MIRA3 (SEM)

Figure 1. The TESCAN MIRA3 SEM

SEM is mainly made up of electronic optical systems, electronic systems, display components and vacuum system.

The working principle of the SEM is to scan the sample with a very fine beam of electrons to stimulate secondary electrons on the surface of the sample. The amount of secondary electrons is related to the incident angle of the electron beam, thus reflects the surface morphology of the sample. The secondary electrons are collected by the detector and converted by the scintillator into an optical signal which can translate into electrical signal using photomultiplier. An amplifier can control the intensity of the electron beam on the screen, finally a scanned image synchronized with the electron beam is displayed. The image is a stereoscopic image that reflects the surface structure of the specimen.

The SEM features a high-brightness Schottky emitter allowing users to generate high-resolution images with low noise and resolution down to 1 nm. It is built around the large XMU chamber, which gives researchers the flexibility to analyse samples as large as 300 mm wide. It will allow researchers to investigate their materials at the micro and nano level, helping them to better understand how these structures behave.

The microscope also includes BDM (beam deceleration mode) imaging, which will allow us easily image sensitive samples such as nanoparticles under low-vacuum conditions which more accurately replicate ambient operating conditions. The included Peltier stage also allows them to investigate how samples behave at temperatures between -70 and 50°C.

When combined with the Thermo Scientific EDS system, QUT researchers will be able to look at the elemental composition of their samples. By looking at the homogeneity, elemental distribution and changes in composition using the Pinnacle analytical software package, the researchers will gain an insight into the relationships between chemistry and performance.

"This is the first TESCAN microscope that we have purchased and we're looking forward to having it installed and adding to the capability in our lab," said Dr Riches. "We already envisage it being used to investigate such things as polymer scaffolds for bone healing, corrosion studies on stainless steel through to multilayer materials for solar cell devices."

"In addition, the EBL (electron beam lithography) system will be a useful complement to the ion beam instruments that we have for device preparation, while the plasma cleaner will help us control contaminants in the column from samples that may break down on exposure to the electron beam in vacuo."