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WO1998008046A1 - Microscope a force atomique et procede correspondant - Google Patents

Microscope a force atomique et procede correspondant Download PDF

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Publication number
WO1998008046A1
WO1998008046A1 PCT/GB1997/002232 GB9702232W WO9808046A1 WO 1998008046 A1 WO1998008046 A1 WO 1998008046A1 GB 9702232 W GB9702232 W GB 9702232W WO 9808046 A1 WO9808046 A1 WO 9808046A1
Authority
WO
WIPO (PCT)
Prior art keywords
cantilever
tip
frequency
sample
vibration
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB1997/002232
Other languages
English (en)
Inventor
Oleg Victor Kolosov
George Andrew Davidson Briggs
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Oxford University Innovation Ltd
Original Assignee
Oxford University Innovation Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Oxford University Innovation Ltd filed Critical Oxford University Innovation Ltd
Priority to AU40225/97A priority Critical patent/AU4022597A/en
Publication of WO1998008046A1 publication Critical patent/WO1998008046A1/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
    • G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
    • G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
    • G01Q60/32—AC mode

Definitions

  • the present invention relates to apparatus for and a method of imaging and studying surface and sub-surface characteristics of a sample at nanoscale resolution in dependence on the atomic force between the sample and a tip of the apparatus.
  • the present invention relates to atomic force microscopy apparatus and a method thereof and it will be understood that in the context of this document reference to atomic force microscopy apparatus is intended as reference to any microscope or other apparatus which relies upon the detection and measurement of atomic force.
  • an atomic force microscope consists of an arm or cantilever at the end of which is an atomically sharp tip which is held very close, for example a few Angstrom, from the surface of a sample to be studied.
  • the cantilever is capable of deflection in a plane perpendicular to the surface of the sample and the characteristics of the sample are studied by monitoring the deflection of the tip as a result of the atomic force between the tip and the surface of the sample.
  • the atomic force involved can be either of the van de Waals (attractive) or core (repulsive) type and is of the order of 10 "6 and 10 "12 N.
  • the ultrasonic force microscope enables the imaging and mapping of the dynamic surface and sub-surface viscoelastic properties of a sample and hence elastic and adhesion phenomena as well as local material composition which otherwise would not be visible using standard techniques at nanoscale resolution.
  • the sample is vibrated by means of a piezotransducer attached to the sample but this can be inconvenient and in some cases is impossible. Also, it requires the output of the microscope to be normalised with respect to the particular sample-piezotransducer attachment.
  • the sample is particularly thick, has a very irregular surface or high ultrasonic attenuation only low surface vibration amplitude may be generated. In such circumstances the amplitude of vibration may be below the sensitivity threshold of the microscope in which case measurement is impossible.
  • the cantilever is dynamically rigid to ultrasonic frequencies above its natural resonance. Although this rigidity makes the microscope sensitive to the viscoelastic properties of the sample, it significantly reduces the sensitivity of the output of the cantilever at these frequencies. Thus, greater sensitivity to the properties of the sample are gained at the loss of sensitivity to the output of the microscope with the above described atomic force microscopes.
  • the present invention seeks to provide apparatus and a method which maintain sensitivity to the properties of the sample whilst retaining sensitivity to the output of the microscope.
  • the present invention provides atomic force microscopy apparatus having a cantilever with a tip at a free end thereof, a vibration device for applying vibration to the cantilever at a first frequency greater than the resonance frequency of the cantilever and a detector for detecting movement of the tip in dependence on an atomic force between the tip and the surface of a sample characterised in that there is further provided an oscillation device for generating a modulation of the tip-surface interaction at a second frequency which is less than the resonance frequency of the cantilever and the detector includes sampling means whereby movement of the tip is detected at a frequency less than the resonance frequency of the cantilever.
  • the vibration device preferably includes a first signal generator and a vibration generator and the oscillation device is in the form of second signal generator which generates a low frequency signal whereby the output of the first signal generator is modulated by mixing of the output of the second signal generator and the modulated signal is supplied to the vibration generator mechanically coupled to the cantilever.
  • the detector is optical.
  • the detector means may be in the form of a piezotransducer and the sampling means include the second signal generator so that the piezotransducer is in registration with the frequency of the second signal generator.
  • the vibration generator may also be in the form of a piezotransducer.
  • the second signal generator may produce a frequency, amplitude or phase modulating signal.
  • the vibration device is in the form of a first signal generator which supplies a high frequency signal to the vibration generator and the oscillation device is in the form of a second signal generator which supplies a high frequency signal to a second vibration generator arranged for mechanical coupling to the sample and the sampling means of the detector controls measurement of the tip-surface interaction at a frequency corresponding to the difference between the frequencies of the vibrations applied to the cantilever and sample.
  • the vibration of the cantilever may be modulated by the action of the vibration of the sample either in frequency or in amplitude.
  • the apparatus may alternatively or additionally include means for applying external forces to the sample such as electrostatic or electromagnetic etc. which may be constant or varied at frequencies greater than the resonance frequency of the cantilever.
  • the present invention also provides in a second aspect a method of monitoring the atomic force between a tip mounted on a cantilever and the surface of a sample comprising applying a first signal having a frequency greater than the resonance frequency of the cantilever to a vibration generator mechanically coupled to the cantilever, generating a modulation of the tip-surface interaction at a second frequency less than the resonance frequency of the cantilever and detecting movement of the tip at a frequency less than the resonance frequency of the cantilever, the movement of the tip being representative of the atomic force between the tip and the surface of the sample.
