The Electron Microscopy Unit of the University of Ioannina is located at the new Building basement of the Department of Materials Science Engineering and it is consisting from the following equipment (primary and secondary):

• Two (2) Ultra-Cryomicrotomes for thin sections used in TEM [1 through donation from DMSE/MIT and Professor E. L. Thomas) and a new one as of May 2012 (four diamond knives, two for cryomicrotoming and two for environmental microtoming) from Leica Instruments through competitive funding, Leica EM UC7 Ultramicrotome]
• One (1) High-Resolution Transmission Electron Microscopy (HR-TEM) from JEOL (JEM-2100, LaB6 filament)
• One (1) Scanning Electron Microscopy-Low Vacuum (SEM-LV) from JEOL (JSM-6510LV, LaB6filament)
• Various secondary equipment such as: Precision Ion Polishing system (PIPS), cross-sectional kit, ultrasonic cutter, disc grinder, dimple grinder from Gatan Inc.

Two (2) Ultra-Cryomicrotomes for thin sections used in TEM (1 through donation from DMSE/MIT and Professor E. L. Thomas) and a new one as of May 2012 from Leica Instruments through competitive funding, Leica EM UC7 Ultramicrotome)

With these instruments (Figure 1) the ability to obtain thin sections from bulk films as low as 5 nm is possible. They are used in ambient conditions (environmental microtoming) and at cryogenic conditions as low as -160⁰C (ultra-cryomicrotoming).

The usual requirements for the obtained thin sections to be observed by TEM is for their thickness to range from 20 nm up to 70 nm. These thickness values depend on the specimen, the staining requirements, the accelerating voltage at which they will observed and their sensitivity (thermal, degradation/decomposition, cross-linking) under the electron beam exposure.

Glass knives and diamond knives are used for the collection of the sections. The diamond knives are differentiated according to the conditions used (ambient or cryogenic). Deviations and deformation of the sections due to static electricity (especially during ultra-cryomicrotoming conditions) are substantial. In total there are four diamond knives, two for ultra-cryomicrotoming and two for environmental microtoming.

Many different preparation protocols can be used for obtaining the desired thin sections in both conditions and the grids used for deposition of the sections are variable according to demand, type of sample and imaging requirements.

Figure 1. Ultra-Cryomicrotomes. Left image: The new as of May 2012 from Leica Instruments, model: Leica EM UC7 Ultramicrotome, right image: The older microtome through donation from DMSE/MIT, model: Reichert- Jung FC 4E cryo-ultramicrotome.

In Figure 2 additional images are shown for the working space of the ultra-cryomicrotome Leica EM UC7 Ultramicrotome under cryogenic conditions. Figure 2 (top image) indicates the area where specimen and knives (glass and diamond) are located as well as the control panel is observed. Figure 2 (center image) the area of the specimen and the diamond knife is specified under cryogenic conditions (ultra-cryomicrotoming) and magnified further in Figure 2 (lower image) for better observation.

Figure 2. Top image: area where specimen and knives (glass and diamond) are located as well as the control panel, center image: area of the specimen and the diamond knife, bottom image: magnification of specimen and diamond knife for better observation.

High-Resolution Transmission Electron Microscopy (HR-TEM) from JEOL (JEM 2100HR, LaB₆ filament) 

The high-resolution electron microscope of the Electron Microscopy Unit of the University of Ioannina is shown in Figure 3.

Figure 3. High Resolution Transmission Electron Microscope (HRΤΕΜ), model JEM 2100HR (JEOL Ltd).

General Information

The transmission electron microscope consists of two basic systems: the illumination system and the image projection system.

The illumination system comprises the gun and the condenser lenses and its role is to take the electrons from the source and transfer them to the specimen. The electron gun is normally fitted with a tungsten filament cathode as the electron source. The electron beam is accelerated by an anode typically at 100-200 keV, while advanced TEMs can reach up to 1MeV which provides better examination of thicker specimens.

The image projection system comprises from the objective lens, the intermediate lens, the diffraction lens, the projection lens, the viewing luminous screen for the observation of the specimen and the photographic camera. The first and most important magnification of the sample is performed by the objective lens where the rest of the lenses create the final magnification.

The major features are dependent on the system, the goniometer and the mounting. More specifically:

System: By creating the status display of the basic unit and operation screen using JEOL’s graphical user interface based on MS Windows software, this system is easy to operate, even for beginners.  In addition, by providing powerful external control functions, it lets you program a series of operations and facilitates useful collaboration with other peripheral equipments.

Goniometer: By not only drastically enhancing the after-drift and tilting performances of the stage, but also completely computerizing the stage-control system, the operation environment of the stage has been substantially improved over any conventional instrument.  Moreover, piezoelectric drive mechanisms make sub-nanometer stage movement possible.

Mounting: The mounting not only enhances the vibration- and earthquake-resistance performance by supporting the column nearest the center of gravity of the electron microscope, but also it affords you to select the best mounting according to the floor vibration in the installation room by increasing the choice of mountings.

Specifications of the TEM instrument

The JEM-2100HR is equipped with EDS, STEM mode, EELS and more specifically:

• The instrument has high resolution capabilities to successfully gain high quality analysis, qualitive determination and high accuracy automatic elemental recognition.
• It has the capability to improve the quality of the gained spectra through X-ray aperture and no rotation of the image or the diffraction is evident when the magnification or the optical length are changed.
• With the right objective lens, it indicates resolution at the atomic scale from spot to spot as low as 0.25 nm or less and resolution of crystal lattices as low as 0.15 nm or less. In that manner the observation of interfaces is possible and crystallographic characteristics can be observed which are necessary for composite materials and copolymers especially during high symmetry projections.
• Except from the single tilt holder, it has the possibility to use additional holders such as: dual tilt, rotate tilt, vacuum tilt and cryo-tilt (all of them have been acquired and are available).
• Possibility of imaging acquisition through a CCD camera with 2048 x 2048 pixels resolution, size pixel 24μmx 24μm and with high sensitivity.
• The image transfer is possible through FireWire in the computer for immediate observation, digital processing, and storage.
• The instrument can be used as STEM (Scanning-Transmission Electron Microscope) to be applied for calculations of mass per unit length for biological specimen with dimensions of 1 μm but with low thickness (~ <100nm).
• Using Energy Dispersive Spectrometry – EDS and X-rays it can analyze light elements (as low as B) and the ability to create qualitive mapping of samples with very fast elemental analysis.
• Using Electron Energy Loss Spectroscopy – EELS it can determine atomic composition, chemical bonds, electron properties of conductivity zones, interfacial properties etc.

The general specifications of the instrument are (according to basic parts as given below):

The main system configuration (JEM-2100HR) which is functional in the Electron Microscopy Unit of the University of Ioannina, since it is High-resolution is as follows:

EM-21000BU.          Electron Microscope Basic Unit

EM-20500                CM Lens Unit

EM-20720              High Resolution Polepiece

EM-20080              High Contrast Objective Aperture

EM-23110              SIP Vacuum Pump

EM-27112PCU       Computer Unit

EM-27121MON      Main Monitor

EM-08010             Air Compressor

Scanning Electron Microscopy-Low Vacuum (SEM-LV) from JEOL (JSM-6510LV, LaB₆ filament)

The Scanning Electron Microscopy-Low Vacuum (SEM-LV) of the Electron Microscopy Unit of the University of Ioannina is shown in Figure 4.

Figure 4. Scanning Electron Microscope (SEM).