The electron beam broadening in specimens is a important issue to obtain a high spatial resolution expected by using a fine electron probe of nanometer order in analytical electron microscopy. Beam broadening mainly depends on electron diffusion in specimens. The theoretical equation on the beam broadening, which is based on single scattering approximation model for incident electrons, has been proposed by Goldstein et al.. in this work, the beam broadening was estimated experimentally by a TEM equipped with a field emission gun and the results were compared with the values theoretically obtained.

The sizes of the beam diameter with and without specimens were measured by using JEM-2010F and JEM 3000F TEMs, which are equipped with a field emission gun, being operated at 200 and 300 kV, respectively. The beam diameter was defined as the diameter containing 90% of the total electrons. The specimens used were amorphous SiO2, crystalline MgO and Si.

Sm(Co,Cu,Fe,Zr)z 2:17 based permanent magnets have the highest Curie temperature and the most excellent temperature stability among the current rare-earth permanent magnets. in recent years, the Sm(Co,Cu,Fe,Zr)z magnets have attracted again considerable attention due to the demand of the Department of Defense for high temperature applications such as aircraft, spacecraft and ship systems. Our recent studies have led to the development of new precipitation hardened Sm(Co,Fe,Cu,Zr)z magnets with operating temperatures above 400°C and with coercivities as high as 10 kOe at 500°C. The microstructure of the Sm(Co,Cu,Fe,Zr)z high temperature magnets consists of a cellular structure (2:17 rhomobohedral cells surrounded by 1:5 hexagonal cell walls) superimposed on a lamella phase (2:17 hexagonal). This microstructure is sensitive to processing and to the alloy chemical composition. Magnetic domain structure studies play a critical role in understanding the magnetic hardening behavior of the magnets. in this paper, HREM and magnetic domain structure were studied in these Sm(Co,Cu,Fe,Zr) high temperature permanent magnets.

Similar to graphite and carbon fullerenes, the physical properties of carbon nanotubes (NTs) can be altered by ex-situ doping or by functionalizing the nanotube walls. Such mechanisms for tailoring the properties of carbon NTs expand their potential utility in electronic, optical and structural applications. Both acceptor (e.g. I2, Br) and donor-type (e.g. K, Rb) dopants have been successfully intercalated into single-wall NT (SWNT) bundles, and the transport properties of these doped species are greatly altered. For example, iodine-doped SWNTs exhibit a 40% decrease in DC conductivity. Doped SWNTs are a completely new class of nanostructured materials, and there is a large demand for understanding the structure of the various doped-compounds as well as the ramifications for the electronic properties of the material.

In this paper we demonstrate the utility of Z-contrast scanning transmission electron microscopy (STEM) for elucidating the structure of doped nanotubes.

The advancement of metal-oxide-semiconductor (MOS) technology towards sub- 100nm device dimensions presents several technical difficulties. Nanoscaling in MOS devices is specifically governed by difficulties in the formation of ultrashallow junctions for the source/drain regions with the requirement of low resistance and low leakage currents. The use of a silicide (forming Schottky contacts at the source and drain) instead of the conventional ion implanted Si for the contacts allows a reduction in the contact area to be made, due to lower serial resistance per unit area of the silicide. According to the specific contact resistance dependence on the Schottky barrier height (ΦSB) and active dopant concentration (ND),

Current commercial analytical electron microscopes (AEMs) including scanning transmission electron microscopes (STEMs) are a compromise design between the highest spatial, analytical and energy resolutions. in contrast, a VG HB603 STEM at Lehigh University has been designed with a 300 kV cold field-emission gun and twin X-ray detectors to maximize X-ray generation and collection efficiencies [1]. in addition, instrumental features of almost no stray radiation, ultra-high vacuum (<10−7 Pa in the stage and <10−7 Pa in the gun), beam blanking and direct probe-current measurement in the HB 603 have transformed the approaches to quantitative analysis. By using such modern AEMs, it is now possible to perform X-ray microanalysis with the spatial resolution as low as 1.5 nm and the detectability limits of∽2 atoms in the analyzed volume [2]. Furthermore, even quantitative X-ray mapping becomes achievable, while maintaining, high spatial resolution (the original aim of such instruments) [3].

