Current Model: Hitachi SU-70 Field Emission Gun Scanning Electron Microscope

The Hitachi SU-70 is a high resolution field emission scanning electron microscope capable of high resolution imaging (1.0 nm at 15 kV) and in-depth sample analysis in both low and high mag. modes.

The Hitachi SU-70 is one of the highest resolution microscopes available on the market and features several specialised in-lens detectors in addition to STEM (Scanning TEM) and EDX/WDX (Energy Dispersive X-Ray analysis and Wavelength Dispersive X-Ray analysis) capability. These analytical components provide complementary information in terms of elemental analysis, compositional point analysis and mapping. The SU 70 also allows reduced charge-up imaging and low voltage imaging.

Typical samples:

Metals, Polymers, Coated Components, Powders

Principle:

A scanning electron microscope produces images of a sample by scanning with a focused beam of high-energy electrons emitted from an electron gun (Tungsten filament). This generates a variety of signals at the surface of solid specimens. The signals that derive from electron-sample interactions reveal information about the sample including external morphology (texture), chemical composition, and crystalline structure and orientation of materials making up the sample. The SEM utilizes vacuum conditions and uses electrons to form an image; therefore special preparations must be made with the sample:

Typical Preparation Steps:

  • Wet Samples: All water must be removed from the samples because the water would vaporise in the vacuum.
  • Metal Samples: All metals are conductive and require no preparation before being used.
  • Non-Metal Samples: All non-metals need to be made conductive by covering the sample with a thin layer of conductive material. This is done by using a device called a “sputter coater.”
  • The SEM is critical in all fields that require characterisation of solid materials. Most SEM’s are comparatively easy to operate, with user-friendly “intuitive” interfaces. Many applications require minimal sample preparation. However, the SEM Samples must be solid and they must fit into the microscope chamber. Maximum size in horizontal dimensions is usually on the order of 10 cm; Vertical dimensions are generally much more limited and rarely exceed 40 mm. For most instruments samples must be stable in a vacuum on the order of 10-5 – 10-6 torr.

 Analysis Process:

The sample is prepared for analysis, and placed onto the specimen stage of the SEM. The experiment is run and the beam hits the sample, electrons and X-rays are ejected from the sample. Detectors collect these X-rays, backscattered electrons, and secondary electrons and convert them into a signal that is sent to a screen similar to a television screen. This produces the final image for analysis.

The elemental composition of materials can be obtained by the Energy Dispersive Spectrometer (EDS) by measuring the energy and intensity distribution of X-ray signals generated by a focused electron beam on the specimen (EDS).

What is given here is only a simple example which highlights the capability of NMR spectroscopy.  It can be used to analyse simple molecules like this up to large, complex proteins.  Its applications reach far beyond just chemical analysis with uses in medical imaging, the petroleum industry, as process controls and in the future perhaps even quantum computing

Technical Specifications:

  • Schottky (thermal) field emission electron source
  • Imaging resolution of 1nm at 15 KV and 1.6nm at 1 kV
  • Magnification: Low mag. mode 20x – 2000x; High mag. mode 100x – 800,000x
  • Accelerating Voltage: 0.5 kV – 30 kV
  • Probe Current: 1 Ρa to >200 Na.
  • Specimen Stage: x = 110 mm, y = 110 mm, z = 1.5 – 40 mm, tilt =-5 – +70 degrees
  • Flexible Detection System utilising: Highly efficient in lens, Lower and Upper
  • Secondary Electron Detectors, Low and High Angle Backscattered Electron Detectors and STEM Detector.
  • Anti-Contamination Trap “Cold Finger” used to reduce sample contamination