[an error occurred while processing this directive] IBM Research - Zurich | News

Low-cost microscope to spur new surface studies

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Zurich, Switzerland, and Chiba, Japan; July 15, 1998—Scientists can now examine surfaces with greater precision, more convenience and at less cost thanks to a cleverly designed atomic force microscope developed by IBM Research - Zurich in Switzerland and Seiko Instruments Inc., Chiba, Japan.

The new atomic force microscope (AFM) can inspect surfaces with nearly atomic resolution without a special vibration-damping table. The least expensive version, called Nanopics (TM), will cost less than one-third of US$100,000 average price of today's basic, less-capable AFMs.

The basic technology for this low-cost AFM was developed by scientists at IBM Research - Zurich. Seiko Instruments Inc. (SII) later licensed IBM's AFM patents and worked with the IBM scientists to develop the product. SII is already selling the new instrument in Japan. Worldwide availability has not been announced. SII estimates that about 1,000 AFMs were purchased in 1997 worldwide with a sales volume of about US$100 million.

"The dramatically reduced price of such a powerful AFM will allow many small commercial and research laboratories and even schools to begin to study surfaces on a nearly atomic scale," said IBM Fellow Gerd Binnig. He is an IBM Zurich physicist who invented the AFM in 1986, shortly before receiving the Nobel Prize in Physics for his role in inventing, with Heinrich Rohrer, the scanning tunneling microsope (STM) for imaging atoms on conducting surfaces.

Understanding the atomic-scale details of surfaces is increasingly important in both science and industry. Among a myriad examples, AFM examinations of surfaces have led to improved optical lenses, magnetic hard disks and filters used in blood cleansing.

Like the STM, the AFM can detect the height profile of a sample by scanning its surface with a fine tip—in the best cases with such high resolution that the position of individual atoms can be recognized. An STM works by sending a "tunneling" current between tip and sample, which must be electrically conductive. The AFM, however, can be used to investigate any surface, even poorly or nonconducting ones, which broadens its potential applications significantly. Many companies and laboratories are using AFMs today.

The original AFM was developed by Binnig, IBM colleague Christoph Gerber, and Calvin Quate of Stanford University in California. Its heart is a fine tip formed at the end of a flexible silicon bar called a cantilever. Forces between the tip and sample can cause the cantilever to bend closer or farther away from the sample surface or to change its resonant frequency, depending on the distance between tip and sample. Such changes are detected and are used to image the topography of the surface as it is scanned by the tip.

"We wanted to create a high-tech instrument that is accessible to as many people as possible," says Binnig. "Our collaboration with SII has produced a microscope that we believe will become standard equipment in many laboratories. The microscope will also make it possible for young people with yet a limited knowledge of microscopy to gain their own insight into smallest features of nature."

Technical background The technical innovations that made the new AFM cheaper to manufacture and simpler to operate include:

Sensors integrated into the cantilever itself measure its motion. Conventional force microscopes use expensive laser beam reflection or interferometry systems to measure the cantilever deflection. Inexpensive voice coils from everyday loudspeakers position the AFM tip more precisely and over a wider range than the costly piezoelectric elements used in conventional scanning microscopes. An intricate but inexpensive mechanism moves the tip precisely over a wide range of distances: (1) rough vertical tip approach to a surface (4-5 millimeters), (2) fine vertical adjustment of the tip-sample distance (20 micrometers, thousandths of a millimeter), and (3) scanning surfaces from 0.5 to 800 micrometers square. Only the component containing the AFM cantilever scans across the surface. In most conventional force microscopes, the entire sample is moved. This design makes the instrument less expensive to manufacture and also permits looking at a specific area of a large sample. (To do this, the measuring head is separated from the the sample holder and positionined directly atop the sample.) The AFM was designed to be compact and uses components with naturally high resonant frequencies, all of which reduces the instrument's sensitivity to external vibrations. This AFM can thus operate in many more types of locations than had been possible before. The measurement electronics of the basic Nanopics AFM produces a TV-quality color video image of 512-by-512 pixels. Results can therefore be displayed on any TV screen and stored on ordinary video tape. Color can also be added to illustrate sample properties, such as topography or material structures, making expensive digital image recording unnecessary for displaying results.

The finest Nanopics resolution of a few nanometers is achieved with the relatively simple image-processing equipment at scanning lengths of up to 500 nanometers. Optional features include higher image resolution, programmable computer control of the instrument, and digital recording to permit more sophisticated image display and analysis. SII is also developing customized but still low-cost AFMs for specific applications, such as for inspecting semiconductor surfaces and for use in biology.

Press contact

Nicole Strachowski
Media Relations
IBM Research - Zurich
Tel +41 44 724 84 45

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