Scanning Electron Microscopy

Hitachi SU6600 Scanning Electron Microscope

The Hitachi SU6600 Scanning Electron Microscope (SEM) utilizes a focussed beam of high energy electrons to generate a variety of signals at the surface of solid specimens. These signals that arise due to electron-sample interactions which reveal information regarding the external morphology, chemical composition, crystalline structure and orientation of materials that make up a given sample. By acquiring these signals, a 2-dimensional image is generated that displays spatial variations in these properties. The Hitachi SU6600 SEM is equipped with EDX and WDX facilities for elemental analysis.

Principle

In a typical scanning electron microscope, electrons are accelerated towards a sample with significant amounts of kinetic energy. Following the deceleration of these electrons in the solid samples, they give rise to signals as a result of electron-sample interactions. Secondary electrons are a part of these signals that are produced and are used in the production of SEM images. Backscattered electrons may also be used in the production of the SEM image alongside the secondary electrons. Other signals that are produced include characteristic X-rays, cathodoluminescence, specimen current and transmitted electrons. Being a Field Emission SEM, the Hitachi SU6600 allows a smaller spot size which leads to the production of high-resolution images. The instrument utilizes advanced variable pressure technology and an improved Schottky field emission electron source that provides exceptional imaging along with a high probe current with great stability. The variable pressure technology allows the SEM to operate under high vacuum conditions (≤10-8 Pa) and under low vacuum conditions (10-300 Pa). Using energy dispersive X-ray spectroscopy (EDX), the identification and quantification of elements at areas/point locations of the specimen are possible. Wavelength dispersive X-ray spectroscopy (WDX) can be used in conjunction with EDX in order to identify spectrally overlapping elements.

Strengths

• Rapid, high resolution imaging
• Quick identification of elements present
• Provides images with high depth of field

Limitations

• Samples must be solid and they must fit into the microscope chamber
• Size restrictions may cause the initial sample to be cut
• The ultimate resolution is a strong function of the sample chemistry and the stability of the sample against the electron beam
• Samples with magnetic properties cannot be analysed

Applications

• Materials research: High resolution imaging and analysis of novel-nano materials, analysis of coatings and thin films, imaging of various forms of carbon and other 2D materials, imaging, analysis and structural differentiation of polymer materials
• Life Sciences: High resolution imaging and high throughput analysis of cryo-fixed biological samples, research on biomaterials such as teeth, bone, collagen-containing biopolymers like hair. Plant materials such as pollen grains, leaves could be analysed to observe structurally important features.
• Geoscience and mineralogy: Characterization of minerals and rocks
• Natural resources: Fast and accurate investigation of mineralogical core samples
• Industrial applications: Failure analysis of materials and manufactured components, imaging and analysis of steels and metals, inspection of medical devices, characterization of semiconductor and electronic devices in process control and diagnostics

Technical Specifications

• Signals detected: Secondary electrons, backscattered electrons and X-rays
• Elements detected (For EDX and WDX): 11Na Onwards (For quantification of elements)
• Maximum resolution: 1.2 nm
• Maximum magnification: 600,000x
• 6 detectors available (Secondary Electron Detector, Environmental Secondary Electron Detector, Back Scattered Electron Detector, EDAX detector, Transmission Electron Detector, WDS detector)