The Magellan is down because of an issue with the aperture homing mechanism. FEI has been contacted and the service engineer is expected to troubleshoot the issue on the 11th or 12th.
Magellan Down on 12/10/14 and up on 12/19/2014
//Month: December 2014
//The UltimaIII company maintenance Dec 1-3
//A Rigaku Tech visited LEXI for the UltimaIII maintenance .
Dec. 1 2014:
i) Original optical configuration: BB/Dtex.
ii)The optics was switched to BB/SC; reference Si samples was tested. It was found that the attenuator was not installed and receiving slit box was not installed at right position.
iii) The optics was set as PB/SC; CBO peak position was checked. After 2 months operation, the peak position was found to be shifted ~12% (one month 9%).
iv) PB optical alignment could not be performed smoothly. The PB alignment failed twice for unknown reasons.
vi) All test results and alignment results were sent to TX for review. Waiting for feedback….
Dec. 2 2014:
i). The tech got more experience with the UltimaIII. Finally BB optical alignment was completed without difficulties.
ii) PB optical alignment could be performed without difficulties. The less absorbers were used for optical alignment. It was believed that the counting loss calibration could be better in this way. Tests with regular PB and BB optics looked like normal.
iii). PB thin film stage alignment was performed but failed with an error message saying the attenuator can’t be switched to “0” position “.
Test results were sent to TX Woodland for further review and feedback…..
Dec. 3 2014
The thin film stage alignment still can not be performed successfully with unknown reasons.
More diagnosis and trouble-shooting is required…
CHEMS seminar on HAADF-STEM tomography of Au particles on silica supports
//Date/Time: Monday, Dec 8, 11:00 am – 12:00 pm
Venue: ET 331
Presenter: Dr. Paromita Kundu
From External Morphology to Atomic Structure under the Electron Microscope
Paromita Kundua,b,c, Stuart Turnera, Hamed Heidaria, Sandra Van Aerta, Sara Balsa, N. Ravishankarb and Gustaaf Van Tendelooa
a Electron Microscopy for Materials Science (EMAT), University of Antwerp, Groenenborgerlaan 171, 2020 Antwerp, Belgium
b Materials Research Center, Indian Institute of Science, Bangalore 560012, India
c Institute of Bioelectronics (PGI-8), Forschungszentrum Jülich, D – 52425 Jülich, Germany
E-mail: paro.124@gmail.com
Abstract: Analysing the external shape and internal arrangement of a nanostructured material can lead us to understand its behaviour and tune its properties. Advanced electron microscopy emerged as a powerful technique to quantify these aspects of a nanostructure.
HRTEM combined with image simulation and exit wave reconstruction can provide information on the local atomic structure, however, with aberration corrected microscopes and advanced analytical methods one can analyse the structure with picometer precision. This method is limited to atomically thin samples. Besides, electron tomography provides a way to reconstruct the 3D volume of the specimen from a series of 2D projection images. In case of nanoscale heterostructures electron tomography is a promising technique to understand the ordering of the heterounits whether the mixing is at atomic level or at the nanoscale. It allows us to visualize the external morphology as well as derive the real atomic constitution of the nanostructure in 3D using (HR)STEM images taken at a series of tilt angles and from different zone axes, respectively. Here we demonstrate the case of nanoscale heterostructures and 1D metal wires where HAADF-STEM tomography and aberration corrected high resolution microscopy are used to understand the structure and morphology. We investigated ultrathin gold nanowires to deduce its atomic structure using low dose microscopy and recorded beam induced structural changes at the atomic scale using aberration corrected HRTEM. This shows a relaxed structure extending towards the surface meaning a relatively large strain in the outermost layer of atoms indicating its potential for an efficient catalytic material. At higher dose we observe the dynamics of the atomic columns leading to the breaking of the wires. Other than the atomic structures, in nanohybrids the external combination of the building units is important to characterise as this influences its properties. HAADF-STEM electron tomography on Au-SiO2 spheres will also be demonstrated. The material is a potential catalyst and the distribution of Au on silica will certainly influence its activity. A 3D reconstruction from a series of HAADF-STEM images renders the volume which shows that the Au is embedded in the outermost layer of the silica spheres. Tomography performed on the intermediate structures formed in the reaction medium reveals that initially a 3D self assembly of Au particles forms, which in the presence of silica precursors results in such spherical morphology. The thermal stability of the structures are investigated and tomography reveals a good stability of the structure, however, at high temperatures the Au particles migrate inside the matrix although the external shape of silica remains intact. Some of these results will be discussed in the presentation.