Open Access. Powered by Scholars. Published by Universities.®
- Keyword
-
- Atomic force microscopes (6)
- Materials properties (5)
- Adhesion (3)
- Atomic force microscopy (3)
- Calibration (3)
-
- Electron beams (2)
- Mechanical properties (2)
- Scanning probe microscopes (2)
- Amorphous semiconductors， Electron spectroscopy， Silicon ，Infrared spectroscopy，Photoelectron spectroscopy (1)
- Atom surface interactions (1)
- Atomic and molecular beams (1)
- Comparators (1)
- Cratering (1)
- Dynamic mechanical analysis (1)
- Elastic moduli (1)
- Electrochemistry (1)
- Etching (1)
- Field effect transistors (1)
- Frequency doubled lasers (1)
- Friction (1)
- Glass transitions (1)
- Hardness (1)
- II-VI semiconductors (1)
- Isomerization (1)
- Materials analysis (1)
- Materials behavior (1)
- Materials properties， Scanning microscopy， Transducers (1)
- Microelectromechanical systems (1)
- Microoptics (1)
- Milling (1)
Articles 1 - 25 of 25
Full-Text Articles in Engineering
Getting To The Root Of Bacterial Hairs: What Is “S”?, Rebecca Gaddis, Samantha O'Conner, Evan Anderson, Terri Camesano, Nancy Burnham
Getting To The Root Of Bacterial Hairs: What Is “S”?, Rebecca Gaddis, Samantha O'Conner, Evan Anderson, Terri Camesano, Nancy Burnham
Nancy A. Burnham
An atomic force microscope (AFM) was used to measure the steric forces of lipopolysaccharides (LPS) on the biofilm-forming bacteria, Pseudomonas aeruginosa. It is well known that LPS play a vital role in biofilm formation. These forces were characterized with a modified version of the Alexander and de Gennes (AdG) model for polymers, which is a function of equilibrium brush length, L, probe radius, R, temperature, T, separation distance, D, and an indefinite density variable, s. This last parameter was originally distinguished by de Gennes as the root spacing or mesh spacing depending upon the type of polymer adhesion; however since …
Relating The Physical Properties Of Pseudomonas Aeruginosa Lipopolysaccharides To Virulence By Atomic Force Microscopy, Nancy Burnham, Ivan Ivanov, Erica Kintz, Laura Porter, Joanna Goldberg, Terri Camesano
Relating The Physical Properties Of Pseudomonas Aeruginosa Lipopolysaccharides To Virulence By Atomic Force Microscopy, Nancy Burnham, Ivan Ivanov, Erica Kintz, Laura Porter, Joanna Goldberg, Terri Camesano
Nancy A. Burnham
Lipopolysaccharides (LPS) are an important class of macromolecules that are components of the outer membrane of Gram-negative bacteria such as Pseudomonas aeruginosa. P. aeruginosa contains two different sugar chains, the homopolymer common antigen (A band) and the heteropolymer O antigen (B band), which impart serospecificity. The characteristics of LPS are generally assessed after isolation rather than in the context of whole bacteria. Here we used atomic force microscopy (AFM) to probe the physical properties of the LPS of P. aeruginosa strain PA103 (serogroup O11) in situ. This strain contains a mixture of long and very long polymers of O antigen, …
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Quantitative Assessment Of Sample Stiffness And Sliding Friction From Force Curves In Atomic Force Microscopy, Nancy Burnham, Jon Pratt, Gordon Shaw, Lee Kumanchik
Nancy A. Burnham
It has long been recognized that the angular deflection of an atomic force microscope(AFM) cantilever under “normal” loading conditions can be profoundly influenced by the friction between the tip and the surface. It is shown here that a remarkably quantifiable hysteresis occurs in the slope of loading curves whenever the normal flexural stiffness of the AFM cantilever is greater than that of the sample. This situation arises naturally in cantilever-on-cantilever calibration, but also when trying to measure the stiffness of nanomechanical devices or test structures, or when probing any type of surface or structure that is much more compliant along …
Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin
Optimal Roughness For Minimal Adhesion, Nancy Burnham, D-L Liu, J Martin
Nancy A. Burnham
Roughness has a significant affect on adhesion. The authors used a single-asperity model to describe a smooth tip in contact with a rough surface and predicted that an optimal size of asperity yields a minimum of adhesion. Experimentally, adhesive forces on silicon wafers with varying roughness were measured using atomic-force-microscopy cantilevers with varying tip radii. It was found that minima do exist, and for all tip radii, the adhesion falls significantly for roughness greater than 1–2nm and drops at higher roughness for larger tips. This work should help minimize stiction in microelectromechanical systems and progress the understanding of nanoscale-contact mechanics.
Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell
Precision And Accuracy Of Thermal Calibration Of Atomic Force Microscopy Cantilevers, Nancy Burnham, G Matei, E Thoreson, J Pratt, D Newell
Nancy A. Burnham
To have confidence in force measurements made with atomic force microscopes(AFMs), the spring constant of the AFM cantilevers should be known with good precision and accuracy, a topic not yet thoroughly treated in the literature. In this study, we compared the stiffnesses of uncoated tipless uniform rectangular silicon cantilevers among thermal, loading, and geometric calibration methods; loading was done against an artifact from the National Institute of Standards and Technology (NIST). The artifact was calibrated at NIST using forces that were traceable to the International System of units. The precision and accuracy of the thermal method were found to be …
Substrate Rigidity Regulates The Formation And Maintenance Of Tissues, Nancy Burnham, Wei-Hui Guo, Margo Frey, Yu-Li Wang
Substrate Rigidity Regulates The Formation And Maintenance Of Tissues, Nancy Burnham, Wei-Hui Guo, Margo Frey, Yu-Li Wang
Nancy A. Burnham
The ability of cells to form tissues represents one of the most fundamental issues in biology. However, it is unclear what triggers cells to adhere to one another in tissues and to migrate once a piece of tissue is planted on culture surfaces. Using substrates of identical chemical composition but different flexibility, we show that this process is controlled by substrate rigidity: on stiff substrates, cells migrate away from one another and spread on surfaces, whereas on soft substrates they merge to form tissue-like structures. Similar behavior was observed not only with fibroblastic and epithelial cell lines but also explants …
Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson
Standard-Deviation Minimization For Calibrating The Radii Of Spheres Attached To Atomic Force Microscope Cantilevers, Nancy Burnham, E Thoreson
Nancy A. Burnham
We describe an efficient method for determining the radii of spheres attached to atomic force microscope(AFM) cantilevers by minimizing the square root of the square error for a segment of circular arc cross-sectional data. The approach we present has benefits: (1) The method fits a function, with two fitting parameters, to a number of data points, rather than calculating the radius based on two points of cross-sectional data, (2) a fit is performed in a common spreadsheet application, using a solving feature, and (3) spheres of diameters 2 to 60 μm were measured to an accuracy of 9% and a …
Apparatus For Illuminating The Tip-Sample Interface Of An Atomic Force Microscope, Nancy Burnham, E Thoreson
Apparatus For Illuminating The Tip-Sample Interface Of An Atomic Force Microscope, Nancy Burnham, E Thoreson
Nancy A. Burnham
An apparatus for the delivery of radiation to the tip-sample interface of an atomic force microscope(AFM) is demonstrated. The pulsed light delivery system (PLDS) was fabricated to probe photoinduced conformational changes of molecules using an AFM. The system is 67 mm long, 59 mm wide, and 21 mm high, leaving clearance to mount the PLDS and a microscope slide coated with a thin film of photoactive molecules beneath the cantilever tip of a stand-alone AFM. The PLDS is coupled into a fiber pigtailed Nd:yttrium–aluminum–garnetfrequency doubled laser, operating at a wavelength of 532 nm. The radiation delivered to a sample through …
Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet
Phase Imaging: Deep Or Superficial?, Nancy Burnham, O Behrend, L Odoni, J Loubet
Nancy A. Burnham
Phase images acquired while intermittently contacting a sample surface with the tip of an atomic force microscope cantilever are not easy to relate to material properties. We have simulated dynamic force curves and compared simulated with experimental results. For some cantilever–sample combinations, the interaction remains a surface effect, whereas for others, the tip penetrates the sample significantly. Height artifacts in the “topography” images, and the role of the sample stiffness, work of adhesion, damping, and topography in the cantilever response manifest themselves to different extents depending on the indentation depth.
