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NatureInterface > No.02 > P076-079 [Japanese]

Scanning Prove Microscope: The Engine of the Further Innovation of Nanotechnology -- Seiko Instruments Inc.

















Scanning Prove Microscope, the Engine of the Further Innovation of "Nanotechnology"


Nanotechnology (1 nanometer = 1/1 billion meter) is the technology of treating the minute world of atoms and molecules. This field, in which basic research has been done for more than ten years in Japan, is attracting a great deal of attention from various fields, such as semiconductor technology, optical technology, and medical technology. Moreover, the government has allocated 20 trillion yen for research and development of the life sciences, IT, environment, and nanotechnology in the next Basic Plan for Science and Technology (the 2001 fiscal year - the 2005 fiscal year). SPM (Scanning Prove Microscope) is scanning and processing equipment indispensable to the research and development of nanotechnology. Seiko Instruments, Inc. (SII) started research on SPM in Japan early on, and is currently experiencing a domestic top market share in this field. SPM, the fundamental tool of nanotechnology, will be reported on here.

The Evolution of Nanotechnology

Our world has already entered the period of nanotechnology, if we define nanotechnology as "the technology for visualization, manipulation, assembly, and handling sample materials under a nano scale environment." The structures of silicone semiconductor devices have to be observed physically in nanometer scale, and DNA with a diameter of 2 nanometers is observed directly in the field of genetic engineering. Moreover, the generation of efficient energy and long life batteries has been studied in the energy related field, and many research results have been reported in various fields, including medical science and the environment. In the field of nanotechnology, research and development that can be classified into the following three categories is being performed:

1. R&D that aims at utilization and industrialization five - ten years after.

2. Aggressive R&D that looks ahead to ten - 20 years after.

3. Germinal research that attaches importance to individual originality.

And as observation and manipulation equipment indispensable to those ultramodern research and development projects, SPM is attracting a great deal of attention from industrial, administrative, and academic sectors.

What is SPM?

SPM is the general term for microscopes that observe sample surfaces and measure a field distribution of the surface force, current and light which works between tip and sample using the keenly sharpened probe. STM (Scanning Tunnel Microscope, which observes a form of sample surface using minute "tunnel currents," which flow between the probe and a sample), and AFM (Atomic Force Microscope, which observes a form of a sample surface using minute "atomic force" produced between its probe and a sample), are typical SPM. Those progresses of SPM's are rapidly developed at the same pace as nanotechnology. SPM has great merits, as follows:

1. Simultaneous observation of 3-dimensional form, and physical properties of a sample at high magnification.

2. Measurement under various environments, such as the inside of solutions, a vacuum, the atmosphere, various temperatures or humidity and changing electric or magnetic field.

3. Modification of a sample.

4. SPM's are small-sized and relatively inexpensive.

SII started research and development of STM based on their global level precision machinery machining technology in the form of technical cooperation to the Electrotechnical Laboratory in 1985, and in 1989, four years after that, the company succeeded in commercializing STM (SAM3000). Since then, they have been developing various kinds of frame models (17 models) and peripheral equipment, and have released them on the market.

Application and Resolution of SPM

Let us show you how SPM measures samples and its resolution and magnification. Basically, SPM can measure anything that has a form. The small projections and dents on a flat sample can be measured in angstrom units (1 angstrom = 0.1 nanometer,?or the height of one atom). In addition, one of the most unique merits of SPM is that it can visualize various physical information (light, magnetism, electrical potential, friction, hardness, etc.) of sample surfaces, as well as sample forms in an angstrom unit. SPM can observe samples at 1000 to about several 10 million times magnification. The magnification depends on samples properties.

Moreover, SPM can measure samples not only in the atmosphere, but also in various environments, such as in a gas atmosphere, in a vacuum, or in a solution. Although SEM can measure samples in high resolution like SPM, however, SEM needs high vacuum for using an electronic beam. Moreover, although there is an optical technique to observe samples in the atmosphere and in solutions, it is not possible to acquire the information below the wavelength of light. SPM can measure samples in any environment, if it is possible to control the distance between its probe and a sample, and to detect the interaction between the probe and sample. SPM definitively differs from other nanometer-observation equipment in that it can measure samples controlling environment, such as atmosphere and temperature. In actuality, SPM has the capability of broad applications. In terms of its wide application, SPM, which visualizes a field distribution of the amount of substances on a sample surface detecting various physical interactions between its probe and a sample surface, can measure other information about a sample, besides its form. There are MFM (Magnetic Force Microscopes), SMM/KFM (Scanning Maxwell stress Microscopes / Kelvin Force Microscopes), and VE-AFM (Visco-Elasticity Atomic Force Microscopes) in typical SPM's.

Development of SNOAM (Scanning Near-field Optical Atomic-force Microscope)

Next, we'll describe the SNOAM. SII became the first one to commercialize the SONAM to the world. In a common optical microscope, the resolution is the half grade of the wavelength of the light to use because of the diffraction. For example, with light with a wavelength of 500 nanometers, 250 nanometers is the limit of observation. The reason for the limit is light diffraction. But newly-developed SPM that utilizes near-field light that does not depend on wavelength makes scanning resolution higher than before. Precision machining technology in SII makes it possible to produce SPM probes by making a minimum hole in the tip of an optical fiber. By use of the probes, SII commercialize SNOAM, which obtains optical information such as a penetration image and a fluorescence image using near-field light on a sample surface. SNOAM is used as observation equipment for cellular tissues and the DNA of a living body, and it is also expected to be used as a machining tool at a nano level.

In this report, the outline of SPM has been briefly explained. As mentioned above, SPM has been evolving by realizing various applications, and it has become indispensable equipment to nanotechnology. In the 21st century, new development subjects using nanotechnology, such as "next generation semiconductors," "very high density memory," "new material," "nano manufacture technology," and "biotechnology," are mentioned all over the world. SII will expand the possibility of using SPM, in compliance with the demands of users.

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