SEM Electron Gun

Background

The acceleration of electrons within a vacuum chamber has led to many technological advances and many scientific discoveries. Some of the latest technological tools using an electron gun are nanotechnology tools, like the Scanning Electron Microscope (SEM). The SEM has helped to open up the world at the nano-level (10^-9 m or nanometre (nm) level). An SEM was created/invented in the mid-to-later part of the 20th century. The SEM has a resolution down to 10 nm (10 x 10^-9 m) and has a much greater (focused) depth of field than optical microscopes (providing a 3D-like image). This is all done with accelerated and focused electrons—in a beam. To understand or even explain the SEM from a physics perspective, you need to use concepts such as accelerating electrons in an electric field and focusing electron beams in a magnetic field

There are now many different types and sub-types of microscopes—or should we now say nanoscopes? Scientists now have, for example, scanning electron microscopes (SEMs), scanning probe microscopes (SPMs), atomic force microscopes (AFMs), and scanning tunneling microscopes (STMs). The new worlds of evidence that can be obtained from these microscopes have revolutionized scientific work at the nano-level and normalized work at the micro-level.

We now have nano-technology which focuses on inventing technologies and making them work, and we have nano-science which focuses on creating descriptions, explanations, and predictions related to the nano-world. Technology often focuses on how, while science focuses on why. Until the 20th century there were no examples of science leading technology; technologies were invented and then science came along to explain the technology (e.g., the battery was invented in the early 1800s but explained by science only in the early 1900s). The modern collaborative and interdisciplinary work between scientists, engineers, and technologists has produced rapid advances in both fields.

Whether science led technology or technology led science in the invention of the SEM may be debated, the collaborative nature of the invention is hard to debate. In this lesson we will use science to explain the technology rather than predict the technology.