Elastic And Shear Moduli Of Single-Walled Carbon Nanotube Ropes, Nancy Burnham, Jean-Paul Salvetat, G Andrew D Briggs, Jean-Marc Bonard, Revathi Bacsa, Andrzej Kulik, Thomas Stöckli, László Forró
Elastic And Shear Moduli Of Single-Walled Carbon Nanotube Ropes, Nancy Burnham, Jean-Paul Salvetat, G Andrew D Briggs, Jean-Marc Bonard, Revathi Bacsa, Andrzej Kulik, Thomas Stöckli, László Forró
Nancy A. Burnham
Carbon nanotubes are believed to be the ultimate low-density high-modulus fibers, which makes their characterization at nanometer scale vital for applications. By using an atomic force microscope and a special substrate, the elastic and shear moduli of individual single-walled nanotube (SWNT) ropes were measured to be of the order of 1 TPa and 1 GPa, respectively. In contrast to multiwalled nanotubes, an unexpectedly low intertube shear stiffness dominated the flexural behavior of the SWNT ropes. This suggests that intertube cohesion should be improved for applications of SWNT ropes in high-performance composite materials.
Local Mechanical Spectroscopy With Nanometer-Scale Lateral Resolution, Nancy Burnham, F Oulevey, G Gremaud, A Semoroz, Aj Kulik, E Dupas, D Gourdon
Local Mechanical Spectroscopy With Nanometer-Scale Lateral Resolution, Nancy Burnham, F Oulevey, G Gremaud, A Semoroz, Aj Kulik, E Dupas, D Gourdon
Nancy A. Burnham
A new technique has been developed to probe the viscoelastic and anelastic properties of submicron phases of inhomogeneous materials. The measurement gives information related to the internal friction and to the variations of the dynamic modulus of nanometer-sized volumes. It is then the nanoscale equivalent to mechanical spectroscopy, a well-known macroscopic technique for materials studies, also sometimes called dynamic mechanical (thermal) analysis. The technique is based on a scanning force microscope, using the principle of scanning local-acceleration microscopy (SLAM), and allows the sample temperature to be changed. It is called variable-temperature SLAM, abbreviated T-SLAM. According to a recent proposition to …
Friction Anisotropy And Asymmetry Of A Compliant Monolayer Induced By A Small Molecular Tilt, Nancy Burnham, M Liley, D. Gourdon, Dimitrios Stamou, U Meseth, T Fischer, C Lautz, H Stahlberg, H Vogel, C Duschl
Friction Anisotropy And Asymmetry Of A Compliant Monolayer Induced By A Small Molecular Tilt, Nancy Burnham, M Liley, D. Gourdon, Dimitrios Stamou, U Meseth, T Fischer, C Lautz, H Stahlberg, H Vogel, C Duschl
Nancy A. Burnham
Lateral force microscopy in the wearless regime was used to study the friction behavior of a lipid monolayer on mica. In the monolayer, condensed domains with long-range orientational order of the lipid molecules were present. The domains revealed unexpectedly strong friction anisotropies and non-negligible friction asymmetries. The angular dependency of these effects correlated well with the tilt direction of the alkyl chains of the monolayer, as determined by electron diffraction and Brewster angle microscopy. The molecular tilt causing these frictional effects was less than 15 degrees, demonstrating that even small molecular tilts can make a major contribution to friction.
Scanning Local‐Acceleration Microscopy, Nancy Burnham, A. Kulik, G. Gremaud, P. Gallo, F. Oulevey
Scanning Local‐Acceleration Microscopy, Nancy Burnham, A. Kulik, G. Gremaud, P. Gallo, F. Oulevey
Nancy A. Burnham
By adapting a scanning force microscope to operate at frequencies above the highest tip–sample resonance, the sensitivity of the microscope to materials’ properties is greatly enhanced. The cantilever’s behavior in response to high‐frequency excitation from a transducer underneath the sample is fundamentally different than to its low‐frequency response. In this article, the motivations, instrumentation, theory, and first results for this technique are described.
Materials’ Properties Measurements: Choosing The Optimal Scanning Probe Microscope Configuration, Nancy Burnham, G Gremaud, A Kulik, P Gallo, F Oulevey
Materials’ Properties Measurements: Choosing The Optimal Scanning Probe Microscope Configuration, Nancy Burnham, G Gremaud, A Kulik, P Gallo, F Oulevey
Nancy A. Burnham
Rheological models are used to represent different scanning probe microscope configurations. The solutions for their static and dynamic behavior are found and used to analyze which scanning probe microscope configuration is best for a given application. We find that modulating the sample at high frequencies results in the best microscope behavior for measuring the stiffness of rigid materials, and that by modulating the tip at low frequencies and detecting the motion of the tip itself (not its position relative to the tip holder) should be best for studying compliant materials in liquids.
