Skip navigation

FEI Titan Environmental Transmission Electron Microscope

Overview

The transmission electron microscope uses a high-energy electron beam transmitted through a very thin specimen to image and analyze the microstructure of materials with atomic scale resolution. The TEM can be employed in two different technical variants. In conventional TEM, the sample is illuminated by a near-parallel beam of electrons and the image is formed by a series of electromagnetic lenses. In scanning TEM (STEM), a fine probe (of less than 0.2 nm) is formed by optically focusing the incident electrons and is then scanned across the sample. The transmitted electrons are registered by detectors, and the resulting signal is displayed and captured by a CCD camera or spectrometer. In addition, interactions between electrons and the specimen can result in some of the incident electrons losing energies, or in the generation of X-rays, both with energies that are characteristic of the chemical composition of the specimen. Thus, by fitting the (S)TEM with an electron energy-loss (EEL) spectrometer or an energy-dispersive X-ray spectrometer, chemical information about the sample on the nanometer scale can be obtained. The information limit in a TEM is limited by aberrations in the electromagnetic lenses. Now, systems that are largely free of aberrations can be constructed with aberration compensation ("correctors") brought about by adding optical elements to a lens that exhibit the same aberrations as the lens but of the opposite sign. The Nano Center houses a spherical aberration-corrected FEI 80-300 environmental Titan (S)TEM with the following capabilities: High brightness field emission gun source, Spherical aberration (image) corrector (information limit 0.08nm at 300kV), Monochromator with energy resolution of ~ 0.2eV, Gatan Quantum 966 electron energy-loss spectrometer (for Energy-Filtered TEM imaging and electron energy-loss spectroscopy), High-angle annular dark field (HAADF) detector, Bright-field/Dark-field STEM detectors, Oxford SDD Energy-dispersive X-ray spectroscopy, Magnetic biprism for electron holography, Dual tilt axis tomography holder (for electron tomography), SuperTwin objective pole piece, environmental cell for controlled gas inlet into the sample holder area and analysis of the chemical composition of the atmosphere (up to 20mbar), US1000XP CCD camera with high-speed option. Operates at 80, 200 and 300kV.

Restrictions on Samples

Sample preparation for TEM generally requires more time and experience than for most other characterization techniques. A TEM specimen must be approximately 1000 Ã… or less in thickness in the area of interest. The entire specimen must fit into a 3mm diameter cup and be less than about 100 microns in thickness. A thin, disc shaped sample with a hole in the middle, the edges of the hole being thin enough for TEM viewing, is typical. The initial disk is usually formed by cutting and grinding from bulk or thin film/substrate material, and the final thinning done by ion milling. Other specimen preparation possibilities include direct deposition onto a TEM-thin substrate (Si3N4, carbon); direct dispersion of powders on such a substrate; grinding and polishing using special devices (t-tool, tripod); chemical etching and electropolishing; lithographic patterning of walls and pillars for cross-section viewing; and focused ion beam (FIB) sectioning for site specific samples. Artifacts are common in TEM samples, due both to the thinning process and to changing the form of the original material. For example surface oxide films may be introduced during ion milling and the strain state of a thin film may change if the substrate is removed. Most artifacts can either be minimized by appropriate preparation techniques or be systematically identified and separated from real information.

 

Contact Information

Ann Marshall
office: (650) 723-3572; lab: (650) 725-4684

Ai Leen Koh
office: (650) 723-1686; lab: (650) 723-1575

Cognizant Faculty Advisor

Robert Sinclair

 

Research Examples


In this research, the FEI Titan TEM was used to study quantum plasmon resonancesof individual metallic nanoparticles. Applied techniques include aberration-corrected TEM imaging and monochromated scanning TEM electron energy-loss spectroscopy (EELS). For more information: School of Engineering Press Release. Reference: Scholl, Koh, Dionne, Nature 483 (2012) - doi:10.1038/nature10904

 

Getting Started

Pre-requisites for Titan training:

  • Must have completed Tecnai trainings
  • Must demonstrate competency on the Tecnai
  • Pre-requisites for specific modules follow
    • Titan Basics, alignments + Cs image corrector tuning
      • Compulsory for all Titan users
      • Completion of basic training is necessary for training on other techniques
    • STEM:
      • Must be familiar with STEM on the Tecnai
    • EELS (STEM and/or TEM mode)
      • Must have completed Titan STEM training module
    • Monochromator
      • Must have completed Titan EELS training module
    • Energy-filtered TEM/ Elemental Mapping
    • Tomography (TEM mode)
    • Tomography (STEM mode)
      • Must have completed Titan STEM training module
    • Lorentz imaging
    • Electron holography
    • High-resolution imaging and through-focal series acquisition and reconstruction
    • EDS analysis
      • Must be familiar with EDS on the Tecnai
    • Environmental TEM