Note: The NanoCenter NispLab will be offering SEM, TEM, and FIB shortcourses from 6/17 through 7/3. Please click here for more information
Thomas C. Isabell, Ph.D.
JEOL USA, Inc
Few electron optical inventions have revolutionized the TEM/STEM as profoundly as the spherical aberration (Cs) corrector. With Cs correctors the sub-Ångstrom imaging barrier has been passed, and fast atomic scale spectroscopy is possible. Because the spherical aberration can be corrected, efforts are now directed towards the reduction of the chromatic aberration. Since the chromatic aberration is proportional to the energy spread of electron source, a low energy spread reduces the probe size of a STEM spherical aberration corrected column. A cold field emission gun (CFEG) is known to create an electron source with low energy spread as well as high brightness. These characteristics give high speed acquisition with high spatial and energy resolution in STEM and EELS.
EDS analysis in the TEM has long been a technique that required great care and great patience. Due to the geometry near the specimen in the TEM, EDS collection efficiency has traditionally been very poor. This means an overall lack of EDS signal; requiring long dwell times to collect meaningful and statistically significant data. A new generation of large solid angle EDS detectors for ultrafast, ultrasensitive collection of X-rays has been developed. Combined with the large probe currents in small probe sizes attainable with aberration corrected cFEG STEM, fast, efficient atomic resolution EDS analysis is possible.
A further benefit to aberration corrected microscopes is that a larger pole piece gap can be used in the TEM, while still achieving sub-Angstrom image resolution. This means that there is more room around the sample for in-situ experimentation. This opens the door to a whole realm of dynamic experiments, done on a spatial scale never before possible.
There are a few ways in which in-situ experiments in the TEM can be carried out. The TEM can be dedicated to in-situ experimentation and modified to include an environmental cell around the specimen. However, this approach can affect the performance of the instrument. Alternatively, specially designed TEM specimen holders can be used in a conventional TEM for in-situ work. A variety of environmental holders have been developed for these kinds of experiments, including: heating, cooling, straining, and indentation holders; probe holders for electrical measurements; holders with an enclosed environmental cell so that the specimen can be examined under different gases and or liquids; and even holders with an integrated SPM tip for simultaneous TEM/SPM observation of the specimen. These holders provide unparalleled flexibility for an aberration corrected microscope, allowing in-situ experiments to be carried out without compromising the overall performance of the TEM.
Mike Hernandez (Sr. Product Specialist)
Hitachi High Technologies America, Inc.
EDS x-ray microanalysis in the SEM is considered a relatively low spatial resolution technique, due to a typically large e-beam interaction volume in the specimen. In order to improve spatial resolution, the interaction volume has to be reduced. This can be achieved by either substantially reducing the beam energy, or by producing very thin specimens. In both cases, x-ray signal generation is greatly reduced. High-sensitivity x-ray detectors greatly increase collection efficiency, but traditional e-beam sources still lack the ability to deliver enough electrons into a small enough spot to make it an efficient process. The latest cold FEG source produces the brightest and most coherent e-beam at all energies, making the dream of high-throughput, high-spatial resolution EDS microanalysis a reality. Here we will describe why this new technology is not only the perfect platform for efficient high resolution EDS, but also the best solution for ultra-high resolution SEM imaging, especially at low and ultra-low beam energies.
Doug Wei, Ph.D.
Carl Zeiss Microscopy
Owing to its extremely small probe size, He ion microscopy has initially been used in imaging to achieve high resolution, high quality images since its introduction to the market by Carl Zeiss in 2006. Further development in instrumentation and applications has made this technology more attractive in nanoscale processing and fabrication, especially in sub-10nm regime where no other ion beam based techniques have ever reached. In this report, an overview of the technology and instrumentation, current applications as well as future development will be presented.
TESCAN-USA, Cranberry Township, PA, USA
The purpose of this talk is to bring to light the many applications and uses for cathodoluminescence on a scanning electron microscope. Examples will be demonstrated for many disciplines, using both monochromatic and and panchromatic imaging.
Bruker XTrace Micro-Spot X-ray source attachment to the SEM provides micro-XRF capability and extends EDS analysis sensitivity by 20 to 50 times over electron excited EDS, for elements above Ca. Micro-XRF, with minimum detection limits in the 100ppm range, is most beneficial for trace element analysis. Polycapillary optics focus the X-ray excitation down to spot sizes as small as 45 µm and so elemental mapping of the sample, via XRF, is also possible.
