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138 results on '"Kjoller, Kevin"'

1. Time dynamics of photothermal vs optoacoustic response in mid IR nanoscale biospectroscopy

Author

Tovee, Peter D., Tinker-Mill, Claire, Kjoller, Kevin, Allsop, David, Weightman, Peter, Surman, Mark, Siggel-King, Michele R. F., Wolski, Andy, and Kolosov, Oleg V.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Physics - Optics
Abstract

Infrared (IR) spectroscopy, a well established tool for chemical analysis of diverse materials, has significant potential in biomedical applications. While the spatial resolution of traditional IR spectroscopy is limited by the wavelength of the IR light to the few micrometres, it has been shown that nanoscale chemical analysis can be obtained by detecting IR induced local heating photothermal response via Scanning Thermal Microscopy (SThM) or local thermomechanical expansion using Atomic Force Microscopy (AFM). This paper explores the potential of a pulsed ps pulse duration high power free electron laser (FEL) light source for AFM-IR and SThM-IR spectroscopy employing standard AFM and SThM probes. The SThM-IR response was found to have a detrimental strong background signal due to the direct heating of the probe, whereas the AFM IR thermomechanical response allowed to eliminate such a problem for both top down and bottom up illuminations with the FEL IR source. The SThM IR characteristic response time was approximately half that of AFM-IR, in line with finite element analysis simulations. Finally, the advantages and drawbacks of AFM-IR wavelength sensitive spectroscopic response using a ps duration FEL vs a high repetition quantum cascade laser IR source in studies of nanoscale dimension amyloid peptide fibres were explored both experimentally and via finite elements analysis.

Published
2015

2. Nanoscale spatial resolution probes for Scanning Thermal Microscopy of solid state materials

Author

Tovee, P., Pumarol, M., Zeze, D., Kjoller, Kevin, and Kolosov, O.

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Condensed Matter - Other Condensed Matter
Abstract

Scanning Thermal Microscopy (SThM) uses micromachined thermal sensors integrated in a force sensing cantilever with a nanoscale tip can be highly useful for exploration of thermal management of nanoscale semiconductor devices. As well as mapping of surface properties of related materials. Whereas SThM is capable to image externally generated heat with nanoscale resolution, its ability to map and measure thermal conductivity of materials has been mainly limited to polymers or similar materials possessing low thermal conductivity in the range from 0.1 to 1 W/mK, with lateral resolution on the order of 1 \mum. In this paper we use linked experimental and theoretical approaches to analyse thermal performance and sensitivity of the micromachined SThM probes in order to expand their applicability to a broader range of nanostructures from polymers to semiconductors and metals. We develop physical models of interlinked thermal and electrical phenomena in these probes and then validate these models using experimental measurements of the real probes, which provided the basis for analysing SThM performance in exploration of nanostructures. Our study then highlights critical features of these probes, namely, the geometrical location of the thermal sensor with respect to the probe apex, thermal conductance of the probe to the support base, heat conduction to the surrounding gas, and the thermal conductivity of tip material adjacent to the apex. It is furthermore allows us to propose a novel design of the SThM probe that incorporates a carbon nanotube (CNT) or similar high thermal conductivity graphene sheet material positioned near the probe apex. The new sensor is predicted to provide spatial resolution to the thermal properties of nanostructures on the order of few tens of nm, as well as to expand the sensitivity of the SThM probe to materials with heat conductivity values up to 100-1000 W/mK.

Published
2011
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10. Resonance-enhanced nanoscale IR spectroscopy of ultrathin films and monolayers on metals

Author

Marcott, Curtis, Lu, Feng, Jin, Mingzhou, Belkin, Mikhail A., Yang, Honghua, Prater, Craig B., and Kjoller, Kevin

Subjects
Monomolecular films, Chemistry, Engineering and manufacturing industries, Physics, Science and technology
Abstract

Infrared (IR) microspectroscopy provides a powerful capability for chemically characterizing materials at spatial resolutions down to 5-10 [Jim. Commercial Fourier transform infrared (FT-IR) spectrometers equipped with microscopes or other microsampling [...]

Published
2014

13. Nanoscale IR spectroscopy: AFM-IR -- a new technique

Author

Marcott, Curtis, Kjoller, Kevin, Lo, Michael, Prater, Craig, Shetty, Roshan, and Dazzi, Alexandre

Subjects
Polymers -- Methods, Atomic force microscopy -- Methods, Spectrum analysis -- Methods, Chemistry, Engineering and manufacturing industries, Physics, Science and technology
Abstract

The combination of atomic force microscopy (AFM) and infrared (IR) spectroscopy in the technique of AFM-IR is one of the most important recent developments in the field of IR microspectroscopy [...]

