The Experts below are selected from a list of 39258 Experts worldwide ranked by ideXlab platform

Alan R Champneys - One of the best experts on this subject based on the ideXlab platform.

  • modelling oscillatory flexure modes of an Atomic Force Microscope cantilever in contact mode whilst imaging at high speed
    Nanotechnology, 2012
    Co-Authors: Oliver D Payton, Loren Picco, Mervyn J Miles, Martin Homer, Alan R Champneys
    Abstract:

    Understanding the modal response of an Atomic Force Microscope is important for the identification of image artefacts captured using contact-mode Atomic Force microscopy (AFM). As the scan rate of high speed AFM increases, these modes present themselves as ever clearer noise patterns as the frequency of cantilever vibration falls under the frequency of pixel collection. An Euler–Bernoulli beam equation is used to simulate the flexural modes of the cantilever of an Atomic Force Microscope as it images a hard surface in contact mode. Theoretical results are compared with experimental recordings taken in the high speed regime, as well as previous analytical results. It is shown that the model can capture the mode shapes and resonance properties of the first four eigenmodes.

Tomohiro Machida - One of the best experts on this subject based on the ideXlab platform.

  • Fabrication of graphene nanoribbon by local anodic oxidation lithography using Atomic Force Microscope
    Applied Physics Letters, 2009
    Co-Authors: Shinsuke Masubuchi, Katsutoshi Hirakawa, M. Ono, K. Yoshida, Tomohiro Machida
    Abstract:

    We conducted local anodic oxidation (LAO) lithography in single-layer, bilayer, and multilayer graphenes using tapping-mode Atomic Force Microscope. The width of insulating oxidized area depends systematically on the number of graphene layers. An 800-nm-wide bar-shaped device fabricated in single-layer graphene exhibits the half-integer quantum Hall effect. We also fabricated a 55-nm-wide graphene nanoribbon (GNR). The conductance of the GNR at the charge neutrality point was suppressed at low temperature, which suggests the opening of an energy gap due to lateral confinement of charge carriers. These results show that LAO lithography is an effective technique for the fabrication of graphene nanodevices.

John E Sader - One of the best experts on this subject based on the ideXlab platform.

  • spring constant calibration of Atomic Force Microscope cantilevers of arbitrary shape
    Review of Scientific Instruments, 2012
    Co-Authors: John E Sader, Paul Mulvaney, Julian A Sanelli, Brian D Adamson, J P Monty, Simon Crawford, James Friend, Ivan Marusic, Evan J Bieske
    Abstract:

    The spring constant of an Atomic Force Microscope cantilever is often needed for quantitative measurements. The calibration method of Sader et al. [Rev. Sci. Instrum. 70, 3967 (1999)]10.1063/1.1150021 for a rectangular cantilever requires measurement of the resonant frequency and quality factor in fluid (typically air), and knowledge of its plan view dimensions. This intrinsically uses the hydrodynamic function for a cantilever of rectangular plan view geometry. Here, we present hydrodynamic functions for a series of irregular and non-rectangular Atomic Force Microscope cantilevers that are commonly used in practice. Cantilever geometries of arrow shape, small aspect ratio rectangular, quasi-rectangular, irregular rectangular, non-ideal trapezoidal cross sections, and V-shape are all studied. This enables the spring constants of all these cantilevers to be accurately and routinely determined through measurement of their resonant frequency and quality factor in fluid (such as air). An approximate formulation of the hydrodynamic function for microcantilevers of arbitrary geometry is also proposed. Implementation of the method and its performance in the presence of uncertainties and non-idealities is discussed, together with conversion factors for the static and dynamic spring constants of these cantilevers. These results are expected to be of particular value to the design and application of micro- and nanomechanical systems in general.

  • general scaling law for stiffness measurement of small bodies with applications to the Atomic Force Microscope
    Journal of Applied Physics, 2005
    Co-Authors: John E Sader, Jessica Pacifico, Christopher P Green, Paul Mulvaney
    Abstract:

    A general scaling law connecting the stiffness and dissipative properties of a linear mechanical oscillator immersed in a viscous fluid is derived. This enables the noninvasive experimental determination of the stiffness of small elastic bodies of arbitrary shape by measuring their resonant frequency and quality factor in fluid (typically air). In so doing, we elucidate the physical basis of the method of Sader et al. [Rev. Sci. Instrum. 70, 3967 (1999)] for determining the stiffness of rectangular Atomic Force Microscope cantilevers, and discuss its applicability. The validity of the derived general technique is demonstrated by calibrating Atomic Force Microscope cantilevers with complex geometries, and its implications to small bodies in general are discussed.

  • calibration of rectangular Atomic Force Microscope cantilevers
    Review of Scientific Instruments, 1999
    Co-Authors: John E Sader, James W M Chon, Paul Mulvaney
    Abstract:

    A method to determine the spring constant of a rectangular Atomic Force Microscope cantilever is proposed that relies solely on the measurement of the resonant frequency and quality factor of the cantilever in fluid (typically air), and knowledge of its plan view dimensions. This method gives very good accuracy and improves upon the previous formulation by Sader et al. [Rev. Sci. Instrum. 66, 3789 (1995)] which, unlike the present method, requires knowledge of both the cantilever density and thickness.

