Review of the development of scanning electron microscopy

The development history of scanning electron microscope (SEM) is like a scientific adventure novel. Its origins and development are closely related to scientists' constant curiosity and pursuit of knowledge.

In the early 20th century, with the rapid development of physics and materials science, scientists became keenly interested in the microscopic world. When the rapid development of electronic physics collides with the resolution limit of traditional optical microscopes, scientists have been unable to see microscopic details below 200 nanometers. They urgently need a higher-resolution microscope to observe smaller-scale material structures.

This is the realistic background for the emergence of scanning electron microscopy.

The ideas of transmission electron microscope (TEM) and scanning electron microscope (SEM) were both proposed in the early 1930s. In 1931, M. Knoll and E. Ruska of Germany modified a high-voltage oscilloscope with a cold cathode discharge electron source and three electron lenses, and obtained an image magnified 12 times. What they invented was a transmission electron microscope (referred to as a transmission electron microscope). This invention proved with facts that it is feasible to use an electron microscope to magnify and image tiny objects. In 1934, through the continuous efforts and improvements of Ven Borries and Ruska, the resolution of the transmission electron microscope reached 50nm, breaking through the resolution limit of the optical microscope, and the transmission electron microscope began to receive attention from the scientific and technological community.

In the 1940s, Hill in the United States invented the astigmatism absorber, which solved the problem of the beam spot not being round enough due to the incomplete rotational symmetry of the electromagnetic lens in the electron microscope, and made a new breakthrough in the resolution of the electron microscope. Due to the year-by-year improvement in electron microscope design capabilities and mechanical processing levels, as well as the continuous improvements of scientists, electron microscopes have reached the current high-resolution level.

The key figures who first proposed and developed the scanning electron microscope were the German physicist Max von Laue and the Swedish physicist August K. Tufte. In 1938, they designed and built the earliest prototype of an electron microscope, but further development was hampered by technical limitations and the outbreak of World War II.

Since the 1950s, a new generation of scientists has begun to join the research on scanning electron microscopy, and scanning electron microscopy has entered an era of rapid development. In 1956, American physicist Erwin Müller developed the earliest feasible atomic-scale imaging device and is regarded as the founder of scanning electron microscopy. In 1965, Japanese scientists Hiroshi Tanabe and Ryoei Hino built the first commercial scanning electron microscope and began to promote and apply this technology. In the 1970s, the German Carl Zeiss Company, the Dutch Royal Philips Company, and the American Erica Company began to mass-produce scanning electron microscopes, making them gradually popular. In the 1980s, American physicist Shuichi Yoshida proposed the concept of Field Emission Scanning Electron Microscope (FE-SEM), which further improved the resolution and precise imaging capabilities of scanning electron microscopes.

In recent years, with the rapid development of nanotechnology, scanning electron microscopy has become more and more widely used in fields such as materials science, biological science, and nanoscience, continuously promoting the innovation and progress of its technology.

In less than a hundred years, electron microscopes have developed rapidly. The resolution and detection functions of electron microscopes have also been continuously improved and increased. Models with the same functions have become smaller and smaller, their application ranges have become wider and wider, and their cost performance has also improved. Improvement and popularization are also accelerating. Standing on the "shoulders of giants", scientists have continuously proposed new theories, designed key instruments and equipment, and promoted the advancement and commercial application of scanning electron microscope technology.

Overall, the history of scanning electron microscopy is a process of active exploration and innovation. From its earliest prototypes to today's high-resolution, high-performance equipment, scanning electron microscopes have become an indispensable scientific tool, revealing the mysteries of the microscopic world to us.