Mixed conductors have been the focus of many studies in the last decade, leading to a detailed understanding of many of the macroscopic bulk properties of these materials. in particular, although the reduced low temperature phase in rare earth perovskite oxides is commonly explained in terms of ordered brownmillerite structured micro domains, its transition to the high temperature phase remains elusive. in this presentation an investigation of (La, Sr)FeO3, prepared under different reducing conditions through correlated atomic resolution annular dark field imaging and electron energy loss spectroscopy will be shown.

We investigate the (La, Sr)FeO3 material by atomic resolution Z-contrast imaging and EELS using a 200 keV STEM/TEM JEOL2010F with a post column GIF. The combination of these techniques allows us to obtain direct images from the atomic structure of the bulk sample and to correlate this with the atomically resolved EELS information. In-situ heating of the material in a heating double tilt holder in the microscope columns allows us to simulate the highly reducing operating conditions for this oxygen conducting membrane material.

It is known that wurtzite III-V nitrides are highly polarized in the c-direction, which is usually the growth direction. This polarization (spontaneous and piezoelectric) in GaN/AlxGa1-xN heterostructure field effect transistors (HFET) results in high carrier concentrations at the interfaces, in addition to the large conduction band offset. This high-density 2D electron gas formed at a GaN/AlxGa1-xN heterointerface in its turn increases the mobility of the heterostructure. Therefore, questions about the measurement of the physical width of a GaN/AlxGa1-xN interface and the calculation of its effects on the physical characteristics of devices naturally arise. Since the electrical field distribution, as well as the location and density of the 2D electron gas, depends on the width of the GaN/AlxGa1-xN heterointerface, accurate determination of the width is critical.

Measurements with high spatial resolution EELS using transmission electron spectroscopy with a ∽2Å focused electron beam permits atomic-level studies of such specimens.

High spatial resolution information on the structure and composition of semiconductor quantum dots is necessary to relate microstructure to macroscopic electron-optical properties [1]. Scanning transmission electron microscopy (STEM) combined with electron energy-loss spectroscopy (EELS) can be used to determine the elemental composition of nanometer-sized particles. Applying these techniques to quantum dots is challenging because the dot nucleates on a very thin wetting layer of similar composition and is embedded in a matrix. Here we present a strategy to extract absolute compositional information on InGaAs dots. The method relies on modeling both the dot shape and the electron probe profile.

Samples were prepared by depositing four monolayers of In0.5Ga0.5As onto a GaAs substrate giving a nominal wetting layer thickness of 1.2 nm [2]. STEM was performed on a Vacuum Generator's HB501 equipped with a GATAN parallel electron energy-loss spectrometer. An ES Vision system was used to acquire spatially resolved electron energy-loss spectra from the wetting layer and the quantum dots.

The study of magnetic thin films by Lorentz microscopy in the transmission electron microscope (TEM) is a well-established technique. However, in many instances, images are recorded with the specimen in its as-grown state or in a single remanent state following application of a magnetic field outside the microscope. Although such images can provide valuable information, they rarely produce insight into the mechanism by which the magnetic material reverses nor do they show the magnetic structures that form during the reversal process. Furthermore, it is not possible to determine, for example, the field range over which a reversal takes place. Given the importance of such elements for magnetic sensing and storage applications, there is considerable incentive to develop techniques which not only yield the magnetisation loop for an individual element but which reveal how the spatial distribution of magnetisation evolves as a function of field.

The study of magnetic materials using electron column instruments has been a fruitful area of research for microscopists/microanalysts for nearly 4 decades. A number of techniques have been developed for both the SEM and TEM which enable visualization of magnetic fields ranging from Fresnel imaging (Fuller and Hale, Silcox), Differential Phase Contrast (Chapman), through to Electron Holography (Tonomura). The latter are generally qualitative, while the former quantitative, albeit at the price of significant complexity. The advent of microprocessor control of modern instruments, CCD detectors, and experimental diligence allows us to revisit and in fact revitalize this area of measurement.

The experimental work reported here is being carried out in the ANL AAEM HB603Z 300 kV FEG instrument. in this instrument, the electron optical column was operated in a zero field mode (figure 1), where the objective lens is turned off and the probe forming lens functions were reallocated to the C1, C2, and C3 lenses.