  • parallel beam approximation for v shaped Atomic Force Microscope cantilevers
    Review of Scientific Instruments, 1995
    Co-Authors: John E Sader
    Abstract:

    Due to its simplicity, the parallel beam approximation (PBA) is commonly used in the analytical evaluation of the spring constant of V‐shaped Atomic Force Microscope (AFM) cantilevers. However, the point of contention regarding the validity of the PBA is as yet an unresolved issue, which has been exacerbated by some recent contradictory reports. In this paper, we present a detailed investigation of the deflection properties of the V‐shaped AFM cantilever, and in so doing, show that the PBA is in fact a valid and accurate approximation, provided the width and length of the parallel rectangular arms are chosen appropriately. As a direct consequence of this finding, we obtain exceedingly simple yet accurate formulas for the V‐shaped cantilever, which will be of value to the users of the AFM.

  • theoretical analysis of the static deflection of plates for Atomic Force Microscope applications
    Journal of Applied Physics, 1993
    Co-Authors: John E Sader, Lee R White
    Abstract:

    The analysis of the static deflection of cantilever plates is of fundamental importance in application to the Atomic Force Microscope (AFM). In this paper we present a detailed theoretical study of the deflection of such cantilevers. This shall incorporate the presentation of approximate analytical methods applicable in the analysis of arbitrary cantilevers, and a discussion of their limitations and accuracies. Furthermore, we present results of a detailed finite element analysis for a current AFM cantilever, which will be of value to the users of the AFM.

Seizo Morita - One of the best experts on this subject based on the ideXlab platform.

  • contrast of Atomic resolution images from a noncontact ultrahigh vacuum Atomic Force Microscope
    Japanese Journal of Applied Physics, 1995
    Co-Authors: Masahiro Ohta, Hitoshi Ueyama, Yasuhiro Sugawara, Seizo Morita
    Abstract:

    Contrast variations of Atomic-resolution images were investigated on an InP(110) surface using an ultrahigh-vacuum Atomic Force Microscope (UHV-AFM) in the noncontact mode. The contrast of the Atomic-scale AFM image suddenly changed during scanning, which seems to be due to the positional change of the atoms on the tip apex. We observed Atomic-scale point defects. These phenomena seem to occur only in monoAtomic tip-sample interaction. We also observed an Atomic-scale dark area which seems to be due to the convolution of the Atomically flat tip and point defects.

  • Atomically resolved inp 110 surface observed with noncontact ultrahigh vacuum Atomic Force Microscope
    Japanese Journal of Applied Physics, 1995
    Co-Authors: Hitoshi Ueyama, Masahiro Ohta, Yasuhiro Sugawara, Seizo Morita
    Abstract:

    Atomic resolution imaging of the cleaved InP(110) surface was demonstrated using an ultrahigh vacuum Atomic Force Microscope (UHV-AFM) in a noncontact mode, for the first time. The Force gradient acting on the tip was detected by the frequency modulation (FM) detection method. A rectangular lattice could be clearly resolved. Atomic defects were also clearly and reproducibly observed. These results suggest that the noncontact UHV-AFM has potential for imaging III-V compound semiconductor surfaces with true Atomic-scale lateral resolution.

D F Ogletree - One of the best experts on this subject based on the ideXlab platform.

  • electronic contribution to friction on gaas an Atomic Force Microscope study
    Physical Review B, 2008
    Co-Authors: Yabing Qi, Miquel Salmeron, Bas Hendriksen, D F Ogletree, Jeong Young Park
    Abstract:

    The electronic contribution to friction at semiconductor surfaces was investigated by using a Pt-coated tip with 50 nm radius in an Atomic Force Microscope sliding against an $n$-type GaAs(100) substrate. The GaAs surface was covered by an approximately 1 nm thick oxide layer. Charge accumulation or depletion was induced by the application of forward or reverse bias voltages. We observed a substantial increase in friction Force in accumulation (forward bias) with respect to depletion (reverse bias). We propose a model based on the Force exerted by the trapped charges that quantitatively explains the experimental observations of excess friction.

  • a variable temperature ultrahigh vacuum Atomic Force Microscope
    Review of Scientific Instruments, 1995
    Co-Authors: Qing Dai, D F Ogletree, R Vollmer, Robert W Carpick, M Salmeron
    Abstract:

    A new Atomic Force Microscope (AFM) that operates in ultrahigh vacuum (UHV) is described. The sample is held fixed with spring clamps while the AMF cantilever and deflection sensor are scanned above it. Thus, the sample is easily coupled to a liquid nitrogen cooled thermal reservoir which allows AFM operation from ≊100 K to room temperature. AFM operation above room temperature is also possible. The Microscope head is capable of coarse x‐y positioning over millimeter distances so that AFM images can be taken virtually anywhere upon a macroscopic sample. The optical beam deflection scheme is used for detection, allowing simultaneous normal and lateral Force measurements. The sample can be transferred from the AFM stage to a low energy electron diffraction/Auger electron spectrometer stage for surface analysis. Atomic lattice resolution AFM images taken in UHV are presented at 110, 296, and 430 K.