We have determined the long-range order parameter of individual [001] oriented FePt L1 0 nanoparticles. Measurement of convergent beam electron diffraction intensities of single particles in scanning transmission electron microscopy (STEM) mode, and comparison of the measured intensities to multislice simulations of diffracted beam intensities allow determination of the order parameter of the particle.FePt films were prepared by co-sputtering high purity Fe and Pt targets onto SiO2/Si substrates using ultra high vacuum dc magnetron sputtering. Ex-situ anneals between 500°C and 800°C in one atmosphere of a flowing reducing gas, argon with 3% hydrogen, were used to stabilize the isolated cluster morphology and to induce ordering. The composition of the Fe-Pt deposit was measured by Rutherford backscattering spectrometry (RBS) and determined to be 50 ±0.5 atomic % Fe.The CBED patterns were simulated with a multislice approach [1] for [001] oriented particles under conditions matching the experiment. The multislice approach specifically includes important dynamical scattering effects. Thermal effects were included using the frozen phonon method with root-mean-square deviations from the atomic positions of 0.007 nm for Fe and 0.0063 nm for Pt (estimated from the international table for X-ray crystallography [2]). The order parameter is included by statistically weighting each site in the structure with the correct fraction of the atomic species found on those sites. An example simulated CBED pattern is shown in Fig 2. In Fig. 3 we show the simulated I 110 /I 220 intensity ratio as a function of changing order parameter (S) for several thicknesses close to the observed particle thickness. Also in Fig 3 are two examples of experimental intensity ratios and the corresponding range of order parameter.Single particle diffraction data was acquired in the STEM mode of the TEM. A convergent beam of 4 mrad convergence semi-angle was focused on the specimen, and CBED patterns were collected from the ordered particles. The 4 mrad angle was chosen to give minimal overlap between the diffracted disks. Fig 4 shows an [001] oriented particle CBED pattern after subtraction of an offparticle background pattern.Dynamical scattering effects are seen in the oscillatory nature and flattening of the curves in Fig 3. This introduces uncertainties in the measurements of order parameter. With those uncertainties taken into account, the order parameter for the two cases shown is determined to be S = 0.4±0.1 and S=0.62±0.24 [3].References

Most of us heard the story of the blind men and the elephant as children. In this old tale from India each man in a group of blind men touches a different part of an elephant. Each walks away with a different experience and subsequently argues that the elephant is like a spear (the tusk), a thick rope (the trunk), a wall (the flank), etc. Only the combination of their stories would have provided a complete, or at least more complete, picture of what an elephant really is. In some sense this is the story of surface analysis, which lacks a single analytical tool that can provide comprehensive information about a surface or interface. We rely on X-ray photoelectron spectroscopy (XPS) for surface elemental analysis and oxidation state information, spectroscopic ellipsometry for film thicknesses and optical constants, contact angle measurements to understand surface wetting, Fourier transfer infrared spectroscopy (FTIR) to reveal functional group information, negative and positive ion time-of-flight secondary ion mass spectrometry (ToF-SIMS)to provide molecular fragments and trace element detection, Rutherford backscattering (RBS) for elemental composition and atom distributions in moderately thick films (typically at least a few nanometers), nuclear reaction analysis (NRA) for absolute quantitation of atomic compositions of thin films, atomic force microscopy (AFM) for surface roughness, scanning electron microscopy (SEM) to reveal surface features and patterning, BET (Brunauer, Emmett, Teller) isotherm measurements to provide surface areas and pore sizes, etc. Combining such information typically provides the most complete view of a surface or interface. The purpose of my talk is to discuss a problem that illustrates the importance of using multiple analytical methods to better understand surfaces and interfaces -an important conclusion of my talk is that no single instrument could have provided the insight into the problem that was gained from the combination of techniques. In particular, we are currently developing and/or modifying highly stable materials based on diamond, zirconia, and/or graphite, which can withstand extreme pH values, temperatures, and/or other harsh chemical conditions, as stationary phases or supports for liquid chromatography.1-3At present this is an important topic in separations science -about 410