Published
2012

15. Transition temperature microscopy: Probing thermal properties of coatings and multilayer films at the micro-and nanoscale

Author

Germinarto, Louis T., Schoff, Clifford K., Kjoller, Kevin, Prater, Craig, and Sahagian, Khoren

Subjects
Coatings industry -- Thermal properties, Microscope and microscopy -- Thermal properties, Coatings -- Thermal properties, Business, Chemicals, plastics and rubber industries
Abstract

Transition temperature microscopy (TTM) is a novel local thermal analysis technique that maps spatial variations in thermal properties on length scales from millimeters to nanometers. Traditional bulk thermal analysis provides [...]

Published
2010

17. Recent developments in profiling optical surfaces

Author

Bennett, Jean M., Elings, Virgil, and Kjoller, Kevin

Subjects
Optical measurements -- Innovations, Surfaces (Technology) -- Research, Surface roughness -- Measurement, Astronomy, Physics
Abstract

To understand better the fabrication of optical surfaces and to be able to produce smoother, lower-scatter surfaces, we need to extend characterization techniques to shorter and longer surface spatial wavelengths beyond the conventional 1-micrometer to 1-mm region. Scanning probe microscopes are now available for profiling optical surfaces with height and lateral resolutions of a few atomic spacings. In this paper we report on measurements made with a Nanoscope II atomic force microscope on a variety of supersmooth optical surfaces and compare these results with measurements made with a conventional stylus profiling instrument. Consistent results have been obtained. To cover the long-spatial-wavelength region, long-scan profilers can be used to measure surface waviness in the range from a few millimeters to a few centimeters with height sensitivities approximately 10 times better than conventional interferometers. The characterization of a Nanostep long-scan mechanical profiler is described, and examples of surface profiles taken on selected flat samples are given.

Published
1993

19. Widefield Super-Resolution Infrared Spectroscopy and Imaging of Autofluorescent Biological Materials and Photosynthetic Microorganisms Using Fluorescence Detected Photothermal Infrared (FL-PTIR)

Author

Prater, Craig B., Kjoller, Kevin J., Stuart, Andrew P.D., Grigg, David A., ‘Limurn, Rinuk, and Gough, Kathleen M.

Abstract

We have demonstrated high-speed, super-resolution infrared (IR) spectroscopy and chemical imaging of autofluorescent biomaterials and organisms using camera-based widefield photothermal detection that takes advantage of temperature-dependent modulations of autofluorescent emission. A variety of biological materials and photosynthetic organisms exhibit strong autofluorescence emission under ultraviolet excitation and the autofluorescent emission has a very strong temperature dependence, of order 1%/K. Illuminating a sample with pulses of IR light from a wavelength-tunable laser source causes periodic localized sample temperature increases that result in a corresponding transient decrease in autofluorescent emission. A low-cost light-emitting diode-based fluorescence excitation source was used in combination with a conventional fluorescence microscopy camera to detect localized variations in autofluorescent emission over a wide area as an indicator of localized IR absorption. IR absorption image stacks were acquired over a range of IR wavelengths, including the fingerprint spectral range, enabling extraction of localized IR absorption spectra. We have applied widefield fluorescence detected photothermal IR (FL-PTIR) to an analysis of autofluorescent biological materials including collagen, leaf tissue, and photosynthetic organisms including diatoms and green microalgae cells. We have also demonstrated the FL-PTIR on live microalgae in water, demonstrating the potential for label-free dynamic chemical imaging of autofluorescent cells. [ABSTRACT FROM AUTHOR]

Published
2024
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20. AFM improves resolution of IR spectroscopy: combining infrared spectroscopy with probe microscopy provides a powerful new analytical instrument capable of simultaneous nanoscale chemical and physical analysis of materials

Author

Prater, Craig, Kjoller, Kevin, Shetty, Roshan, and Dazzi, Alexandre

Subjects
Infrared spectroscopy -- Thermal properties -- Investigations, Atomic force microscopy -- Thermal properties -- Investigations, Analytical instruments -- Thermal properties -- Investigations, Company legal issue, Business, Electronics and electrical industries
Abstract

The atomic force microscope (AFM) has been enormously successful addressing nanoscale measurement problems in basic research, materials science, and engineering. In fact, the AFM is credited with enabling multibillion-dollar research [...]

