Analysis of contact stiffness in ultrasound atomic force microscopy: three-dimensional time-dependent ultrasound modeling

Piras, Daniele; Sadeghian, Hamed

doi:10.1088/1361-6463/aa7024

Cited by 10 publications

(7 citation statements)

References 20 publications

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“…Contact resonance atomic force microscopy (CR-AFM) has been widely applied to characterize local mechanical properties of specimens [1][2][3][4][5][6] and subsequent subsurface nanoimaging via tip-generated stress [7][8][9][10][11][12][13][14][15][16][17][18]. In CR-AFM, the sample or the cantilever is ultrasonically excited while keeping them in contact.…”

Section: Introductionmentioning

confidence: 99%

Enhancement of contact resonance atomic force microscopy subsurface imaging by mass-attached cantilevers

Wang

Zhang

Chen

2020

J. Phys. D: Appl. Phys.

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Improvement of contact resonance atomic force microscopy (CR-AFM) frequency sensitivity at a high contact stiffness condition and subsequent enhancement of its subsurface imaging capability were demonstrated by adding an additional mass on the cantilever backside near the free end. The influence of mass and its position on the CR-AFM performances was analytically investigated by using a simplified cantilever vibration model and further compared with finite element analysis. Theoretical results and FEA simulations showed good agreement and they could provide a general guide on the cantilever’s modification by attaching a proper mass to improve the CR-AFM capability. As a prototype, a Pt micro-disc with precisely controlled size and position on the cantilever, which served as the attached mass, was deposited by utilizing focused ion beam. The improvement of frequency sensitivity was verified through CR spectroscopy and subsurface imaging on cavities having pre-determined diameters and covered with highly oriented pyrolytic graphite flakes. Compared with the original unmodified cantilever, obvious enhancement of CR-AFM subsurface nano-imaging was obtained. The mass-attached cantilever can benefit characterizing sample’s mechanical properties and enhancing subsurface imaging based on tip-generated stress.

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Section: Introductionmentioning

confidence: 99%

Enhancement of contact resonance atomic force microscopy subsurface imaging by mass-attached cantilevers

Wang

Zhang

Chen

2020

J. Phys. D: Appl. Phys.

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“…In addition, mechanically heterogeneous structures in the contact volume will alter the local contact stiffness and then the contact resonance of the cantilever. Its usage in detecting buried structures such as defects [21–25] and nanofillers [26–28] has thus gained much attention. Although a few investigations have been carried out using CR-AFM for subsurface imaging, its application in defect diagnosis for flexible circuits has seldom been reported.…”

Section: Introductionmentioning

confidence: 99%

Subsurface imaging of flexible circuits via contact resonance atomic force microscopy

Wang¹,

Ma²,

Chen³

et al. 2019

Beilstein J. Nanotechnol.

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Subsurface imaging of Au circuit structures embedded in poly(methyl methacrylate) (PMMA) thin films with a cover thickness ranging from 52 to 653 nm was carried out by using contact resonance atomic force microscopy (CR-AFM). The mechanical difference of the embedded metal layer leads to an obvious CR-AFM frequency shift and therefore its unambiguous differentiation from the polymer matrix. The contact stiffness contrast, determined from the tracked frequency images, was employed for quantitative evaluation. The influence of various parameter settings and sample properties was systematically investigated by combining experimental results with theoretical analysis from finite element simulations. The results show that imaging with a softer cantilever and a lower eigenmode will improve the subsurface contrast. The experimental results and theoretical calculations provide a guide to optimizing parameter settings for the nondestructive diagnosis of flexible circuits. Defect detection of the embedded circuit pattern was also carried out, which indicates the capability of imaging tiny subsurface structures smaller than 100 nm by using CR-AFM.

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“…Viscoelasticity based SSPM requires large indentation forces applied to the tip in order to extend the stress field in the sample and in that way probe the subsurface. Thus, the maximum detection depth of the method is limited to less than 1 μm 8,12 depending on the medium's compressive strength and the viscoelastic contrast between the subsurface feature and the surrounding medium. 2) Scattering 14 15 :…”

Section: Introductionmentioning

confidence: 99%

“…The scattered wave then travels towards the sample top surface, and the resulting sample top surface displacement is picked up by an AFM probe. The contact between tip and sample surface is described in literature by means of Hertz theory 8,12,17 . In Hertz theory the relation between the contact force and the resulting tip indentation is nonlinear.…”

Section: Introductionmentioning

confidence: 99%

Optimization of acoustic coupling for bottom actuated scattering based subsurface scanning probe microscopy

Neer

Quesson

et al. 2019

Review of Scientific Instruments

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The characterization of buried nanoscale structures non-destructively is an important challenge in a number of applications, such as defect detection and metrology in the semiconductor industry. A promising technique is Subsurface Scanning Probe Microscopy (SSPM), which combines ultrasound with Atomic Force Microscopy (AFM). Initially, SSPM was used measure the viscoelastic contrast between a subsurface feature and its surrounding medium. However, by increasing the ultrasonic frequency to >1 GHz, it has been shown that SSPM can also measure acoustic impedance based contrasts. At these frequencies it becomes difficult to reliably couple the sound into the sample such that the AFM is able to pick up the scattered sound field. The cause is the existence of strong acoustic resonances in the sample, the transducer and the coupling layer-the liquid layer used to couple the sound energy from the transducer into the sample-in combination with the nonlinearity of the tipsample interaction. Thus, it is essential to control and measure the thickness of the coupling layer with nanometer accuracy. Here, we present the design of a mechanical clamp to ensure a stable acoustic coupling. Moreover, an acoustic method is presented to measure the coupling layer thickness in realtime. Stable coupling layers with thicknesses of 700 ± 2 nm were achieved over periods of 2-4 hours. Measurements of the downmixed AFM signals showed stable signal intensities for >1 hour. The clamp and monitoring method introduced here makes scattering based SSPM practical, robust and reliable and enables measurement periods of hours.

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Analysis of contact stiffness in ultrasound atomic force microscopy: three-dimensional time-dependent ultrasound modeling

Cited by 10 publications

References 20 publications

Enhancement of contact resonance atomic force microscopy subsurface imaging by mass-attached cantilevers

Enhancement of contact resonance atomic force microscopy subsurface imaging by mass-attached cantilevers

Subsurface imaging of flexible circuits via contact resonance atomic force microscopy

Optimization of acoustic coupling for bottom actuated scattering based subsurface scanning probe microscopy

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