March 25, 2010

Electron Microscope Allows ‘Atom-by-Atom Analysis’

Material scientists have high hopes that one day they will be able place a sample of unknown substance under a microscope and be able to name individual atoms and what structure they form, reports the AFP news agency.

Thanks to a feat by US scientists, they are one step closer to that goal. Scientists used a transmission electron microscope to analyze a single layer of film made up of boron nitride. They were able to distinguish boron atoms from nitrogen atoms, as well as oxygen and carbon atoms.

Transmission electron microscopy is a technique that sends a narrow beam of electrons through a super-thin sample. Depending on the density of the sample, some electrons are scattered.

The unscattered electrons strike a screen at the bottom of the microscope, creating a shadow image which is formed by interaction between the electrons and atoms within the sample. The core technology in telescopic electron microscopy dates back to 1931.

The process hasn't been problem free either. Scientists had a hard time getting electromagnetic lenses to focus on the beam on the sample, and the electrons often damaged the samples as well.

The breakthrough stems from optics that correct the lens abnormality and form a somewhat annular dark-field method that is sensitive to the number of protons in the nucleus of the imaged atoms, according to the British journal Nature.

The study is led by Ondrej Krivanek of Nion Co., a company based in Kirkland, Washington, that specializes in electron microscopy.

The first atom to ever be viewed was by physicist Erwin Mueller in 1955 using a field ion microscope.


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