Using the same XFlash EDS detector, combined electron and X-ray exited EDS spectra can be acquired. Combined quantification of the spectra can be merged for mutual enhancement of quantification reliability for complete characterization of the sample with improved results, particularly for samples with trace elements.
EDAX Global Applications Manager, Mahwah, NJ
In this lecture X-ray excitation in the SEM will be reviewed, providing an understanding of how the inner workings of the modern Silicon Drift Detector (SDD) technologies increase analytical capabilities. The increases gained by the SDD allow more complex data collection routines which drive new applications in microanalysis. Specifically, phase mapping characterizes materials in a more comprehensive manner, revealing elemental distribution and associations that were not previously possible. Examples include phase mapping of ceramic materials, automotive components and low kV analysis of graphene.
EDAX Global Applications Manager, Mahwah, NJ
This 40 minute session will start with a background and introduction to the hardware and geometrical considerations of integrated EDS and EBSD components. Signal collection, image processing and kikuchi band indexing at high speeds will be evaluated to show how high quality data, even at faster collection rates, is now possible. The analysis of large scales ranging from tens of nanometers to millimeters for a wide range of crystalline materials is the result, enabling microstructural understandings complimentary to techniques such as XRD. 3D microanalysis datasets will be explored to conclude this session.
John Damiano, Ph.D., Protochips, Inc.
Over the past several years, the tools and techniques supporting in situ electron microscopy have improved dramatically. Semiconductor-based sample supports are replacing traditional TEM grids to create environments in the EM and apply stimulus to samples. The unique features of these sample supports - as part of a complete in situ system - allow researchers to study and analyze nanoscale samples under reaction conditions without compromising image quality. This presentation will describe new trends that are transforming in situ EM and discuss recent results from the research community.
Sairam K Malladi, Qiang Xu, Frans Tichelaar, Henny Zandbergen
National Centre for HREM, Kavli Institute of Nanoscience Delft, Delft University of Technology, 2628 CJ Delft, The Netherlands
Investigating dynamic changes in specimen while applying a stimulus in a transmission electron microscope (TEM) has always been an exciting field of study. With the advancements in TEMs and microelectromechanical systems (MEMS), the area of in situ TEM has grown in leaps and bounds over the last decade. We have used a functional MEMS based device developed in-house called nanoreactor to carry out in situ TEM studies. The nanoreactor1 consists of two facing silicon chips with thin electron-transparent silicon nitride membranes. One half of the nanoreactor (bottom half) is embedded with a Pt coil for resistive heating. When a specimen is encapsulated in a nanoreactor, it is possible to carry out gas-liquid-material interactions from room temperature to 700 °C with environmental pressures as high as 4.5 bar, while the bottom half alone can be used for in situ heating experiments. Using these devices with specially made TEM holders, we have succeeded in carrying out in situ precipitation studies2 in aluminium alloy (AA2024-T3) on one hand. We observed the nucleation and growth of needle-like S-phase type (AlXCuYMgZ) precipitates while heating these alloy specimens within temperatures of 100 - 250°C. On the other hand, we have also succeeded in carrying out room temperature corrosion studies of AA2024-T3 exposed to oxygen bubbled through aqueous hydrochloric acid of pH = 3 at a pressure of ~ 1.5 bar.3 These sort of experiments are critical to understand the performance of engineering materials in service conditions. With this method, it is possible to correlate the microstructural changes happening during the service of an engineering alloy, due to any processes that can heat the material like welding or higher operating temperatures, with the changes in the environment. Therefore, the TEM no longer serves as a mere characterization tool but also as a laboratory to carry out many interesting in situ experiments.
Joe Klingfus, Andre Linden
Raith America, Inc., 2805 Veterans Highway, Ronkonkoma, NY 11779, USA
Frank Nouvertné, Axel Rudzinski, Torsten Michael, Mark Levermann,
Raith GmbH, Konrad-Adenauer-Allee 8, Dortmund, 44263, Germany
RWTH Aachen, 2. Phys. Inst., Otto-Blumenthal-Str. 28, 52074 Aachen
Well-established, standard electron and ion beam nanolithography instruments are regarded as must-haves in modern research labs to enable state-of-the-art nanofabrication. Nanopatterning processes and corresponding parameters are typically well understood for standard applications such as resist-based electron beam lithography (EBL) or FIB milling processes like circuit editing or TEM lamella preparation. In the recent past however, the bandwidth of nanofabrication applications for dedicated nanopatterning tools has significantly broadened and is not limited to standard resist-based EBL or “standard” FIB milling tasks. Some latest generation professional and multi-purpose electron and ion beam nanolithography tools even facilitate additional in situ processes such as resistless focused electron or ion beam induced processes (like material deposition or gas enhanced etching.) The number of variables for such complex processes involving new gas chemistry or ion species is a nearly infinite parameter space, so that an efficient in situ characterization of material deposition, milling or etching rates becomes crucial for the most effective understanding and subsequent optimization of such processes. Smart patterning strategies (such as using sequences of loops in conjunction with flexible multi-directional patterning modes) can significantly improve the final nanostructure´s definition and performance.