  • Figure 1 is a schematic diagram of atomic force microscopy apparatus in accordance with the present invention
  • Figure 2 shows a driving signal for the apparatus of Figure 1 ; and Figure 3 shows the non-linear response of the cantilever with the driving signal of Figure 2.
  • the atomic force microscopy apparatus shown in Figure 1 is generally conventional in design and comprises a cantilever 10 having at its free end a probe or tip 11.
  • the radius of curvature of the tip 11 is made to be as small as possible so as to maximise the resolution of the apparatus.
  • the end of the cantilever 10 opposite to the tip 11 is supported in a mount (not shown).
  • an ultrasonic vibration generator 12 is also provided mechanically coupled to the cantilever so that the cantilever may function as a waveguide.
  • the vibration generator 12 is either directly attached to the cantilever or may be attached through a support member 13, as shown in Figure 1.
  • the vibration generator 12 may be in the form of a piezotransducer or other generator of high frequency vibration.
  • the vibration generator 12 is, in turn, connected to a controller 14 which provides the signal for driving the vibration of the generator.
  • a detector 15 is also provided, separate from the cantilever, for detecting movement of the tip 11.
  • the detector 15 is conventional in design and is arranged to detect vibration of the tip 11.
  • the detector may comprise a laser and a light sensitive reader which is arranged to receive light reflected from off the head of the tip 1 1.
  • the detector 15 may be in the form of a piezoelectric detector.
  • the controller 14 has a high frequency first signal generator 16, a low frequency second signal generator 17 and a modulation device 18 which modulates the high frequency signal from the first signal generator 16 with a low frequency signal from the second signal generator 17.
  • the vibration generator 12 is driven by a modulated signal supplied by the controller 14.
  • the high frequency signal either may be frequency modulated or amplitude modulated as desired.
  • a lock-in amplifier 19 is provided between the controller 14 and detector 15 so that the frequency at which the detector 15 operates is in registration with the frequencies of the controller 14. Any alternative frequency registration device may of course be employed instead of a lock- in amplifier. It will be seen from Figure 1 that the lock-in amplifier 19 is connected to the low frequency second signal generator 17 and it is this low frequency, which is less than the resonance frequency of the cantilever, at which the detector 15 operates. It will of course be understood that the detector 15 need not be in registration with the modulation in which case the lock-in amplifier may be omitted.
  • the waveguide properties of the cantilever are employed with the cantilever 10 being caused to vibrate at a frequency greater than its resonance frequency and the vibration modulated with a frequency less than the resonance frequency of the cantilever.
  • the resultant deflection of the tip 11 is then measured by the detector 15 at substantially the same frequency used to modulate the vibration frequency of the cantilever.
  • the atomic force microscopy apparatus may be used in a scanning mode in which the tip and the surface of the sample move relative to one another and spatially resolved information on the surface of the sample is collected.
  • the apparatus may be used for point measurement of the sample to gain temporally resolved information for example where fluctuations in the characteristics of a region of the surface or sub-surface of the sample are to be measured.
  • the high frequency signal has a frequency of 7.504 MHz with a peak-to-peak amplitude of 0.8 V and has been 100% modulated with a saw tooth signal at a frequency of 2.781 kHz (the cantilver resonance frequency is taken to be 39 kHz).
  • the non-linear response of the caVitilever is shown
  • the effective stiffness K ⁇ of the cantilever at the tip end may be estimated using the model of vibration of a free end cantilever.
  • the effective stiffness K n and effective mass M n of the cantilever for the n-th flexural vibration mode can be related with the mode frequency ⁇ n by the simple point mass oscillator equation ⁇ n ⁇ (K n /M n ) 2 .
  • a third signal generator 20 is mechanically coupled to the sample so that the sample can be vibrated at a frequency higher than the resonance frequency of the cantilever.
  • the first signal generator 16 which also generates a signal at a frequency greater than the resonance frequency of the cantilever, but at a frequency which is different to the vibration frequency applied to the sample, remains connected to the vibration generator 12 and the detector 15 may or may not be brought into registration with the combined vibration frequencies.
  • the tip-surface interaction is non-linear, it is reasonable to assume that with a high frequency ⁇ t vibration applied to the cantilever and an adjacent frequency ⁇ s applied to the sample, the cantilever should vibrate at a difference frequency ⁇ ,- ⁇ s .
  • the first term in parentheses is responsible for the non-linear detection of the cantilever vibration, the last term describes the non-linear detection of the sample vibration and the middle term describes the heterodyne mixing of two frequencies.
  • non-linear detection of the cantilever vibration is provided without the need for vibration to be applied to the sample.
  • the sample is not suitable for the attachment of a piezotransducer for example or where the sample is too thick for the vibration to be transmitted through the sample.
  • nanosecond and sub-nanosecond time scale phase information on the tip-surface mechanical interaction can be obtained, for example acoustic wave propagation and material mechanical viscoelastic properties. This phase information may also be utilised in acoustic holographic algorithms for imaging nanoscale sized sub-surface defects.
  • the detection of the resulting cantilever response with or without reference to the modulation frequencies of tip vibration or the combination frequencies of spectral components of tip vibration or the combination frequencies of spectral components of tip vibration with the spectral components of the variation of additional physical forces should reveal local physico-chemical and physico-mechanical properties of the sample such as carrier concentration or optoelastic constants as well as sensing time-dependent phenomena such as relaxation or oscillations up to nanosecond and sub- nanosecond time resolution.
  • the apparatus could also be employed in nanofabrication techniques where the application of bursts of high frequency vibration at high amplitude could produce plastic deformation of the sample with low amplitude vibration being used for sample imaging.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Health & Medical Sciences (AREA)
  • General Health & Medical Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
  • Radiology & Medical Imaging (AREA)
  • Length Measuring Devices With Unspecified Measuring Means (AREA)
  • Measurement Of Length, Angles, Or The Like Using Electric Or Magnetic Means (AREA)

