Several well (and also several not so well) publicized incidents of unethical conduct have raised the concerns of scientists, politicians and common folk that the truth and only the truth may not always emerge from scientific investigation. While this is a problem which clearly needs attention, I believe that Science alone of all fields of human endeavor has built in mechanisms which ensure that truth will emerge sooner or later, usually sooner (although some frauds, for example the Piltdown hoax, survived for quite a long time). This self correcting feature arises from the fact that today's interpretations are repeatedly tested against nature, whenever new methods or hypotheses arise. Only correct beliefs survive this repeated scrutiny. The misguided workers who for whatever reasons “cheat” or get so personally involved that they fall in traps made of their own gullibility are eventually discovered and at the very least lose the recognition that they longed for.

Electron beam lithography is a term well known in the world of microelectronics. It provides an effective but costly solution for producing the smallest electronic devices (transistors, memories, etc). Many fields of science and research also require small structures below the one micron dimension. The ability to generate these structures “in house” without going to external sources has been a luxury only the largest corporations and universities could afford. Even when a production lithography system is available, the time allocated for research work can sometimes be extremely limited. Those with the need for these small devices are now realizing there is new way to get the most use from their SEM, STM or STEM.

In the past few years, experimental e-beam systems have been developed by making use of the basic capabilities of the scanning electron microscope. Mow a variety of home built and commercially available systems are being used throughout the world. The mast basic system can take control of the e-beam in the SEM and write a simple pattern on a sample coated with materials sensiiive to electrons.

Great strides have been made in the last decade in high resolution transmission electron microscopes (TEMs) which can also provide elemental information via energy dispersive X-ray analysis (EDX) or energy loss spectroscopy (EELS), and proponents of various TEM techniques make bold claims. Convergent beam elecjron diffraction and microdifff action shine as techniques for defect structure analysis and means for solving crystal structures. The spectroscopies can now be used to map chemical state information at a level which until recently might be encountered in science fiction. As a pure imaging device, electron holography holds great promise for providing Ehe ultimate (would you believe 0.1Å?) imaging resolution. Although conventional TEMs will never approach this, it appears that we are learning more and more about less and less, until we will soon know everything there is to know about nothing.

Over the years, we've seen major developments in electron source technologies in response to the demands for better performance. This article presents a brief overview of the cathode technologies in use today.

Two types of electron sources are used in commercially available scanning electron microscopes (SEMs), transmission electron microscopes (TEMs), scanning Auger microprobes, and electron beam lithography systems: thermionic and field emission electron cathodes. Thermionic cathodes reiease electrons from the cathode material when they are heated while field emission cathodes rely on a high electric field to draw electrons from the cathode material.