Typical measurement/verification procedures involve using analytical equipment “outside” the system vacuum, and subsequently re-introducing the sample back into the tool for further processing. In contrast to this, we have implemented a distance-sensitive nanomanipulator with nanoprofilometric capabilities. This allows for in situ characterization of nanostructures in 3D with a sharp W-tip (see Figure 1) by collecting topographic sample surface information via line scans well below 20 nm height resolution (see Figure 2 and Figure 3). First results of direct in situ growth rate determination of focused electron beam induced material deposition (FEBID) for process calibration (see Figure 4 to Figure 6) as well as 3D surface topographic information of challenging milling applications will be presented.
JEOL USA Inc.,
Gold/TiO2 films have attracted much attention due to the high catalytic activity, and have recently been characterized using surface enhanced Raman scattering (SERS) technique . Red-shift in the extinction spectrum was observed with the increase of TiO2 film thickness and has ascribed to the increase in effective refractive index of the substrate slab and coupled plasmon resonance. A similar Au/TiO2 structure was hence investigated in confirming the propriety of the SERS analysis and disclosing the point at issue using analytical electron microscopy.
A TiO2 thin film was deposited on an optical microscope glass slide (FEA, ground edges, plain) at 200°C, by 417 cycles of atomic layer deposition (ALD) using alternating pulses of tetrakisdimethylamido titanium and H2O with an Ar carrier gas flow. The deposition rate for TiO2 was 0.045 nm per ALD cycle , and the estimated film thickness was 20 nm using a spectroscopic ellipsometer. An Au layer was then deposited on the surface of TiO2 film by thermal evaporation. The thickness of the Au layer was ~ 3 nm as indicated by a quartz crystal thickness monitor. The specimen was reinforced with carbon and Pt layers, and then thinned by focused ion beam (FIB). Analytical TEM was performed using a JEM-2100F UHR STEM, equipped with an Oxford Instruments 30 mm2 EDS spectrometer, a Gatan Orius model US1000FT CCD camera, and a GIF Tridiem (model) energy filter.
HR-TEM revealed that the 3 nm thick Au film was composed of round particles with diameters of ~15 nm or less . Based on TEM images, the thickness of TiO2 layer was measured to be 11 nm though the expected thickness was 20 nm (as mentioned above). STEM HAADF image, as shown in Figure 1a, depicts each Au79 particle clearly. The Ti22O82 layer (arrow in Fig. 1a) is shown with light (contrast) gray band that is laid in between dark areas of the glass (Si14O82) and bright C6 layers. EFTEM thickness map (Fig. 1b) illustrates t/λ, where λ is the average mean free path of inelastic scattering of electrons and t is the local specimen thickness, which can be evaluated from t =λ log (IT /I0) . I0 is zero-loss intensity, obtained from zero-loss image (0±5 eV) (Fig. 1c), and IT is the total intensity in EELS, obtained from conventional EFTEM image (Fig. 1d). This thin specimen, with t < 0.31λ, warrants the accuracy of the EELS analysis. The EFTEM Ti-L map (Fig. 1e) and EFTEM C-K map (Fig. 1f) indicate the TiO2 layer and the reinforcement of C, respectively. Figure 2 shows EDS analysis of the Au/TiO2 microstructure. HAADF image (Fig. 2a) and Au-L map (Fig. 2b) reveal an Au particle. The Ti-L map (Fig. 2c) indicates the TiO2 layer whereas Si-K map (Fig. 2d) indicates the glass substrate. However, these images exhibit artifact contrasts due to the higher background of X-rays stimulated by strong emissions form Au particle. The Ca-K map (Fig. 2e) illustrates Ca atoms on the common soda lime glass substrate. EELS maps (Fig. 3) do not exhibit any artifact in the gold region. The O-K map (Fig. 3a), O-K map with energy-loss near-edge structure for Ti-O (Fig. 3b) and together with Ti-L map (Fig. 3c) confirmed the existence of TiO2 layer. It is known that the density of amorphous oxide films is ~30 % less than that of the bulk oxide and the amorphous films may contain many voids . As the soda lime glass substrate was heated to 200 oC during ALD, Ca atoms in glass surface have become mobile and readily diffused a few nanometers into the thin amorphous TiO2 film (Fig. 3d). Those voids in the thin amorphous TiO2 layer might have been immediately occupied by diffused Ca atoms while heating the substrate (i.e., before the deposition of Au). Therefore, Au atoms that lately evaporated/deposited on the surface of amorphous Ti(Ca)O2 could easily migrate around and formed a smaller number of Au nuclei. In contrast, the surface of the thicker amorphous TiO2 layer was consisted of pure TiO2 with more voids and thus more Au particles formed than that of a thin amorphous Ti(Ca)O2 layer. The difference in the number of Au nuclei on different TiO2 layers may explain the geometrical differences of Au particles that have reported in ref (1).
