinear effects

    SciTech Connect

    Horn, H.; Mueller, G. M.; Huebner, J.; Oestreich, M.; Rasel, E. M.; Santos, L.

    2011-10-15

    Highly sensitive Faraday rotation spectroscopy is used to measure the fluctuating magnetization noise of noninteracting rubidium atoms under resonant and nonresonant optical probing conditions. The spin-noise frequency spectra, in conjunction with the probe light detuning with respect to the D{sub 2} transition, reveal clear signatures of coherent coupling of the participating electronic levels. The results are explained by extended Bloch equations, including homogeneous and inhomogeneous broadening mechanisms. Our measurements further indicate that spin noise originating from excited states is governed at high intensities by collective effects.

  19. Probing the surfaces of heterogeneous catalysts by in situ IR spectroscopy.

    PubMed

    Lamberti, Carlo; Zecchina, Adriano; Groppo, Elena; Bordiga, Silvia

    2010-12-01

    This critical review describes the reactivity of heterogeneous catalysts from the point of view of four simple, but essential for Chemistry, molecules (namely dihydrogen, carbon monoxide, nitrogen monoxide and ethylene) that are considered as probes or as reactants in combination with "in situ" controlled temperature and pressure Infrared spectroscopy. The fundamental properties of H(2), CO, NO and C(2)H(4) are shortly described in order to justify their different behaviour in respect of isolated sites in different environments, extended surfaces, clusters, crystalline or amorphous materials. The description is given by considering some "key studies" and trying to evidence similarities and differences among surfaces and probes (572 references). PMID:21038053

  20. Scanning Tunneling Microscopy and Scanning Tunneling Spectroscopy Studies of Chromium Clusters Deposited on Moiré Patterns on HOPG

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Luo, Hong

    2014-03-01

    Moiré patterns (MP) formed by twisted graphene layers, present great potential for use as periodic substrates to facilitate the growth of nanostructures to obtain useful electronic and/or magnetic properties. The growth of Chromium (Cr) deposited on MPs on the surface of highly ordered pyrolitic graphite (HOPG) and its effects on the electronic structure in the MPs were studied by scanning tunneling microscopy/spectroscopy (STM/STS). Without Cr, two van Hove singularities (VHSs) were observed by STS on the MPs. With low coverage of Cr, atoms deposited on graphite Moiré form small clusters randomly distributed over the surface. With the presence of Cr clusters, the energy difference between the two VHS peaks enlarged while its linear dependence on the twisting angle remains. Compare to the situation before deposition, the graphite's Fermi velocity increased while the interlayer interaction decreased. The electronic structure modification caused by a Cr cluster as a function of distance from the cluster was studied with extremely low coverage. The effective distance can reach about 10 lattice cells of the Moiré pattern. This work was supported by NSF DMR1006286.

  1. Scanning tunneling spectroscopy of single-wall carbon nanotubes on a polymerized gold substrate

    NASA Astrophysics Data System (ADS)

    Shao, F.; Zha, F. X.; Pan, C. B.; Shao, J.; Zhao, X. L.; Shen, X. C.

    2014-02-01

    The physics picture on scanning tunneling spectroscopy of single-wall carbon nanotubes (SWCNTs) was revisited recently [H. Lin et al., Nat. Mater. 9, 235 (2010), 10.1038/nmat2771] with an image potential model under the framework of the many-body theory whose description is different from that of conventional one-particle tight-binding theory. The model is explored further in the present study of SWCNTs with an ultrahigh-vacuum scanning tunneling microscope. In the experiments, two types of samples were measured. In one sample, the nanotubes were in intimate contact with the gold surface and the observed tunneling gaps of semiconductor nanotubes fit the prediction of the one-particle model. In the other sample, the nanotubes were isolated by a thin polymer (4-vinylpyridine) layer from the gold surface. The semiconducting SWCNTs in the latter sample show tunneling gaps several hundreds of milli-electron volts larger than the prediction of the one-particle model. The results can, however, be interpreted by the modified image potential model, which takes into account the surface dielectric mechanism. The consistent picture of the tunneling gaps of the different samples provides insight into the scanning tunneling spectroscopy of SWCNTs from the standpoint of many-body theory.

  2. 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. PMID:25821686

  3. 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

  4. Use of scanning probe microscopies to study dopants at semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Nelson, Mark William

    Dopants, in semiconductors, are detected as either protrusions or depressions in scanning tunneling microscopy (STM) images. Measured dopant heights for layered semiconductors are considerably larger than for conventional semiconductors. This is interpreted as the influence of dopant induced electrostatic forces between the tip and the sample leading to a structural deformation of the surface around the dopant atoms. To investigate the influence of electrostatic forces, we performed STM measurements on p-type MoS2 at different bias voltages. The bias dependence of the STM images indicates the presence of electrostatic forces. Additional measurements with current imaging tunneling spectroscopy (CITS) show that changes in the density of states at dopant sites play only a minor role and cannot account for the large protrusions observed. Atomic force microscopy (AFM), with an applied D.C. voltage between the cantilever and sample, also confirms the role of electrostatic forces. Recently, we developed a new TappingmodeRTM AFM (TMAFM) based dopant profiling method based on an electrostatic mechanism similar to the STM imaging of dopants in layered semiconductors. TMAFM with an applied bias was used to spatially resolve areas of different doping type and density on silicon patterned via ion implantation. The application of a D.C. bias between the cantilever and sample during the measurement results in a Coulomb interaction between the tip and sample, whose magnitude depends on the spatial variation in the doping density. This effect was utilized to detect areas differing in doping by monitoring the phase angle between the drive frequency and cantilever response while scanning over areas of differing doping density. Measurements at various bias voltages are presented to demonstrate that the phase contrast observed between differently doped areas is directly connected to the bias induced surface potential (band bending) present on these areas. A quantitative investigation

  5. Supercriticality of charge centers in graphene probed with scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Jiang, Yuhang; Mao, Jinhai; Li, Guohong; Moldovan, D.; Masir, M. Ramezani; Peeters, F. M.; Andrei, Eva Y.

    2015-03-01

    The massless Dirac fermion carriers in graphene, with their effective fine structure constant,αg, being of order unity, provide fertile ground for exploring the physics of ultra-relativistic particles in the strong coupling limit.In particulara positive charge Z embedded in graphene is expected to exhibit supercritical behavior already for Z>Zc = 0.5/αg, in stark contrast to the atomic case where Zc ~ 170 is experimentally inaccessible. However due to the significant screening in graphene, attaining the supercritical regime is challenging. We will report on a new method to create charge centerswithin the graphene layer whose charge, Z, can be tuned to exceed the critical value. Using low temperature scanning tunneling microscopy and spectroscopy we study the evolution in the local electronic structure of graphene as a function of Z, from charge neutrality to the supercritical regime, which is identified by comparing to numerical simulations. Work supported by DOE-FG02-99ER45742 and NSF DMR 1207108.

  6. Characterization of dilute optical lattices using pump-probe spectroscopy and photon correlation measurements

    NASA Astrophysics Data System (ADS)

    Clements, Ethan; Ross, Preston; Rapp, Anthony; Cai, Hong; Reigle, Alex; Schlonsky, Eli; Lee, Hoseong; Clemens, James; Bali, Samir

    2016-05-01

    We experimentally investigate optical lattices using three different methods: pump-probe spectroscopy of vibrational energy levels, photon correlation of light scattered by cold atoms, and fluorescence imaging. Photon correlations of the scattered light can be used to measure lattice dwell times and crossover times between lattice sites. From this information we can derive the diffusion constant which can then be compared to direct measurement via fluorescence imaging. Furthermore, by Fourier transforming the time delayed photon correlations we can obtain the intensity spectrum which can be compared directly to pump-probe spectroscopy of the vibrational energy levels. We plan to carefully study situations in which the atomic transport properties deviate from Boltzman Gibbs statistics.