In 1995 Peter Rez et al. discussed the Radiolytic transformation of TiO 2 to TiO under high flux electron irradiation (~10 8 A/m 2 ) as observed from the fine structure changes in Electron Energy Loss Spectra (EELS) [1]. We would like to revisit this topic with the specific focus of High resolution EELS of this transformation and general cautionary commentary on STEM work in nanostructures. If the beam is rapidly scanned over a region such as a line or square (as indicated in Fig 1), the observed spectra (Fig 2) is typical of anatase TiO 2 with the B peak split into B 1 and B 2 and B 1 showing up stronger than B 2 [2]. In Fig 2, this is only seen as the peak at the B 1 position and an asymmetry in the B peak. However, when the beam is stopped at the center of the circle shown in Fig 1, the spectra shifts to lower energy onset and loses the clear A -B set of peaks. This new fine structure appears to be two peaks separated by less than 1 eV. Peak labeling follows the A, B pattern of reference 2.Both spectra shown in Fig 2 were taken at 6 seconds of integration time. However, the electrons involved in the "area" spectra are spread over a region greater than 100 times as large as the spot spectra with an expected corresponding greater than 100 fold decrease in the damage rate. However, in the case of the stopped beam, the damage rate is significantly faster than that seen by Rez [1]. This difference in damage rate could be attributed to difference in electron dose. However, similar data from single crystal anatase particles of similar overall size (~70-100 nm) show no damage on the six second time scale. This indicates a significant enhancement of the damage rate due to the small size and resulting large surface of the fundamental constituent particles.This underscores and illustrates that we must be careful to both minimize and understand the role of beam damage when using the extremely high electron density probes seen in STEM work [3].

Extended abstract of a paper presented at Microscopy and Microanalysis 2010 in Portland, Oregon, USA, August 1 – August 5, 2010.

The environment in which a TEM is installed is critical to the performance of the instrument. Among many concerns is the interference that can be caused by existing mechanical or acoustical vibrations, electro-magnetic interference (EMI) and thermal fluctuations [1]. Studies have shown various techniques that can be employed to reduce or eliminate the external interference [2]. In 2003 Brigham Young University completed the construction of a TEM facility. The installation of the microscopes (FEI, models Tecnai F30 & Tecnai F20 EFTEM) was completed in July of 2004. The facility was designed to meet or exceed the specifications from the microscope and other equipment manufacturers. This work will report on the design and construction of the facility and include a discussion of the measured effectiveness of both the well-known and the not-so-well-known procedures for eliminating the ambient disturbances.Prior to the initial design, the specifications from the equipment manufacturers were reviewed. The methods for measuring mechanical vibrations differ for different manufacturers. As an example, FEI Company takes RMS, third-octave acceleration measurements of the vibration over a particular bandwidth for three perpendicular axes; two parallel (X and Y) and one perpendicular (Z) to the floor. The threshold of vibration acceleration for the X axis is shown in figure 1 by the dotted line. For acoustical vibrations the ambient noise must be less than 70 dB for the entire spectrum and less than 55 dB per individual third-octave band between 10 and 10000 Hz, indicated by the dotted line in figure 2[3]. EMI requirements, given by Gatan Inc. for their GIF Tridiem ER (865), specified that the line frequency must be less than 1 mG with all other frequencies less than 0.1 mG [4]. The thermal fluctuations of the GIF were loosely required to be less than ±0.1˚ C per 1 hr.A few of the design elements used to reduce ambient interference are summarized here. The TEM rooms were built on a separate foundation and a physical gap, with no rigid connections, was maintained between the walls separating the TEM rooms from the main building. This was done to insulate the TEM rooms from vibrations generated in the main building. Custom magnetic field shielding was installed in both rooms to reduce any existing and future increases in AC magnetic field levels. The walls were then paneled with standard acoustic absorptions panels with coated fabric for particulate reduction. The instruments physically sit on a concrete block that is 3 ft thick and physically isolated from the floor of the microscope room. Water-cooled ceiling tiles were installed to minimize the amount of forced air needed to maintain thermal stability of the room. Greater details of all the design components are to be presented.Measurements of the ambient conditions of the TEM rooms have been taken at various stages of the construction as well as after completion and installation. All of the data reported here, except the temperature measurements, were acquired from one of t...