Milestone-Proposal:First Practical Field Emission Electron Microscope, 1972-1984
This Proposal has been approved, and is now a Milestone Nomination
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Is the achievement you are proposing more than 25 years old?
Is the achievement you are proposing within IEEE’s fields of interest? (e.g. “the theory and practice of electrical, electronics, communications and computer engineering, as well as computer science, the allied branches of engineering and the related arts and sciences” – from the IEEE Constitution)
Did the achievement provide a meaningful benefit for humanity?
Was it of at least regional importance?
Has an IEEE Organizational Unit agreed to pay for the milestone plaque(s)?
Has an IEEE Organizational Unit agreed to arrange the dedication ceremony?
Has the IEEE Section in which the milestone is located agreed to take responsibility for the plaque after it is dedicated?
Has the owner of the site agreed to have it designated as an Electrical Engineering Milestone? Yes
Year or range of years in which the achievement occurred:
Title of the proposed milestone:
First Practical Field Emission Electron Microscope, 1972-1984
Plaque citation summarizing the achievement and its significance:
In what IEEE section(s) does it reside?
IEEE Tokyo Section
IEEE Organizational Unit(s) which have agreed to sponsor the Milestone:
IEEE Organizational Unit(s) paying for milestone plaque(s):
IEEE Organizational Unit(s) arranging the dedication ceremony:
IEEE section(s) monitoring the plaque(s):
Street address(es) and GPS coordinates of the intended milestone plaque site(s):
Naka Division, Hitachi High Technologies Corporation (formerly Naka Works, Hitachi Ltd.) and Central Research Laboratory, Hitachi Ltd.
Describe briefly the intended site(s) of the milestone plaque(s). The intended site(s) must have a direct connection with the achievement (e.g. where developed, invented, tested, demonstrated, installed, or operated, etc.). A museum where a device or example of the technology is displayed, or the university where the inventor studied, are not, in themselves, sufficient connection for a milestone plaque.
Please give the address(es) of the plaque site(s) (GPS coordinates if you have them). Also please give the details of the mounting, i.e. on the outside of the building, in the ground floor entrance hall, on a plinth on the grounds, etc. If visitors to the plaque site will need to go through security, or make an appointment, please give the contact information visitors will need.
The plaque will be installed outside the main building at the sites where FE technology and electron microscopes were developed. (1) Naka Division, Hitachi High Technologies Corporation (formerly Naka Works, Hitachi Ltd.) and (2) Central Research Laboratory, Hitachi Ltd.
Are the original buildings extant?
Details of the plaque mounting:
How is the site protected/secured, and in what ways is it accessible to the public?
The sites are guarded by security officers at the entrance of the sites. The entrance lobby of the building is open to visitors by registering at the security gate.
Who is the present owner of the site(s)?
The sites are owned by (1) Hitachi High Technologies Corporation and (2) Hitachi, Ltd.
A letter in English, or with English translation, from the site owner(s) giving permission to place IEEE milestone plaque on the property:
A letter or email from the appropriate Section Chair supporting the Milestone application:
What is the historical significance of the work (its technological, scientific, or social importance)?