  7. Polarized pump--probe spectroscopy of electronic excitation transport in photosynthetic antennas

    SciTech Connect

    Struve, W.S. )

    1990-08-01

    Polarized pump--probe spectroscopy was performed with 1.5--2 psec resolution on the bacteriochlorophyll a protein antenna complex from the green sulfur bacterium Prosthecochloris aestuarii and on native and enriched photosystem I particles from spinach. The resulting photobleaching profiles reflect the details of singlet electronic-excitation transport in these photosynthetic antennas, in which the pigments are complexed by proteins into clusters of five or more chromophores.

  8. Low Temperature Scanning Tunneling Spectroscopy of isolated Mn12-Ph Single Molecule Magnets

    NASA Astrophysics Data System (ADS)

    Reaves, K.; Han, P.; Iwaya, K.; Hitosugi, T.; Packwood, D.; Katzgraber, H. G.; Zhao, H.; Dunbar, K. R.; Kim, K.; Teizer, W.

    2015-03-01

    We study Mn12O12(C6H5COO)16(H2O)4 (Mn12-Ph) single-molecule magnets on a Cu(111) surface using scanning tunneling microscopy and scanning tunneling spectroscopy at cryogenic temperatures (T < 6K). We report the observation of Mn12-Ph in isolation and in thin films, deposited through in situ vacuum spray deposition onto clean Cu(111). The tunneling current of isolated Mn12-Ph, normalized with respect to the Cu background, shows a strong bias voltage dependence within the molecular interior. The qualitative features of these I vs.V curves differ by spatial location in several intriguing ways (e.g. fixed junction impedance with increasing bias voltages). We explore these normalized I vs. V curves and present a phenomenological explanation for the observed behaviors, corresponding to the physical and electronic structure within the molecule. Funding from WPI-AIMR.

  9. Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics

    DOE PAGESBeta

    Picón, A.; Lehmann, C. S.; Bostedt, C.; Rudenko, A.; Marinelli, A.; Osipov, T.; Rolles, D.; Berrah, N.; Bomme, C.; Bucher, M.; et al

    2016-05-23

    New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Specifically, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. In this paper, we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ionsmore » during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site.« less

  10. Development of Femtosecond Stimulated Raman Spectroscopy as a Probe of Photoisomerization Dynamics

    NASA Astrophysics Data System (ADS)

    Kieda, Ryan D.; Dunkelberger, Adam D.; Shin, Jaeyoon; Oudenhoven, Tracy; Crim, F. Fleming

    2012-06-01

    Femtosecond stimulated Raman spectroscopy (FSRS) has proven to be a reliable probe of condensed phase dynamics by simultaneously achieving both exceptional temporal and frequency resolution. We report on preliminary attempts to utilize FSRS as a probe of the photoisomerization of dMe-OMe-NAIP (N-alkylated indanylidene pyrroline Schiff base) which is a mimic of the chromophore in Rhodopsin. We implement a 400 nm Raman pump/continuum probe process following a 400 nm actinic pump pulse which initiates photoisomerization. This initial work appears to corroborate previous transient absorption studies of NAIP while granting a vibrational mode specific look at the dynamics involved in relaxation from its excited state and subsequent vibrational relaxation.

  11. Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics.

    PubMed

    Picón, A; Lehmann, C S; Bostedt, C; Rudenko, A; Marinelli, A; Osipov, T; Rolles, D; Berrah, N; Bomme, C; Bucher, M; Doumy, G; Erk, B; Ferguson, K R; Gorkhover, T; Ho, P J; Kanter, E P; Krässig, B; Krzywinski, J; Lutman, A A; March, A M; Moonshiram, D; Ray, D; Young, L; Pratt, S T; Southworth, S H

    2016-01-01

    New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site. PMID:27212390

  12. Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics

    NASA Astrophysics Data System (ADS)

    Picón, A.; Lehmann, C. S.; Bostedt, C.; Rudenko, A.; Marinelli, A.; Osipov, T.; Rolles, D.; Berrah, N.; Bomme, C.; Bucher, M.; Doumy, G.; Erk, B.; Ferguson, K. R.; Gorkhover, T.; Ho, P. J.; Kanter, E. P.; Krässig, B.; Krzywinski, J.; Lutman, A. A.; March, A. M.; Moonshiram, D.; Ray, D.; Young, L.; Pratt, S. T.; Southworth, S. H.

    2016-05-01

    New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site.

  13. Hetero-site-specific X-ray pump-probe spectroscopy for femtosecond intramolecular dynamics

    PubMed Central

    Picón, A.; Lehmann, C. S.; Bostedt, C.; Rudenko, A.; Marinelli, A.; Osipov, T.; Rolles, D.; Berrah, N.; Bomme, C.; Bucher, M.; Doumy, G.; Erk, B.; Ferguson, K. R.; Gorkhover, T.; Ho, P. J.; Kanter, E. P.; Krässig, B.; Krzywinski, J.; Lutman, A. A.; March, A. M.; Moonshiram, D.; Ray, D.; Young, L.; Pratt, S. T.; Southworth, S. H.

    2016-01-01

    New capabilities at X-ray free-electron laser facilities allow the generation of two-colour femtosecond X-ray pulses, opening the possibility of performing ultrafast studies of X-ray-induced phenomena. Particularly, the experimental realization of hetero-site-specific X-ray-pump/X-ray-probe spectroscopy is of special interest, in which an X-ray pump pulse is absorbed at one site within a molecule and an X-ray probe pulse follows the X-ray-induced dynamics at another site within the same molecule. Here we show experimental evidence of a hetero-site pump-probe signal. By using two-colour 10-fs X-ray pulses, we are able to observe the femtosecond time dependence for the formation of F ions during the fragmentation of XeF2 molecules following X-ray absorption at the Xe site. PMID:27212390

  14. Design of a rectal probe for diffuse optical spectroscopy imaging for chemotherapy and radiotherapy monitoring

    NASA Astrophysics Data System (ADS)

    van de Giessen, Martijn; Santoro, Ylenia; Mirzaei Zarandi, Soroush; Pigazzi, Alessio; Cerussi, Albert E.; Tromberg, Bruce J.

    2014-03-01

    Diffuse optical spectroscopy imaging (DOSI) has shown great potential for the early detection of non-responding tumors during neoadjuvant chemotherapy in breast cancer, already one day after therapy starts. Patients with rectal cancer receive similar chemotherapy treatment. The rectum geometry and tissue properties of healthy and tumor tissue in the rectum and the requirement of surface contact impose constraints on the probe design. In this work we present the design of a DOSI probe with the aim of early chemotherapy/radiotherapy effectiveness detection in rectal tumors. We show using Monte Carlo simulations and phantom measurements that the colon tissue can be characterized reliably using a source-detector separation in the order of 10 mm. We present a design and rapid prototype of a probe for DOSI measurements that can be mounted on a standard laparoscope and that fits through a standard rectoscope. Using predominantly clinically approved components we aim at fast clinical translation.

  15. Probe diffusion in polymer solutions and hydrogels using fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Michelman-Ribeiro, Ariel; Boukari, Hacene; Horkay, Ferenc; Nossal, Ralph

    2006-03-01

    We apply fluorescence correlation spectroscopy (FCS) to measure the diffusion of small fluorescent probes (TAMRA, Mw = 430 Da; dextran, Mw = 10 kDa) in poly(vinyl alcohol) (PVA) solutions and hydrogels. PVA is a linear, neutral, biocompatible polymer, whose hydrogels have many biotechnology applications, such as drug-delivery devices and tissue scaffolds. The FCS measurements indicate that the probe diffusion decreases when the polymer solution is cross-linked. Further, the more the polymer chains are cross-linked, the slower the particles diffuse. These results suggest that the cross-link density, which is often ignored in the analysis of probe diffusion data in gels, must be taken into account. Remarkably, we find that the apparent diffusion time and the elastic modulus of the gels show a linear correlation.

