Characteristics of fracture during the approach process and wear mechanism of a silicon AFM tip

Chung, Koo–Hyun; Lee, Yong Ha; Kim, Dae Eun

doi:10.1016/j.ultramic.2004.09.009

Cited by 130 publications

(77 citation statements)

References 31 publications

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“…SEM images of tips before and after force measurement indicates that changes in the tip structure can occur when being in contact with another solid surface. This agrees with results reported by various research groups who observed tip wear by SEM [212][213][214][215][216]. Tip wear was studied at different humilities by scanning an area of µm 5 5× 2 for 5, 10, and 30 min on a silicon wafer or mica with different cantilevers (type 2 and 6).…”

Section: Tip Wearsupporting

confidence: 89%

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

et al. 2006

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To optimize the handling of fine powders in industrial applications, understanding the interaction forces between single powder particles is fundamental. The forces between colloidal particles dominate the behavior of a great variety of materials, including paints, paper, soil, and many industrial processes. With the invention of the atomic force microscope (AFM), the direct measurement of the interaction between single micron-sized particles became possible. The adhesional contact between a particle and a substrate is a parameter for analyzing pull-off force data generated by AFM. The aim of this study was to understand surface interactions between fine particles. I measured the adhesion forces between AFM tips or particles attached to AFM cantilevers and different solid samples. Smooth and homogeneous surfaces such as silicon wafer, mica, or highly oriented pyrolytic graphite (HOPG), and more rough and heterogeneous surfaces such as iron particles or patterns of TiO 2 nanoparticles on silicon wafer were used. First, I addressed to the wellknown issue that AFM adhesion experiment results show wide distributions of adhesion forces rather than a single value. My experimental results show that variations in adhesion forces comprise fast (i.e., from one force curves to the next) random fluctuations and slower fluctuations, which occur over tens or hundreds of consecutive measurements. Slow fluctuations are not likely to be the result of variations in external factors such as lateral position, temperature, humidity, and so forth because those were kept constant. Even if two solid bodies are brought into contact under precisely the same conditions (same place, load, direction, etc.) the result of such a measurement will often not be the same as for the previous contact. The measurement itself will induce structural changes in the contact region which can change the value for the next adhesion force measurement.In the second part I studied the influence of humidity on the adhesion of nanocontacts. Humidity was adjusted relatively fast to minimize tip wear during one experiment. For hydrophobic surfaces, no signification change of adhesion force with humidity was observed. Adhesion force-versus-humidity curves recorded with hydrophilic surfaces either showed a maximum or continuously increased. I demonstrate that the results can be interpreted with simple continuum theory of the meniscus force. The meniscus force is calculated based on a model that includes surface roughness and takes into account different AFM tip (or particle) shapes by a two-sphere-model.Experimental and theoretical results show that the precise contact geometry has a critical influence on the humidity dependence of the adhesion force.Changes of tip geometry on the sub-10-nm length scale can completely change adhesion force-versus-humidity curves. Our model can also explain the differences between earlier AFM studies, where different dependencies of the adhesion force on humidity were observed.Keywords: Atomic force microscopy (AFM), cantile...

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Section: Tip Wearsupporting

confidence: 89%

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

et al. 2006

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“…With a high resolution TEM Chung et al [157] even succeeded to reveal the crystalline structure of a silicon tip. An alternative which does not require an electron microscope is to image a sharp structure and reconstruct the tip shape from the image [153,158,159].…”

Section: Characterizationmentioning

confidence: 99%

“…Computer simulations showed that a transfer of atoms between the two surfaces is likely as they get into contact [160]. Chung et al [157] could show that during the first approach significant structural changes of the tip apex can occur, even at low forces.…”

Section: Characterizationmentioning

confidence: 99%

Force measurements with the atomic force microscope: Technique, interpretation and applications

Butt

Cappella

Kappl

2005

Surface Science Reports

3,242

2,949

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“…Dislocation arrays have also been seen originating at the tip in some of the tips following testing. The observation of a thin amorphous layer on Si cantilever tips has been previously reported [7]. …”

mentioning

confidence: 64%

Wear of Si Cantilever Tips used in Atomic Force Acoustic Microscopy

Geiss

Kopycinska-Müller

Hurley

2005

MAM

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As the implementation of thin films continues to extend into the nanoscale, innovative experimental techniques are needed to study their physical properties. Many applications, for example molecular dynamics modeling, require knowledge about the mechanical properties of such nanoscale thin films. Unfortunately, most conventional methods to evaluate thin-film mechanical properties are illequipped to cope as film dimensions shrink below a micrometer. Recently, the efforts of several groups have focused on the determination of elastic properties using dynamic enhancements of atomic force microscopy (AFM) [1][2][3][4]. Despite individual differences, all of these methods rely on simplified Hertz or Derjaguin-Müller-Toporov (DMT) contact-mechanics models [5,6] to describe the interaction between the AFM tip and the sample. Atomic force acoustic microscopy (AFAM) [3,4] has been used to obtain quantitative elastic-property values that agree with those obtained by nanoindentation or calculated from tabulated data. However, the best agreement is obtained when AFAM experiments include tedious reference measurements to minimize the influence of continuous tip wear. In this paper, we describe our work to better understand the process of tip wear that occurs in AFAM experiments in order to improve contact-mechanics models for data analysis.Several silicon AFM cantilevers were used to conduct a sequence of tests that simulated typical AFAM experiments. AFAM experiments measure the resonant frequency of the cantilever when it is in contact with a vibrating sample as a function of the applied static load. The first test consisted of three AFAM measurements at relatively low loads (about 0.3 to 1.5 µN). In the second test, the static load was increased to 3-5 µN and to as many as 40 repeat measurements. A fused quartz sample was used for all of the experiments. From the measured frequencies of the lowest two flexural modes, the contact stiffness k* was calculated [4]. The Hertz and DMT contact-mechanics models were used to estimate the geometry of the tip and the tip radius R assuming a hemispherical-shaped tip. We also acquired scanning electron microscope (SEM) images of the tips at various points in the AFAM testing sequence and measured the apparent tip radius R SEM . The values of R SEM were compared with the values of R obtained from the AFAM measurements using the above-mentioned theories.The details of the SEM-AFAM experiments and measurement results will be described. In many cases, the tip broke during the first AFAM measurement sequence and increased its radius during subsequent measurements, as seen in Figure 1. We found that the tips always changed. Some tips were found to have ill-defined geometries, as shown in Figure 2, but still yielded useful AFAM data. Broken tips quite frequently show a structure similar to the flat-punch geometry shown in Figure 2c. We observed that tips with initial probe diameters of about 50 nm usually did not break and were the most robust throughout the AFAM measurement sequence. Tips w...

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Characteristics of fracture during the approach process and wear mechanism of a silicon AFM tip

Cited by 130 publications

References 31 publications

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

On the Adhesion between Fine Particles and Nanocontacts: An Atomic Force Microscope Study

Force measurements with the atomic force microscope: Technique, interpretation and applications

Wear of Si Cantilever Tips used in Atomic Force Acoustic Microscopy

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