The different chemical composition in different thickness of TiO2 layers especially at the surface of substrate, the different growth behavior of Au particles, and electric and optical properties of the deposited films might all have resulted from the diffusion of Ca atoms into TiO2 film at the substrate surface during ALD. Ultra-high resolution analytical microscopy study is, thus, indispensable in the characterization of nanoscale novel materials and devices.
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Fig. 1. EFTEM of Au/TiO2 microstructure. (a) STEM HAADF image. (b) EFTEM thickness map. (c) Zero-loss image (0 ± 5 eV). (d) Conventional EFTEM image (e) EFTEM Ti-L map. (f) EFTEM C-K map.
Fig. 2. EDS mapping of Au/TiO2 structure. (a) HAADF image. (b) Au-L map. (c) Ti-L map. (d) Si- K map. (e) Ca-K map. (f) Composite EDS map (Si: red, Ca: blue, Ti: green and Au: yellow).
Fig. 3. EELS maps of Au/TiO2 structure. (a) O-K map. (b) O-K map with energy-loss near-edge structure for Ti-O. (c) Ti-L map. (d) Ca-L map. (e) C-K map. (f) Composite EELS map (Ca: red, Ti: green and C: blue).
F. A. Stevie(1), L. Sedlacek(2), P. Babor(3) J. Jiruse(2), E. Principe(4), K. Klosova(2)
(1) North Carolina State University, 2410 Campus Shore Drive, Raleigh, NC 27695, USA
(2) TESCAN, Libusina trida, 623 00, Brno, Czech Republic
(3) Central European Institute of Technology, Technicka 3058/10, CZ-616 00, Brno, Czech Republic
(4) TESCAN-USA, Cranberry Township, Pa USA
Development of a SIMS technique with the capability to provide ppm level detection integrated with a FIB-SEM platform has been long sought after goal. Of the possible analyzers, magnetic sectors have had limited application with only two instruments [1-4] and quadrupole analyzers provide a low useful yield by comparison to a ToF analyzer . A Time of Flight SIMS (TOF-SIMS) analyzer developed in cooperation between Tescan-Orsay Holdings and Tofwerk AG as part of the EMPA FIBLYS project provides a new approach to integrated SIMS analysis and extends the analytical capability of FIB-SEM workstations . The combination of this analyzer with a high current plasma ion source offers new analytical opportunities in terms of both volume and application space. Use of a TESCAN FERA platform showed the ability to detect and quantify Li, Na, K and B ion implanted in Si at known concentration. Depth profiles using both Ar and Xe sources of a Si sample ion implanted with Li, Na, and K showed count rates in excess of 1x105 counts/sec and a dynamic range of more than two orders of magnitude for ion implants with peak concentration of 1x1019 atoms/cm3. Using the integrated field emission electron column permitted charge mitigated analysis of 300nm SiO2/Si implanted with BF2. Successful analysis has also been made of a mineral bulk insulator. We will summarize quantitative results obtained using the plasma ion source and TOF-SIMS analyzer on a series of Si samples with known impurity concentrations. Parallel experiments on an LMIG system also confirmed significant secondary ion yield improvement for Ga+ bombardment of Si as measured on 28Si+ and 30Si+ with the addition of O2+ bombardment at 2-5keV.
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