  16. Quantification of probe-sample interactions of a scanning thermal microscope using a nanofabricated calibration sample having programmable size.

    PubMed

    Ge, Yunfei; Zhang, Yuan; Booth, Jamie A; Weaver, Jonathan M R; Dobson, Phillip S

    2016-08-12

    We report a method for quantifying scanning thermal microscopy (SThM) probe-sample thermal interactions in air using a novel temperature calibration device. This new device has been designed, fabricated and characterised using SThM to provide an accurate and spatially variable temperature distribution that can be used as a temperature reference due to its unique design. The device was characterised by means of a microfabricated SThM probe operating in passive mode. This data was interpreted using a heat transfer model, built to describe the thermal interactions during a SThM thermal scan. This permitted the thermal contact resistance between the SThM tip and the device to be determined as 8.33 × 10(5) K W(-1). It also permitted the probe-sample contact radius to be clarified as being the same size as the probe's tip radius of curvature. Finally, the data were used in the construction of a lumped-system steady state model for the SThM probe and its potential applications were addressed. PMID:27363896

  17. 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.

  18. 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.

  19. 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. PMID:26724038

  20. Design and construction of a point-contact spectroscopy rig with lateral scanning capability

    NASA Astrophysics Data System (ADS)

    Tortello, M.; Park, W. K.; Ascencio, C. O.; Saraf, P.; Greene, L. H.

    2016-06-01

    The design and realization of a cryogenic rig for point-contact spectroscopy measurements in the needle-anvil configuration is presented. Thanks to the use of two piezoelectric nano-positioners, the tip can move along the vertical (z) and horizontal (x) direction and thus the rig is suitable to probe different regions of a sample in situ. Moreover, it can also form double point-contacts on different facets of a single crystal for achieving, e.g., an interferometer configuration for phase-sensitive measurements. For the later purpose, the sample holder can also host a Helmholtz coil for applying a small transverse magnetic field to the junction. A semi-rigid coaxial cable can be easily added for studying the behavior of Josephson junctions under microwave irradiation. The rig can be detached from the probe and thus used with different cryostats. The performance of this new probe has been tested in a Quantum Design PPMS system by conducting point-contact Andreev reflection measurements on Nb thin films over large areas as a function of temperature and magnetic field.

  1. Design and construction of a point-contact spectroscopy rig with lateral scanning capability.

    PubMed

    Tortello, M; Park, W K; Ascencio, C O; Saraf, P; Greene, L H

    2016-06-01

    The design and realization of a cryogenic rig for point-contact spectroscopy measurements in the needle-anvil configuration is presented. Thanks to the use of two piezoelectric nano-positioners, the tip can move along the vertical (z) and horizontal (x) direction and thus the rig is suitable to probe different regions of a sample in situ. Moreover, it can also form double point-contacts on different facets of a single crystal for achieving, e.g., an interferometer configuration for phase-sensitive measurements. For the later purpose, the sample holder can also host a Helmholtz coil for applying a small transverse magnetic field to the junction. A semi-rigid coaxial cable can be easily added for studying the behavior of Josephson junctions under microwave irradiation. The rig can be detached from the probe and thus used with different cryostats. The performance of this new probe has been tested in a Quantum Design PPMS system by conducting point-contact Andreev reflection measurements on Nb thin films over large areas as a function of temperature and magnetic field. PMID:27370466

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

    DOE PAGESBeta

    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.

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

    SciTech Connect

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

    2007-11-15

    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.

  5. Step-Scan FTIR spectroscopy and quantum chemical calculations of xanthone in the triplet state

    NASA Astrophysics Data System (ADS)

    Buschhaus, L.; Kleinermanns, K.

    2014-10-01

    Step-Scan-FTIR spectroscopy has been used to measure the infrared spectrum of xanthone in the triplet state using chloroform as solvent. Xanthone is an important triplet sensitizer and therefore suitable as model system. Xanthone was excited at 266 nm and its IR triplet spectrum measured in the range 1000-1750 cm-1. The spectrum was analyzed by comparison with DFT/B3LYP/TZVP/COSMO calculations. Further on the results were compared to gas phase IR measurements of triplet xanthone and calculations of isolated xanthone. Mainly based on the calculations we tried to identify the geometry changes from the electronic ground state to the first triplet state.

  6. Scanning tunneling spectroscopy on ZnO(0001) surfaces : evidence for an inhomogeneous electronic structure

    NASA Astrophysics Data System (ADS)

    Hackens, B.; Rodrigues, M. S.; Faniel, S.; Mouthuy, P. O.; Melinte, S.; Dumont, J.; Sporken, R.

    2010-03-01

    We performed low temperature (77 K) scanning tunneling microscopy (STM) and spectroscopy (STS) on the polar Zn-terminated ZnO(0001) surface [1]. STM and STS data show that the surface electronic structure strongly depends on the local morphology : we observe a narrow bandgap and surface states in the flat regions, and, in the defective surface regions, a wide bandgap without surface states. We also image atomically-resolved (√3 x√3)R30^o reconstructions in small defect-free areas.[4pt] [1] J. Dumont et al., Appl. Phys. Lett. 95, 132102 (2009).

  7. Excited state dynamics of metastable phthalocyanine-tetrasulfonate tetra-anions probed by pump/probe photoelectron spectroscopy

    SciTech Connect

    Ehrler, Oli T.; Yang Jiping; Sugiharto, Albert B.; Unterreiner, Andreas N.; Kappes, Manfred M.

    2007-11-14

    Femtosecond time-resolved pump-probe photoelectron spectroscopy was used to study elementary relaxation processes occurring in isolated phthalocyanine-tetrasulfonate tetra-anions ([MPc(SO{sub 3}){sub 4}]{sup 4-}, M=Cu,Ni, and ''free-base'' [H{sub 2}Pc(SO{sub 3}){sub 4}]{sup 4-}) following Q band excitation by one-photon absorption at 775 nm. Whereas the Cu and Ni systems decay rapidly by means of internal conversion without electron loss, the free-base phthalocyanine primarily undergoes excited state tunneling electron emission. This reflects less efficient coupling to lower lying states within the corresponding spin manifold. Results are interpreted in terms of (time-dependent) density functional theory calculations of ground and electronically excited states and kinetically modeled to yield the associated rates.

  8. Standardization in dimensional nanometrology: development of a calibration guideline for Scanning Probe Microscopy

    NASA Astrophysics Data System (ADS)

    Dziomba, Thorsten; Koenders, Ludger; Wilkening, Günter

    2005-10-01

    The continuing miniaturization in many technologies - among them the optical systems - demands high-resolution measurements with uncertainties in the nanometre-range or even well below. A brief introduction of measurement methods used at the micro- & nanometre scale is therefore given as introduction. While a wide range of these methods are well established for the determination of various physical properties down to the nanometric scale, it is Scanning Probe Microscopy (SPM) that provides a unique direct access to topographic surface features in the size range from atomic diameters to some ten or hundred micrometres. With the increasing use of SPMs as quantitative measurement instruments, the demand for standardized calibration routines also for this type of instruments rises. However, except for a few specially designed set-ups mainly at National Metrology Institutes (e. g. PTB in Germany), measurements made with SPMs usually lack traceability to the metre definition. A number of physical transfer standards have therefore been developed and are already available commercially. While detailed knowledge of the standards' properties is a prerequisite for their practical applicability, the calibration procedure itself deserves careful consideration as well. As there is, up to now, no generally accepted concept how to perform SPM calibrations, guidelines are now being developed on various national and international levels, e. g. VDI/VDE-GMA in Germany and ISO. This papers discusses the draft of an SPM calibration guideline by focusing on several critical practical aspects of SPM calibration. The paper intends to invite the readers to take active part in guideline discussions.

