Source transmission electron microscopy

L. Reimer. Transmission Electron Microscopy Physics of Image Formation and Microanalysis. Springer-Verlag, Berlin, 1984. This is an advanced but comprehensive source on TEM. Reimer also authored a companion volume on SEM. 

Alternatives to XRD include transmission electron microscopy (TEM) and diffraction, Low-Energy and Reflection High-Energy Electron Diffraction (LEED and RHEED), extended X-ray Absorption Fine Structure (EXAFS), and neutron diffraction. LEED and RHEED are limited to surfaces and do not probe the bulk of thin films. The elemental sensitivity in neutron diffraction is quite different from XRD, but neutron sources are much weaker than X-ray sources. Neutrons are, however, sensitive to magnetic moments. If adequately large specimens are available, neutron diffraction is a good alternative for low-Z materials and for materials where the magnetic structure is of interest. 

Transmission electron microscopy (TEM) is a powerful and mature microstructural characterization technique. The principles and applications of TEM have been described in many books [16 20]. The image formation in TEM is similar to that in optical microscopy, but the resolution of TEM is far superior to that of an optical microscope due to the enormous differences in the wavelengths of the sources used in these two microscopes. Today, most TEMs can be routinely operated at a resolution better than 0.2 nm, which provides the desired microstructural information about ultrathin layers and their interfaces in OLEDs. Electron beams can be focused to nanometer size, so nanochemical analysis of materials can be performed [21]. These unique abilities to provide structural and chemical information down to atomic-nanometer dimensions make it an indispensable technique in OLED development. However, TEM specimens need to be very thin to make them transparent to electrons. This is one of the most formidable obstacles in using TEM in this field. Current versions of OLEDs are composed of hard glass substrates, soft organic materials, and metal layers. Conventional TEM sample preparation techniques are no longer suitable for these samples [22-24], Recently, these difficulties have been overcome by using the advanced dual beam (DB) microscopy technique, which will be discussed later. 

Figure 3. Example of intracellular membrane organisation a transmission electron microscopy (TEM) image of a section through the thylakoid stack from a chloroplast. (Source http //www.ru.ac.za/administrative/emu/grl0p6.htm, Reproduced with permission from Dr. R. Cross)...

Powdered, particulate MCM-41 molecular sieves (Si/Al = 37) with varied pore diameters (1.80, 2.18, 2.54 and 3.04 nm) were synthesized following the conventional procedure using sodium silicate, sodium aluminate and C TMAB (n = 12, 14, 16 and 18) as the source materials for Si, A1 and quaternary ammonium surfactants, respectively [13]. Each sample was subjected to calcination in air at 560 °C for 6 h to remove the organic templates. The structure of the synthesized material was confirmed by powder X-ray diffraction (XRD) and by scanning/transmission electron microscopy. Their average pore sizes were deduced from the adsorption curve of the N2 adsorption-desorption isotherm obtained at 77 K by means of the BJH method (Table 1). 

In this Datareview, bulk growth of GaN and AIN by a sublimation method and of GaN by a sublimation sandwich method is described. The source powder was analysed. The bulk GaN obtained was characterised by XRD (X-ray diffraction), TEM (transmission electron microscopy), and so on. 

The oxidation of carbon can also be catalyzed. Two fundamentally different cases should be discriminated. Transition metal oxides and carbides were found to be efficient local sources of atomic oxygen increasing its abundance much above the uncatalyzed case. Streams of diffusing oxygen atoms created decorated pathways of nonselective oxidation of basal plane sites as detected by transmission electron microscopy [117, 118]. 

Ryoo et al. reported the first ordered mesoporous carbon, CMK-1, using cubic MCM-48 as template and sucrose as carbon source. CMK-1 exhibited a highly ordered cubic structure, as confirmed by transmission electron microscopy (TEM). However, x-ray powder diffraction patterns indicated that CMK-1 underwent a structural transformation upon the silica removal due to the two disconnected porous systems separated by the silica wall. ... 

Transmission electron microscopy (TEM) has been used extensively in biology for direct visualization of ultrastructural details and platinum deposits in cells. The underlying physics behind TEM is similar to that of ordinary light microscopy however, the resolutions achieved by TEM can be some 400-fold greater than that of light microscopy (38). Briefly, the mechanics behind TEM involves an illuminating source, the electron gun, that sends a beam of electrons through a vacuum and onto the... 

In the case where there is a loss of activity of the catalyst, however, simply ascertaining evidence of sintering in the metallic phase is often sufficient. The simple fact that particles can be observed by transmission electron microscopy often constitutes a test for tracing the source of a malfunction. For catalysts with lower dispersion levels, a more detailed study can be used to obtain a histogram showing the particle size distribution. 

Source Brearley (1993) and Greshake (1997). Matrix analyzed by electron microprobe amorphous phase by analytical transmission electron microscopy. Totals are normalized tol(X)%. Figures in parentheses are la of means of analyzed regions for matrix and la of analyses for amorphous phase. NA, not analyzed. 

The samples were characterized by means of X-ray diffraction (XRD) analysis, Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), electron diffraction (ED), and Mossbauer spectroscopy. XRD analysis was carried out on a HZG-4A diffractometer by using Ni-filtered Co Ka radiation. IR-spectra were recorded on an AVATAR FTIR-330 spectrometer. TEM/ED examinations were performed with a LEO 906E and a JEOL 4000 EX transmission electron microscopes. The resonance spectra were recorded in air at 298 K and processed by using a commercial SM2201 MSssbauer spectrometer equipped with a 15 mCi Co (Rh) source. 

The size and distribution of pores and the size, distribution, and identity of minerals in coal specimens from an eastern Kentucky splint coal and the Illinois No. 6 coal seam were determined by means of transmission electron microscopy (TEM) and analytical electron microscopy (AEM). The observed porosity varies with the macerals such that the finest pores (<2-5 nm) are located in vitrinite, with a broad range of coarser porosity (40-500 nm) associated with the macerals exinite and inertinite. Elemental analyses, for elements of atomic number 11 or greater, in conjunction with selected area diffraction (SAD) experiments served to identify the source of the titanium observed in the granular material as the mineral rutile. Only sulfur could be de-tected in the other coal macerals. Dark-field microscopy is introduced as a means for determining the domain size of the coal macerals. This method should prove useful in the determination of the molecular structure of coal. 

Rutherford backscattering spectroscopy Scanning electron microscopy Secondary ion mass spectroscopy Single crystal X-ray diffraction Small angle X-ray and neutron scattering Spark source mass spectrometry Transmission electron microscopy Voltametry... 

---