In this paper, we discuss the advantage of combining STEM imaging with diffraction. in addition, we present a set of accurately calculated convergent beam electron diffraction (CBED) patterns for Si, which highlights the sensitivity of electron diffraction to structure. The calculation takes the full account of crystal bonding by including known experimental structure factors in simulation. Such calculated patterns can be used for accurate determination of the sample thickness, crystal orientation and polarity (for acentric crystals). Calculations with and without crystal bonding show significant difference in calculated intensities, equivalent to a change in thickness about several nanometers for thick samples.

The annual dark field (ADF) imaging mode in scanning transmission electron microscopes offers the unique advantage of combining high-resolution electron imaging and spectroscopy with diffraction. The large cutoff angle used in ADF imaging allows simultaneous recording of diffraction patterns for quantitative structural information, while ADF imaging gives the precise position of the probe and the image of the sample.

Fluctuation microscopy is an electron microscopy technique sensitive to medium-range order (MRO) in disordered materials. It has been applied to study amorphous germanium and silicon, leading to the conclusion that these materials exhibit more MRO than the conventional continuous random network model for their structure.

As originally proposed by Treacy and Gibson, fluctuation microscopy utilizes mesoscopicresolution (1.5 nm) hollow-cone dark field (HCDF) imaging in a TEM. The normalized variance of such images,

is a measure of the magnitude of fluctuations in the diffracted intensity from mesoscopic volumes of the sample and is sensitive to MRO via the three- and four-body atom distribution functions. Studying V as a function of the diffraction vector magnitude k gives information about the degree of MRO and the internal structure of ordered regions. V as a function of the inverse resolution Q gives information about the characteristic MRO length scale.

We developed a high energy-resolution electron energy-loss spectroscopy (EELS) microscope to investigate electronic structures from specified small specimen areas [1]. EELS gives us information of the dielectric properties and the partial density of states (DOS) of the conduction band. Together with the DOS of the conduction band (unoccupied states), the DOS of the valence band (occupied states) is imperative to understand the whole electronic structure. Unfortunately, the DOS of the valence band cannot be reached directly by EELS.

A partial DOS of the valence band can be obtained by fluorescent X-ray emission spectroscopy (XES). A conventional EELS instrument attached to a TEM usually takes spectra with an energy resolution of about 1 eV, by which the DOS of conduction bands has been studied using ELNES until now. Thus, an energy resolution of about 1 eV is at least necessary for the study of the DOS of the valence band.

Three-dimensional (3D) observation is one of the important trials of future TEM and STEM methods. in the field of biological science, 3D-observation has already become general because the biological materials are usually amorphous and computed tomography (CT) routines can be effectively used. The CT assumes that the image intensity is linearly proportional to the projection of material density. in a crystalline specimen, however, this linearity does not hold due to the dynamical diffraction effect depending on spepimen thickness and incident directions of electron beam. High-angle annular-darkfield STEM (HAADF-STEM) and EDX mapping images could meet this requirement of the linearity because their image intensity are little affected by the dynamical diffraction effect.

Our 3D-STEM is based on a 300 kV FE-TEM/STEM(Hitachi HF-3000) equipped with a specially designed eucentric specimen stage with double spherical fulcra, a newly developed dark/bright field STEM detectors, a 3D-sampling system and a 3D-imaging processor for 3D topography and tomography.

In many new application areas it is necessary to combine atomic resolution imaging with atomic level chemical and crystallographic analysis. The new applications include microbiology, nanotubes, smart materials and sensor initiatives, and the myriad semiconductor fields. Along with these there are many other valuable applications in older and more established technologies such as chemicals, catalysis, pigments and construction materials for chemical plants, airplanes, pipelines, power generation, and other aspects of societal infrastructure. Analysis down to the atomic level will help to solve recalcitrant problems and open up some reluctant opportunities in these fields. They can be very effective in resolving important and long standing issues with huge potential monetary and societal costs and benefits. Key aspects of environmentally sensitive corrosion and pollution control may also require the support of similarly sophisticated imaging and microanalysis.

We think the capabilities of a new generation high performance instrument should include atomic resolution coherent TEM imaging and also incoherent atomic number (Z) contrast high angle annular dark field (HAADF) STEM imaging.