  9. The application of reflected light microscopy, scanning electron microscopy-energy dispersive spectroscopy, Auger electron spectroscopy and electron microprobe analysis to the study of dusts

    SciTech Connect

    Hagni, A.M.; Hagni, R.D. . Dept. of Geology and Geophysics)

    1993-03-01

    Over 500,000 tons of electric arc furnace (EAF) dust is generated each year in the US. The mineralogy and characterization of this dust is being studied to determine the phases and relationships of the valuable zinc, the hazardous lead, cadmium, and chromium, and the deleterious chlorine and fluorine. EAF dust averages 15--20% zinc and is therefore a potential source for 100,000 tons of zinc per year. The major mineralogical phases of EAF dust are franklinite (ZnFe[sub 2]O[sub 4]), magnetite (FeFe[sub 2]O[sub 4]), jacobsite (MnFe[sub 2]O[sub 4]), solid solutions between franklinite-magnetite-jacobsite, and zincite (ZnO). Franklinite, magnetite, and jacobsite solid solutions commonly are cruciform or dendritic crystals in a Ca-Fe-Si matrix and contain up to 5% chromium. Magnetite also occurs as spheres partially oxidized to hematite (Fe[sub 2]O[sub 3]) along its octahedral planes. The dust particles are predominantly in the form of spheres and broken spheres, ranging in size from 200 [mu]m to less than 1 [mu]m. Although many spheres are in the size ranges of 40--50 [mu]m and 10--20 [mu]m, most are less than 1 [mu]m in diameter. Automated scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) probed 118 particles in search of chlorine phases. Chlorine-bearing lime (CaO) was identified by that SEM study. In addition, chlorine is present as hydrophylite (CaCl[sub 2]) and sylvite (KCl). Auger electron spectroscopy (AES) was used to sputter the outer 180[angstrom] layer of the dust particles to search for the possible presence of cotunnite (PbCl[sub 2]) coatings, but none were detected. Minor phases detected include chalcopyrite (CuFeS[sub 2]), sphalerite (ZnS), pyrite (FeS[sub 2]), and coke.

  10. Soft x-ray spectroscopy for probing electronic and chemical states of battery materials

    NASA Astrophysics Data System (ADS)

    Wanli, Yang; Ruimin, Qiao

    2016-01-01

    The formidable challenge of developing high-performance battery system stems from the complication of battery operations, both mechanically and electronically. In the electrodes and at the electrode-electrolyte interfaces, chemical reactions take place with evolving electron states. In addition to the extensive studies of material synthesis, electrochemical, structural, and mechanical properties, soft x-ray spectroscopy provides unique opportunities for revealing the critical electron states in batteries. This review discusses some of the recent soft x-ray spectroscopic results on battery binder, transition-metal based positive electrodes, and the solid-electrolyte-interphase. By virtue of soft x-ray’s sensitivity to electron states, the electronic property, the redox during electrochemical operations, and the chemical species of the interphases could be fingerprinted by soft x-ray spectroscopy. Understanding and innovating battery technologies need a multimodal approach, and soft x-ray spectroscopy is one of the incisive tools to probe the chemical and physical evolutions in batteries.

  11. Improved accuracy and speed in scanning probe microscopy by image reconstruction from non-gridded position sensor data.

    PubMed

    Ziegler, Dominik; Meyer, Travis R; Farnham, Rodrigo; Brune, Christoph; Bertozzi, Andrea L; Ashby, Paul D

    2013-08-23

    Scanning probe microscopy (SPM) has facilitated many scientific discoveries utilizing its strengths of spatial resolution, non-destructive characterization and realistic in situ environments. However, accurate spatial data are required for quantitative applications but this is challenging for SPM especially when imaging at higher frame rates. We present a new operation mode for scanning probe microscopy that uses advanced image processing techniques to render accurate images based on position sensor data. This technique, which we call sensor inpainting, frees the scanner to no longer be at a specific location at a given time. This drastically reduces the engineering effort of position control and enables the use of scan waveforms that are better suited for the high inertia nanopositioners of SPM. While in raster scanning, typically only trace or retrace images are used for display, in Archimedean spiral scans 100% of the data can be displayed and at least a two-fold increase in temporal or spatial resolution is achieved. In the new mode, the grid size of the final generated image is an independent variable. Inpainting to a few times more pixels than the samples creates images that more accurately represent the ground truth. PMID:23892397

  12. Improved accuracy and speed in scanning probe microscopy by image reconstruction from non-gridded position sensor data

    NASA Astrophysics Data System (ADS)

    Ziegler, Dominik; Meyer, Travis R.; Farnham, Rodrigo; Brune, Christoph; Bertozzi, Andrea L.; Ashby, Paul D.

    2013-08-01

    Scanning probe microscopy (SPM) has facilitated many scientific discoveries utilizing its strengths of spatial resolution, non-destructive characterization and realistic in situ environments. However, accurate spatial data are required for quantitative applications but this is challenging for SPM especially when imaging at higher frame rates. We present a new operation mode for scanning probe microscopy that uses advanced image processing techniques to render accurate images based on position sensor data. This technique, which we call sensor inpainting, frees the scanner to no longer be at a specific location at a given time. This drastically reduces the engineering effort of position control and enables the use of scan waveforms that are better suited for the high inertia nanopositioners of SPM. While in raster scanning, typically only trace or retrace images are used for display, in Archimedean spiral scans 100% of the data can be displayed and at least a two-fold increase in temporal or spatial resolution is achieved. In the new mode, the grid size of the final generated image is an independent variable. Inpainting to a few times more pixels than the samples creates images that more accurately represent the ground truth.

  13. Toward single atom qubits on a surface: Pump-probe spectroscopy and electrically-driven spin resonance

    NASA Astrophysics Data System (ADS)

    Paul, William

    We will discuss the characterization of spin dynamics by pump-probe spectroscopy and the use of gigahertz-frequency electric fields to drive spin resonance of a Fe atom on a MgO/Ag(001) surface. In the spirit of this session, the technical challenges in applying a precise voltage to the tip sample junction across a wide radio-frequency bandwidth will be described. The energy relaxation time, T1, of single spins on surfaces can be measured by spin-polarized pump-probe STM (scanning tunneling microscopy). To date, the relaxation times reported for Fe-Cu dimers on Cu2N insulating films have been of the order ~100 ns. A three-order-of-magnitude enhancement of lifetime, to ~200 μs, was recently demonstrated for Co on a single-monolayer of MgO. Here, we report on the tailoring of the T1 lifetime of single Fe atoms on single- and multi- layer MgO films grown on Ag(001). Next, we demonstrate electron spin resonance of an individual single Fe atom, driven by a gigahertz-frequency electric field applied across the tip-sample junction, and detected by a spin-polarized tunneling current. The principle parameters of the spin resonance experiment, namely the phase coherence time T2 and the Rabi rate, are characterized for Fe atoms adsorbed to the monolayer MgO film.

  14. Kinetics of linear domains in LiNbO{sub 3} single crystals polarized by scanning probe microscopy

    SciTech Connect

    Bo, Huifeng; College of Science, Hebei United University, Tangshan 063009 ; Jin, Yaming; Xu, Tingting; Du, Yingchao; Kan, Yi; Lu, Xiaomei Zhu, Jinsong

    2013-12-16

    Growth and decay processes of linear domains in lithium niobate single crystals fabricated utilizing scanning probe microscopy were investigated. It is found that the initial configuration of linear domains is dependent on the fabrication parameters as scan velocity and voltage. The linear domains decay at the part where the domain width is small for two different processes. A comparison of critical stable domain size between dot and linear domains was carried out. The critical linear domain width is 0.7 times as large as the critical diameter of dot domain at the same sample thickness due to their smaller surface energy.

