Like the wizard from the King Arthur legend, the new MERLIN electron microscope has a few tricks up its sleeve. The new Field Emission Scanning Electron Microscope, more conveniently described as a FESEM, from Carl Zeiss SMT AG is designed to overcome the standard trade-offs between image resolution and the analytical capability.
The electron microscope
Electron Microscopes have been around since the 1930s, and allow us to create still images of structures too small to see via standard optical cameras. They work by firing collimated beams electrons at a tiny structure to create the detailed image. Scanning Electron microscopes create the image by sweeping the beam of electrons across the surface to gradually image each portion of the surface being measure separately.
MERLIN
This new electron microscope is based around the new generation of the GEMINI core, known as the GEMINI II, which is what generates the electron beam.
This instrument is described as combining versatile analytical processes with a high spatial resolution. The enhanced GEMINI II column can achieve a spatial image resolution of 0.8 nanometers, which is less than half the width of a strand of DNA. This gives it the power to see incredible detail on the tiniest of objects.
On the analytical side, the system can provide a sample current of up to 300 nano-amperes which can be utilized for a variety of measurements, such as energy and wavelength dispersive X-ray spectroscopy and diffraction analysis of backscattered electrons.
Detection and Analysis
The detection system is made up of the in-lens Scattered Electron (SE) detector, which is used for standard imaging of the surface of the sample, the in-lens Energy-Selective Backscattered-electron (EsB) detector, which is used for detecting compositional contrasts on the surface of the sample being imaged, and the Angle-Selective Backscattered-electron (AsB) detector for widely dispersed backscattered electrons which contain specific information on the orientation of the various surfaces in the sample. A key consideration in the design of the MERLIN according to Carl Zeiss is ease of use. Its system designed for charge compensation has been creatively utilized to enable the ability to clean the sample while it is inside the microscope. Samples being imaged by an electron microscope need to sit inside a vacuum, to eliminate noise and interference from the air, which limits the amount of manipulation that can be done on the sample. This ability to frequently remove unwanted deposits from the surface of the sample allows for a much crisper image with minimum time and effort.
An additional benefit of the design of the MERLIN’s new electronic system is that it allows for multiple instrument configurations, with different detectors able to be added quickly to increase the adaptability of the system.