MEE Atomic Force Microscopy #mee #atomic #force #microscopy, #afm #failure #analysis, #afm


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Atomic Force Microscopy (AFM)

Atomic Force Microscopy (AFM)

Atomic Force Microscopy

Description 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 about the sample’s surface. The information gathered from the probe’s interaction with the surface can be as simple as physical topography or as diverse as measurements of the material’s physical, magnetic, or chemical properties. These data are collected as the probe is scanned in a raster pattern across the sample to form a map of the measured property relative to the X-Y position. Thus, the AFM microscopic image shows the variation in the measured property, e.g. height or magnetic domains, over the area imaged.

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

Analytical Information

Contact Mode 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 topographical changes, the scanner adjusts the probe position to restore the original cantilever deflection. The scanner position information is used to create a topographical image. Lateral resolution of

Intermittent Contact (Tapping Mode) AFM – In this mode, the probe cantilever is oscillated at or near its resonant frequency. The oscillating probe tip is then scanned at a height where it barely touches or “taps” the sample surface. The system monitors the probe position and vibrational amplitude to obtain topographical and other property information. Accurate topographical information can be obtained even for very fragile surfaces. Optimum resolution is about 50 Å lateral and

Lateral Force Microscopy – This mode measures the lateral deflection of the probe cantilever as the tip is scanned across the sample in contact mode. Changes in lateral deflection represent relative frictional forces between the probe tip and the sample surface.

Phase Detection Microscopy – With the system operating in Tapping mode, the cantilever oscillation is damped by interaction with the sample surface. The phase lag between the drive signal and actual cantilever oscillation is monitored. Changes in the phase lag indicate variations in the surface properties, such as viscoelasticity or mechanical properties. A phase image, typically collected simultaneously with a topographical image, maps the local changes in material’s physical or mechanical properties.

Magnetic Force Microscopy – This mode images local variations in the magnetic forces at the sample’s surface. The probe tip is coated with a thin film of ferromagnetic material that will react to the magnetic domains on the sample surface. The magnetic forces between the tip and the sample are measured by monitoring cantilever deflection while the probe is scanned at a constant height above the surface. A map of the forces shows the sample’s natural or applied magnetic domain structure.


Image Analysis – Since the images are collected in digital format, a wide variety of image manipulations are available for AFM data. Quantitative topographical information, such as lateral spacing, step height, and surface roughness are readily obtained. Images can be presented as two-dimensional or three-dimensional representations in hard copy or as digital image files for electronic transfer and publication.

Nanoindentation – A specialized probe tip is forced into the sample surface to obtain a measure of the material’s mechanical properties in regions as small as a few nanometers. (See the Handbook section on Nanoindentation Hardness Testing .)

Sample Requirements

No sample preparation is typically required. Samples can be imaged in air or liquid. Sample height is limited to about 1.5 inches. Areas up to 8 inches in diameter can be fully traversed without repositioning. Larger samples can be fixtured for imaging within a limited area. Total surface roughness in the image area should not exceed about 6 µm.

Typical Applications

  • 3-dimensional topography of IC device
  • Roughness measurements for chemical mechanical polishing
  • Analysis of microscopic phase distribution in polymers
  • Mechanical and physical property measurements for thin films
  • Imaging magnetic domains on digital storage media
  • Imaging of submicron phases in metals
  • Defect imaging in IC failure analysis
  • Microscopic imaging of fragile biological samples
  • Metrology for compact disk stampers

Planning underway for Mendenhall Glacier visitor center improvements #climate #change,cruise #ship,emission,glacier,greenhouse #gas,intergovernmental


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Planning underway for Mendenhall Glacier visitor improvements

View of the staging lot for waiting buses at the Mendenhall Glacier Visitor Center. (Photo by Matt Miller/KTOO)

Managers of Juneau s most popular tourist attraction say they’re planning for a more sustainable facility, even as the very object of many a visitors fascination continues retreating at a faster rate because of climate change.

Most of the $415,000 dollars for drafting a master plan for the U.S. Forest Service s Mendenhall Glacier Visitor Center comes from the Federal Highway Administration. The plan may address everything from Glacier Spur Road access to improving parking, culverts, trails and other outdoor areas, and even heat loss from the large, inefficient windows at the Visitor Center.

Visitor Center Director John Neary briefly explained the plan during a press conference Tuesday about potential impacts to the Alaska tourism industry from climate change.

It seems like a no-brainer to me, Neary said.

We have people coming on cruise ships that are belching emissions that are contributing (to climate change), and they get on diesel buses that are belching emissions, and they land at the glacier, and get off, and they see this glacier, and they’re not making the connection between everything they’ve just done and what they’re seeing before them.

Neary went into more detail during an interview with KTOO immediately after the teleconferenced presentation. He’s open to ideas such as reconstruction of a Nugget Creek hydroelectric project that served miners a century ago, closing off the end of Glacier Spur Road and using an electric circulator or tram to transport visitors from a parking lot to the Center, and offering incentives for tour companies to electrify their bus fleet.

Passengers board a bus at the Mendenhall Glacier Visitor Center on Tuesday. (Photo by Matt Miller/KTOO)

Such as, if we were to provide plug in stations for those buses with electricity at competitive rates, and with those stations offering the best parking spot that is available.

Neary points out that the Mendenhall Glacier is the most popular tourism destination with 450,000 visitors, or almost half of the total number of cruise ship passengers that visit Juneau each year. Of that number, about 10,000 visitors to the glacier are locals. He also said companies can’t sell trips to other destinations in Juneau (like the DIPAC hatchery, for example) unless the Mendenhall Glacier is included in the package.

Neary admits that achieving zero-net energy and zero-net waste at the Visitor Center, or entirely eliminating carbon emissions would be extremely difficult, if not impossible. But that’s not the ultimate goal anyway. He said their job as interpreters is about making that link, or connecting people to the landscape in a way that they never had thought about before.

We’re not making the fact that ‘You are the cause of the retreating glacier. You and everyone else.’ We all collectively need to address this. And a starting point would be right here at this Visitor Center.

He hopes that visitors will then go home, start a discussion, and take action in their own community.

Neary said they’ll finish the plan and have priorities identified by next spring. Implementation of the plan, however, may take years and a lot more funding.

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