  15. Scanning Single-Molecule Fluorescence Correlation Spectroscopy Enables Kinetics Study of DNA Hairpin Folding with a Time Window from Microseconds to Seconds.

    PubMed

    Bi, Huimin; Yin, Yandong; Pan, Bailong; Li, Geng; Zhao, Xin Sheng

    2016-05-19

    Single-molecule fluorescence measurements have been widely used to explore kinetics and dynamics of biological systems. Among them, single-molecule imaging (SMI) is good at tracking processes slower than tens of milliseconds, whereas fluorescence correlation spectroscopy (FCS) is good at probing processes faster than submilliseconds. However, there is still shortage of simple yet effective single-molecule fluorescence method to cover the time-scale between submilliseconds and tens of milliseconds. To effectively bridge this millisecond gap, we developed a single-molecule fluorescence correlation spectroscopy (smFCS) method that works on surface-immobilized single molecules through surface scanning. We validated it by monitoring the classical DNA hairpin folding process. With a wide time window from microseconds to seconds, the experimental data are well fitted to the two-state folding model. All relevant molecular parameters, including the relative fluorescence brightness, equilibrium constant, and reaction rate constants, were uniquely determined. PMID:27140004

  16. Updates on Optical Emission Spectroscopy & Langmuir Probe Investigations on the Helicon Plasma Experiment (HPX)

    NASA Astrophysics Data System (ADS)

    Karama, Jackson; Frank, John; Azzari, Phillip; Hopson, Jordan; James, Royce; Duke-Tinson, Omar; Paolino, Richard; Sandri, Eva; Sherman, Justin; Wright, Eva; Turk, Jeremy

    2015-11-01

    HPX is developing a to shorter lifetime (20 - 30 ns) more reproducible plasma at the Coast Guard Academy Plasma Laboratory (CGAPL). Once achieved, spectral and particle probes will help to verify plasma mode transitions to the W-mode. These optical probes utilize movable filters, and ccd cameras to gather data at selected spectral frequency bands. Once corrections for the RF field are in place for the Langmuir probe, raw data will be collected and used to measure the plasma's density, temperature, and potentially the structure and behavior during experiments. Direct measurements of plasma properties can be determined with modeling and by comparison with the state transition tables, both using Optical Emission Spectroscopy (OES). The spectral will add to HPX's data collection capabilities and be used in conjunction with the particle probes, and Thomson Scattering device to create a robust picture of the internal and external plasma parameters on HPX. Progress on the implementation of the OES and Langmuir probes will be reported. Supported by U.S. DEPS Grant [HEL-JTO] PRWJFY15.

  17. A diamond-based scanning probe spin sensor operating at low temperature in ultra-high vacuum

    NASA Astrophysics Data System (ADS)

    Schaefer-Nolte, E.; Reinhard, F.; Ternes, M.; Wrachtrup, J.; Kern, K.

    2014-01-01

    We present the design and performance of an ultra-high vacuum (UHV) low temperature scanning probe microscope employing the nitrogen-vacancy color center in diamond as an ultrasensitive magnetic field sensor. Using this center as an atomic-size scanning probe has enabled imaging of nanoscale magnetic fields and single spins under ambient conditions. In this article we describe an experimental setup to operate this sensor in a cryogenic UHV environment. This will extend the applicability to a variety of molecular systems due to the enhanced target spin lifetimes at low temperature and the controlled sample preparation under UHV conditions. The instrument combines a tuning-fork based atomic force microscope (AFM) with a high numeric aperture confocal microscope and the facilities for application of radio-frequency (RF) fields for spin manipulation. We verify a sample temperature of <50 K even for strong laser and RF excitation and demonstrate magnetic resonance imaging with a magnetic AFM tip.

  18. A diamond-based scanning probe spin sensor operating at low temperature in ultra-high vacuum

    SciTech Connect

    Schaefer-Nolte, E.; Wrachtrup, J.; 3rd Institute of Physics and Research Center SCoPE, University Stuttgart, 70569 Stuttgart ; Reinhard, F.; Ternes, M.; Kern, K.; Institut de Physique de la Matière Condenseé, Ecole Polytechnique Fédérale de Lausanne, 1015 Lausanne

    2014-01-15

    We present the design and performance of an ultra-high vacuum (UHV) low temperature scanning probe microscope employing the nitrogen-vacancy color center in diamond as an ultrasensitive magnetic field sensor. Using this center as an atomic-size scanning probe has enabled imaging of nanoscale magnetic fields and single spins under ambient conditions. In this article we describe an experimental setup to operate this sensor in a cryogenic UHV environment. This will extend the applicability to a variety of molecular systems due to the enhanced target spin lifetimes at low temperature and the controlled sample preparation under UHV conditions. The instrument combines a tuning-fork based atomic force microscope (AFM) with a high numeric aperture confocal microscope and the facilities for application of radio-frequency (RF) fields for spin manipulation. We verify a sample temperature of <50 K even for strong laser and RF excitation and demonstrate magnetic resonance imaging with a magnetic AFM tip.

  19. Characterizing nanoscale scanning probes using electron microscopy: A novel fixture and a practical guide

    NASA Astrophysics Data System (ADS)

    Jacobs, Tevis D. B.; Wabiszewski, Graham E.; Goodman, Alexander J.; Carpick, Robert W.

    2016-01-01

    The nanoscale geometry of probe tips used for atomic force microscopy (AFM) measurements determines the lateral resolution, contributes to the strength of the tip-surface interaction, and can be a significant source of uncertainty in the quantitative analysis of results. While inverse imaging of the probe tip has been used successfully to determine probe tip geometry, direct observation of the tip profile using electron microscopy (EM) confers several advantages: it provides direct (rather than indirect) imaging, requires fewer algorithmic parameters, and does not require bringing the tip into contact with a sample. In the past, EM-based observation of the probe tip has been achieved using ad hoc mounting methods that are constrained by low throughput, the risk of contamination, and repeatability issues. We report on a probe fixture designed for use in a commercial transmission electron microscope that enables repeatable mounting of multiple AFM probes as well as a reference grid for beam alignment. This communication describes the design, fabrication, and advantages of this probe fixture, including full technical drawings for machining. Further, best practices are discussed for repeatable, non-destructive probe imaging. Finally, examples of the fixture's use are described, including characterization of common commercial AFM probes in their out-of-the-box condition.

  20. Characterizing nanoscale scanning probes using electron microscopy: A novel fixture and a practical guide.

    PubMed

    Jacobs, Tevis D B; Wabiszewski, Graham E; Goodman, Alexander J; Carpick, Robert W

    2016-01-01

    The nanoscale geometry of probe tips used for atomic force microscopy (AFM) measurements determines the lateral resolution, contributes to the strength of the tip-surface interaction, and can be a significant source of uncertainty in the quantitative analysis of results. While inverse imaging of the probe tip has been used successfully to determine probe tip geometry, direct observation of the tip profile using electron microscopy (EM) confers several advantages: it provides direct (rather than indirect) imaging, requires fewer algorithmic parameters, and does not require bringing the tip into contact with a sample. In the past, EM-based observation of the probe tip has been achieved using ad hoc mounting methods that are constrained by low throughput, the risk of contamination, and repeatability issues. We report on a probe fixture designed for use in a commercial transmission electron microscope that enables repeatable mounting of multiple AFM probes as well as a reference grid for beam alignment. This communication describes the design, fabrication, and advantages of this probe fixture, including full technical drawings for machining. Further, best practices are discussed for repeatable, non-destructive probe imaging. Finally, examples of the fixture's use are described, including characterization of common commercial AFM probes in their out-of-the-box condition. PMID:26827324

  1. Watching Domains Grow: In-situ studies of polarization switching by combined Scanning Probe and Scanning Transmission Electron Microscopy

    SciTech Connect

    Chang, Hye Jung; Kalinin, Sergei V; Yang, S.Y; Yu, P; Bhattacharya, S.; Wu, P; Balke, Nina; Jesse, Stephen; Chen, Long-Qing; Ramesh, R.; Pennycook, Stephen J; Borisevich, Albina Y

    2011-01-01

    Ferroelectric domain nucleation and growth in multiferroic BiFeO{sub 3} films is observed directly by applying a local electric field with a conductive tip inside a scanning transmission electron microscope. The nucleation and growth of a ferroelastic domain and its interaction with pre-existing 71{sup o} domain walls are observed and compared with the results of phase-field modeling. In particular, a preferential nucleation site and direction-dependent pinning of domain walls are observed due to slow kinetics of metastable switching in the sample without a bottom electrode. These in situ spatially resolved observations of a first-order bias-induced phase transition reveal the mesoscopic mechanisms underpinning functionality of a wide range of multiferroic materials.

