Case Study Peking University 

The quality of electron microscope images can be affected by interference from magnetic fields that are created by everyday equipment out of the researcher’s control, such as lifts and trains. Scientists are using field cancelling systems to escape this disturbance, increasing the performance of the instrument and, therefore, the resolution of images. Researchers at Peking University, China, have recently installed one of these set-ups to overcome the image distortion caused by external interference from magnetic fields.

Electron microscopes are powerful, but sensitive tools used for obtaining high resolution images in many technical disciplines – from cell biology to materials science and engineering – and are integral to understanding the intricate structure of many biological and inorganic specimens. However, interference from surrounding magnetic fields generated by day-to-day electrical equipment can affect the resolution of electron microscopes, decreasing the quality of images obtained. Users of these sophisticated microscopes often turn to cancelling systems that drastically reduce both AC and DC magnetic fields to overcome these problems. Dr Jing Ju, a researcher in the College of Chemistry and Molecular Engineering at Peking University, China, explained: “My lab is the core facility for use of the scanning electron microscope (SEM), and we assist many departments and research groups with a range of projects, from studying bacteria and materials to the analysis of nanoparticle crystal structures. For SEM, we need a very high resolution image – typically a 200,000x magnification of the sample – with minimal interference.”

Unwanted interference 

“Our laboratory is in a very old building and, unfortunately, there is a large electricity power cabinet emitting AC interference nearby, as well as a subway 100 metres away contributing to high levels of DC magnetic fields and acoustic noise from vibrations. This level of interference deflects the electron beam of the microscope, distorting the image. Our SEM system ideally needs to operate with an external magnetic field of less than one milligauss, but DC fields measured on the z-axis were 19 milligauss and AC fields on the x-axis were more than 21 milligauss. Both AC and DC magnetic fields were regularly out of range in our lab according to the SEM requirements, and so we explored using a cancelling system to stabilise the field by creating forces to oppose those from external factors.”

Cancelling out the noise

“We started using the SEM in around 2014, but it was only recently that we were introduced to different options for removing unwanted signals. After discussing with local advanced laboratory equipment supplier, Ke Chieh Tech, it was suggested that we tried one of Spicer Consulting’s systems, and the company performed a live demonstration of the cancelling equipment for us to see. We were so impressed with the efficiency of the instrument that, at the beginning of 2018, we purchased Spicer’s SC24 magnetic field cancelling system, and are amazed at the increase in quality of images we can produce. In fact, we can now reach a magnification of 300,000x, which is a huge improvement in resolution. The dynamic nature of the SC24 means that it detects and reacts to field changes within 100 microseconds, ensuring any interference is quickly cancelled out, which is very important in such a busy laboratory.”

A trusted partnership

“Our local supplier assisted in the installation of the SC24 system and we were taught how to maintain the equipment, which is very straightforward to do even for someone with minimal experience. Whenever we have needed support, the company has been readily available by phone or email to answer any questions and provide solutions to our problems, which have always been quick to fix. We are planning on moving the SEM to a new site soon, and will be using the company’s consultation service to assist in surveying the new environment, in order to detect any possible sources of interference and confirm whether it will be a suitable location. We are incredibly pleased with the performance of the cancelling system, and the support that we have received, and look forward to continuing to work with Spicer instruments in the future,” Jing concluded.

Spicer Consulting provides solutions to reduce magnetic field interference for higher resolution electron microscopy. Contact us to find out here.

About Spicer Consulting Limited

Since it was established in 1988, Spicer Consulting has built a world-wide reputation in magnetic field cancelling for Electron Microscopes and similar instruments. Today, working with equipment manufacturers and users alike, the company is recognised as an industry expert in maximising the performance of electron microscopes, electron beam lithography systems, CD metrology and focused ion beam tools. 

Spicer Consulting magnetic field cancelling systems protect sensitive equipment in the world's leading laboratories, universities and semiconductor manufacturing plants, as well as in the test facilities of electron and ion beam equipment manufacturers. Its magnetic field, vibration and acoustic analysis systems have been adopted as standard equipment for the conduct of site surveys by leading equipment manufacturers. Spicer Consulting is located in Stewartby, Bedfordshire, within the United Kingdom’s Golden Triangle of elite universities in London, Cambridge and Oxford.