(word processor parameters LM=8, RM=75, TM=2, BM=2) Taken from KeelyNet BBS (214) 324-3501 Sponsored by Vangard Sciences PO BOX 1031 Mesquite, TX 75150 There are ABSOLUTELY NO RESTRICTIONS on duplicating, publishing or distributing the files on KeelyNet except where noted! October 30, 1993 SCOPE.ASC -------------------------------------------------------------------- This file shared with KeelyNet courtesy of Bert Pool. -------------------------------------------------------------------- 02-22-1993 New optical microscopes transcend limits of visible light By John Markoff New York Times News Service A new generation of optical microscopes is emerging, capable of resolving images far beyond the conventional limits imposed by visible light. These microscopes are known as near-field scanning optical microscopes, or NSOM, and they may soon offer a wide variety of remarkable applications ranging from detailed movies of the inner workings of cells to vast increases in data storage capacity for the computer industry. In theory the technique could pack information so densely that two copies of "War and Peace" could be transcribed in the area of a pinhead. The renaissance of optical microscopy is a striking reversal of recent trends in this three-century-old technology. Since the 1930s conventional lens-based optical microscopes have increasingly lagged behind two other kinds. One is the electron and X-ray microscopes which resolve at far shorter wavelengths than optical systems; the other is scanning probe instruments which, in the case of the scanning tunneling microscope, can now routinely resolve objects as tiny as individual atoms. Yet despite the razor-sharp imaging ability of nonoptical systems they have failed to replace traditional optical microscopy for many applications because of what researchers call a Faustian bargain struck by each technology. In both cases compromises must be made. There are shortcomings in these powerful technologies ranging from lack of viewing contrast to the destructiveness of techniques that destroy biological material. Despite its great promise, the new optical technique has been developing slowly because of a variety of hurdles that are only now being overcome. Until now near-field scanning optical microscopes have been the laggards of the field, said Eric Betzig, a physicist at AT&T Bell Laboratories who is one of the leading developers of the Page 1 instruments. That is now changing quickly based on technical advances made in Betzig's laboratory and by researchers at Cornell University and IBM scientists in Zurich, Switzerland. Their hope is that the near-field optical instruments now being perfected will take advantage of the decades of experience gained with improving conventional optical microscopes. Betzig said advantages like speed and the ease of preparing specimens would enable scientists to adapt quickly to the new technique. Betzig's belief in the field's promise is echoed by some of the leading figures in microscope research. "Near-field optical extends the limits to a degree that is unprecedented," said Calvin Quate, a Stanford University physicist who is a pioneer in developing advanced microscope technologies. "If you have two microscopes of similar resolution, the optical would win out because of the power of photons." Bell Laboratories researchers have already perfected near-field scanning optical microscopes capable of resolving images down to approximately 12 nanometers, or less than one 1,700,000-millionth of an inch. This makes it easy to view objects like bacterial viruses which are in the range of 70 nanometers across or about one 360,000th of an inch. At the heart of the new technique is an ultra-fine fiber-optic probe that can be steered over the surface of a sample with remarkable accuracy while staying within several nanometers of the object's surface. The probe itself is created by heating and drawing a fiber-optic wire and then sheering its tip. The probe is coated with aluminum and a light is shined through it. As the probe is scanned over the surface of an object, an image is built up line by line, much as a television image is created. The great advantage of the new technique is that it evades a basic physics principle known as the diffraction limit, which holds that details that are smaller than half the wavelength of light cannot be resolved. The microscope can in fact resolve objects that are dwarfed by the wavelength of light, which is around 500 nanometers. To get around the diffraction barrier, the new instruments exploit the fact that a light wave can be defined as the sum of a series of waves with far shorter wavelengths. Because of the probe's extreme proximity to the surface it is measuring, it can detect these "evanescent" waves that are lost at greater distances. Several applications for the new breed of optical microscopes are now being explored. At Bell Laboratories Betzig and his co-workers have used the instrument to view extremely thin tissue samples taken from the hippocampus of a monkey's brain. When it is used together with a conventional optical microscope, the viewer can jump back and forth from a wide viewing area to focusing in on extremely fine features that have traditionally only been accessible to transmission electron microscopes. The Bell research Page 2 suggests that the new instrument could