  2. Noise Characteristics of 100nm-scaleGaAs/Al_xGa_{1-x}As Scanning Hall Probes

    SciTech Connect

    Hicks, C.W.; Luan, L.; Moler, K.A.; Zeldov, E.; /Weizmann Inst.

    2007-03-23

    The authors have fabricated and characterized GaAs/Al{sub x}Ga{sub 1-x}As two-dimensional electron gas scanning Hall probes for imaging perpendicular magnetic fields at surfaces. The Hall crosses range from 85 x 85 to 1000 x 1000 nm{sup 2}. They study low-frequency noise in these probes, especially random telegraph noise, and show that low-frequency noise can be significantly reduced by optimizing the voltage on a gate over the Hall cross. The authors demonstrate a 100 nm Hall probe with a sensitivity of 0.5 G/{radical}Hz (flux sensitivity of 0.25m {Phi}{sub 0}/{radical}Hz; spin sensitivity of 1.2 x 10{sup 4} {mu}{sub B}/{radical}Hz) at 3 Hz and 9 K.

  3. Imaging of enzyme activity by scanning electrochemical microscope equipped with a feedback control for substrate-probe distance.

    PubMed

    Oyamatsu, Daisuke; Hirano, Yu; Kanaya, Norihiro; Mase, Yoshiaki; Nishizawa, Matsuhiko; Matsue, Tomokazu

    2003-08-01

    The enzymatic activity of diaphorase (Dp) immobilized on a solid substrate was characterized using a scanning electrochemical microscope (SECM) with shear force feedback to control the substrate-probe distance. The shear force between the substrate and the probe was monitored with a tuning fork-type quartz crystal and used as the feedback control to set the microelectrode probe close to the substrate surface. The sensitivity and the contrast of the SECM image were improved in the constant distance mode (distance, 50 nm) with the shear force feedback compared to the image in the constant height mode without the feedback. By using this system, the SECM and topographic images of the immobilized diaphorase were simultaneously measured. The microelectrode tip used in this study was ground aslant like a syringe needle in order to obtain the shaper topographic images. This shape was also effective for avoiding the interference during the diffusion of the enzyme substrates. PMID:12893317

  4. Mapping Liquid-liquid protein phase separation using ultra-fast-scanning fluorescence correlation spectroscopy

    NASA Astrophysics Data System (ADS)

    Wei, Ming-Tzo; Elbaum-Garfinkle, Shana; Arnold, Craig B.; Priestley, Rodney D.; Brangwynne, Clifford P.

    Intrinsically disordered proteins (IDPs) are an understudied class of proteins that play important roles in a wide variety of biological processes in cells. We've previously shown that the C. elegans IDP LAF-1 phase separates into P granule-like droplets in vitro. However, the physics of the condensed phase remains poorly understood. Here, we use a novel technique, ultra-fast-scanning fluorescence correlation spectroscopy, to study the nano-scale rheological properties of LAF-1 droplets. Ultra-fast-scanning FCS uses a tunable acoustic gradient index of refraction (TAG) lens with an oil immersion objective to control axial movement of the focal point over a length of several micrometers at frequencies of 70kHz. Using ultra-fast-scanning FCS allows for the accurate determination of molecular concentrations and their diffusion coefficient, when the particle is passing through an excitation volume. Our work reveals an asymmetric LAF-1 phase diagram, and demonstrates that LAF-1 droplets are purely viscous phases which are highly tunable by salt concentration.

  5. Development of Broad Range Scan Capabilities with Jet Cooled Cavity Ringdown Spectroscopy

    NASA Astrophysics Data System (ADS)

    Codd, Terrance J.; Chen, Ming-Wei; Miller, Terry A.

    2011-06-01

    We have developed a technique for obtaining broad scans, >100 Cm-1, for jet cooled cavity ringdown spectroscopy (CRDS) spectra. Previously the scans of the jet cooled, CRDS apparatus were limited to <10 Cm-1 due to the use of a narrow linewidth radiation source. However, by coupling our jet cooled, CRDS apparatus with a moderate resolution (≃q 0.05 Cm-1) dye laser we are able to greatly increase our rate of data acquisition thereby gaining the capability to perform broad spectral surveys of jet cooled molecules. As a test of the capabilities of the technique we have scanned the tilde{A}-tilde{X} transition of NO_3 previously reported by Deev et al. at room temperature. We believe that this will be a very useful technique to search for transitions of cold molecules whose frequencies are not well known and which later can be studied using high resolution methods. A. Deev, J. Sommar, and M. Okumura, J. Chem. Phys. 122, 224305 (2005).

  6. Tissue classification and diagnostics using a fiber probe for combined Raman and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Cicchi, Riccardo; Anand, Suresh; Crisci, Alfonso; Giordano, Flavio; Rossari, Susanna; De Giorgi, Vincenzo; Maio, Vincenza; Massi, Daniela; Nesi, Gabriella; Buccoliero, Anna Maria; Guerrini, Renzo; Pimpinelli, Nicola; Pavone, Francesco S.

    2015-07-01

    Two different optical fiber probes for combined Raman and fluorescence spectroscopic measurements were designed, developed and used for tissue diagnostics. Two visible laser diodes were used for fluorescence spectroscopy, whereas a laser diode emitting in the NIR was used for Raman spectroscopy. The two probes were based on fiber bundles with a central multimode optical fiber, used for delivering light to the tissue, and 24 surrounding optical fibers for signal collection. Both fluorescence and Raman spectra were acquired using the same detection unit, based on a cooled CCD camera, connected to a spectrograph. The two probes were successfully employed for diagnostic purposes on various tissues in a good agreement with common routine histology. This study included skin, brain and bladder tissues and in particular the classification of: malignant melanoma against melanocytic lesions and healthy skin; urothelial carcinoma against healthy bladder mucosa; brain tumor against dysplastic brain tissue. The diagnostic capabilities were determined using a cross-validation method with a leave-one-out approach, finding very high sensitivity and specificity for all the examined tissues. The obtained results demonstrated that the multimodal approach is crucial for improving diagnostic capabilities. The system presented here can improve diagnostic capabilities on a broad range of tissues and has the potential of being used for endoscopic inspections in the near future.

  7. Tissue classification and diagnostics using a fiber probe for combined Raman and fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Cicchi, Riccardo; Anand, Suresh; Rossari, Susanna; Sturiale, Alessandro; Giordano, Flavio; De Giorgi, Vincenzo; Maio, Vincenza; Massi, Daniela; Nesi, Gabriella; Buccoliero, Anna Maria; Tonelli, Francesco; Guerrini, Renzo; Pimpinelli, Nicola; Pavone, Francesco S.

