This Small Business Innovation Research (SBIR) Phase I project will develop a very low-cost, easy to use scanning electron microscope (SEM) for students and small businesses that cannot afford them today. The project achieves this goal by eliminating the costly, complex high vacuum system. In traditional SEM's, the high vacuum system prevents rapid failure of the electron emitter. Phase I will develop an innovative new electron source that has long life and high performance without the need for a high vacuum system. The proposed electron source protects the emitter from rapid oxidation and evaporation even in poor vacuum conditions. These new electron sources will be evaluated for brightness and lifetime in both high vacuum and low vacuum environments. The sources will then be evaluated in a modified SEM without the high vacuum system. Finally, a new SEM will be designed for low cost, ease of use and good performance. This SEM will have comparable performance to existing SEM's at a substantially lower cost.
The broader impact/commercial potential of this project will be to bring one of the most important tools of science and technology - the electron microscope - to students and small businesses. Existing electron microscopes are large, difficult to use and expensive to buy and maintain. This project aims to produce a simple, rugged and inexpensive scanning electron microscope (SEM). The proposed SEM can be used in K-12 schools, vocational schools and small colleges as well as small businesses that cannot afford present-day SEM's. SEM's are becoming essential in manufacturing both "low-tech" products (e.g., cosmetics, textiles and food processing) and "high-tech" products (e.g., microelectronics, medical devices and pharmaceuticals). Access to a SEM will give small businesses an advantage for better process and quality control, enabling them to compete with larger companies that already have SEM's. Students who learn how to use a SEM will have an advantage seeking high-tech jobs. Scientists and engineers performing R&D at small companies or colleges will be have access to one of the basic tools of advanced technology, the SEM.
What do electron microscopes and rocket engines have in common? If DLA Instruments succeeds, the same materials used to coat rocket nozzles and jet engine turbine blades will be used to make a new type of electron microscope. At the core of an electron microscope is an electron emitter—usually a tungsten filament. To create a beam of electrons, the filament is heated until electrons boil off. Just like a light bulb, if the filament is switched on in air, it will burn up quickly. In a light bulb, the oxygen is removed so that the filament does not burn up. In an electron microscope, the filament is under vacuum: all the gas is pumped out of the system. The pumping system to remove the gas is heavy, expensive and complex, while the rest of the electron microscope is relatively simple with no moving parts. Eliminating or simplifying the pumping system would dramatically reduce the cost, size and complexity of electron microscopes. Ultra-High-Temperature Ceramics, UHTC’s, are materials that can withstand extremely high temperatures without burning up. Many of these materials can be heated to thousands of degrees without melting or burning up, which is why they are used to coat rocket engines and turbine blades. Some of these UHTC’s also emit electrons when hot, which makes them potential materials for the emitter in electron microscopes. If UHTC’s can be turned into effective electron emitters, then the need for expensive pumping systems in electron microscopes can be reduced or even eliminated. There would be plenty of advantages to eliminating the high-vacuum system from an electron microscope. First is the cost: a high-vacuum system can account for 50% or more of the cost of the microscope. Second is the complexity: a high-vacuum system is delicate. It typically consists of several pumps working together to achieve high vacuum. One of these pumps, the turbo-molecular pump, is a high-speed fan that sucks gas atoms from the system. It spins at 30,000 rpm, and costs $10,000 or more. If it is bumped or moved while operating, the rotating fan may shatter, ruining the pump and possibly the electron microscope. For these reasons, electron microscopes have been prohibitively expensive and too complex to use in classrooms and small businesses. In this SBIR, we measured the performance of UHTC’s as electron emitters. We operated these emitters at relatively high pressures—much higher than used in existing electron microscopes. We found that the emitters performed well under these conditions and maintained their shape and electrical properties even when the pressure was thousands of times higher than standard for electron microscopes. With continued development, UHTC electron emitters could create a whole new market for electron microscopes, bringing the technology to schools and small businesses.