Published
2011

26. The importance of correcting for variable probe–sample interactions in AFM-IR spectroscopy: AFM-IR of dried bacteria on a polyurethane film

Author

Barlow, Daniel E., primary, Biffinger, Justin C., additional, Cockrell-Zugell, Allison L., additional, Lo, Michael, additional, Kjoller, Kevin, additional, Cook, Debra, additional, Lee, Woo Kyung, additional, Pehrsson, Pehr E., additional, Crookes-Goodson, Wendy J., additional, Hung, Chia-Suei, additional, Nadeau, Lloyd J., additional, and Russell, John N., additional

Published
2016
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31. 'Nanoscale Thermal Analysis of Multilayer Thin Films for Packaging using the New Mode of Heated Tip-AFM

Author

Gotzen, Nicolaas-Alexander, Van Assche, Guy, King, William P., Kjoller, Kevin, Shetty, Roshan, and Materials and Chemistry

Subjects
microTA, nanoTA
Abstract

In this paper we compare Wollaston and silicon probes for localized thermal analysis measurements (LTA) on biaxially oriented polypropylene (BOPP) films. Up till now, no real comparison was reported in literature between the different transition temperatures measured using Wollaston and silicon probes. Using different types of probes for studying the same material proves to be very interesting. Using the Wollaston probe, the thermal properties and thickness of a 1 mu thick skin layer can be determined by through-thickness local thermal analysis measurements. The improved resolution of the silicon probes, enables the measurement of thermal properties of individual layers in a cross sectioned film, even for layers of only 1 mu thickness. Based on the results, the silicon probes seem to be more sensitive toward the start of the melting process, since the silicon probe already penetrates at lower temperature, as compared to the Wollaston probes. This sensitivity can be exploited for studying the effect of variations in thermal history between or within samples.

Published
2007

33. Micro- and Nanothermal analysis of pharma materials

Author

Harding, Ljiljana, Reading, Mike, Craig, Duncan, Kjoller, Kevin, Gotzen, Nicolaas-Alexander, and Physical Chemistry and Polymer Science

Subjects
nano-TA
Abstract

Thermal methods are one of the fundamental tools available to pharmaceutical materials scientists and have been widely used for many years for the characterisation of pharmaceutical materials. Conventional thermal techniques, such as DSC (differential scanning calorimetry) and MTDSC (modulated temperature DSC) are well established and extensively used; however, it should be borne in mind that, as bulk measurement techniques, they provide results that represent the sum of all the constituents in the specimen, with the thermal response often being dominated by the higher concentration material. Furthermore, such methods provide no information on the size, shape or spatial distribution of constituents within a multicomponent system. Micro/Nano thermal analysis (MTA/nano-TA) overcomes these disadvantages by combining atomic force microscopy (AFM) with thermal methods of analysis. The principle of MTA is based on performing highly localised material property characterisationon a micrometre to a sub-micrometre scale on a sample subjected to a controlled temperature programme using a heated tip.

Published
2006

38. Nanoscale spatial resolution probes for scanning thermal microscopy of solid state materials

Author

Tovee, P., Pumarol Crestar, Manuel, Zeze, D., Kjoller, Kevin, Kolosov, O., Tovee, P., Pumarol Crestar, Manuel, Zeze, D., Kjoller, Kevin, and Kolosov, O.

Abstract

Scanning thermal microscopy (SThM) uses micromachined thermal sensors integrated in a force sensing cantilever with a nanoscale tip that can be highly useful for exploration of thermal management of nanoscale semiconductor devices as well as mapping of surface and subsurface properties of related materials. Whereas SThM is capable to image externally generated heat with nanoscale resolution, its ability to map and measure thermal conductivity of materials has been mainly limited to polymers or similar materials possessing low thermal conductivity in the range from 0.1 to 1 W m(-1) K-1, with lateral resolution on the order of 1 mu m. In this paper, we use linked experimental and theoretical approaches to analyse thermal performance and sensitivity of the micromachined SThM probes in order to expand their applicability to a broader range of nanostructures from polymers to semiconductors and metals. We develop physical models of interlinked thermal and electrical phenomena in these probes and their interaction with the sample on the mesoscopic length scale of few tens of nm and then validate these models using experimental measurements of the real probes, which provided the basis for analysing SThM performance in exploration of nanostructures. Our study then highlights critical features of these probes, namely, the geometrical location of the thermal sensor with respect to the probe apex, thermal conductance of the probe to the support base, heat conduction to the surrounding gas, and the thermal conductivity of tip material adjacent to the apex. It furthermore allows us to propose a novel design of the SThM probe that incorporates a multiwall carbon nanotube or similar high thermal conductivity graphene sheet material with longitudinal dimensions on micrometre length scale positioned near the probe apex that can provide contact areas with the sample on the order of few tens of nm. The new sensor is predicted to provide greatly improved spatial resolution to thermal pr

Published
2012

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