Abstract

La présente invention décrit un microscope comprenant un bras en porte à faux (10) possédant une pointe atomique (11) et un détecteur (15) qui surveille la déviation de la pointe (11) permettant de mesurer la force atomique entre la pointe et un échantillon. Un transducteur piézo-électrique (12) est situé à l'extrémité du bras en porte à faux (10) à une certaine distance de la pointe (11). Le transducteur piézo-électrique (12) génère des vibrations haute fréquence qui se transmettent au bras en porte à faux. Les vibrations transmises à la pointe (11) sont modulées au moyen d'un second transducteur piézo-électrique (20) en contact avec l'échantillon, et le mouvement de la pointe (11) est alors échantillonné par le détecteur (15) à une fréquence très inférieure. Le microscope et le procédé décrits sont capables de conserver à l'échantillon ses caractéristiques sensibles tout en conservant celles de la sortie de l'appareil. Lesdits procédé et appareil conviennent particulièrement à l'étude d'éléments dont les caractéristiques physico-chimiques et physico-mécaniques dépendent d'un facteur temps pouvant aller jusqu'à une résolution temporelle à l'échelle de la nanoseconde et en dessous.
PCT/GB1997/002232 1996-08-19 1997-08-19 Microscope a force atomique et procede correspondant Ceased WO1998008046A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AU40225/97A AU4022597A (en) 1996-08-19 1997-08-19 Atomic force microscopy apparatus and a method thereof

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9617380.2 1996-08-19
GBGB9617380.2A GB9617380D0 (en) 1996-08-19 1996-08-19 Atomic force microscopy apparatus and a method thereof

Publications (1)

Publication Number Publication Date
WO1998008046A1 true WO1998008046A1 (fr) 1998-02-26

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PCT/GB1997/002232 Ceased WO1998008046A1 (fr) 1996-08-19 1997-08-19 Microscope a force atomique et procede correspondant