become a cost-effective tool for clinical pathology. MORE (Optional 2ndtake follows.) In the laboratory of Michael S. Isaacson, a Cornell physicist who led one of the three groups that originally developed the near-field optical microscopes in the late 1970s and early 1980s, researchers are using the devices as diagnose semiconductor lasers. With the instrument's power, they can understand more precisely problems that develop in the process of growing the lasers. Despite early promise, some significant hurdles remain. In biological fields, Isaacson said that the instrument's usefulness is narrow so far. "The technique may be restricted to a certain class of biological objects," he said. Because the optical probe functions so close to the surface of an object, it may be impossible to navigate across cell surfaces that have many protruding receptors. But Isaacson said that researchers at the University of Washington had already begun using a near-field microscope to explore the structure of muscle cells, which generally have smooth surfaces. Indeed, the Bell Laboratories researchers, working with scientists at the Center for Light Microscope Imaging and Biotechnology at Carnegie Mellon University, have already demonstrated that the near- field technique can obtain more detailed images of cell structures than can other microscopic methods. The detailed cell images are providing new insights into the mechanisms of wound repair, they said. They have also recently begun to view cells under water, a first step toward creating images of living cells. It currently takes about 45 minutes to obtain a 512 by 512 pixel image, far slower than some of the living cell processes. In the future, however, Betzig said the researchers believe that modifications to the current system may make it possible to create several images per second. There are also several research projects under way in nonbiological areas. The Cornell Laboratory, in conjunction with IBM, is exploring use of the NSOM to write ultra-thin circuit lines on silicon wafers by scanning the probe tip over a light-sensitive semiconducting material. At present electronic circuits are etched on semiconductors by shining ultraviolet light through masks that make it possible to expose as many as 30 wafers an hour. Using a single NSOM probe would take a prohibitive amount of time even to write the circuitry for a single chip. To overcome this barrier scientists are discussing the possibility of creating arrays of tens of thousands of probes that could scan across the surface of a wafer writing ultra-dense semiconductor circuits. "You can fabricate silicon structures that are almost comparable with what you can do with electron beams," said Isaacson. "But in order for it to be realistic in a manufacturing sense you would have to do it in parallel." Page 3 There may be intermediate applications in the semiconductor manufacturing process, however. The Bell Laboratories researchers are studying using the NSOM tools as an inexpensive means for correcting defects in the masks that are used in the lithographic process needed to make microchips. Potentially it will be possible to microscopically "weld" defects in the delicate semiconductor circuit pattern masks. The Bell Laboratories researchers are also exploring the possibility of using the NSOM as a device for storing and retrieving computer data. Currently they have been able to read and write information at densities of 45 billion bits per inch. If that much information were in the form of recorded music, it would take a disk the size of a quarter as much as eight days to play it all. If it took the form of compressed high-density television programming, a palm-sized disk could hold 17 hours' worth. Yet while such densities are more than 40 times greater than those attained with state-of-the-art magnetic recording techniques, there are competing technologies that may be even more promising. Last year IBM scientists at the company's Almaden Research Center in San Jose used an atomic force microscope probe in conjunction with a laser to store and retrieve data at even higher storage densities. It is still early but researchers are beginning to talk about the advent of a golden age in the Lilliputian world of high-technology microscopes. "It's a fantastic time, its the golden age of microscopy," said Kumar Wickramasinghe, manager of physical measurements at IBM's Thomas J. Watson Research Center in Yorktown Heights, N.Y. "The scanning tunneling microscope has taught me and a lot of others in this field that by scanning probes around you can overcome the limits to resolution. Now you're really limited only by the ingenuity of the scientist designing the probe. We're all having lots of fun." -------------------------------------------------------------------- If you have comments or other information relating to such topics as this paper covers, please upload to KeelyNet or send to the Vangard Sciences address as listed on the first page. Thank you for your consideration, interest and support. Jerry W. Decker.........Ron Barker...........Chuck Henderson Vangard Sciences/KeelyNet -------------------------------------------------------------------- If we can be of service, you may contact Jerry at (214) 324-8741 or Ron at (214) 242-9346 -------------------------------------------------------------------- Page 4