First Practical Field Emission Technology and its Application to High Resolution Electron Microscopes, 1972–1984 Hitachi is a pioneer in electron microscopes, which it first started research and development in 1940, and has developed many electron microscopes. Its microscopes, beginning from the first made-in-Japan commercial electron microscope in 1942, have been highly evaluated from early on, for example the grand prize at the Brussels International Exposition in 1958. In the mid-1960's, Dr. A. V. Crewe (The University of Chicago) developed a field emission (FE) electron source and reported that an early version of an FE scanning transmission electron microscope (FE-STEM) succeeded to observe individual atoms. Hitachi collaborated with Dr. Crewe in the development of a practical FE electron microscope. After many years of fundamental research and development of FE stability technology, Hitachi constructed the world’s first commercial high-resolution FE-SEM (field-emission scanning electron microscope) in 1972. The FE-SEM brought about an innovative improvement in image resolution, from 15 nm to 3 nm. Its first application was to biology, which resulted in the first high-resolution observation of bacteriophages. The application of an enhanced in-lens electron optics design enabled ultra-high-resolution imaging of sub nanometers, which led to the first observation of the AIDS virus and more detailed images of bacteriophages by Professor Tanaka (Tottori University). Subsequent advances in technology resulted in current FE-SEMs having greatly improved resolution, i.e., 0.4 nm in the secondary electron image. The FE electron source was also applied to a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM). In physics, the application of an FE electron source with high interference characteristics to an FE-TEM developed for electron beam holography resulted in greatly improved coherency, i.e., from 300 to as many as 3000 lines of Fresnel fringes. The FE-TEM electron beam holography experimentally proved the Aharonov-Bohm effect in 1982, which confirmed the existence of gauge field and put an end to the vector-potential controversy. In the semiconductor industry, the critical-dimension SEM (CD-SEM), i.e., an FE-SEM dedicated to semiconductor-device micro-pattern in-line measurement, was commercialized in 1984. The CD-SEM is suitable for measuring non-conductive semiconductor devices without charge-up. Application of the Schottky electron source, an FE electron source proposed by Dr. Swanson in the 1980's, enabled long-term, stable and reliable CD-SEM operation, which is required for semiconductor production lines. CD-SEMs have been contributing to “scaling” as an indispensable metrology tool for device fabrication. Development of FE electron source technology enabled ultra-high-resolution imaging with stability and reliability. FE electron microscopes, i.e., FE-SEMs, FE-TEMs, FE-STEMs, and CD-SEMs, are now widely used for advanced research and development in many fields of science, technology, and industry, including physics, biotechnology, medical science, materials, and semiconductors.
What obstacles (technical, political, geographic) needed to be overcome?
For FE emission current stability, a steady-state ultra-high vacuum of 10^−8 Pa was necessary since residual gas molecules cause the FE emission current to fluctuate. This is a much higher vacuum than that of a conventional thermionic emission electron source (order of magnitude of 10^−4 Pa). Moreover, maintaining an ultra high vacuum under electron beam emission conditions is quite a challenge because the electron beam stimulates outgassing from the anode, which degrades the vacuum. Hitachi succeeded in establishing an ultra-high vacuum technology for the FE electron source. Patented "innerbake” technology, i.e., heating and degassing of a heater built into the anode, was the breakthrough. A “flashing" technique, i.e., short-duration heating of the cathode to remove the gas molecules, produced a stable, clean state of the cathode surface. Low outgas materials and surface treatment technology were also integrated and used to reduce the effect of the residual gas molecules. As a result, the FE emission current was fundamentally stabilized, enabling development of a stable and reliable FE electron source, which realized the development of practical high-resolution electron microscopes.
What features set this work apart from similar achievements?
The FE electrons are obtained by applying a high voltage (several thousand volts) to the tip of a metal needle (FE tip) with a radius of less than 100 nm. Application of a high electric field to the tip extracts electrons from the top of the tip due to the tunnel effect, whereas heating of the tungsten filament in a conventional thermionic emission source extracts thermionic electrons. Because of the high electric field, the FE electron current density (10^4–10^6 A/cm2) is three orders of magnitude larger than that of thermionic electrons (1–10 A/cm2). An FE electron source is ideally a point source, and the diameter of the virtual source ranges from 5 to 10 nm, which is 1/1000 the source size of thermionic emission (1–10 mm). The energy spread of FE electrons is 0.2–0.3 eV, which is much narrower than that of thermionic emission (2 eV). As a result, an FE electron source has 1000× the brightness, 1/1000 the source size, and 1/10 the energy spread of a conventional thermionic emission source. These features of the FE electron source result in much brighter and higher resolution images and high interference characteristics when applied to SEMs, TEMs, STEMs, and CD-SEMs. However, the instability of the FE emission current was an essential difficulty in the development of a practical FE electron microscope. After many years of fundamental research and development of FE electron source stability technology, Hitachi finally achieved a commercial FE-SEM featuring a stable and reliable FE electron source.
References to establish the dates, location, and importance of the achievement:
Supporting materials (supported formats: GIF, JPEG, PNG, PDF, DOC):