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February 28th, 2010 at 10:45 pm

Atomic Force Microscopy

Atomic Force MicroscopyDESCRIPTION OF TECHNIQUE

Atomic force microscopy (AFM) is a form of scanning probe microscopy (SPM), where a small probe is scanned across the sample to obtain information on the sample surface. The information gathered by the interaction of the probe with the surface can be as simple as physical topography or other material such as measurements of physical, magnetic, or chemical properties. These data are collected as the probe is scanned in a raster pattern through the sample to form a map of the property measured from the XY position. Thus, the AFM microscope image shows the change in the property measured, for example. height or magnetic domains, over the image area.

The AFM probe tip has a very sharp, often less than 100 in diameter, at the end of a small cantilever beam. The probe is connected to a piezoelectric tube scanner, which scans the probe in a selected area of the surface of the sample. Interatomic forces between the probe tip and the sample surface cause the cantilever to deflect the topography of the sample surface (or other property) changes. A laser light reflected from the back of the cantilever measures the deflection of the cantilever. This information is sent back to a computer, which generates a map of topography and / or other properties of interest. All square as large as about 100 ìm square less than 100 nm can be resumed.

INFORMATION ANALYSIS

Modes of contact AFM – The AFM probe is scanned at a constant force between the probe and the sample surface to obtain a 3D topographical map. When the probe cantilever is deflected by topographic changes, the scanner changes the position of the probe to restore the original cantilever deflection. The location information of the scanner is used to create a topographic image. Lateral resolution of <1 style = “font-weight: bold;”> intermittent contact (tapping mode) AFM – In this mode, the cantilever probe is oscillated or at its resonant frequency. The oscillating probe tip is then scanned at a height where it barely touches or “taps” the surface of the sample. The system monitors the position of the probe and the amplitude of oscillation to obtain information on topographic properties and others. Precise topographic information can be obtained even for very delicate surfaces. Optimum resolution is about 50 Å lateral and <1 style = “font-weight: bold;”> Lateral Force Microscopy – This method of measuring the lateral deviation of the cantilever probe tip is scanned across the sample in contact mode. Changes in lateral bending forces are on the friction between the probe tip and the sample surface.

Detection phase microscopy with the operating system in tapping mode, the cantilever oscillation is damped by the interaction with the sample surface. The phase delay between the signal units and actual cantilever oscillation is monitored. Changes in the phase lag indicate variations in surface properties such as viscoelasticity or mechanical. Image phase, typically collected simultaneously with a topographic image, maps the local changes in physical properties and mechanical properties of the material.

Magnetic Force Microscopy – this image to local variations in the magnetic forces on the sample surface. The tip of the probe is coated with a thin film of ferromagnetic material that reacts to magnetic domains on the surface of the sample. The magnetic forces between the tip and the sample are measured by monitoring the cantilever deflection, while the probe is scanned at a constant height above the surface. A map showing the sample natural forces or applied magnetic domain structure.

Image analysis – Since the images are collected in digital format, a wide range of image manipulation are available for the AFM data. Quantitative topographic information, such as the lateral spacing, step height and the roughness of the surface are readily obtained. Images can be presented as two-dimensional or three-dimensional representations on paper or as digital image files for electronic transfer and publication.

Nanoindentation – A tip of the probe is forced specializes in the sample surface to obtain a measure of the mechanical properties of the material in areas as small as a few nanometers. (See Manual nanoindentation hardness tests.)

TYPICAL APPLICATIONS

* 3-dimensional topography of IC device
* Measures of roughness for the chemical mechanical polishing
* Analysis of the distribution phase microscopic polymer
* Measures of physical and mechanical properties of thin films
* Imaging magnetic domains on digital storage media
* Pictures of the phases of submicron in metals
* Imaging defect in IC failure analysis
* Microscope images of biological samples fragile
* Metrology Stampers compact disk

SAMPLE REQUIREMENTS

No sample preparation is usually necessary. Samples can be taken up in the air or liquid. Sample height is limited to about 1.5 inches. Areas up to 8 inches in diameter can be completely crossed without repositioning. Larger samples may be automatic for imaging in a limited area. Roughness of the surface total image area should not exceed about 6 microns.

source: actually i get this article from my friend’s blog which unfortunately i forget it’s link, but because of someone claim this article to his mine, so i would credit this article to: www.mee-inc.com, thanks for your claiming, it really helpfull to me and my visitor in order to adding our refference :)

Tags: Afm Microscope, Afm Probe, Analysis Modes, Atomic Force Microscopy, Cantilever Beam, Cantilever Deflection, Lateral Resolution, Lt 1, Magnetic Domains, Microscope Image, Mode Afm, Physical Topography, Piezoelectric Tube, Probe Tip, Property Changes, Raster Pattern, Resonant Frequency, Scanning Probe Microscopy, Topographic Changes, Topographic Image
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  • Larry Hanke
    12:19 pm on April 2nd, 2011 1

    This article is strongly derivative of an article that I authored and has been published on line at http://www.mee-inc.com for several years. There are inaccuracies in the details on this page where the original article has not been accurately copied.

  • techicien
    11:12 am on October 29th, 2011 2

    sorry for the late response, but ive been credit this article to that site :)

 

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