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AU (1) AU4022597A (fr)
GB (1) GB9617380D0 (fr)
WO (1) WO1998008046A1 (fr)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7448269B2 (en) 2003-08-12 2008-11-11 Northwestern University Scanning near field ultrasound holography
EP1952204A4 (fr) * 2005-10-06 2011-12-14 Univ Northwestern Holographie ultrasonore de champ proche a balayage
US8322220B2 (en) * 2007-05-10 2012-12-04 Veeco Instruments Inc. Non-destructive wafer-scale sub-surface ultrasonic microscopy employing near field AFM detection
US8438927B2 (en) 2003-08-12 2013-05-14 Northwestern University Scanning near field thermoelastic acoustic holography (SNFTAH)
US8726410B2 (en) 2010-07-30 2014-05-13 The United States Of America As Represented By The Secretary Of The Air Force Atomic force microscopy system and method for nanoscale measurement
CN112798205A (zh) * 2020-12-15 2021-05-14 东莞理工学院 一种原子力显微镜微悬臂弹性系数标定装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410131A1 (fr) * 1989-07-27 1991-01-30 International Business Machines Corporation Microscopie à champ proche employant la force de Lorentz
US5503010A (en) * 1993-11-09 1996-04-02 Agency Of Industrial Science & Technology Directional atomic force microscope and method of observing a sample with the microscope
WO1996024819A1 (fr) * 1995-02-07 1996-08-15 International Business Machines Corp. Detecteur de deflexion d'un element en porte-a-faux et son emploi

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0410131A1 (fr) * 1989-07-27 1991-01-30 International Business Machines Corporation Microscopie à champ proche employant la force de Lorentz
US5503010A (en) * 1993-11-09 1996-04-02 Agency Of Industrial Science & Technology Directional atomic force microscope and method of observing a sample with the microscope
US5503010B1 (en) * 1993-11-09 1998-06-23 Agency Ind Science Techn Directional atomic force microscope and method of observing a sample with the microscope
WO1996024819A1 (fr) * 1995-02-07 1996-08-15 International Business Machines Corp. Detecteur de deflexion d'un element en porte-a-faux et son emploi

Non-Patent Citations (4)

* Cited by examiner, † Cited by third party
Title
GOEDDENHENRICH T ET AL: "A LATERAL MODULATION TECHNIQUE FOR SIMULTANEOUS FRICTION AND TOPOGRAPHY MEASUREMENTS WITH THE ATOMIC FORCE MICROSCOPE", REVIEW OF SCIENTIFIC INSTRUMENTS, vol. 65, no. 9, 1 September 1994 (1994-09-01), pages 2870 - 2873, XP000469221 *
KOLOSOV O ET AL: "Nonlinear detection of ultrasonic vibrations in an atomic force microscope", JAPANESE JOURNAL OF APPLIED PHYSICS, PART 2 (LETTERS), 1 AUG. 1993, JAPAN, vol. 32, no. 8A, ISSN 0021-4922, pages L1095 - L1098, XP002049098 *
NECHAY B A ET AL: "Applications of an atomic force microscope voltage probe with ultrafast time resolution", THIRD INTERNATIONAL CONFERENCE ON NANOMETER-SCALE SCIENCE AND TECHNOLOGY, DENVER, CO, USA, 24-28 OCT. 1994, vol. 13, no. 3, ISSN 0734-211X, JOURNAL OF VACUUM SCIENCE & TECHNOLOGY B (MICROELECTRONICS AND NANOMETER STRUCTURES), MAY-JUNE 1995, USA, pages 1369 - 1374, XP002049099 *
YAMANAKA K ET AL: "ULTRASONIC FORCE MICROSCOPY FOR NANOMETER RESOLUTION SUBSURFACE IMAGING", APPLIED PHYSICS LETTERS, vol. 64, no. 2, 10 January 1994 (1994-01-10), pages 178 - 180, XP000416816 *

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7448269B2 (en) 2003-08-12 2008-11-11 Northwestern University Scanning near field ultrasound holography
US7798001B2 (en) 2003-08-12 2010-09-21 Northwestern University Scanning near field ultrasound holography
US8316713B2 (en) 2003-08-12 2012-11-27 Northwestern University Scanning near field ultrasound holography
US8438927B2 (en) 2003-08-12 2013-05-14 Northwestern University Scanning near field thermoelastic acoustic holography (SNFTAH)
EP1952204A4 (fr) * 2005-10-06 2011-12-14 Univ Northwestern Holographie ultrasonore de champ proche a balayage
US8322220B2 (en) * 2007-05-10 2012-12-04 Veeco Instruments Inc. Non-destructive wafer-scale sub-surface ultrasonic microscopy employing near field AFM detection
US8726410B2 (en) 2010-07-30 2014-05-13 The United States Of America As Represented By The Secretary Of The Air Force Atomic force microscopy system and method for nanoscale measurement
CN112798205A (zh) * 2020-12-15 2021-05-14 东莞理工学院 一种原子力显微镜微悬臂弹性系数标定装置

Also Published As

Publication number Publication date
AU4022597A (en) 1998-03-06
GB9617380D0 (en) 1996-10-02

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