    2015-03-01

    Two different optical fiber probes for combined Raman and fluorescence spectroscopic measurements were designed, developed and used for tissue diagnostics. Two visible laser diodes were used for fluorescence spectroscopy, whereas a laser diode emitting in the NIR was used for Raman spectroscopy. The two probes were based on fiber bundles with a central multimode optical fiber, used for delivering light to the tissue, and 24 surrounding optical fibers for signal collection. Both fluorescence and Raman spectra were acquired using the same detection unit, based on a cooled CCD camera, connected to a spectrograph. The two probes were successfully employed for diagnostic purposes on various tissues in a good agreement with common routine histology. This study included skin, brain and bladder tissues and in particular the classification of: malignant melanoma against melanocytic lesions and healthy skin; urothelial carcinoma against healthy bladder mucosa; brain tumor against dysplastic brain tissue. The diagnostic capabilities were determined using a cross-validation method with a leave-one-out approach, finding very high sensitivity and specificity for all the examined tissues. The obtained results demonstrated that the multimodal approach is crucial for improving diagnostic capabilities. The system presented here can improve diagnostic capabilities on a broad range of tissues and has the potential of being used for endoscopic inspections in the near future.

  8. Unveiling nanometric plasmons optical properties with advanced electron spectroscopy in the Scanning Transmission Electron Microscope

    NASA Astrophysics Data System (ADS)

    Kociak, Mathieu

    Since the pioneering work of Yamamoto, the use of electron spectroscopy such as Cathodoluminescence (CL) and Electron Energy Loss Spectroscopy (EELS) in a Scanning (Transmission) Electron Microscope (STEM) has considerably helped improving our understanding of the optical properties of metallic nanoparticles. The resemblance of spectroscopic signals from electron and pure optical techniques leads to the intuition that both types of techniques are very close, an idea theoretically discussed by F.J. Garcia de Abajo and coworkers. However, it is also quite intuitive that CL and EELS should be different. For example, EELS helps detecting any sort of modes while CL can only detect radiative ones. On the other hand, even between optical spectroscopy techniques, clear differences such as energy shifts or spectral shapes changes are expected in the case of plasmons. The lack of adapted instrumentation capable of performing combined EELS and CL, as well as theoretical developments allowing to account for the generic difference between EELS and CL and their optical counterparts impeached a comprehensive understanding of plasmons physics with the otherwise amazing electron spectroscopies. In this talk, I will present recent experimental results showing combined EELS and CL spectral mapping of plasmonic properties for nanoparticles with several shapes (triangles, cubes, stars...) and composition (gold, silver, aluminum...). Helped with different theoretical tools, I will try to show how these results can be related to their optical counterparts (extinction, scattering), and what type of physical insights can be gained from these combined measurements. Finally, if time allows, pointing the weaknesses of state-of-the-art CL and EELS (in terms of spectral range and/or spectral resolution), I will present EELS results obtained on highly monochromated electron beams that could cope with these limitations

  9. A silicon metal-oxide-semiconductor field-effect transistor Hall bar for scanning Hall probe microscopy.

    PubMed

    Yamaguchi, Akinobu; Saito, Hiromasa; Shimizu, Masayoshi; Miyajima, Hideki; Matsumoto, Satoru; Nakamura, Yoshiharu; Hirohata, Atsufumi

    2008-08-01

    We demonstrate successful operation of a scanning Hall probe microscope with a few micron-size resolution by using a silicon metal-oxide semiconductor field-effect transistor (Si-MOSFET) Hall bar, which is designed to improve not only the mechanical strength but also the temperature stability. The Si-MOSFET micro-Hall probe is cheaper than the current micro-Hall probes and is found to be as sensitive as a micro-Hall probe with GaAs/AlGaAs heterostructure or an epitaxial InSb two-dimensional electron gas. This was used to magnetically image the surface of a Sm(2)Co(17) permanent magnet during the magnetization reversal process as a function of an external magnetic field below 1.5 T. This revealed firm evidence of the presence of the inverse magnetic seed as theoretically predicted earlier. Magnetically pinned centers, with a typical size 80 mum, are observed to persist even under a high magnetic field, clearly indicating the robustness of the Si Hall probe against the field application as well as the repetition of the measurement. PMID:19044353

  10. The Utilization of Spin Polarized Photoelectron Spectroscopy as a Probe of Electron Correlation with an Ultimate Goal of Pu

    SciTech Connect

    Tobin, James; Yu, Sung; Chung, Brandon; Morton, Simon; Komesu, Takashi; Waddill, George

    2008-02-11

    We are developing the technique of spin-polarized photoelectron spectroscopy as a probe of electron correlation with the ultimate goal of resolving the Pu electronic structure controversy. Over the last several years, we have demonstrated the utility of spin polarized photoelectron spectroscopy for determining the fine details of the electronic structure in complex systems such as those shown in the paper.

  11. Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers

    SciTech Connect

    Jana, Dipankar Porwal, S.; Sharma, T. K. Oak, S. M.; Kumar, Shailendra

    2014-04-15

    Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.

  12. Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers

    NASA Astrophysics Data System (ADS)

    Jana, Dipankar; Porwal, S.; Sharma, T. K.; Kumar, Shailendra; Oak, S. M.

    2014-04-01

    Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates.

  13. Pump-probe surface photovoltage spectroscopy measurements on semiconductor epitaxial layers.

    PubMed

    Jana, Dipankar; Porwal, S; Sharma, T K; Kumar, Shailendra; Oak, S M

    2014-04-01

    Pump-probe Surface Photovoltage Spectroscopy (SPS) measurements are performed on semiconductor epitaxial layers. Here, an additional sub-bandgap cw pump laser beam is used in a conventional chopped light geometry SPS setup under the pump-probe configuration. The main role of pump laser beam is to saturate the sub-bandgap localized states whose contribution otherwise swamp the information related to the bandgap of material. It also affects the magnitude of Dember voltage in case of semi-insulating (SI) semiconductor substrates. Pump-probe SPS technique enables an accurate determination of the bandgap of semiconductor epitaxial layers even under the strong influence of localized sub-bandgap states. The pump beam is found to be very effective in suppressing the effect of surface/interface and bulk trap states. The overall magnitude of SPV signal is decided by the dependence of charge separation mechanisms on the intensity of the pump beam. On the contrary, an above bandgap cw pump laser can be used to distinguish the signatures of sub-bandgap states by suppressing the band edge related feature. Usefulness of the pump-probe SPS technique is established by unambiguously determining the bandgap of p-GaAs epitaxial layers grown on SI-GaAs substrates, SI-InP wafers, and p-GaN epilayers grown on Sapphire substrates. PMID:24784628

  14. Compliant head probe for positioning electroencephalography electrodes and near-infrared spectroscopy optodes.

    PubMed

    Giacometti, Paolo; Diamond, Solomon G

    2013-02-01

    A noninvasive head probe that combines near-infrared spectroscopy (NIRS) and electroencephalography (EEG) for simultaneous measurement of neural dynamics and hemodynamics in the brain is presented. It is composed of a compliant expandable mechanism that accommodates a wide range of head size variation and an elastomeric web that maintains uniform sensor contact pressure on the scalp as the mechanism expands and contracts. The design is intended to help maximize optical and electrical coupling and to maintain stability during head movement. Positioning electrodes at the inion, nasion, central, and preauricular fiducial locations mechanically shapes the probe to place 64 NIRS optodes and 65 EEG electrodes following the 10-5 scalp coordinates. The placement accuracy, precision, and scalp pressure uniformity of the sensors are evaluated. A root-mean-squared (RMS) positional precision of 0.89 ± 0.23 mm, percent arc subdivision RMS accuracy of 0.19 ± 0.15%, and mean normal force on the scalp of 2.28 ± 0.88 N at 5 mm displacement were found. Geometric measurements indicate that the probe will accommodate the full range of adult head sizes. The placement accuracy, precision, and uniformity of sensor contact pressure of the proposed head probe are important determinants of data quality in noninvasive brain monitoring with simultaneous NIRS-EEG. PMID:23377012

  15. Probing buried interfaces with standing-wave excited photoelectron spectroscopy and X-ray emission spectroscopy

    NASA Astrophysics Data System (ADS)

    Sell, Brian C.