The IBM high resolution STEM project has now reached the point where integration of new subsystems into the instrument is the main activity. During the past three years, we have demonstrated a 50meV EELS resolution using a high brightness electron monochromator incorporated into the electron gun [1, 2, 3], and better than 0.14mn spatial resolution using spherical aberration correction at 120KeV. [4] Recent effort has been to identify and remove many sources of instabilities in the original instrument; to rebuild several existing subsidiary pieces of equipment such as the ADF detector, the EELS spectrometer electron optical coupling, and the EELS CCD detection system; and to set up software and hardware control of each system to allow routine operation.

The new STEM column is summarized in Fig. 1. Briefly, the original VG gun flange has been lowered about 4cm, using a spacer, to allow insertion of the Fringe Field monochromator.

Internal boundaries in crystalline microstructures, like polycrystals, thin-film or multi-layer composites, essentially control many important material properties and physical phenomena, such as mechanical deformation and fracture, transport processes or phase transformations. This influence is originating from the local atomistic and electronic structures at the boundaries. Hence, for a. science-based technological design and optimisation of structural and functional materials it is of paramount importance to characterize and understand the structure, chemistry and bonding at interfaces.

Transmission electron microscopy (TEM) has matured to one of the most successful experimental approaches for the analysis of extended structural defects like dislocations and interfaces. This presentation discusses scientific and technological ingredients of TEM for quantitative characterisations on the microscopic level. For selected model cases of internal interfaces it illustrates recent achievements of both experiment and theory. A variety of interface properties and corresponding TEM techniques for their characterisation are summarized in TABLE 1.

Moiré patterns are commonly formed in multiphase system when diffracting planes of similar spacing and orientation lead to interference effects. They can be used experimentally to evaluate the stress distribution in materials [1], to analyze orientation relationships and latttice strain in diffraction contrast microscopy, or, combined with the related geometrical phase technique, to analyze displacements in high resolution lattice images [2,3]. The interpretation of moiré fringes is often not straightforward due to the elastic interaction between the crystals at the interface and the dynamical nature of electron diffraction [4]. However, if the two lattices are fully relaxed, or if a small precipitate crystal is embedded in a large matrix, moiré patterns can give a simple and direct measure of orientation and lattice constants. in the present work, the moiré technique has been applied to the quantitative analysis of lath-shaped Ge or Ge-Si precipitates in Al with the aim to determine the composition (the Si:Ge ratio) from the lattice parameter indicated by the moiré fringes.

The development of ‘quantitative’ high-resolution transmission electron microscopy (QHRTEM) has led to considerable progress in analyzing and understanding the atomistic structure of grain boundaries and heterointerfaces, which often control relevant macroscopic properties of materials. The following results of recent experimental studies and the comparison of these results with atomistic modeling demonstrate the strength of QHRTEM:

1.Grain Boundaries in SrTiO3. Some technical applications of SrTiO3 ceramics rely on special electric properties of this material, which originate from segregation of electrically active point defects to grain boundaries. QHRTEM can substantially contribute to understanding the correlation between the atomistic structure of grain boundaries and the segregation of point defects to these interfaces. As an example for a grain boundary structure solved by QHRTEM, FIGs. la and b present an experimental HRTEM image of the Σ= 3, (111) grain boundary in SrTiO3 and the corresponding atomistic structure as obtained by QHRTEM.

Oxides, nitrides, carbides and silicides contain more than one type of atoms that gives one extra degree of freedom in the grain boundary and interfacial structure. This degree of freedom is the choice of the boundary plane containing different type of atoms which results of several structural multiplicities in the boundary. Coexistence of the structural multiplicities (or boundary domains) in the interface and grain boundary were reported [1, 2]. The structural information in high frequency domain is usually blurred and lost in the lens system of a high resolution transmission electron microscopes (HRTEM) such that the HRTEM image may not truly represent the real structure. Conventionally, the structures of grain boundary and interface were solved using forward method. The forward method involves matching the simulated images from guessed possible models with the through focal series experimental images. Recently, rereconstruction methods such as focal variation holography [3, 4], tiltbeam holography [5] and Gerchberg-Saxton algorithm [6] provide a backward (direct) way to recover the structural information lost in a modern microscope.