Nanosubharmonics: The Dynamics Of Small Nonlinear Contacts, Nancy Burnham, A Kulik, G Gremaud, Gad Briggs
Nanosubharmonics: The Dynamics Of Small Nonlinear Contacts, Nancy Burnham, A Kulik, G Gremaud, Gad Briggs
Nancy A. Burnham
We observed the generation of subharmonics and chaos in a nanometer-sized mechanical contact. To first order, the behavior matches that of macroscopic systems, with some intriguing secondary differences. As the occurrence of periodic behavior (subharmonics) is related to the coefficient of restitution, it may be possible to image local energy dissipation with nanometer resolution.
Accounting For The Stiffnesses Of The Probe And Sample In Scanning Probe Microscopy*, Nancy Burnham
Accounting For The Stiffnesses Of The Probe And Sample In Scanning Probe Microscopy*, Nancy Burnham
Nancy A. Burnham
The elements of a scanning probe microscope are modeled as a set of springs in series. For a single‐component sample, that is, a sample consisting of only one material, the detected feature height in variable force (force microscopy) or variable current (tunneling microscopy) modes is a function of the total system stiffness and the stiffness of the detector. For a multicomponent sample, the data in both variable force (current) and constant force (current) modes are modified by the set‐point force, the detector stiffness, and the relative stiffnesses of the components of the sample. A detection scheme for reducing this compliance …
Burnham, Colton, And Pollock Reply, Nancy Burnham, Rj Colton, Hm Pollock
Burnham, Colton, And Pollock Reply, Nancy Burnham, Rj Colton, Hm Pollock
Nancy A. Burnham
It is not necessary to obtain permission to reuse this article or its components as it is available under the terms of the Creative Commons Attribution 3.0 License. This license permits unrestricted use, distribution, and reproduction in any medium, provided attribution to the author (s) and the published article's title, journal citation, and DOI are maintained. Please note that some figures may have been included with permission from other third parties. It is your responsibility to obtain the proper permission from the rights holder
Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock
Work-Function Anisotropies As An Origin Of Long-Range Surface Forces, Nancy Burnham, R Colton, H Pollock
Nancy A. Burnham
Unusual effects noticed in previous force microscopy data are explained by a model based on work-function anisotropies and their associated patch charges. Measurable forces between macroscopic bodies can be due to the interaction of patch charges, with important consequences in the fields of surface forces, contact mechanics, adhesion, Schottky barriers, and the surface properties of insulators.
Interpretation Issues In Force Microscopy, Nancy Burnham, Richard Colton, Hubert Pollock
Interpretation Issues In Force Microscopy, Nancy Burnham, Richard Colton, Hubert Pollock
Nancy A. Burnham
In this paper, we will discuss force microscopy (FM) and its potential for determining mechanical properties of thin films. We will introduce the basic principles of FM, and demonstrate how FM can be used to determine materials properties as well as image surface topography, both with nanonewton or sub‐nanonewton force resolution and sub‐nanometer position resolution. As FM is still a new field, not all of the questions concerning interpretation have been fully answered. We will elucidate four current issues that must be resolved before the full potential of FM can be realized. They are: (1) the role of water vapor …
On The Electrochemical Etching Of Tips For Scanning Tunneling Microscopy, Nancy Burnham, J. Ibe, P. Bey Jr., S. Brandow, R. Brizzolara, D. Dilella, K. Lee, C. K. Marrian, R. Colton
On The Electrochemical Etching Of Tips For Scanning Tunneling Microscopy, Nancy Burnham, J. Ibe, P. Bey Jr., S. Brandow, R. Brizzolara, D. Dilella, K. Lee, C. K. Marrian, R. Colton
Nancy A. Burnham
The sharpness of tips used in scanning tunneling microscopy(STM) is one factor which affects the resolution of the STM image. In this paper, we report on a direct‐current (dc) drop‐off electrochemicaletching procedure used to sharpen tips for STM. The shape of the tip is dependent on the meniscus which surrounds the wire at the air–electrolyte interface. The sharpness of the tip is related to the tensile strength of the wire and how quickly the electrochemical reaction can be stopped once the wire breaks. We have found that the cutoff time of the etch circuit has a significant effect on the …
Probing The Surface Forces Of Monolayer Films With An Atomic-Force Microscope, Nancy Burnham, Dawn Dominguez, Robert Mowery, Richard Colton
Probing The Surface Forces Of Monolayer Films With An Atomic-Force Microscope, Nancy Burnham, Dawn Dominguez, Robert Mowery, Richard Colton
Nancy A. Burnham
Using an atomic force microscope (AFM), we have studied the attractive and adhesive forces between a cantilever tip and sample surfaces as a function of sample surface energy. The measured forces systematically increased with surface energy. The AFM is very sensitive; changes in the surface forces (i.e., attraction and adhesion) of monolayer covered samples could be clearly discerned when only the surface group of the monolayer film was changed from -CH3 to -CF3.
Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton
Measuring The Nanomechanical Properties And Surface Forces Of Materials Using An Atomic Force Microscope, Nancy Burnham, Richard Colton
Nancy A. Burnham
An atomic force microscope(AFM) has been configured so that it measures the force between a tip mounted on a cantilever beam and a sample surface as a function of the tip–surface separation. This allows the AFM to study both the nanomechanical properties of the sample and the forces associated with the tip–surface interaction. More specifically, the AFM can measure the elastic and plastic behavior and hardness via nanoindentation,van der Waals forces, and the adhesion of thin‐film and bulk materials with unprecedented force and spatial resolution. The force resolution is currently 1 nanonewton, and the depth resolution is 0.02 nm. Additionally, …
Electron Beam Effects In The Analysis Of Compound Semiconductors And Devices, Nancy Burnham, Ll Kazmerski, Ab Swartzlander, Aj Nelson, Se Asher
Electron Beam Effects In The Analysis Of Compound Semiconductors And Devices, Nancy Burnham, Ll Kazmerski, Ab Swartzlander, Aj Nelson, Se Asher
Nancy A. Burnham
The effects of electron beams on the analysis of CuInSe2surfaces are examined in this paper. Potential changes in the surface chemistry—including oxidation and desorption—under a range of incident probe conditions, are investigated for possible artifactual information generation. Emphasis is placed on the relationships between beam conditions and oxygen chemisorption and physisorption, since oxygen treatments of devices utilizing this semiconductor are critical to performance. Single crystals and polycrystalline thin films are analyzed and compared to establish the beam‐induced phenomena.
Electron Energy‐Loss Spectroscopy Study Of Hydrogenated Amorphous Silicon, Nancy Burnham, Rf Fisher, Se Se, Ll Kazmerski
Electron Energy‐Loss Spectroscopy Study Of Hydrogenated Amorphous Silicon, Nancy Burnham, Rf Fisher, Se Se, Ll Kazmerski
Nancy A. Burnham
Electron energy‐loss spectroscopy is used to study hydrogenated amorphous silicon (a‐Si:H). Core‐level and plasma excitations were examined as a function of hydrogen content. This technique and its interpretation reveals a consistent picture of the electron excitations within this important material. The a‐Si:H thin films were fabricated by rf sputtering. Their hydrogen concentrations ranged from 0% to 15%. Hydrogen content was determined by infrared spectroscopy and secondary ion mass spectroscopy. X‐ray photoelectron spectroscopy and inspection of the silicon Auger‐K L L peak confirmed the silicon core levels.
Scanning Auger Microprobe Studies Of Ball Cratered Cds/Cuinse2 Solar Cells, Nancy Burnham, Ll Levenson, Rj Matson, R Noufi, Ll Kazmerski
Scanning Auger Microprobe Studies Of Ball Cratered Cds/Cuinse2 Solar Cells, Nancy Burnham, Ll Levenson, Rj Matson, R Noufi, Ll Kazmerski
Nancy A. Burnham
CdS/CuInSe2solar cell films are typically several micrometers thick. Composition profiles of these films are usually carried out on fracture cross sections by scanning Auger microscopy or by recording Auger spectra during ion milling. For fracture cross sections, the depth resolution depends on the electron beam diameter and the roughness of the fracture surface. Ion milling is time consuming, and artifacts are caused by ion beam faceting. Ball cratering requires only a fraction of an hour and provides significant magnification of the film cross section. There is sufficient contrast, both in optical and electron microscopy, to distinguish between CdS and CuInSe2 …