    The experiments presented in this thesis are based on a few rather simple ideas that, when put together, can yield impressive amounts of information of relevance to nanoscience and nanotechnology. It is with this philosophy in mind that we will work our way through the generation of x-rays to their excitation of photoelectrons and x-rays to their final use to yield information about buried interfaces in a non-destructive manner. As a first idea, a strong soft x-ray standing wave can be created by irradiating a synthetic multilayer with a monochromatized synchrotron radiation beam at its first-order Bragg angle. The standing wave causes a strong modulation of the magnitude of the electric field inside and above the multilayer. This modulation in turn results in a modulation of the intensity of both photoelectrons and secondary x-rays emitted from the sample as a function of the depth of the emitting atoms below the surface. By growing one layer of the sample as a wedge on top of the multilayer and the other uniform-thickness layers of the sample on top of that, we can by translating the focused x-ray beam across the thickness of the wedge probe the stoichiometric and magnetic properties of the overlayers and their respective interfaces. These measured intensities can then be compared to theoretical calculations which include all x-ray optical effects. This standing wave/wedge approach, which we shall also term the "swedge" method, shows considerable promise for studying a variety of nanostructured materials and devices.

  16. Multilevel memristor effect in metal-semiconductor core-shell nanoparticles tested by scanning tunneling spectroscopy

    NASA Astrophysics Data System (ADS)

    Chakrabarti, Sudipto; Pal, Amlan J.

    2015-05-01

    We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility, reversibility, and retentivity of the multilevel memristors. From the normalized density of states (NDOS), we infer that the memristor effect is correlated to a decrease in the transport gap of the nanostructures. We also infer that the memristor effect occurs in the nanostructures due to an increase in the density of available states upon application of a voltage pulse.We have grown gold (Au) and copper-zinc-tin-sulfide (CZTS) nanocrystals and Au-CZTS core-shell nanostructures, with gold in the core and the semiconductor in the shell layer, through a high-temperature colloidal synthetic approach. Following usual characterization, we formed ultrathin layers of these in order to characterize the nanostructures in an ultrahigh-vacuum scanning tunneling microscope. Scanning tunneling spectroscopy of individual nanostructures showed the memristor effect or resistive switching from a low- to a high-conducting state upon application of a suitable voltage pulse. The Au-CZTS core-shell nanostructures also show a multilevel memristor effect with the nanostructures undergoing two transitions in conductance at two magnitudes of voltage pulse. We have studied the reproducibility

  17. Probing the reaction coordinate for ligand binding in hemoglobin using ultrafast transient Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Zhu, Huiping; Lingle, Robert, Jr.; Xu, Xiaobing; Hopkins, John B.

    1993-05-01

    Transient picosecond Raman spectroscopy is capable of differentiating vibrational relaxation from conformational changes by comparing the Stokes and anti-Stokes dynamics. We report pump-probe picosecond Raman experiments on oxy- and deoxyhemoglobin (oxyHb and deoxyHb, respectively) using 8 ps 532 nm pump pulses and 8 ps 355 nm probe pulses. Heme- to-protein vibrational cooling has been directly observed in deoxyHb for the first time, and the deconvolved cooling time constant is measured to be 2 - 5 ps. By applying our mode-specific Stokes and anti-Stokes technique to oxyHb, we find that any geminate recombination of photodeligated O2 must occur in either less than two picoseconds or longer than a nanosecond.

  18. Structural dynamics inside a functionalized metal–organic framework probed by ultrafast 2D IR spectroscopy

    PubMed Central

    Nishida, Jun; Tamimi, Amr; Fei, Honghan; Pullen, Sonja; Ott, Sascha; Cohen, Seth M.; Fayer, Michael D.

    2014-01-01

    The structural elasticity of metal–organic frameworks (MOFs) is a key property for their functionality. Here, we show that 2D IR spectroscopy with pulse-shaping techniques can probe the ultrafast structural fluctuations of MOFs. 2D IR data, obtained from a vibrational probe attached to the linkers of UiO-66 MOF in low concentration, revealed that the structural fluctuations have time constants of 7 and 670 ps with no solvent. Filling the MOF pores with dimethylformamide (DMF) slows the structural fluctuations by reducing the ability of the MOF to undergo deformations, and the dynamics of the DMF molecules are also greatly restricted. Methodology advances were required to remove the severe light scattering caused by the macroscopic-sized MOF particles, eliminate interfering oscillatory components from the 2D IR data, and address Förster vibrational excitation transfer. PMID:25512539

  19. Evaluation of contact status between probe and skin for noninvasive blood sensing with NIR reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Qiu, Qingjun; Xu, Kexin; Jiang, Jingying; Chen, Wen Liang

    2004-07-01

    In non-invasive blood sensing with near-infrared (NIR) reflectance spectroscopy, optical probe usually directly contacts skin to eliminate specular reflection. Due to the direct contact, changes in contact pressure can lead to changes in internal structure and components distribution of the measured site, and thus introduces great interference into the final results. In this paper, we use self-made AOTF spectrophotometer to investigate the changes of reflectance spectrum with changing contact status for tissues in vitro (fresh porcine skin) and in vivo (two volunteers' left palms) at wavelengths ranging from 1100 nm to 1700 nm. The results show that with increasing degree of contact, energy of reflectance spectrum gradually decreases and the trend goes stable with time. However, the decreasing degree is related to wavelengths, which potentially suggests an indirect relevance with changes of components in tissues. Meanwhile, the results provide a practical solution to determining the optimum contact status between probe and skin.

  20. Large area scanning probe microscope in ultra-high vacuum demonstrated for electrostatic force measurements on high-voltage devices

    PubMed Central

    Glatzel, Thilo; Schmölzer, Thomas; Schöner, Adolf; Reshanov, Sergey; Bartolf, Holger; Meyer, Ernst

    2015-01-01

    Summary Background: The resolution in electrostatic force microscopy (EFM), a descendant of atomic force microscopy (AFM), has reached nanometre dimensions, necessary to investigate integrated circuits in modern electronic devices. However, the characterization of conducting or semiconducting power devices with EFM methods requires an accurate and reliable technique from the nanometre up to the micrometre scale. For high force sensitivity it is indispensable to operate the microscope under high to ultra-high vacuum (UHV) conditions to suppress viscous damping of the sensor. Furthermore, UHV environment allows for the analysis of clean surfaces under controlled environmental conditions. Because of these requirements we built a large area scanning probe microscope operating under UHV conditions at room temperature allowing to perform various electrical measurements, such as Kelvin probe force microscopy, scanning capacitance force microscopy, scanning spreading resistance microscopy, and also electrostatic force microscopy at higher harmonics. The instrument incorporates beside a standard beam deflection detection system a closed loop scanner with a scan range of 100 μm in lateral and 25 μm in vertical direction as well as an additional fibre optics. This enables the illumination of the tip–sample interface for optically excited measurements such as local surface photo voltage detection. Results: We present Kelvin probe force microscopy (KPFM) measurements before and after sputtering of a copper alloy with chromium grains used as electrical contact surface in ultra-high power switches. In addition, we discuss KPFM measurements on cross sections of cleaved silicon carbide structures: a calibration layer sample and a power rectifier. To demonstrate the benefit of surface photo voltage measurements, we analysed the contact potential difference of a silicon carbide p/n-junction under illumination. PMID:26885461